Advanced Materials Research Vols. 532-533

Abstract: The boehmite (AlOOH) sol derived from aluminium isopropoxide was synthesized by Yoldas method. The physicochemical process and phase transition of AlOOH were investigated by TG-DSC, N2 adsorption-desorption, XRD and TEM. The results showed that upon heating, AlOOH lost the physicsorbed water first, and then lost the chemisorbed water at 242 °C, and the dehydroxylation occurred at 361 °C. The BET surface area, total pore volume and pore diameter increased, since the waters were lost. The orthorhombic AlOOH transformed to the cubic γ-Al2O3 at 361 °C, the cubic η-Al₂O₃ appeared after 484 °C, the monoclinic θ-Al₂O₃ and rhombohedral α-Al2O3 appeared after 1026 °C, and it totally turned into α-Al₂O₃ at 1237 °C.

Abstract: Two-photon three-dimensional optical data storage is an important method to realize high density storage and ultra-high density storage. This paper introduces the the basic principle of two-photon photobleaching optical storage, describes two-photon three-dimensional optical storage system and the absorption and fluorescence spectra of a new type of photobleaching materials BASF in detail, carries out the experimental study that two-photon information is written and read out against a new photobleaching material of BASF using femtosecond pulse laser wavelength is 800nm, and realize two layers of optical information storage, the information point spacing is 8μm and the interlayer distance is 15μm; two-layer information point signal strength is recognized using Recognition algorithm. The experiment proved that new photobleaching material of BASF can be used for two-photon three-dimensional optical storage, that has laid a solid foundation for the high-density and ultra-high density optical information storage materials research.

Abstract: Thermal oxidation treatment is a convenient and environmental friendly technique that can be used to harden the surface of titanium alloys, and hence improve the poor properties of the materials. The aim of the paper is to study the oxidizing kinetics of the process at different temperatures. With this purpose, pure titanium TA2 was subjected to thermal oxidation (TO) treatment in a conventional muffle furnace at 500°C~1050°C for 20mins~930mins under air atmosphere and cooled in the air. The surface morphology of the oxide layer at various temperatures was observed by scanning electron microscopy (SEM). The weight gain after oxidation treatment under different testing condition was measured and calculated. It is concluded that the oxidizing kinetics at 600°C～750°C followed parabolic law, and the parabola rate constant of Kp was investigated. The oxide layer formed at temperatures lower than 800°C is dense and protectable, while it is getting very loose at temperatures higher than 800°C.

Abstract: A new high-strength magnesium alloy with better properties than that of AZ31 was developed. The effect of applied pressure during squeeze casting on microstructures and properties of the alloy was studied by means of techniques such as standard mechanical tester, Brinell Hardness Tester (BHT), and Metallographic Microscope (MM). The parameters studied include squeeze casting pressure, melt temperature and pressure holding time by using orthogonal experimental method. It was found that a squeeze casting pressure of 110 MPa and a melt and pressure holding time of 700 °C and 15s respectively gave a good combination of mechanical properties in AZ31 Mg alloy. This was primarily due to effective die filling, microstructural refinement and good heat transfer between the molten metal and the mould.

Abstract: γ-Fe₂O₃/N-doped TiO₂ nanotubes (N-TiO₂ NTs) photocatalyst was successfully prepared by a wet chemical method. Visible light responses of this novel catalyst for decomposing methyl orange (MO) in air were also evaluated. It was found that the photocatalytic activity of γ-Fe₂O₃/N-TiO₂ NTs was higher than those of N-doped TiO₂ NTs, TiO₂ NTs and P25. The characterizations including TEM, EDX and UV/Vis DRS revealed that iron oxide nanoparticles were decorated in/around N-TiO₂ NTs and the spectral response was enhanced in visible region. Meanwhile, the catalyst recycled by external magnetic field showed that its photocatalytic efficiency did not decrease obviously.

Abstract: Diamond-copper composites are fabricated by spark plasma sintering (SPS). The effects of particle size, original properties and coatings of diamond on the thermal conductivity (TC) of diamond-copper composites have been investigated, respectively. The results indicate that thermal conductivity of composites enhances with an increase in particle size and original properties of diamond. Composites with Cr, Ti or Ni coatings on diamond surface appear remarkably higher TC than that which without any coatings. The improvements of TC of diamond/copper composites are mainly due to the large particle size diamond decreasing the interfacial area in composites, the high original properties diamond possessing higher original TC, and coatings on diamond surface declining the interfacial thermal resistance and improving the wetting properties between diamond and copper.

Abstract: Polyamide 6-polyurethane (PA6-PU) block copolymers filled with graphite particles were prepared by anionic polymerization process. The friction and wear experiments were conducted using a UMT-3 machine with the chromium steel ball sliding on surface of the composites at high sliding speeds of 500rpm, 1000rpm and 1500rpm and loads of 78.5N and 157N. With adding of graphite, coefficient of friction and wear rate values of the composites decreased firstly, and then increased. And the influence of the applied load and sliding speed on tribological properties of the composites was explored in this study. The results showed coefficient of friction and wear rate values increased with the increasing of load. Coefficient of friction decreased and wear rate values increased with increasing of sliding speed. Microstructure of wear surface of the tested composites was inspected by scanning electronic microscope(SEM) and wear mechanism of the composites was studied.

Abstract: To develop novel cathode materials with high electrical performances for intermediate temperature solid oxide fuel cells (IT-SOFCs) and optimize the preparation process, perovskite-type oxides Pr_1-x-ySr_xCa_yCo_1-zFe_zO_3-δ (x=0.1, 0.2; y=0.1, 0.2; z=0.2, 0.3, 0.4; denoted as PSCCF-81182, PSCCF-72173 and PSCCF-62264) were prepared by solid state reaction. The formation process, phase structure and microstructure of the prepared samples were measured using TG-DTA, FT/IR, XRD and SEM techniques. The mixed conductivity of the samples was measured using DC four-terminal method in the range of 150-950 °C. Chemical state of the elements was measured by XPS experiments. The results show that the prepared samples PSCCF-81182, PSCCF-72173 and PSCCF-62264 exhibit a single phase with cubic perovskite structure after sintered at 1200 °C for 6 h. The mixed conductivity of the samples increases with temperature up to a maximum value, and then decreases. At lower temperature, the conductivity follows small polaron hopping mechanism. The negative temperature dependence occurring at higher temperature is due to the creation of oxygen vacancies for charge balance. At intermediate temperature (600-800 °C), the mixed conductivity values of the prepared samples are all much higher than 100 S•cm^-1，and can meet the demand of cathode materials for IT-SOFC. XPS tests show that Co and Fe elements in PSCCF-72173 are all of + 3 and + 4 valence. Absorbed oxygen can also be found from the XPS patterns, which is related to the concentration of oxygen vacancies in the perovskite-type oxides.

Abstract: Polyamide 6/polyurethane/graphite composites have been prepared by anionic polymerization process. The effect of graphite concentration on mechanical properties of the composites was investigated. The test results show that with increment of graphite content, tensile strength of the composites increases firstly, and then decreases, while notch impact strength decreases. The change of mechanical properties of the composites is attributed to the dispersion of graphite, the interfacial properties between the matrix and graphite and the nucleation effect of graphite. In addition, the relationships between loss factor(Tan δ), storage module(E’) and temperature were investigated using Dynamic Mechanical Analysis(DMTA), and the morphological characteristic of the composites were studied using Scanning Electronic Microscope (SEM).