Advanced applications of DTA

Sects. 4.2-4A. Intermediate between thermometry and calorimetry is differential thermal analysis, or DTA. In this technique transition temperature information is derived by the qualitative changes in heats of transition or heat capacity. As the instrumentation of DTA advanced, quantitative heat information could be derived from temperature and time measurements. The DTA has in the last 50 years increased so much in precision that its applications overlap with calorimetry, as is shown in the discussion of the different forms of differential scanning calorimetry, DSC (Sects. 4.3 and 4.4). 

More advanced techniques are now available and section 4.2.1.2 described differential scanning calorimetry (DSC) and differential thermal analysis (DTA). DTA, in particular, is widely used for determination of liquidus and solidus points and an excellent case of its application is in the In-Pb system studied by Evans and Prince (1978) who used a DTA technique after Smith (1940). In this method the rate of heat transfer between specimen and furnace is maintained at a constant value and cooling curves determined during solidification. During the solidification process itself cooling rates of the order of 1.25°C min" were used. This particular paper is of great interest in that it shows a very precise determination of the liquidus, but clearly demonstrates the problems associated widi determining solidus temperatures. 

DSC thermograms have been published [67] the reader is referred to a recent book [68] and reviews on DTA and DSC [69-71] for further details. Quantitative DSC has been reviewed [72]. Mathot [73] has reviewed recent advances in DSC, including (very) high pressure DSC (up to 550 MPa). Modulated DSC has been reviewed by ref. [21] and its practical applicability to polymeric systems has been described [74], Reading et al. [75] have discussed origin and interpretation of MTDSC. Special issues on temperature modulated calorimetry [76] and MTDSC [77,78] have appeared. 

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