Theoretical Analysis of Classical DTA, Power-Compensated DSC and Heat-Flux DSC

Kazuya SAITO, Tooru ATAKE and Yasutoshi SAITO

Theoretical analysis is given for classical DTA (differential thermal analysis), power-compensated DSC (differential scanning calorimetry) and heat-flux DSC, based on a unified model which is applicable to all the three types of instruments. The equation governing heat flow within the system are solved analytically assuming constant heat capacity and thermal conductivity. The method of estimating the actual temperature is given in the case of the first-order phase transition. A principle of drawing the base line is given for determining the enthalpy of the first-order phase transition. Applying the principle to the unified model, theoretically rigorous drawing of the base line is shown in the case that the heat capacities before and after the transition are different. Theoretical peak height due to the first-order phase transition is represented as a function of the heat capacity, the thermal resistance and the heating (cooling) rate. It is shown that the limiting peak height obtainable in the experiments is independent of the amount of the sample. A possibility is discussed of quantitative determination of the enthalpy of transition by using classical DTA.
(Netsu Sokutei, 14, 2-11 (1987), review in Japanese)


Theoretical Analysis of Peak Height in Classical DTA, Power-Compensated DSC and Heat-Flux DSC

Yasutoshi SAITO, Kazuya SAITO and Tooru ATAKE

Theoretical analysis of peak height is given for traces, due to a first-order phase transition with substantial latent heat, obtained classical DTA, power-compensated DSC and heat-flux DSC. Theoretical peak height is represented as a function of the heat capacity, the thermal resistance and the heating (cooling) rate on the basis of a unified model which is applicable to all three types of instruments. The limiting height obtained in the experiment with an infinite rate of heating (cooling) is independent of the amount of the sample present. The possibility is discussed of quantitative determination of the enthalpy of transition by using classical DTA.
(Thermochim. Acta, 107, 277-282 (1986))


Base Line Drawing for the Determination of the Enthalpy of Transition in Classical DTA, Power-Compensated DSC and Heat-Flux DSC

Yasutoshi SAITO, Kazuya SAITO and Tooru ATAKE

A principle for drawing the base line is given when determining the enthalpy of the first-order phase transition by experiments with classical differential thermal analysis, power-compensated differential scanning calorimetry and heat-flux differential scanning calorimetry. When the principle is applied to Mraw's model which is applicable to the three tyoes of instruments, theoretically rigorous drawing of the base line is shown in the case when the heat capacity of the sample before and after transition is different. The enthalpy of transition is obtained from the area enclosed by the base line and the recorded trace.
(Thermochim. Acta, 104, 275-283 (1986))


Theoretical Analysis of Heat-Flux Differential Scanning Calorimetry Based on a General Model

Yasutoshi SAITO, Kazuya SAITO and Tooru ATAKE

Theoretical analysis is given for heat-flux differential scanning calorimetry, based on a unified model which is applicable also to classical differential thermal analysis and power-compensated differential scanning calorimetry. The equations governing heat flow within the system are solved analytically on the assumption that the values of heat capacity and of thermal conductivity are constant. The temperature-lag of the sample is evaluated, and the method of estimating the actual temperature is given in the case of the first-order phase transition.
(Thermochim. Acta, 99, 299-307 (1986))


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