Abstract
Alumina hydrate-coated SiC whisker, a starting powder for fabrication of SiC whisker reinforced alumina ceramics, was prepared from SiC whisker and aluminum sulfate by homogeneous precipitation method using urea. Effects of reaction conditions on the coalescence of coated bodies and formation of independent alumina hydrate particles were studied. Observation of coated bodies during reaction showed that coalescence of coated bodies occurs by collision and agglomeration followed by deposition of alumina hydrate on the collided specimens. Coalescence of coated bodies was suppressed by intensive stirring, use of a flow reactor, high [SiC]/[Al2(SO4)3] ratio, low hydrolysis rate of urea, and high urea concentration. Generation of independent alumina hydrate particles was suppressed at a high SiC whisker concentration, a low aluminum sulfate concentration, and a low hydrolysis rate of urea. When the deposition rate of alumina hydrate was very low, coating was not uniform.
