Chapter 23. Fracture Toughness and Reliability of Si3N4 Whisker-Reinforced Si3N4 Ceramics

  1. J. P. Singh
  1. Célio A. Costa and
  2. Judith A. Todd

Published Online: 26 MAR 2008

DOI: 10.1002/9780470294437.ch23

Proceedings of the 21st Annual Conference on Composites, Advanced Ceramics, Materials, and Structures: A: Ceramic Engineering and Science Proceedings, Volume 18, Issue 3

Proceedings of the 21st Annual Conference on Composites, Advanced Ceramics, Materials, and Structures: A: Ceramic Engineering and Science Proceedings, Volume 18, Issue 3

How to Cite

Costa, C. A. and Todd, J. A. (1997) Fracture Toughness and Reliability of Si3N4 Whisker-Reinforced Si3N4 Ceramics, in Proceedings of the 21st Annual Conference on Composites, Advanced Ceramics, Materials, and Structures: A: Ceramic Engineering and Science Proceedings, Volume 18, Issue 3 (ed J. P. Singh), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470294437.ch23

Author Information

  1. Department of Mechanical, Materials and Aerospace Engineering, Illinois Institute of Technology, Chicago, IL 60616, USA

Publication History

  1. Published Online: 26 MAR 2008
  2. Published Print: 1 JAN 1997

ISBN Information

Print ISBN: 9780470375495

Online ISBN: 9780470294437

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Keywords:

  • ceramics;
  • hot-pressed direction;
  • grain size;
  • sintering aid;
  • weibull modulus

Summary

Addition of 5 and 10 wt.% Si3N4 whiskers to Si3N4 hot-pressed with 3% MgO resulted in an increase of toughness perpendicular to the hot-pressed direction of 25% (8.8 MPa.m1/2) and 14% (8.0 MPa.m1/2), respectively, compared to the monolithic material (7.0 MPa.m1/2). However, the same whisker additions to Si3N4 hot-pressed with 6% Y2O3 sintering aid, decreased the toughness of the composite by 18% (6.7 MPa.m1/2) and 10% (7.4 MPa.m1/2), respectively, compared to the monolithic material (8.2 MPa.m1/2). Despite the above differences in toughness, a Weibull modulus of 12 was found for all materials, irrespective of the amount of whiskers and type of sintering aids. Grain size variation did not uniquely explain the above differences in fracture toughness. A crack deflection mechanism predominated and could be correlated with the low value of Weibull modulus.