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Effective thermal insulation materials rely on the fabrication of dense, ultra‐high‐temperature ceramics that can withstand harsh environments. Hafnium carbide‐based ceramics are one of the leading materials that have the potential to perform relatively well in high‐temperature oxidizing environments under mechanical loading due to their thermal and mechanical stability. In this study, we explore the effects of processing conditions to create dense, ablation‐resistant HfC–SiC composites with a fixed composition of HfC–20 wt.% SiC using a hot‐pressing method. Sintering pressure, temperature, and time were varied and the material's relative density, phase composition, morphology, microstructure, and hardness were investigated. Composite ceramics with 99% relative density relative to a theoretical value were created by hot pressing at 2100°C for 1 h at 50 MPa and displayed a fine microstructure with an average grain size of ∼5 µm and a Vickers hardness of 22.9 ±.8 GPa. The mass loss was determined using an oxyacetylene torch with cross‐section investigations of oxide surface formations and subsurface microstructural changes. These HfC–SiC samples developed a 410 nm hafnium oxide layer on the surface upon torch exposure and had an average calculated recession rate of.028 µm/s. [ABSTRACT FROM AUTHOR]

X-ray photoelectron spectroscopy (XPS) confirmed that RF magnetron sputtering of h-BN onto unheated substrates produced a-BOxNy films under all of the sputtering conditions studied. The surface roughness improved and pinholes were eliminated as the deposition pressure increased. Analysis of the current density dependence on the electric field of the a-BOxNy films suggests field-enhanced Schottky emission and/or Frenkel-Poole emission transport mechanisms. The highest breakdown strength obtained was 8 MV cm−1. A bandgap of 3.9 eV was confirmed by spectroscopic ellipsometry and UV–Vis spectroscopy. An interface trap concentration (Nit) of 7.3 × 1010 cm−2 and interface state density (Nss) of 7.5 × 1012 eV−1 cm−2 were measured for transparent ITO/a-BOxNy/ZnO metal–insulator-semiconductor (MIS) structures. Approximately, 2 V was required to switch the a-BOxNy/ZnO interface from accumulation to inversion. [ABSTRACT FROM AUTHOR]