Process for producing silicon nitride based articles of high fra

Details Process for producing silicon nitride based articles of high fra Process for producing silicon nitride based articles of high fra

1989-12-28

1991-09-10

Derrington, James

Plastic and nonmetallic article shaping or treating: processes

Including step of generating heat by friction

264 63, 264 65, 264332, 501 92, 501 95, C04B 3558

Patent

active

050471864

ABSTRACT:
A process for producing a silicon nitride-based article of improved fracture toughness and strength. The process involves densifying to at least 98% of theoretical density a mixture including (a) a bimodal silicon nitride powder blend consisting essentially of about 10-30% by weight of a first silicon nitride powder of an average particle size of about 0.2 .mu.m and a surface area of about 8-12 m.sup.2 /g, and about 70-90% by weight of a second silicon nitride powder of an average particle size of about 0.4-0.6 .mu.m and a surface area of about 2-4 m.sup.2 /g, (b) about 10-50 percent by volume, based on the volume of the densified article, of refractory whiskers or fibers having an aspect ratio of about 3-150 and having an equivalent diameter selected to produce in the densified article an equivalent diameter ratio of the whiskers or fibers to grains of silicon nitride of greater than 1.0, and (c) an effective amount of a suitable oxide densification aid. Optionally, the mixture may be blended with a binder and injection molded to form a green body, which then may be densified by, for example, hot isostatic pressing.

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M. L. Huckabee et al., "Silicon Carbide Whisker Reinforced Silicon Nitride", Proc. 26th Automotive Engineers, Inc., Warrendale, Pa. (1989).
Ube Industries, Ltd., Silicon Nitride Technical Report, data sheet, "Effect of Binary Powder Mixing".

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