Mitsubishi Gas Chemical Company, Inc.

Agency of Industrial Science and Technology

Kansei Izaki

Takamasa Kawakami

Takashi Suzuki

Takeshi Koyama

Akira Mori

Rieko Nakano

Masami Orisaku

Koichi Niihara

Kazuhiro Ando

Fumihiro Wakai

Yasuharu Kodama

Kouichi Hakkei

There are disclosed in process for shaping ceramic composites which comprises shaping a sintered silicon nitride-silicon carbide composite material having a microstructure formed predominantly of equiaxed grains with an average grain size of 2 .mu.m or below and a silicon carbide content of 10-50% by volume, obtained by liquid-phase sintering, at least 40% by volume of the silicon nitride in the material being in the .beta.-phase, by superplastically deforming said material at a strain rate of 10.sup.-6 sec.sup.-1 to 10.sup.-1 sec.sup.-1 under application of tensile stress or compressive stress in a superplastic temperature region of 1400.degree.-1700.degree. C., and a process for shaping ceramic composites which comprises shaping said sintered composite material by superplastic deformation as described above and then heat-treating the shaped article obtained in a non-oxidizing atmosphere under normal or applied pressure at 1000.degree.-2300.degree. C.

Process for shaping ceramic composites

A sintered silicon nitride-silicon carbide composite material is provided comprising a matrix phase of silicon nitride and silicon carbide where silicon carbide grains having an average diameter of not more than 1 .mu.m are present at grain boundaries of silicon nitride grains and silicon carbide grains having a diameter of several nanometers to several hundred nanometers, typically not more than about 0.5 micrometers, are dispersed within the silicon nitride grains and a dispersion phase where (a) silicon carbide grains having an average diameter of 2 to 50 .mu.m and/or (b) silicon carbide whiskers having a short axis of 0.05 to 10 .mu.m and an aspect ratio of 5 to 300 are dispersed in the matrix phase. A process for the production of the composite material is also provided.

Silicon nitride-silicon carbide composite material and process for

The invention relates to a sintered silicon nitride-silicon carbide composite material excellent in toughness and strength and to a process for producing the same. The present sintered composite material is substantially formed of silicon nitride predominantly in .beta.-phase and about 5 to 35% by weight of silicon carbide predominantly in .beta.-phase, which is characterized by the microstructure such that the silicon nitride is in the form of fine grains comprising elongated grains, 0.2 to 1.0 .mu.m in length of minor axis and 1 to 10 .mu.m in length of major axis, and equiaxed grains, 1 .mu.m or below in average size, and the silicon carbide is in the form of equiaxed grains, 1 .mu.m or below in average size, said silicon carbide grains being uniformly dispersed. Having a three-point flexural strength of at least 95 kg/mm.sup.2 and a fracture toughness (K.sub.IC) of at least 54 MN/m.sup.3/2, the present sintered material is excellent in toughness and strength. The process for producing such a material is disclosed in detail.

Fine silicon nitride powders, fine silicon carbide powders, or fine powdery mixture of silicon nitride and silicon carbide are prepared by vapor phase reaction of an aminosilane compound, a cyanosilane compound, a silazane compound, an alkoxysilane compound or a siloxane compound and heat treatment of the resulting fine powders in a non-oxidizing gas atmosphere.

Process for preparing silicon nitride, silicon carbide or fine powdery

Fine spherical amorphous powder represented by the general formula:

Growing community of inventors

Niigata, Japan

Kansei Izaki