Thermodynamic properties of under-cooled silver melts

Abstract

Differential scanning calorimeter technique combined with the traditional fluxing treatment was used to investigate the specific heat and related thermodynamic properties of under-cooled pure silver melts. The specific heat of the under-cooled melt showed a linear dependence on the temperature in the range of the obtained under-cooling from 0 to 198 K. The related thermodynamic properties of silver, such as the entropy change, the enthalpy change and the Gibbs free energy difference between the under-cooled melt and the solid phase, were derived from the measured specific heat. The relations between the temperature and the thermal diffusion or the thermal conductivity of the under-cooled melt were analyzed respectively. under-cooled silver melts, specific heat, thermodynamic propertiesSpecific heat and related thermodynamic properties of under-cooled liquid melts are very important parameters to further research on the mechanism of non-equilibrium solidification and formation of new metastable materials, and these properties are also essential for describing the nucleation and growth phenomena in under-cooling melts [1-6]. In the past several decades, the specific heat and related thermodynamic properties of under-cooled metals, alloys and oxides have been investigated, by electromagnetic [7-15] and electrostatic [16,17] levitation, whose techniques can easily realize the deep under-cooling of melts. But the heat transmission in the process of levitation lacks accurate control and measurement, and the techniques can measure only the average specific heat of under-cooled melts, which does not accurately show the relation between specific heat and temperature. During repeated melting and solidification, the sample in a suitable flux can be purified and the container wall effects on heterogeneous nucleation can be suppressed. As a result, deep under-cooling can be obtained [18,19]. When combined with the DSC technique, accurate measurement of the specific heat of the deeply under-cooled melts is realized [20][21][22][23].Studies on the measurement of the specific heat of deep under-cooled metal liquids and alloys have been reported recently [24][25][26][27][28], but the accurate experimental data on the specific heat and related thermodynamic properties of the under-cooled melts are still very scarce, for high-melting metals and alloys in the temperature range above 1200 K in particular. The recent literature covers only the measurements of some pure metals and simple binary alloys. In this paper, fluxing treatment is used within a DSC facility to investigate pure silver, a high-melting metal with the melting point temperature of 1233.6 K. The related thermodynamic properties including the enthalpy change, the entropy change, the Gibbs free energy difference, thermal diffusivity and thermal conductivity, are derived on the basis of the experimental results. And their temperature dependence is discussed, respectively. The experimental results are compared with several traditional approximate models based on different...