Process for the manufacture of friable silicon nitride bodies
First Claim
1. A process for producing a friable silicon nitride body comprising (i) infiltrating a reaction bonded silicon nitride body which has a density of greater than about 1.5 g/cc, outside surfaces, and a central core, with a fluid which will expand upon freezing, (ii) freezing the fluid in the infiltrated body so that the fluid in the outside surfaces of the body freezes before the fluid in the central core, and (iii) thawing the frozen body of silicon nitride.
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Abstract
A friable silicon nitride body is prepared by infiltrating a non-friable silicon nitride body with a fluid which expands upon freezing, rapidly freezing the fluid, and thawing the frozen fluid. Silicon nitride flakes and chunks obtained with only light pressure on the friable body may then be final milled to a desired particle size more rapidly and with less energy input than with conventionally processed silicon nitride. The silicon nitride body may have a higher density than has previously been used to prepare silicon nitride powders, thereby preventing the generation of potentially hazardous whiskers in the final powder product.
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11 Claims
- 1. A process for producing a friable silicon nitride body comprising (i) infiltrating a reaction bonded silicon nitride body which has a density of greater than about 1.5 g/cc, outside surfaces, and a central core, with a fluid which will expand upon freezing, (ii) freezing the fluid in the infiltrated body so that the fluid in the outside surfaces of the body freezes before the fluid in the central core, and (iii) thawing the frozen body of silicon nitride.
- 8. A process for preparing a friable silicon nitride body comprising (i) infiltrating a body of non-friable reaction bonded silicon nitride with water by immersing the bed in water, (ii) rapidly freezing the water-infiltrated body by immersing it into a liquified gas, and (iii) thawing the body to at least about room temperature.
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