Ciudad Juárez, Mexico
Ciudad Juárez, Mexico

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Dominguez-Rios C.,CIMAV | Hurtado-Macias A.,CIMAV | Torres-Sanchez R.,CIMAV | Ramos M.A.,Institute Ingenieria y Tecnologia | Gonzalez-Hernandez J.,CIMAV
Industrial and Engineering Chemistry Research | Year: 2012

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. © 2012 American Chemical Society.


Vilchis-Nestor A.R.,Autonomous University of Mexico State | Lugo-Medina E.,IT de Los Mochis | Carrillo-Castillo A.,Institute Ingenieria y Tecnologia | Quevedo-Lopez M.A.,University of Texas at Dallas | Olivas A.,National Autonomous University of Mexico
Scanning | Year: 2015

In this work, the influence of substrate on the morphology of ZnS thin films by chemical bath deposition is studied. The materials used were zinc acetate, tri-sodium citrate, thiourea, and ammonium hydroxide/ammonium chloride solution. The growth of ZnS thin films on different substrates showed a large variation on the surface, presenting a poor growth on SiO2 and HfO2 substrates. The thin films on ITO substrate presented a uniform and compact growth without pinholes. The optical properties showed a transmittance of about 85% in the visible range of 300-800 nm with band gap of 3.7 eV. SCANNING 37:389-392, 2015. © 2015 Wiley Periodicals, Inc.


Diaz-Moreno C.A.,CIMAV | Farias-Mancilla R.,Institute Ingenieria y Tecnologia | Matutes-Aquino J.A.,CIMAV | Elizalde-Galindo J.,Institute Ingenieria y Tecnologia | And 3 more authors.
Journal of Magnetism and Magnetic Materials | Year: 2014

Ferromagnetism is observed in LiNiO3 nanocrystals exposed to a reducing atmosphere intended to create oxygen vacancies. The existence of vacancies is confirmed by measuring the oxygen depletion across the selected nanoparticles by TEM. The magnetism shows no temperature dependence in the range of 4-300 K. The density functional theory was used to perform spin polarized electronic structure calculations for LiNiO3 with and without oxygen vacancies. The calculated magnetic data qualitatively support the observed magnetic behavior. © 2013 Elsevier B.V.


Lastra G.,National Autonomous University of Mexico | Carrillo-Castillo A.,Institute Ingenieria y Tecnologia | Quevedo-Lopez M.A.,University of Texas at Dallas | Quevedo-Lopez M.A.,University of Sonora | Olivas A.,National Autonomous University of Mexico
Journal of Electronic Materials | Year: 2014

Zinc sulfide (ZnS) thin films have been grown by chemical bath deposition (CBD) using different zinc sources on a silicon nitride (Si3N4) substrate in an alkaline solution. The zinc precursors used were zinc acetate, zinc nitrate, and zinc sulfate. The structural and optical characteristics of the ZnS thin films obtained were analyzed. The morphology of the surface showed that the films were compact and uniform, with some pinholes in the surface depending on the zinc source. The most homogeneous and compact surfaces were those obtained using zinc nitrate as the zinc source with a root-mean-square (RMS) value of 3 nm. The transmission spectra indicated average transmittance of 80% to 85% in the spectral range from 300 nm to 800 nm, and the optical bandgap calculated for the films was around 3.71 eV to 3.74 eV. © 2014 The Minerals, Metals & Materials Society.


PubMed | National Autonomous University of Mexico, IT de Los Mochis, University of Texas at Dallas, Autonomous University of Mexico State and Institute Ingenieria y Tecnologia
Type: Journal Article | Journal: Scanning | Year: 2016

In this work, the influence of substrate on the morphology of ZnS thin films by chemical bath deposition is studied. The materials used were zinc acetate, tri-sodium citrate, thiourea, and ammonium hydroxide/ammonium chloride solution. The growth of ZnS thin films on different substrates showed a large variation on the surface, presenting a poor growth on SiO2 and HfO2 substrates. The thin films on ITO substrate presented a uniform and compact growth without pinholes. The optical properties showed a transmittance of about 85% in the visible range of 300-800nm with band gap of 3.7eV.


Ramos M.,Institute Ingenieria y Tecnologia | Ramos M.,University of Texas at El Paso | Ferrer D.,University of Texas at Austin | Martinez-Soto E.,University Metropolitana | And 4 more authors.
Ultramicroscopy | Year: 2013

Hydrotreatment catalytic operations are commonly performed industrially by layered molybdenum sulfide promoted by cobalt or nickel in order to remove heteroelements (S, N, O) from fossil fuels and biofuels. Indeed, these heteroelements are responsible of the emission of pollutants when these fuels are used in vehicles. In this respect, previous studies made by our research group have shown that the active phase under steady state conditions is partially carbided while strong bending effects of MoS2 slabs were also observed. However, up to now, the morphology of the resulting Co/MoSxCy carbided catalyst has not been fully characterized. In the present study, for the first time, a chemical reaction between the carbon content of a TEM Cu/C grid and a freshly sulfide Co/MoS2 catalyst was in situ observed at 300°C and 450°C by HRTEM experimental techniques at ~10nm of resolution. Results indicate that bending of MoS2 layers occurred due to carbon addition on MoS2 edge sites, as observed in stabilized catalysts after HDS reaction. Using a silicon grid, only cracks of MoS2 slabs were observed without bending effect confirming the role of structural-carbon in this change of morphology. © 2012 Elsevier B.V.


Gonzalez G.A.,University of Texas at El Paso | Alvarado M.,University of Texas at El Paso | Ramos M.A.,Institute Ingenieria y Tecnologia | Berhault G.,CNRS Research on Catalysis and Environment in Lyon | Chianelli R.R.,University of Texas at El Paso
Computational Materials Science | Year: 2016

Transition state computational studies of the sulfur removal from dibenzothiophene (DBT) molecule have herein been performed considering the Co9S8/MoS2 interface existing on unsupported Co/MoS2 catalysts. The linear synchronous transit (LST) and quadratic synchronous transit (QST) methods integrated in a density functional theory (DFT) program such as Dmol3 were used for the calculations of energy barriers of the transition states. Three different configurations present on the Co9S8/MoS2 interface have been envisaged as possible catalytic sites: sulfur-sulfur (S, S) sites, and molybdenum-sulfur (Mo, S) and molybdenum-molybdenum (Mo, Mo) edge sites. This study revealed that the (Mo, Mo) edge site is the most catalytically active site for the hydrodesulfurization (HDS) reaction followed by the (Mo, S) edge site while the (S, S) site shows almost inertness for the HDS reaction. This information allows us to propose clues to design new catalysts based on bulk Co9S8/MoS2 phases with higher efficiency by increasing the proportion of (Mo, Mo) edge sites. © 2016 Elsevier B.V.


Lopez H.,University of Texas at El Paso | Gonzalez G.,University of Texas at El Paso | Ramos M.,Institute Ingenieria y Tecnologia | Chianelli R.R.,University of Texas at El Paso
Materials Research Innovations | Year: 2016

The Bridgman and the chemical vapour transport are crystal growth techniques that are often used to produce high-quality fully dense crystals, but prove impractical for the evaluation of a large number of new compounds. Uniaxial dry-cold pressing (UDCP) is a robust and time-efficient method to agglomerate particulate solids and the work presented here explored it as an alternate sample preparation procedure that will enable rapid thermoelectric evaluation of a large number of new compounds. Samples fabricated by different methods using the chalcogenides Bi2Te3 (reference compound) and TiS2 (experimental compound) had their Seebeck coefficients and their electrical conductivities measured. It was observed that UDCP pellets generated a good Seebeck coefficient when compared to their monocrystalline counterparts. Manufacturing procedures were developed for fabricating UDCP samples of Bi2Te3 and TiS2. The UDCP is a novel technique for the evaluation of new compounds for thermoelectric applications. © 2016 Informa UK Limited, trading as Taylor & Francis Group.


Zarei-Chaleshtori M.,University of Texas at El Paso | Correa V.,University of Texas at El Paso | Lopez N.,University of Puerto Rico at Mayaguez | Ramos M.,University of Texas at El Paso | And 4 more authors.
Catalysts | Year: 2014

We present the chemical synthesis of hexaniobate nanotubes using two routes, (1) starting material K4Nb6O17 and (2) parent material of H4Nb6O17 via ion exchange. The as-synthesized materials were exfoliated by adjusting the pH to 9–10 using tetra-n-butylammonioum hydroxide (TBA+OH−), leading to a formation of hexaniobate nanotubes. In order to understand morphology a full characterization was conducted using SEM, HRTEM, BET and powder-XRD. The photocatalytic activity was evaluated using photolysis method using Bromocresol Green (BG) and Methyl Orange (MO) as model contaminants. Results indicate a nanotube porous oxide with large porous and surface area; the photocatalytic activity is about 95% efficient when comparing with commercial TiO2. © 2014 by the authors; licensee MDPI, Basel, Switzerland.


PubMed | Institute Ingenieria y Tecnologia
Type: | Journal: Ultramicroscopy | Year: 2013

Hydrotreatment catalytic operations are commonly performed industrially by layered molybdenum sulfide promoted by cobalt or nickel in order to remove heteroelements (S, N, O) from fossil fuels and biofuels. Indeed, these heteroelements are responsible of the emission of pollutants when these fuels are used in vehicles. In this respect, previous studies made by our research group have shown that the active phase under steady state conditions is partially carbided while strong bending effects of MoS2 slabs were also observed. However, up to now, the morphology of the resulting Co/MoSxCy carbided catalyst has not been fully characterized. In the present study, for the first time, a chemical reaction between the carbon content of a TEM Cu/C grid and a freshly sulfide Co/MoS2 catalyst was in situ observed at 300 C and 450 C by HRTEM experimental techniques at ~10 nm of resolution. Results indicate that bending of MoS2 layers occurred due to carbon addition on MoS2 edge sites, as observed in stabilized catalysts after HDS reaction. Using a silicon grid, only cracks of MoS2 slabs were observed without bending effect confirming the role of structural-carbon in this change of morphology.

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