Concurrent differential thermal and amperometric thermal analysis

Abstract

The evolution or absorption of energy in the form of heat that accompanies a transition of a material as a function of temperature has provided the basis for differential thermal analysis. The observation and/or measurement of the changes of other properties of materials can be used also to detect and measure transitions. One such example of this is change in the thermal coefficient of electrical resistance of a material. A sample holder has been designed which permits amperometric thermal analysis (ATA) and differential thermal analysis (DTA) to be performed concurrently over the temperature range from ambient to 500°C. The DTA portion is performed in the conventional way and the ATA is carried out by measuring the current flow within the sample as a function of temperature. Using ATA, currents as small as 1 × 10 −12 can be measured. The thermal analyses of many materials using the concurrent techniques show that the two methods reinforce one another and in some instances ATA is capable of detecting physical changes that are not as readily observable by DTA due to a lack of sensitivity or underlying principle. The thermograms in the following paper illustrate the utility of ATA in detecting the presence of moisture, glass transitions, crystallization, melting, and oxidation. In principle, the thermal coefficient of resistance can be dynamically obtained.