From Prediction To Validation: Powder Processing And Characterization Of Single-Phase High-Entropy Carbides And Borides

The development of modern technologies in the fields of aeronautics and astronautics is appearing with the rise in demand for newer materials. One area of material research that is under investigation is the development of high-entropy ultra-high temperature ceramics (HE-UHTCs). This new class of material is proposed to withstand the performance requirements of next- generation propulsion and hypersonic vehicles. UHTCs have the aptitude to survive extreme operating conditions with increased strength, hardness, elevated temperature resistance, and corrosion resistance. As a newfound class of materials, there is much to learn with existing experimental data being scarce, due to trial-and-error methods being inadequate as it is time consuming and resource heavy. This work contributes to an Air Force Office of Scientific Research (AFOSR) effort to integrate computational tools and experimental approaches to accelerating HE- UHTC discovery. The primary focus of this thesis is highlighting the workflow of preparation, synthesis, and characterization of carbide and diboride powders. Using high energy ball milling (HEBM) to create homogeneous multicomponent mixtures that are then verified by elemental mapping from Energy Dispersive X-ray Spectroscopy (EDS). Ceramic surfaces are also analyzed by Scanning Electron Microscopy (SEM) for microstructure, grain distribution, and porosity. The crystallinity of the ceramic is then evaluated using X-ray Diffraction (XRD) to confirm the synthesis of single-phase materials. In addition to powder preparation, assisted in the two-step pressureless sintering process by contributing to sample preparation and process monitoring. Refining the manufacturing process with each iteration would improve specimens promoting better densification, grain formation, and less defects resulting in the successful synthesis of single-phase high entropy ceramics.