All ETDs from UAB

Advisory Committee Chair

Yogesh K Vohra

Advisory Committee Members

Shane Aaron Catledge

Cheng-Chien Chen

Patricia Kalita

Haibin Ning

Document Type


Date of Award


Degree Name by School

Doctor of Philosophy (PhD) College of Arts and Sciences


This work employs a broad and in-depth range of experimental x-ray diffraction techniques to probe anisotropic compression effects and shear deformation behavior in transition metals and their borides to ultra-high pressures. These techniques include the custom designed toroidal diamond anvils fabricated by focused ion beam machining to compress samples to pressure of 358 GPa equating to that at the Earth’s core. This has been used to generate a new equation of state for Ta metal for pressure calibration within the field of high-pressure physics and test the validation of other pressure calibrations claiming > 500 GPa of pressure. This has also enabled high pressure studies on Re and Os-based metal borides that have shown considerable strength and incompressibility rivaling that of diamond to pressures 3-5 times greater than any previous studies. The techniques within this work include the employment of Radial X-ray Diffraction and Lattice Strain Theory to determine hydrostatic compression and shear strength measurements on transition metal Os and transition metal boride ReB2. This technique has allowed the validation of Density Functional Theory (DFT) calculations by estimating hydrostatic compression parameters (pressure, volume) for accurate theory-experiment comparisons. These hydrostatic experimental measurements have elucidated details of anomalies present within lattice parameters of Os under compression and iv anisotropic compression documented in ReB2 and Os2B3 by comparison with non-hydrostatic compression studies and DFT. Finally, high pressure and high temperature studies on transition metal boride Os2B3 were conducted to 5.4 GPa and 1273 K to map out the thermal equation of state and determine its mechanical properties and thermal expansion coefficients at high temperatures. The thermal phase stability and high strength have suggested the use of this material into hypersonic engine devices, high strength coatings, and industrial tools. The experiments conducted in these studies were done in collaboration with major national laboratories such as Argonne National Laboratory and Los Alamos National Laboratory and provided for the first-time anisotropic compression data and shear strength data on transition metals and their borides under extreme environments.



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