Low-surface-temperature jump behavior of C/SiC composites prepared via precursor impregnation and pyrolysis in high-enthalpy plasma flows

The response of C/SiC composites prepared via precursor impregnation and pyrolysis was investigated in a 1 MW plasma wind tunnel. Under a considerable aero heating of up to 26.2 MJ/kg of specific total enthalpy, the samples were exposed to heat fluxes exceeding 5.7 MW/m² and low pressures of 4.5–6.6 kPa. The samples were able to withstand low heat fluxes and low stagnation pressures, and their carbon-rich nature improved the thermal conductivity, presenting a low steadystate surface temperature. However, a spontaneous jump in the surface temperature at around 1700 °C was observed at high heat fluxes and high stagnation pressures. The jump temperature was lower compared with that reported in previous studies, and was found to increase rapidly to temperatures above 2000 °C. This low-temperature jump phenomenon was associated with the evolution of microstructure during testing, and the underlying mechanism was revealed through the use of thermodynamics analysis.