Kabushiki Kaisha Toshiba

Yoshiyuki Ohnuma

Takeyuki Yonezawa

Yasuhiro Goto

Hiroshi Inoue

Akihiko Tsuge

Toshiaki Mizutani

Jen Ando

According to the present invention, there is provided a fiber-reinforced silicon nitride ceramic prepared by sintering a starting composition containing silicon nitride, at least one sintering additive and silicon carbide fiber or a fiber containing silicon carbide as a major constituent (to be referred to as a silicon carbide fiber hereinafter), characterized in that said silicon carbide fiber has a length of 200 .mu.m or more, and is contained 5 to 50 wt %, and said sintering additive is contained 0.1 to 30 wt % and is selected from the group consisting of an oxide, a nitride, and a carbide of titanium or zirconium, a composite oxide of titanium and zirconium, magnesia, and spinel. When the contents of the fibers and the sintering addtives fall within the ranges according to the present invention, a high strength and a large toughness value are simultaneously obtained.

Fiber-reinforced silicon nitride ceramic

A silicon nitride-ceramic is composed of a sintered body including silicon nitride and an additive, and has a columnar crystal of .beta. type silicon nitride substantially parallel to one plane. A method for manufacturing a silicon nitride-ceramic comprises the steps of forming first powder including a needle-shaped crystal of .beta. type silicon nitride by mixing the needle-shaped crystal of the .beta. type silicon nitride with second silicon nitride powder mainly of .alpha. type including an additive, or by heating the second silicon nitride powder at temperature 1500.degree. to 1750 .degree. C. in advance; and sintering the first powder at a predetermined temperature under non-oxidation atmosphere.

Silicon nitride-ceramic and a manufacturing method therof

A silicon carbide sintered body containing not less than 0.03% by weight of boron, a total of not more than 0.3% by weight of metallic element impurities including the boron, not more than 1.0% by weight of free carbon, a total of not more than 0.15% by weight of non-metal impurities other than the free carbon, and the balance essentially consisting of silicon carbide, and having a density of not less 3.10 g/cm.sup.3. The sintered body is manufactured by heating a molding of a mixture containing a silicon carbide powder, a boron-containing sintering assistant, and a carbon-containing oxygen scavenger to a sintering temperature. The molded body is maintained at a temperature lower than the sintering temperature during the heating process until an oxide film covering the silicon carbide powder is substantially removed by the oxygen scavenger, and the molded body is then sintered at the sintering temperature under a non-pressurized condition.

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Kawasaki, Japan

Yoshiyuki Ohnuma