22 pure elements - 30 years of pulse heating experience

G. Pottlacher1

1Institute of Experimental Physics, Graz University of Technology, Austria

Keywords: dynamic pulse calorimetry
property: thermophysical properties
material: pure metals

A dynamic calorimetric pulse experiment utilizes resistive self-heating of an electric conductor, typically wire shaped, by passing a large current pulse over the sample. As a result of the materials’ resistivity, the test specimen can be heated from room temperature up to melting, further through the liquid phase and finally up to the boiling point in several microseconds. The following parts are common for all pulse heating experiments: energy storage, typically battery banks or capacitor banks with a charging unit, main switching unit such as high-voltage mercury vapor ignition tubes, an experimental chamber with windows for optical diagnostics and the ability to maintain a controlled ambient atmosphere. Pulse heating experiments are commonly performed under inert ambient atmosphere, e.g. nitrogen or argon, at ambient pressure, in vacuum or at elevated ambient pressures. Quite often data recording equipment is placed in a shielded room.

The quantities which are typically recorded as a function of experimental duration during such an experiment in the solid and in the liquid phase are: the current through the sample, the voltage drop across the sample, the temperature by surface radiation for optical thermometry and other quantities such as thermal expansion of the sample and polarization information for optical properties measurements such as normal spectral emissivity. Based on the initially measured quantities, thermophysical properties like enthalpy, specific heat capacity, electrical resistivity, volumetric expansion, thermal conductivity and thermal diffusivity as a function of temperature can be obtained for the material under investigation up to the end of the liquid phase, assuming that the mass of the sample at room temperature is known. These data are useful as input parameters in numerical simulations and it is a major purpose of our ongoing research to provide data for simulations performed by the metal working industry.

Our work group has rendered outstanding services in the field of dynamic pulse calorimetry within the last thirty years. Today, only few more experiments on pure metals are to be expected, because almost all elements, which are suitable for our pulse-heating system so far, have been investigated. These elements are: Co, Cu, Au, Hf, In, Ir, Fe, Pb, Mo, Ni, Nb, Pd, Pt, Re, Rh, Ag, Ta, Ti, W, V, Zn, and Zr. Therefore it is now a good starting point for comparative analyses within these 22 elements.

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