Advanced Materials Research Vols. 299-300

Abstract: Taking the hypereutectic Al-Si alloy as the research object, the fading characteristics of Al-22% Si alloy at different pulse temperatures are investigated in this paper in order to analyze the mechanism of electrical pulse modification to the alloy. We can get the conclusion by observing the microstructure of the sample, measuring the microhardness and calculating the volume fraction and the average size of primary silicon: at different pulse temperatures, the effect of electric pulse modification is fading with static duration prolonging; meanwhile, with the temperature upward, the modification effect and fading trends to be weak, which indicates the best pulse temperature is one of the important factors to influence the modification effect.

Abstract: In this paper, the effects of electric pulse on solidified structure and graining process of near eutectic Al-5%Cu alloy have been investigated during solidified process. It was treated with different pulse voltages at 740°C in this experiment, and established the cooling curve. The results show that the improvement of alloy casting macro-segregation and solidification structure refinement by electric pulse discharging; The change of the solidified casting structure has a preferable coincidence relation with the change of the cooling curve, and analysis of the cooling curve shows that the best granular effect has a maximal supercooling on the curve.

Abstract: Based on the empirical electron theory of solid and molecule, the valence electron structures(VESs) of graphite, CaS and MnS in cast iron are calculated, their bond-forming energy F of the structure unit and bond-forming energy E of the crystal plane are defined and calculated. Combined with the nucleation theory of the liquid metal, F and E are applied to analyze the thermodynamics condition of graphite heterogeneity nucleation in undercooling liquid of case iron, i.e., GL-F_G>GL-FH,>. According to the coincidence lattice model of large-angle grain boundary used commonly in modern times, the corresponding structural condition is analyzed, i.e., the crystal structure of graphite should have the better lattice contract ratio with the crystal structure of its annexed heterogeneous particles.

Abstract: Palladium composite membranes have been prepared by improved electroless plating on macroporous α-Al₂O₃ tubes. TS-1 zeolite layer was introduced in the palladium composite membrane to modify macroporous α-Al₂O₃ tubes and prevent the diffusion between Pd and alumina. The detailed microstructure and morphology of the Pd-TS-1 composite membrane were examined by SEM and XRD. Moreover, gas permeation performance was tested at the temperature range of 623~773K. Results showed that the H₂ permeance and H₂/N₂ ideal selectivity for Pd-TS-1 composite membrane could be up to 3.7×10^-7 mol·m^-2·s^-1·Pa^-1 and 310 at 773K, respectively.

Abstract: The amorphous Fe₇₈Si9B13 alloy was treated by low frequency pulse magnetic field (LFPMF). The microstructure was observed by Mössbauer spectroscopy and Transmission Electron Microscope. The activation energy of nanocrystallization of amorphous alloy Fe78Si9B13 treated by low frequency pulse magnetic field was determined by differential scanning calorimetry (DSC). The results indicated that the activation energy was decreased from 433.6kJ.mol-1 to less than 200kJ.mol-1 after LFPMF. The nucleating rate of α-Fe(Si) was increased and there was only single phase α-Fe(Si) crystalline formed.

Abstract: Yttrium Lanthanum Oxide transparent ceramics were fabricated with (Y_0.9La_0.1)₂O₃ powders prepared by different methods. The growth characteristics, physical and chemical properties of the powders were investigated. The wet-chemical composite powders’ particle size was inhibited by La₂O₃ at high temperature treatment, therefore smaller than that of powders by solid-state reaction method. During the solid-state reaction between La₂O₃ and Y₂O₃ at temperature of 700~1100°C, La₂O₃ may have not effectively hindered the particle growth of Y₂O₃. (Y_0.90La_0.10)₂O₃ ceramic fabricated by both powders own smaller grain size and lower porosity than Y₂O₃ ceramics. The transmittance and sintering performance of Y₂O₃ ceramics were also improved after adding of La₂O₃. The powders prepared by both methods could be used to make high transparency ceramics.

Abstract: Based on the empirical electron theory of solids and molecules and the basic theory of the phase transformation of titanium alloys, a new method to calculate β transition temperature of titanium alloys is put forward after calculating the valence electron structure(VES) parameter n_A which is the covalence electron pairs on the strongest bond of alloy phases, the crystal cell weight of a and b phases in the structure, the compensation coefficient of the phase and the temperature coefficient of b stable element. After calculating we find β transition temperature of Ti-6Al-4V is 974.9 °C, the error of the theoretical calculation value and the experimental one(995 °C) is 2%, so it is feasible to calculate β transition temperature of the titanium alloys from covalence electron level.

Abstract: Ti/(Ru,Ir)O_x, and Ti/(Ru,Ir,La)O_x oxide electrodes were prepared by using thermal decomposition of the metal chlorides in the precursor solution on the Ti base. Their apparent electrocatalytic activity investigated by cyclic voltammetry, polarization curve, scanning electron microscope and X-ray diffraction. These data show that Ti/(Ru,Ir,La)Ox oxide electrode exhibits considerably high voltammetric charges, apparent current density and low onset potential for the ClER and OER. The XRD results reveal the main formation of the La-containing oxide electrode in amorphous phase.

Abstract: Hemocompatibility is a key property of biomaterials that come in contact with blood. Surface modification has shown great potential for improving the hemocompatibility of biomedical materials and devices. It has been improved that TiO₂ has excellent hemocompatibility. In this study, TiO₂ nanoparticles was added into polytetrafluorethylen (PTFE) resin in order to enhance hemocompatibility of the organic coating. The surface hydrophobicity of the coatings was characterized by contact angle measurement. Systematic evaluation of hemocompatibility, including platelet adhesion and blood clotting, proved that TiO₂ nanoparticles composite PTFE coating have better hemocompatibility. It is suggested that TiO₂ nano particles can improve hemocompatibility of organic coating due to its passive surface and chemical stability.

Abstract: In the present study, design of experiments (Orthogonal experiment) was used to find an optimal combination for the factors, which affect the catalytic activity of nano-crystalline TiO₂ powder synthesized by sol–gel method. Sixteen kinds of TiO₂ powder were prepared by changing three material ratio at four levels. The effects of calcinations temperature on the catalyst activity of TiO₂ were investigated by single factor experiments. TiO₂ were characterized by XRD. The results of design of experiments are examined by the direct observation analysis. The preparation conditions have been optimized as material ratio nTi(OC₄H₉)₄: nH₂O: nHN(C₂H₅OH)₂: nC₂H₅OH=1:2:2.5:20, mean 16.8 nm TiO₂ nanoparticle with anatase structure obtained at 500°C calcination. The photodegradation efficiency of methylene blue in aqueous solution is 99 % under 1g/L catalyst.