Thermophysical properties of rhodium obtained by fast pulse-heating.

ABSTRACT

The so-called platinum metals are Ru, Rh, Pd, Os, Ir and Pt. Our workgroup has already published data on Pd, Ir and Pt. The present work will focus on measurements of the thermophysical properties of rhodium, which have been carried out recently. The scarce literature data available emphasize the need for new measurements. Using a rapid pulse-heating technique, wire-shaped specimens are ohmic-heated by the passage of a large current pulse. This fast heating drives the sample from room temperature up into the liquid phase in typically 50 µs and thus prevents chemical reactions and gravitational distortions. Enthalpy, electrical resistivity and volume expansion can be obtained as a function of temperature. From these results, heat of fusion, heat capacity and change of density can be calculated as a function of temperature. A set of data of the mentioned quantities will be presented and the comparison to literature values will be discussed within this study. Additionally we will contrast the results for rhodium with the respective results for Pd, Ir and Pt. The conformity of data published decades ago with our new measurements is fairly high. Rhodium does not show unexpected behaviour regarding the comparison to Pd, Ir and Pt.