Heat inertia and temperature gradient in the treatment of DTA peaks

Historical development of methods and theoretical basis of differential thermal analysis (DTA) are outlined. DTA is a procedure in which the heat transfer toward the sample plays an important function and the associated process in the sample is manifested by deviation of temperature difference from its background. This difference Delta T is not directly proportional to the rate of the process (d alpha/dt) but includes also the effect of heat inertia proportional to the slope d Delta T/dt as it was derived and incorporated into DTA equation by Vold (Anal Chem 21:683-688, 1949), Borchardt and Daniels (J Am Chem Soc 79:41-46, 1957), and suggested to be corrected in the authors' previous papers (1976). However, the correction with respect to heat inertia has so far been omitted (particularly after the boom of non-isothermal kinetics started by paper of Kissinger (Anal Chem 29:1702-1706, 1957)). DTA experiments with rectangular pulses realized by micro-heater inside the sample show that the correction of DTA signal employing calculated heat inertia term of the DTA equation is reliable but not yet fully sufficient. It was a reason to derive a more complete DTA equation including a term expressing the changes in the temperature field inside the sample during process. Possibilities for improving of DTA (and DSC) data processing are discussed. Itemized 150 references with titles.