Model experiments concerning abnormal grain growth in silicon nitride
- Autor: Dressler, W; Kleebe, HJ; Hoffmann, MJ; Ruhle, M; Petzow, G
- Quelle: JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 1996, Band 16, Heft 1, S. 3–14
- Model experiments concerning abnormal grain growth in silicon nitride.
Abstract
Model experiments were designed to study abnormal grain growth in
Si3N4-based ceramics. Experiments relating inhomogeneous crystalline
secondary-phase distribution to exaggerated grain growth conclusively
showed that abnormal grain growth is not governed by secondary-phase
distribution, because a rapid homogenization of locally formed liquid
occurs via capillary forces. Further investigations were focussed on
intrinsic properties of the alpha-Si3N4-starting powders. The influence
of: (i) beta-Si3N4-grain morphology; (ii) beta-Si3N4-nuclei density,
and (iii) beta-Si3N4-grain-size distribution of the powder blends on
microstructural development were analyzed. The results revealed that a
large basal plane of beta-Si3N4 seeds energetically and kinetically
favours grain growth. However, this effect is only partly responsible
for abnormal grain growth. The formation of elongated Si3N4 grains,
such as in in situ reinforced Si3N4 materials, strongly depend on the
amount and grain-size distribution of beta-Si3N4 nuclei present in the
alpha-Si3N4-starting powder.