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Listado de Artículos Publicados 2012

Los artículos están ordenados por el factor de impacto reflejado en el 'Journal Citation Reports 2011'.
  1. Preparation of inorganic nanoparticles in oil-in-water microemulsions: a soft and versatile approach
    Margarita Sánchez Domínguez, Kelly Pemartin and Magali Boutonnet.
    Current Opinion in Colloid and Interface Science 17 (2012) 297–305 F. I. 8.01
    In this review, the synthesis of inorganic nanoparticles using oil-in-water (O/W) microemulsions as confined reaction media is discussed. Synthesis using (O/W) microemulsions has been demonstrated for a great variety of inorganic nanoparticles: metallic (Pt, Pd, Rh, Ag), single metal oxides (CeO2, ZrO2, TiO2, Fe2O3), mixed and doped metal oxides (Ce0.5Zr0.5O2, Ce0.99Eu0.01O2, Zr0.99Eu0.01O2, and Fe2Mn0.5Zn0.5O4), semiconductors (PbS, CdS, Ag2S, ZnS, CdSe, PbSe, Ag2Se), fluorides (CaF2, YF3, NdF3, PrF3), phosphates (CePO4, HoPO4), and chromates (BaCrO4 and PbCrO4). There are two synthetic strategies: 1) the use of oil-in water (O/W) microemulsions, in which the precursor is an ionic salt which is dissolved in the continuous aqueous phase; and 2) use of O/W microemulsions, in which the precursor is an organometallic salt dissolved in the oil droplets of the microemulsion. The latter approach keeps more resemblance to the typical W/O microemulsion reaction method, as it has the greatest level of precursor confinement.
  2. Antibacterial activity, inflammatory response, coagulation and citotoxicity effects of silver nanoparticles.
    F. Martínez Gutiérrez, E. P.Thi, J. M. Silverman, C. Camargo, S. L. Svensson, A. Vanden Hoek, E. Morales, N. E. Reiner, E. C. Gaynor, E. L. G. Pryzdal, E. M. Conway, E. Orrantia, F. Ruiz, Y. Av Gay, & H. Bach..
    Nanomedicine: Nanotechnology, Biology, and Medicine. 8 (2012) 328-336 F. I. 6.692
    The incorporation of nanoparticles (NPs) in industrial and biomedical applications has increased significantly in recent years, yet their hazardous and toxic effects have not been studied extensively. Here, we studied the effects of 24 nm silver NPs (AgNPs) on a panel of bacteria isolated from medical devices used in a hospital intensive care unit. The cytotoxic effects were evaluated in macrophages and the expression of the inflammatory cytokines IL-6, IL-10 and TNF-alpha were quantified. The effects of NPs on coagulation were tested in vitro in plasma-based assays. We demonstrated that 24 nm AgNPs were effective in suppressing the growth of clinically relevant bacteria with moderate to high levels of antibiotic resistance. The NPs had a moderate inhibitory effect when coagulation was initiated through the intrinsic pathway. However, these NPs are cytotoxic to macrophages and are able to elicit an inflammatory response. Thus, beneficial and potential harmful effects of 24 nm AgNPs on biomedical devices must be weighed in further studies in vivo.
  3. Cytotocicity of functionalized carbon nanotubes in J774 macrophages.
    Silvia Lorena Montes Fonseca, Erasmo Orrantia Borunda, Alfredo Aguilar Elguézabal, Luna Velasco Antonia, Carmen González Horta, Patricia Talamás Rohana, Blanca Sánchez Ramírez.
    New Biotechnology 29 (2012) 203 F. I. 6.692
    The cytotoxicity of the carbon nanotubes (CNTs) is an important factor for the manufacture of nanovaccines. The aim of this work was to evaluate the relationship of the purification method of CNTs in cellular toxicity using macrophages (MOs) from the J774 cell line. Viability test was performed with MTT assays at 24 h of exposure at concentrations of 0.06, 0.6, and 6 mg/L of unpurified (UP-CNTs) or purified (P-CNTs) CNTs by two different methods: (1) reflux with 3M HNO3 and (2) sonication in H2SO4/HNO3. Characterization and COOH content of CNTs was performed using scanning electron microscopy, raman spectroscopy, and titration with NaHCO3. P-CNTs1 had lengths >100 μm and 2.76% COOH content, while P-CNTs2 had lengths >1 μm and 7% COOH content. This last particle showed a lower toxic effect. The results suggest that the lenght and COOH content are important factors in the toxicity of the CNTs.
  4. Optical properties, morphology and elemental composition of atmospheric particles at T1 supersite on MILAGRO campaign
    G. Carabali, R. Mamani-Paco, T. Castro, O. Peralta, E. Herrera, and B. Trujillo.
    Atmospheric Chemistry and Physics 12 (2012) 2747-2755 F. I. 5.52
    Atmospheric particles were sampled at T1 supersite during MILAGRO campaign, in March 2006. T1 was located at the north of Mexico City (MC). Aerosol sampling was done by placing copper grids for Transmission Electron Microscope (TEM) on the last five of an 8-stage MOUDI cascade impactor. Samples were obtained at different periods to observe possible variations on morphology. Absorption and scattering coefficients, as well as particle concentrations (0.01–3 μm aerodynamic diameter) were measured simultaneously using a PSAP absorption photometer, a portable integrating nephelometer, and a CPC particle counter. Particle images were acquired at different magnifications using a CM 200 Phillips TEM-EDAX system, and then calculated the border-based fractal dimension. Also, Energy Dispersive X-Ray Spectroscopy (EDS) was used to determine the elemental composition of particles. The morphology of atmospheric particles for two aerodynamic diameters (0.18 and 1.8 μm) was compared using border-based fractal dimension to relate it to the other particle properties, because T1-generated particles have optical, morphological and chemical properties different from those transported by the MC plume. Particles sampled under MC pollution influence showed not much variability, suggesting that more spherical particles (border-based fractal dimension close to 1.0) are more common in larger sizes (d50 = 1.8 μm), which may be attributed to aerosol aging and secondary aerosol formation. Between 06:00 and 09:00 a.m., smaller particles (d50 = 0.18 μm) had more irregular shapes resulting in higher border-based fractal dimensions (1.2–1.3) for samples with more local influence. EDS analysis in d50 = 0.18 μm particles showed high contents of carbonaceous material, Si, Fe, K, and Co. Perhaps, this indicates an impact from industrial and vehicle emissions on atmospheric particles at T1.
  5. Hard and tough carbon nanotube-reinforced zirconia-toughened alumina composites prepared by spark plasma sintering
    Echeberria, J; Rodríguez, N; Vleugels, J; Vanmeensel, K; Reyes Rojas, A ; García Reyes, A ; Domínguez Ríos, C; Aguilar Elguezabal, A; Bocanegra Bernal, MH..
    Carbon 50 (2012) 706-717 F. I. 5.378
    It is demonstrated that 0.1 wt% of multi-walled carbon nanotubes (MWCNTs) or single-walled carbon nanotubes (SWCNTs) added to zirconia toughened alumina (ZTA) composites is enough to obtain high hardness and fracture toughness at indentation loads of 1, 5, and 10 kg. ZTA composites with 0.01 and 0.1 wt% of MWCNTs or SWCNTs were densified by spark plasma sintering (SPS) at 1520 degrees C resulting in a higher hardness and comparable fracture toughness to the ZTA matrix material. The observed toughening mechanisms include crack deflection, pullout of CNTs as well as bridged cracks leading to improved fracture toughness without evidence of transformation toughening of the ZrO(2) phase. Scanning electron microscopy showed that MWCNTs rupture by a sword-in-sheath mechanism in the tensile direction contributing to an additional increase in fracture toughness.
  6. Synthesis of sulfonated graphene/polyaniline composites with improved electro activity
    Elcin Coskun, Erasto A. Zaragoza Contreras, Horacio J. Salavagione..
    Carbon 50 (2012) 2235–2243 F. I. 5.378
    The sulfonation of graphene by coupling with the diazonium salts of sulfanilic (SA) acid and amino-4-hydroxy-2-naphthalenesulfonic (NSA) acid is studied. Coupling with the diazonium salt of NSA gives the highest degree of sulfonation. Composites of polyaniline (PANI) and sulfonated graphene (SG) are prepared by the polymerization of aniline in the presence of the SG. The materials have been characterized by Raman, Fourier transformed infrared spectroscopy, thermogravimetric analysis and cyclic voltammetry. These materials are electrochemically active at pHs close to physiological pH due to the doping of PANI with the sulfonic groups in SG trapped in the polymer. Furthermore, good conductivity values are obtained.
  7. Evaluation of bimetallic catalyst PtAg/C as a glucose-tolerant oxygen reduction cathode
    Guerra-Balcázar, M (Guerra-Balcázar, M.)1; Cuevas-Muñiz, FM (Cuevas-Muñiz, F. M.)2; Álvarez-Contreras, L (Álvarez-Contreras, L.)3; Arriaga, LG (Arriaga, L. G.)1; Ledesma-García, J (Ledesma-García, J.)2.
    Journal of Power Sources 197 (2012) 121-124 F. I. 4.951
    PtAg/C nanoparticles were synthesized by chemical reduction and evaluated for the oxygen reduction reaction (ORR) in the absence and presence of glucose. PtAg/C catalyst formed onion-like layered structures, which are uniformly distributed on the support. PtAg/C showed activity comparable to that of Pt/C ETEK for ORR. Further, the catalyst exhibited high selectivity for ORR in the presence of glucose. PtAg/C was evaluated as cathode in a microfluidic fuel cell operated with high concentration of glucose (100 mM) as fuel. The results demonstrated that the use of PtAg/C as cathode electrode achieved higher selectivity and better performance compared with Pt/C catalyst.
  8. In situ Raman and Time-Resolved Luminescence Investigation of Local Structure of ZrO2 in the Amorphous to Crystalline Phase Transition
    Carmen Tiseanu, Vasile I. Parvulescu, Bogdan Cojocaru, Kelly Pemartin, Margarita Sánchez Domínguez and Magali Boutonnet.
    Journal of Physical Chemistry C 116 (2012) 16776-16783 F. I. 4.805
    The local structure of europium doped and impregnated ZrO2 in the amorphous state and during crystallization is investigated by in situ X-ray diffraction and in situ Raman, high- resolution transmission electron microscopy (HRTEM) and time-resolved photoluminescence spectroscopy. From Raman spectra excited at three different wavelengths (λex= 488, 514 and 633 nm), both phonons modes and photoluminescence (PL) corresponding to europium electronic transitions were investigated. In the as-synthetized state, samples were X-ray and Raman amorphous with few tetragonal (also monoclinic) crystallites being observed under HRTEM microscopy. In situ XRD patterns show that all samples crystallize in the tetragonal phase around 450 °C. The time-resolved PL spectra of europium doped and impregnated ZrO2 show spectral dynamics with time delay after lamp/laser pulse which is assigned to the co-existence of the different amorphous and crystalline components or unreacted europium precursor. From in situ Raman spectra, crystallization was detected at ~300- 350 °C, monitoring for the characteristic tetragonal like 5D0- 7F2 emission of europium at 606 nm. The ratio of tetragonal to amorphous emission increased abruptly from ca. 2- 4 % at 300- 400 °C to almost 25 % at 400- 450 °C whereas at 500 oC the emission is mostly tetragonal. Similar trend was found with the ex situ calcined samples, but relative strong tetragonal emission was observed at lower temperature in the range of 350 to 400 °C. Keywords: europium, tetragonal phase, temperature, XRD, phonons, microemulsion
  9. Photoelectrochromic performance of tungsten oxide based devices with PEG-titanium complex as solvent-free electrolytes
    Hechavarria, L; Mendoza, N ; Rincón, ME; Campos, J ; Hu, H..
    Solar Energy Materials and Solar Cells 100 (2012) 27-32 F. I. 4.542
    Photoelectrochromic (PEC) devices were assembled with an electrochemically deposited tungsten oxide (WO3) thin film on transparent conductive glass (ITO) substrates, a composite polymeric electrolyte (PE), and a Ruthenium 535 sensitized TiO2 sol-gel film deposited on ITO substrates. The polymeric electrolyte was prepared by the sol-gel method using a viscous polyethylene glycol (PEG, MW 600) and titanium isopropoxide as precursors in an acidic medium. A lithium salt (LiI) was added to the PEG-Ti complex for photoelectrochemical purposes. The color change of WO3 based PEC devices under 100 mW/cm(2) illumination at short circuit conditions indicates that the introduction of titanium complex inside the polymeric electrolyte accelerates the coloring speed from 26 to 9 s. Electrochemical impedance spectroscopy analyses of PEC devices show that the presence of titanium complex in PE reduces the charge transfer resistance and increases the charge storage capacity of the cells. This improvement could come from the oxidation of iodides and reduction of titanium ions inside the composite electrolytes that increase the lithium ion's mobility
  10. Comparison and functionalization study of microemulsion prepared magnetic iron oxide nanoparticles
    Chuka Okoli,Margarita Sanchez-Dominguez, Magali Boutonnet, Sven Järås, Concepción Civera, Conxita Solans, Gunaratna Rajarao Kuttuva.
    Langmuir 28 (2012) 8479-8485 F. I. 4.186
    Magnetic iron oxide nanoparticles (MION) for protein binding and separation were obtained from water-in-oil (w/o) and oil-in-water (o/w) microemulsions. Characterization of the prepared nanoparticles have been performed by TEM, XRD, SQUID magnetometry, and BET. Microemulsion-prepared magnetic iron oxide nanoparticles (ME-MION) with sizes ranging from 2 to 10 nm were obtained. Study on the magnetic properties at 300 K shows a large increase of the magnetization 35 emu/g for w/o-ME-MION with superparamagnetic behavior and nanoscale dimensions in comparison with o/w-ME-MION (10 emu/g) due to larger particle size and anisotropic property. Moringa oleifera coagulation protein (MOCP) bound w/o- and o/w-ME-MION showed an enhanced performance in terms of coagulation activity. A significant interaction between the magnetic nanoparticles and the protein can be described by changes in fluorescence emission spectra. Adsorbed protein from MOCP is still retaining its functionality even after binding to the nanoparticles, thus implying the extension of this technique for various applications.
  11. The synthesis of Ni-activated carbon nanocomposites via electroless deposition without a surface pretreatment as potential hydrogen storage materials
    M.Z. Figueroa-Torres, C. Dominguéz-Ríos, J.G. Cabañas-Moreno, O. Vega-Becerra, A. Aguilar-Elguézabal..
    International Journal of Hydrogen Energy. 37 (2012) 10743–10749 F. I. 4.054
    This work presents the deposition of Ni nanoparticles on a potassium hydroxide (KOH) activated carbon (AC) support by an electroless deposition (ED) technique without using sensitization and activation surface pretreatments. The hydrogen storage properties of Ni-activated carbon nanocomposites (Ni/AC) were investigated at room temperature and under moderate pressure. The chemical composition, morphology and textural parameters are characterized using an inductively coupled plasma spectrometer (ICP), scanning and transmission electron microscopy (SEM and TEM) and N2 adsorption isotherms. Fine and well-dispersed Ni nanoparticles were obtained by ED that had spherical shape with an average size of 5 nm. The hydrogen storage capacity of the AC can be improved through Ni loading; which results in a hydrogen storage enhancement factor of two compared with the Ni-free AC. This enhancement factor is due to the greater interactions between the Ni and the AC, which facilitate the hydrogen spillover mechanism.
  12. Synthesis and characterization of PbSe nanoparticles obtained by colloidal route using extran as surfactant at low temperature
    R Romano-Trujillo, E Rosendo, M Ortega, A Morales-Sánchez, T Díaz, M Gracia, G García, G Nieto, C Gutiérrez, H Juárez, A Luna and M Pacio.
    Nanotechnology 23 (2012) doi:10.1088/09574484/23/18/185602 F. I. 3.979
    Lead selenide nanoparticles (PbSe NPs) have been obtained through an easy and low cost route using colloidal synthesis in aqueous solution. The synthesis was carried out at room temperature using Extran (Na5P3O10, NaOH and H2O) as surfactant. Hydrochloric acid (HCl) was used to eliminate the generated by-products. The size of PbSe NPs was varied by changing the Pb:Se molar concentration. The PbSe NPs were characterized by powder x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray analysis (EDAX), high-resolution transmission electron microscopy (HRTEM) and Raman spectroscopy. The XRD measurements showed that the PbSe NPs have the face-centered cubic phase structure. The crystal size was found to be between 14 and 20 nm as calculated from the XRD patterns and these values were corroborated with SEM and TEM. Additionally, HRTEM micrographs showed crystalline planes at (200), (220) and (111) of the PbSe NPs, in agreement with the XRD results.
  13. Influence of the activation atmosphere on the hydrodesulfurization of Co-Mo/SBA-15 catalysts prepared from sulfur-containing precursors
    G. Alonso-Núñez; J. Bocarando; R. Huirache-Acuña; L. Álvarez-Contreras; Z.-D. Huangd ;W. Benschd; G. Berhault; J. Cruz; T.A. Zepeda; S. Fuentes..
    Analytical and Bioanalytical Chemistry 419-420 (2012) 95-101 F. I. 3.903
    Mesoporous SBA-15 material was used as support of binary Co-Mo hydrodesulfurization (HDS) catalysts prepared using a novel approach based on the use of already sulfided precursors (ammonium tetrathiomolybdate and cobalt diethyldithiocarbamate). The effects of atmosphere and activation temperature were studied to optimize the preparation of highly active CoMo/SBA-15 hydrodesulfurization catalysts. Two sets of catalysts were synthesized using either a N2/H2 (10% H2) or a H2/H2S (15% H2S) atmosphere at three different temperatures of activation (723, 773 and 823 K). The catalysts were tested in the HDS of dibenzothiophene (DBT) and the catalysts were characterized by N2 physisorption, X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The use of already sulfided precursors leads to a homogeneous dispersion of the active phase inside the SBA-15 channels. Moreover, the N2/H2 activation procedure at 723 K allows obtaining optimized HDS active catalysts. Finally, a confinement effect of MoS2 slabs inside the SBA-15 channels leads to a high selectivity along the direct desulfurization pathway.
  14. Tungsten disulfide catalysts from tetraalkylammonium thiotungstates by ex situ activation, their properties and HDS activity
    Romero-Rivera, R ; Berhault, G (Berhault, G.)3; Alonso-Nunez, G (Alonso-Nunez, G.)4; Del Valle, M (Del Valle, M.)1; Paraguay-Delgado, F (Paraguay-Delgado, F.)2; Fuentes, S (Fuentes, S.)4; Salazar, S (Salazar, S.)1; Aguilar, A (Aguilar, A.)2; Cruz-Reyes, J (Cruz-Reyes, J.)1.
    Applied Catalysis A-General 433 (2012) 115-121 F. I. 3.903
    The role of carbon coming from tetraalkylammonium thiotungstate precursors during the ex situ activation of WS2 catalysts was herein studied through the comparison of two different thiosalts, ammonium tetrathiotungstate (ATT, without carbon) and cetyltrimethylammonium tetrathiotungstate (CTATT, with carbon). The influence on the resulting WS2 catalysts, of a N-2 vs a H2S/H-2 (20% H2S) atmosphere during ex situ activation was also evaluated. Freshly obtained catalysts were characterized by N-2 adsorption-desorption isotherms, X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX), while their catalytic properties were evaluated in the hydrodesulfurization of dibenzothiophene at 3.1 MPa and 623 K. No significant difference was found in the textural and morphological properties of the final WS2 catalysts derived from thermal decomposition of ATT under N-2 flow, compared to 20% H2S/H-2 flow. In contrast, the textural, morphological and catalytic properties of WS2 catalysts derived from CTATT were strongly influenced by the nature of the atmosphere. Samples of WS2 derived from ATT showed an absence of porosity, while WS2 catalysts formed from CTATT presented a mesoporous organization characterized by type IV N-2 isotherms. XRD and TEM showed that the use of CTATT induces a strong destacking of the WS2 particles and the excessive formation of amorphous carbon, thus yielding less active WS2 catalysts which confirm the negative role of carbon-containing tetraalkylammonium precursors in the activation of WS2 catalysts, as opposed to their positive influence in the activation of MoS2 catalysts. The very high activity of the WS2 catalyst obtained from ATT is attributed to an optimized incorporation of structural carbon inside the WS2 structure. Finally, selectivity results show the depleted hydrogenating character of the WS2 catalysts formed from CTATT.
  15. Automated total and radioactive strontium separation and preconcentration in samples of environmental interest exploiting a lab-on-valve system
    Rogelio Rodríguez, Jessica Avivar, Laura Ferrer, Luz O. Leal, Víctor Cerdà.
    Talanta 96 (2012) 96-101 F. I. 3.794
    A novel lab-on-valve system has been developed for strontium determination in environmental samples. Miniaturized lab-on-valve system potentially offers facilities to allow any kind of chemical and physical processes, including fluidic and microcarrier bead control, homogenous reaction and liquid–solid interaction. A rapid, inexpensive and fully automated method for the separation and preconcentration of total and radioactive strontium, using a solid phase extraction material (Sr-Resin), has been developed. Total strontium concentrations are determined by ICP-OES and 90Sr activities by a low background proportional counter. The method has been successfully applied to different water samples of environmental interest. The proposed system offers minimization of sample handling, drastic reduction of reagent volume, improvement of the reproducibility and sample throughput and attains a significant decrease of both time and cost per analysis. The LLD of the total Sr reached is 1.8 ng and the minimum detectable activity for 90Sr is 0.008 Bq. The repeatability of the separation procedure is 1.2% (n = 10).
  16. Automated system for on-line determination of dimethylarsinic and inorganic arsenic by hydride generation-atomic fluorescence spectrometry
    Chaparro, LL (Chaparro, L. L.) Ferrer, L (Ferrer, L.); Cerda, V (Cerda, V.); Leal, LO (Leal, L. O.).
    Analytical and Bioanalytical Chemistry 404 (2012) 1589-1595 F. I. 3.778
    A multisyringe flow-injection approach has been coupled to hydride generation-atomic fluorescence spectrometry (HG-AFS) with UV photo-oxidation for dimethylarsinic (DMA), inorganic As and total As determination, depending on the pre-treatment given to the sample (extraction or digestion). The implementation of a UV lamp allows on-line photo-oxidation of DMA and the following arsenic detection, whereas a bypass leads the flow directly to the HG-AFS system, performing inorganic arsenic determination. DMA concentration is calculated by the difference of total inorganic arsenic and measurement of the photo-oxidation step. The detection limits for DMA and inorganic arsenic were 0.09 and 0.47 mu g L-1, respectively. The repeatability values accomplished were of 2.4 and 1.8 %, whereas the injection frequencies were 24 and 28 injections per hour for DMA and inorganic arsenic, respectively. This method was validated by means of a solid reference material BCR-627 (muscle of tuna) with good agreement with the certified values. Satisfactory results for DMA and inorganic arsenic determination were obtained in several water matrices. The proposed method offers several advantages, such as increasing the sampling frequency, low detection limits and decreasing reagents and sample consumption, which leads to lower waste generation.
  17. Analysis of Corrosion Behavior of Ti-15Mo Alloys
    C.G. Nava-Dino1,5, R. G. Bautista-Margulis2 ,M. A. Neri-Flores1, M. V. Orozco-Carmona1, S.D de la Torre3, J.G. Gonzalez-Rodriguez4, J. G. Chacon-Nava1 and A. Martínez Villafañe1..
    International Journal of Electrochemical Science 7 (2012) 4250 - 4260 F. I. 3.729
    The Ti-15Mo alloys have been studied by using electrochemical measurements. The electrochemical test was made to analyze their resistance and predictability to corrosion from green dust samples, SPS samples and arc-melt alloying. The corrosion behavior in Ringer’s solution was evaluated by Potentiodynamic polarization curves, electrochemical noise and SEM (Scanning Electron Microscope).
    Images were used to study corrosion behavior and corrosion predictability
  18. Carbonation Rate and Reinforcing Steel Corrosion of Concretes with Recycled Concrete Aggregates and Supplementary Cementing Materials
    S. P. Arredondo-Rea 1, R. Corral-Higuera 1,*, J. M. Gómez-Soberón3, J.H. Castorena-González1, V. Orozco-Carmona2, J.L. Almaral-Sánchez1.
    International Journal of Electrochemical Science 7 (2012) 1602 - 1610 F. I. 3.729
    Because of the significant environmental impact that the concrete production causes, and as sustainability contribution for this industry; presently some improvements are being implemented in its durability and its components are been replaced for alternative recyclable materials. Concrete carbonation is one of the main causes of reinforcement electrochemical corrosion. Coarse Recycled Concrete Aggregates (RCA) and Supplementary Cementing Materials (SCM) such as fly ash and silica fume were used to produce durable and environmentally friendly concrete and for the evaluation of its carbonation depth and carbonation-induced reinforcement corrosion when it is exposed to accelerated conditions. The depth of carbonation was observed by spraying a phenolphthalein solution on the fresh broken concrete surface. The corrosion rates of steel embedded in these concretes have been measured by the lineal polarization resistance technique. The results indicate that to use RCA and SCM increase the carbonation depth and corrosion current density.
  19. Cement Based Anode in the Electrochemical Realkalisation of Carbonated Concrete
    C.P. Barrios Durstewitz, F. J. Baldenebro López, R.E. Núñez Jaquez, G. Fajardo, F. Almeraya,E. Maldonado-Bandala., M. Baltazar-Zamora., J.H. Castorena.
    International Journal of Electrochemical Science 7 (2012) 3178 - 3190 F. I. 3.729
    A nondestructive technique to revert concrete carbonation is the electrochemical realkalisation (ER) that consists in applying a direct current between the steel bars and an external auxiliary electrode placed on concrete surface with the aim of restoring the alkalinity loss. In the present work is studied the use of a conductive mortar as anode in the electrochemical realkalisation of concrete. Carbonated reinforced concrete specimens with a water/cement ratio of 0.65 were evaluated. ER was applied by 5 day period with a current density of 2 A/m2 and using as anode a layer of modified mortar (add 25% graphite powder by cement weight) saturated with a 1M Na2CO3 solution. The pH in the concrete was determined by phenolphthalein test and potentiometric titration. After the ER treatment the pH value of the carbonated concrete samples had increased from 8 to 12.
  20. Corrosion Behavior of Ti-6Al-4V Alloys.
    1. C.G. Nava-Dino, C. López-Meléndez R. G. Bautista-Margulis, M. A. Neri-Flores, J.G. Chacón-Nava, S.D de la Torre, J.G. González- Rodríguez and A. Martínez-Villafañe..
    International Journal of Electrochemical Science 7 (2012) 2389 - 2402 F. I. 3.729
    The alloy Ti-6Al-4V has been considered ideal for implant applications. Electrochemical tests were made to analyze their resistance and predictability to corrosion from green dust samples, SPS (Spark
    Plasma Sintering) samples and commercial alloying. The corrosion behavior in Ringer´s and Hank´s solution was evaluated by SEM (Scanning Electron Microscope). Fractal dimension were used to study corrosion behavior and corrosion predictability was observed by modeling studies.
  21. Dynamic Study of Current Fluctuations of Nanostructured Films.
    C. López- Meléndez1,2, E. M Garcia-Ochoa3, M.I. Flores-Zamora4, , R.G. Bautista-Margulis5, C. Carreño-Gallardo1, C.P. Castillo Morquecho1 , J.G. Chacon-Nava1, A. Martínez-Villafañe1*..
    International Journal of Electrochemical Science 7 (2012) 1160-1169 F. I. 3.729
    The objective of the current research work is to study the polarization curves and electrochemical noise, the performance and nonlinear dynamic of corrosion protection of a nanostructured thin film of AISI 304 stainless steel on a AISI 304 substrate applied by magnetron sputtering technique. The graphical analysis of recurrence (recurrence plot) and the determination of the fractal dimension of the current time series were obtained from the nonlinear analysis techniques used.
  22. Efficiency of Galvanized Steel Embedded in Concrete Previously Contaminated with 2, 3 and 4% of NaCl
    M.A. Baltazar-Zamora1, E. Maldonado-Bandala1, M.U. Loya Tello2, G. Santiago-Hurtado1,F.J. Olguín Coca3, A. Ortiz-Cedano1, C. P. Barrios D4, R. E. Núñez J.4, P. Zambrano R5, C. Gaona-Tiburcio5*, F. Almeraya-Calderón2,5.
    International Journal of Electrochemical Science 7 (2012) 2997 - 3007 F. I. 3.729
    The results are reported from the evaluation of corrosion rate of galvanized steel embedded in concrete specimens contaminated with different concentrations of NaCl and exposed to a simulated marine environment for a period of 320 days to compare their efficiency with steel-1018 used worldwide. The mixture was designed according to the standard ACI 211.1 considering a resistance of 250kg/cm² at 28 days. Was evaluated the potential corrosion (ASTM C 876-99 standard) and corrosion rate with the electrochemical technique of linear polarization resistance (LPR). The results show a significant protection against the corrosion of galvanized steel bars after 138 days of exposure when is embedded in an uncontaminated concrete. Was observed that in contaminated concretes the performance of galvanized as protection against corrosion is not efficient; is only a viable option to increase the service life of concrete structures with their respective limitations.
  23. Electrochemical Impedance Spectroscopy Behavior of Nanometric Al-Cr, Cr-Al Coatings by Magnetron Sputtering.
    C. P. Castillo Morquecho1, C. López Meléndez1, M.I. Flores-Zamora2, R.G. Bautista-Margulis3, H. E. Esparza Ponce 1, F. Almeraya Calderón 1,4, C. Gaona Tiburcio4, A. Martínez-Villafañe1,*.
    International Journal of Electrochemical Science 7 (2012) 1125-1133 F. I. 3.729
    Multilayer and bilayers structures have attracted much attention as a way of improving the mechanical and corrosion resistance properties of protective coatings. In this work the application of nanometric Al/Cr and Cr/Al bilayers deposited on AA2024-T3, AA60601-T6 aluminum alloys and AISI 9840 steel by magnetron sputtering and DC sputtering was studied. The materials were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and electrochemical impedance spectroscopy (EIS) in order to consider their application as high corrosion resistance coatings. The corrosion behavior of the films was studied using a NaCl aqueous solution (3.5 wt %)
  24. Evaluation of Corrosion Resistance of Thin Films 304 Stainless Steel Deposited by Sputtering.
    C. López-Meléndez1,2, R.G. Bautista-Margulis3, E. M Garcia-Ochoa4, H. E. Esparza-Ponce1, C. Carreño-Gallardo1, C. Gaona-Tiburcio5, J. Uruchurtu-Chavarín6, A. Martínez-Villafañe1,*.
    International Journal of Electrochemical Science 7 (2012) 1149-1159 F. I. 3.729
    At present, new materials have been developed in the form of a thin film, due to the nanometer level improvement in the properties of bulk materials and this is increasingly important in materials science and engineering. In the present work, thin films of stainless steel 304 were grown in situ on substrate of the same material, with the technique of magnetron sputtering, three temperatures of deposit were varied: 25, 100 and 200°C, with the objective to reduce the particle size and increase resistance to corrosion. The films were microstructurally characterized by a) scanning electron microscope field emission to analyze the thickness of the film, b) atomic force microscopy to determine particle size and c) X-ray diffraction to obtain the phase analysis. The behavior to the corrosion was established by means of the techniques of potentiodynamic polarization curves and electrochemical noise. The results of the micrographs showed that the effect of the deposition temperature in the thin films (aids at reducing) the size of particle being minor to the conventional steel, homogenize the size with increasing temperature. The study of X-rays diffraction showed that as the temperature of the substratum increases the austenite phase is clearly defined. The results of Potentiodynamic polarization curves have allowed demonstrating that the films help in decreasing the corrosion susceptibility of this material. Likewise, the technique of electrochemical noise indicated the type of corrosion that it would be present in an aggressive environment such as sodium chloride showing corrosion pitting.
  25. Evaluation of the Corrosion at Early Age in Reinforced Concrete Exposed to Sulfates
    Baltazar-Zamora, MA (Baltazar-Zamora, M. A.)1; Santiago, G (Santiago H, G.)1; Tiburcio, CG (Gaona Tiburcio, C.)5; Maldonado-Bandala, EE (Maldonado-Bandala, E. E.)1; Barrios-Durstewist, CP (Barrios-Durstewist, C. P.)3; Nunez, RE (Nunez-J, R. E.)3; Perez-Lopez, T (Perez-Lopez, T.)4; Zambrano, P (Zambrano R, P.)5; Almeraya-Calderon, F (Almeraya-Calderon, F.)2,5.
    International Journal of Electrochemical Science 7 (2012) 588 - 600 F. I. 3.729
    One of the mainly corrosion mechanisms in reinforced concrete structures (RCS) is the attack by sulfates, due to the cracking that cause this attack, is accelerates the penetration of the sulfate ion in the RCS's, and causing depassivation of steel reinforced and generate the formation of electrochemical cells, triggering the corrosion of reinforcement steel. However, the present work shows the results of the electrochemical evaluation of reinforced concrete specimens expose in a 3 to 5% (Na2SO4) solutions during 120 days. The concrete was elaborated with water/cement ratio of 0.4, 0.5 and 0.6. The results obtained with the linear polarization resistance (LPR), shown that at early age the attack by sulfates is negligible and there is no difference between the different w/c, and the concentrations of sulfates for a well performance of the concrete under study
  26. Statistical Analysis of Factors Influencing Corrosion in Concrete Structures
    D. Nieves-Mendoza1, C. Gaona-Tiburcio4, H. L. Hervert-Zamora2, R. Tobias J2., P. Castro-Borges3, R.
    Colas O4, P. Zambrano Robledo4,Martínez-Villafañe A5., F. Almeraya-Calderón4,5,*.
    International Journal of Electrochemical Science 7 (2012) 5495-5509 F. I. 3.729
    The use of mathematical and statistical models has allowed the description of the behavior of many natural phenomena. However, their application in civil engineering particularly, for the analysis of the corrosion behavior, has been overlooked in recent studies. In the present work, a factorial analysis with subdivided parcels design were conducted to evaluate the corrosion rate behavior of arrangements of protected and not protected steel bars found in reinforced concrete specimens subject to two different aggressive media. The results showed that, in comparison to sulphate ions, the effect of chloride ions on the corrosion rate was not statistically significant. In the same way, protected and not protected segments on the steel bars (i.e., steel bar condition) did not have a significant effect on the corrosion rate. The only factor found to significantly affect the corrosion rate was the variability of the beam
    fabrication process (i.e., beam factor).
  27. Electrochemical Corrosion Performance of Hematite-Free Magnetite Layer on AISI 4340 by Duplex Pulsed Plasma Nitriding-Oxidizing Treatment.
    J.C. Díaz Guillén. G. Vargas Gutiérrez E.E. Granda Gutiérrez J.A. Aguilar Martínez J. Candelas Ramírez S.I. Pérez Aguilar L. Álvarez Contreras.
    International Journal of Electrochemical Science 7 (2012) 7261-7269 F. I. 3.729
    Plasma assisted duplex processes, such as nitriding post-oxidation, has been the focus of recent research publications looking to optimize wear and corrosion performance of several industrial components. High efficiency, process control as well as low energy consumption and clean technologies suggest that these processes are good alternatives for replacing the environmental harmful electrochemical techniques. An important challenge during post oxidation step is to avoid, as much as possible, the formation of hematite (Fe2O3) and to produce layers with a high content of high corrosion resistance magnetite (Fe3O4). In the present work, pulsed DC plasma post oxidation was used in order to obtain hematite-free magnetite layers on plasma nitrided AISI 4340 steel in order to improve its corrosion resistance. The effect of oxidation time (15, 30 and 45 minutes) on crystalline phases content and electrochemical corrosion performance was evaluated. Rietveld analysis of X ray diffraction data
    shows an increase in magnetite content and a decrease in Fe3N content after the post-oxidation period. Corrosion performance of nitrided AISI 4340 steel was significantly enhanced by the smoothest surface and the hematite-free magnetite layer obtained after pulsed post-oxidation process.
  28. Comparison of Electrochemical Noise (EN) Signal and Corrosion Products Signal Image of Ti-6Al-4V.
    C.G. Nava Dino, G. López Ocaña, J. A. Cabral Miramontes, M.A. Luna Ramírez, H. Monreal Romero, R. Bautista Margulis, J.G. Chacón Nava, A. Martínez Villafañe..
    International Journal of Electrochemical Science 11 (2012) 11182- 11190 F. I. 3.729
    Electrochemical noise (EN) measurements and their corrosion products were observed by Scanning Electron Microscopy (SEM). Digital image process allows changing the image result of corrosion products in an equivalent signal. Samples of Ti-6Al-4V were produced by mechanical milling at different milling times. After that, they are sintering by SPS (Spark Plasma Sintering) to predict the behavior of the samples in Hank’s solution. The images obtained by SEM were changed to binary map and then changed to a two-dimensional array. SEM images showed the surface topography of corrosion products.
  29. Electrochemical Noise Study of Ni-Mo Alloys Fabricated by Mechanical Alloying and Densified by Spark Plasma Sintering.
    F. Almeraya-Calderon1,2, R.G. Bautista-Margulis3. C.G. Nava-Dino4. G. López-Ocaña3, C. GaonaTiburcio2, S.D. De la Torre5, J. Castañeda-Avila4 and A. Martínez-Villafañe1,.
    International Journal of Electrochemical Science 7 (2012) 12999 - 13007 F. I. 3.729
    The mechanical alloying (MA) method by the low energy ball milling process has been used to fabricate Ni-Mo based electro-active powder. Nanometric-sized Mo particles have been embedded into agglomerated amorphous matrix. The spark plasma sintering (SPS) process has been used to densify the powder in  6 min at heating rates of about 250°C min -1 from 400 to 1300°C, applying loads of 120 MPa. High performance porous nickel electrodes having new phases with a particle size range between 1.0 and 8.7 m have been obtained after rapid SPS operations. The electrochemical noise (EN) technique has been used to study the behavior of Ni-Mo alloy in KOH 30% solution at 70°C. In this study, the preliminary electrochemical analysis of the porous nickel electrodes was reported.
  30. Identifying Factors Influencing the Corrosion Rate of Steel Using Nonparametric Statistics
    Nieves Mendoza, D ; Gaona Tiburcio, C ; Hervert, HL ; Méndez, RC ; Castro Borges, P ; Borunda, A ; Robledo, PZ ; Almeraya Calderón, F..
    International Journal of Electrochemical Science 7 (2012) 6343-6352 F. I. 3.729
    Statistical techniques have made it possible to describe the behavior of certain phenomena. Nonetheless, given the difficulty in obtaining adequate data, it is common not to have random and homogeneous samples in order to conduct parametric statistical tests (which follow a known distribution). The present study reports results from the use of a non-parametric statistical test (which does not follow a known distribution) known as the Mood test of median differences which was conducted to analyze the corrosion rate of concrete beams exposed to different environmental conditions. The main objective was to statistically determine which factors accelerated the corrosion rate of the beams under study. Results showed that the tested factors (three different concrete covers: 15, 20 and 30 mm, and two water/cement ratios: 0.45 and 0.65), had statistically significant effects on the corrosion rate. Greater corrosion rates were observed for beams with covers of 15 and 20 mm, and with a water/cement ratio of 0.65. Nonetheless, we found that the corrosion rate was not statistically different between sides of the beam facing prevailing winds, and those that were sheltered from them.
  31. Electrochemical Behavior of Reinforced Concrete and Its Relation With the Environment of Xalapa, Veracruz
    Santiago-Hurtado, G; Maldonado-Bandala, EE; Coca, FJO; Almeraya-Calderon, F; Torres-Acosta, A; Baltazar-Zamora, MA..
    International Journal of Electochemical Science 10 (2012) 9825-9834 F. I. 3.729
    In this work it is evaluated the electrochemical performance of reinforced concrete exposed to the environment of the city of Xalapa, Veracruz, to portray the effect in the durability, since this depends not only from its mechanical features but also from the environment in which the structure will be build, as it has been demonstrated in some researches. 12 beams of 15 x 15 x 30 cm were made, 6 with steel to reinforce and 6 without it. Two types of concrete were designed, one with a w/c = 0.65 ratio and the other with a w/c = 0.45 ratio, with the same kind of cement, 3/8 diameter 1018 steel carbon rods, in three types of coating thickness, 15, 20 and 30 mm. The tests to evaluate the oversensitivity to corrosion of the reinforce steel, were resistance to polarization and the monitoring of potential corrosion based in the standard ASTM C-876-09. The obtained results of the first two years of monitoring indicate us noble potentials that indicate a 10% probability of corrosion, the kinetics of corrosion is negligible for 12 rods since 6 of them have a moderate level of corrosion.
  32. Influence of magnetoelectric coupling on electric field induced magnetization reversal in a composite unstrained multiferroic chain
    Horley, PP (Horley, Paul P.)1; Sukhov, A (Sukhov, Alexander)2; Jia, CL (Jia, Chenglong)2,3; Martínez, E (Martínez, Eduardo)1; Berakdar, J (Berakdar, Jamal)2.
    Physical Review B 85 (2012) 54401 F. I. 3.691
    We study theoretically the multiferroic dynamics in a composite one-dimensional system consisting of BaTiO3 multiferroically coupled to an iron chain. The method treats magnetization and polarization as thermodynamic quantities describable via a combination of the Landau-Lifshits-Gilbert and the Ginzburg-Landau dynamics coupled via an additional term in the total free energy density. This term stems from the multiferroic interaction at the interface. For a wide range of strengths of this coupling, we predict the possibility of obtaining a well-developed hysteresis in the ferromagnetic part of the system induced by an external electric field. The dependence of the reversal modes on the electric field frequency is also investigated and we predict a considerable stability of the magnetization reversal for frequencies in the range of 0.5-12 GHz.
  33. Order and Disorder Effects in the nano-crystalline ZrO2: A Micro- Raman and Spectrally and Temporarily Resolved Luminescence Investigation
    Carmen Tiseanu, Bogdan Cojocaru, Vasile I. Parvulescu, Margarita Sánchez - Domínguez, Philipp A. Primus, Magali Boutonnet.
    Physical Chemistry Chemical Physics 14 (2012) 12970-12981 F. I. 3.573
    Pure and europium (Eu3+) doped ZrO2 synthesized by an oil-in-water microemulsion reaction method were investigated by in situ and ex situ X-ray diffraction (XRD), ex situ Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), steady state and time-resolved photoluminescence (PL) spectroscopies. Based on the Raman spectra excited at three different wavelengths i.e. 488, 514 and 633 nm and measured in the spectral range of 150–4000 cm−1 the correlation between the phonon spectra of ZrO2 and luminescence of europium is clearly evidenced. The PL investigations span a variety of steady-state and time resolved measurements recorded either after direct excitation of the Eu3+ f–f transitions or indirect excitation into UV charge-transfer bands. After annealing at 500 °C, the overall Eu3+ emission is dominated by Eu3+ located in tetragonal symmetry lattice sites with a crystal-field splitting of the 5D0–7F1 emission of 20 cm−1. Annealing of ZrO2 at 1000 °C leads to a superposition of Eu3+ emissions from tetragonal and monoclinic lattice sites with monoclinic crystal-field splitting of 200 cm−1 for the 5D0–7F1 transition. At all temperatures, a non-negligible amorphous/disordered content is also measured and determined to be of monoclinic nature. It was found that the evolutions with calcination temperature of the average PL lifetimes corresponding to europium emission in the tetragonal and monoclinic sites and the monoclinic phase content of the Eu3+ doped ZrO2 samples follow a similar trend. By use of specific excitation conditions, the distribution of europium on the amorphous/disordered surface or ordered/crystalline sites can be identified and related to the phase content of zirconia. The role of zirconia host as a sensitizer for the europium PL is also discussed in both tetragonal and monoclinic phases.
  34. Nanoindentation characterization of the micro-lamellar arrangement of black coral skeleton
    B.A. Juárez-de la Rosaa, , , J. Muñoz-Saldañab, D. Torres-Torresc, P.-L. Ardissond, J.J. Alvarado-Gila, .
    Journal of Structural Biology 177 (2012) 349–357 F. I. 3.406
    Black corals (antipatharians) are colonial cnidarians whose branched tree-like skeleton is mostly constituted of chitin fibrils inside a lipoproteic matrix. The skeleton exhibits growth rings formed by chitin layers (micro-lamellae). In order to know the effect of the arrangement microlamellae of chitin of black corals and to improve the understanding of the role of chitin structure in the antipatharian skeleton, the mechanical properties of the skeleton of two black corals, Antipathes caribbeana and Antipathes pennacea, were examined using nanoindentation tests. Measurements of reduced elastic modulus, nanohardness and the viscoelastic behavior were measured with a spheroconical indenter. The results indicate variations in the values of the mechanical properties clearly associated with different structures present in the skeletons, the core being the one that invariably shows the maximum values. The solid multilamellar arrangement of black coral chitin, its viscoelastic behavior, and the anisotropic mechanical response, are relevant factors contributing to the successful adaptation of black coral colonies to shallow as well as to very deep waters.
  35. Fabricating ordered functional nanostructures onto polycrystalline substrates from the bottom-up
    M. Torres, L. Pardo, J. Ricote, L. E. Fuentes Cobas, B. J. Rodríguez, M. L. Calzada.
    Journal of Nanoparticle Research 14 (2012) doi 10.1007/s11051-012-1108-x F. I. 3.287
    Microemulsion-mediated synthesis has emerged as a powerful bottom-up procedure for the preparation of ferroelectric nanostructures onto substrates. However, periodical order has yet to be achieved onto polycrystalline Pt-coated Si substrates. Here, we report a new methodology that involves microemulsion-mediated synthesis and the controlled modification of the surface of the substrate by coating it with a template-layer of water-micelles. This layer modifies the surface tension of the substrate and yields a periodic arrangement of ferroelectric crystalline nanostructures. The size of the nanostructures is decreased to the sub-50 nm range and they show a hexagonal order up to the third neighbors, which corresponds to a density of 275 Gb in(-2). The structural analysis of the nanostructures by synchrotron X-ray diffraction confirms that the nanostructures have a PbTiO3 perovskite structure, with lattice parameters of a = b = 3.890(0) angstrom and c = 4.056(7) angstrom. Piezoresponse force microscopy confirmed the ferro-piezoelectric character of the nanostructures. This simple methodology is valid for the self-assembly of other functional oxides onto polycrystalline substrates, enabling their reliable integration into micro/nano devices.
  36. Small-scale and household methods to remove arsenic from water for drinking purposes in Latin America
    Marta I. Litter, María Teresa Alarcón Herrera, María J. Arenas, María A. Armienta, Marta Avilés, Roberto E. Cáceres, Henrique Nery Cipriani, Lorena Cornejo, Luiz E. Dias, Alicia Fernández Cirelli, Elsa M. Farfán, Sofía Garrido, Liliana Lorenzo, María. E. Morgada, Mario A. Olmos Márquez, Alejo Pérez Carrera.
    Science of The Total Environment 429 (2012) 107–122 F. I. 3.286
    Small-scale and household low-cost technologies to provide water free of arsenic for drinking purposes, suitable for isolated rural and periurban areas not connected to water networks in Latin America are described. Some of them are merely adaptation of conventional technologies already used at large and medium scale, but others are environmentally friendly emerging procedures that use local materials and resources of the affected zone. The technologies require simple and low-cost equipment that can be easily handled and maintained by the local population. The methods are based on the following processes: combination of coagulation/flocculation with adsorption, adsorption with geological and other low-cost natural materials, electrochemical technologies, biological methods including phytoremediation, use of zerovalent iron and photochemical processes. Examples of relevant research studies and developments in the region are given. In some cases, processes have been tested only at the laboratory level and there is not enough information about the costs. However, it is considered that the presented technologies constitute potential alternatives for arsenic removal in isolated rural and periurban localities of Latin America. Generation, handling and adequate disposal of residues should be taken into account in all cases.
  37. DFT Study of the Effect of Substituents on the Absorption and Emission Spectra of Indigo
    Francisco Cervantes-Navarro and Daniel Glossman-Mitnik.
    Chemistry Central Journal 6 (2012) doi:10.1186/1752-153X-6-70 F. I. 3.281
    Theoretical analyses of the indigo dye molecule and its derivatives with Chlorine (Cl), Sulfur(S), Selenium (Se) and Bromine (Br) substituents, as well as an analysis of the Hemi-Indigo molecule, were performed using the Gaussian 03 software package.
    Results. Calculations were performed based on the framework of density functional theory (DFT) with the Becke 3- parameter-Lee-Yang-Parr (B3LYP) functional, where the 6-31 G(d,p) basis set was employed. The configuration interaction singles (CIS) method with the same basis set was employed for the analysis of excited states and for the acquisition of the emission spectra.
    Conclusions. The presented absorption and emission spectra were affected by the substitution position. When a hydrogen atom of the molecule was substituted by Cl or Br, practically no change in the absorbed and emitted energies relative to those of the indigo molecule were observed; however, when N was substituted by S or Se, the absorbed and emitted energies increased.
  38. Synthesis of core-shell composites using an inverse surfmer
    E. Armando Zaragoza-Contreras, Margarita Stockton-Leal, Claudia A. Hernández-Escobar, Yusuke Hoshina, Josué F. Guzmán-Lozano, Takaomi Kobayashi.
    Journal of Colloid and Interface Science 377 (2012) 231-236 F. I. 3.07
    Anilinium dodecylsulfate was prepared from aniline and sodium dodecylsulfate. The critical micellar concentration of the salt was determined using electrical conductimetry, which revealed that the change of countercation, sodium by anilinium, reduced the critical micellar concentration with respect to the conventional counterpart, sodium dodecylsulfate. The anilinium dodecylsulfate was used as the surfmer in the synthesis of polystyrene/polyaniline core-shell composites, first performing as the surfactant to stabilize the emulsion polymerization of styrene, and later as the monomer to synthesize polyaniline via oxidative polymerization. Here, the surfmer function was directed toward the external phase instead of to the internal phase, as with conventional surfmers with carbon-carbon double bonds. Consequently, the term inverse surfmer is proposed. Analyses of its composite microstructure using electron microscopy and thermogravimetric analysis confirmed the core-shell arrangement.
  39. Multiparametric automated system for sulfate, nitrite and nitrate monitoring in drinking water and wastewater based on sequential injection analysis
    Ayala, A (Ayala, A.)2; Leal, LO (Leal, L. O.)2; Ferrer, L (Ferrer, L.)1; Cerda, V (Cerda, V.)1.
    Microchemical Journal 100 (2012) 55-60 F. I. 3.048
    An automated monitoring system for sulfate, nitrite and nitrate based on sequential injection analysis (SIA) was developed. For nitrite determination the modified Griess-Ilosvay method was used, whereas nitrate was previously reduced to nitrite using a cadmium column followed by nitrite determination. A turbidimetric method was carried out in order to determine sulfate. The results showed that the proposed SIA monitoring system constitutes an effective approach for nitrite, nitrate and sulfate determination since it is able to determine levels required by international agencies that regulate these parameters in water. Detection limits of 0.0207 mg N L(-1), 0.0022 mg N L(-1) and 3 mg SO(4)(2-) L(-1) were obtained for nitrate, nitrite and sulfate, respectively. The developed method offers also typical characteristics of the multicommutated systems, as portability, low reagents consumption and the subsequently minimization of waste generation. The proposed system was successfully applied to drinking water and wastewater samples and validated with a certified river water sample (10N-96.3, LGC Standards).
  40. Photodeposition of Ni nanoparticles on TiO2 and their application in the catalytic ozonation of 2,4-dichlorophenoxyacetic acid
    Rodríguez, JL; Valenzuela, MA; Pola, F ; Tiznado, H.; Poznyak, T..
    Journal of Molecular Catalysis A-Chemical 353 (2012) 29-36 F. I. 2.947
    Different photochemical approaches have been investigated to prepare supported nickel nanoparticles to be used in the catalytic ozonation of 2,4-dichlorophenoxyacetic acid (2,4-D). Direct photochemical (lambda = 365 nm, without TiO2) and photocatalytic deposition in presence or absence of sensitizers (TiO2, acetone or benzophenone) were employed. The characterization of the catalysts was carried out by Xray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The photocatalytic deposition without any sensitizer resulted to be the most suitable method to obtain in very short irradiation time. Ni nanoparticles randomly distributed over the support with a particle size ranging from 7 to 15 nm. An optimization of this technique was performed by varying the mass of TiO2 and the light intensity. According to the results of 2,4-D degradation, the catalytic ozonation with Ni/TiO2 catalyst presented a slightly higher conversion than TiO2 or ozonation alone. These results were explained in terms of the two phases (NiO/Ni) present on the surface of TiO2 which favor the ozone decomposition forming OH radicals useful for 2,4-D degradation. A reaction pathway including all the intermediates formed during the direct attack of ozone and the produced OH radicals was proposed.
  41. Effect of a temperature gradient on ellipsometry measurements in supercritical CO2
    A. Mendoza-Galván, C. Trejo-Cruz; O. Solís-Canto1, G. Luna-Bárcenas.
    The Journal of Supercritical Fluids 64 (2012) 25-31 F. I. 2.86
    Phase modulated spectroscopic ellipsometry measurements were performed in supercritical CO2 using a Mueller matrix approach allowing the explicit assessment of the cell windows effect on the measurements. The adsorption of CO2 on thermal SiO2 and the swelling of PMMA thin films on a silicon substrate were studied from atmospheric pressure up to 13.89 MPa at 35 and 50 °C. A systematic analysis of the deviations between experimental and calculated spectra reveals the presence of a temperature gradient in the vicinity of CO2's critical point where large density fluctuations are present. The temperature gradient produces a graded CO2 refractive index resulting in a pressure-dependent angle of incidence. This mirage effect is analyzed with a simple model that considers the equation of state for CO2 allowing the evaluation of the temperature gradient. Our results are intended to provide a better understanding of spectroscopy ellipsometry studies in supercritical CO2.
  42. Comparative study on the mechanical and fracture properties of acrylic bone cements prepared with monomers containing amine groups
     May-Pat, A (May-Pat, Alejandro)1,2; Herrera-Kao, W (Herrera-Kao, Wilberth)1; Cauich-Rodriguez, JV (Cauich-Rodriguez, Juan V.)1; Cervantes-Uc, JM(Cervantes-Uc, José M.)1; Flores-Gallardo, SG (Flores-Gallardo, Sergio G.)2.
    Journal Of The Mechanical Behavior Of Biomedical Materials 6 (2012) 95-105  F. I. 2.814
    In this work, the effect of the incorporation of comonomers containing amine groups on the mechanical and fracture properties of acrylic bone cements was studied. Cements were prepared with either diethyl amino ethyl acrylate (DEAEA), dimethyl amino ethyl methacrylate (DMAEM) or diethyl amino ethyl methacrylate (DEAEM) as comonomer in the liquid phase. It was found that strength and modulus decreased with increasing comonomer content in the bending and compressive tests. It was also observed that fracture toughness (K-IC) and the critical strain energy release rate (G(IC)) increase with increasing comonomer concentration and are significantly higher compared to the control formulation. The mechanical and fracture properties of cements were also evaluated after soaking the specimens in Simulated Body Fluid (SBF) for 3 and 6 months. It was found that the mechanical properties of cements decreased when the samples were stored in SBF, although the impact strength increased in the first 3 months and then decreased. SEM micrographs were in agreement with the results obtained during mechanical characterization as the increase in toughness was confirmed by the appearance of ductile tearing pattern which is associated with plastic deformation.
  43. The effects of porosity on optical properties of semiconductor chalcogenide films obtained by the chemical bath deposition
    Yu.V. Vorobiev, P.P. Horley, J. Hernández Borja, H.E. Esparza Ponce, R. Ramírez Bon, P. Vorobiev, C. Pérez and J. González Hernández.
    Nanoscale Research Letters 7 (2012) doi:10.1186/1556-276X-7-483 F. I. 2.726
    This paper is dedicated to study the thin polycrystalline films of semiconductor chalcogenide materials (CdS, CdSe, and PbS) obtained by ammonia-free chemical bath deposition. The obtained material is of polycrystalline nature with crystallite of a size that, from a general point of view, should not result in any noticeable quantum confinement. Nevertheless, we were able to observe blueshift of the fundamental absorption edge and reduced refractive index in comparison with the corresponding bulk materials. Both effects are attributed to the material porosity which is a typical feature of chemical bath deposition technique. The blueshift is caused by quantum confinement in pores, whereas the refractive index variation is the evident result of the density reduction. Quantum mechanical description of the nanopores in semiconductor is given based on the application of even mirror boundary conditions for the solution of the Schrödinger equation; the results of calculations give a reasonable explanation of the experimental data.
  44. Modification of optical and electrical properties of zinc oxide-coated porous silicon nanostructures induced by swift heavy ion
    Yogesh Kumar, Manuel Herrera Zaldívar, Sion Federico Olive Méndez, Fouran Singh, Xavier Mathew and Vivechana Agarwal.
    Nanoscale Research Letters 7 (2012) doi: 10.1186/1556-276X-7-366 F. I. 2.72
    Morphological and optical characteristics of radio frequency-sputtered zinc aluminum oxide over porous silicon (PS) substrates were studied before and after irradiating composite films with 130 MeV of nickel ions at different fluences varying from 1 × 10 12 to 3 × 10 13 ions/cm 2 .The effect of irradiation on the composite structure was investigated by scanning electron microscopy, X-ray diffraction (XRD), hotoluminescence (PL), and cathodoluminescence spectroscopy. Current–voltage characteristics of ZnO-PS heterojunctions were also measured. As compared to the granular crystallites of zinc oxide layer, Al-doped zinc oxide (ZnO) layer showed a flaky structure. The PL spectrum of the pristine composite structure consists of the emission from the ZnO layer as well as the near-infrared emission from the PS substrate. Due to an increase in the number of deep-level defects, possibly oxygen vacancies after swift ion irradiation, PS-Al-doped ZnO nanocomposites formed with high-porosity PS are shown to demonstrate a broadening in the PL emission band, leading to the white light emission. The broadening effect is found to increase with an increase in the ion fluence and porosity. XRD study revealed the relative resistance of the film against the irradiation, i.e., the irradiation of the structure failed to completely amorphize the structure, suggesting its possible application in optoelectronics and sensing applications under harsh radiation conditions.
  45. Weak and strong confinements in prismatic and cylindrical nanostructures
    Yuri V Vorobiev, Bruno Mera, Vítor R Vieira, Paul P Horley and Jesús González Hernández.
    Nanoscale Research Letters 7 (2012) doi:10.1186/1556-276X-7-371 F. I. 2.72
    Cylindrical nanostructures, namely, nanowires and pores, with rectangular and circular cross section are examined using mirror boundary conditions to solve the Schrödinger equation, within the effective mass approximation. The boundary conditions are stated as magnitude equivalence of electron's Ψ function in an arbitrary point inside a three-dimensional quantum well and image point formed by mirror reflection in the walls defining the nanostructure. Thus, two types of boundary conditions - even and odd ones - can be applied, when Ψ functions in a point, and its image, are equated with the same and the opposite signs, correspondingly. In the former case, the Ψ function is non-zero at the boundary, which is the case of a weak confinement. In the latter case, the Ψ function vanishes at the boundary, corresponding to strong quantum confinement. The analytical expressions for energy spectra of electron confined within a nanostructure obtained in the paper show a reasonable agreement with the experimental data without using any fitting parameters.
  46. Antimicrobial sensibility of Streptococcus mutans serotypes to silver nanoparticles
    Espinosa-Cristobal, LF; Martínez-Castanon, GA Martinez-Martinez, RE; Loyola-Rodriguez, JP ; Patino-Marin, N; Reyes-Macias, JF; Ruiz, F..
    Materials Science & Engineering C-Materials for Biological Applications 32 (2012) 896-901 F. I. 2.686
    Dental caries is a common infectious disease in humans all over the world and is considered a public health problem with an incidence and prevalence still high. The principal pathogen associated with the development of dental caries is Streptococcus mutans (S. mutans), a microorganism that has been widely studied. A new approach to treat dental caries is the use of silver nanoparticles (SNP) due to their antibacterial effect. It has been reported the effectiveness of SNP against S. mutans, but sensibility of S. mutans serotypes to SNP is still unknown. The aim of this study is to analyze the inhibitory effect of three different sizes of silver nanoparticles on S. mutans obtained from clinical isolates and one reference bacteria strain, determining sensibility differences between serotypes, which were determined by using PCR analysis. Silver nanoparticles with sizes around 9.3, 21.3 and 98 nm were prepared, characterized and used to find, with a microdilution method, the minimum inhibitory concentration (MIC) on S. mutans. SNP showed bactericidal effect on all strains tested with statistical differences between smaller nanoparticles and larger nanoparticles, 9.3 nm SNP showed a higher antibacterial activity than 21.3 and 98 nm SNP; however, sensibility was different among all clinical strains (p<0.05) being serotype c the most sensible and serotype e the most resistant to the three different sizes of SNP considering the inhibitory effect better when nanoparticle size is smaller.
  47. Performance of Eleocharis macrostachya and its importance for arsenic retention in constructed wetlands
    Olmos-Marquez, MA (Alberto Olmos-Marquez, Mario)1; Alarcon-Herrera, MT (Teresa Alarcon-Herrera, Maria)1; Martin-Dominguez, IR (Ramiro Martin-Dominguez, Ignacio)1.
    Environmental Science and Pollution Research 19 (2012) 763-771 F. I. 2.651
    Introduction Arsenic (As) can be removed from water via rhizofiltration using phytostabilizing plants. The aim of this study was to investigate the performance of Eleocharis macrostachya in constructed wetland prototypes, as well as the plant's arsenic mass retention and the distribution of As along the wetland flow gradient and the soil in the wetland mesocosmos. Materials and methods Experiments were carried out in laboratory-scale wetland prototypes, two planted with E. macrostachya and one without plants. Samples of water were taken at the inlet and outlet of the wetlands during the 33-week test period. At the end of the experiment, plants and soil (silty-sand) from each prototype were divided in three equal segments (entrance, middle and exit) and analyzed for their arsenic content. Results revealed that the planted wetlands have a higher As-mass retention capacity (87-90% of the total As inflow) than prototypes without plants (27%). Results As mass balance in the planted wetlands revealed that 78% of the total inflowing As was retained in the soil bed. Nearly 2% was absorbed in the plant roots, 11% was flushed as outflow, and the fate of the remaining 9% is unknown. In the prototype without plants, the soil retained 16% of As mass, 72% of the arsenic was accounted for in the outflow, and 12% was considered unknown. Although E. macrostachya retained only 2% of the total arsenic mass in their roots, its presence was a determining factor for arsenic retention in the wetland soil medium. Conclusion Hence, planted wetlands might be a suitable option for treating As-contaminated water.
  48. Density Functional Theory (DFT) Study of Triphenylamine-Based Dyes for Their Use as Sensitizers in Molecular Photovoltaics
    Jesús Baldenebro-López1,2 , José Castorena-González2 , Norma Flores-Holguín1 , Jorge Almaral-Sánchez2 and Daniel Glossman-Mitnik1.
    International Journal of Molecular Sciences 13 (2012) 4418-4432 F. I. 2.598
    In this work we studied three dyes which are proposed for potential photovoltaic applications and named Dye7, Dye7-2t and Dye7-3t. The Density Functional Theory (DFT) was utilized, using the M05-2X hybrid meta-GGA functional and the 6–31+G(d,p) basis set. This level of calculation was used to find the optimized molecular structure and to predict the main molecular vibrations, the absorption and emission spectra, the molecular orbitals energies, dipole moment, isotropic polarizability and the chemical reactivity parameters that arise from Conceptual DFT. Also, the pKa values were calculated with the semi-empirical PM6 method.
  49. DFT Study of Nanomaterials for their Use as Sensitizers in Molecular Photovoltaics
    Jesús Baldenebro López, José Castorena González, Norma Flores Holguín, Jorge Almaral Sánchez and Daniel Glossman Mitnik.
    International Journal of Molecular Sciences 13 (2012) 4438-4432 F. I. 2.598
    In this work we studied three dyes which are proposed for potential photovoltaic applications and named Dye7, Dye7-2t and Dye7-3t. The Density Functional Theory (DFT) was utilized, using the M05-2X hybrid meta-GGA functional and the 6–31+G(d,p) basis set. This level of calculation was used to find the optimized molecular structure and to predict the main molecular vibrations, the absorption and emission spectra, the molecular orbitals energies, dipole moment, isotropic polarizability and the chemical reactivity parameters that arise from Conceptual DFT. Also, the pKa values were calculated with the semi-empirical PM6 method.
  50. Computational Molecular Nanoscience Study of the Properties of Copper Complexes for Dye-Sensitized Solar Cells
    Jesús Baldenebro-López 1,2 , José Castorena-González 2 , Norma Flores-Holguín 1 , Jorge Almaral-Sánchez 2 and Daniel Glossman-Mitnik 1, .
    International Journal of Molecular Sciences 13 (2012) 16005-16019 F. I. 2.598
    In this work, we studied a copper complex-based dye, which is proposed for potential photovoltaic applications and is named Cu (I) biquinoline dye. Results of electron affinities and ionization potentials have been used for the correlation between different levels of calculation used in this study, which are based on The Density Functional Theory (DFT) and time-dependent (TD) DFT. Further, the maximum absorption wavelengths of our theoretical calculations were compared with the experimental data. It was found that the M06/LANL2DZ + DZVP level of calculation provides the best approximation. This level of calculation was used to find the optimized molecular structure and to predict the main molecular vibrations, the molecular orbitals energies, dipole moment, isotropic polarizability and the chemical reactivity parameters that arise from Conceptual DFT.
  51. Effect of different acid and lithium salt used in polyethylene glycol titanium oxide based solvent-free electrolytes on electrochromic performance of WO3 thin films
    Narcizo Mendoza, Francisco Paraguay-Delgado, Hailin Hu..
    Solar Energy 86 (2012) 997 F. I. 2.475
    Polymeric nanocomposites of polyethylene glycol (PEG) with titanium oxide compound, PEG–Ti, are solvent-free viscous materials obtained by sol–gel method in acidic medium. Lithium salt (LiX) has been added into PEG–Ti to form PEG–Ti–LiX polymeric electrolytes. Electrochromic devices based on tungsten oxide thin films and PEG–Ti–LiX electrolyte may show excellent optical contrast in the wavelength range from 300 to 2500nm, however it depends on the type of lithium salt as well as the acid source used during the sol–gel process. With LiI, the color change speed of the devices is very fast, but they show a yellow color at bleaching state. Highlights: Polyethylene glycol (PEG)–TiO2 complex was prepared by sol–gel in acidic condition. Strong acid promotes the crosslinking between PEG and titanium oxide complex. Low solubility of LiClO4 in PEG deteriorates WO3 electrochromic performance. HCl or LiI gives larger color change speed (ν) and optical contrast (ΔT) in devices. Acetic acid or LiClO4 increases the visible transparency but reduces ν and ΔT.
  52. Compressive strength of HPC containing CNI and fly ash after long-term exposure to a marine environment
    López-Calvo, HZ (López-Calvo, H. Z.)1; Montes-García, P (Montes-García, P.)2; Bremner, TW (Bremner, T. W.)1; Thomas, MDA (Thomas, M. D. A.)1; Jiménez-Quero, VG (Jiménez-Quero, V. G.)2,3.
    Cement & Concrete Composites 34 (2012) 110-118 F. I. 2.421
    This study addressed the effect of calcium nitrite based corrosion inhibitor (CNI) and fly ash (FA) on the long-term compressive strength of high performance concrete (HPC). A 3(3) full factorial design was developed to evaluate the influence of CNI at addition rates of 0, 12.5 and 25 L/m(3) on the compressive strength of HPC manufactured with 8% silica fume blended cement in combination with 0%, 20% and 40% FA replacements and mixed at 0.29, 0.37 and 0.45 water to cementing materials ratios (w/cm). Standard 100 x 200 mm cylinders were prepared and tested for compressive strength at 28 days and 1 year. The 9-year old concrete specimens were obtained from small-scale reinforced concrete slabs that were exposed to a marine environment. Results indicate that the interaction of CNI and FA does not adversely affect the short and long term compressive strength of concrete. In fact, an enhancement on the compressive strength was observed in concretes containing such combination even after long-term exposure to a marine environment.
  53. Effect of cathodicprotection on steel–concrete bondstrength using ionmigrationmeasurements
    J. García*, F. Almeraya, C. Barrios, C. Gaona, R. Núñez, I. López, M. Rodríguez, A. Martínez-Villafañe, J.M. Bastidas.
    Cement & Concrete Composites 34 (2012) 242-247 F. I. 2.421
    mpressed current cathodic protection (ICCP) is a widely used method to protect steel reinforcements against corrosion. Bond degradation between concrete and steel at protection and overprotection levels was studied. Two types of materials were tested: an ordinary Portland cement (OPC) and a mixture of 85% OPC and 15% fly ash (OPC/FA). Concrete specimens were immersed in a 3.5% sodium chloride (NaCl) solution. Chemical analysis of sodium, potassium and hydrogen ions was performed using atomic absorption spectrophotometry (AAS). Hydrogen ion content was monitored using electrochemical impedance spectroscopy (EIS). Mechanical behaviour was analysed by means of pullout tests, and microstructure characterisation was carried out using scanning electron microscopy (SEM). Sodium, potassium and hydrogen ions were found at the concrete–steel interface. The mechanical properties of the specimens were poorer at overprotection level than at protection level.
  54. Hybridization vs. Bond Stretching Isomerism in Ru(II) Cyclometalated Complexes of 2-Phenylpyridine
    Molina, B (Molina, Bertha)2; Alexandrova, L (Alexandrova, Larissa)1; LeLagadec, R (LeLagadec, Ronan)3; Sansores, LE (Sansores, Luis E.)1; Ríos-Jara, D (Ríos-Jara, David)4; Espinosa-Magaña, F (Espinosa-Magaña, Francisco)5; Salcedo, R (Salcedo, Roberto)1.
    Molecules 17 (2012) 34-47 F. I. 2.386
    The phenomenon of formation of two isomers, yellow and orange, of the cyclometalated Ru(II) complex, [Ru(o-C6H4-py)(MeCN)(4)](+), was investigated by EELS spectroscopy and theoretical calculations. Both forms show very similar structures and spectroscopic properties, but slight differences in X-ray data and absorption between them were noted. No double minimum on the potential energy surface was found and thus these two forms cannot be considered as bond stretching isomers. However, the DFT study revealed the change in the hybridization of the carbon in trans-position of one of acetonitrile ligands. This effect can be responsible for the difference in colour. The results of the theoretical modelling coincide well with the experimental EELS data.
  55. A Theoretical Study of the Carbocation Formation Energy Involved in the Isomerization of alpha-Pinene
    Norma Flores Holguín, Alfredo Aguilar Elguézabal, Luz María Rodríguez Valdez and Daniel Glossman Mitnik.
    Chemical Physics Letters 546 (2012) 168-170 F. I. 2.337
    α-Pinene isomerization starts with the formation of the pinanyl carbocation, which then undergoes rearrangement into two different isomers. One isomer yields monocyclic rings as final products, such as limonene, α-terpinene, and terpinolene while the other isomer yields bicyclic compounds, including camphene. In this Letter, a computational study is carried out in order to find the optimal temperature and solvent for the promotion of the second path considering that the bicyclical compounds are of greater economical interest. The energies of formation of the carbocations at different temperatures were calculated in vacuum and in solvents using the PBEPBE/6-31+G(d,p) model chemistry.
  56. Chitosan/poly(DL,lactide-co-glycolide) scaffolds for tissue engineering
    Martel-Estrada SA, Olivas-Armendáriz I, Martínez-Pérez CA, Hernández T, Acosta-Gómez EI, Chacón-Nava JG, Jiménez-Vega F, García-Casillas PE..
    Journal Of Materials Science-Materials In Medicine 23 (2012) 2893-2901 F. I. 2.316
    Chitosan/poly(DL-lactide-co-glycolide) (Ch/DL PLG) composite scaffolds were fabricated by freeze-drying lyophilization, and were evaluated and compared for use as a bone regeneration scaffold through measurements of the compression mechanical properties of the porous scaffolds. Also, In vitro cell culture of Sprague-Dawley rat's osteoblasts were used to evaluate the phenotype expression of cells in the scaffolds, characterizing the cellular adhesion, proliferation and alkaline phosphatase activity. The gene expression of osteocalcin, sialoprotein, alkaline phosphatase, Type I collagen and TGFβ1 were confirmed in the samples; moreover, it was confirmed, the mineralization by IR spectra and EDS analysis. Our results thus show that Ch/DL PLG scaffolds are suitable for biological applications.
  57. Synthesis, structure parameter and reaction pathway for spinel-type Co2SnO4
    J.A. Aguilar Martínez, M.I. Pech Canul, M. Esneider, A. Toxqui, S. Shaji.
    Materials Letters 78 (2012) 28-31 F. I. 2.307
    Co2SnO4 powders with the spinel structure were successfully obtained by the sol–gel method using Co(NO3)2·6H2O and SnCl4·5H2O as raw materials, followed by calcining at 900 and 1500 °C for 1 h. Characterization by XRD and SEM showed that at 900 °C, crystalline spinel accompanied by Co3O4 and SnO2 is obtained, while at 1500 °C homogeneous single-phase spinel powders are synthesized. Analysis by X-ray diffraction (XRD) aided by the refinement method of Rietveld allowed phase quantification and determination of the spinel lattice parameter (8.464 ± 0.005 Å). A reaction pathway is put forward based on a thermal analysis using simultaneous thermogravimetric analysis and differential scanning calorimetry (TGA/DSC). The proposed mechanism suggests that spinel is formed by the reaction between SnO2 (formed from SnCl4) and CoO which in its turn is produced during the decomposition reaction of Co3O4 into CoO and O2. Co3O4 on the other hand, is formed previously from Co(NO3)2.
  58. Characterization of Kevlar-29 fibers by tensile tests and nanoindentation
    J.A. Bencomo Cisneros, A. Tejeda Ochoa, J.A. García Estrada, C.A. Herrera Ramírez, A. Hurtado Macías, R. Martínez Sánchez, J.M. Herrera Ramírez.
    Journal of Alloys and Compounds 536 (2012) 456-459 F. I. 2.289
    Kevlar-29 fibers are being used in different applications due of their exceptional mechanical properties. More mechanical information on these fibers is needed for better understanding of their complex mechanical behavior. This article presents results from tensile tests on single Kevlar-29 filaments, to characterize their intrinsic behavior under quasi-static loading, and nanoindentation tests, to investigate their cross-section mechanical properties. The results reveal that the elastic modulus measured in the fiber cross-section is lower than that obtained in the longitudinal direction due to the high anisotropy of the fibers.
  59. Dielectric properties of Bismuth Titanate densified by Spark Plasma Sintering and Pressureless Sintering
    Joel O. Herrera Robles, Claudia A. Rodríguez González, Sebastián Díaz de la Torre, Luis E. Fuentes Cobas, Perla E. García Casillas, Héctor Camacho Montesa,.
    Journal of Alloys and Compounds 536 (2012) 511-515 F. I. 2.289
    Bismuth Titanate powder Bi4Ti3O12 of 175 nm mean particle size has been synthesized through chemical precipitation and calcination of chemical precursors at 700 °C. Ceramic pellets were sintered by conventional Pressureless Sintering (PLS) and Spark Plasma Sintering (SPS) techniques. SPS is shown to be effective in inhibiting grain growth and allowing the formation of a homogeneous microstructure. The optimum SPS temperature is 800 °C in less than 5 min. PLS specimens seem to be more sensible to temperature rise and sintering time, undergoing grain grow and plates-like morphology. This fact leads formation of a given crystallographic texture. Dielectric properties of SPS specimens are found dependent of the electric signal frequency and less sensitive to sintering temperature than PLS counterparts.
  60. Effect of carbon nanoparticles addition on the mechanical properties of an aluminum composite prepared by mechanical milling and leaching process
    I. Estrada Guel, C. Carreño Gallardo, R. Martínez Sánchez.
    Journal of Alloys and Compounds 536 (2012) 175-179 F. I. 2.289
    Aluminum (Al) based composites were produced by a solid state route using a high energy ball milling. Pure Al and mechanochemical processed graphite (C) powders were used as precursors. The C particles were prepared under different milling intensities and an additional chemical leaching process. Microscopy studies showed a uniform dispersion of the carbon nanoparticles into the aluminum matrix. A pronounced effect on the mechanical response of the specimens (smax, sy and hardness) was evident upon the addition of the C particles. An optimum value on the mechanical response was reached with small amounts of C complemented with medium milling intensities. This effect is believed to be caused by the homogeneous dispersion of the carbon particles into the matrix. Higher C contents cause both: particle agglomeration and saturation of the matrix, which decreases the mechanical properties of samples.
  61. Study of coherence strain of GP II zones in an aged aluminum composite
    J.L. Hernández-Rivera, J.J. Cruz Rivera, C.T. Koch, V.B. Özdöl, R. Martínez Sánchez.
    Journal of Alloys and Compounds 536 (2012) 159-164 F. I. 2.289
    Strain mapping using the geometric phase analysis (GPA) technique was applied to Al–GP II (Guinier–Preston) nanoscale precipitates, using both high resolution transmission electron microscopy (HRTEM) micrographs as well as the exit wave function (EWF) obtained by focal series reconstruction. The experimental strain results were compared with strain maps obtained from an atomic model which consisted of an Al supercell containing a GP II precipitate. It was built as a reference from literature data. The experimental results demonstrate a complex strain distribution and larger fluctuations than the reference strain maps. These differences were found to be partly a consequence of image artifacts produced by the technique as well as complex microstructural events which were present at the development stage studied.
  62. Synthesis, microstructural, optical and mechanical properties of yttria stabilized zirconia thin films
    P. Amézaga Madrid, F. Estrada Ortiz, W. Antúnez Flores, A. Hurtado Macías, P. Pizá Ruiz and M. Miki Yoshida. .
    Journal of Alloys and Compounds 536 (2012) 412-417 F. I. 2.289
    Thin films of yttria-stabilized zirconia (YSZ) exhibit exceptional properties, such as high thermal, chemical and mechanical stability. Here, we report the synthesis of YSZ thin films by aerosol assisted chemical vapour deposition onto borosilicate glass and fused silica substrates. Optimum deposition temperature was 673 ± 5 K. In addition, different Y content was tried to analyse its influence in the microstructure and properties of the films. The films were uniform, transparent and non-light scattering. Surface morphology and cross sectional microstructure were studied by field emission scanning electron microscopy. The microstructure of the films was characterized by grazing incidence X-ray diffraction. Crystallite size and lattice parameter were obtained. Optical properties were analysed from reflectance and transmittance spectra; from these measurements, optical constants and band gap were obtained. Quantum confinement effect, due to the small grain size of the films, was evident in the high band gap energy obtained. Nanoindentation tests were realized at room temperature employing the continuous stiffness measurement method, to determine the hardness and elastic modulus as a function of Y content.
  63. Wear behavior in Al2024–CNTs composites synthesized by mechanical alloying
    R. Pérez Bustamante, J.L.Bueno Escobedo, J.Jiménez Lobato, I.Estrada Guel, M. Miki Yoshida, L.Licea Jiménez, R. Martínez Sánchez.
    Journal of Alloys and Compounds 292-293 (2012) 169-175 F. I. 2.289
    The wear behavior of the 2024 aluminum alloy and its composites was evaluated through a pin-on-disk system. For this purpose the aluminum alloy was reinforced by carbon nanotubes dispersion produced by milling process. The nanotubes dispersion was carried out using a high energy mill for a fixed milling time. Milled powders were cold consolidated, sintered and then microstructurally and mechanically evaluated. The wear behavior of the alloy and its composites was evaluated considering the different nanotube contents under several abrasive conditions. The composites with higher nanotube concentration (5.0 wt%) displayed an improved wear resistance in all cases evaluated in this work.
  64. Characterization of Al2O3NP–Al2024 and AgCNP–Al2024 composites prepared by mechanical processing in a high energy ball mill
    C. Carreño Gallardo, I. Estrada Guel, M. Romero Romo, R. Cruz García, C. López Meléndez, R. Martínez Sánchez.
    Journal of Alloys and Compounds 536 (2012) 26-30 F. I. 2.289
    Mechanical alloying was used to produce two kinds of metal matrix composites based on 2024 aluminum alloy. The nanocomposites were reinforced with different percentages of Al2O3 and AgC nanoparticles. The content of nanoparticles has an important role on the mechanical properties of the nanocomposites. A milling time of 10 h is enough to form the Al2024 nanocomposites. The thermograms obtained by differential scanning calorimeter show the temperatures of phase precipitation, which were identified by X-ray diffraction. The results revealed that mechanical alloying is an excellent route for the incorporation and distribution of nanoparticles into Al2024.
  65. AA2024-CNTs composites by milling process after T6-temper condition
    R. Pérez Bustamante, M.J. González Ibarra, J. González Cantú, I. Estrada Guel, J. M. Herrera Ramírez, M. Miki Yoshida, R. Martínez Sánchez.
    Journal of Alloys and Compounds 536 (2012) 17-20 F. I. 2.289
    The 2024 aluminum alloy produced from elemental powders and reinforced by the addition of carbon nanotubes were microstructural and mechanically characterized. Composites were synthesized through milling process followed by cold consolidation, sintering and hot extrusion. The effect of the nanotubes on the microstructure and mechanical properties were analyzed in the composites after T6 thermal treatment. Al4C3 formation was due to the reaction of carbon nanotubes and Al matrix. Precipitated Al–Cu phase coexists and presents interaction with crystallized carbide and dispersed nanotubes. There is a direct relationship of carbon nanotubes content and hardness answer.
  66. Electrophoretic Impregnation/Deposition Complemented with Polymeric Templating for the Fabrication of Functionalized-Porosity Layered-Ceramics: a Solid-Oxide-Fuel-Cells Approach.
    Mayen-Mondragón, R (Mayen-Mondragón, Rodrigo)1; Falk, G (Falk, Guido)1; Clasen, R (Clasen, Rolf)1.
    Journal Of The American Ceramic Society 95 (2012) 593-599 F. I. 2.272
    A simple, economical, and environmentally compatible methodology for the fabrication of layered ceramics is presented herein. Water-based electrophoretic techniques and polymeric templating were combined to fabricate graded-porosity ceramic foams with controlled pore size, pore geometry, and excellent pore connectivity. Dense ceramic films can be laid either on top of the porous ceramic or in a sandwich-style configuration. A single fabrication step suffices when working a single material (or material composition). Else, two or more fabrication steps are required. The two-step manufacture of a half solid-oxide-fuel-cell is presented. The yttria-stabilized zirconia (8YSZ) solid electrolyte layer was deposited on top of the templated graded-porosity nickel-oxide/8YSZ electrode. The present methodology promises alternatives to current fabrication processes.
  67. Enhanced layerwise model for laminates with imperfect interfaces - Part 1: Equations and theoretical validation
    Álvarez-Lima R, Díaz- Díaz A., Carón JF, Chataigner S.
    Composite Structures 94 (2012) 1694-1702 F. I. 2.24
    The aim of this paper is the enhancement and validation of a layerwisemodel applied to the analysis of laminates with thin layers of an elastic–plastic adhesive. The thin adhesive layers are modelled as imperfectinterfaces across which displacement discontinuities exist. In a previous paper, the constitutive equations of the imperfectinterfaces were empirically established without following the layerwise logic. The modelequations are revisited and a solid theoretical justification of the new enhancedequations is obtained by making use of the Hellinger–Reissner functional. A theoreticalvalidation of the model is performed by comparing its predictions to those of a solid finite element resolution in the case of a T-peel joint. The results of the enhanced version of the model are very accurate whereas those of the previous version are erratic for the considered joint. As compared to the solid finite element method, an important saving in computational cost is achieved.
  68. Enhanced layerwise model for laminates with imperfect interfaces - Part 2: Experimental validation and failure prediction
    Mendoza-Navarro LE, Díaz- Díaz A, Carón JF, Chataigner S.
    Composite Structures 94 (2012) 1032-1037 F. I. 2.24
    n this paper, the layerwise model for laminates with imperfect interfaces and enhanced in Part 1 of this work is confronted with experimental results. The model calculations are validated by comparing its sliding predictions in double lap adhesive joints to the sliding measurements performed in a previous paper. The model predictions agree with the experimental results. Finally, the model is applied to the failure analysis in double lap joints and T-peel joints exhibiting adherend, adhesive and cohesive failures. The model calculations and pertinent failure criteria provide accurate predictions and may become a helpful tool suitable to the design of adhesive joints.
  69. Structural and morphological study of a 2024 Al–Al2O3 composite produced by mechanical alloying in high energy mill
    J.L. Hernández Riveraa, , , J.J. Cruz Riverab, V. Paz del Ángelc, V. Garibay Feblesc, O. Coreño Alonsod, R. Martínez-Sáncheza.
    Materials & Design 37 (2012) 96-101 F. I. 2.2
    2024 Al composite reinforced with Al2O3 particles was obtained by mechanical alloying (MA) using Al, Cu and Mg elemental powders as raw materials and Al2O3 nanoparticles as reinforcement. The results shown that as the MA time increased, the non-reinforced (WR) and Al2O3 reinforced powders (R1A and R2A) morphology changed from flake-flattened to equiaxed. Regarding the average particle size, WR group displayed a continuous decreasing value even for a processing time of 10 h while R2A and R1A groups shown a constant value for the same time. This led to the conclusion that steady state of the process was reached in shorter times in presence of Al2O3 nanoparticles. It was found that the reinforcement was present in the matrix like isolated particles and small agglomerates which affected the dislocation motion, and it was assumed that this fact caused the increase observed in the microhardness values. There was no evidence of new phase precipitation through MA process.
  70. Uranium-seriesisotopestransport in surface, vadose and groundwaters at SanMarcosuraniumbearingbasin, Chihuahua, Mexico
    Juan Carlos Burillo Montúfar a, Manuel Reyes Cortés a, b, Ignacio Alfonso Reyes Cortés b, Ma. Socorro Espino Valdez b, Octavio Raúl Hinojosa de la Garza a, Diana Pamela Nevárez Ronquillo a, Eduardo Herrera Peraza a, Marusia Rentería Villalobos a, María Elena Montero Cabrera a,.
    Applied Geochemistry 27 (2012) 1111–1122 F. I. 2.176
    In the U deposit area at San Marcos in Chihuahua, Mexico, hydrogeological and climatic conditions are very similar to the Nopal I, Peña Blanca U deposit, 50 km away. The physicochemical parameters and activity concentrations of several 238U-series isotopes have been determined in surface, vadose and ground waters at San Marcos. The application of some published models to activity ratios of these isotopes has allowed assessing the order of magnitude of transport parameters in the area. Resulting retardation factors in San Marcos area are Rf238 ≈ 250–14,000 for the unsaturated zone and ≈110–1100 for the saturated zone. The results confirm that the mobility of U in San Marcos is also similar to that of the Nopal I U deposit and this area can be considered as a natural analog of areas suitable for geologic repositories of high-level nuclear waste.
  71. Piezoelectric control of the magnetic anisotropy via interface strain coupling in a composite multiferroic structure
    Chenglong Jia, Alexander Sukhov, Paul P. Horley and Jamal Berakdar.
    EPL 99 (2012) doi:10.1209/0295-5075/99/17004 F. I. 2.171
    We investigate theoretically the magnetic dynamics in a ferroelectric/ferromagnetic heterostructure mediated by a strain-induced magnetoelectric interaction. The epitaxial strain involves a strong piezoelectricity and interfacial magnetoelastic coupling, the interplay of both gives rise to an electrically tunable uniaxial magnetic anisotropy. We predict an electric-field–induced magnetic switching in the plane perpendicular to the magneto-crystalline easy axis while the total magnetization remains stable. We trace this effect back to the ferroelectric control of the magnetic anisotropy. We also inspect the magnetic remanence and the electric coercivity and demonstrate a pronounced dynamic magnetic response to an electric field in a thin ferromagnetic layer.
  72. Multiferroic response of nanocrystalline lithium niobate
    Carlos Díaz-Moreno, Rurik Farías, Abel Hurtado-Macías, José Elizalde-Galindo, Juan Hernández-Paz.
    Journal of Applied Physics 111 (2012) 7 F. I. 2.168
    In this research work the multiferroic nature of nanocrystalline lithium niobate (NLN) was investigated. The NLN samples were prepared by mechanochemical alloying followed by calcination; after that, the samples were annealed in Ar-5% H atmosphere in order to generate oxygen vacancies in the surface of the nanoparticles. X-ray diffraction (XRD) spectrum showed the formation of a single crystalline phase of LN with an average size of 25 nm. This was confirmed by high-resolution transmission electron microscopy (HRTEM). Ferroelectric hysteresis loop measurements showed a maximum polarization of Ps = 0.21 μC/mm2, remnant polarization Pr = 0.11 μC/mm2 and coercive field Ec = 5.1 kV/cm. Ferromagnetic measurements showed a magnetic remanence of Mr = 0.35 × 10−3 emu/g and a coercive field of HC = 0.75 kOe. Thus, confirming the multiferroic nature of nanometer-scale particles of LN.
  73. Comparison of electrical and electro-optical characteristics of light-emitting capacitors based on silicon-rich Si-oxide fabricated by plasma-enhanced chemical vapor deposition and ion implantation
    A A González-Fernández, J Juvert, A Morales-Sánchez, J Barreto, M Aceves, and C Domínguez.
    Journal of Applied Physics 111 (2012) doi.10.1063/1.3692082 (9 pages) F. I. 2.168
    This work presents electrical and electro-optical studies performed on light-emitting capacitors with silicon-rich silicon oxide fabricated by plasma-enhanced chemical vapor deposition and by the implantation of Si ions in thermally grown SiO2. The influence of the fabrication technique and silicon content on electrical, electro-optical, and emission spectra characteristics has been studied. Results on the electrical behavior show a significant dependence on both the fabrication technique and Si content that translates in variations on electroluminescence with fabrication technique and silicon excess.
  74. Comprehensive characterization of thermophysical properties in solids using thermal impedance
    Martinez-Flores, JJ ; Licea-Jimenez, L ; Pérez-Garcia S.A. ; Rodriguez-Viejo, J ; Alvarez-Quintana, J.
    Journal of Applied Physics 112 (2012) doi: 10.1063/1.4759434 F. I. 2.168
    Thermal impedance Zth(iω) is a way of defining the thermophysical characteristics and behavior of thermal systems. Existing photoacoustic and photothermal approaches based on thermal impedance formalism merely allows a partial thermal characterization of the materials (generally, either thermal diffusivity or thermal effusivity). In this work, a new approach based on the thermal impedance concept in terms of its characteristic thermal time constant is developed from thermal quadrupoles formalism. The approach outlined in this contribution presents a set of analytical equations in which through a single measurement of thermal impedance is sufficient to obtain a comprehensive characterization of the thermophysical properties of solid materials in a simple way.
  75. Critical magnetic fields in the rutheno-cuprates Ru(1-x)NbxSr2Eu1.4Ce0.6Cu2O10
    M. E. Botello-Zubiate, J. A. Matutes-Aquino, O. E. Ayala-Valenzuela, and M. Jaime.
    Journal of Applied Physics 111 (2012) doi: 10.1063/1.3676418 F. I. 2.168
    II-type superconducting rutheno-cuprates are both interesting and challenging systems where there is a coexistence of superconductivity and magnetism, so far poorly understood. The magnetic transitions that occur before the superconducting transition in Ru-1212 are simpler and better understood than those found in Ru-1222. In this work, polycrystalline Ru(1-x)NbxSr2Eu1.4Ce0.6Cu2O10 samples (Ru-1222) with x = 0, 0.2, 0.4, and 0.6, were prepared by conventional solid state reaction using stoichiometric amounts of high purity oxide powders: RuO2, Nb2O5, SrCO3, Eu2O3, CeO2, and CuO. The phases were identified by x-ray diffraction. From electrical resistance measurements as a function of the applied magnetic field at different temperatures (4 to 40 K), the H-c2 critical field or a lower limit of this was determined for each composition. At the lower measurement temperatures, from T = 4 K to T = 20 K, it was only possible to set a lower limit for the critical magnetic field, H-c2, of 140 kOe for compositions x = 0 and 0.2, while for compositions x = 0.4 and 0.6 the critical magnetic field, H-c2, were 110 and 84 kOe, respectively at T = 4 K. The dependence of these critical magnetic fields, H-c2, with temperature and composition is discussed.
  76. Magnetocaloric effect in Sm-Co2-xFex alloys
    Burrola Gándara, LA (Burrola-Gandara, L. A.)1; Grijalva-Castillo, MC (Grijalva-Castillo, M. C.)1; Santillán Rodríguez, CR (Santillan-Rodriguez, C. R.)1; Matutes-Aquino, JA (Matutes-Aquino, J. A.)1.
    Journal of Applied Physics 111 (2012) doi: 10.1063/1.3679392 F. I. 2.168
    SmCo2 and SmFe2 magnetic cubic Laves phases have Curie temperatures of 220 and 669 K, respectively. Aiming to increase the Curie temperature of SmCo2 for potential room temperature magnetic refrigeration Co was partially replaced by Fe. The fundamental magnetic entropy change of the SmCo2 compound, Delta S-M = 3.61 J/kg.K, for an applied magnetic field of mu H-o = 1.5 T was observed at T-SR = 175 K, where a spin reorientation transition occurs; furthermore a refrigerant capacity of 37 J/kg was calculated. Interestingly the addition of Fe practically suppressed the spin reorientation transition, shifting the magnetic entropy change maximum to the Curie temperature in the SmCo1.8Fe0.2 sample. The magnetic entropy change maximum at Curie temperature T-C = 300 K and the refrigerant capacity for the doped compound decreased to Delta S-M = 0.20 J/kg.K and 13.5 J/kg, respectively, for an applied magnetic field of mu H-o = 1.5 T. After an homogenization heat treatment at 773 K during 50 h, the SmCo1.8Fe0.2 compound showed an increase of the maximum magnetic entropy change, Delta S-M = 0.28 J/kg.K, and the refrigerant capacity remains 13.5 J/kg, for an applied magnetic field of mu H-o = 1.5 T.
  77. Mass transport and thermal stability of TiN/Al2O3/InGaAs nanofilmas
    O. Ceballos Sánchez, A. Sánchez Martínez, M.O. Vázquez Lepe, T. Duong, R. Arroyave, F. Espinosa Magaña and A. Herrera Gómez.
    Journal of Applied Physics 112 (2012) F. I. 2.168
    The structure of TiN/Al2O3 nanofilms grown on InxGa1-xAs substrates was studied with angle-resolved x-ray photoelectron spectroscopy (ARXPS), high resolution transmission electron microscopy (HRTEM), and density functional theory calculations. From the ARXPS studies, it was possible to characterize in detail the composition and distribution of the various layers constituting the nanofilms; the results were consistent with HRTEM micrographs. The analysis of the ARXPS data showed that annealing causes diffusion of indium atoms from the substrate into the titanium layer. It also allowed for establishing that the thickness and composition of the dielectric layers remain stable under thermal treatments.
  78. Temperature effect on dipolar and exchange interactions for SmCo51Fe65Co35 nanocomposite powders
    Ortega, LPM (Muñoz Ortega, L. P.)1; Galindo, JTE (Elizalde Galindo, J. T.)1; Mancilla, JRF (Farías Mancilla, J. R.)1; Santillán, CR (Santillán, C. R.)2; Aquino, JAM (Matutes Aquino, J. A.)2.
    Journal of Applied Physics 111 (2012) doi: 10.1063/1.3672070 F. I. 2.168
    DC magnetization measurements were used to determine the temperature dependencies of the magnetic properties for (90% wt) SmCo5+(10% wt)Fe65Co35 nanocomposite powders synthesized by mechanical milling and subsequent annealing. The annealing conditions were T equal to 1073 K and time, t, equal to 1.5, 3.0, 4.5, 6.0 min. Maximum magnetization decreased upon cooling in temperature range from 290 to 10 K. Coercivity increased its value to a maximum at the lowest temperature. On the other hand, hysteresis loops collected at low temperatures showed a knee in the second quadrant of the demagnetization curve, which suggests that dipolar interactions are becoming stronger than intergrain exchange coupling as temperature is lowered. This low temperature reduction of exchange interactions is confirmed by the temperature dependence of the exchange coupled volume ratio, R. Finally, the temperature effect on magnetic properties is explained on the basis of anisotropy enhancement and reduction of thermal fluctuations as temperature decreases.
  79. Temperature induced conversion from surface to “bulk” sites in Eu3+-impregnated CeO2 nanocrystals
    Carmen Tiseanu, Vasile I. Parvulescu, Margarita Sánchez Domínguez and Magali Boutonnet.
    Journal of Applied Physics 112 (2012) F. I. 2.168
    Evolution with calcination temperature of Eu3+ sites in CeO2 nanocrystals is investigated by time-resolved photoluminescence spectroscopy. In the as-synthesized Eu3+ impregnated CeO2, most of Eu3+ ions reside on surface (S) sites. The Eu3+emission in S sites is broad and short-lived (τ = 240 μs) being dominated by the electric dipole (ED) 5D0-7F2 emission with little evidence for clustering. After calcination (between 500 and 1300 °C), Eu3+ is distributed on surface, cubic and up to three additional crystalline sites. Surface type emission could be detected until 1100 °C. In cubic sites, Eu3 substitute for the lattice Ce4+ with Oh symmetry (O sites). The emission of Eu3+ in O sites is characterized by relative long-lived (τ = 1.8–2 ms) and ultra-narrow (FWHM = 7 cm−1) magnetic dipole (MD) 5D0-7F1 emission centered at ∼591 nm. Three more crystalline sites are attributed to the oxygen vacancy charge-compensated defects: trigonal with C3v symmetry (C1 sites) and C2 and C3 sites with C2v or lower symmetry. Eu3+ in C1 sites exhibits predominant ED 5D0-7F2 emission centered at ∼610 and 632 nm with lifetime of 0.85–1 ms. The C1 sites are assigned to Eu3+-(oxygen vacancy)-associated cubic sites. The O2− to Ce4+ electronic charge-transfer band sensitizes preferentially the Eu3+ emission in O and, to a less extent, C1 sites but not the S sites. Overall, the results show that the oxygen vacancies are distributed around both Eu3+ and Ce4+ and the Eu3+-oxygen vacancy interaction mode as nearest-neighbour or next-nearest-neighbour depends on the calcination temperature.
  80. Structural stability and cation disorder in Aurivillius phases
    M. García Guaderrama, L. Fuentes, A. Márquez Lucero, O. Blanco.
    Materials Research Bulletin 47 (2012) 3850–3854 F. I. 2.105
    A model to determine the structural stability and cation configuration of Aurivillius phases is presented. Structural stress caused by elastic coupling between the (M2O2) and (An−1BnO3n+1) substructures that form the phase and the electrostatic attraction forces between them are considered. The model suggests that the cation exchanges observed in these substructures result from a balance between the cohesive electrostatic energy and the disruptive elastic coupling energy. The model explains and predicts the cation configuration of Aurivillius phases of type (Bi2−xPbxO2)(PbyBi1−y)n−1BnO3n+1, where the cation exchange between M and A sites is of Bi3+ ↔ Pb2+ type. The PbBi2Nb2O9 phase is taken as a case study. This material has been studied quantifying this cation exchange and several theoretical models have been developed to explain the phenomenon. The cation equilibrium configuration determined by the present model is much more accurate than previous studies. Furthermore, a precise explanation of this phenomenon is provided.
  81. Influence of mesoporous substrate morphology on the structural, optical and electrical properties of RF sputtered ZnO layer deposited over porous silicon nanostructure
    Kumar, Y (Kumar, Yogas)1,3; García, JE (Escorcia García, J.)1; Singh, F (Singh, Fouran)2; Olive-Méndez, SF (Olive-Méndez, S. F.)3; Sivakumar, VV (Sivakumar, V. V.)2; Kanjilal, D (Kanjilal, D.)2; Agarwal, V (Agarwal, V.)1.
    Applied Surface Science 258 (2012) 2283-2288 F. I. 2.103
    Morphological, optical and transport characteristics of the RF sputtered zinc oxide (ZnO) thin films over the mesoporous silicon (PS) substrates have been studied. Effect of substrate porosity on the grain growth and transport properties of ZnO has been analyzed. Physical and optical properties of ZnO-PS structures were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), atomic force microscopy (AFM), and photoluminescence (PL) spectroscopy. Our experimental results indicate that on changing porosity of the PS substrates, regularity of the spatial distribution of the ZnO nanocrystallites can be controlled. While the morphology and grain size of ZnO depended strongly on the morphology and pore size of the PS substrates, the rectifying factors of the metal semiconductor junction were found to be different by a factor of 3. The deposition of semiconducting oxides on such mesoporous sub-strates/templates offers the possibility to control their properties and amplify their sensing response.
  82. High Temperature Thermal Barrier Coatings from Recycled Fly Ash Cenospheres
    A. Arizmendi Morquecho , A. Chávez Valdez , J. Álvarez Quintana, .
    Applied Thermal Engineering 48 (2012) 117–121 F. I. 2.06
    The high temperature behavior of electrophoretically deposited thermal barrier coatings based on recycled fly ash cenospheres is presented. Thermal properties such as thermal expansion coefficient, specific heat, thermal conductivity, thermal diffusivity and thermal effusivity of fly ash (FA) and fly-ash cenospheres (FAC) were measured in the temperature range of 373 K–1173 K. Thermal conductivity values as low as 0.17 W/m K and 0.32 W/m K for FAC and FA respectively at 1200 K were found. These results confirm their potentiality as ultra-low thermal conductivity thermal insulators for high temperature applications.
  83. Structural study of molybdenum(VI) complexes containing bidentate ligands: Synthesis, characterization and DFT calculations
    Raúl Colorado-Peralta Mario Sanchez-Vazquez Irán F. Hernández-Ahuactzi Sonia A. Sánchez-Ruiz Rosalinda Contreras Angelina Flores-Parra Silvia E. Castillo-Blum.
    Polyhedron 48 (2012) 72-79 F. I. 2.057
    A series of molybdenum(VI) complexes containing bidentate ligands: toluene-3,4-dithiol (1), 2-mercaptophenol (2), 2-aminothiophenol (3), ethane-1,2-dithiol (4), dithiooxamide (5) and 2-thiopheno-carboxamide (6) are reported. The hexacoordinated molybdenum tris-chelates compounds: tris-(toluene-3,4-dithiolate)molybdenum(VI) (7), tris-(2-mercaptophenolate)molybdenum(VI) (8), tris-(2-aminothiophenolate)molybdenum(VI) (9), tris-(ethane-1,2-dithiolate)molybdenum(VI) (10), and the bis-chelates, which also contain coordinated oxo ligands: bis-(dithiooxamidate)dioxomolybdenum(VI) (11) and bis-(2-thiopheno-carboxamide)dioxomolybdenum(VI) (12), were characterized by 1H and 13C NMR and IR spectroscopies, as well as elemental analyses and mass spectrometry. The structures of minimum energy of the coordination compounds were calculated using DFT (B3LYP/def2-TZVPP). Solid state structures of analogous compounds, as well as calculations indicated that the minimum energy structures correspond to those of trigonal prismatic geometry.
  84. Growth of Aligned ZnO Nanorods on Transparent Electrodes by Hybrid Methods
    Meléndrez, MF (Meléndrez, M. F.)1; Hanks, K (Hanks, K.)2; Leonard-Deepak, F (Leonard-Deepak, Francis)3; Solís-Pomar, F (Solís-Pomar, F.)4; Martínez-Guerra, E (Martínez-Guerra, E.)5; Pérez-Tijerina, E (Pérez-Tijerina, E.)4; José- Yacaman, M (José- Yacaman, M.)2.
    Journal of Materials Science 47 (2012) 2025-2032 F. I. 2.015
    The fabrication of ZnO (80 nm) thin film was achieved by hybrid atomic layer deposition (ALD) to prevent the reaction between the reactants and conductive layer of the substrates. ZnO nanorods (ZnO-NRs) growth over the substrates was performed by wet chemical procedure in which Zn(NO(3))(2) and hexamethylenetetramine were used as the precursors. HR-TEM, SAED, FE-SEM, X-ray diffraction (XRD), and UV-Vis spectroscopy were employed to characterize the ZnO-NRs samples on the substrates. XRD and HR-TEM analyses confirmed that the ZnO nanorod structure is hexagonal wurtzite type with growth in the [0001] direction. Length and thickness of the ZnO-NRs ranged between 45 and 90 nm and 480 and 600 nm, respectively. It was observed that the growth rate of NRs in [0001] direction is 10 times higher than in [1000] direction. The growth mechanism and resulted dimensions of nanorods are function of the synthesis parameters (in hybrid ALD process) such as reaction time, temperature, precursor molar ratio, and thickness of ZnO film.
  85. Synthesis, crystal stability, and electrical behaviors of La0.7Sr0.3Cr0.4Mn0.6O3−δ–XCu0.75Ni0.25 for its possible application as SOFC anode
    J. Alvarado Flores M. H. Bocanegra Bernal, I. Espitia Cabrera, E. Torres Moye, A. Reyes Rojas.
    Journal of Materials Science 47 (2012) 8118-8127 F. I. 2.015
    La0.7Sr0.3Cr0.4Mn0.6O3-d (perovskite-type) nanocomposites impregnated with Cu0.75Ni0.25 have been synthesized by sol–gel method. Crystal structure of LSCM–Cu0.75Ni0.25 composites were refined by the Rietveld method. Crystal symmetry of CuO and NiO nanoparticles have monoclinic C12=c and cubic Fm3 m
    symmetry, respectively, but after sintering at 1,200 C and reducing the temperature to 600 C, it’s transformed into a new Cu0.75Ni0.25 intermetallic solid solution without secondary phase. We have detected a cationic inter-diffusion in Cu $ Ni interphase crystals during this reduction process; however, when sintering time exceeds 2 h at 1,200 C this reaction mechanism is interrupted by a sublimation phenomenon; which causes Cu2O cubic structure segregation from monoclinic CuO structure. This leads to Cu precipitation from the Cu1-xNix solid solution. Cu0.75Ni0.25 inhibits the LSCM perovskite-type grain growth (t & 220 nm). Electrical conductivity indicates the presence of semiconductor and metallic-type behaviors with a maximum electrical conductivity (800 C)[4.5 (log r, Sm cm -1 ). When Cu0.75Ni0.25 concentration was 25 and 35 %, semiconductor behavior were dominated. Thermal
    expansion coefficients showed a linear dependence inversely proportional to Cu0.75Ni0.25 concentration. Electrical conductivity, Rietveld analysis, Porosity, TEC, and Ea behaviors lead to the conclusion that the anodes between 25 and 35 % (Cu0.75Ni0.25) are closer to applications at SOFC.
  86. Enhancement of photoluminescence due to erbium-doped in CdS thin films
    Zelaya-Ángel, O; Tomas, SA ; Rodríguez, P ; Mendoza-Álvarez, JG; Lozada-Morales, R; Portillo-Moreno, O; González-Hernández, J..
    Journal o f Materials Science 47 (2012) 479-485 F. I. 2.015
    Cadmium sulfide (CdS) thin films were synthesized by chemical bath deposition on glass substrates at 80 A degrees C. The CdS thin films were doped with erbium (Er(3+)) during the growth process by adding aqueous solutions of Er(NO(3))(3)center dot 3H(2)O to the CdS chemical bath. The relative volume (V (r)) of the doping-solution was varied to obtain ten different doping levels. X-ray diffraction patterns displayed the zincblende crystalline structure for all the CdS:Er samples, with a remarked preferred orientation along the (111) direction. The (111) interplanar distance (ID) first decreased, reaching a minimum value at V (r) = 3%, after which point it increased up to saturation for largest values of V (r). The dependence of the band-gap energy (E (g)) on V (r) followed an opposite behavior to that described by the ID. The photoluminescence (PL) spectra showed essentially two main bands: the green emission (GE) band of CdS and a red emission (RE) band. The increasing of the PL signal, for V (r) a parts per thousand currency sign 4% has been associated with the presence of Er(3+) into the CdS lattice. For V (r) > 4%, Er degrades the lattice. In addition, the crystalline quality (CQ) and PL of the material improved for low V (r) values, which was in agreement with measurements of the mobility.
  87. [2]pseudorotaxanes derived from 27-and 29-membered oxaazacyclophanes and 1,2-bis(benzimidazolium)ethane salts
    Reyes-Marquez, V (Reyes-Marquez, Viviana)1; Tiburcio, J (Tiburcio, Jorge)2; Hopfl, H (Hoepfl, Herbert)3; Sanchez-Vazquez, M (Sanchez-Vazquez, Mario)4; Hernandez-Ahuactzi, IF (Hernandez-Ahuactzi, Iran F.)4; Moreno-Corral, R (Moreno-Corral, Ramon)1; Lara, KO (Lara, Karen O.)1.
    Journal Of Physical Organic Chemistry 25 (2012) 1042-1052 F. I. 1.963
    Four novel 27- and 29-membered oxaazacyclophanes were synthetized via the high dilution method in moderate to good yields, employing aromatic dialdehydes and diamines as precursors to generate first the corresponding cyclic Schiff bases, which were then reduced in almost quantitatively yields to the corresponding macrocyclic diamines. All compounds were characterized by conventional techniques such as IR and NMR (H-1, C-13) spectroscopy, elemental analysis, and mass spectrometry. Besides, two macrocycles were studied by single-crystal X-ray diffraction analysis, which revealed that their cavities are appropriate to include small molecules. Using two representative oxaazacyclophanes (OX-3 and OX-4) as wheels and 1,2-bis(benzimidazolium)ethane salts as axles, [2]pseudorotaxanes were formed in 1:1 (v/v) solvent mixtures of CHCl3 and MeCN and studied by H-1 NMR and ultraviolet/visible (UV/Vis) spectroscopy, and electrospray ionization-time-of-flight mass spectrometry, finding in all cases the formation of stable 1:1 complexes. The binding constants of the complexes were determined by UV/Vis and H-1 NMR titration experiments, giving values ranging from 0.52 x 10(3) to 4.6 x 10(3) M-1. Likely, complex structures were investigated in the gas-phase using density functional theory calculations at the B3LYP/6-31G(d) level of theory. The complexation experiments together with the results from the molecular modeling studies indicate that dicationic axles can penetrate the cavity of the oxaazacyclophanes synthesized herein to give a new family of [2]pseudorotaxanes. These supramolecular structures are held together by pi-pi stacking interactions (charge-transfer), charge-assisted hydrogen bonds, and ion dipole forces.
  88. P-type thin films transistors with solution-deposited lead sulfide films as semiconductor
    A. Carrillo-Castilloa, A. Salas-Villasenora, I. Mejiaa, S. Aguirre-Tostadob, B.E. Gnadea, M.A. Quevedo-Lópeza.
    Thin Solid Films 520 (2012) 3107-3110 F. I. 1.89
    n this paper we demonstrate p-type thin film transistors fabricated with lead sulfide (PbS) as semiconductor deposited by chemical bath deposition methods. Crystallinity and morphology of the resulting PbS films were characterized using X-ray diffraction, atomic force microscopy and scanning electron microscopy. Devices were fabricated using photolithographic processes in a bottom gate configuration with Au as source and drain top contacts. Field effect mobility for as-fabricated devices was ~ 0.09 cm2 V− 1 s− 1 whereas the mobility for devices annealed at 150 °C/h in forming gas increased up to ~ 0.14 cm2 V− 1 s− 1. Besides the thermal annealing, the entire fabrications process was maintained below 100 °C. The electrical performance of the PbS-thin film transistors was studied before and after the 150 °C anneal as well as a function of the PbS active layer thicknesses.
  89. Friction and wear properties of poly(methyl methacrylate)-hydroxyapatite hybrid coating on UHMWPE substrates
    C.H. Navarro a, K.J. Moreno a, A. Chávez-Valdez b,
    F. Louvier-Hernández a, J.S. García-Miranda a, R. Lesso a, A. Arizmendi-Morquecho,.
    Wear 282 (2012) 282-283 F. I. 1.872
    Poly(methyl methacrylate)–hydroxyapatite (PMMA/HA) composite has been successfully prepared for its application as coating on ultra high molecular weight polyethylene (UHMWPE). The hybridcoating was prepared by mixing PMMA obtained from methyl methacrylate (MMA) polymerization and medical grade hydroxyapatite (HA). FTIR technique was used to study the PMMA synthesis and hybrid composite coating. For comparative studies, pure PMMA coatings were also prepared in order to determine the influence of HA incorporation into PMMA matrix. The coating thickness was determined using image analysis software and increased from 32.61 μm to 34.01 μm when HA was added. The surface morphology of the coatings was characterized by Scanning Electron Microscopy (SEM). The wear tests for PMMA/HA and PMMA coatings on UHMWPE were carried out on a pin-on-disk tribometer in dry conditions with normal loads ranging from 2 to 10 N. The wear performance of PMMA coatings was improved by HA additions, obtaining lower friction coefficients and volume loss for PMMA/HA coatings than the corresponding values for PMMA coating under 10 N load.
  90. Measurement of Mechanical Properties of a Novel Electroless Ni-B Coating using Nanoindentation
    Abel Hurtado Macías; Carlos Domínguez; Roal Torres; Manuel Ramos; Jesús González Hernández.
    Surface & Coatings Technology 51 (2012) 7762–7768 F. I. 1.867
    Structure and mechanical properties of electroless nickel-boride (Ni–B) thin film coatings on S7 steel substrate were studied in as-plated and annealed samples. The electroless bath does not contain Pb, Cd, or Ta in the stabilizer agents. The mechanical properties of the Ni–B coatings were obtained from nanoindentation measurements. Models by Korsusky and King were used to obtain hardness and elastic modulus, respectively. The structure of the coatings was observed by atomic force and scanning electron microscopy and XRD. Bath composition, plating time, annealing temperature, and time were considered in order to prepare coatings with optimal mechanical properties.
  91. Improving polyaniline processability by grafting acrylic copolymer
    Elcin Coskun, Shaida Marisol Martínez-Ramírez, Wilber Antúnez-Flores, Claudia Alejandra Hernández-Escobar, Erasto Armando Zaragoza-Contreras.
    Synthetic Metals 162 (2012) 344-351 F. I. 1.829
    n this study styrenesulfonate of polyaniline/acrylic copolymers were synthesized via free radical polymerization through polymerization in dispersed medium. The resulting materials were applied onto glass-ITO slides using the air-brushing technique to obtain PAni based thin films. Analyses by scanning electron microscopy in TEM mode (STEM) indicated that depending on the acrylic monomer combination (methyl methacrylate, methacrylic acid or butyl acrylate) the adhesion on the substrate was better than styrenesulfonate of polyaniline (PAni–SSA) homopolymer. The effect of the combination of the acrylic monomers on the electrical properties was determined by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Results indicated that the electrical properties of the acrylic copolymer could be enhanced by varying the glass transition temperature. From these findings it was concluded that the inclusion of butyl acrylate in the copolymer was the critical condition to improve adhesion and electrical properties.
  92. Ab initio study of electron transport in 4-(3-nitro-4-tetrafluorophenylthiolate-ethynyl, phenylethynyl) benzenethiolate
    Serrato-Villegas, L (Serrato-Villegas, Lilia)2; Gallo, M (Gallo, Marco)1; Delgado-Ríos, M (Delgado-Ríos, Marcos)3; Romero, MT (Teresa Romero, María)4; Glossman-Mitnik, D (Glossman-Mitnik, Daniel)5.
    Journal of Molecular Modeling 18 (2012) 611-621 F. I. 1.797
    The electron transport of the 4-(3-nitro-4-tetrafluorophenylthiolate-ethynyl, phenylethynyl) benzenethiolate (S-FNPPB-o) molecule assembled in two Au (111) electrodes, was studied using two approaches: in the first approximate approach an electric field was applied to the pure molecule attached to two thiolate ends fixed, and in the second approach we used the nonequilibrium GreenA ' s function formalism (NEGF) coupled to DFT to calculate the I-V curve and the voltage dependence of the transmission function in the extended system, molecule plus electrodes. By applying an electric field to the pure molecule plus thiolate ends fixed, and visualizing the changes in the spatial distribution of the frontier molecular orbitals, we can expect based on the continuity of the conduction pathway in electron transport, that if electron transport occurs through the frontier orbitals, only the LUMO orbital would create an open channel for electron transport due to its delocalized nature and large orbital density at the thiolate groups. The NEGF calculations indicate that at applied voltages lower than +/- 0.8 V, the current is related to transmission values through the tails of the broad LUMO orbital, and since this orbital is the one closer to the Fermi energy, and we observed very low current values in this region, higher current values at positive bias than at negative bias. As the voltage exceeds +/- 0.8 V the current increases from the contribution of more states from the broadened part of the transmission function from the LUMO orbital, and when the voltage approaches +/- 2 V, the LUMO + 1 orbital enters into the bias window and the current increases again.
  93. Computational Simulation of the Molecular Structure and Properties of Dye-7 for Organic Photovoltaics
    Jesús Baldenebro-López, José Castorena-González, Norma Flores Holguín, Joel Calderón-Guillén and Daniel Glossman-Mitnik.
    Journal of Molecular Modeling 18 (2012) 835-842 F. I. 1.797
    Organic dyes have great potential for its use in solar cells. In this recent work, the molecular structure and properties of Dye 7 were obtained using density functional theory (DFT) and different levels of calculation. Upon comparing the molecular structure and the ultraviolet visible spectrum with experimental data reported in the literature, it was found that the M05-2X/6-31G(d) level of calculation gave the best approximation. Once the appropriate methodology had been obtained, the molecule was characterized by obtaining the infrared spectrum, dipole moment, total energy, isotropic polarizability, molecular orbital energies, free energy of solvation in different solvents, and the chemical reactivity sites using the condensed Fukui functions.
  94. DFT Study of the Interaction Between the Conjugated Fluorescein and DABCYL System, Using Fluorescence Quenching Method
    Mónica Alvarado González, Marco Gallo, Pablo López Albarrán, Norma Flores Holguín and Daniel Glossman Mitnik.
    Journal of Molecular Modeling 18 (2012) 4113-4120 F. I. 1.797
    Molecular beacon is a DNA probe containing a sequence complementary to the target that is flanked by self-complementary termini, and carries a fluorophore and a quencher at the ends. We used the fluorescein and dabcyl as fluorophore and quencher respectively, and studied with DFT calculations at the GGA/DNP level, and taking into account DFT dispersion corrections by the Grimme and Tkatchenko-Scheffler (TS) schemes, the distance, where the most favorable energetic interaction between the fluorophore and quencher in conjugated form occurs. This distance occurs at a separation distance of 29.451 Å between the centers of Dabcyl and fluorescein employing the TS DFT dispersion correction scheme, indicating FRET efficiency around 94.28 %. The calculated emission spectra of the conjugated pair in water indicated that the emission and absorption spectrum overlap completely and thus no fluorescence can be observed due to the fluorescence resonance energy transfer (FRET) effect. The DFT results confirmed the experimentally observing fluorescence quenching of the fluorescein-dabcyl conjugated system by FRET.
  95. Comparative Computational Characterization of Au4 on a Carbon Nanotube with and without Defects using ONIOM Method
    Diana Barraza Jiménez, D. H. Galván, Álvaro Posada Amarillas, Manuel Alberto Flores Hidalgo, Daniel Glossman Mitnik and Miguel José Yacamán.
    Journal of Molecular Modeling 1.797 (2012) 4885–4891 F. I. 1.797
    We use ONIOM (QM/MM) methodology to carry out geometry calculations in a 4-atom nanocluster supported by an (8, 8) armchair carbon nanotube with and without defects employing LSDA/SDD for the QM system and UFF for MM. In two particular cases, defects were added in the carbon nanotube wall. These defects are a double oxygenated vacancy (Vac2O2) and a double vacancy but without oxygen which creates two pentagons and an octagon. Our results show how geometries using QM/MM and energies calculations carried out with QM, change on both the gold nanocluster and the carbon nanotube. In addition, an application of ONIOM methodology in a comparative study to predict behavior of structures as hybrid materials based in carbon nanotubes combined with gold nanoclusters is shown. In this work we examine geometry changes on both the gold nanocluster and the carbon nanotube. A comparison is made with the binding energy resulting values as well as with the orbital energies such as the frontier orbitals HOMO and LUMO.
  96. Computational chemistry calculations of stability for bismuth nanotubes, fullerene-like structures and hydrogen-containing nanostructures
    Oxana V. Kharissova Mario Osorio Mario Sánchez Vázquez Boris I. Kharisov.
    Journal of Molecular Modeling 18 (2012) 3981-3992 F. I. 1.797
    Using molecular mechanics (MM+), semi-empirical (PM6) and density functional theory (DFT) (B3LYP) methods we characterized bismuth nanotubes. In addition, we predicted the bismuth clusters {Bi20(C 5V ), Bi24(C 6v ), Bi28(C 1 ), B32(D 3H ), Bi60(C I )} and calculated their conductor properties.
  97. Computational study of Au_4 cluster on a carbon nanotube with and without defects using QM/MM methodology
    Barraza-Jimenez, D (Barraza-Jimenez, Diana)1; Galvan, DH (Galvan, D. H.)2; Posada-Amarillas, A (Posada-Amarillas, Alvaro)3; Flores-Hidalgo, MA (Alberto Flores-Hidalgo, Manuel)4; Glossman-Mitnik, D (Glossman-Mitnik, Daniel)4; Jose-Yacaman, M (Jose-Yacaman, Miguel)5.
    Journal of Molecular Modeling 18 (2012) 4885-4891 F. I. 1.797
    We use ONIOM (QM/MM) methodology to carry out geometry calculations in a 4-atom nanocluster supported by an (8, 8) armchair carbon nanotube with and without defects employing LSDA/SDD for the QM system and UFF for MM. In two particular cases, defects were added in the carbon nanotube wall. These defects are a double oxygenated vacancy (Vac(2)O(2)) and a double vacancy but without oxygen which creates two pentagons and an octagon. Our results show how geometries using QM/MM and energies calculations carried out with QM, change on both the gold nanocluster and the carbon nanotube. In addition, an application of ONIOM methodology in a comparative study to predict behavior of structures as hybrid materials based in carbon nanotubes combined with gold nanoclusters is shown. In this work we examine geometry changes on both the gold nanocluster and the carbon nanotube. A comparison is made with the binding energy resulting values as well as with the orbital energies such as the frontier orbitals HOMO and LUMO.
  98. Elastic properties of an orthotropic binary fiber-reinforced composite with auxetic and conventional constituents
    G. G. Nava Gómez, H. Camacho Montes, F. J. Sabina, R. Rodríguez Ramos, L. Fuentes, R. Guinovart Díaz.
    Mechanics of Materials 48 (2012) 1--25 F. I. 1.769
    Closed-form expressions for the nine effective elastic constants of a binary fiber-reinforced composite with transversely isotropic constituents with positive (conventional) and negative (auxetic) Poisson’s ratio are considered. Such formulae were obtained by means of the asymptotic homogenization method and were verified numerically with an independent finite element model. The overall properties display explicit dependence on (i) the properties of the constituents, (ii) the volume fraction or radius of inclusion and (iii) the array periodicity. They are finally obtained by solving a normal infinite symmetric linear system of algebraic equations by truncation to a relatively small order term. This allows a fast solution and low computation cost. The overall orthotropy of the elastic properties is obtained by varying the distance between the fibers in two of the principal directions leading to different spacial aspect ratio for fiber distribution. In addition to this, an analytical relation between the effective properties based on the symmetry of the stiffness tensor is introduced. With the previous elements, we present reliable predictions for auxetic and conventional composites of this kind wherein a significant enhancement in Young’s modulus is found in a composite with an auxetic matrix reinforced by conventional fibres. Finally, we compute auxeticity windows (i.e., intervals of volume fraction where the composite is auxetic) when the fibres are auxetic. It is reported that spacial fiber aspect ratio plays a key role in the composite auxetic behavior.
  99. Hercynite and magnesium aluminate spinels acting as a ceramic bonding in an electrofused MgO–CaZrO3 refractory brick for the cement industry
    Edén Rodríguez, G Alan Castillo, José Contreras, R. Puente Ornelas, J.A. Aguilar Martínez, Laura García, Cristian Gómez.
    Ceramics International 38 (2012) 6769–6775 F. I. 1.751
    nnovative chrome-free basic refractory bricks have been design based on electrofused magnesia–calcium zirconate (MgO-CaZrO3) technology using as ceramic bonding magnesium aluminate spinel (MgAl2O4) and hercynite spinel (FeAl2O4) in order to improve their properties. Industrial refractory bricks have been manufactured by solid state sintering of magnesium and calcium zirconate aggregates with MgAl2O4 and FeAl2O4 spinels at 1650 °C in a tunnel kiln. Physical and microstructural characteristics of new refractory bricks have been characterised in terms of density, porosity, crystalline phases, phase distribution and morphology. X-ray diffraction (XRD) analyses and scanning electron microscopy (SEM) with microanalysis (using energy dispersive spectroscopy analysis -EDS) have been used. The mechanical behaviour has been evaluated in terms of cold crushing strength (CCS) at room temperature and three point bending modulus of rupture (MOR) at 25 and 1260 °C. Static and dynamic resistance test by chemical attack of clinker raw meal constituents have been carried out at 1450 °C. Results have shown that thermo-mechanical properties of new refractory bricks significantly improved with increasing both type of spinel in content. Microstructural analysis revealed that spinel phases aided to develop a strong bond between the magnesia and calcium zirconate refractory aggregates. Finally, these refractory matrixes exhibit a good thermal stability and an excellent chemical resistance against clinker raw meal.
  100. Effect of Synthesis Variables on the Fluorescence Properties of CdSe-Polystyrene Latexes
    Anilú Rubio-Ríos, Bethsy Adriana Aguilar-Castillo, Sergio Flores-Gallardo, Claudia Alejandra Hernández-Escobar, Erasto Armando Zaragoza-Contreras.
    Journal of Polymer Research 19 (2012) 9833 F. I. 1.733
    The development of photoluminescent materials based on the incorporation of quantum dots (QDs) into polymeric latexes has gained importance due to the multiple potential applications. Through the process of miniemulsion polymerization it is possible to encapsulate quantum particles into polymer matrix to provide both chemical stability and to maintain emission properties. The polymerization process was achieved with continuous magnetic stirring and nitrogen atmosphere. Cetyl trimethylammonium bromide (CTAB) was used as surfactant at concentration levels of 1.3 × 10-3, 3.2 × 10-3 and 5.4 × 10-3 M. The initiator 2,2-azobisisobutyronitrile (AIBN) was used at 0.50 and 0.75 wt% and CdSe QDS were used at 0.075, 0.15 and 0.225 wt%, both in relation to monomer content. A STEM study on the composite latexes and later a statistical study on the measurement of polymer particle diameter let us corroborate that the increment in surfactant concentration produces a decrement in polymer particle size. The obtained composite latexes were stable and showed fluorescence by excitation with UV light. The spectrofluorometry studies indicated that in composite latexes fluorescent emission was a function of polymer particle size, showing higher intensity those formulations with smaller surfactant concentrations and bigger polymer particle size.
  101. Growth and microstructural study of CuO covered ZnO nanorods
    F. Pola-Albores, W. Antúnez-Flores, P. Amézaga-Madrid, E. Ríos-Valdovinos, M. Valenzuela-Zapata, F. Paraguay-Delgado, M. Miki-Yoshida.
    Journal of Crystal Growth 351 (2012) 77-82 F. I. 1.726
    A feasible method to synthesize CuO covered ZnO nanorods was realized. Firstly, ZnO nanorods were grown by wet-chemical route at 90 °C onto borosilicate glass substrates. Subsequently, the CuO covered ZnO matrix was obtained by Aerosol-Assisted Chemical Vapor Deposition at different temperatures (300, 400, 500 and 600 °C). The CuO–ZnO nanocrystals were microstructurally characterized by electron microscopy and Rietveld refinement. Results showed a CuO formed nanocrystals but also an amorphous fraction of CuO which increases with the synthesis temperature. Additionally, it was evident the presence of secondary copper-oxide phase (paramelaconite), which also has grown over the ZnO nanorod surface.
  102. Full bridge circuit based on pentacene schottky diodes fabricated on plastic substrates
    G Gutierrez-Heredia, VH Martinez-Landeros, FS Aguirre-Tostado, P Shah, BE ....
    Semiconductor Science and Technology 27 (2012) doi:10.1088/02681242/27/8/085013 F. I. 1.723
    In this work, we demonstrate a full bridge diode (FBD) circuit compatible and fabricated on flexible polyethylene naphthalene (PEN) substrate. The fabrication was carried out using photolithography-based processes and pentacene Schottky diodes as the active circuit components. The individual pentacene diodes show the on/off current ratio of 105, with reverse and forward bias current densities of 10−4 and 102 A cm−2, respectively. Diodes and the full bridge configuration were measured in the range of −10 to +10 V. Discrete diodes fabricated in the same substrate show similar behavior to those integrated in the FBD circuit. The frequency response was evaluated using an ac signal and voltage ranging from 1 to 5 MHz and −10 to +10V, respectively. The dc output voltage under these conditions was 7–8.5 V for individual diodes and 3–5.5 V for the FBD circuit. The resulting FBD circuits show full wave rectification for ac signals up to ±10 V in the frequency regime tested. The circuit demonstrated could be used for ac-related energy harvesting requiring rectification. One of such energy harvesting approaches could be power generated from micro-cantilevers.
  103. X-ray diffraction and atomic force microscopy study in aged zirconia-toughened alumina composite with dispersion of m-ZrO2 nanoparticles
    A. Reyes Rojas, E. Torres Moye, O. Solís Canto, A. Aguilar Elguézabal and M.H. Bocanegra Bernal.
    International Journal of Refractory Metals and Hard Materials 35 (2012) 270-278 F. I. 1.693
    X-ray diffraction (XRD) and atomic force microscopy (AFM) were utilized to investigate the aging behavior of pressureless sintered monolithic ZrO2 (TZ-3Y) and zirconia-toughened alumina composite with additions of 2 wt% m-ZrO2 nanoparticles at 1520 °C for 1 h. Results show that TZ-3Y exhibited significant aging in water steam at 134 °C under pressure 2 bar compared to zirconia toughened alumina (ZTA) composite. The maximum fraction of monoclinic polymorph resulted after 10 and 15 h of aging for monolithic TZ-3Y (~ 85%) and ZTA (~ 2.3%) composite, respectively. The homogeneous dispersion of zirconia into the matrix and its fine grain size as well as the high Young's modulus of the Al2O3 matrix which can provide a constraining effect on the zirconia could partially inhibit the phase transformation. In terms of monoclinic phase content, our ZTA composite fulfil ISO 1336–2008 requirements for implants for surgery, being thus an interesting alternative in this field. ⺠ZTA composites could be a promise for medical and dental applications. ⺠Grain size has influence on monoclinic phase content. ⺠Alumina matrix provides high thermal degradation resistance. ⺠Monolithic TZ-3Y exhibited significant aging compared to ZTA composite. ⺠ZTA composite could fulfil requirements for implants in terms of monoclinic phase content.
  104. X-ray diffraction evidence of a phase transformation in zirconia by the presence of graphite and carbon nanotubes in zirconia toughened alumina composites.
    M.H. Bocanegra Bernal, A. Reyes Rojas, A. Aguilar Elguézabal, E. Torres Moye, J. Echeberria..
    International Journal of Refractory Metals and Hard Materials 35 (2012) 315–318 F. I. 1.693
    We have demonstrated by X-ray diffraction a transformation from the t-ZrO2 phase into the m-ZrO2 phase by the presence of multiwall carbon nanotubes (MWCNTs) and graphite powder (GP) in zirconia toughened alumina composites sintered in air. The phase transformation does not occur in sintering under an argon atmosphere. The quantitave phase analysis was carried out by fitting the X-ray diffraction profile with the Rietveld method making use of the FullProf software. The obtained amounts of m-ZrO2 phase by the presence of GP and MWCNTs were 5% and 2.2%, respectively, at a sintering temperature of 1520 °C for 1 h. ⺠ZTA composites could be a promise in the industry and technology. ⺠Carbon nanotubes and graphite powder could transform the tetragonal zirconia. ⺠Possible surface reaction sintering can contribute to transformation of t-ZrO2
  105. Glass transition study in model food systems prepared with mixtures of fructose, glucose and sucrose
    M. Z. Saavedra-Leos, A. Grajales-Lagunes, R. González-García, A. Toxqui-Teran, S. A. Pérez-García, M. Abud-Archila, M. A. Ruiz-Cabrera.
    Journal of Food Science 77 (2012) E118–E126 F. I. 1.658
    The glass transition temperature of model food systems prepared with several glucose/fructose/sucrose mass fractions was studied using differential scanning calorimetry (DSC). A distance-based experimental design for mixtures of 3 components was used to establish the proportion of sugars of the model systems. Thus, 32 compositions including individual sugars and sugar mixtures, both binary and ternary were prepared and analyzed. Thermograms showing the complete process of heating–cooling–reheating were used to determine the precise glass transition temperature during cooling (inline image) or reheating (inline image) in amorphous sugars. The Scheffe cubic model was applied to experimental results to determine the influence of sugar composition on the glass transition temperature (P < 0.05). The final model proved to be appropriate (R2 > 0.97, CV < 9%, model significance <0.0001) to predict the Tg values of any dry mixture of amorphous fructose, glucose, and sucrose.
  106. Risk analysis of residental area close to the tailing dams of an exfoundry
    Ma. Cecilia Valles Aragón, Ma. Teresa Alarcón Herrera.
    Environmental Progress and Sustainable Energy 0 (2012) doi: 10.1002/ep.11701 F. I. 1.649
    Several old mining sites in Latin America are unexpectedly turning into residential areas, posing a high health risk for its residents. Hence, we address the case of an old mineral processing plant and foundry, located in Chihuahua, Mexico. This study comprised site sampling, determination of Pb contents in the soil, and a risk analysis of the exposed child population via the Integrated Exposure Uptake Biokinetic Model (IEUBK, USEPA model). Three exposure scenarios were derived from the Pb concentrations found in soil and were classified as: maximum (A), average (B), and minimum (C). The IEUBK considered two amounts of soil intake: (350 mg/day) for areas without paved streets and (200 mg/day) for paved streets. Results show that 62% of the samples exceed the maximum permissible level recommended for lixiviates, which indicates the solubility and possible dispersion of metal contents. 90% of the samples exceed the permissible contents of Pb for residential use and 85% are above guidelines for industrial use. Results from the IEUBK model, considering unpaved streets, show that the average concentration of Pb in blood in scenarios A, B, and C were 79.94, 16.58, and 9.25 μg/dL, respectively. For communities with paved streets and under the same conditions, the amounts of Pb in blood decreased to 57.75, 11.57, and 4.18 μg/dL respectively. In both cases, the maximum permissible concentration of Pb in children's blood is exceeded. It is imperative to take the appropriate remediation measures in this site to reduce the Pb contents in the soil and to minimize the public health risk. © 2012 American Institute of Chemical Engineers Environ Prog, 2012
  107. Corrigendum to “Computational study of the molecular structure and reactive sites of the R and S isomers of persin diene” [J. Mol. Struct. (THEOCHEM) 869 (2008) 67–74]
    Ana María Mendoza-Wilson, , Graciela Dolores Ávila-Quezada, René Renato Balandrán-Quintana, Daniel Glossman-Mitnik.
    Computational and Theoretical Chemistry, Formerly known as Journal of Molecular Structure: THEOCHEM. 989 (2012) 100 F. I. 1.634
    The structures that were labeled as R and S enantiomers are not enantiomers but are instead conformational isomers. Hence, the reported calculations cannot explain differences in biological activity of the two enantiomers and would not support a discussion of enantiomeric effects. We very much regret this serious error, and we thank Dr. Raymond Carman for pointing it out. Also, the experimental X-ray data that we have transcribed to Table 4 do not correspond to these isomers, but to the cis,cis-1,4-pentadiene system from other dienes and polyenes. The values were from Ref. [25] (Z. Rappoport, The Chemistry of Dienes and Polyenes, vol. 1, John Wiley and Sons, New York, 1997), and not from Ref. [28], and so, the correct form of Table 4 footnote should be: Data obtained by single-crystal X-ray diffraction for dienes and polyenes other than persin diene in Ref.
  108. Synthesis and properties of crystalline silver nanoparticles supported in natural zeolite chabazite
    Flores-López, NS; Castro-Rosas, J; Ramírez-Bon, R; Mendoza-Córdova, A; Larios-Rodríguez, E; Flores-Acosta, M..
    Journal of Molecular Structure 1028 (2012) 110-115 F. I. 1.634
    A simple, low-temperature, hydrothermal method for the synthesis of silver nanoparticles supported on the surfaces of the natural zeolite chabazite has been developed. The synthesis method includes two ion exchange processes: the first is a conditioning process to exchange the natural cations included in the chabazite tuff with NH4 ions, and the second exchanges the latter ions with silver. The precipitation of silver nanoparticles is achieved by thermal annealing of the silver-exchanged chabazite at 400 degrees C for 1 h. The samples were studied with X-ray diffraction, Fourier-transform infrared spectroscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy and diffuse reflectance spectroscopy. The results show the presence of both silver cations and nanoparticles in the chabazite matrix, the silver nanoparticles being located at the surface of the chabazite microcrystals. The silver nanoparticles are crystalline with an average size of 8 nm and show cube-truncated shapes. The absorption spectra of the silver nanoparticles display several plasmon resonance transitions due to their geometry. The silver-supporting chabazite powders have bactericide properties against several types of bacteria as was shown by the inhibition of bacteria growth on conventional agar medium.
  109. Magnetic property enhancement and crystal structures in bulk and nanosized ZnxNi1 − xFe2O4 (0⩽x⩽1)
    Cristian E. Botez, Kanokporn Chattrakun, Alejandro J. Metta Magaña, Keith H. Pannell, José A. Matutes Aquino.
    Physics Letters A 376 (2012) 2730–2734 F. I. 1.632
    Dc-magnetization, ac-susceptibility and x-ray diffraction (XRD) were used to investigate the microscopic origin of the magnetic property modifications induced by zinc doping in bulk and nanosized nickel ferrite, ZnxNi1 − xFe2O4. Both the nanoparticle energy barrier to magnetization reversal, EB, and the bulk saturation magnetization, Ms, are observed to initially increase with x, reach a maximum at x∼0.5, and eventually decrease upon further doping. XRD data do not indicate significant structural modifications at x∼0.5. Instead we found evidence that an indirect doping mechanism, by which Ni2+ ions are replaced by Zn2+, is responsible for the observed magnetic property enhancement.
  110. Partial crystallization in exotic phase stishovite of amorphous silica xerogels induced by incorporation of chlorophyll species
    Martínez, JR; Espericueta, E; Guerrero-Serrano, AL; Ortega-Zarzosa, G..
    Journal of Sol-Gel Science and Technology 4 (2012) 661-666 F. I. 1.632
    Using the Rietveld refinement, we analyze the structural evolution under thermal treatment of silica xerogel samples with incorporation of extract from frozen spinach leaves, prepared by sol-gel method with low molar ratio (R) of water to TEOS of R = 1, and R = 5. Partial crystallization of silica xerogel in the form of stishovite has been obtained at atmospheric pressure conditions and temperatures of 200 A degrees C, they both, very lower than those specified by the phase diagram, in samples containing chlorophyll aggregates dispersed in amorphous silica. The results show that the incorporation of spinach extracts leave together with low water contents induce devitrification of the silica matrix in exotic phase stishovite.
  111. SnO2 thin films grown by pulsed Nd:YAG laser deposition
    Díaz, ECY (Chan y Díaz, E.)1; Duarte-Moller, A (Duarte-Moller, A.)1; Camacho, JM (Camacho, Juan M.)2; Castro-Rodríguez, R (Castro-Rodríguez, R.)2.
    Applied physics a materials science & processing 106 (2012) 619-624 F. I. 1.63
    SnO2 thin films have been deposited on glass substrates by pulsed Nd:YAG laser at different oxygen pressures, and the effects of oxygen pressure on the physical properties of SnO2 films have been investigated. The films were deposited at substrate temperature of 500°C in oxygen partial pressure between 5.0 and 125 mTorr. The thin films deposited between 5.0 to 50 mTorr showed evidence of diffraction peaks, but increasing the oxygen pressure up to 100 mTorr, three diffraction peaks (110), (101) and (211) were observed containing the SnO2 tetragonal structure. The electrical resistivity was very sensitive to the oxygen pressure. At 100 mTorr the films showed electrical resistivity of 4×10-2 O?cm, free carrier density of 1.03×1019 cm-3, mobility of 10.26 cm2?V-1?s-1 with average visible transmittance of ~87%, and optical band gap of 3.6 eV.
  112. Toxicity of Uranium to Microbial Communities in Anaerobic Biofilms
    Aida Tapia-Rodríguez, Antonia Luna-Velasco, James A. Field, Reyes Sierra-Alvarez.
    Water Air Soil Pollution 223 (2012) 3859-3868 F. I. 1.625
    Microbial processes have shown promise for the remediation of uranium and nitrate in groundwater impacted by uranium mine tailings. This study investigated the inhibitory impact of uranium(VI) towards different microbial populations in anaerobic biofilms, including methanogenic, denitrifying, and uranium-reducing microorganisms, which are commonly found at uranium bioremediation sites. Results of batch activity bioassays indicated a very distinct level of toxicity depending on the targeted microbial community. U(VI) caused severe inhibition of acetoclastic methanogenesis as indicated by a 50 % inhibiting concentration (IC50) of only 0.16 mM. Denitrifying populations were also impacted by uranium, but their sensitivity depended on the electron donor utilized. Sulfur-oxidizing denitrifiers were the least affected (IC50 for denitrification activity = 0.32 mM), followed by H2- and acetate-utilizing denitrifiers (IC50 of 0.20 and 0.15 mM, respectively). In contrast, exposure to U(VI) concentrations up to 1.0 mM did not inhibit the rate of U(VI) bioreduction with H2 as electron donor in the presence or absence of nitrate. On the contrary, a considerable increase in the uranium-reducing activity of the denitrifying and methanogenic mixed cultures was observed with increasing uranium concentrations. The results suggest that microorganisms responsible for U(V) reduction could tolerate much higher uranium concentrations compared to the other microbial populations assayed.
  113. Synthesis of ZnO and ZnO2 nanoparticles by the oil-in-water microemulsion reaction method
    Kelly Pemartin, Conxita Solans, German Vidal Lopez, Margarita Sanchez Dominguez.
    Chemistry Letters 41 (2012) 1032-1034 F. I. 1.587
    Crystalline ZnO and ZnO2 nanoparticles (NPs) were prepared in one-pot oil-in-water (O/W) microemulsion media at room temperature by adding an aqueous solution of sodium hydroxide (followed by H2O2 in the case of synthesis of ZnO2) to the O/W microemulsion containing a Zn(II) organometallic precursor dissolved in the oil phase. After calcination of ZnO2 NPs, ZnO NPs were also obtained, and their characteristics were compared with those of ZnO NPs prepared directly in O/W microemulsion. The materials were characterized by X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy.
  114. Microstructure and mechanical properties of 7075 aluminum alloy nanostructured composites processed by mechanical milling and indirect hot extrusion,
    R. Flores-Campos, I. Estrada-Guel, M. Miki-Yoshida, R. Martínez-Sánchez, J. M. Herrera-Ramírez.
    Materials Characterization 63 (2012) 39-46 F. I. 1.572
    Nanostructured composites of 7075 aluminum alloy and carbon coated silver nanoparticles were produced by mechanical milling and indirect hot extrusion. The milling products were obtained in a high energy SPEX ball mill, and then were compacted by uniaxial load and pressure-less sintered under argon atmosphere. Finally, the sintered product was hot extruded. Carbon coated silver nanoparticles were well distributed in the matrix of the extruded material. Tensile tests were carried out to corroborate the hypothesis that second phase particles, well dispersed in the matrix, improve the strength of the material. High resolution transmission electron microscopy was employed to locate and make sure that the silver nanoparticles were homogeneously and finely dispersed.
  115. Effect of milling time and CNT concentration on hardness of CNT/Al2024 composites produced by mechanical alloying
    R. Pérez Bustamante, F. Pérez Bustamante, I. Estrada Guel, L. Licea Jiménez, M. Miki Yoshida, R. Martínez Sánchez,.
    Materials Characterization * (2012) 13–19 F. I. 1.572
    Carbon nanotube/2024 aluminum alloy (CNT/Al2024) composites were fabricated with a combination of mechanical alloying (MA) and powder metallurgy routes. Composites were microstructurally and mechanically evaluated at sintering condition. A homogeneous dispersion of CNTs in the Al matrix was observed by a field emission scanning electron microscopy. High-resolution transmission electron microscopy not only confirmed the presence of well dispersed CNTs but also needle-like shape aluminum carbide (Al4C3) crystals in the Al matrix. The formation of Al4C3 was suggested as the interaction between the outer shells of CNTs and the Al matrix during MA process in which crystallization took place after the sintering process. The mechanical behavior of composites was evaluated by Vickers micro hardness measurements indicating a significant improvement in hardness as function of the CNT content. This improvement was associated to a homogeneous dispersion of CNTs and the presence of Al4C3 in the aluminum alloy matrix.
  116. Evaluation of strain caused by coherent precipitates in an Al alloy using TEM techniques
    J.L. Hernández Rivera, J.J. Cruz Rivera, C.G. Garay Reyes, M. Ramos Azpeitia, I. Zúñiga Alonso, R. Martínez Sánchez.
    Materials Characterization 73 (2012) 61-67 F. I. 1.572
    Elastic strains, caused by GP zones in an aged Al alloy, were determined quantitatively using two techniques: Dark Field In-line Holography (DFH) and High Resolution Transmission Electron Microscopy-Geometric Phase Analysis (HRTEM-GPA). The results obtained by both techniques showed that the elastic strain was not uniform along the precipitate–matrix interface. In some areas, it was found that strain had negligible value and this was attributed to the loss of coherence between the lattices. It is suggested that a possible explanation for this fact could be a variation in the “vacancies pump mechanism” kinetics. To obtain a better interpretation of the experimental deformation maps, a reference GP precipitate–matrix structure was built using QSTEM software. The main advantages of DFH over HRTEM-GPA were a bigger field of view and low electron dose requirements without spatial resolution loss. Another difference found was that crystalline defects such as dislocations were evidenced by HRTEM-GPA in contrast to the result obtained by DFH. However, strain measurements were affected by mask size effect in the former.
  117. The Frenet-Serret representation of the Landau-Lifshitz-Gilbert equation
    Vítor R Vieira1 and Paul P Horley2.
    Journal of Physics A-Mathematical and Theoretical 45 (2012) 65208 F. I. 1.564
    A proper representation of the Landau–Lifshitz–Gilbert equation is important to obtain useful parameters and characteristics of the system and its dynamics and for speeding up the calculations. In this paper, we report the successful use of the Frenet–Serret system of tangent, normal and binormal vectors, allowing one to extract important information about the curvature and torsion of the phase portrait trajectories describing the dynamics of the magnetization vector. For comparison, we also present the spherical representation of the same equation.
  118. Nanosized polypyrrol affected by surfactant agitation for emulsion polymerization
    Yusuke Hoshina, Erasto Armando Zaragoza-Contreras, Ramin Farnood, Takaomi Kobayashi.
    Polymer Bulletin 12 (2012) 250-260 F. I. 1.532
    Nanosized conductive polypyrrole (PPy) powders were prepared using emulsion polymerization with aid of high speed agitation. Different agitation speeds from 650 to 24,000 rpm were used with different anionic, cationic, and non-ionic surfactants. Then, the effects of the agitation speed and surfactant species were examined in terms of their physical and electrical properties of conductivity and powder size. Prepared PPy nanopowders exhibited high conductivity values of 10 S/cm regions, when sodium dodecylbenzenesulfonate (SDBS) and sodium dodecylsulfate (SDS) were used. The powder dispersion of the resultant PPy was also observed to be dependent on the agitation speed and surfactant type. The morphology shown by SEM and TEM revealed that the anionic SDBS surfactant could effectively disperse into nanosized aggregates of the PPy. The results showed that the combination of the anionic surfactants and high agitation in the emulsion polymerization could produce nanosized PPy powders with higher conductivity.
  119. Particle density distribution in a pyramid-shaped quantum well
    Paul P. Horleya, , , Pedro Ribeirob, Vítor R. Vieirab, Jesús González-Hernándeza, Yuri V. Vorobievc, Luis Gerardo Trápaga-Martínezc.
    Physica E: Low-dimensional Systems and Nanostructures 44 (2012) 1602–1607 F. I. 1.532
    This paper is focused on analytical solution of the quantum–mechanical problem describing a particle confined into a pyramid-shaped quantum well. This type of micro- and nano-scale objects can be formed on the surface of semiconductor material as texturing elements for solar cells, Bragg reflectors, quantum dot lasers, etc. The problem was treated using specular reflections of plain wave functions of the particle from the sides of the pyramid. Defining a closed group of symmetry transformations for the system, we solve Schrödinger equation in the Cartesian coordinates. This wave function was used to calculate three-dimensional distributions of particle probability density within a square-based pyramid. Analysis of excited states energy reported in publications shown good correlation between our theoretical calculations and experimental data.
  120. Semicontinuous heterophase polymerization of methyl methacrylate in the presence of reactive surfactant HITENOL BC10
    Ovando-Medina, VM (Ovando-Medina, Victor M.)1; Pina-Garcia, PS (Pina-Garcia, Piedad S.)1; Corona-Rivera, MA (Corona-Rivera, Miguel A.)1; Diaz-Flores, PE (Diaz-Flores, Paola E.)1; Peralta, RD (Peralta, Rene D.)2; Martinez-Gutierrez, H (Martinez-Gutierrez, Hugo)3; Lara-Ceniceros, TE (Lara-Ceniceros, Tania E.)4.
    Polymer Bulletin 68 (2012) 2313-2322 F. I. 1.532
    Semicontinuous heterophase polymerization was used to copolymerize methyl methacrylate (MMA) with reactive surfactant HITENOL BC10 (HBC10) at 60 A degrees C using sodium dodecyl sulfate as pre-stabilizing agent and potassium persulfate as initiator. The mixture of MMA and HBC10 was added at constant rate in continuous mode varying the MMA/HBC10 ratio. High-polymerization rates were observed, decreasing as the MMA/HBC10 ratio decreased. Latexes with polymer content near 20% and polymer to surfactant (P/S) weight ratios between 5 and 15 were obtained. Particle sizes distribution were bimodal in all cases with a tendency to be monomodal as HBC10 concentration increased which was ascribed to enhanced particle stabilization by the presence of HBC10. The average particle diameters at the end of polymerizations for the first and second populations were around 10 and 50 nm, respectively. Very high average molecular weights were observed (1.4 x 10(6) a parts per thousand currency sign M (w) a parts per thousand currency sign 2.1 x 10(6) g/mol), which decreased when HBC10 concentration increased.
  121. Experimental and theoretical determination of the low-loss electron energy loss spectroscopy of nanostructured ZnO
    H.J. Morales-Rodríguez and F. Espinosa-Magaña.
    Micron 43 (2012) 177-182 F. I. 1.527
    The dielectric properties of nanostructured wurtzite-type ZnO are studied by analyzing the low-loss region of the electron energy loss spectroscopy (EELS) in a transmission electron microscope. Characteristic peaks at about 12 and 32 eV in the imaginary part of the dielectric function shift to lower energies as particle size decreases. A comparison of experimental EELS spectra and ab initio density-functional theory calculations (WIEN2k code) within the generalized gradient approximation (GGA), GGA + U and modified Becke-Johnson (mBJ) is presented. The origins of interband transitions are identified in the electronic band structure by calculating the partial imaginary part of the dielectric function and the partial density of states of Zn and O.
  122. Cathodoluminescence and photoluminescence of swift ion irradiation modified zinc oxide-porous silicon nanocomposite
    Yogesh Kumara, Manuel Herrera, Fouran Singhc, S.F. Olive Méndez, D. Kanjilal, Shiv Kumar, V. Agarwal, .
    Materials Science and Engineering B-Advanced Functional Solid-State Materials 117 (2012) 1476–1481 F. I. 1.518
    We report the room temperature cathodoluminescence and photoluminescence of swift ion irradiated (130 MeV Nickel ion) porous silicon zinc oxide nanocomposites. The evolution of a broad and flat emission band from 1.5 to 3.5 eV is demonstrated. Annealing effect of irradiation is found to result in a relative increase in the band edge emission. Emission wavelength can be tuned in the complete visible range by changing the substrate characteristics.
  123. Device for simultaneous measurements of the optical and dielectric properties of hydrogels
    Gómez- Galván, F (Gómez- Galván, F.)1,2; Lara- Ceniceros, T (Lara- Ceniceros, T.)1; Mercado- Uribe, H (Mercado- Uribe, H.)2.
    Measurement Science and Technology 23 (2012) doi: 10.1088/0957-0233/23/2/025602 F. I. 1.494
    We have designed an experimental device to simultaneously measure the light transmittance and dielectric properties of thermo-sensitive hydrogels. We have used this device to study poly(N-isopropylacrylamide) samples in order to understand the mechanism of water deliverance during the phase transition such hydrogels normally exhibit. We found that the phase transition can be observed dielectrically at low frequencies, when the isothermals obtained during the heating of the samples separate into two groups. The phenomenon occurs due to the increase of ions caused by the dissociation of water molecules released by the polymer, and corresponds to the drop of the optical transmittance.
  124. Elastic Modulus Determination of Al-Cu Film Alloys Prepared by Thermal Diffusion
    Huerta, E; Oliva, AI; Avilés, F; González Hernández, J;Corona, JE..
    Journal of Nanomaterials * (2012) doi: 10.1155/2012/895131 F. I. 1.376
    Elastic moduli of 50-250nm thick Al-50 at % Cu film alloys deposited by thermal evaporation on Kapton substrates and postformed by thermal diffusion are investigated. Formation of the Al2Cu alloy phase was confirmed by X-ray photoelectron spectroscopy (XPS). Surface morphology was examined by atomic force microscopy (AFM) and scanning electron microscopy (SEM) before and after tensile mechanical testing. Force-strain curves of the Al-Cu alloy were obtained by subtracting the effect of the force-strain Kapton curves from the corresponding curves of the Al-Cu/Kapton system. A reduction in the elastic modulus of the Al-Cu alloys from 106.1 to 77.8 GPa with the increase of alloy thickness was obtained. Measured elastic moduli were between the reported bulk modulus for Al and Cu. Reductions in the surface roughness and increments in the grain size were measured after tensile testing of the Al-Cu alloys.
  125. Molecular Dynamics Analysis of PVA-AgnP Composites by Dielectric Spectroscopy
    González-Campos, JB; Prokhorov, E; Sánchez, IC ; Luna-Barcenas, JG; Manzano-Ramírez, A; González Hernández, J; López-Castro, Y; del Rio, RE..
    Journal of Nanomaterials * (2012) doi: 10.1155/2012/925750 F. I. 1.376
    The molecular dynamics of PVA/AgnP composites were studied by dielectric spectroscopy (DS) in the 20-300 degrees C temperature range. Improper water elimination leads to misinterpretation of thermal relaxations in PVA composites in agreement with the previous report for pristine PVA. The evaporation of water and its plasticizing effect are more evident in pure PVA confirming the existence of strong interaction between OH groups of PVA chains and AgnP. Dry films show a single nonlinear VFT dependence (from 45 degrees C until melting) associated to the alpha-relaxation and, therefore, to the glass transition phenomenon and from dielectric measurements, the T-g of composites vary from 88 degrees C for pristine PVA to 125 degrees C for PVA/AgnP (5 wt%). Below 45 degrees C, dry films exhibit a single Arrhenius behavior showing a 3D hopping conductivity as explained based on the variable range hopping model. PVA/AgnP composites have higher conductivity compared to pristine PVA, and it increases as AgnP weight percent increases. Finally, DMA measurements support the statement that a secondary relaxation was erroneously assigned as the glass transition of PVA and composites in previous reports.
  126. Cytotoxicity of Carbon Nanotubes on J774 Macrophages Is a Purification-Dependent Effect
    Montes-Fonseca, SL; Orrantia-Borunda, E; Duarte-Moller, A; Luna-Velasco, A; Roman-Aguirre, M; Horta, CG; Sanchez-Ramirez, B..
    Journal of Nanomaterials * (2012) doi: 10.1155/2012/715838 F. I. 1.376
    The cytotoxicity of the carbon nanotubes (CNTs) is an important factor for the manufacture of nanovaccines. The aim of this work was to evaluate the relationship of the purification method of CNTs in cellular toxicity using macrophages (MOs) from the J774 cell line. Viability test was performed with MTT assays at 24 h of exposure at concentrations of 0.06, 0.6, and 6 mg/L of unpurified (UP-CNTs) or purified (P-CNTs) CNTs by two different methods: (1) reflux with 3M HNO3 and (2) sonication in H2SO4/HNO3. Characterization and COOH content of CNTs was performed using scanning electron microscopy, raman spectroscopy, and titration with NaHCO3. P-CNTs1 had lengths >100 mu m and 2.76% COOH content, while P-CNTs2 had lengths >1 mu m and 7% COOH content. This last particle showed a lower toxic effect. The results suggest that the lenght and COOH content are important factors in the toxicity of the CNTs.
  127. On the Origin of Light Emission in Silicon Rich Oxide Obtained by Low-Pressure Chemical Vapor Deposition
    Aceves-Mijares, M; Gonzalez-Fernandez, AA; Lopez-Estopier, R; Luna-Lopez, A; Berman-Mendoza, D; Morales, A; Falcony, C; Dominguez, C; Murphy-Arteaga, R..
    Journal of Nanomaterials * (2012) doi: 10.1155/2012/890701 F. I. 1.376
    Silicon Rich Oxide (SRO) has been considered as a material to overcome the drawbacks of silicon to achieve optical functions. Various techniques can be used to produce it, including Low-Pressure Chemical Vapor Deposition (LPCVD). In this paper, a brief description of the studies carried out and discussions of the results obtained on electro-, cathode-, and photoluminescence properties of SRO prepared by LPCVD and annealed at 1,100 degrees C are presented. The experimental results lead us to accept that SRO emission properties are due to oxidation state nanoagglomerates rather than to nanocrystals. The emission mechanism is similar to Donor-Acceptor decay in semiconductors, and a wide emission spectrum, from 450 to 850 nm, has been observed. The results show that emission is a function of both silicon excess in the film and excitation energy. As a result different color emissions can be obtained by selecting the suitable excitation energy.
  128. Bioflotation of sulfide minerals with Acidithiobacillus ferrooxidans in relation to copper activation and surface oxidation
    Pecina Treviño ET, Ramos Escobedo GT, Gallegos Acevedo PM, López Saucedo FJ, Orrantia Borunda E..
    Canadian Journal of Microbiology 58 (2012) 1073-1083 F. I. 1.363
    Surface oxidation of sulfides and copper (Cu) activation are 2 of the main processes that determine the efficiency of flotation. The present study was developed with the intention to ascertain the role of the phenomena in the biomodification of sulfides by Acidithiobacillus ferrooxidans culture (cells and growth media) and their impact in bioflotation. Surface characteristics of chalcopyrite, sphalerite, and pyrrhotite, alone and in mixtures, after interaction with A. ferrooxidans were evaluated. Chalcopyrite floatability was increased substantially by biomodification, while bacteria depressed pyrrhotite floatability, favoring separation. The results showed that elemental sulfur concentration increased because of the oxidation generated by bacterial cells, the effect is intensified by the Fe(III) left in the culture and by galvanic contact. Acidithiobacillus ferrooxidans culture affects the Cu activation of sphalerite. The implications of elemental sulfur concentration and Cu activation of sphalerite are key factors that must be considered for the future development of sulfide bioflotation processes, since the depressive effect of cells could be counteracted by elemental sulfur generation.
  129. Study of structural and transport properties of nanostructured CeO2, Ce1-xRuxO2 and Ce1-xInxO2 thin films
    R. Rangel, L. Chávez-Chávez , E. Pérez-Tijerina, E. Martínez, P. Bartolo-Pérez.
    Physica Status Solidi B-Dasic Solid State Physics 7 (2012) 1199-1205 F. I. 1.316
    The present work reports for the first time thin films prepared from Ce1−xMxO2−δ (M = Ru, In) solid solutions for application as gas sensors. The CeO2, Ce0.95Ru0.05O2 and Ce0.95In0.05O2 thin films were prepared by means of the RF sputtering process onto Si (111) substrates. The deposition conditions were carried out at 500 °C varying the deposition time. Targets were prepared via sol–gel process starting from C6H9O6In, Ru3(CO)12 and Ce(C2H3O2)3 · 1.5H2O compounds and using a ceramic method to consolidate them. The samples were characterized by means of XRD, SEM, and AFM. Their thickness was measured using a profilometer. The results herein obtained regarding the microstructure and transport properties indicate that these materials can be used as gas sensors.
  130. Revisiting thermal relaxations of poly (vinyl alcohol)
    J. Betzabe Gonzalez-Campos1, Zaira Y. Garcia-Carvajal2, E. Prokhorov2, J. Gabriel Luna-arcenas2,*, M. E. Mendoza-Duarte3, Javier Lara-Romero1, Rosa E. del Rio1, Isaac C. Sanchez4.
    Journal of Applied Polymer Science * (2012) 40082-4090 F. I. 1.289
    The molecular dynamics of poly(vinyl alcohol) (PVA) were studied by dielectric spectroscopy and dynamic mechanical analysis in the 20–300°C range. The well-established plasticizing effect of water on the glass-transition temperature (Tg) of PVA was revisited. Improper water elimination analysis has led to a misinterpretation of thermal relaxations in PVA such that a depressed Tg for wet PVA films (ca. 40°C) has been assigned as a secondary β relaxation in a number of previous studies in the literature. In wet PVA samples, two different Vogel–Fulcher–Tammann behaviors separated by the moisture evaporation region (from 80 to 120°C) are observed in the low- (from 20 to 80°C) and high- (>120°C) temperature ranges. Previously, these two regions were erroneously assigned to two Arrhenius-type relaxations. However, once the moisture was properly eliminated, a single non-Arrhenius α relaxation was clearly observed. X-ray diffraction analysis revealed that the crystalline volume fraction was almost constant up to 80°C. However, the crystallinity increased approximately 11% when temperature increased to 180°C. A secondary βc relaxation was observed at 140°C and was related to a change in the crystalline volume fraction, as previously reported.
  131. In Situ TEM Study of mechanical Behaviour of Twinned Nanoparticles
    Gilberto Casillas-García, Juan Pedro Palomares-Báez, José Luis Rodríguez-López, Junhang Luo, Arturo Ponce, Rodrigo-Esparza, J. Jesús Velázquez-Salazar, Abel Hurtado-Macías, Jesús González-Hernández and Miguel José-Yacaman.
    Philosophical Magazine letters 92 (2012) 4437-4453 F. I. 1.241
    There is strong interest in studying changes in mechanical properties with reducing grain size. The rational is that consequent dislocation glide cannot be sustained, resulting in an increase in material strength. However, this comes with the cost of a reduction in ductility. It has been shown that coherent twin boundaries in nanostructured Cu improve the ductility to 14% [Lu et al., Science 324 (2009) p. 349]. In this paper, we report for the first time the compression of individual nanoparticles using an in situ force probing holder in the transmission electron microscope. Four types of nanoparticles were tested, three with twin boundaries (decahedra, icosahedra and a single twin) and one free of defects (octahedral). Our results indicate the yield strength of the twinned nanoparticles is between 0.5 and 2.0 GPa. The total malleability for the twinned particles range from 80 to 100%. In addition, experimental results were reproduced by MD simulations of the compression phenomena and suggest that the outstanding mechanical properties are related with partial dislocation multiplication at twin boundaries.
  132. Enhancement of Young's moduli and auxetic windows in laminates with isotropic constituents
    Ramírez, M ; Nava-Gómez, GG; Sabina, FJ; Camacho-Montes, H; Guinovart-Diaz, R; Rodríguez-Ramos, R ; Bravo-Castillero, J..
    International Journal ef Engineering Science 58 (2012) 95-114 F. I. 1.21
    Recently an enhancement of certain mechanical properties of composites have been shown to be attained by the introduction of auxetic phases (materials with negative Poisson's value) such as indentation resistance, fracture toughness and improved energy absorption. Here one aim is to use well-known closed-form formulas for the effective stiffness and engineering constants of a periodic composite where the repetitive cell is a laminate of n elastic isotropic constituents. The formulas are given as a function of the elastic stiffnesses or in terms of the engineering constants of the constituents and their volume fraction. Effective mechanical properties are independent of the order in which the laminas are taken. In order to confirm the theoretical formulas and show them reliable, comparisons with two independent numerical calculations using finite element are given. They are excellent. For a bilaminate the conditions by which Young's moduli are enhanced are given. Also we provide expressions for auxetic and enhancement windows. The stiffness constants exhibit certain characteristics associated with auxetics such as the negatively of non-diagonal components of the stiffness tensor. It is shown that the laminas combination of positive-positive materials may be produce enhancement of Young's moduli as some auxetic-auxetic ones. The relative indentation compliance of a circular punch upon transversely isotropic medium is calculated using Fabrikant's formulas. Two different indentations are considered. In one the indenter and the bilaminate are frictionless contact and in the other they are bonded. The indentation attains the asymptotic limits of Boussinesq or Mossakovskii-Spence when the auxetic phase is very thin compared with the width of the non-auxetic phase and in the opposite case. The results given here may be of interest in practical applications using composites with auxetic constituents when the microstructure is small compared with the dimensions of the laminate.
  133. Following the Integration of Diamond Particles on the Lapping-Plate Surface: Towards a More Efficient Charging Process.
    Mayen-Mondragón, R (Mayen-Mondragón, Rodrigo)2; Yanez-Limon, JM (Yanez-Limon, José M.)1; Espinoza-Beltrán, F (Espinoza-Beltrán, Francisco)1; Muñoz-Saldana, J (Muñoz-Saldana, Juan)1; Herrera-Gómez, A (Herrera-Gómez, Alberto)1; Vargas-Ortiz, RA (Vargas-Ortiz, Ramón A.)1; Ramírez-Bon, R (Ramírez-Bon, Rafael)1; Coronado, F (Coronado, Francisco).
    Journal Of Tribology-Transactions Of The Asme 134 (2012) doi: 10.1115/1.4006994 F. I. 1.196
    Even when the charging of lapping plates can extensively influence their subsequent finishing performance, the subject has been scarcely treated in specialized literature. The present paper aims to help fill such a gap and gain a better insight of the charging process. A semiquantification of the diamond particles integrated into the lapping plate surface as a function of charging time was performed by Raman spectroscopy and scanning electron microscopy, together with a simple image-analysis procedure. The corresponding evolution of surface rough features was followed from atomic force micrographs with the aid of fractal-analysis tools. It was observed that charging proceeds in two stages, both with different rates of diamond particle integration. This leads to a significant waste of diamond slurry. During the first stage, the charging ring seems to preferentially promote a further flattening of the lapping-plate surface. Diamond particles are apparently more readily incorporated into such flattened regions during the second stage. The results suggest a specific topographic condition must be attained before the diamond can be efficiently integrated into the lapping plate surface. A lapping-plate preconditioning step could help improve this situation and reduce the amount of abrasive waste during charging.
  134. Developing novel gas sensors for NO2 detection, based on Ce(1-x)MXO2, {M=Ru, In} solid solutions
    Rangel, R (Rangel, Ricardo)1; Chávez-Chávez, L (Chávez-Chávez, Lidia)1; García- Méndez, M (García- Méndez, Manuel)2,3; Martínez, E (Martínez, Eduardo)4.
    Journal of Electroceramics 28 (2012) 34-44 F. I. 1.194
    CeO2, Ce(1-x)MXO2, {M = Ru, In} compounds with sensing properties were fabricated using the sol-gel route. The main purpose was to compare the efficiency of CeO2 vs. Ce(1-x)MXO2 doped compounds as gas sensors for NO2 detection. Characterization was performed by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and surface area determination (BET). Measurements of electrical resistance under different conditions of time, concentration and temperature in the presence of NO2 were carried out. Ruthenium inclusion increased the CeO2 sensor response in a great extent, gas response (S) = 1.8 for CeO2 vs. gas response (S) = 350 for Ce0.95Ru0.05O2 and gas response (S) = 35 for Ce0.95In0.05O2. This behavior is reported by the first time. Our results demonstrate that ruthenium or indium inclusion has been beneficial for CeO2. Conclusively the materials herein described could be applied as NO2 gas sensors.
  135. Uranium removal from water using cellulose triacetate membranes added with activated carbon
    R. Villalobos-Rodríguez, M.E. Montero-Cabrera, H.E. Esparza-Ponce, E.F. Herrera- Peraza, M. L. Ballinas-Casarrubias.
    Applied Radiation and Isotopes 70 (2012) 872-881 F. I. 1.172
    Ultrafiltration removal of uranium from water, with composite activatedcarboncellulosetriacetatemembranes (AC-CTA), was investigated. The filtrate was provided by uraninite dissolution with pH=6–8. Removal efficiencies were calculated measuring solutions' radioactivities. Membranes were mainly characterized by microscopy analysis, revealing iron after permeation. Uranyl removal was 35±7%. Chemical speciation indicates the presence of (UO2)2CO3(OH)3−, UO2CO3, UO2(CO3)22− and Fe2O3(s) as main compounds in the dissolution, suggesting co-adsorption of uranium and iron by the AC during filtration, as the leading rejection path.
  136. Comparison of properties of cadmium, copper and lead sulfides thin filmsgrown by CBD
    Rojas-Hernandez, AG; Mendivil-Reynoso, T; Acosta-Enriquez, MC; Ramirez-Bon, R; Castillo, SJ..
    Chalcogenide Letters 9 (2012) 121-126 F. I. 0.834
    In this work we are presenting a comparative study of Cd, Cu and Pb sulfides thin films grown by Chemical Bath Deposition technique, the as ground films were polycrystalline for the Cd and Pb Sulfides while the Cu sulfide was amorphous. The Atomic Force Microscopy images gave us information about the representative surface morphology and roughness, being RMSPbS=15.3nm, RMSCdS=3.2nm, RMSCuS=30.4nm. We used UV-Vis Spectroscopy to determine simple optical responses, getting the biggest transmittances of 45% for PbS, 72% for CdS and 80% for CuS, and direct energy band gaps of 2.37 eV for CdS and 1.26 eV for CuS. We use X-rays Photoelectrons Spectroscopy to formalize the chemical composition analysis, from this analysis we could to proof the high purity of the chemical bath deposition method in the materials preparation.
  137. Nixtamalization in two steps with different calcium salts and the relationship with chemical, texture and thermal properties in masa and tortilla
    Ruiz-Gutierrez, MG ; Quintero-Ramos, A ; Melendez-Pizarro, CO (Melendez-Pizarro, C. O.)1; Talamas-Abbud, R (Talamas-Abbud, R.)1; Barnard, J (Barnard, J.)2,3; Marquez-Melendez, R ; Lardizabal-Gutierrez, D (Lardizabal-Gutierrez, D.)4.
    Journal Of Food Process Engineering 35 (2012) 772-783 F. I. 0.83
    The present investigation evaluated the chemical and thermal properties using lime and alternative calcium salts, and their effect on the characteristics of masa and tortilla obtained in a two-step nixtamalization process. White dent corn was cooked in calcium hydroxide solution (1.2% [w/v]; 1:3 maize : water ratio) at 80C (30 min), and the calcium hydroxide was replaced either by calcium chloride or lactate at calcium equilibrated concentration (30 min), and steeped in a cooking solution for 2,400 min. Grains were analyzed for water and calcium absorption, and apparent diffusion coefficients were calculated. Thermal properties of flour made from these grains were also determined. Additionally, the masa and tortilla made with nixtamalized corn flours were analyzed for texture and color, and an acceptability test was performed on the tortilla. Water absorption showed a notable increase during cooking, approaching an asymptotic maximum absorption after 8 h of steeping for all treatments. The maximum calcium absorption was obtained in stepwise nixtamalization with solutes of CaCl2 and C6H10O6Ca. The water apparent diffusion coefficients were adequately described by Fick's model and it was found that C6H10O6Ca showed the highest value (5.5901 x 10-10 m2/s), while that for calcium diffusion the model gave low fits. The thermal analysis showed that gelatinization temperatures were affected significantly (P < 0.05) by the cooking and steeping times, while the gelatinization range and enthalpy were affected significantly (P < 0.05) by salt type. The masas and tortillas obtained from all treatments presented good texture and color characteristics in comparison with the commercial flour. Sensory analysis showed that the tortilla nixtamalized with C6H10O6Ca was the most acceptable to consumers. PRACTICAL APPLICATIONS The main contribution of the present study is the utilization of different salts as an alternative to calcium during cooking and steeping in a two-phase nixtamalization process. The different calcium salts provide an option to avoid undesirable changes in the products' quality characteristics present in the typical nixtamalization process produced by high lime concentration. At the same time, these alternatives could contribute to reduced environmental pollution, specifically in the waste water (decreased pH and the solids). A prediction model for water and calcium absorption during the nixtamalization process is proposed for the different calcium salts. The physical, chemical and thermal changes that occur in the nixtamalization in the different treatments for the different calcium salts were related to color and texture characteristics of masa and tortilla as well as tortilla acceptability.
  138. Optical absorptive response of Platinum doped TiO2 transparent thin films with Au nanoparticles Materials Science in Semiconductor Processing
    Juan P Campos López, Carlos Torres Torres, Martin D Trejo Valdez, David Torres Torres, Guillermo Urriolagoitia Sosa, Luis H Hernández Gómez, Guillermo M Urriolagoitia Calderón..
    Materials Science in Semiconductor Processing 15 (2012) 421-427 F. I. 0.753
    In this paper different optical absorption bands associated to the surface plasmon of resonance of a nanoparticle containing sample were achieved by a sol–gel processing route. We study the linear and nonlinear optical absorptive properties of a titanium dioxide thin film with superficial Au nanoparticles. A chaotic behavior related with modification of the optical absorption by a multi-wave mixing interaction was investigated. A characteristic Mandelbrot group tendency was used to describe the possibility of a resulting absorptive response. The analysis of the observations showed that an excitation at 488 nm wavelength in the nanocomposite can originate a measurable change in the absorptive properties for the propagation of optical beams at 532 nm and at 650 nm. However, the inhibition of this condition exhibited by the film can be obtained by the shift of its plasmonic response. It is considered that the near resonance participation of the Au nanoparticles is mainly responsible for avoiding the photodarkening contribution to the optical absorptive response of the sol–gel TiO2 film with embedded Au nanoparticles. Potential applications of the samples are proposed for development of optical sensors or transparent thin films for filtering functions.
  139. Preparation and tribological properties of chitosan/hydroxyapatite composite coatings applied on ultra high molecular weight polyethylene substrate
    Hernández Navarro, Carolina; Moreno Bello, Karla; Arizmendi Morquecho, Ana; Chávez Valdez, Alejandra; García Miranda, Santos.
    Journal of Plastic and Film Sheeting 28 (2012) 279-297 F. I. 0.722
    We prepared a chitosan/hydroxyapatite composite as coating on ultra–high-molecular-weight polyethylene substrates. The hydroxyapatite was prepared by a precipitation method obtaining particles with nanometer sizes with needle and spherical morphologies. The coating was prepared by a mixture of hydroxyapatite and lower molecular weight chitosan. Fourier transformed infrared spectroscopy technique was used to study the hydroxyapatite synthesis and composite coating. The chitosan/hydroxyapatite coating has been compared with a pure chitosan coating on ultra–high-molecular-weight polyethylene substrate in order to study the influence of hydroxyapatite incorporation. The characterization of coating thickness was performed by light microscopy, whereas the surface morphology was characterized by scanning electron microscopy. A ball-on-disc tribometer, employing a 6-mm diameter tungsten carbide ball, was run as a test method to investigate tribological behaviors of the chitosan/hydroxyapatite and chitosan coatings in dry conditions. It was found that the friction coefficients of the chitosan/hydroxyapatite coating have lower values than chitosan coating. The chitosan/hydroxyapatite coating exhibited lower wear rate values than the chitosan coating. The incorporation of hydroxyapatite nanoparticles into chitosan increased the coating thickness from 20 µm to 37 µm. We have found a composite hardness of 9.1 HV and 6.4 HV for the chitosan and chitosan/hydroxyapatite coating, respectively.
  140. Origen y distribución de la radiactividad natural en la zona norte de la cuenca de Chihuahua, México
    Manuel Reyes Cortés, Ignacio Alfonso Reyes Cortés, Socorro Espino Valdez, Marusia Rentería Villalobos, Juan Carlos Burillo Montúfar y María Elena Montero Cabrera.
    Revista Mexicana de Ciencias Geológicas 28 (2012) 659-675 F. I. 0.697
    El valle de Chihuahua es una franja de terreno de 8 km de ancho por unos 32 km de largo, orientada de norte a sur y forma parte de la cuenca hidrológica de Chihuahua, de la que se extrae casi la totalidad del agua para el consumo de la ciudad. El agua de la presa de San Marcos, situada en la parte alta de esta cuenca, tiene materia orgánica enriquecida hasta cien veces más que el contenido de uranio con respecto al agua. El agua y los peces de la presa de San Marcos y el agua de algunos pozos de la región noroccidental del valle de Chihuahua presentan altas concentraciones de uranio. Mediante un estudio litoestratigráfico de barrenos y por mediciones de espectrometría gamma, se localizaron estratos y lentes arcillo-arenosos mezclados con material carbonoso. Estos horizontes se presentan con anomalías radiométricas de uranio en la zona noroccidental del valle de Chihuahua con valores de hasta 612 Bq/kg o aproximadamente 50 ppm. Las anomalías encontradas en el agua de algunos pozos profundos corresponden con la presencia de cuerpos de sedimentos finos, formados por posibles paleo-suelos o paleo-sedimentos de planicie de inundación. Se sugiere que estos horizontes de arcillas son recolectores del ión uranilo, que sufre un proceso de reducción por el material orgánico y es capturado. Dependiendo del pH y Eh, la removilización y oxidación del uranio causa nuevamente su reintegración al agua que se extrae de los pozos agrícolas de la región.
  141. Magneto-Structural Characterization of Strontium Substituted Lead Hexaferrite
    A.L. Guerrero-Serrano, S.A. Palomares-Sánchez, M. Mirabal-García, J.A. Matutes-Aquino.
    Journal of Superconductivity and Novel Magnetism 19 (2012) 1--6 F. I. 0.65
    In this work, the magnetic and structural properties of the system Pb 1− x Sr x Fe 12 O 19 ( x =0.1,0.3,0.5,0.7 and 0.9) are reported. The samples were prepared by the traditional ceramic method. All the compounds are isostructural with the strontium hexaferrite (SrFe 12 O 19 ). X-ray powder diffraction was used to carry out the quantitative analysis of phases and to determinate the crystallographic parameters. It was found that the compound consists of only one phase and that the coercivity, remanence and saturation increased with the strontium content. The initial susceptibility was also obtained and results are discussed in terms of the magnetization mechanisms produced by the effect of the substitution on the hexaferrite. Furthermore, Néel temperature measurements indicate a strengthening of the exchange interactions with increasing strontium content.
  142. Towards an improved calorimetric methodology for glass transition temperature determination in amorphous sugars
    M. Z. Saavedra-Leos, C. Alvarez-Salas, M.A. Esneider-Acalá, A. Toxqui-Terán, S. A. Pérez-García, M. A. Ruiz- Cabrera.
    CyTA - Journal of Food 10 (2012) 37-41 F. I. 0.632
    Measuring glass transition temperature is necessary for predicting the state and the behavior during the processing, distribution, and storage of many amorphous sugar-rich products. Therefore, the purpose of this study was to establish an improved calorimetric methodology to assess Tg in amorphous sugars. This method was created through melting crystal with differential scanning calorimetry (DSC) using the same principle proposed by Jiang, Liu, Bhandari, and Zhou (2008. Impact of caramelization on the glass transition temperature of several caramelized sugars. Part I: chemical analyses. Journal of Agricultural and Food Chemistry, 56, 5138–5147). Thermogravimetric analysis with simultaneous DSC was required to characterize the melting and thermal degradation temperatures of sugars. Thermograms showing the complete process of heating–cooling–reheating are proposed to determine the precise glass transition temperature during cooling (TgC) or reheating (TgH), and to verify if the processed amorphous samples were created with or without thermal degradation. The melting temperature has little effect on the Tg value whereas the sugar was melted without thermal degradation. Thus, using this methodology the precise Tg value of amorphous sugars can be determined.
  143. In vitro Bioactivity of Chitosan/Poly (DL-LACTIDE) Composites
    Martel-Estrada, SA; Olivas-Armendariz, I ; Martinez-Perez, CA,Chacon-Nava, JG..
    Revista Mexicana de Ingeniería Qímica 11 (2012) 505-512 F. I. 0.578
    Porous composites scaffolds of different concentration of chitosan/ Poly(DL,lactide) were fabricated for tissue engineering applications by thermally induced phase separation and lyophilization techniques. The in vitro bioactivity evaluation of the scaffolds was carried out by analyzing the apatite layers produced on them using Simulated Body Fluid (SBF) as incubation medium. The interaction between functional groups in the composite was analyzed using differential scanning calorimetry. The apatite formation was analyzed using FTIR spectroscopy, Field Emission Scanning Electron Microscopy coupled to energy-dispersive electron X-ray spectroscopy and X-ray diffraction. The cumulative results obtained from IR spectra and SEM-EDS, suggest that the developed composites might have potential applications in tissue engineering.
  144. Evaluation of the Corrosion Resistance of Fe40Al60 Intermetallics in Molten Carbonate (Li+K).
    G. Pedroza, A. Martínez-Villafañe, M.A. Espinoza-Medina, M.A. Rivera and P.J. Sebastián..
    Journal of New Materials for Electrochemical Systems 15 (2012) 21-30 F. I. 0.533
    Alloys of the intermetallic material based on Fe40Al60 and the alloys formed with addition of Ag constitute a new alternative to improve the problems of corrosion resistance and electrical conductivity. The electrochemical characterization was employed to evaluate the corrosion resistance of the materials for being used as bipolar plates in molten carbonate fuel cells (MCFC). These characterizations were done under similar conditions as the working environment of the molten carbonate fuel cell (MCFC). The working environment of the standard molten carbonate fuel cell was simulated by the use of molten salts of 62 mol.% Li2CO3 and 38 mol.% K2CO3 at the temperature of 650 ºC. Alloys included Fe40Al60 with additions of 1, 3 and 5 weight % of Ag. The results obtained indicate that this material is promising for its use as bipolar plates in MCFC.
  145. Electrochemical Properties of Nanostructured AgxPt100-x/C Electrocatalyst for Oxygen Reduction Reaction
    Andrés Godínez-García, Alejandra García-García, H. Vladimir Martínez-Tejada, J.F. Pérez-Robles, O. Solorza-Feria.
    Journal of New Materials for Electrochemical Systems 15 (2012) 129-135 F. I. 0.533
    In this work, AgxPt100-x/C (x = 60, 80, 90 and 95) colloidal nanostructured electrocatalysts for the oxygen reduction reaction (ORR) were prepared by sequential reduction of AgNO3 and H2PtCl6 using an ultrasound-assisted colloidal method. The synthesized mate-rials were characterized by UV/Vis spectroscopy, XRD, EDS and HRTEM. In addition electrochemical measurements were performed using cyclic voltammetry (CV) and thin-film rotating-disk electrode (TF-RDE) technique in 0.5 M H2SO4 at room temperature. Results of the physical characterization showed ring-like morphology of the nanostructured catalyst with a size distribution in the range of 6-16 nm. From steady polarization measurements, the AgxPt100-x/C nanocatalysts showed electrocatalytic activity towards the ORR like that obtained for Pt/C catalyst under the same experimental conditions and also favored the multielectron (n=4e-) charge transfer process to water for-mation (i.e., O2+4H++4e-→2H2O).
  146. A study of bioflotation of chalcopyrite and pyrrhotite mixtures in presence of L. ferrooxidans
    Diaz-Lopez, CV (Diaz-Lopez, C. V.)1; Pecina-Trevino, ET (Pecina-Trevino, E. T.)2; Orrantia-Borunda, E (Orrantia-Borunda, E.)1.
    Canadian Metallurgical Quarterly 51 (2012) 118-125 F. I. 0.443
    The objective of this work was to determine the behaviour of chalcopyrite (Cp) and pyrrhotite (Po) in microflotation tests using pure minerals and mixtures in the presence of Leptospirillum ferrooxidans. Tests were carried out in the presence and absence of an unconventional collector, isopropyl ethyl thionocarbamate. The results indicate that chalcopyrite and pyrrhotite act differently alone than in a mixture which means the presence of pyrrhotite inhibits chalcopyrite recovery. For chalcopyrite, the flotation rate significantly increases in the presence of bacteria in the first 10 min of contact which is an indication of a first order kinetic equation. The results in the presence of an unconventional collector suggest that the interaction between mineral and thionocarbamate is chemical and not due to the galvanic effect.
  147. Simple Method to Synthesize Functionalized Carbon Nanotubes Employing Cobalt Nitrate and Acetone by Using Spray Pyrolysis Deposition Technique
    Gomez, JA; Marquez, A; Perez, A; Duarte-Moller, A..
    Advances in Materials Science and Engineering * (2012) doi: 10.1155/2012/258673 F. I. 0.414
    Recently alcohols and ketones have been employed to sensitize CNT by CVD. A study has shown the importance of the chemical nature of those carbon precursors on the characteristics of the CNT (carbon nanotubes) obtained. In the present work we show the influence of the catalyst employed on the synthesis of functionalized multiwall carbon nanotubes (MWCNTs) utilizing acetone as carbon source and cobalt nitrate Co(NO3)(2) as catalyst.
  148. Structure and Electromagnetic Properties of Bi1- xYxFe0.95Mn0.05O3 (x = 0.05, 0.075 and 0.10)
    J. Silva, A . Reyes, R. Castañeda, H. Esparza,H. Camacho, J. Matutes, and L. Fuentes.
    Ferroelectrics 426 (2012) 103-111 F. I. 0.391
    The effect of Y and Mn co- doping on the structural and electromagnetic properties of BiFeO3 is described. Multiferroic ceramics of Bi1- xYxFe0.95Mn0.05O3 (x = 0.05, 0.075 and 0.10) have been synthesized by the sol- gel method. Phase, structure and microstructure
    analyses were performed by scanning electron microscopy and X- ray diffraction followed by Rietveld analysis. Y saturation and consequent formation of a secondary phase was observed. Electric and magnetic measurements show that investigated doping
    is beneficial. Dielectric loses decreases, ferroelectric and ferromagnetic loops compare favorably with those corresponding with competing compositions.
  149. Steering magnetization with electric fields in a composite multiferroic chain
    A. Sukhov, P.P. Horley, C. L. Jia and J. Berakdar.
    Ferroelectrics 428 (2012) 109-115 F. I. 0.391
    We consider a multiferroic composite chain consisting of BaTiO3 on the one side and Fe on the other side with a linear magnetoelectric coupling at the interface induced by electrostatic screening. Employing the Landau-Khalatnikov equation for the ferroelectric polarization and the Landau-Lifshitz-Gilbert equation for the magnetization we study theoretically their mutual response to an external time-dependent electric field. We demonstrate for the sixth order ferroelectric potential for BaTiO3 and real parameters for Fe the full magnetization reversal in thin multiferroic chains due to the applied electric field.
  150. Application of the alpha spectrometry for the study of core sediment extracted in the San Marcos dam in Chihuahua
    C. Méndez García, R.García-Tenorio, M. Rentería Villalobos, María Elena Montero Cabrera.
    Revista Mexicana de Física 58 (2012) 234-237 F. I. 0.366
    La determinación de las actividades específicas de 210Po y uranio isotópico mediante espectrometría alfa fue realizada en un núcleo de sedimento de la Presa San Marcos. El objetivo de este trabajo fue analizar la distribución vertical de uranio isotópico y de 210Po así como el comportamiento de estos radionúclidos a lo largo del núcleo de sedimento recolectado en la presa San Marcos. La muestra fue dividida en 11 secciones. Para la determinación de 210Po y de uranio isotópico en cada una de las secciones se utilizó la técnica de extracción líquido-líquido con tributil fosfato (TBP). También se realizó una comparación entre la técnica del TBP y la técnica de cromatografía de extracción con resinas UTEVA para el uranio isotópico. Los resultados de las actividades específicas para 210Po muestran una tendencia decreciente a lo largo del núcleo, mientras que para uranio isotópico muestran una tendencia no monótona. Los resultados de las relaciones isotópicas entre el 234U y el 238U muestran estar cerca del equilibrio secular en cada una de las secciones del núcleo. La comparación entre las dos técnicas de extracción de uranio indica que se tiene un mayor rendimiento químico mediante empleando la técnica de UTEVA.
  151. Determination of uranium and polonium in Sparus aurata by alpha spectrometry
    M. Luna Porres, G. Manjón Collado, I. Díaz, M. Rentería, M.E. Montero Cabrera.
    Revista Mexicana de Física 58 (2012) 224-227 F. I. 0.366
    The aim of this study was optimizing conditions for the specific activities determination of some uranium-series radionuclides present in Sparus aurata by alpha spectrometry. Determinations of specific activities were conducted varying the type of digestion: acid attack on hot plate, controlled microwave digestion and acid attack after calcination of the sample. The latter procedure was applied only to the case of uranium isotopes determination. The variation in the isotope extraction method consisted of applying the techniques of liquid-liquid extraction using Tributyl phosphate (TBP) or chromatographic UTEVA resin. Results depending on the type of treatment given to the samples were compared based on obtained chemical yields. The results reveal a higher bioaccumulation of polonium in the liver sample, with activities of 0.809, 2.495 and 2.439 Bq kg¡1 fresh wt compared with the fillet. The best chemical yields for polonium were close to 60% for samples that were digested by microwave. In the case of uranium the best chemical yields, close to 80% for fillet, were obtained with a previous calcination of the sample and using the UTEVA resin.
  152. Radioactive hydrogeochemical processes in the Chihuahua-Sacramento Basin, Mexico
    J.C. Burillo1, M. Reyes Cortes1;2, M.E. Montero Cabrera1;¤, I. Reyes2, M.S. Espino2, M. Renterıa-Villalobos1, E.F. Herrera Peraza1.
    Revista Mexicana de Física 58 (2012) 241–248 F. I. 0.366
    The Chihuahua Basin is divided by its morphology into three main subbasins: Chihuahua-Sacramento subbasin, Chihuahua Dam subbasin and Chuviscar River subbasin. In the aquifers at the Sacramento subbasin, specific concentrations of uranium in groundwater range from 460 to 1260 Bq / m3. The presence of strata and sandy clay lenses with radiometric anomalies in the NW of Chihuahua Valley was confirmed by a litostatigraphic study and gamma spectrometry measurements of drill cuttings. High uranium activity values found in the water of some deep wells may correspond to the presence of fine material bodies of carbonaceous material, possible forming paleo-sediment of flooding or paleo-soils. It is suggested that these clay horizons are uranyl ion collectors. Uranyl may suffer a reduction process by organic material. Furthermore the groundwater, depending on its pH and Eh, oxidizes and re-dissolves uranium. The hydrogeochemical behavior of San Marcos dam and the NW Valley area is the subject of studies that should help to clarify the origin of the radioactive elements and their relationships with other pollutants in the watershed.
  153. Synthesis of Potassium and Calcium Uranovanadates, analogues of Carnotite and Metatyuyamunite Minerals
    J.L. Requena Yañeza, M. Reyes Cortesa;b, E. Torres Moyea, D. Lardizabala, H. Riverosc, M.E. Montero Cabreraa;¤.
    Revista Mexicana de Física 58 (2012) 253-257 F. I. 0.366
    The aim of this study was to develop a synthesis of metatyuyamunite (Ca(VUO6)2¢3-5H2O) and carnotite (KVUO6¢1-3H2O) under hydrothermal conditions. Also, crystals obtained from this synthesis were compared with crystals from melting method. The analyses of synthesis products were performed by X-Ray techniques. X-Ray Diffraction was used for both species identification, whereas Scanning Electron Microscopy was used to analyze their morphology and elemental composition. Both uranovanadates were positive synthesized under hydrothermal conditions; besides, their morphology presents particles agglomerates. Calcium uranovanadate agglomerates contain well-defined crystals, whereas potassium uranovanadate agglomerates consist in fine powder particles.
  154. Análisis de los transitorios de ruido electroquímico para aceros inoxidables 316 y Duplex 2205 en NaCl y FeCl
    Facundo Almeraya-Calderón, Francisco Estupiñan, Patricia Zambrano R, Alberto Martínez-Villafañe , Adán Borunda T., Rafael Colas O, Citlalli Gaona-Tiburcio..
    Revista de Metalurgia 48 (2012) 147-156 F. I. 0.202
    En este trabajo se muestran los resultados obtenidos de las mediciones de ruido electroquímico para diferentes materiales que exhiben corrosión por picaduras. Los transitorios presentados en las series de tiempo en corriente y en potencial, se correlacionan con el análisis superficial de microscopía electrónica de barrido (MEB). Las mediciones electroquímicas fueron realizadas a diferentes tiempos de exposición, para obtener una correlación. Los materiales usados fueron los aceros inoxidables 316 y dúplex 2205, inmersos en cloruro férrico (FeCl3) y cloruro de sodio (NaCl) como electrolitos. Los análisis por MEB, muestran que los transitorios observados en las series de tiempo, corresponden realmente con la actividad de la nucleación de picaduras desarrollada sobre la superficie de los electrodos.
  155. Corrosion Behavior of Fe3Al Intermetallics with addition of Lition, Cerium and Nickel in 2.5% SO2+ N2 at 900°C
    M.A. Luna-Ramirez*, J. Porcayo-Calderon, A. Martínez-Villafañe, J. G. González Rodríguez, and. J.G. Chacon-Nava..
    Revista de Metalurgia 48 (2012) 405-413 F. I. 0.202
    The corrosion behavior of Fe3Al-type intermetallic alloys with addition of 1 at. % cerium, lithium and nickel at high temperature has been studied. The various alloys were exposed to an environment composed of 2.5 % SO2+N2 at 900 °C for 48 h. For all the intermetallic tested, the corrosion kinetics showed a parabolic behavior. The alloy, which showed less corrosion rate, was the Fe3AlNi alloy, being Fe3AlCeLi the alloy with the highest corrosion rate. For the various alloys, energy dispersive X-ray spectroscopy analysis, EDS, on the developed scale only detected aluminum, oxygen, and traces of iron and cerium, suggesting the formation of alumina as main component. The intermetallic alloys showed oxide cracking and spalling. The intermetallic chemical composition played an important role in defining the oxide scale morphology and the extent of damage.
  156. Catalytic activity and X-ray photoelectron spectroscopy performance of Bi2MoxW(1-x)O6 solid-solutions
    R. Rangel, P. Bartolo-Pérez, E. Martínez, X. A. Trejo-Cruz, G. Díaz and D. H. Galván.
    Catalysis Science & Technology 2 (2012) 847-852    F. I. 0
    The present paper describes the results of the study of solid solutions of Bi2MoxW(1-x)O6, which were prepared by the route of solid-state reaction and tested for catalytic activity in the oxidation of CO into CO2. X-Ray photoelectron spectroscopy (XPS) was conducted to obtain information on the chemical composition, and with the use of Bi2MoO6 and Bi2WO6 synthesized standards, quantitative measures were obtained. Catalytic studies of the samples show that they possess high activity, as a change in the temperature of activation as a function of the sintering temperature with the Mo/W ratio was detected. Bi-Mo mixed oxides have synergistic effects on the oxidation of CO, making possible the full conversion at lower temperatures than compounds that contain only single phases. The work described here demonstrates that a solid solution can be more efficient in oxidation, compared with single oxides studied separately
  157. Quantitative XPS and catalytic activity studies of Bi2Mo(x)W(1-x)O6 solid solutions
    R. Rangel, P. Bartolo Pérez, E. Martínez, X. A. Trejo Cruz, G. Díaz and D. H. Galván.
    Catalysis Science & Technology 2 (2012) 847-852 F. I. 0
    The present paper describes the results of the study of solid solutions of Bi2MoxW(1−x)O6, which were prepared by the route of solid-state reaction and tested for catalytic activity in the oxidation of CO into CO2. X-Ray photoelectron spectroscopy (XPS) was conducted to obtain information on the chemical composition, and with the use of Bi2MoO6 and Bi2WO6 synthesized standards, quantitative measures were obtained. Catalytic studies of the samples show that they possess high activity, as a change in the temperature of activation as a function of the sintering temperature with the Mo/W ratio was detected. Bi–Mo mixed oxides have synergistic effects on the oxidation of CO, making possible the full conversion at lower temperatures than compounds that contain only single phases. The work described here demonstrates that a solid solution can be more efficient in oxidation, compared with single oxides studied separately.
  158. Uranium in the surrounding of San Marcos-Sacramento River environment (Chihuahua, Mexico)
    Marusia Rentería-Villalobos, Manuel Reyes Cortés, Juan Mantero, Guillermo Manjón, Rafael García-Tenorio, Eduardo Herrera, María Elena Montero-Cabrera..
    Thescientificworldjournal * (2012) 1--13 F. I. 0
    The main interest of this study is to assess whether uranium deposits located in the San Marcos outcrops (NW of Chihuahua City, Mexico) could be considered as a source of U-isotopes in its surrounding environment. Uranium activity concentrations were determined in biota, ground, and surface water by either alpha or liquid scintillation spectrometries. Major ions were analyzed by ICP-OES in surface water and its suspended matter. For determining uranium activity in biota, samples were divided in parts. The results have shown a possible lixiviation and infiltration of uranium from geological substrate into the ground and surface water, and consequently, a transfer to biota. Calculated annual effective doses by ingestion suggest that U-isotopes in biota could not negligibly contribute to the neighboring population dose. By all these considerations, it is concluded that in this zone there is natural enhancement of uranium in all environmental samples analyzed in the present work.
  159. An Optical Overview of Poly[mu(2)-L-alanine-mu(3)-nitrato-sodium(I)] Crystals
    Gallegos-Loya, E; Orrantia-Borunda, E; Duarte-Moller, A..
    Thescientificworldjournal * (2012) doi: 10.1100/2012/620189 F. I. 0
    Single crystals of the semiorganic materials, L-alanine sodium nitrate (LASN) and D-alanine sodium nitrate (DASN), were grown from an aqueous solution by slow-evaporation technique. X-ray diffraction (XRD) studies were carried for the doped grown crystals. The absorption of these grown crystals was analyzed using UV-vis-NIR studies, and it was found that these crystals possess minimum absorption from 200 to 1100 nm. An infrared (FTIR) spectrum of single crystal has been measured in the 4000-400 cm(-1) range. The assignment of the observed vibrational modes to corresponding symmetry type has been performed. A thermogravimetric study was carried out to determine the thermal properties of the grown crystal. The efficiency of second harmonic generation was obtained by a variant of the Kurtz-Perry method.
Ultima actualización: 06 Mayo 2013