Study On Preparation And Properties Of Electroheating Porous Silicon Carbide Ceramics

Porous silicon carbide ceramics have been widely used in many industry because of its high temperature resistance, resistance to eroding and high porosity and so on .However, it has two problems in practice. One is its lost function due to block narrow passage,the other is that the porous materials can been used until it was heated to a certainty. This paper develops that porous silicon carbide ceramics have function of heating element by semi-conductor characteristic of silicon.Electroheating porous ceramics is processed by three methods of grain pile and organic-gridding pile and great porous size ceramics. At the same time,I study all kinds of technics Especially discussing the relation between material(particle size, content) and sample performance. In order to research inductivity of sample AL2O3,ZrO2 and B2O3 which are used, the effect of inductivity performance was discussed. Silicon carbide ceramics capability and microcosmic construction are studied by means of XRD and SEM, with the conductivity mechanism of sample.The result shows that the performance of PSC has relation to backbone and granularity .The experiment shows that the porosity will reach to the most (39.6%) and the compressive strength will reach to the most (19.6Mp) when porous size of silicon is 106μm, With the lower electrical resistance.The silicon ceramics capacity has relation to the firing temperature, firing time, materials porosity and content. When the sintering temperature is 2250℃ and the sintering time is 21 minutes, the electrical resistance is the least (0.064Ω·cm).The experiment shows that the porosity and water absorptivity decreases gradually with increasing of silicon carbide grains ,and electrical resistance went on increasing . when the silicon carbide is up to 50％,the electrical resistance becomes the least (0.172Ω·cm). The porosity and water absorptivity slowly increases when the producting celluar was increased, with the lower stress and higher resistance.In experiment ,the impurity of Al2O3,ZrO2 and B2O3 are imported. The research shows that ZrO2 has nothing to do with the melt pre-pressingly of sample and the electrical resistance decreases due to Al2O3,ZrO2 and B2O3. The Al2O3 and ZrO2 lead to the more decrease of the electrical resistance than Al2O3 does. When they are mixed, the electrical resistance of sample is unstable and the mechanism decreases too The performances of porous silicon carbide ceramics have obvious difference because of porous structure by three methods. The test shows that the porous structure of different aspect lead to the different penetrating parameter. The porous silicon carbide ceramics have excellent resistance to thermal shock because of porous characteristic and resistance to thermal shock of silicon carbide.In addition, the porous silicon carbide ceramics have excellent conductivity. The efficiency that electricity energy is transformed to heat energy is as high as 99.9%.The inductivity mechanism is found to be depended on the crystal property, impurity property, limitation type and number and so on.