Structure-property relationships of earth and engineered materials

Structure-property relationships, which describe the connection between an atomic-scale structure and arising functional properties, inform our understanding of the physical world, from unraveling deep-earth dynamics to developing and tuning profitable materials. A comprehensive characterization of the structure of minerals and materials (from their atomic- to microstructure) is necessary for their full and informed implementation. This dissertation considers three overarching areas of research in which mineral and material structures are constrained and resultant large-scale consequences are detailed. First, the properties inherent in atmospheric mineral particles and their consequences on aerospace-grade material are investigated. The mineralogy and particle-based characteristics of test dusts are comprehensively described using a detailed mineralogical characterization workflow. The morphologies of these particles combined with particle-target experiments (conducted for different permutations of particle impact speed, angle of incidence, and target material type) reveal that erosion of targets from impacts of test dust particles is driven by normal particle impact velocity and target yield strength. These results were implemented into a particle bounce model in a companion paper which models a particle's change in kinetic energy following impacts. Second, the high-pressure crystallographic properties were investigated for ternary oxides (ABO4 compositional space). High-pressure experiments on the rare-earth phosphate (REEPO4) group show that whole-structure compressibility is driven by the compressibility of REEOx polyhedra. Moreover, we demonstrate a linear relationship between the REE ionic radius and REEPO4 compressibility, which is consistent through the I41/amd to P21/n phase transition. We also combine high pressure and high temperature data for the mineral zircon, which demonstrates entrapment conditions of zircon inclusions in garnet hosts. Third, the dynamical properties of the entropy-stabilized oxide Mg0.2Co0.2Ni0.2Cu0.2Zn0.2O, which are instrumental to its valuable thermal properties, are described using inelastic neutron scattering experiments combined with complementary VASP simulations. This work shows that energy contributions at room temperatures and above are driven by Mg and O ions. Calculations of thermal properties from VASP simulations reveal that phonon-driven entropy contributes a significant amount to total system entropy. In combination, this work contributes to three different fields of scientific research and uncovers how valuable, desired, or complex properties of earth and engineering materials are driven by inherent structural characteristics.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Geosciences

Department dc:contributor.department

Geosciences

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2025

Author dc:creator

• Ehlers, Alix Marie

Chairs dc:contributor.committeechair

• Caddick, Mark James
• Ross, Nancy L.

Committee members dc:contributor.committeemember

• Michel, Frederick Marc
• Rost, Christina Mary
• Slebodnick, Carla
• Duncan, Megan S.

• Structure-property relationships
• extreme conditions

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en

Dc Identifier Other

vt_gsexam:44680

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/138833