Effect of 2 vol % Graphene Additive on Heat Transfer of Ceramic Material in Underexpanded Jets of Dissociated Air

Using a high-frequency induction plasma torch, features of the behavior of ultra-high-temperature ceramic materials HfB2-30 vol % SiC and (HfB2-30 vol % SiC)-2 vol % C-G under the influence of underexpanded jets of dissociated air have been studied. The heat fluxes measured at the final stage of the experiment have been found to be equal to 120 and 111 W cm(-2), respectively. It has been found that for graphene-modified ceramics, the surface temperature is slightly lower (by 35-75 degrees C) compared to base UHTCs; however, the microstructure, elemental and phase composition of the oxidized surface differed greatly: for (HfB2-30 vol % SiC)-2 vol % C-G, in addition to a decrease in the number of spherical convex particles formed at the exit of the borosilicate melt on the surface, the formation of openwork layered formations, presumably, boric acid, has been noted. For the estimated integral radiation coefficients, a tendency to decrease in the course of thermochemical exposure has been noted. It has been established that under the conditions of a supersonic air plasma jet flow, the studied materials manifest themselves as low-catalytic ones.