Applied Mechanics and Materials Vol. 377

Abstract: High quality VO₂ films have been successfully deposited by pulsed magnetron sputtering. In the preparation of vanadium dioxide films, the stoichiometry, structure and orientation of vanadium dioxide can be influenced by the process parameters. In this study, sputtering power and oxygen partial and substrate temperature were controlled accurately during experiment. Between X-ray diffraction and X-ray photoelectron spectroscopy were used to analyze the composition, phase structure, crystalline and valence state of the film. Atomic force spectroscopy was used to identify the film surface morphology. Electrical transition characteristics were also measured by four probes. Thermal radiative property was measured on a Calorimetric Emissometer. These investigations reveal that VO₂ films have high purity, monophase and the sharp variation of resistance of films from semiconductor to metal state at 293K~373K temperature. Thermal emissivity of VO₂ films vary widely from 0.82 to 0.35, which can meet requirement of future space thermal design.

Abstract: In order to improve the wear resistance of Al-Si alloys, the electro deposition of Ni-Co-P/Si₃N₄ coating on a hypereutectic Al-Si casting alloy was studied in this paper. The thickness, hardness, surface morphology, composition, adhesive force and wear resistance of Ni-Co-P/Si₃N₄ coating were measured by optical microscope, micro-hardness tester, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), adhesive attraction scratcher and abrasion tester. It was shown that Si₃N₄ particulates were uniformly distributed in the composite coating. And the effect of process parameters, such as electric current density, temperature, PH, plating time and component of electroplating bath,were obtained. The wear resistance of the coating was improved with the increase of hardness and the content of Si₃N₄ in the coating. It was also improved by decreasing electric current density. The adhesion of the coating was poor for increasing the content of P and Co in the coating. At the same time, the coating was hard, friable, and easy to be broken with the decrease of temperature.

Abstract: Based on the principle of maximum entropy method (MEM), the particle swarm optimization (PSO) with inertia weight factor is efficiently applied for the orientation distribution function (ODF) representation on textured materials in this article. By this optimized algorithm with a faster rate of convergence, more appreciable calculation results have been obtained for complete orientation distributions (C-ODF) of the designated deep-drawing IF steel sheets with macro cubic-orthogonal symmetry. With reference to data processing, there need no more assumptions except that the system entropy approaches maximum. The calculation results are irrelevant to the sample compositions, texture components or their initial orientation distributions derived from three pole figures.

Abstract: This paper prepared polyamide (PA)/polyacrylonitrile (PAN) thin-film composite hollow fiber membranes via interfacial polymerization by using triethylenetetramine (TETA) and trimesoyl chloride (TMC) as the monomers and asymmetric PAN hollow fiber membrane as the substrate. The effect of hydrolysis of asymmetric PAN hollow fiber membranes on the chemical properties was investigated. The results showed that the chemical properties of PAN hollow fiber membranes were affected by hydrolysis. Moreover, the effects of PA thin film polymerized onto the inner and outer surface of asymmetric PAN hollow fiber membranes on pervaporation performances were also investigated. The results also revealed that the interfacial polymerized PA/PAN composite hollow fiber membranes that were polymerized onto the outer surface of asymmetric PAN hollow fiber membranes can be used in the pervaporation of aqueous alcohol solution.

Abstract: AZ91 magnesium alloy was fabricated by powder metallurgy. The effects of sintering temperature on the relative density, hardness and tensile strength were investigated. The microstructure of the material was observed by scanning electron microscopy (SEM) and Energy Disperse Spectroscopy (EDS). The study found that the best sintering temperature is 550°C under the vacuum hotpressing, and at this sintering temperature the relative density can reach to 98.3%. SEM and EDS show that the sintering microstructure of the alloy is composed of α-Mg solid solution and the second phase β-Mg₁₇Al₁₂. Under the 550°C sintering temperature, Volume diffusion is the mainly sintering form, and produced more β-Mg₁₇Al₁₂ which is dispersively distributed on the grain boundary, and improves the hardness of alloy by second-phase strength.

Abstract: In this study, the structure and properties of bisphenol A polycarbonate (BPA-PC) after UVB-313 radiation were investigated. When BPA-PC was exposed to ultraviolet (UV), this polymer showed two different degradation mechanisms: photo-Fries rearrangement and photo-oxidation. The interpretation of the observed chemical degradation was based on attenuated total reflection IR (ATR). Gel permeation chromatograph (GPC) measurements indicated that the molecular weights of exposed surface sample were decreased with increasing of irradiation time, but the molecular weights of bulk polymer did not decrease severely. Namely, the degradation of BPA-PC was a surface phenomenon, which only extended about several micrometers into the exposed surface. This also could explain why the mechanical properties of samples showed no change. In addition, photo-induced yellowing of the aged PC was aggravated with the irradiation time prolonging, but no remarkable changes of light transmission have been observed.

Abstract: To study the effect of different pH on degradation products of tinidazole pills and direct preparation of tinidazole pills, Tinidazole pills were prepared and the solution of different pH was compounded. The tinidazole content of pills and degradation products were determined by being heated at 80°C via high performance liqud chromatographic (HPLC). The number and concentration of tinidazole pills were increased with the increase of temperature and pH. Tinidazole pills in acidic conditions with the pH value within 4~5 were more stable than in neutral and alkaline conditions. It was shown that shortening the melting time and keeping pH value within 4~5 were in favor of preparation and assurance of pills quality.