先进材料疑固实验室 Morphology control of crystals Laboratory of Advanced Materials Solidification What is the mechanisms of the effect of heat flow on crystal growth? After nucleation,normally AT;is fairly large,and this causes high growth rate and rapid heat release. If the (negative)temperature gradient in the solid or the liquid is not sufficiently large,the heat cannot be transferred away quickly enough, and the residual heat is used to heat the solid and liquid near the S/L interface. This will cause an increase of Ti,and a decrease of ATi,which in turn leads to a decrease of growth rate and the rate of heat release from solidification. At some point,these two opposite effects are balanced,and ATi remains unchanged.This is called steady state for crystal growth. T;and AT;are the temperature and undercooling at the interface 上海充通大￥ SHANGHAI JIAO TONG UNIVERSITYMorphology control of crystals What is the mechanisms of the effect of heat flow on crystal growth? • After nucleation, normally ∆Ti is fairly large, and this causes high growth rate and rapid heat release. • If the (negative) temperature gradient in the solid or the liquid is not sufficiently large, the heat cannot be transferred away quickly enough, and the residual heat is used to heat the solid and liquid near the S/L interface. • This will cause an increase of Ti , and a decrease of ∆Ti , which in turn leads to a decrease of growth rate and the rate of heat release from solidification. • At some point, these two opposite effects are balanced, and ∆Ti remains unchanged. This is called steady state for crystal growth. Ti and ∆Ti are the temperature and undercooling at the interface