Solidification of a disk-shaped crystal from a weakly supercooled binary melt.
Solidification of a disk-shaped crystal from a weakly supercooled binary melt.
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弱过冷二元熔体中盘状晶体的凝固。
DOI：
10.1103/physreve.92.022406
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
A. Wells
中科院分区：
文献类型：
--
作者：
David W. Rees Jones;A. Wells
从液相中生长冰晶的物理学，特别是在有盐存在的情况下，比从气相中生长雪晶受到的关注要少得多。在过冷的盐水溶液中凝固形成的所谓冰的生长与晶体在基面上的生长是一致的，晶体生长受到固液界面上凝固潜热的扩散去除的限制，同时受到垂直方向上的附着动力学的限制。这导致形成近似圆盘状的晶体，与半径相比，厚度的纵横比较低，因为径向生长比轴向生长快得多。考虑到相对较慢的轴向生长、溶质在流体相中的溶解作用以及固相和流体相之间热性能的差异，我们用数值方法计算了圆盘状晶体在纯熔体和二元熔体中的生长速度。我们确定了控制晶体生长的主要物理机制，并表明生长界面上释放的潜热和拒绝的盐的扩散去除都是重要的。我们的计算表明，某些先前的参数化，基于尺度的论点，大大低估了低纵横比磁盘的晶体生长速率，其数量级为10-100，并且我们提供了用于环境设置中冰晶生长模型的参数化。
The physics of ice crystal growth from the liquid phase, especially in the presence of salt, has received much less attention than the growth of snow crystals from the vapor phase. The growth of so-called frazil ice by solidification of a supercooled aqueous salt solution is consistent with crystal growth in the basal plane being limited by the diffusive removal of the latent heat of solidification from the solid-liquid interface, while being limited by attachment kinetics in the perpendicular direction. This leads to the formation of approximately disk-shaped crystals with a low aspect ratio of thickness compared to radius, because radial growth is much faster than axial growth. We calculate numerically how fast disk-shaped crystals grow in both pure and binary melts, accounting for the comparatively slow axial growth, the effect of dissolved solute in the fluid phase, and the difference in thermal properties between solid and fluid phases. We identify the main physical mechanisms that control crystal growth and show that the diffusive removal of both the latent heat released and the salt rejected at the growing interface are significant. Our calculations demonstrate that certain previous parametrizations, based on scaling arguments, substantially underestimate crystal growth rates by a factor of order 10-100 for low aspect ratio disks, and we provide a parametrization for use in models of ice crystal growth in environmental settings.