Thermal analysis of repetitive single crystallization events in glass-forming liquids at low undercooling
Thermal analysis of repetitive single crystallization events in glass-forming liquids at low undercooling
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DOI：
10.1016/j.jnoncrysol.2017.12.037
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发表时间：
2017-12
影响因子：
3.5
通讯作者：
S. Krüger;J. Deubener
中科院分区：
文献类型：
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作者：
S. Krüger;J. Deubener
对284个重复单结晶事件进行了热分析。特别是，泊松分布和非高斯形放热DSC信号的等温液晶转变动力学分别计算和叠加计算。发现各向异性生长、随机和规则色散的碰撞模式不能准确地预测单晶或少量晶体生长时的生长指数。当多个晶化事件的虚信号叠加时，低晶和大晶的非平稳效应明显减弱。结果表明，计算转变程度的精确解析公式依赖于同时生长的晶体系综。如果不是这种情况，如玻璃形成液体从高于液相温度冷却，正确的方法是使用重复结晶运行的时间平均信号。
Thermal analyses of 284 repetitive single crystallization events were carried out. In particular, the isothermal liquid-to-crystal transformation kinetics of Poisson-distributed and non-Gaussian shaped exothermic DSC signals are calculated individually and by superimposition. It is found that modes of impingement for anisotropic growth, random and regular dispersions fail to accurately predict the growth exponent if a single crystal or a low number of crystals are growing. Non-stationary effects are evident at low and large crystal fractions which diminish when virtual signals of multiple crystallization events are superimposed. The results show that the precise analytic formulation to calculate the degree of transformation relies on an ensemble of crystals growing simultaneously. Where this is not the case, as in glass-forming liquids cooled from above liquidus temperature, the proper approach is to use a time-averaged signal of repetitive crystallization runs.