Kabushiki Kaisha Kobe Seiko Sho

Kabushiki Kaisha Seiko Sho

Tsuneo Tatsuno

Hiroshi Okada

Takao Fujikawa

Masato Moritoki

Katuhiko Honma

Moriyoshi Kanamaru

Takehiro Tsuchida

Katsuhiko Honma

Noboru Ohyama

The specification describes a method for producing high density sintered silicon nitride (Si.sub.3 N.sub.4) having a relative density of at least 98%. In a first step, silicon nitride powder is compacted into a desired shape. It is then pre-sintered in a second step, generally, under normal pressure to obtain a presintered body having a relative density of at least 92%. In a third step, the presintered body is subjected to a hot isostatic pressing (HIP) in an inert gas atmosphere of 1500.degree.-2100.degree. C. and of nitrogen gas partial pressure of at least 500 atm. Since the presintering does not require any capsule, it is possible to produce high density sintered Si.sub.3 N.sub.4 of complex configurations. As a sintering aid, Y.sub.2 O.sub.3 --Al.sub.2 O.sub.3 --MgO system sintering aid is particularly effective. To improve the strength of sintered Si.sub.3 N.sub.4, it is effective to add a heat treatment step after the HIP and maintain the temperature of the sintered Si.sub.3 N.sub.4 above 500.degree. C. for a while. Between the second and third steps, the temperature of the presintered body is preferably maintained above 500.degree. C. These temperature controls are effective not only to improve the strength of sintered Si.sub.3 N.sub.4 but also to save the thermal energy and to shorten the production cycle.

Method for producing high density sintered silicon nitride(Si.sub.3 N.sub.4

The specification describes a method for producing high density sintered silicon nitride(Si.sub.3 N.sub.4) having a relative density of at least 98%. In a first step, silicon nitride powder is compacted into a desired shape. It is then presintered in a second step, generally, under normal pressure to obtain a presintered body having a relative density of at least 92%. In a third step, the presintered body is subjected to a hot isostatic pressing(HIP) in an inert gas atmosphere of 1500-2100.degree. C. and of nitrogen gas partial pressure of at least 500 atm. Since the presintering does not require any capsule, it is possible to produce high density sintered Si.sub.3 N.sub.4 of complex configurations. As a sintering aid, Y.sub.2 O.sub.3 -Al.sub.2 O.sub.3 -MgO system sintering aid is particularly effective. To improve the strength of sintered Si.sub.3 N.sub.4, it is effective to add a heat treatment step after the HIP and maintain the temperature of the sintered Si.sub.3 N.sub.4 above 500.degree. C. for a while. Between the second and third steps, the temperature of the presintered body is preferably maintained above 500.degree. C. These temperature controls are effective not only to improve the strength of sintered Si.sub.3 N.sub.4 but also to save the thermal energy and to shorten the production cycle.

Method for producing high density sintered silicon nitride (SI.sub.3 N.sub.

A mixed powder containing: 5-30 wt % of SiC whiskers; 3-30 wt % of a sintering auxiliary agent composed of one kind or more of oxides of Mg, Si, Ca, Ti, Zr, Cr, Ni, Y and rare earth elements; and an Al.sub.2 O.sub.3 powder as a base material; or further containing 0.5-40 wt % of one kind or more of compounds composed of one kind or more of transient elements in the groups IVa, Va, and VIa of the periodic table and one kind or more of C, N and B, are compacted and subjected to pressureless-sintering in a nitrogen containing inert gas atmosphere at a temperature between 1500.degree. and 1900.degree. C. With this method, the SiC whiskers containing Al.sub.2 O.sub.3 based ceramic material, which is densified and has a sufficient strength and toughness, can be formed in a complex shape and a large size.

Alumina based ceramic material and method of manufacturing the same

The specification describes a method for producing high density sintered silicon nitride(Si.sub.3 N.sub.4) having a relative density of at least 98%. In a first step, silicon nitride powder is compacted into a desired shape. It is then presintered in a second step, generally, under normal pressure to obtain a presintered body having a relative density of at least 92%. In a third step, the presintered body is subjected to a hot isostatic pressing(HIP) in an inert gas atmosphere of 1500-2100.degree. C. and of nitrogen gas partial pressure of at least 500 atm. Since the presintering does not require any capsule, it is possible to produce high density sintered Si.sub.3 N.sub.4 of complex configurations. As a sintering aid, Y.sub.2 O.sub.3 --Al.sub.2 O.sub.3 --MgO system sintering aid is particularly effective. To improve the strength of sintered Si.sub.3 N.sub.4, it is effective to add a heat treatment step after the HIP and maintain the temperature of the sintered Si.sub.3 N.sub.4, above 500.degree. C. for a while. Between the second and third steps, the temperature of the presintered body is preferably maintained above 500.degree. C. These temperature controls are effective not only to improve the strength of sintered Si.sub.3 N.sub.4 but also to save the thermal energy and to shorten the production cycle.

Method for producing high density sintered silicon nitride (Si.sub.3 N.sub.

Al.sub.2 O.sub.3 composites, process for producing them and throw-away

A method for producing a high strength sintered silicon carbide, the method comprising: molding a mixture of silicon carbide powder and a sintering aid into a green compact of a predetermined shape: preliminarily sintering the green compact to obtain a preliminarily sintered compact having a relative density higher than 80%; charging the preliminarily sintered compact in a HIP equipment without using a capsule; and subject the preliminarily sintered compact to a HIP treatment in a high-temperature and high-pressure N.sub.2 gas atmosphere maintaining a pressure higher than 500 atms and a temperature in the range of 1400.degree.-2300.degree. C.

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Kobe, Japan

Tsuneo Tatsuno