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Oxidation and Fracture Strength of High‐Purity Reaction‐Bonded Silicon Nitride

1989; Wiley; Volume: 72; Issue: 9 Linguagem: Inglês

10.1111/j.1151-2916.1989.tb06302.x

1551-2916

J. S. Haggerty, A. Lightfoot, J. E. Ritter, Paul A. Gennari, S. V. Nair,

Metal and Thin Film Mechanics

Reaction‐bonded Si 3 N 4 (RBSN) made from high‐purity Si powder is unusually resistant to degradation caused by exposures to air for up to 50 h at temperatures up to 1400°C. The weight gain during oxidation of this SiH 4 ‐originating RBSN is approximately 10 times less than conventional RBSN. Contrary to normally observed strength degradations, room‐temperature strengths of this high‐purity, oxidized RBSN (avg = 435 MPa, max. = 668 MPa) remained at their unusually high, as‐processed levels after 1000° and 1400°C oxidizing exposures. Fracture toughness values were unaffected by oxidation ( K IC = 2.3 to 2.4 MPa · m 1/2 ). This superior oxidation resistance results from the high purity and the small diameter pore channels (0.01 to 0.06 μm) achieved in this SiH 4 ‐originating RBSN.