Plastic and nonmetallic article shaping or treating: processes – Including step of generating heat by friction
Patent
1988-09-26
1997-02-18
Derrington, James
Plastic and nonmetallic article shaping or treating: processes
Including step of generating heat by friction
264 62, 264 85, 264570, 264325, C04B 35584
Patent
active
056038763
ABSTRACT:
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.
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Title of Document is: Mechanical Properties of Hot-Pressed Silicon Nitride with Different Grain Structures.
Journal of Materials Science 11 (1976) pp. 1103-1107, "Pressure sintering of Si.sub.3 N.sub.4, M. Mitomo".
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Fujikawa Takao
Honma Katuhiko
Moritoki Masato
Okada Hiroshi
Tatsuno Tsuneo
Derrington James
Kabushiki Kaisha Kobe Seiko Sho
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