Papers by Author: Jian Qing Wu

Abstract: The anchor plays a very important role in gravity retaining wall. The displacement of retaining and soil pressure distribution with anchor is different from that without anchor. The numerical simulation software FLAC^3D is used to analysis the soil pressure distribution characteristics of gravity retaining wall. The results show that the anchor plays a supporting role in gravity retaining wall. There is a critical length in the anchor in gravity retaining wall. The soil pressure distribution of gravity retaining wall with anchor does not conform to the classical Coulomb linear distribution theory and more research is needed for the soil pressure distribution theory. The research has important guiding significance on the design and construction development of gravity retaining wall.

Abstract: Carbonated hydroxyapatite (CHA) and hydroxyapatite (HA) were prepared by the wet chemical method. The contact angle was measured to calculate the surface energy. The biomineralization process in SBF solution of HA and CHA were investigated in vitro. The cell attachment and proliferation behavior of CHA and HA were compared by the cell culture experiments. The results show that the polar component of surface energy of B-type CHA is higher than that of HA. Osteoblastic cells attach and proliferate very well on the surface, which indicates the excellent cell compatibility. The CHA have high bioactivity owing to rapid formation of hydroxyl-carbonate-apatite (HCA) mineralized layer on the biomaterial’s surface in SBF.

Abstract: The effect of Ho2O3 doping on the electrical properties and microstructure of ZnO base varistor was investigated. It was found that Ho2O3 is an effective dopant for increasing the breakdown electric filed. The Ho2O3 doping can also improve the nonlinear performance both in low and high current area. But excessive doping of Ho2O3 will decrease the withstanding surge current. With 0.8mol% Ho2O3 doping, the varistor samples exhibit a breakdown voltage of about 400V/mm, a nonlinear coefficient of 80 and the withstanding surge current of 8/20μs, waveshape is higher than 5kA. Ho2O3 dopant can hinder ZnO grain growth and make the crystal grains more uniform.

Abstract: Precursor of nanosized TiO2 was prepared by alkoxide hydrolysis method. It was dried by common drying, far infrared drying, vacuum drying and supercritical drying before heat-treated at 600°C and 800°C. Influence of drying process and treatment temperature on the crystalline phase composition and photocatalytic activity were analyzed. The photocatalytic activity of the TiO2 dried by common and far infrared drying is higher than that of the TiO2 dried by vacuum and supercritical drying after treated at 600°C. The photocatalytic activity of the TiO2 dried by common and far infrared drying is lower than that of the TiO2 treated by the other two drying methods after treated at 800°C.

Abstract: The anti-reducing sintering of (Ca,Sr,Ba)TiO3-based dielectrics was achieved by the cooperating effect of Mn2+, Ca2+, Mg2+, Dy3+ and Yb3+. A small quantity of Zr4+ partly substitution for Ti4+ can improve the temperature dependence of dielectric constant. But ZrO2 will also reduce the solid solubility of BaTiO3-SrTiO3-CaTiO3 ternary system, and may cause phase separation. The separated ferroelectric phase increases the capacitance change under DC bias. Non-reducible (Ca,Sr,Ba)(Ti,Zr)O3-based dielectrics with single orthorhombic phase of perovskite structure was obtained. The dielectric and DC bias properties are: .C/C (DC bias: 1.5kV/mm) <0.05%, ε =250~300, tgδ < 0.5%.

Abstract: A new method called cation extraction process has been applied to improve the oxidation resistance of silicon nitride ceramics with sintering additives. It is found that the high temperature oxidation rate of the Si3N4 ceramic treated by the process decreased remarkably in contrast to the oxidation rate of the Si3N4 without the process. The oxidation rate of Si3N4 ceramics with the cation extraction process is reduced more than 50% comparing with that of the Si3N4 ceramics without the process. The morphological characteristic and phase composition of the oxides were analyzed by means of SEM and XRD. The oxidation rate of silicon nitride after cation extraction treatment is determined by the quality of the “purified layer” formed below the pre-oxide scale. Thicker oxide layer formed in pre-oxidation, higher extraction temperature and longer extraction time are helpful to form a good “purified layer”.

Abstract: In this article, the β–Sialon with average diameter size less than 20µm is prepared and researched by use of aluminum, silicon, and corundum at 1300°C holding temperature for 8h under nitrogen atmosphere. The preparation temperature of β–Sialon powder was optimized according to the results from the experiments that different aluminum and silicon reacted with pure nitrogen at different temperature. The reaction at the preparation of β–Sialon powder was discussed by thermodynamic calculation. The reaction mechanism was investigated by x–ray diffraction (XRD) and scanning electron microscope (SEM) was discussed in detail.

Abstract: The influence of leucite on dental porcelain properties is investigated in this paper. The nanosized leucite powder prepared by sol-gel method was added into a low-fusing temperature frit to fabricate dental porcelain fused to metal. The porcelains with different leucite contents were sintered at the temperatures ranging from 780° to 900°C. The flexural strength and the thermal expansion coefficient (TEC) of the dental porcelain containing leucite particles are evaluated. The micro- structure and phases of the porcelain are characterized and the mechanism that nanosized leucite particles strengthening the porcelain is discussed.

Abstract: A commercial a-alumina powder was mixed with Zr(OH)4 gel synthesized by a precipitation method. The mixture was calcined at 600°C for 2h. The Al2O3−15 wt% ZrO2 composites were sintered for 2 h in the temperature range between 1400°C and 1650°C in air. At the sintering temperature of 1550°C the highest density, the best wear resistance, the maximum bending strength of 708 MPa and the highest fracture toughness of 5.8 MPa×m1/2 were achieved, respectively. Improvement of the mechanical and wear properties of the Al2O3 matrix should mainly be attributed to the addition of ZrO2.

Abstract: In this paper, the α-Al2O3 microfiltration membrane modified by nano-ZnO coating was obtained using zinc nitrate and urea as raw materials via homogeneous precipitation method. The effects of reaction temperature and coating times on the modification of the membrane were emphatically studied. The test results show that the flux of modified membrane is raised by 43% when the nano-ZnO particles (5 ~ 10 nm) are smoothly and densely coated on the surface of the membrane. The mechanism of the modification was studied by means of TEM, FTIR, XPS, Zeta electric potential analyzer, etc.