Effect of geometrical confinement on the nucleation and crystallization behavior of n-alkane mixtures.
Effect of geometrical confinement on the nucleation and crystallization behavior of n-alkane mixtures.
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DOI：
10.1021/jp807347d
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发表时间：
2008-12
期刊：
影响因子：
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通讯作者：
K. Jiang;Yunlan Su;Baoquan Xie;Shichun Jiang;Ying Zhao;Dujing Wang
中科院分区：
文献类型：
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作者：
K. Jiang;Yunlan Su;Baoquan Xie;Shichun Jiang;Ying Zhao;Dujing Wang
受限几何中正构烷烃（正构烷烃）混合物的凝聚结构是一个有趣的话题，涉及奇数烷烃和偶数烷烃结晶行为的差异。在本工作中，结合差示扫描量热法（DSC）和X射线衍射（XRD）研究了正十八烷（n-C18H38）和正十九烷（n-C19H40）混合物在窄尺寸分布微胶囊中的结晶。 DSC检测微胶囊化的n-C18H38、n-C19H40及其混合物的表面冷冻单层，混合物为混合均匀晶相，组成连续变化。微胶囊化的 n-C18H38/n-C19H40 = 95/5（摩尔比）混合物观察到更稳定的旋转相 (RI)，与本体混合物相比，通过从 RI 到稳定相转变的过冷度增加证实了这一点。推测两种成核机制为“液-固”异质成核和“固-固”均质成核，它们发生在微胶囊的不同结晶阶段，可能分别归因于受限几何形状中的表面效应和限域效应。
The condensed structure of normal alkane (n-alkane) mixtures in confined geometry is an interesting topic concerning the difference in crystallization behavior of odd and even alkanes. In the present work, the crystallization of mixtures of normal octadecane (n-C18H38) and normal nonadecane (n-C19H40) in microcapsules with narrow size distribution was investigated using the combination of differential scanning calorimetry (DSC) and X-ray diffraction (XRD). A surface freezing monolayer for microencapsulated n-C18H38, n-C19H40, and their mixture was detected by DSC, which for the mixture is a mixed homogeneous crystalline phase with continuous change in the composition. A more stable rotator phase (RI) was observed for the microencapsulated n-C18H38/n-C19H40 = 95/5 (molar ratio) mixture, confirmed by an increased supercooling of the transition from RI to stable phase compared to that of the mixture in bulk. Two nucleation mechanisms were speculated as "liquid-to-solid" heterogeneous nucleation and "solid-to-solid" homogeneous nucleation, which occur at different crystallization stages in microcapsules and might be attributed to the surface effect and confinement effect, respectively, in the confined geometry.