Application of Grain Growth Control to Ceramic Materials
세라믹재료에서 입자성장 제어의 응용
|
문경석 경상대학교 Microstructural control during sintering is one of the most important technique of improving the properties of inorganic materials. When a polycrystal is in chemical equilibrium, the microstructure changes as results of grain growth and densification under the capillary driving force due to the interface curvature among grains. The grain growth rate is expressed as the product of the interface mobility and the driving force. According to grain growth theories, the mobility of the interface governed by diffusion control is constant but interface mobility is nonlinear when the movement of an interface governed by interface reaction. As the growth rate is nonlinear for the regime of interface reaction control, the grain growth is nonstationary with annealing time. In addition, the slower process is dominant in the overall kinetics because the atomic movement process is a series process with interface reaction and diffusion (mixed control). The microstructure can be controlled by changing the growth rate of an individual grain with correlation between maximum driving force (for the largest grain) and the critical driving force for appreciable growth. This presentation shows applications of the principle in fabrication of ceramic materials such as particle shape control of soft magnetic hexaferrite materials and solid-state single crystals growth of lead-free piezoelectric materials. |