Basic Research on Technology Development for Sintered Ceramics
Abstract
Fired compacts of pure Si3N4 powders, having average particle sizes between 0.15 and 0.4 microns, undergo large (approx. 15%) weight losses and considerable grain growth in the absence of macroscopic shrinkage. The nearly similar weight loss of Si3N4 compacts made from the same starting powder but which contained different oxygen contents, 3.14 and 0.7 wt%, suggests that the major portion of material loss is caused by thermal decomposition of Si3N4 and not by an oxygen-removal reaction. This information leads to the conclusion that the sintering of pure Si3N4 is prevented by high vapor transport and/or thermal decomposition. The need for Si3N4 powder with higher specific surface area and purity than that commercially available led to the synthesis, on a laboratory scale, of amorphous Si3N4 powders with specific surface areas as high as 80 sq. m/g by the reaction between silane and ammonia. At temperatures above 600 C, it is difficult to prepare Si3N4 powders free of silicon. Powders containing free silicon cannot be completely nitrided at temperatures below 1400 C in nitrogen. However, preliminary results indicate that Si3N4 powder free of elemental silicon and low in oxygen can be synthesized by the reaction between silane and ammonia in a temperature interval between about 530 and 570 C.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1976
- Accession Number
- ADA139197
Entities
People
- C. D. Greskovich
- J. H. Rosolowski
- S. Prochazka
Organizations
- General Electric