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

Abstract

Abstract:Over the last 20 years, great progress has been made in techniques for electrostatic levitation, with innovations such as containerless thermophysical property measurements and combination of levitators with synchrotron radiation source and neutron beams, to name but a few. This review focuses on the technological developments necessary for handling materials whose melting temperatures are above 3000 K. Although the original electrostatic levitator designed by Rhim et al. allowed the handling, processing, and study of most metals with melting points below 2500 K, several issues appeared, in addition to the risk of contamination, when metals such as Os, Re, and W were processed. This paper describes the procedures and the innovations that made successful levitation and the study of refractory metals at extreme temperatures (>3000 K) possible; namely, sample handling, electrode design (shape and material), levitation initiation, laser heating configuration, and UV range imaging. Typical results are also presented, putting emphasis on the measurements of density, surface tension, and viscosity of refractory materials in their liquid and supercooled phases. The data obtained are exemplified by tungsten, which has the highest melting temperature among metals (and is second only to carbon in the periodic table), rhenium and osmium. The remaining technical difficulties such as temperature measurement and evaporation are discussed.

Environmental conical nozzle levitator equipped with dual wavelength lasers

“…More information on levitation techniques can be found in the following reviews. [53][54][55][56] The environmental controlled conical nozzle levitator (E-CNL) equipped with dual-wavelength lasers (CO 2 and Yb) is an aerodynamic levitation system designed in collaboration with Materials Development Inc. (MDI) to study ultra-high temperature materials and UHTCs (both oxide and non-oxide) in a controlled (varying gas composition), containerless environment, up to and beyond ∼4000 K. The E-CNL addresses the two key problems with studying UHTCs. Many UHTCs and ultra-high-temperature materials of interest can have a range of electrical conductivity at various temperatures.…”

“…The systems that are currently in operation have been optimized for either oxide or metallic materials, and the highest reported temperatures are ∼3773 K 51 on oxide systems in oxygen using aerodynamic levitation and ∼3673 K on non‐oxide systems in inert atmospheres 41,52 using ESL. More information on levitation techniques can be found in the following reviews 53–56 …”

Active disturbance rejection control of test sample in electrostatic suspension system

“…Compared to other suspension methods such as the electromagnetic suspension system [9,10], the aerodynamic suspension system [11] and the acoustic suspension system [12], the electrostatic suspension system could suspend the nonmetallic materials, realize the suspension in vacuum environment and separate the heating from the suspension. More importantly, the electrostatic suspension system causes little influence on the test sample with better control performance [13].…”