Process Development and Property Evaluation of Organosilicon Infiltrated Reaction Sintered Silicon Nitride (RSSN).
Abstract
The porous nature of RSSN limits its performance as a structural material because the pores act as strength limiting flaws and facilitate internal oxidation. The objective of this program was to develop an impregnation and pyrolysis process to fill these pores with silicon carbide and/or nitride derived from organosilicon precursors. Seven organosilicon precursors were evaluated as infiltrants using reaction bonded silicon nitride (RSSN) ceramics of different densities. Methylsilazane in decalin solvent was the best infiltrant. Pyrolysis of methylsilazane resulted in a fine-grained microstructure containing 1 micron closed pores. This grainy deposit bonded well to the pore walls in RSSN, and for this reason the methylsilazane is considered to be the best candidate organosilicon for improving the properties of RSSN. During pyrolysis all organosilicon precursors exhibit a considerable volume of shrinkage and weight loss causing residual surface material to flake off the RSSN surface. Thin coatings were applied to RSSN samples to effectively plug the surface porosity. This resulted in significant improvements in oxidation resistance in both high and medium density RSSN materials. A 70% increase in the strength of low density foam RSSN was obtained. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1982
- Accession Number
- ADA111461
Entities
People
- R. A. Markle
- R. R. Wills
- W. E. Hauth
Organizations
- Battelle Memorial Institute