Abstract
Recreating the extreme conditions of the deep Earth and other planetary interiors poses significant experimental difficulty. The primary tool for investigations of material properties at high pressure and temperature is the laser-heated diamond anvil cell. Laser heating can routinely generate temperatures of many thousand Kelvin at pressures well into the megabar range, but large thermal gradients and poor temperature stability introduces significant uncertainty, limits the accuracy of measured data, and prohibits analyses requiring long acquisition times. Resistive heating techniques provide greater temperature stability, more precise control, reduced thermal gradients, and temperature uncertainties an order of magnitude smaller. However, resistive heaters external to the diamond anvils are limited in accessible temperature range and cannot recreate the conditions of the Earth’s lower mantle as the unpressurised diamonds begin to graphitise beyond ∼1500 K. Internal resistive heating (IRH), in which heat is generated only within the pressure chamber, can extend the accessible temperature range significantly. Experiments in which the metallic heater doubles as the sample can be performed up to several thousand Kelvin, but existing designs applicable to non-metallic samples are limited to 1900 K at pressures beyond 10 GPa.Here I describe the development of a new IRH design capable of generating temperatures well in excess of 3000 K across a pressure range equivalent to 1000 km depth within the Earth. A novel ‘split-gasket’ approach is adopted which reduces the technical difficulty of performing IRH experiments, improves the isolation of the heating filament, and allows extremely stable, homogeneous heating of both metallic and non-metallic samples. The application of IRH to studies of both solids and melts is investigated and discussed. The IRH design is well suited for the rapid collection of high-resolution P-V-T datasets, the precise demarcation of phase boundaries (including melting), and for experiments requiring long acquisition times at high temperature. The IRH technique is also well suited to stabilising large volumes of melt at high-pressure, and tools for the analysis of liquid x-ray diffuse scattering data are developed and described. IRH provides a new and accessible tool for investigating material properties at extreme conditions.
| Date of Award | 27 Sept 2022 |
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| Original language | English |
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| Supervisor | Oliver T Lord (Supervisor) & Simon C Kohn (Supervisor) |