2020 Theses Doctoral

Towards Real Time Characterization of Grain Growth from the Melt

Wright, Christopher James

Single crystal materials have unique properties which are endowed by their long ranging atomic order. Growing these crystalline materials can be difficult, as entropy favors disordered grains. The optical floating zone furnace provides an efficient way to make novel single crystal materials, enabling the study of crystals with complex chemical makeup which other techniques would not be able to provide. However, the growth mechanisms of these crystals is poorly understood, leaving the process of making them prone to trial and error and limiting its application in the broader research community.

This work aims to understand the microstructural dynamics of floating zone growth using x-ray scattering techniques. These techniques include x-ray diffraction tomography and two dimensional crystal mapping. One focus of this work is building the computational infrastructure to process the large stream of heterogeneous data which results from these techniques. Additionally, this work includes computational and experimental commissioning of the x-ray diffraction tomography technique, helping to understand the advantages and limitations of the current approaches. These pieces of infrastructure are then used to characterize the growth of Rutile crystals via a float zone furnace. Particular attention is paid to the competition amongst the grains, and how certain grains are selected from the plethora which are created at the beginning of the growth.