Spectral emissivity measurements of liquid refractory metals by spectrometers combined with an electrostatic levitator

Abstract

A spectral emissivity measurement system combined with an electrostatic levitator was developed for high-temperature melts. The radiation intensity from a high-temperature sample was measured with a multichannel photospectrometer (MCPD) over the 700–1000 nm spectral range, while a Fourier transform infrared spectrometer (FTIR) measured the radiation over the 1.1–6 µm interval. These spectrometers were calibrated with a blackbody radiation furnace, and the spectral hemispherical emissivity was calculated. The system's capability was evaluated with molten zirconium samples. The spectral hemispherical emissivity of molten zirconium showed a negative wavelength dependence and an almost constant variation over the 1850–2210 K temperature range. The total hemispherical emissivity of zirconium calculated by integrating the spectral hemispherical emissivity was found to be around 0.32, which showed good agreement with the literature values. The constant pressure heat capacity of molten zirconium at melting temperature was calculated to be 40.9 J mol−1 K−1.

Apparatus for measuring the emittance of materials from far infrared to visible wavelengths in extreme conditions of temperature

“…In the geosciences field, emittance spectra are also unavoidable data to be able to understand heat transfer and transformation occurring in the earth mantle [3,4]. Several devices [5][6][7][8][9][10][11][12][13][14] have been already published around this subject but most of them are limited to the characterization of the emissivity of opaque materials in restricted spectral ranges. In this paper the technical details of an experimental apparatus designed to measure the emittance spectra of opaque and semi transparent materials in the whole spectral range where thermal emission is produced (i.e.…”

Challenges of Handling, Processing, and Studying Liquid and Supercooled Materials at Temperatures above 3000 K with Electrostatic Levitation

“…Then, the total hemispherical emissivity can be calculated by integrating the spectral hemispherical emissivity. The detailed procedures and the experimental set up can be found in [16].…”

“…Table 1 shows the typical sample size (diameter and mass) and applied voltage between the top and bottom electrode (10 mm apart) for levitating the samples against gravity. The data for zirconium, which became a reference, and is the most commonly used sample for electrostatic levitators [15,16], are also listed, for comparison. Compared with zirconium, sample masses of these metals are higher, while the sample sizes are smaller.…”

Heat capacity of liquid transition metals obtained with aerodynamic levitation

“…By assuming wavelength-independent emissivity values, Paradis et al converted the ratio into heat capacity. More recently, to correct for the uncertainty in assuming a constant emissivity across all wavelengths, Ishikawa et al [24,25,26,27,28,29] used a blackbody furnace (BBF) setup to determine the emissivity of the sample for use in heat capacity calculations. A BBF was also used with EML by Kobatake et al.…”

“…However, the heat loss of a sample levitated with ADL is more complicated than that in the case of ESL because convective heat loss is present. To calibrate our heat loss model for ADL, we utilized the heat capacity and emissivity values reported using ESL + BBF by Ishikawa et al [28]. The reported heat capacity values for Au, Cu, Fe, Ni, and…”