在有限的液体体积条件下，异常高的结晶速率受晶体形式的控制,Crystal Growth & Design

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在有限的液体体积条件下，异常高的结晶速率受晶体形式的控制
Crystal Growth & Design ( IF 3.2 ) Pub Date : 2018-01-30 00:00:00 , DOI: 10.1021/acs.cgd.7b00980
S. Y. Misyura _{1,

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Affiliation

已经通过实验研究了在盐水溶液的薄层中的非等温蒸发和结晶。这些研究的结果对于获得薄涂层和薄层和薄膜的结晶相关的各种现代技术都是重要的。结晶模式显示为不同的盐是不同的，并且在结晶水合物表面和时间上都变化。已经检查了晶体水合物的生长动力学。结晶曲线的定性行为可能与使用统计方法获得的曲线的行为一致，也可能不同。结果表明，这种差异是由蒸发速率与结晶速率的变化比率决定的。通过改变蒸发速度，可以改变晶体形式和结晶速度。众所周知，结晶速率随时间的平方根增加。但是，根据我们的结果，结晶速度可能随时间上升和下降，并且具有极值。对于所有研究的盐结晶水合物，都有可能发现树枝状晶体。对于NaCl晶体，未发现枝晶。忽略晶体形式（“晶体习性”）可能会导致高估和低估3个数量级的结晶速率。晶体形式的形态显示出控制动力学并导致异常高的结晶速率。实验中得出的动力学常数比通过已知动力学表达式计算出的常数高三个数量级，没有考虑到“水晶习惯”。在结晶前沿的前面，有一个移动的热前沿，出现在亚稳态溶液中。考虑到热传递和晶体形式，可以定量和定性地描述结晶行为的差异。

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The Anomalously High Rate of Crystallization, Controlled by Crystal Forms under the Conditions of a Limited Liquid Volume

Non-isothermal evaporation and crystallization in a thin layer of an aqueous salt solution have been studied experimentally. The results of these studies are important for a wide range of modern technologies, associated with obtaining thin coatings and crystallization in thin layers and films. The crystallization patterns are shown to differ for different salts and change both over the crystalline hydrate surface and over time. The growth kinetics of crystal hydrates has been examined. A qualitative behavior of crystallization curves may both coincide and differ from the behavior of the curves, obtained using a statistical approach. It is shown that this difference is determined by a changing ratio of rates of evaporation to crystallization. By changing the evaporation velocity, it is possible to change the crystal forms and crystallization velocity. It is well-known that the crystallization rate increases as a square root of time. However, according to our results, the crystallization rate may both rise and fall over time and have an extremum. For all studied crystalline hydrates of salts, it was possible to find dendrites. For the NaCl crystals, the dendrites were not found. A neglect of the crystal form (“crystal habit”) may result in both overestimating and underestimating the crystallization rate by 3 orders of magnitude. The morphology of the crystal forms is shown to control the kinetics and leads to anomalously high crystallization rates. The kinetic constant derived in the experiment is three orders higher than the constant, calculated by the known kinetic expressions, which do not take into account the “crystal habit”. Ahead of the crystallization front, there is a moving thermal front, arising in a metastable solution. Consideration of heat transfer and crystal forms allows quantitatively and qualitatively describing the difference in the behavior of crystallization.

更新日期：2018-01-30

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