Structure, properties and microgravity processing of liquids and glasses

Abstract

Containerless processing was used to access and study supercooled liquids and glasses that cannot be made using conventional melting approaches. In-situ measurements of melt atomic structure and density provided insight into how the glass forms. Experiments included making measurements in microgravity where buoyancy driven convection and sedimentation are suppressed. Here we examine the structure and properties of rare earth-aluminate composition liquids and some glasses made from them. The structures show a fundamentally different network behavior from the classical Zachariasen model. The network comprises four and about 40 % five coordinated aluminum ions that share corners or edges and often form triply bonded species with an oxygen ion. The concept of Kn is used to evaluate the glass forming behavior in terms of network connectivity and bonding. The temperature dependence of density of the liquid is reported and discussed in the context of processing molten materials in reduced gravity where bubbles can be trapped in the liquid due to lack of buoyancy. The interior structure in samples was investigated using X-ray tomography to investigate how bubbles can cluster inside a liquid drop.