Liquid-Phase Sintered SiC Ceramics with Oxynitride Additives

  • Rixecker, G. (Max-Planck Institut f r Metallforschung and Institut fr Nichtmetallische Anorganische Materialien der Universit t Stuttgart) ;
  • Biswas, K. (Max-Planck Institut f r Metallforschung and Institut fr Nichtmetallische Anorganische Materialien der Universit t Stuttgart) ;
  • Wiedmann, I. (Max-Planck Institut f r Metallforschung and Institut f r Nichtmetallische Anorganische Materialien der Universit t Stuttgart) ;
  • Sldinger, F. (Max-Planck Institut f r Metallforschung and Institut f r Nichtmetallische Anorganische Materialien der Universit t Stuttgart)
  • Published : 2000.06.01

Abstract

Silicon carbide ceramics with sintering additives from the system AlN-Y$_2$O$_3$ can be gas-pressure sintered to theoretical density. While commonly a combination of sesquioxides is used such as Al$_2$O$_3$-Y$_2$O$_3$, the oxynitrid additives offer the advantage that only a nitrogen atmosphere is require instead of a powder. By starting form a mixture of ${\beta}$-SiC and ${\alpha}$-SiC, and by performing dedicated heat treatments after densification, anisotropic grain growth is obtained which leads to a platelet microstructure showing enhance fracture toughness. In the present work, recent improvement of the mechanical behaviour of these materials at ambient and high temperatures is reported. By means of a surface oxidation treatment in air it is possible to obtain four-point bending strengths in excess of 1 GPa, and the strength retention at high temperatures is significantly improved.

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