Silicon nitride powder by imide decomposition process; Chikka keiso (imide netsu bunkaiho)

Higher performance has been demanded on silicon nitride products in recent years, thereby requirements in improving the performance and increasing the production quantity of their material powder have been expanded. This paper illustrates a new imide decomposition process developed by Ube Industries, introducing a method of manufacturing high-purity material powder (halogen <100 ppm, for example) using the imide decomposition process, and the product characteristics. Organic solvent aqueous solution of SiCl4 is reacted with NH3 to obtain amorphous Si3N4 via Si(NH)2. Adjusting the conditions in subsequent crystallization processes makes possible not only control of crystallinity, {alpha}/{beta} ratio, and particle systems, but also acquisition of {beta} silicon nitride whiskers, and Y{alpha}-SiALON powder by adding Y and Al. Mixing the powder with silicon nitride powder and sintering the mixture under normal pressure can produce a high-performance sinter. Mixture of two kinds of powders may produce composite texture with such a complex structure as whisker reinforced material. 9 refs., 4 figs.