Thermophysical Property Measurements of Molten Oxides by the Electrostatic Levitation Furnace onboard the International Space Station
Abstract
The electrostatic levitation method is a containerless technique that levitates a charged sample by Coulomb force between the sample and the surrounding electrodes. Since the technique doesn't utilize container, high temperature liquids can be handled without contamination under wide temperature range including undercooling range. Therefore, the technique has been utilized for precise measurements of thermophysical properties as a function of temperature, which are necessary for improvement of materials processing and investigation of liquid structure. Originally the technique was developed by Rhim et al. ^{1} at the Jet Propulsion Laboratory (JPL). On the basis of their knowledge, the Japan Aerospace Exploration Agency (JAXA) has been developing the technique for more than 20 years ^{2}. As a result, JAXA succeeded in measuring thermophysical properties of molten metals with high melting temperature such as W, Re and Ta on the ground. However, the measurements of molten oxides were scarcely performed on the ground, because oxides are difficult to charge and then do not levitate. In order to resolve this problem and measure physical properties of oxides, JAXA designed and fabricated the Electrostatic Levitation Furnace onboard the International Space Station (ISS-ELF) ^{3}which enables to levitate oxides with small charge due to an effect of microgravity. First, to measure molten density, one of the fundamental thermophysical properties, the capabilities of levitation and heating were checked by using alumina (Al _{2}O _{3}). As a result, each sample was succeeded in levitating and melting fully in dry air by four semiconductor lasers. When the sample was fully molten, all lasers were powered off to cool it. During cooling, the temperature was measured by a pyrometer. The sample images were recorded by using CCD camera and UV-light. From the image and weight after the measurement, the density was calculated. The density as a function of temperature shows good agreement with that obtained by Langstaff et al. (2013) ^{4} using aerodynamic levitator. It also shows about 2 % lower than our earlier results obtained by using electrostatic levitator on the ground in high vacuum condition (Paradis et al. 2004) ^{5}. This result proves the validity of the density measurement with the ISS-ELF. The functional check for the surface tension and viscosity measurement is being currently conducted, and detailed results will be reported later.1. Rhim, W.-K., Chung, S. K., Barber, D., Man, K. F., Gutt, G., Rulison, A., Spujt, R. E, Rev. Sci. Instrum. 64, 2961-2970 (1993)2. Ishikawa, T., Paradis, P.-F. in High-Temperature Measurements of Materials, ed. by Fukuyama, H and Waseda, Y (Springer Berlin Heidelberg 2009) P. 173-1953. Tamaru, H., Ishikawa, T., Okada, J.T., Nakamura, Y., Ohkuma, H., Yukizono, S., Sakai, Y., Takada, T., Int. J. Microgravity Sci. Appl. 32, 32104 (2015)4. Langstaff, D., Gunn, M., Greaves, G. N., Marsing, A., Kargl, F.: Aerodynamic levitator furnace for measuring thermophysical properties of refractory liquids. Rev. Sci. Instrum. 84, 124901 (2013)5. Paradis, P.-F., Ishikawa, T., Saita, Y., Yoda, S.: Non-contact thermophysical property measurements of liquid and undercooled alumina. Japanese Journal of Applied Physics 43, 1496 - 1500 (2004).
- Publication:
-
42nd COSPAR Scientific Assembly
- Pub Date:
- July 2018
- Bibcode:
- 2018cosp...42E1828K