Abstract
In order to use ceramics as a material for slurry valves, which are exposed to a flow of slurry containing hard particles of coal or ash, the bending strength of alumina (Al2O3), silicon nitride (Si3N4), silicon carbide (SiC) and partially stabilized zirconia (PSZ) was examined under the practical condition (400°C, slurry dipped condition). Also high resolution transmission electron microscopy (HR-TEM) was employed to characterize these materials. From the direct observation of the microstructure of cracked surfaces, it was shown that fracture took place from the structual weak points, that is, pores, large crystal grains and the impurity phases. In the case of ceramics with uniformly small crystalline particles and very little pores, fracture seems to occur through the impurity phases.
