Adiabatic Calorimetry Approach to Assess Thermal Influences on the Indium Melting Point

Within the framework of the Euramet project 732, LCM/LNE-CNAM has recently proposed a new device to investigate the melting point of indium (156.5985 °C) by the way of an adiabatic calorimetry approach. An apparatus based on a cell-within-cell configuration was developed and experimentally tested. First results highlighted parasitic heat flows due to the geometrical characteristics of the cell, disturbing significantly the isothermal condition within the calorimeter. Such thermal effects were also clearly identified with a specific numerical model developed for this purpose. Considering the remarkable agreement between the model and relevant experiments, an optimization step has been carried out to design a suitable cell geometry. A new enhanced cell was subsequently fabricated and arranged within the calorimeter (indium load of 122.32 g). The purpose of this article is to introduce the thermal behavior of such a highly effective apparatus, while presenting some series of measurements; on the one hand, the melting point of indium under adiabatic conditions is studied, and on the other hand, the so-called continuous heat flow method under isothermal conditions is worked out. The obtained results are discussed and analyzed according to the impurity concentrations into the ingot (sum of individual estimate method).