Compositions: ceramic – Ceramic compositions – Refractory
Patent
1985-09-16
1987-02-03
McCarthy, Helen M.
Compositions: ceramic
Ceramic compositions
Refractory
264 65, 501 98, C04B 3558
Patent
active
046409033
ABSTRACT:
Silicon nitride sintered bodies having particularly excellent strength and creep resistance at high temperature, in which a total amount of MgO and Al.sub.2 O.sub.3 is more than 7% by weight and not more than 30% by weight and a weight ratio of MgO/Al.sub.2 O.sub.3 is 5-15 and the remainder is mainly Si.sub.3 N.sub.4 and at least one of magnesium sialon crystal represented by the general formula Mg.sub.x/2 Si.sub.6-y+x/2 Al.sub.y-x O.sub.y N.sub.8-y (0<x.ltoreq.y<8, preferably 0.9.ltoreq.x/y) and forsterite crystal represented by the formula Mg.sub.2 SiO.sub.4 is contained as a second phase in addition to the main crystal of Si.sub.3 N.sub.4, are produced by mixing a raw material powder of silicon nitride containing not greater than 2% by weight of oxygen with MgO and Al.sub.2 O.sub.3 so that a total amount of MgO and Al.sub.2 O.sub.3 is from 7% by weight to 30% by weight and a weight ratio of MgO/Al.sub.2 O.sub.3 is 5-15, and firing the resulting mixture at a temperature of 1,650.degree.-1,850.degree. C. in nitrogen or an inert gas atmosphere.
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Matsuhiro Keiji
Matsui Minoru
McCarthy Helen M.
NGK Insulators Ltd.
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