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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Fast and slow components in the crystallization of a model multicomponent system, NaKCa(NO_3): The role of composition fluctuations
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Fast and slow components in the crystallization of a model multicomponent system, NaKCa(NO_3): The role of composition fluctuations

机译：模型多组分系统NaKCa（NO_3）结晶中的快和慢组分：组分波动的作用

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摘要

We use calorimetrically detected crystal nucleation and growth studies to broaden the discussion of fluctuation-induced nucleation processes to include composition fluctuations in ionic complex-forming systems. We use the model system Ca-(NO_3)_2-KNO_3 with NaNO_3 introduced as a third component, so that crystallization kinetics can be controlled by change of alkali cation at constant mole fraction of Ca(NO _3)_2. At fixed NaNO_3 content, we find separate and thermodynamically anomalous kinetics for the crystallization of NaNO _3 and Ca(NO_3)_2,which we attribute to the importance of slow concentration fluctuations in the latter case. The "nose" of the time-temperature- transformation TTT curve for crystallization of the Ca(NO_3)_2 occurs at much higher temperatures and longer times than that for NaNO_3 and the shape of the curve is different. Above the metastable liquidus surface of NaNO _3, supercooled ternary melts can persist for long times. Suppression of the fast NaNO_3 crystallization, by replacement of Na~+ by K~+, is a prerequisite for easy vitrification in this system.
机译：我们使用量热法检测晶体成核和生长研究，以扩大对波动诱导的成核过程的讨论，以包括离子络合物形成系统中的成分波动。我们使用引入NaNO_3作为第三组分的模型系统Ca-（NO_3）_2-KNO_3，以便可以通过在Ca（NO _3）_2的摩尔分数恒定时改变碱金属阳离子来控制结晶动力学。在固定的NaNO_3含量下，我们发现NaNO _3和Ca（NO_3）_2的结晶具有独立的热力学异常动力学，这归因于在后一种情况下缓慢的浓度波动的重要性。用于Ca（NO_3）_2结晶的时间-温度-转变TTT曲线的“鼻子”出现在比NaNO_3更高的温度和更长的时间下，并且曲线的形状不同。在NaNO _3的亚稳态液相线表面上方，过冷的三元熔体可以持续很长时间。通过用K〜+代替Na〜+来抑制快速的NaNO_3结晶是该系统中易于玻璃化的先决条件。

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