PhD Student: Alex Austin

PhD Supervisor: Dr. Katharina Marquardt

In this PhD project we focus on the investigations of ceramics/rocks exposed to high-temperature and supercritical water. Understanding the reaction mechanism at interfaces and the character variations of interfaces as a function of exposure to H2O is at the heart of the study. 

Left: a) and b) are secondary electron images of a) a pristine sample, the grains are smooth and show evidence of structural equilibrium. b) Altered sample, with platy minerals forming on the surface of the sample. c) Bright field transmission electron micrograph of altered interfaces and transforming phases, the inset is a diffraction pattern of one of the mineral grains. Evidence of the fluid primarily reacting at the interfaces is visible at the interface running from left to right between the light grey and darker grey crystals. While closer to the original surface (right side of micrograph), the lamella progressing though the crystals are evidence of further advanced transformation. d) High resolution transmission electron micrograph of the interface. Bubble shaped voids are visible in places where fluids migrated during the experiment.

This project ranges from the synthesis of starting materials, conduction of experiments and characterization the material using mechanical testing, novel scanning electron microscopy techniques as developed for electron backscatter diffraction (EBSD) and transmission Kikuchi diffraction (TKD). Additionally, transmission electron microscopy (TEM) and infrared spectroscopy will be employed to study the interfacial structure and composition of the ceramics at the nm-scale.