Recent improvements in conduction calorimetry. Application to the martensitic transformations in shape memory alloys

A critical reading of the work of Tian and Calvet and the actual state of the art in thermostats, temperature control and the modelling of differential conduction calorimeters suggest a backwards evolution to non-differential calorimeters. An elementary design shows increased performances at constant temperature; the sensitivity is 700 mV W-1 at room temperature, the short-term noise around 200 nV approximate to 0.3 mu W, and the baseline fluctuations around 1 mu V approximate to 1 mu W. Measurements of the dissipated heat power, indicative of the internal processes after a heat treatment (different types of quench) were realised for a Cu-Zn-Al shape memory alloy. The experimental results established that the dissipated heat evolves in time for at least 2 or 3 days. At least two time constants were detected and, as expected, the values are dependent on the quench type and sample mass.