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Processing and Creep Performance of Silicon Carbide Whisker-Reinforced Silicon Nitride

Published online by Cambridge University Press:  25 February 2011

John. R. Porter ,
F. F. Lange  and
A. H. Chokshi
John. R. Porter
Affiliation:
Rockwell International Science Center, 1049 Camino Dos Rios, P.O. Box 1085, Thousand Oaks, CA 91360
F. F. Lange
Affiliation:
Materials Program, University of California, Santa Barbara, CA 93106.
A. H. Chokshi
Affiliation:
Department of Mechanical Engineering, University of California, Davis, CA 95616.
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Abstract

Silicon carbide whisker reinforcement can significantly reduce creep rates in polycrystalline alumina [1], but the system SiC/Al2O3 is thermodynamically unstable in air and oxidizes to mullite during creep testing [2]. The system SiC/Si3N4 was investigated as a potentially more stable, high temperature structural composite. Silicon carbide whiskers were successfully incorporated into a silicon nitride matrix doped with alumina and yttria. Processing involved mixing dispersed slurries of silicon carbide and silicon nitride, adding the dopants as a solution of their nitrates and subsequently increasing the pH to precipitate the additive hydroxides. The resulting slurries were filter pressed at room temperature and hot pressed at 1650°C in graphite dies to full density. X-ray diffraction and transmission electron microscopy confirmed the presence of β-Si3N4, α-SiC and trace quantities of α-Si3N4, confirming that the α-β Si3N4 reaction occurred. An additional, as yet unidentified, minor phase was also detected.

Whisker reinforcement was shown to increase the room temperature flexural strength and fracture toughness but high temperature creep performance was unaffected by whisker reinforcement.

Type
Articles
Information
MRS Online Proceedings Library (OPL) , Volume 78: Symposium E – Advances in Structural Ceramics , 1986 , 289
Copyright
Copyright © Materials Research Society 1987

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References

REFERENCES

1. Chokshi, A.H. and Porter, J.R., J. Am. Ceram. Soc. 68, C–144 (1985).Google Scholar
2. Porter, J.R. and Chokshi, A.H., in Ceramic Microstructures '86: The Role of Interfaces, edited by Pask, J. A. and Evans, A. G. (Plenum, New York, 1987), in press.Google Scholar
3. Porter, J.R., Lange, F.F. and Chokshi, A.H., Ceramic Bull., in press.Google Scholar
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