Experimental Methods to Obtain Thermal Conductivity and Thermal Diffusivity of Liquid Metals and Alloys: A Review

Abstract

Over the last decades many experimental methods have been developed and improved to measure thermophysical properties of matter. This publication gives an overview over the most common techniques to obtain thermal conductivity and thermal diffusivity a of solid and liquid samples at high temperatures. These methods can be divided into steady state and transient methods. The steady state methods are all those, which allow a direct measurement of thermal conductivity or thermal diffusivity at constant temperatures. Transient methods usually offer a simple set up and are not as time consuming as steady state ones. At the Institute of Experimental Physics at Graz, University of Technology, an ohmic pulse-heating apparatus has been set up in the 1980s and has been further improved over the years, which allows the investigation of thermal conductivity and thermal diffusivity for the end of the solid phase and especially for the liquid phase of metals and alloys. This apparatus will be described here in more detail. Wire shaped metal samples are resistively volume heated as part of a fast capacitor discharge circuit. Time resolved measurements with sub-μs resolution of current through the specimen are made with a pearson probe, voltage drop across the specimen is determined with knife-edge contacts and ohmic voltage dividers. Radiance temperature of the sample is measured with a pyrometer and volume expansion of the wire with a fast acting CCD-camera. To determine thermal conductivity and thermal diffusivity with the ohmic pulse-heating method, the Wiedemann-Franz law is used. There are electronic as well as lattice contributions to thermal conductivity. As the materials examined at Graz, University of Technology are mostly in the liquid phase, the lattice contribution to thermal conductivity is negligible small in most cases.