Ceramic matrices reinforced with SiC, Si.sub.3 N.sub.4 or SiAlON fibers having a coating of C, B or BN containing SiC or Si.sub.3 N.sub.4

Fiber-reinforced ceramics comprising at least one of fibers and whiskers distributed in a sintered ceramic matrix, the ceramic matrix being composed mainly of SiC, Si.sub.3 N.sub.4, or Si.sub.6-z Al.sub.z O.sub.z N.sub.8-z where 0<z.ltoreq.4, the fibers and the whiskers consisting essentially of at least one of SiC, Si.sub.3 N.sub.4, or Si.sub.6-z Al.sub.z O.sub.z N.sub.8-z where 0<z.ltoreq.4, a coating film comprising C, B or BN containing 10-50 mol % of SiC or Si.sub.3 N.sub.4 being provided on surfaces of the fibers and the whiskers, and a ratio of distances l between the fibers or the whiskers to diameter d of the fibers or the whiskers having the coating film, l/d, being 0.5 to 2;

• the coating film having a thickness of 0.1 to 5 .mu.m, the diameter of the fibers being in the range of 10 to 200 .mu.m and the diameter of the whiskers being in the range of 0.5 to 5 .mu.m.

Fiber-reinforced ceramics comprising at least one of fibers and whiskers distributed in a sintered ceramic matrix, the ceramic matrix being composed mainly of SiC, Si.sub.3 N.sub.4 or Si.sub.6-z Al.sub.z O.sub.z N.sub.8-z where 0<z.ltoreq.4, the fibers and the whiskers consisting essentially of at least one of SiC, Si.sub.3 N.sub.4, or Si.sub.6-z Al.sub.z O.sub.z N.sub.8-z where 0<z.ltoreq.4, a coating comprising C, B or BN containing 10-50 mol % of SiC or Si.sub.3 N.sub.4 being provided on surfaces of the fibers and the whiskers, and the diameter of the fibers or the whiskers having the coating film being at least 5 times the average particle size of the sintered matrix and the length of the fibers or the whiskers having the coating film being at least 30 times the diameter of the fibers or the whiskers;

• the coating film having a thickness of 0.1 to 5 .mu.m, the diameter of the fibers being in the range of 10 to 200 .mu.m and the diameter of the whiskers being in the range of 0.5 to 5 .mu.m.

Fiber-reinforced ceramics comprising at least one of fibers and whiskers distributed in a sintered ceramic matrix, the ceramic matrix being composed of SiC, Si.sub.3 N.sub.4 or Si.sub.6-z Al.sub.z O.sub.z N.sub.8-z where 0<z.ltoreq.4, the fibers and the whiskers consisting essentially of at least one of SiC, Si.sub.3 N.sub.4, or Si.sub.6-z Al.sub.z O.sub.z N.sub.8-z where 0<z.ltoreq.4, a coating film comprising C, B or BN containing 10-50 mol % SiC or Si.sub.3 N.sub.4 being provided on surfaces of the fibers and the whiskers, said fiber-reinforced ceramics exhibiting a fracture toughness, K.sub.1c, of at least 10 MN/m.sup.3/2 and a bending strength at room temperature of at least 50 kg/mm.sup.2 ;

• said coating film having a thickness of 0.1 to 5 .mu.m, the diameter of the fibers being i the range of 10 to 200 .mu.m and the diameter of the whiskers being in the range of 0.5 to 5 .mu.m.

Fiber-reinforced ceramics comprising at least one of fibers and whiskers distributed in a sintered ceramic matrix, the ceramic matrix being composed mainly of Si3N.sub.4 and containing 1 to 20% by volume of at least one of Al.sub.2 O.sub.3 and Y.sub.2 O.sub.3, the fibers and the whiskers consisting essentially of at least one of SiC, Si.sub.3 N.sub.4, or Si.sub.6-z Al.sub.z O.sub.z N.sub.8-z where 0<z.ltoreq.4, and a coating film comprising C, B or BN containing 10-50 mol % SiC or Si3N.sub.4 being provided on surfaces of the fibers and the whiskers;

• the coating film having a thickness of 0.1 to 5 .mu.m, the diameter of the fibers being in the range of 10 to 200 .mu.m and the diameter of the whiskers being in the range of 0.5 to 5 .mu.m.

Fiber-reinforced ceramics consisting essentially of at least one of fibers and whiskers distributed in a sintered ceramic matrix, the ceramic matrix being composed mainly of SiC, Si.sub.3 N.sub.4 or Si.sub.6-z Al.sub.z O.sub.z N.sub.8-z where 0<z.ltoreq.4, the fibers and the whiskers consisting essentially of at least one of SiC, Si.sub.3 N.sub.4, or Si.sub.6-z Al.sub.z O.sub.z N.sub.8-z where 0<z.ltoreq.4, and a coating film of C, B or BN containing 10-50 mol % SiC or Si.sub.3 N.sub.4 being provided on surfaces of the fibers and the whiskers;

• the coating film having a thickness of 0.1 to 5 .mu.m, the diameter of the fibers being in the range of 10 to 200 .mu.m and the diameter of the whiskers being in the range of 0.5 to 5 .mu.m.

Fiber-reinforced ceramics comprising at least one of fibers and whiskers distributed in a sintered ceramic matrix, the ceramic matrix being composed mainly of SiC, Si.sub.3 N.sub.4, or Si.sub.6-z Al.sub.z O.sub.z N.sub.8-z where 0<z.ltoreq.4, or the ceramic matrix being composed mainly of at least one of SiC and Si.sub.3 N.sub.4 and containing 1 to 20% by volume of at least one of Al.sub.2 O.sub.3 and Y.sub.2 O.sub.3, the fibers and the whiskers consisting essentially of at least one of SiC, Si.sub.3 N.sub.4, or Si.sub.6-z Al.sub.z O.sub.z N.sub.8-z where 0<z.ltoreq.4, a coating film comprising C, B or BN containing 10-50 mol % of SiC or Si.sub.3 N.sub.4 being provided on surfaces of the fibers and the whiskers, and a ratio of distances l between the fibers or the whiskers to diameter d of the fibers or the whiskers having the coating film, l/d, being 0.5 to 2 and the diameter of the fibers or the whiskers having the coating film being at least 5 times the average particle size of the sintered matrix and the length of the fibers or the whiskers having the coating film being at least 30 times the diameter of the fibers or the whiskers;

• the coating film having a thickness of 0.1 to 5 .mu.m, the diameter of the fibers being in the range of 10 to 200 .mu.m and the diameter of the whiskers being in the range of 0.5 to 5 .mu.m.