Advanced Materials Research Vol. 811

Abstract: The Al alloy is environmental friendly, easy to recycle, and provides a high added value to fishing boats. Aluminum alloy do not corrode due to the formation of an anticorrosive passive film, such as Al₂O₃ or Al₂O₃3H₂O, which resists corrosion in neutral solution. In seawater, however, Cl^- ions destroy this passive film. We investigated on several electrochemical tests undertaken to determine the optimum conditions in seawater for corrosion protection of casted AC7AV aluminum alloy. The components of casted AC7AV aluminum alloy are similar with Al-Mg alloys (5xxx series) which are used for ship. Result of electochemical experiment, the optimum protection potential range with regards to hydrogen embrittlement and stress corrosion cracking was determined to lie between-1.3 and-0.7 V(vs Ag/AgCl).

Abstract: nanocopper oxides (Cu₂O) materials, which received much attention in recent years, have many promising applications in various areas. The nanocopper oxides were prepared by the reduction of aqueous cupric acetate, with hydrazine as a reductant. The nanocopper oxides Collosol would be very stability when coated by Oleic acid, the oleic acid coats Cu₂O nanoparticle through chemical reaction between carboxyl at one end of oleic acid molecule. All the samples were characterized by XRD, SEM and FTIR analysis.

Abstract: High purity aluminium powder was sintered in a dilatometer in flowing high purity nitrogen. The distinct shrinkage segments observed on the dilatometry curves were the basis of experiments consisting of interrupted sintering. In this way compacts with microstructure frozen at different steps of sintering cycle were produced. Optical microstructure examinations and LECO analysis of nitrogen content showed the development of aluminium nitriding. Additionally, X-ray diffraction was used to examine phases appearing in the system investigated. Microstructure analysis of structural components revealed evidence that isothermal sintering proceeds in the presence of a liquid phase, despite taking place below the melting point of aluminium. It seems that aluminium nitrogen interactions are responsible for the appearance of this phase, which is accompanied by extensive shrinkage.

Abstract: In this paper the detailed analysis of thermal behavior of electrical resistivity of Co₈₂Fe₄Cr₃Si₈B₃ amorphous alloy is made. It has been shown that within temperature range 23⁰С <T< 560⁰С the structure of the alloy keeps its amorphous character and only a slight changes occurred. A high temperature (above room temperature) resistivity minimum was found at 160°C. This feature was related with Curie temperature of the alloy. It has been shown that change of electrical resistivity behavior at 350°C can be explained by reaching the Debye temperature of the alloy.

Abstract: Acoustic microscopes can be used to measure Rayleigh and longitudinal wave velocities in a specimen at microscopic resolution. These velocities are deduced from the analysis of the so-called acoustic signatures or V(z) curves. Such curves are obtained by recording the output signal, V, as the specimen is defocused along the z axis of the lens. In this context, we investigate Co-Additives effects on reflectance functions, R(θ) and acoustic signatures. The elastic properties of Lithium cobalt mixed ferrites of different compositions from the experimentally and simulation observed that the values of longitudinal wave velocities vary from 5072 m/s to 6833 m/s whereas transverse velocities from 3084 m/s to 4105 m/s. The variation of the elastic moduli with composition was interpreted in terms of the binding forces between the atoms.

Abstract: The V₂O₅/TiO₂ catalyst is used to control chlorobenzene and NO simultaneously in NH3-SCR reaction. XRD characterization of the catalyst is carried out. The effect of NO and NH₃ on the chlorobenzene catalytic conversion is studied and opposite results are concluded. NO slightly increases the catalytic conversion rate of chlorobenzene under 250oC while NH3 obviously declines the chlorobenzene catalytic degradation at 300oC. The best coupled control efficiency can be achieved at 350 oC.

Abstract: Alloys from austenitic and ferritic stainless steel found to be satisfactory for a great many applications. However, for applications that require higher levels of strength and hardness from the martensitic grades are frequently specified. Martensitic stainless steels offer significantly higher strengths but have to low ductility. For this reason for application where high levels of strength and a moderate ductility is required, the precipitation strengthened stainless steels are often considered. One of the most popular alloy of this kind of stainless steel is 17-4 PH. The aim of the present paper was to examined the influence the process parameters in conventional powder metallurgy processing on the mechanical properties of the 17-4 PH alloy in both as-sintered and heat treated conditions. In was found that temperature of aged is a very sensitive parameter for obtained high strength and acceptable ductility.

Abstract: The oxidation characteristics of WC-20%TiC-10%Co sintered carbides were studied by oxidizing at 700, 800 and 900 °C for 3 h in air. The samples oxidized fast with large weight gains, displaying quite poor oxidation resistance. The formed oxide scales that consisted primarily of CoWO₄, WO₃, and TiO₂ were porous, and prone to cracking.

Abstract: SiO_x based composite powders were fabricated by flame hydrolysis synthesis method employing an oxygen-hydrogen flame torch. The SiCl₄ gas was used as a precursor and carried into the central tube of the torch by dry Ar gas. As-synthesized SiO_x based composite powders had spherical shape with the size of about 3040 nm. To control the structure of the incompletely oxidized SiO_x based composite powders, the as-synthesized SiO_x based composite powders were heat-treated under 5 % H₂ and 95 % Ar mixed gas atmosphere at a temperature of 1000 °C to 1400 °C for 3h. The properties of as-synthesized and post heat-treated SiO_x based composite powders at various temperatures were investigated by XRD, TEM, SEM, FT-IR and XPS analysis. And through the post-treatment effects, structural controlled the incomplete oxidized SiO_x based composite powders. The formed particles in SiO_x based powders had sphere shape and the size of 30 ~ 40 nm. TEM analysis revealed that the amorphous phase and crystalline phase were mixed in SiO_x based composite powders by post-heat treatment. And the Si and SiO₂ crystalline phases were detected in amorphous phase.

Abstract: The term cold-drawing of tubes refers to forming when the final material (a tube) is formed in a pipe bell and its vertical cross-section is smaller, the tube wall is thinner or thicker and its length is greater. Steel is most commonly the final material. The forming proceeds in a few draws which depend on the final tube dimension. The selection of relative reduction for particular diameters plays an important role because an unbalanced reduction causes stress, and therefore also deformation or cracks during drawing. The technological parameters are: rolling temperature, de-burring of tube ends, the reduction, which determines the dimensions of the forming tools, the optimal chemical modification, the speed of forming on the drawbenches, and the method of tube drawing.