固—固相变储能物质—(C_nH_2n+1NH₃)₂MX₄及其二元体系的研究

【作者】 李雅娟；

【导师】 刘晓地； 武克忠；

【作者基本信息】 河北师范大学 ， 物理化学， 2003， 硕士

【摘要】 能源是人类生存和发展的基础。随着科学技术的发展，人类对能源的需求日益增加，但同时对能源的利用率仍不是很高，存在着很大的浪费，从而造成能源的供给渐趋紧张。因此，如何开发出新的能源以及提高其利用率已经成为非常紧迫的问题。考虑到选择贮能材料的原则，固-固相变材料以其转变温度低、转变焓高、过冷轻、体积变化小、无相分离等优点而倍受青睐。本论文选择了具有技术和经济潜力的固-固相变贮能材料—有机金属化合物作为研究对象，其通式为(n-C_nH_2n+1NH₃)₂MX₄，对其纯物质及其二元体系的贮热性能进行了系统的研究，为选择合适的贮能材料提供理论依据；绘制了其二元体系的相图，为实际应用提供有价值的参考；并对其进行了动力学的研究，探讨了其固-固相变的活化能与其结构的关系。 第一部分的工作是制备了一系列有机金属化合物C_nMX及其二元体系，采用元素分析和红外光谱技术对纯样进行了合成表征。然后对其结构和相变机理进行了分析，以期更深入的理解不同有机金属化合物热参数的异同。 第二部分的工作是采用差示扫描量热法（DSC）对纯样及其二元体系的贮热性能进行了详细系统的研究。结果表明，纯样及其二元体系均具有优良的贮热性能：转变焓高、不挥发、过冷程度轻、使用寿命长等优点，而且二元体系可以降低相转变温度，拓宽相变温度范围，更适用于低温贮热。 第三部分的工作是绘制了两个C_nZnCl二元体系的相图，并首次绘制了一个C_nCuBr体系相图。利用三种实验手段：（1）热分析，以得到组成和转变温度的关系。（2）X-射线衍射技术，用以确定不同组成的二元体系的相区。（3）变温红外光谱的测试，即通过红外光谱中特征吸收峰随温度的变化，得到相转变温度区间，辅助绘制相图，并可探讨其相变机理。研究表明这几个体系的相图均属于有中间化合物生成的部分互溶的较简单的相图。两组元链长的大小对其互溶度有影响，两组元结构的差异影响其相图的形式。由于两组元的结构相同，故其相图的形式相同，但由于组元的链长不同，故其互溶度有所不同。相图所提供的热力学信息对生产实践有指导意义。 第四部分的工作主要是测得不同升温速率下的CnZnCI（n二10、12、16、18）、及不同组成的CloZnCI一C16ZnCI二元体系的DSC曲线，借助儿ssinger法和ozawa法计算固一固相变过程的动力学参数一活化能 （Ea）和反应级数（n），并分析比较两种动力学处理方法和计算结果。结果表明它们的固一固相变过程均为一级反应，所得计算结果中的活化能Ea的数值有一定的规律性:前两个纯物质的活化能随链长的增加而升高，而后两个纯物质的活化能较前两个纯物质的值小，并随链长的增加而减小，这与分子间的作用力有关:对于二元体系其固一固相变过程的活化能的变化规律与其相变过程的相变焙规律一致。 所作工作是在前人基础上，从热力学和动力学更深入的研究固-固相变过程，为固一固相变储能物质的实际应用提供了理论依据，添补和修正了数据的空白和不足。采用了多种实验手段，其中变温红外研究相变是近年来较新的测试方法，对揭示相变机理有重要的作用。而变温红外辅助绘制相图是一种新的尝试，结果证实是很有效的。更多还原

【Abstract】 Energy is the base of living and development of human being. With the development of science technology, the demand of energy is increased, but because of the low utilization ratio and the waste, the supply of energy is in short supply. So, how to develop new energy and increase the utilization ratio are becoming the importance problem. Considering the principle of selecting energy storage materials, phase change materials （PCMs） have been widely studied. Particularly, the solid-solid phase materials are attached to increasing importance because of many advantages such as low temperature, high enthalpies, low supercooling degree and so on during solid-solid phase transition. They also offer many other advantages of small change in volume and no phase separation, which make them suitable for heat storage. Alkylammonium teyrachlorometallates （II） (C_nH_2n+12MCl₄ (C_nMX) and their binary system have solid-solid phase transition and can be widely used in many heat storage areas. The article is divided into four parts to study and analyze C_nMX and their binary system.In the first part, a series of C_nMX and their binary system were synthesized, element analysis and IR spectra were used to characterize them. The structure and mechanism of solid to solid transition are analyzed in order to understand the different of the thermal parameter of C_nMX deeply.In the second part, differential scanning calorimetric （DSC） method was used to study the thermodynamic properties of C_nMX and their binarysystem. The calorimetric results show that C_nMX and their binary system have good properties in heat storage such as high enthalpies, no volatility, low supercooling degree and wide range of phase transition temperatures. The results also show that C_nMX and their binary system are promising candidate materials for thermal energy storage.In the third part, the experimental phase diagrams of binary system C₁₀ZnCl/C₁₆ZnCl and C₁₀CuBr/C₁₂CuBr were established at room temperature by three techniques: DSC method, X-ray diffraction, and IR spectra at various temperature. X-ray diffraction patterns are convenient for phase analysis, because the interplanar spacing d and relative intensity I are intrinsic properties of substances, which can confirm the phase of different binary system. The infrared spectra in the range 4000-450cm^-1 were measured. In the temperature range corresponding to the solid-solid phase transition the characteristic absorption has a sudden change which can declare the mechanism of solid-solid phase transition. The results show that the phase diagrams of the above two system are similar and are partial miscibility phase diagram with a stable compound being formed. This need think about the miscible degree of two compositions. For binary system phase diagram is determined by the different of two compositions. Their size influent the degree of dissolve each other and their structure influent the form of phase diagram. Because of the same structure, the form of phase diagram is same, but because of the different of size, the degree of dissolve is different.The last part of the article chiefly dealt with the calculation of two kinetic parameters （activation energy, Ea; reaction order, n） of C_nZnCl（n=10,12,16,18） and C₁₀ZnCl/C₁₆ZnCl binary system by modeling the thermograms observed by DSC. The kinetic treatment methods-Kissinger and Ozawa were used and came to the same conclusion. The conclusion is drawn that the reaction order of their solid-solid phase transition is one and the change of Ea has a rule: with the increasing of n in C₁₀ZnCl, C₁₂ZnCl, activation energy Ea and pre-exponential factor In A were increased, but with the increasing of n in C₁₆ZnCl, C₁₈ZnCl, Ea and hi A were decreased and minor to C₁₀ZnCl, C₁₂ZnCl. In the mixture, Ea and H have the same regularity.My work was done on the basis of other people, the research of solid to solid transition was studies from thermodynamics and kinetic. The theory for the更多还原