Densification of Si_3N_4/Si_3N_4-Fibre Composites

摘要

Mixtures of commercial #alpha#-Si_3N_4powders, and oxide additives, with #beta#-Si_3N_4monocrystalline fibers or #beta#-Si_3N_4 prismatic grains havebeen prepared. The influence of the oxide additives on thetransformation #alpha#->#beta#, densification rate andmicrostructure have been analyzed. The addition of #beta#-Si_3N_4, in the form of fibers as well as grains, promotedtransformation but retarded densification. This decrease insintering rate has been overcome by increasing the amount ofadditives. The addition of #beta#-Si_3N_4 produced acoarsening of the microstructure of these materials, being itmore pronounced in the case of the fiber composite.