A STUDY OF THE THERMAL EFFECTS OBSERVED IN DTA .3. THE INFLUENCE OF A HOLDER AROUND THE SAMPLE AND REFERENCE MATERIALS ON A TYPICAL DTA CURVE

In this study the thermal effects are reported when the sample and reference materials are held within separate "holders", each heated so that the periphery of each rises at the given rate of heating. The effect of different holder thermal conductivities, of different holder densities and specific heats, of holder radius, of different heating rates, and of differing heats of reaction are all considered, as is the effect on a typical DTA curve of varying sample properties in a holder with constant physical properties. The results suggest that the area of the DTA curve, when the thermocouples are situated between the sample and holder interface, are independent of the sample conductivity but the curve is distorted in shape compared with that drawn using the sample and reference thermocouples placed in the centre of the samples. If these latter thermocouples are used for area measurement then the results vary with sample conductivity. It is apparent that the centre measuring thermocouple system is suitable for qualitative work while a holder-sample interface thermocouple system is best suited for quantitative work.