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Fabrication and Microstructures of MoSi 2 Reinforced–Si 3 N 4 Matrix Composites
Author(s) -
Petrovic John J.,
Pena Maria I.,
Kung H. Harriett
Publication year - 1997
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1997.tb02953.x
Subject(s) - materials science , microstructure , fabrication , composite material , phase (matter) , volume fraction , composite number , particle (ecology) , cermet , amorphous solid , thermal expansion , intermetallic , hot pressing , sintering , ceramic , crystallography , chemistry , oceanography , organic chemistry , pathology , geology , alloy , medicine , alternative medicine
Details of the fabrication and microstructures of hot‐pressed MoSi 2 reinforced–Si 3 N 4 matrix composites were investigated as a function of MoSi 2 phase size and volume fraction, and amount of MgO densification aid. No reactions were observed between MoSi 2 and Si 3 N 4 at the fabrication temperature of 1750°C. Composite microstructures varied from particle–matrix to cermet morphologies with increasing MoSi 2 phase content. The MgO densification aid was present only in the Si 3 N 4 phase. An amorphous glassy phase was observed at the MoSi 2 –Si 3 N 4 phase boundaries, the extent of which decreased with decreased MgO level. No general microcracking was observed in the MoSi 2 –Si 3 N 4 composites, despite the presence of a substantial thermal expansion mismatch between the MoSi 2 and Si 3 N 4 phases. The critical MoSi 2 particle diameter for microcracking was calculated to be 3 μm. MoSi 2 particles as large as 20 μm resulted in no composite microcracking; this indicated that significant stress relief occurred in these composites, probably because of plastic deformation of the MoSi 2 phase.