Title

Effect of AlN and Al2O3 Additions on the Phase Relationships and Morphology of SiC Part II: Microstructural Observations

Abstract

Additions of AlN and Al2O3 to -SiC hot pressed at 2100°C strongly effect the - to -SiC phase transformation and the resultant -SiC polytypes which are formed. Scanning and transmission electron microscopy were utilized to investigate the microstructural changes occurring in SiC due to these additions and to correlate these observations to their mechanical properties. The results suggest that Al2O3 additions stabilize the formation of the 6H-polytype of -SiC which grows rapidly into an elongated plate-like morphology, while AlN additions stabilize the 2H-polytype of -SiC resulting in fine equiaxed 2H-SiC: AlN solid solution grains. It is speculated that the elongated growth of 6H-SiC with Al2O3 additions can be controlled through the simultaneous addition of AlN. The formation of 2H-SiC : AlN solid solution grains inhibits the growth of the 6H-SiC grains since AlN(2H) will not go into solid solution in the SiC(6H) structure, effectively pinning the growth of the 6H-SiC grains.

Department(s)

Materials Science and Engineering

Sponsor(s)

United States. Department of Energy

Keywords and Phrases

SiC; Microstructural Changes

Library of Congress Subject Headings

Aluminum nitride
Aluminum oxide

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 1999 Springer Verlag, All rights reserved.


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