Modeling and simulation of grain growth in Si3N4. III. Tip shape evolution

Simulations based on the anisotropic Ostwald ripening model have been perfo rmed for the tip shape evolution of the beta -Si3N4 crystal in the liquid p hase. it was found that tip shape is a function of the liquid concentration and the relationship between the interfacial reaction and diffusion consta nts. Depending on the concentration of the liquid phase, a convex, almost f lat, or concave surface appeared at the tip surface. The following two fact ors are crucial for understanding the development of concavity at the tip s urface of the beta -Si3N4 crystal: (1) young growth anisotropy of the beta -Si3N4 crystal that is the interfacial reaction and diffusion controlled ki netics of the (100) and (001) surfaces, respectively, and (2) supersaturati on of the liquid phase. (C) 2000 Acta Metallurgica Inc. Published by Elsevi er Science Ltd. All rights reserved.