Experimental Determination of the Crystallization Phase-Boundary Velocity in the Halozeotype CZX-1
Experimental Determination of the Crystallization Phase-Boundary Velocity in the Halozeotype CZX-1
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DOI：
10.1021/cm402745e
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发表时间：
2013-10-22
影响因子：
8.6
通讯作者：
Martin, James D.
中科院分区：
文献类型：
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作者：
Dill, Eric D.;Josey, Amanda A.;Martin, James D.
采用二维温度和时间分辨同步辐射X射线衍射仪(TtXRD)和差示扫描量热仪(DSC)对卤代分子筛CZX-1进行了等温结晶实验。这些结晶实验表明，通过在KJMA速率表达式中引入样品体积，可以从相边界控制反应的Kolmogorov Johnson和Mehl and Avrami(KJMA)模型中恢复材料的基本性质，即结晶前沿相边界的速度v(PB)。如果结晶测量的样品体积是各向异性的，则需要额外的修正项。熔体的消失和晶相的出现表明在结晶过程中不存在中间体。当玻璃化转变(T-g接近30摄氏度)接近时，相边界的速度接近于0，并且在熔点以下约10度(T-m=173摄氏度)。相界面速度在135℃时达到最大值30微米S(-1)。在v(PB)远大于形核速率的条件下生长单晶。
Isothermal crystallization experiments were performed on the halozeotype CZX-1 with 2D temperature- and time-resolved synchrotron X-ray diffraction (TtXRD) and differential scanning calorimetry (DSC). These crystallization experiments demonstrate that the fundamental materials property, the velocity of the phase boundary of the crystallization front, v(pb), can be recovered from the Kolmogorov Johnson and Mehl and Avrami (KJMA) model of phase-boundary controlled reactions by introducing the sample volume into the KJMA rate expression. An additional corrective term is required if the sample volume of the crystallization measurement is anisotropic. The concurrent disappearance of the melt and appearance of the crystalline phase demonstrate that no intermediates exist in the crystallization pathway. The velocity of the phase boundary approaches 0 as the glass transition (T-g approximate to 30 degrees C) is approached and at about 10 degrees below melting point (T-m = 173 degrees C). The velocity of the phase boundary reaches a maximum of 30 mu m s(-1) at 135 degrees C. Single crystals are grown under conditions where the v(pb) is much greater than the rate of nucleation.