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Heat Capacity at Constant Volume and Molecular Motion of Crystal, Orientationally Disordered Crystal and Liquid

晶体、无序晶体和液体的定体积热容和分子运动

基本信息

批准号：
02453008
负责人：
OGUNI Masaharu
金额：
$ 4.61万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1991
项目状态：
已结题

项目摘要

The present research aimed at making progress in the thermodynamic understanding on the coupling effects between orientational degrees of freedom and between them and the other degrees of freedom in orientationally disordered crystals.1) Effort was made to construct an automatic high-pressure calorimeter which measures simultaneously both heat capacity and volume at constant pressure to allow one to derive heat capacity at constant volume later from. The calorimeter is workable in the temperature range of 13 K to 500 K and enables high-precision thermometry of 10^<-5> K and heat capacity measurement with inaccuracy around 1 % at high pressures. We have so far succeeded in maintaining high pressure up to 200 MPa with its imprecision of 1 kPa within the high-pressure system. The remaining problem to be solved is in preparation of a thin sample-ampoule of indium which separates the sample and high pressure medium within the calorimeter cell.2) Orientationally disordered crystals, 2-haloge … More nothiophenes and pyridinium salts, were studied through heat capacity measurements under atmosphere. In the former crystals, glass transitions of one step and of two steps were observed in 2-bromothiophene and 2-chlorothiophene, respectively, and their properties changed continuously with a variation of composition between the two substances. These indicate that two reorientational processes couple with each other in both the dynamic and thermodynamic properties. In the latter cystals, pyridium iodide exhibited one phase transition while the chloride two phase transitions leading to the same high-temperature states in their orientational degrees of freedom. In pyridinium hexafluorophosphate, orientational disorderings of the cation and anion proceeded under strong coupling with each other showing only one phase transition as in the iodide. These suggest that the coupling effects stated above play quite important role in the evolution of orientational disordering both in the static and dynamic aspects. Less

本研究的目的是在取向无序晶体中取向自由度之间以及它们与其他自由度之间的耦合效应的热力学理解方面取得进展。1）努力构建了一个自动高压量热计，该量热计可以同时测量定压下的热容和体积，以便稍后可以从定压下的热容导出定体积下的热容。量热计可在13 K至500 K的温度范围内工作，并可实现10^ K的高精度测温<-5>和在高压下误差约为1%的热容测量。到目前为止，我们已经成功地在高压系统中保持了高达200 MPa的高压，其不精确度为1 kPa。剩下的问题是制备一个薄的铟样品- ...更多信息噻吩和吡啶盐，通过在大气下的热容测量进行了研究。在前一种晶体中，观察到2-溴噻吩和2-氯噻吩的玻璃化转变的一个步骤和两个步骤，分别，和它们的性质连续变化的组成之间的两种物质的变化。这表明两个取向过程在动力学和热力学性质上都是相互耦合的。在后者cystals，碘化吡啶表现出一个相变，而氯化物两个相变导致相同的高温状态在其取向自由度。在吡啶六氟磷酸盐，取向无序的阳离子和阴离子进行强耦合下，彼此只显示一个在碘化物的相变。这表明，上述耦合效应在取向无序的静态和动态演化过程中起着重要作用。少