Jian Qing Wu

The Influence of Nanosized Leucite on Dental Porcelain Properties

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.

Preparation of β-SiAlON Powder at Low Temperature

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.

Passivity-based control in wind turbine for maximal energy capture

The question of maximal energy capture in the nonlinear wind energy conversion system with stochastic wind variety is presented. This article adopted the two inputs, that is pitch angle and trigger angle. The control strategy was based on passivity theory and designed a control system with strong robust and favorable dynamic characteristic. This control system combined the maximal wind energy capture to system stability, adopting the methods of selecting appropriate steady state and damp rejecting. The simulation results showed the control strategy can capture the maximal wind energy for that wind energy conversion system which has the stochastic wind and parameter variety.

A reinforcement learning approach to STATCOM controller

The advanced static synchronous compensator (STATCOM) is a device that can provide reactive support to bus voltage. A novel control scheme based on reinforcement learning algorithm for the STATCOM is presented in this paper. Design of STATCOM controller presented does not depend on structure and parameters of power system. The adaptive heuristic critic algorithm is adopted in this paper and the parameter of the controller are updating by given reinforcement signal of system. Only local information is required. A simulation example of single-machine infinite power system is given, and the result shows the effectiveness on maintaining voltage and preventing voltage collapse.

Effect of Ho2O3 Doping on Performance of ZnO Varistor

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.

Effect of Ca/P Molar Ratio and Heat Treatment on Thermal Decomposition and Reconstitution of Hydroxyapatite

Stability of hydroxyapatite(HA) structure is influenced by preparation conditions and afterwards heat treatment. In this paper, the powders with different Ca/P molar ratio were calcined to investigate the influence of Ca/P and heat treatment on thermal decomposition and reconstitution of HA. The results show that the Ca/P has little change even calcined at a high temperature of 1500°C. The Ca/P molar ratio close to 1.67 is beneficial to form high purity HA. HA gradually releases its OH- ions in the temperature range of 800-1200°C. The decomposition takes place at about 1200°C and will become more and more severe with the increase of temperature. Cooling with slow rate and post-heat treatment in wet atmosphere are beneficial to both the rehydration and the recovery of HA from the decomposition products (TTCP and α-TCP).

(Ca,Sr,Ba)TiO3-Based Dielectrics Sintered in Reducing Atmosphere

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%.

Effect of Drying Methods on Photocatalytic Activity of Nanosized Titanium Dioxide

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.

Modification of Al2O3 Microfiltration Membrane by Nano-ZnO Coating

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.

Antistatic Ceramic Tiles Modified by Sb-Doped SnO2

Antistatic ceramic tiles was prepared by adding 15wt% or more synthesized Sb-doped SnO2 into their glazes. The tiles have the surface resistivity ρs of 1.40 × 106 to 5 × 108 Ω×cm. The conduction mechanism was analyzed and it was shown that the electrostatic charges are eliminated by the network formed by the Sb-doped SnO2 distributed in the glaze.