| 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) (CnH2n+12MCl4 (CnMX) 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 CnMX and their binary system.In the first part, a series of CnMX 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 CnMX deeply.In the second part, differential scanning calorimetric (DSC) method was used to study the thermodynamic properties of CnMX and their binarysystem. The calorimetric results show that CnMX 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 CnMX 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 CnZnCl(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... |
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