Development of Silicon Nitride of Improved Toughness.
Abstract
The application of reaction sintered Si3N4 energy absorbing surface layers to hot-pressed Si3N4 was investigated. The surface layer was formed by in-place nitridation of silicon powder. It was found that reaction sintered Si3N4 layers of 1 mm thickness, fabricated from either -100, +200, -200, or -325 mesh Si powder and nitrided in 96% N2/4% H2 so that approximately 20-25 vol % unnitrided Si remained in the layer, resulted in a sevenfold iNCrease in ballistic impact resistance of a 0.64 cm thick hot-pressed Si3N4 substrate from RT to 1370 C. Both Nc-132 Si3N4, with mgO additive, and NCX-34 Si3N4, with Y2O3 additive, were evaluated as substrate material. The finer grain size -200 and -325 mesh nitrided Si layers were found to be preferable for their smoothness and relatively high density. It was found that nitriding in N2/H2 mixtures, rather than pure N2, resulted in a microstructure that did not substantially degrade the strength of the hot-pressed Si3N4 substrate.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 02, 1979
- Accession Number
- ADA077026
Entities
People
- J. J. Brennan
Organizations
- United Technologies Corporation