Synthesis of High Purity, Alpha Phase Silicon Nitride Powder.
DEPARTMENT OF THE AIR FORCE WASHINGTON D C
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A method is provided for preparing alpha silicon nitride powder in which very high purity, liquid silicon tetrachloride is reacted with an excess of ammonia gas in dry deoxygenated benzene or normal hexane at about 0C, yielding a precipitate of silicon diimide and ammonium chloride. After removal of the benzene or n-hexane from the precipitate, the mixture of silicon diimide and ammonium chloride powder is heated under a vacuum from room temperature to a temperature in the range of 1200 to 1350C and maintained at the latter temperature for a period of about 2 to 8 hours. The product obtained is a high purity, submicron, alpha phase silicon nitride powder which is eminently suitable for the fabrication of dense bodies for use in high performance gas turbine engines and in radome applications.
- Ceramics, Refractories and Glass