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Preparation and evaluation of silicon nitride matrices for silicon nitride-SiC fiber compositesContinuous silicon carbide (SiC) fiber was added to three types of silicon nitride (Si3N4) matrices. Efforts were aimed at producing a dense Si3N4 matrix from reaction-bonded silicon nitride (RBSN) by hot-isostatic-pressing (HIP) and pressureless sintering, and from Si3N4 powder by hot-pressing. The sintering additives utilized were chosen to allow for densification, while not causing severe degradation of the fiber. The ceramic microstructures were evaluated using scanning optical microscopy. Vickers indentation was used to determine the microhardness and fracture toughness values of the matrices. The RBSN matrices in this study did not reach more than 80 percent of theoretical density after sintering at various temperatures, pressures, and additive levels. Hot-pressing Si3N4 powder produced the highest density matrices; hardness and toughness values were within an order of magnitude of the best literature values. The best sintering aid composition chosen included Y2O3, SiO2, and Al2O3 or AlN. Photomicrographs demonstrate a significant reduction of fiber attack by this additive composition.
Document ID
19890014307
Acquisition Source
Legacy CDMS
Document Type
Thesis/Dissertation
Authors
Axelson, Scott R. (Alfred Univ. NY, United States)
Date Acquired
September 5, 2013
Publication Date
February 1, 1988
Subject Category
Nonmetallic Materials
Report/Patent Number
NAS 1.26:184798
NASA-CR-184798
Accession Number
89N23678
Funding Number(s)
CONTRACT_GRANT: NCC3-59
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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