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[求助]
相?分离之 失 稳分解 已有1人参与
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最近在做分相研究，制备的材料形貌出现这种链式结构夹杂成核小点，觉得不像是传统的成核生长分相过程。 有木有做相?分离的虫友，求教如何论证分析这个现象。  发自小木虫Android客户端 |
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- 【资源】微观组织热力学
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2楼2016-07-10 23:19:09
3楼2016-08-17 03:37:05
4楼2016-08-18 16:28:35
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无机的二氧化硅复合材料，溶胶液室温干燥后就形成了这个样子，没有啥后处理。这个没有相图。做了xps,eds发现凸起部分和其他部分的化学组成有差异。不知道这样是否可以确定是失稳分解了？谢谢了！ 发自小木虫Android客户端 |
5楼2016-08-18 17:05:10
【答案】应助回帖
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冰点降温: 金币+1, 谢谢回帖交流，欢迎常来无机物化版块。 2016-08-20 09:45:52
lipp6699(冰点降温代发): 金币+2 2016-08-20 09:46:00
冰点降温: 金币+1, 谢谢回帖交流，欢迎常来无机物化版块。 2016-08-20 09:45:52
lipp6699(冰点降温代发): 金币+2 2016-08-20 09:46:00
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我们研究领域差得有点大（忽然发现闯到化工区了），试着提供些信息，希望能有帮助。之所以讲是spinodal decomposition，是因为看上去跟典型的spinodal decomposition（见下图, T为时间）太像了。  spinodal decomposition是什么东西？ Spinodal decomposition is a mechanism for the rapid unmixing of a mixture of liquids or solids from one thermodynamic phase, to form two coexisting phases. As an example, consider a hot mixture of water and an oil. At high temperatures the oil and the water may mix to form a single thermodynamic phase in which water molecules are surrounded by oil molecules and vice versa. The mixture is then suddenly cooled to a temperature at which thermodynamic equilibrium favours an oil-rich phase coexisting with a water-rich phase. Spinodal decomposition then occurs when the mixture is such that there is essentially no barrier to nucleation of the new oil-rich and water-rich phases. In other words, the oil and water molecules immediately start to cluster together into microscopic water-rich and oil-rich clusters throughout the liquid. These clusters then rapidly grow and coalesce until there is a single macroscopic oil-rich cluster, the oil-rich phase, and a single water-rich cluster, the water-rich phase. Spinodal decomposition can be contrasted with nucleation and growth. There the initial formation of the microscopic clusters involves a large free energy barrier, and so can be very slow, and may occur as little as once in the initial phase, not throughout the phase, as happens in spinodal decomposition. 精准判断是不是spinodal decomposition需要结合相图和吉布斯自由能作出spinodal curve（见下图）。 In thermodynamics, the limit of local stability with respect to small fluctuations is clearly defined by the condition that the second derivative of Gibbs free energy is zero. The locus of these points (the inflection point within a G-x or G-c curve, Gibbs free energy as a function of composition) is known as the spinodal curve. For compositions within this curve, infinitesimally small fluctuations in composition and density will lead to phase separation via spinodal decomposition. |
6楼2016-08-19 19:38:17
7楼2016-08-22 00:22:39