| 摘要 |
<p>1427968 Silicon nitride bodies NORTON CO 15 June 1973 [16 June 1972] 28538/73 Heading C1A [Also in Division C7] The invention comprises a shaped isotropic body of Si 3 N 4 having a density greater than 2À4 g./o.c., e.g. up to 2À45 g./c.c., a transverse rupture strength greater than 40,000 p.s.i., e.g. up to 50,000 p.s.i., a pore size of less than 2Á and anα/# Si 3 N 4 ratio of greater than 2, e.g. up to 7À15. The shaped body is prepared by compressing Si powder of particle size less than or equal to 10 Á into a green body having a density of at least 1À4 g./c.c., e.g. up to 1À56 g./c.c., sintering, e.g. at 1100‹ C. in Ar and then nitriding the sintered body, e.g. at 1350- 1450‹ C. in N 2 /NH 3 . The Si powder may have an average diameter of 2 Á and contain Fe, Al or Ca in an amount totalling 1%. The transverse ruptive strength of the sintered body may be greater than 1000 p.s.i.</p> |
