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Journal of Materials Science

, Volume 11, Issue 5, pp 908–912 | Cite as

Effect of selected impurities on the high temperature mechanical properties of hot-pressed silicon nitride

  • J. L. Iskoe
  • F. F. Lange
  • E. S. Diaz
Papers

Abstract

The effect of impurities on the high temperature mechanical properties of hot-pressed silicon nitride has been determined. Selected impurity additions were made to both relatively pure α-phase and Β-phase silicon nitride starting powders. These powders were hot-pressed to full density using 5 wt % MgO as the pressive additive. The silicon nitride hot-pressed from the α-phase powder exhibited higher strength at both 25 and 1400‡ C than that fabricated from the Β-phase powder. The impurity additions had no effect on the room temperature mechanical properties. The CaO additions had the most significant effect on the high temperature mechanical properties. In both the material hot-pressed from the α-phase and Β-phase powders, increasing CaO additions severely reduced the high temperature strength and increased the amount of non-elastic deformation observed prior to fracture. Although alkali additions (Na2CO3, Li2CO3, K2CO3) also tended to have the same effects as the CaO, the high volatility of these compounds resulted in a much reduced concentration in the hot-pressed material, thus minimizing somewhat their tendency to enhance the high temperature strength degradation. The Fe2O3 and Al2O3 had no apparent effect on the high temperature mechanical properties.

Keywords

Al2O3 Fe2O3 Nitride Volatility K2CO3 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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References

  1. 1.
    R. F. Coe, R. J. Lumby and M. F. Pawson, “Special Ceramics”, Vol. 5, edited by P. Popper (Brit. Ceram. Research Assoc., 1972) p. 361.Google Scholar
  2. 2.
    D. W. Richerson, Bul. Amer. Ceram. Soc. 52 (1973) 560.Google Scholar
  3. 3.
    Fourth Semi-Annual Report, Advanced Research Projects Agency, Contract DAAG 46-71-C-0162, September 1973.Google Scholar
  4. 4.
    F. F. Lange, J. Amer. Ceram. Soc. 57 (1974) 84.Google Scholar
  5. 5.
    S. Wild, P. Grieveson, K. H. Jack and M. J. Latimer, “Special Ceramics”, Vol. 5, edited by P. Popper (Brit. Ceram. Research Assoc., 1972) p. 377.Google Scholar
  6. 6.
    G. R. Terwilliger and F. F. Lange, J. Amer. Ceram. Soc. 57 (1974) 25.Google Scholar
  7. 7.
    R. Kossowsky, J. Mater. Sci. 8 (1973) 518.Google Scholar
  8. 8.
    F. F. Lange, J. Amer. Ceram. Soc. 56 (1973) 518.Google Scholar
  9. 9.
    R. F. Coe, Brit. Pat. 1,092,637 (1967).Google Scholar

Copyright information

© Chapman and Hall 1976

Authors and Affiliations

  • J. L. Iskoe
    • 1
  • F. F. Lange
    • 1
  • E. S. Diaz
    • 1
  1. 1.Westinghouse Research LaboratoriesPittsburghUSA

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