Effects of high thermal conductivity chopped fibers on ablation behavior of pressureless sintered SiC–ZrC ceramics

As one of the most promising thermal protection materials, the ablation performance of SiC–ZrC ceramics is strongly influenced by thermal conductivity. In this work, the high thermal conductivity mesophase pitch-based carbon fibers (MPCFs) were uniformly added into a mixture of SiC and ZrC powders, which were pressureless sintered to form a MPCFs modified SiC–ZrC ceramics. The relationship between thermal conductivity and MPCFs content was investigated in detail. Both theoretical calculations and experimental results showed that the SiC–ZrC ceramics modified by adding 4.81 vol% MPCFs gained the highest thermal conductivity of 68.10±0.68 W/(m⋅K). The simulation shows that the temperatures at ablation center and backside of the ceramics were 1094 °C and 446 °C, respectively, after plasma ablation at 2300 °C for 20 s. And the actual backside temperature was detected to be 438 °C and that agreed with the simulation results. The high thermal conductivity leads to a lower ablation temperature because the heat is rapidly transferred from the high temperature part to the low region. Due to the low ablation temperature, the 4.81 vol% MPCFs modified SiC–ZrC ceramics exhibited the lowest mass ablation rate (−0.048±0.007 mg/s) and linear ablation rate (−0.715±0.056 μm/s). This research presents a novel insight for designing and fabricating excellent ablation-resistance ultra-high temperature ceramics (UHTCs).