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Characterization of HIP'ed, High Purity Si3N4 Grain Boundaries

Published online by Cambridge University Press:  25 February 2011

Ping Lu
Affiliation:
Department of Materials Science, The State University, Piscataway, NJ 08855-0909
S.C. Danforth
Affiliation:
Department of Ceramic Engineering, Rutgers, The State University, Piscataway, NJ 08855-0909
W.T. Symons
Affiliation:
A. C. Rochester, Div. of General Motors, 1300 N. Dort Hwy, Flint, MI 48556
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Abstract

Laser synthesized, ultra-fine, amorphous, Si3N4 powders were densified via HIP'ing without any oxide sintering aids. Exposed samples were made from powder that had been exposed to the atmosphere, thereby picking up an oxide surface layer, and unexposed samples were made from powders processed entirely under glove box conditions, i.e. without oxygen contamination. TEM (and sintering) studies indicate that the exposed samples HIP'ed at temperatures in excess of the melting point of Si02, densified via a solution-reprecipitation mechanism, with a resultant intergranular glassy phase of high purity Si02. In contrast, unexposed samples had to be HIP'ed to 2050°C to achieve a density of ∼70 %p Th. These samples consisted of equiaxed β-Si3N4 grains, with localized high density regions where no inter-granular phase (crystalline or glassy) was detected to within 0.66 nm.

Type
Research Article
Copyright
Copyright © Materials Research Society 1993

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References

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