Jing Hong Du

Research on Dehydrogenation and Sintering Process of Titanium Hydride for Manufacture Titanium and Titanium Alloy

In this paper, unlike the traditional powder metallurgy technology, the titanium hydride is directly used as the starting material to manufacture the titanium and titanium alloy. Thermogravimetric and dilatometric techniques are performed to study the dehydrogenation and shrinkage of TiH2 powders with different particle sizes. The process factors such as the sintering temperature, the sintering time, the heating rate, the compaction density, the compaction methods, and the alloy system, would affect the sintering densification of TiH2 powders and TiH2-Al-V alloy powder. The results shown that the dehydrogenation temperature of the starting and ending of the ball milling TiH2 is lower than that of the coarse TiH2 powders, the finer the TiH2 powder, the lower the temperature. The densification of TiH2 powders is easy due to the combination of dehydrogenation and shrinkage of α-Ti in one process, which creates the fresh dehydrided titanium uniform during sintering, thus leads to rapid densification and very high sintering relative density, higher than 99%. In contrast, it is difficult to achieve a full densification of TiH2-Al-V alloy powder during sintering, which requires dissolution of alloy elements during sintering above its beta transformation temperature. The sintered microstructure of Ti-6Al-4V shows the typical lamellar shaped α+β characteristics, with a uniform alloy element distribution.

Low Temperature Co-Fired ZnNb2O6 Dielectric Ceramic Doped by B2O3

To lower the sintering temperature of ZnNb2O6 microwave dielectric ceramic, ZnNb2O6 doped with B2O3 were prepared by the traditional solid state reaction method. The effects of the amount of B2O3 (0.25-5.0wt.%) on the microstructure, density and electrical performances were investigated. The results show that a pure columbite ZnNb2O6 phase was obtained for all B2O3-doped ceramics. The microwave dielectric properties reached the maximum values of εr = 24.1, Q×f = 19502 GHz, τf = -52.19 ppm/°C for 1wt% B2O3-doped ZnNb2O6 ceramic sintered at 1050 °C for 4 h. All of evidences suggest that the enhancement of microwave dielectric properties is due to the enhanced ions-energy and ionic diffusion with the increase of sintering temperature. Furthermore, B2O3 doping can generate liquid phase and reduce the activation energy of diffusion to promote the materials sintering.

Photocatalytic Properties of (Fe, N)-Codoped TiO2

Fe, N)-codoped TiO2 were prepared by calcining the Fe-doped TiO2 samples accomplished by precipitation method in the nitrogen atmosphere, and the photocatalytic properties of (Fe, N)-codoped TiO2 at different temperatures were investigated. The samples were characterized by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and ultraviolet-visible (UV-vis). The results show that the (Fe, N)-codoped TiO2 powder samples calcined at 600°C are dispersed well with more hydroxyl groups on its surface. The absorption edge of the (Fe, N)-codoped TiO2 is 429nm due to the effects of mixed crystal, which means the improvement of photocatalytic capability.

Effects of Sintering Temperature on Microstructure and Properties in TiO2 Varistor Ceramics

The effects of sintering temperature on microstructure, micro-composition, barrier structure and electrical properties of TiO2 varistors ceramics were investigated. The microstructures and chemical compositions of grains in TiO2 ceramics were measured by SEM and EDS. Based on the thermo electronic emission theory, Grain boundaries barrier structure was calculated by analyzing electrical properties of samples. The sample sintered at 1350°C exhibits better microstructure and properties. The grains size of the TiO2 sample sintered at 1350°C is about 15m, and other electrical properties are as follows: solid solubility of donor doping Nb5+ cation solute in TiO2 grains of 1.49mol%, barriers height of 0.28ev, barriers width of 48nm, varistor voltages of 5.25V/mm, non-linear coefficient of 4.2 and relative dielectric constant of 1.1×104.

Effects of Paste Composition and Sintering Process on Performance of Silver Paste for Silicon Solar Cells

In order to study the effects of composition ratio of silver paste and the sintering process on the properties of the silver film after sintering, the effects of different ratios of silver powders, glass powders and organic carrier in silver paste and different sintering temperatures and sintering time on the adhesion force and square resistance of the silver film were studied. The morphology of the sintered silver film was observed by SEM. The results showed that the silver film sintered at 760°C for 6 seconds had better properties after sintering when the ratio of silver powders, glass powders and organic carrier in silver paste was 80:5:15 and the silver powders was composed of spherical silver powders and flake silver powders at the ratio of 94:6. The adhesion force and square resistance of the silver film were 8.25 N and 3.47mΩ /□, respectively.

Performance of (Y2O3,V2O5) Co-Doping TiO2 Ceramics

The present study investigated the effect of the sintering temperature and (Y2O3, V2O5) co-doping on the performance of TiO2 varistor ceramic which has lower varistor voltage and high nonlinear coefficient. The results showed that the TiO2-based varistor ceramic which doped with 0.35% mol and 0.25% mol of Y2O3 and V2O5 has good comprehensive electrical performance and excellent dielectric constant sintered at 1200°C. Its varistor voltage V1mA is 38.1V, nonlinear coefficient is 4.6.

La-Doped Nanometer TiO2 Powders Prepared by Sol-Gel Method

La-doped Titania powders were synthesized by sol-gel method. The influence of dopant on the phase transformation temperature, Phase compositions, chemical states, microstructures and the visible light absorbable range of titania were investigated, which were characterized by X-ray diffractometer (XRD), transmission electron microscopy (TEM), energy dispersion X-ray spectrum in scanning transmission electronic microscope (STEM-EDS) and UV-Vis spectrophotometer (UV-Vis). The results show that the dopant of La3+ significantly inhibited the phase transition and grain growth of TiO2.With the increasing of calcination temperature, the grain orientation of TiO2 are from clutter into order and the light absorption band edge of TiO2 are blue shift. La3+-doped titania precipitate La4Ti19O24 and the second phase precipitated on the surface of TiO2 with irregular spherical.

Preparation Technology of ITO Composite Oxides Nanopowder

The technological parameters on synthesis rate of ITO nanometer by chemical coprecipitation were investigated. The effects of process parameters on synthesis rate of ITO nanometer powders were discussed by the range analysis of orthogonal experiment design. The dispersion features of ITO nanometer powder by ultrasonic dispersion or without were compared. The results show that the biggest factor that affects the powder synthesis rate is the pH at the titration end-point. Powder synthesis rate increases with the increase of pH value. When pH is 9, the powder synthesis rates are all above 90%. TEM images show that ITO nanometer powders are well dispersed without obviously agglomeration when anhydrous ethanol is used as dispersant. Particles have diversity of shapes, and the particle sizes distribute widely. After Ultrasonic physical dispersion, ITO nanopowders are well dispersed with no obviously agglomeration, narrow particle sizes of 20-30 nm and the approximation spherical particle morphology.

Effects of Solid Content on Properties and Structure of PMN-PZT Green Body by Gelcasting

The piezoelectric ceramic of PMN-PZT was prepared by gelcasting using N-hydroxymothl acrylamide(NMAM) as monomer. The green bodies with different microstructure and properties were obtained by changing solid contents of slurry. The effects of solid volume fraction in slurries on properties of PMN-PZT green bodies were investigated. The results that green shrinkage reduced from 5.95% to 1.47%, the green density increased from 3.51g/cm3 to 4.69g/cm3, and green bending strength increased firstly then decreased when solid content of slurry changed from 45vol% to 60vol%. SEM photographs revealed thatSuperscript text the green body had a uniform microstructure and few agglomerates when the solid loading was 50vol%.

Research on Polymerization of PMN-PZT Piezoelectric Ceramic by Gelcasting Using NMAM System

The industrialization of gelcasting technique has been prevented because acryamide is a neurotoxin monomer. In this paper, a low-toxicity gel system based on the polymerization of low-toxicity N-hydroxymothl acrylamide was used for the gelcasting PMN-PZT piezoelectric ceramic. The effects of monomer concentration, the dosage of initiator and catalyst, pH value on polymerization were studied. The results showed that the condition suitable for gelcasting PMN-PZT piezoelectric ceramics could be obtained while monomer concentration was 10wt%～15wt%, the dosages of initiator and catalyst were respectively 0.4 vol%～0.5vol% and 0.4vol%, pH value of slurry was about 10. The highest bending strength of PMN-PZT green body prepared at the aboved conditions can reach 19.5Mpa