Abstract: The composite includes inorganic fiber for reinforcement and a matrix of 40 to 95% by weight of silicon carbide ceramic and 5 to 60% by weight of an oxide phase dispersed in the silicon carbide ceramic. The oxide phase forms a continuous network structure in the matrix and includes ZrSiO4, BaO—MgO—Al2O3—SiO2 glass ceramic or Sro—Al2O3—SiO2 glass ceramic. The matrix surrounds and fills voids between the inorganic fiber.

Abstract: A matrix for high-performance ceramic matrix composite containing inorganic fiber for reinforcement, which comprises silicon carbide ceramic and an oxide phase having dispersed in the solicon carbide ceramic.

Abstract: A silicon nitride powder which provides a water-based slurry with a low viscosity and a high powder concentration. The silicon nitride powder has a specific surface area of 6 to 25 m.sup.2 /g, a number of coarse particles of coarse primary particles, agglomerated particles and/or fused particles, and having a size of 3 to 50 .mu.m, of not more than 1000 per 1 cm.sup.3 of the powder, a number of foreign metallic particles, having a size of more than 20 .mu.m, of not more than 3 per 1 cm.sup.3 of the powder, and a number of foreign metallic particles, having a size of 10 to 20 .mu.m, of not more than 15 per 1 cm.sup.3 of the powder.

Abstract: A SiAlON-based sintered body having a high mechanical strength and fracture toughness, as well as an excellent oxidation resistance, is provided. The SiAlON-based sintered body comprises 5 to 50% by weight of a first crystal phase of RE.alpha.-SiAlON represented by RE.sub.x (Si, Al).sub.12 (O, N).sub.16, where RE stands for at least one modifying rare earth element selected from the group consisting of Ho, Er, Tm, Yb and Lu and x has a value of 0<x.ltoreq.2, 30 to 90% by weight of a second crystal phase of .beta.-SiAlON represented by Si.sub.6-z Al.sub.z O.sub.z N.sub.8-z (0<z.ltoreq.4.2), and 1 to 50% by weight of a third crystal phase containing at least one rare earth element RE selected from the group consisting of Ho, Er, Tm, Yb and Lu, optionally together with 1 to 20% by weight of a crystal phase of .alpha.-silicon nitride.

Abstract: A fine particulate .alpha.-Sialon powder with a narrow particle size distribution, thus having an excellent sinterability, can be produced by using as the starting materials (a) amorphous silicon nitride, (b) metallic aluminum or aluminum nitride, and (c) an oxide of a metal which can be incorporated in the interstices of .alpha.-Sialon lattice or a metal compound capable of forming such a metal oxide upon thermal decomposition, and optionally, (d) an oxygen-containing compound of alumina or silicon, followed by heat treatment of the resultant mixture.