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

Abstract

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 back-wards 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 ≈ 0.3 μW, and the baseline fluctuations around 1 μV ≈ 1 μW. 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.