Thermodynamic calculations for the formation of SiC-whisker-reinforced Si sub 3 N sub 4 ceramics

Abstract

Thermodynamic equilibria were calculated to determine optimum fabrication conditions for SiC-whisker-reinforced Si{sub 3}N{sub 4} composite ceramics. Results of calculations indicate that pressureless sintering in a nitrogen atmosphere of 0.1 MPa may be performed at temperatures up to 2,123 K (1,850{degree}C) without whisker or matrix degradation. In addition, gas pressure sintering at temperatures up to 2,373 K (2,100{degree}C) requires a nitrogen pressure of 1 to 10 MPa. Hot isostatic pressing (total pressure {ge} 100 MPa) at 2,273 K (2,000{degree}C) can yield undegraded composite materials only when the nitrogen partial pressure in a gas mixture with an inert gas is kept between 1 to 10 MPa.