Chapter 27. Processing and Properties of SiC Whisker- and Particulate-Reinforced Reaction Bonded Si3N4
- John B. Wachtman Jr
Published Online: 28 MAR 2008
Copyright © 1991 The American Ceramic Society, Inc.
Proceedings of the 15th Annual Conference on Composites and Advanced Ceramic Materials, Part 1 of 2: Ceramic Engineering and Science Proceedings, Volume 12, Issue 7/8
How to Cite
Lightfoot, A., Ewart, L., Haggerty, J., Cai, Z. Q., Ritter, J. and Nair, S. (1991) Processing and Properties of SiC Whisker- and Particulate-Reinforced Reaction Bonded Si3N4, in Proceedings of the 15th Annual Conference on Composites and Advanced Ceramic Materials, Part 1 of 2: Ceramic Engineering and Science Proceedings, Volume 12, Issue 7/8 (ed J. B. Wachtman), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470313831.ch27
- Published Online: 28 MAR 2008
- Published Print: 1 JAN 1991
Print ISBN: 9780470375099
Online ISBN: 9780470313831
Intermediate density, high-purity RBSN made from silane-derived Si powders has a specific strength and strain-to-failure higher than fully dense Si3N4 Because the fracture toughness is comparatively low, this research sought to increase fracture resistance through composite toughening with particulate and whisker additions. The RBSN composites were made from colloidally pressed octanol dispersions of 0.2–0.3 m̈m diameter, high-purity Si powders mixed with either SiC whiskers (SiC(w)) or Acheson α-SiC particles (SiC(p)) having diameters of ∼0.5 m̈m and ∼0.2 m̈m, respectively. The effect of the reinforcements on room temperature strength, fracture toughness, and R-curve behavior, and interactions between cracks and reinforcements were studied. None of the materials exhibited R-curve behavior. While the microstructural properties of the matrix were retained and no evidence of SiC surface degradation was observed, an increase in Kc was seen only in the 33 vol% SiC(p). Details of the fracture process were revealed by SEM of surface cracks and fracture surfaces as well as TEM. Inoperative toughening mechanisms in the whisker composite were attributed to nonuniform whisker morphology. The modest increase in Kc of the 33 vol% particulate samples resulted from crack deflection around larger particles.