An inter-laboratory comparison involving three participants (PTB, CAE, TU Graz) was conducted on spectral emissivity measurements using experimental setups covering a temperature range from 1250 K to 4000 K and a spectral range between 0.6 μm and 20 μm. The main objective here was to carry out a European-level assessment of the coherency of spectral emissivity measurements at high temperatures. Three refractory materials (molybdenum, tungsten and isotropic graphite) were selected for this comparison. Samples were machined from the same batch of materials and then sandblasted and thermally annealed (PTB, CAE) to achieve uniform and stable surface properties and reduce potential scattering of results between participants. The spectral emissivity of the three materials was then measured by each of the three participants up to the maximum temperature attainable by the devices used. In the overlapping wavelength range from 600 nm to 1100 nm, all measurement methods were in good agreement with regards to their respective uncertainties.

NIST SRM 1155a is an AISI 316L stainless steel (Cr18–Ni12–Mo2) and Standard Reference Material (SRM) intended for use with test methods for elemental analysis. In a previous paper “Measurement of thermophysical properties of solid and liquid NIST SRM 316L stainless steel”, we already published reliable thermophysical properties of high temperature solid and of the liquid phase of this material such as temperature dependent enthalpy, density and electrical resistivity, as well as specific heat capacity for the solid and the liquid phase. In this paper, we add additional thermophysical properties obtained by ohmic pulse-heating and by the laser flash method, namely thermal conductivity and thermal diffusivity as a function of temperature. Furthermore we report surface tension measurement results of liquid SRM 1155a obtained by means of electromagnetic levitation. Simulation of processes like additive manufacturing, laser welding, laser cutting or metal casting depend on the above named quantities as input data. Ohmic pulse-heating as well as electromagnetic levitation are so called “containerless” investigation techniques and no significant chemical reactions of the hot liquid alloy with its surrounding occur. The data presented here are compared to the available literature data and are accompanied by an uncertainty analysis according to the “Guide to the Expression of Uncertainty in Measurement”.

Nickel is an important component in many alloys, so reliable surface tension data in the liquid phase are essential for simulation processes in the metal industry. First results for surface tension of liquid nickel from our working group by Aziz et al. [1], which led to the first publication on the topic of our Electromagnetic Levitation (EML) setup, delivered unusual high values compared to the literature, which itself covers a wide range. To find the reason for this behaviour the aim of this work was to investigate the surface tension of nickel samples from different suppliers at similar purity grades by the Oscillating Drop (OD) technique using the EML setup of the Thermophysics and Metalphysics Group at Graz University of Technology. Since no significant deviations between samples from different suppliers have been found, an extensive literature research according to various experimental and evaluation parameters has been performed. In the course of this investigation, the earlier obtained experimental data of Aziz et al. were re-evaluated. Due to gained awareness in evaluating the translational frequency in vertical direction, the mystery of these elevated surface tension results could be solved, so that in the end the originally obtained results of Aziz have been drastically decreased through re-evaluation.

W360 is a hot work tool steel produced by voestalpine BÖHLER Edelstahl GmbH & Co KG, a special steel producer located in Styria, Austria. Surface tension and density of liquid W360 were studied as a function of temperature in a non-contact, containerless fashion using the oscillating drop method inside an electromagnetic levitation setup. For both, surface tension and density, a linear model was adapted to present the temperature dependence of these measures, including values for the uncertainties of the fit parameters found. The data obtained are compared to pure iron (with 91 wt% the main component of W360), showing an overlap for the liquid density while there is a significant difference in surface tension (− 5.8 % at the melting temperature of pure iron of 1811 K).

In this study, some structure-sensitive thermophysical properties, namely, thermal conductivity, thermoelectric power, density and surface tension of liquid AlCu4TiMg alloy, as one of the most promising cast alloys to fabricate components for cars, aircraft and other complex engineering products, were investigated. Thermoelectric power was measured in a wide temperature range by the four-point contact method. Thermal conductivity was investigated by the steady-state concentric cylinder method. The oscillating drop technique combined with electromagnetic levitation was used for density and surface tension studies. The results obtained are compared with experimental and calculated data from literature for pure aluminum.

In this work, we present normal spectral emissivity data of solid and liquid molybdenum at a wavelength of 684.5 nm. The presented results are novel measurements on molybdenum, a material, which was already measured 15 years ago by our group. The present results indicate a lower emissivity in the liquid phase. The novel measurements were done within the European Metrology Programme for Innovation and Research (EMPIR) project 17IND11 Hi-TRACE. The optimized measuring system is an ohmic pulse-heating apparatus combined with microsecond Division of Amplitude polarimetry.

In this work, we perform high accuracy measurements of thermophysical properties for the National Institute of Standards and Technology standard reference material for 316L stainless steel. As these properties can be sensitive to small changes in elemental composition even within the allowed tolerances for an alloy class, by selecting a publicly available standard reference material for study our results are particularly useful for the validation of multiphysics models of industrial metal processes. An ohmic pulse-heating system was used to directly measure the electrical resistivity, enthalpy, density, and thermal expansion as functions of temperature. This apparatus applies high current pulses to heat wire-shaped samples from room temperature to metal vaporization. The great advantage of this particular pulse-heating apparatus is the very short experimental duration of 50 \(\upmu {{\hbox {s}}}\), which is faster than the collapse of the liquid wire due to gravitational forces, as well as that it prevents any chemical reactions of the hot liquid metal with its surroundings. Additionally, a differential scanning calorimeter was used to measure specific heat capacity from room temperature to around 1400 K. All data are accompanied by uncertainties according to the guide to the expression of uncertainty in measurement.

The density as a function of temperature was determined for liquid iridium (Ir) and rhenium (Re) by means of shadow imaging in ohmic pulse-heating experiments. In addition to regular experiments at $$0.23\,\text {MPa}$$, high-pressure experiments at static pressures between $$0.18\,\text {GPa}$$ to $$0.30\,\text {GPa}$$ were performed to increase the metals’ boiling point and thus determine density data at temperatures far exceeding the boiling temperature at atmospheric pressure. By this means, the experimentally accessible liquid range could be extended by roughly $$2000\,\text {K}$$ (Ir) and $$6000\,\text {K}$$ (Re) compared to data reported in the literature. In a second step, the experimental data were used to estimate critical temperature, critical density, and the complete phase diagram in the density–temperature plane. A comprehensive comparison with literature data was conducted.

This paper presents a new production method for a spherical and monocrystalline aluminum powder. Aluminum powder of irregular particle shapes was mixed with silica nanoparticles and heated to a temperature above the melting point of aluminum. Due to its molten state, high surface tension, and poor wettability, the aluminum particles were transformed into liquid and spherical droplets separated by silica nanoparticles. The spherical shape was then retained when the aluminum particles solidified. The influence of the processing temperature on the particle shape, phase composition, and microstructure was investigated. Moreover, calorimetric, X-ray diffraction, grain size, and scanning electron microscopy with electron backscatter diffraction (SEM-EBSD) measurements of the particles' microstructure are presented. It is proven that, by this means, a spherical and monocrystalline aluminum powder can be efficiently created directly from an air-atomized irregular powder. The observed phenomenon of particles becoming round is of great importance, especially when considering powder preparation for powder-based additive manufacturing processes.

Density as a function of temperature was measured for the liquid transition metals niobium and tungsten by means of ohmic pulse-heating. The generated data are extensively compared to the existing literature data, and the uncertainty is critically assessed according to the guide to the expression of uncertainty in measurement (GUM). Starting from the obtained liquid-phase density regression, the phase diagram, and the critical point, i.e., critical temperature \(T_{\mathrm {c}}\) and critical density \(\rho _{\mathrm {c}}\) of niobium and tungsten are estimated. The so-obtained critical point for these two high-melting metals is compared to the data available in the existing literature.

Over the last decades, many experimental methods have been developed and improved to measure thermophysical properties of matter. This chapter gives an overview over the most common techniques to obtain thermal conductivity λ as a function of temperature T . These methods can be divided into steady state and transient methods. At the Institute of Experimental Physics at Graz University of Technology, an ohmic pulse-heating appa- ratus was installed 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 in more detail. To determine thermal conductivity and thermal dif- fusivity 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 negligibly small in most cases. Uncertainties for thermal conductivity for aluminum have been estimated ±6% in the solid phase and ±5% in the liquid phase.

In order to determine the density of tantalum over the entire liquid phase (at the pressure applied) and several hundred K into the super-heated region, the method of ohmic pulse-heating was applied. For this purpose, images of the thermal radial expansion of the resistively heated sample wires were taken with an adapted CCD system. A newly integrated high-power photoflash and improved triggering of the experiment allowed the acquisition of high-contrast shadow images of the expanding wires. To reduce the uncertainty arising from simultaneous pyrometric temperature measurement, the change in normal spectral emissivity as a function of temperature was additionally taken into account. In this work, the density versus temperature relationship of tantalum is reported and compared to existing literature data. From the newly obtained liquid-phase density, critical point data of tantalum, such as critical temperature and critical density, were estimated via an extrapolation procedure. Furthermore, an estimate of the phase diagram in the density versus temperature plane is given. The work is concluded by a rigorous density uncertainty estimation according to the guide to the expression of uncertainty in measurement (GUM).

This work presents experimental results of thermal diffusivity and computed values of thermal conductivity of pure polycrystalline ruthenium specimens in the temperature range 200 to 1670 K for diffusivity and 250 to 1650 K for conductivity. The results of thermal diffusivity were obtained by an interlaboratory comparison using the laser flash method. A brief description of the two measuring systems applied is given. Specimens were disk shaped, 2 and 3 mm in thickness and 10 and 12.5 mm in diameter. Literature data are used to correct for thermal expansion of the specimens. All the values obtained from the individual laboratories as well as a polynomial fit to the results over the entire temperature range are presented and compared with results found in literature. By using the thermal diffusivity data and previously measured results of specific heat capacity of different pure polycrystalline ruthenium specimens, the values of ruthenium thermal conductivity are estimated and presented together with related literature data.