Modification of HfB2-30% SiC UHTC with Graphene (1 vol %) and Its Influence on the Behavior in a Supersonic Air Jet

Oxidation under exposure to a supersonic dissociated air jet (with heat fluxes in the range 363-779 W/cm(2), total exposure time: 2000 s) was studied for HfB2-30 vol % SiC ultra-high-temperature ceramics (UHTC) doped with a lowered amount (1 vol %) of reduced graphene oxide (GO). Doping the ceramics with a relatively low amount of reduced GO (1 vol %) did not prevent a dramatic increase in the average surface temperature to 2300-2400 degrees C. However, the existence time of surface temperatures below 1800-1850 degrees C increased considerably, probably due to an increase in the thermal conductivity of the ceramics. The ablation rate of the material was determined as 6.5 x 10(-4) g/(cm(2) min), which is intermediate between the respective values for HfB2-SiC ceramics and the ceramics doped by 2 vol % graphene. The microstructure features and elemental composition of the oxidized surface and chips of the material were studied. The structure and thickness of the oxidized near-surface region were determined.