Claims
- 1. A method for improving the impact strength of a dense silicon nitride article which comprises:
- a. applying a layer of a silicon powder slurry to at least one surface of the article;
- b. heating the slurry coated article to remove the liquid slurry constituent;
- c. nitriding the slurry layer to partially convert the silicon powder to silicon nitride and simultaneously bond the silicon powder layer to the dense silicon nitride article to form a porous crushable surface layer comprised of silicon nitride containing from 15-45% of unnitrided silicon.
- 2. A method as in claim 1 wherein the thickness of the surface layer is about 1 mm.
- 3. A method as in claim 1 wherein the surface layer has a residual porosity of from about 20 to about 50 percent.
- 4. A method as in claim 1 wherein a protective, thin, dense layer of pyrolytic silicon nitride is applied to the porous surface layer after the nitriding step.
- 5. An impact resistant silicon nitride article which comprises:
- a fully dense silicon nitride substrate having a surface layer bonded thereto, said surface layer being a porous mixture of silicon and silicon nitride, said surface layer having 20-50% porosity with the nonporous remainder comprising 15-45% silicon, balance essentially silicon nitride.
BACKGROUND OF THE INVENTION
This application is a Continuation-In-Part of application U.S. Ser. No. 869,331 filed Jan. 13, 1978 and now abandoned.
Government Interests
The invention described herein was made in the course of or under a contract with the National Aeronautics and Space Administration.
US Referenced Citations (7)
Non-Patent Literature Citations (2)
Entry |
Poponiak et al, "Thick Wear Resistant Coatings for Silicon Devices", IBM Tech. Disclosure Bulletin, vol. 18, No.12 May, 1976. |
Poponiak et al. "Formation of Thick Si.sub.3 N.sub.4 or Si.sub.x O.sub.y N.sub.z On Sl Substrate by Anodnitridization", vol. 19, No. 3, Aug. 1976. |
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
869331 |
Jan 1978 |
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