Surface Transformation Of Ultrahigh-Temperature Ceramics HfB2-SiC-C(graphene) Under The Influence Of High-Speed Disossociated Nitrogen Jets

In order to study the promising potential of HfB2–30 vol % SiC ultrahigh-temperature ceramic materials modified with low amounts of reduced graphene oxide for the creation of aerospace equipment intended for use in N2-based atmospheres, the effect of high-speed dissociated nitrogen flow on it has been investigated. It has been established that under the chosen conditions of exposure during the stepwise increase of the anode power supply of plasma torch and, accordingly, the influencing heat flux, at certain parameters there is a sharp increase in the surface temperature from ~1750 to 2000-2100°C. At the same time, further increase of the heat flux has no obvious and proportional effect on the temperature of the sample surface, which may indicate its high catalyticity with respect to the reactions of surface recombination of atomic nitrogen. It is shown that the surface layers of the material undergo chemical transformation (removal of silicon-containing substances, formation of a new phase based on HfN), which is accompanied by a significant change in the microstructure (formation of dendrite-like structures), which affects the optical and catalytic characteristics of the surface.