Zhi Fa Wang

Improvement in the Thermal Shock Resistance of Zirconia Ceramic by the Addition of Aluminium Titanate

ZrO2-Al2TiO5 composite materials with high bending strength and good thermal shock resistance expansion were prepared using partially stabilized zirconia (Y-PSZ) powders coated with Al2TiO5 by co-precipitation method. The effects of Al2TiO5 content on the sintering properties, phase composition, microstructure and thermal shock resistance of the zirconia ceramic were investigated．The results show that the apparent porosity of the samples decreased and their bending strength increased with the content of aluminum titanate increasing from 0 to 8 wt%. The samples with 5 and 8 wt% aluminum titanate addtion have excellent thermal shock resistance. The results showed that the addtion of aluminum titanate could enhance the mechanical strength and improve the thermal shock resistance of zirconia ceramic. The XRD and SEM analysis results indicated that the propriety improvement is relative with the change of the microstructure and the increase of tetragonal ZrO2 phase in the composites.

Study on Sintering Properties and Crystallization of Fused Quartz Ceramic Materials Containing BN-B4C

Different dosages of BN-B4C compound additive have been introduced for preparing specimen with fused quartz granule (d50=10μm). Fused quartz ceramic materials were fabricated in reduction atmosphere at various temperatures for 1h. The characterizations were carried out by thermal expansion ratio, apparent porosity, cold modulus of rupture (CMOR) and SEM as well as by X-ray diffraction (XRD). The effect of BN-B4C on the sintering, crystallization and properties of fused quartz was investigated. The result reveals that with increase of the temperature, the apparent porosity and CMOR of specimens decrease. The specimen C sintered at 1300°C possessed a maximum CMOR (22.31 MPa). The specimen C sintered at 1350°C has more compact microstructure. The lowest thermal expansion ratio of the specimens sintered at various temperatures was obtained when the dosages of compound additive is 3%. With increasing BN-B4C content, the role on inhibiting crystallization was improved. The specimens containing 3 wt% BN-B4C had obvious effect on inhibiting crystallization of the specimens sintered at various temperatures.

Influence of Oxygen Donor Alcohols on Non-Hydrolytic Sol-Gel Synthesis of MgAl2O4 Spinel Nanoparticles

Magnesium aluminate (MgAl2O4) spinel nanoparticles were prepared by non-hydrolytic sol-gel method using anhydrous alcohols as oxygen donor. XRD and FTIR were used to characterise the effect of anhydrous alcohols on synthesis of MgAl2O4 spinel nanoparticles.The results showed that when the oxygen donor used in stoichiometric ratio for synthesizing MgAl2O4, anhydrous ethanol was the more effective oxygen donor than anhydrous isopropanol. But there was no remarkable effect on synthesis of MgAl2O4 spinel when the amount of anhydrous ethanol exceeded the stoichiometric ratio. The mean particle size MgAl2O4 spinel nanoparticles was in the range of 40 to 50 nm.

Effect of Rare Earth Nano-Oxides on Sintering and Crystallization of Fused Quartz Ceramic Materials

Fused quartz powder (size<0.04mm) was used as raw material, nano-Y2O3, nano-CeO2 and nano-La2O3 (size<0.08μm) were dividedly used as additives with dosage of 2% each. Fused quartz ceramic materials were sintered in reduction atmosphere at 1300°C, 1350°C and 1400°C for 1h. The effect of rare earth nano-oxides on sintering and crystallization of the fused quartz ceramic were researched by measurements of apparent porosity, bending strength and thermal expansion rate, and analyses of XRD and SEM. The results showed that additives nano-Y2O3, nano-CeO2and nano-La2O3 had obvious effect of inhibiting crystallization of fused quartz, and the samples added nano-Y2O3 and nano-La2O3 were better. Sample added nano-Y2O3 had least thermal expansion rate. Sample added nano-La2O3 had higher bending strength, and it showed that nano-La2O3 had better effect on sintering of fused quartz ceramic. It can be deduced that nano-La2O3 plays the excellent role as the crystallization inhibitor of fused quartz materials.

Research on PCS Real-Time System Based on Integrated Control and Simulation

The principle and control method of PCS circuit based on DSP2812 are introduced.The unified model of equations and simulation is built based on the topology of the circuit.The real-time simulation and directly generation of the control code is implemented using Embedded Coder of MATLAB toolbox.The integrated control and simulation design of control algorithm and dynamic process of PCS are implemented.

Sintering Properties of Fused Silica/Nano-Zirconia Composite Ceramic

Zirconyl chloride was used as zirconium source and fused silica particles were used as main raw material. First of all, the composite powders were prepared by wet chemical synthesis using ammonia as the precipitator and polyethylene glycol as the dispersant. Then, fused silica nanozirconia composite ceramic containing nanometer particle zirconia with different contents (5%, 15%, 25% and 35%) were fabricated in reduction atmosphere at 1300°C, 1350°C and 1400°C for 1 h. The bulk density and bending strength were measured, microstructure was observed by SEM. The result indicated bulk density and bending strength of composite ceramic increase and microstructure becomes denser with content of zirconia increasing. Bulk density of composite ceramic increases and bending strength which reaches maximum at 1350°C firstly increases then decreases with the increase of sintering temperature. Both high sintering temperature and nanozirconia possessing high energy interface can improve the composite ceramic sintering.

Research on Mullite-Corundum-Aluminium Titanate Composite

Mullite-aluminium titanate-corundum composite was prepared at 1300°C with refractory clay, aluminium titanate and high alumina grog as raw material, molded at pressure of 50MPa. Effect of raw material ratio on sintering and themal shock resistance of the mullite-aluminium titanate-corundum composite was researched by measurements of apparent porosity, bending strength and residual strength after water-cool, and analyses of XRD and SEM. The results showed that as refractory clay content, apparent porosity of samples decrease, bulk density and bending strength increase. When the weight ratio of refractory clay, aluminium titanate and high alumina grog is 60/10/30, themal shock resistance of sample is excellent, The XRD and SEM analysis results indicated that the mechanical and thermal proprieties are relative to the microstructure and crystal phases of the composite materials.

A Study on Crystallization of Fused Silica/Zirconia Ceramic Composites

Fused silica particles and zirconyl chloride were used as main raw material. Meanwhile, ammonia was used as precipitator and polyethylene glycol as dispersant. Firstly, the composite powders were prepared by wet chemical synthesis. Then, fused silica/zirconia ceramic composites containing zirconia with different contents (5%, 15%, 25%, 35% and 45%) were fabricated in reduction atmosphere at 1300°C, 1350°C and 1400°C for 1 h. The thermal expansion ratios and XRD of samples were examined. The analysis of XRD indicated that the cristobalite peaks intensity of sample with more zirconia is lower at the same sintering temperature, and the intensity of cristobalite was higher while sintered at higher temperature. Zircons were found in all samples’ XRD patterns. The results of thermal expansion ratios showed the ratios of samples with more zirconia were lower, especially at higher sintering temperature. So, existence of zirconia can inhibit crystallization of fused silica/zirconia ceramic composites effectively.

Influence of Nano-Yb2O3, Nano-Nd2O3 and Nano-Dy2O3 on Sintering and Crystallization of Fused Quartz Ceramic Materials

Fused quartz powder (d50=19μm) was used as raw material, nano-Yb2O3, nano-Nd2O3 and nano-Dy2O3 were dividedly used as additive with dosages of 3% each. Fused quartz ceramic materials were sintered in reduction atmosphere at 1300°C, 1350°C and 1400°C for 1h. The influence of rare earth nanooxides on sintering and crystallization of the fused quartz ceramic were researched by measurements of apparent porosity, bending strength and thermal expansion ratios, and analyses of XRD and SEM. The results showed that samples added nano-Yb2O3 and nano-Nd2O3 have lower apparent porosity, higher bending strength and lower thermal expansion rate. It can be deduced that additives nano-Yb2O3 and nano-Nd2O3 have obvious effect on facilitating sintering and inhibiting crystallization of fused quartz materials at experimental temperatures.

Influence of Grain Composition and Sintering Temperature on Performance of Silicon Carbide Refractory Material

Silicon carbide with diffierent granularity and three grain composition was used as raw material. Silicon carbide refractory material was prepared in oxidizing atmosphere at 1400 °C, 1450 °C and 1500 °C for 3 h. Performence of samples were researched by measurements of apparent porosity, bulk density, bending strength at room temperature, thermal shock resistance and thermal expansion rate, and analyzed by SEM. The results showed that samples sintered at 1400 °C have low thermal expansion rate and apparent porosity, high bending strength and bulk density, good thermal shock resistance, compact texture as well. It can be deduced that (1.0-0.5mm) / (0.5-0.1mm) / (45μm) / (5μm) = 50 / 17/ 20/ 13 is the best grain composition to improve integrated performance of silicon carbide refractory material.