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IV Molten & Gas State Processing

Influence of Oxygen on Surface Tension of Zirconium

Jie Zhao, Jonghyun Lee, Rainer Wunderlich, Hans Fecht,

Stephan Schneider, Michael SanSoucie, Jan Rogers and Robert Hyers

Abstract Zirconium samples with different oxygen concentrations were tested using a ground-based electrostatic levitator at NASA Marshall Space Flight Center. The surface tension of liquid zirconium samples was measured in both undercooled and superheated conditions. The effect of oxygen on surface tension was determined: oxygen in zirconium samples decreases the surface tension of liquid samples, with only a small change in the temperature dependence.

Keywords Electrostatic levitation • Surface tension • Oxygen • Zirconium

Introduction

The influence of oxygen on the thermophysical properties of zirconium is being investigated using MSL-EML (Material Science Laboratory Electromagnetic Levitator) on ISS (International Space Station) in collaboration with NASA, ESA (European Space Agency), and DLR (German Aerospace Center). Zirconium samples with different oxygen concentrations are being processed through multiple melt cycles, during which the density, viscosity, surface tension, heat capacity, and

J. Zhao • J. Lee (H) • R. Hyers

Department of Mechanical and Industrial Engineering, University of Massachusetts, Amherst, MA, USA

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R. Wunderlich • H. Fecht

Institute of Micro and Nanomaterials, Ulm University, Ulm, Germany

S. Schneider

Institute for Materials Physics, German Aerospace Center (DLR), Cologne, Germany M. SanSoucie • J. Rogers

NASA Marshall Space Flight Center, Huntsville, AL, USA © The Minerals, Metals & Materials Society 2017

A. Allanore et al. (eds.), Materials Processing Fundamentals 2017,

The Minerals, Metals & Materials Series, DOI 10.1007/978-3-319-51580-9_5

electric conductivity are being measured at various undercooled and superheated temperatures. The facility check-up of MSL-EML and the first set of melting experiments were successfully performed in 2015. The first zirconium sample was tested at the end of 2015. As part of ground support activities, the thermophysical properties of zirconium and Zr-O were measured using a ground-based electrostatic levitator located at the NASA Marshall Space Flight Center. The influence of oxygen on the measured surface tension was evaluated over a wide range of temperature. The results of this research will serve as reference data for comparison to those measured in ISS.

Electrostatic levitation (ESL) is a containerless method for processing materials including metallic glasses, quasicrystal-forming alloys, and industrial alloys such as steels, semiconductors and refractory metals. Compared with samples used by EML, samples in ESL experiments are smaller with typically 2-3 mm diameter (68 mm in EML). The sample is electrically charged by a D2 arc lamp and levitated in an electrostatic field generated by upper and lower electrodes. Figure 1 show a levitated sample during measurement and Fig. 2 gives a schematic ESL system [1]. The sample’s position is maintained by two dual-axis position detectors and a

Sample levitated between electrodes and heated by laser [1]

Fig. 1 Sample levitated between electrodes and heated by laser [1]

Schematic of ESL system [1] feedback system

Fig. 2 Schematic of ESL system [1] feedback system. The charge on samples can be controlled by an UV source via the photoelectric effect. Samples can be levitated as long as charged. To achieve desired temperatures in study the sample is heated by a 200 W Nd:YAG laser. A radial camera records the processing video of sample. The electrostatic levitator facilities require a non-contact method for measuring temperature. ESL experiments use optical pyrometers to measure thermal radiation emitted by sample. Then the temperature can be determined by the emissivity of the sample. The emissivity of a few materials can be measured directly at a common wavelength in NASA MSFC (Marshall Space Flight Center) ESL. [1] However, the emissivity value of the tested Zr samples was calibrated using the phase transition temperatures, a-Zr to p-Zr at 1136 K.

 
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