Kinetic Analysis of Non-isothermal Volume Melting Processes by Differential Scanning Calorimetry

Description

The onset of melting of standard samples, ascribed to surface melting, is generally used for calibration of calorimeters. However, in non-isothermal conditions, nucleation-driven volume melting, which is thermally activated, takes place. In this work, we propose an approximation in the frame of the classical nucleation and growth transformation kinetics to extend to non-isothermal regimes the analysis of processes governed by constant nucleation and interface controlled growth. The approximation allows both to observe the temperature dependence of nucleation activation energy with the overheating and to obtain the surface energy between the liquid nucleus and the surrounding solid phase for pure indium and lead (~ 10 mJ m−2) and for a Fe70B5C5Si3Al5Ga2P10 bulk metallic glass eutectic composition (~ 50 mJ m−2). These values are about 50% lower than the theoretical ones for homogeneous nucleation, which can be ascribed to the random heterogeneous nucleation occurring at the crystals boundaries.

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