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In this study, the microstructural characterization of a superplastic Zn-Al-Ag alloy (72, 24, and 4 in % wt. respectively) by using spectroscopy analysis techniques was obtained. The X-Ray Fluorescence (XRF), Scanning Electron Microscope (SEM) and X-Ray Diffraction (XRD) techniques were used. The main objective of this alloy development is to improve its super-plasticity property and increases its corrosion resistance in acid rain environments. The effect of small grain microstructure of the alloy obtained at the end of the fabrication process improved the super-plasticity behavior. The result of the fabrication process was observed by the characterization of crystallographic phases (morphology, size and distribution) and the chemical composition. The obtained results by XRF shown that Zn was the higher proportion element, in addition the Ag (4% wt.) addition to Zn-Al base alloy improves the grain refinement, as was observed by the SEM characterization. The Ag3Al and AgZn3 intermetallic compounds homogeneously dispersed were observed in the microstructure of the Zn-Al solid solution phase. The size grain observed after the rolling process was less than 10 µm, and it was associated to one of the main characteristics of super-plasticity properties. The XRD analysis results corroborated the present phases in the alloy, as was identified with the SEM and EDS characterization.
The effect on the mechanical properties at room temperature of Li and Ag additions to the Fe–Al (40 at.%)-based alloy produced by conventional casting were evaluated in this work. Alloying elements were added into a previously molted Fe–(40 at.%) aluminum-based alloy, stirred, and then cast into sand molds to directly produce tensile specimens. To determine the mechanical properties, tensile tests and hardness measurements were performed. The additions of both Ag and Li showed an increase in ductility and tensile strength of the intermetallic alloys. In addition, hardness was substantially increased with the Li addition. Lithium additions promoted a solid solution hardening, whereas 3 at.% of Ag additions promoted ductility due to a microstructural modification and to the formation of a soft Ag3Al phase. Characterization by both optical and electronic microscopy, energy dispersive spectroscopy microanalysis, and x-ray diffraction supported the mechanical characterization.
The study of corrosion behavior of polyurethane/nanohydroxyapatite hybrid coating in aerated Hank solution at 25 °C by Potentiodinamic and Electrochemical Impedance techniques was realized. The nanohydroxyapatite (nHA) powders were synthesized by ultrasonic assisted co-precipitation wet chemical method and then mixed with pure polyurethane (PU) during the polymerization. Results were supported by SEM morphologic characterization. Results showed that good corrosion resistance of hybrid coating, showing small corrosion product layer formation. Corrosion mechanisms are affected by an increasing of polarization resistance, promoting decreasing in the corrosion rates. Diffusion of ionic species was the governing mechanism in the corrosion behavior of polyurethane/nanohydroxyapatite hybrid coating.
The historical monuments such as cathedrals, public buildings and so on, are a fundamental part of artistic heritage of a country. They reflect, ultimately, much of its culture and history. For several decades, their aspect has been seriously changed by graffiti, which clearly endangers their preservation state and causes loss of their esthetic appearance and historic value. This damages seriously the self-esteem of residents who witness the continued and strong degradation of their cultural heritage. The aim of this work is to study the removal of graffiti from a characteristic stone which is used in Morelia (México) as the raw material for architectural monuments, using a high power diode laser treatment. We concluded that continuous wave regime leads to better results than modulated wave regime; additionally, a two laser passes process demonstrated a high performance.
Osteoarthritis is a very complex illness of the joints that affects cartilage and subcondral bone. At the last years, researching has been focused in the development and characterization of composite materials, evaluating their structural properties. Some o those composite materials are constituted by organic and inorganic compounds forming hybrids. These materials can improve their properties due to the interaction of reinforcement hard particles in the polymeric matrix. The interest on the composite biomaterials has been increased on the biomedical applications such as tissue regenerating based in synthetic polymers with biodegradable and biocompatible properties whose can be reinforced by calcium phosphates. In this sense, hydroxyapatite [Ca10(PO4)6(OH)2] is often used for biological implants due its mineral phase similitude with bone microstructure and tissue compatibility. Similarly, polylactic acid (PLA) is a used polymer for implant applications due physicochemical and biocompatibility properties, and short degradation time also. In order to obtain a composite that can be used as a regenerating material on the osteoarthritis problem, in this work a (90/10 wt.%) polylactic/hydroxyapatite hybrid composite was produced by chemical synthesis and characterized by X-ray diffraction, SEM, FT-IR and TGA/DSC techniques.
The isothermal oxidation-sulfidation of Fe-40Al based intermetallics alloys in N2/SO2 gas mixture at 625, 700 and 775°C were evaluated. Fe40Al, Fe40Al+0.1B, Fe40Al+0.1B+10Al2O3 alloys were produced by atomization and deposition. Isothermal gas exposition was reached during 48 hours. FeAl based alloys showed good sulfidation resistance, presenting both small weight gain and weight change fluctuations. At 625°C, the Fe40Al+0.1B alloy had the biggest weight gain; on the other hand the Fe40Al alloy exhibited the biggest sulfidation resistance. At 700 and 775°C, the Fe40Al+0.1B alloy presented the smallest weight gain, however Fe40Al alloy presented higher weight gain, that is to say, the smallest sulfidation resistance at those temperatures. The variation in the weight gain curves were discussed in terms of formation and detachment of sulfides, and by local attack on the alloy surface as the temperature increasing. The results are supplemented with characterization by SEM and analysis of X-rays dispersion.
After some experimental results that indicated that HA is able to growth in an epitaxial way on the surface of OCP, it has been suggested that the central dark line (CDL) observed in the nanometric-sized grains of human tooth enamel corresponds to a one-unit-cell-thick layer of octacalcium phosphate (OCP). Based on this consideration, in this work we propose a model for CDL and we carried out the chemistry and structural analysis of the CDL with high resolution microscopy techniques such as Electron Energy Loss Spectroscopy (EELS) and Z-contrast (HAADF) with the aim of find the agreements and/or differences between the human tooth enamel HA and its CDL.
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