IAM - Ceramic Materials and Technologies

Thermodynamic analysis of grain aspect ratio in fibrous microstructures of silicon nitride

  • Author:

    Raj, R.; Hoffmann, M. J.

  • Source:

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY 80 (1997), 12, 3250–3252 

  • Thermodynamic analysis of grain aspect ratio in fibrous microstructures of silicon nitride.

Abstract

Needlelike, free-floating beta-crystals of silicon nitride, precipitated within a supersaturated Y-Si-Al-O-N oxynitride glass, apparently approach an equilibrium value of the aspect ratio. An expression that relates this aspect ratio to the anisotropy in the interfacial energies of the longitudinal and transverse interfaces of the crystal is derived. The prediction agrees reasonably well with theoretical estimates of the interfacial energies. Kinetic and stearic effects that often lead to nonequilibrium values of the aspect ratio are discussed.