Property Measurements of Molten Oxides at High Temperature Using Containerless Methods

To understand the hyperordered structures found in new glasses fabricated with containerless methods, it is of paramount importance to know not only their atomic structures but also their macroscopic thermophysical properties. However, due to their high melting temperatures and the risk of contamination from the crucibles, molten oxides whose melting temperatures are above 2000 ℃ can hardly be processed using conventional methods. This explains that the published data on thermophysical properties are very scarce. In this chapter, four containerless methods capable of measuring several thermophysical properties such as density, surface tension, and viscosity are introduced. Three of them use a gas flow to levitate samples against gravity, while the electrostatic levitation furnace onboard the International Space Station utilizes the Coulomb force to spatially position samples in microgravity. Features of each method are summarized in this chapter, including their advantages and disadvantages. Finally, the measured data of refractory oxides whose melting temperatures are above 2000 ℃ are summarized.