Advanced Materials Research Vol. 976

Abstract: The crossed beam pulsed laser deposition technique was successfully used to prepare Co:TiO₂ thin films with different cobalt concentrations and a band gap as low as 2.0 eV. The aim of this work is to report the application of TiO₂ thin films modified with different amounts of cobalt (Co:TiO₂) as catalysts in the degradation of a malachite green (MG) solution as well as in solutions containing pharmaceutical wastes such as the analgesics diclofenac and naproxen. For catalyst activation an UV lamp with emission at 254 and 404 nm was used as the energy source. It was followed the decrease in the characteristic absorption band of the different polluted solutions over the reaction time. In general terms, the obtained results showed that samples containing cobalt exhibited better photocatalytic performance than the undoped TiO₂ films. An optimal cobalt content in the film was found that provided the highest degradation for the different solutions.

Abstract: En este trabajo una recuperación selectiva de Zn (II) y Fe (III) a partir de los medios de comunicación por sulfato de extracción líquido - líquido usando como agente de extracción se hizo el líquido iónico (trihexilo) tetradecylphosphonium bis-(trifluorometilsulfonil) imida (Cyphos IL 109). Se estudiaron varios parámetros, tales como: la naturaleza de la fase acuosa (HCl, H ₂ SO ₄ y NH ₃ / NH ₄ ), concentración de extractante, selectividad, y de re-utilización de líquido iónico. Los resultados experimentales mostraron que en medio amoniacal (NH ₃ / NH ₄ ) el agente de extracción (Cyphos IL 109) tiene una mayor afinidad por Zn (II) que el Fe (III), la obtención de la extracción de 98% a pH = 9,2. Por otra parte, en medio ácido sulfúrico (pH = 1,8), tenemos 96% de Fe (III) de extracción y sólo 4,8% de cinc. Por otra parte, se encontró que el aumento de la concentración de IL Cyphos 109 podríamos obtener mayores porcentajes de extracción de ambos metales de iones. El factor de separación (S _{Zn / Fe} = 110) indica la posibilidad de selectivamente de Zn (II) recuperarse de Fe (III) cuando están en la misma solución, que puede tener una amplia gama de aplicaciones en industrias tales como la galvanoplastia, donde estos metales están presentes a bajas concentraciones y pueden ser recuperados. También se observó que el extractante cargado puede ser reutilizado después de varios lavados con H ₂ SO ₄ (2,0 mol L ^-1 ).

Abstract: The main purpose of this research was to measure the resistance of insertion of a dental implant screw designed based on norm, made of the alloy Ti6Al4V [1], which was designed for the cancellous bone density (BD) molar region of the human jaw. The implants were embedded in the in a simulated bone polymer (Sawbone^®) [2] and were compared with specimens of the region molar of human jaw cadaver [3]. Using a digital torque wrench, the values of the insertion torque (IT) were calculated in the specimens with the implants inserted [4]. The minimum measured value was 25 Ncm or 0.25 Nm and the density of the maximum torque value measured was 110 Ncm or 1.1 in Nm recorded in the cadaver jawbone. The Pull Out Test (POT) was then carried out in order to determine the resistance of the insertion implant at the bone interface. The experimental results obtained for density, IT and resistance to insertion were then compared in order to determine the strength of fixation of the implant to the bone interface.

Abstract: This paper shows the results obtained from the synthesis of silver particles (nanoparticles and submicroparticles) on microfiltration membranes, evaluating the influence of surfactants impregnated in the membranes. Sub-micro particles and nanoparticles were obtained by the use of ascorbic acid as a reductant in a microfiltration system. Different shapes and sizes of the deposited silver particles on the membrane were obtained depending on the nature and concentration of the surfactant. The particles deposited over the membranes were characterized by scanning electron microscopy and energy- dispersive X-ray analysis.

Abstract: Strain-balanced quantum well solar cells (SB-QWSC) extend the photon absorption edge beyond that of bulk GaAs by incorporation of quantum wells in the i-region of a pin device. The strain-balanced quantum well solar cell benefits from a fundamental efficiency enhancement due to anisotropic emission from the quantum wells. This anisotropy arises from a splitting of the valence band due to compressive strain in the quantum wells, suppressing a transition which contributes to emission from the edge of the quantum wells. We have studied both the emission light polarized in the plane perpendicular (TM) to the quantum well which couples exclusively to the light hole transition and the emission polarized in the plane of the quantum wells (TE) which couples mainly to the heavy hole transition. It was found that the spontaneous emission rates TM and TE increase when the quantum wells are deeper. We have also demonstrated that the photo-generated carriers can escape from the QWs with near unity efficiency, via a thermally-assisted tunneling process, because gain is several orders greater than radiative recombination.

Abstract: Thepresent research analyzes the effect induced through addition of two zinc concentrations to composites based on recycled PET (polyethylene terephthalate), as a polymer matrix. Prior to mechanical assessment, the optimum grinding time was determined, namely, where the smaller particle size was generated (PET–420mm and Zn-5mm), that was 3 h. Subsequently, a comparison was done between two different blends, changing the zinc concentration 10 or 30 wt. %, from which the necessary test specimens for isothermal sintering were prepared and exposed at 256°C for 10, 15 and 20 minutes periods. These preliminary specimens permitted to value, for each zinc concentration, theirdensity, hardness (shore D) and water absorption. The best results were obtained with the samples sintered for the intermediate periods. The flexion and compression toughness were evaluated, where the blend with the higher toughness contained 30 wt. % Zn.

Abstract: In this work, they were produced and characterized cementing composites made with blast furnace slag replacement, for their use in the construction of oil wells. To this, slurries were prepared with a replacement of 20 and 30% slag, as well as a slurry with 100 % slag and a slurry with 100% H-cement were prepared. Starting materials were characterized by chemical analysis, X-ray diffraction and Fourier Transformed Infra Red. Slurries also were activated with sodium silicate in order to study theirs hydration kinetics, driving by isothermal calorimetry. These studies were complemented by the preparation of specimens of 4 X 4 X 16 cm to which they determine its compressive and bending strength during 2 and 28 days of curing. From the results it can be concluded that it was obtained a product that can be effectively used in the construction of oil wells.

Abstract: Hybrid organic-inorganic films are attractive materials for an alternative manufacture of photonic devices based on non-linear second-order optical processes. However, their efficiency and stability, closely related to their chromophores non-centrosymmetric orientation, still need some improvements. The use of nanostructures in this kind of materials gives place to a change in the chromophores surrounding medium; it can be used to improve the efficiency and the stability of the chromophores orientation in the films. In this work we show that some nanostructures are able to improve significantly the organic-inorganic SiO₂ films second-order non-linear optical responses. Two kinds of nanostructures were studied: some nanostructures were just immersed, but the other ones were spontaneously induced in the films. The immersed nanostructures were multi-walled carbon nanotubes and the spontaneously induced nanostructures were formed in the films by means of surfactants self-assembly. The films were synthesized by the sol-gel method and all of the films were doped with Disperse Red 1 (DR1) dipolar chromophores. The induced nanostructures were lamellar and hexagonal long-range ordered nanostructures, detected by X-ray diffraction (XRD). The second-order non-linear optical properties of the films were studied in resonance through Corona poling assisted second harmonic generation. The results show significant improvements, for some kinds of nanostructures, in the non-linear optical responses of the films. In particular, those films containing Triton X-100 showed, at a poling temperature of 120°C, an improved second-order non-linear coefficient d₃₃ with respect to equivalent non-nanostructured films; the d₃₃ value of those films, determined by the Maker fringes technique, was equal to 21.4 pm/V.

Abstract: Al₂O₃/Ti/TiO₂-functional materials with compositional gradient were fabricated through air oxidation of Al₂O₃/Ti ceramics. To obtain the desired functional material, the Al₂O₃/Ti ceramic was subjected to a heat treatment for 24 hours at temperatures of 500°C, using an electric furnace with air atmosphere. After ceramic oxidation, observations in the transversal area of the microstructure of the new material obtained show a thin film of about 50 microns thick of a combination of constituents that with the aid of EDS analysis were identified as Al₂O₃/TiO₂. In addition to these observations, microhardness measurements performed on the transversal area of the sample by its surface and towards to the center of this, indicate a surface hardness higher than in the center of the sample, where it was identified by EDS an Al₂O₃/Ti compound. This led to conclude that it was obtained at the end of processing an Al₂O₃/Ti/TiO₂-functional material with compositional gradient.

Abstract: Rutile surface has been modeled in order to study its electronic properties as well as to determine its surface chemical reactivity. There have been constructed 10 different rutile structures, from a 6 atoms cluster (for the smallest) to a 356 atoms cluster (for the biggest). It was calculated for each cluster some physical parameters which are related to the electronic properties, such as work function, band gap, and density of states (DOS), in order to analyze the tendency of the cluster properties with the increase of atoms. From the data obtained, it was determined the Electronic Unit Cell (EUC), which refers to the modeled structure for what the electronic and reactivity properties of the system does no change, from clusters with different number of atoms. From the rutile EUC cluster it was determined its band gap with a value of 3.28 eV, which agreed with the experimental value of 3.0-3.1 eV. Furthermore, it was performed a reactivity surface study, which comprised the analysis of reactivity descriptors such as ionization potential, electronic affinity, total hardness, electronic chemical potential, electrophilicity and electronegativity. All theoretical calculations were performed using the semiempirical PM7 included in the 2012 version of MOPAC and the surfaces were modeled from crystallographic data.