Kinetics of heterogeneous nucleation and the 'memory effect' in liquid gallium

Abstract

A series of experiments on liquid gallium is briefly reviewed. A new approach to the behaviour of liquid gallium during the crystallization is explained and a model of kinetics of heterogeneous nucleation is presented. The experimental results obtained by use of the simple thermal analysis have fully confirmed this model.

Dependence of supercooling of a liquid on its overheating

“…Based on the assumption of the existence of microcavities either on the container or on the surface of impurity particles inside a melt, a theoretical linear relationship between the degree of melt supercooling (⌬T Ϫ ) and the level of melt overheating (⌬T ϩ ) was predicted. [5][6][7] While previous experimental results obtained on gallium 5,7 and bismuth 6 were consistent with this theoretical linear relationship, no dependence was observed for bismuth, 8 CdTe, 1 and PbTe. [2][3][4] On the other hand, those previous experimental results were obtained without cooling rate control which can significantly affect the degree of supercooling.…”

Dependence of Liquid Supercooling on Liquid Overheating Levels of Al Small Particles

“…The thermal history effect can be quantified by the relationship between liquid overheating (Δ T + ), which is measured by the difference between liquid temperature and the equilibrium melting point ( T 0 ), and liquid supercooling (Δ T − ), which is measured by the difference between T 0 and the temperature of solidification. Thus far, the dependence of Δ T − on Δ T + has been investigated in metals/semimetals (Bi, Sn, Ga) [2,3,4,5,11,14] and alloys [6,7,8,9,10,11]; typically Δ T − increases with an increase of Δ T + up to several to tens of degrees above T 0 . Despite the fundamental and technical importance, the underlying mechanism of this phenomenon in relation to the liquid structure and the kinetics of heterogeneous nucleation of solidification is not well understood.…”

“…The cavity theory has been quantitatively validated by various experimental results [2,3,4,5], but it was considered to be not general, e.g., the dependence of Δ T − on Δ T + in Bi, Sn, SnSb and SnPb was found to be either continuous or discontinuous [10,11], which points to the evolution of transient short range order structures in the liquid state. Obviously, more investigations of the Δ T + -Δ T − relationship (thermal history effect) in metals and alloys are needed.…”

“…Solidification and melting are transformations basic to technological applications such as casting, crystal growth, and glass formation. Historically, the liquid thermal history was discovered to have a significant effect on the liquid supercooling behavior and thus, the nucleation and growth of crystals and their qualities [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ]. The thermal history effect can be quantified by the relationship between liquid overheating (Δ T + ), which is measured by the difference between liquid temperature and the equilibrium melting point ( T 0 ), and liquid supercooling (Δ T − ), which is measured by the difference between T 0 and the temperature of solidification.…”