Development of measuring apparatus for thermophysical properties in a very small qyuantity of substances by means of ac calorimetric method

为了测量少量物质的热物性，研制了一种光照射式交流热量计，其目的之一就是测量少量液体的热容。样品池由一根内径130微米、外径17微米、长39毫米的超细不锈钢管制成，内装液体样品0.52微米。为了得到热容的绝对值，需要评估空室的热容和提供给电池的交流热流的幅度。为此，计算了空电池、装满标准液体的电池和装满液体样品的电池的交流温度幅度。由此可以得到液体样品的单位体积热容。在此测量中，液体样品的热容绝对值的测定精度在1%以内。用该方法测定了磷脂在水相悬浮液中的热容。热容量在二棕榈酰磷脂酰胆碱(DPPC)-胆固醇与胆固醇，浓度高达7摩尔%。测量了DPPC-二肉豆蔻基磷脂酰胆碱(DMPC)混合物的热容，特别注意了在纯DPPC中出现而在纯DMPC中不出现的亚稳态出现的条件。结果表明，当DMPC的浓度超过50mol%时，不再出现亚稳态，测量热扩散率或导热系数可用于了解少量材料的热物理性质。光照射型交流量热仪不仅可用于测量薄膜的热扩散率，还可用于测量细丝的热扩散率。

A light-irradiation-type ac calorimeter has been developed for obtaining thermophysical properties in a small quantity of materials.One of the aims in the present study is to measure the heat capacity of a small quantity of liquid. The sample cell is made of a very fine stainless steel tube, for instance, 130mum in inside diameter, 17Omum in outside diameter and 39mm long, which is filled with 0.52mul of a liquid sample. To obtain the absolute value of the heat capacity, evaluation of the heat capacity of the empty cell and the amplitude of ac heat flux supplied to the cell is necessary. For this purpose, the amplitude of ac temperature of the empty cell, the cell filled with a standard liquid and the cell filled with a liquid sample. From them, the heat capacity per unit volume of the liquid sample is obtained. In this measurement, the absolute value of heat capacity in liquid sample is determined within an accuracy of 1%. Using this method, the heat capacity of phospholipids in aqueous suspension was measured. The heat capacity in dipalmitoylphosphatidylcboline (DPPC)-cholesterol with cholesterol, concentrations up to 7 mol%. The heat capacity in DPPC-dimyristoylphosphatidylicholine (DMPC) mixtures was measured with special attention to the condition for the appearance of metastable state, which appears in pure DPPC and does not appear in pure DMPC. It was found that the metastable state no longer appears at the DMPC concentrations more than 50 mol%.The measurement of thermal diffusivity or thermal conductivity is desirable to know the thermophysical properties of a small quantity of materials. A light-irradiation-type ac calorimetry was also applied to the measurement of thermal diffusivity in not only thin films but also fine wires.