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 & PLUSMN;0.68 W/(m & BULL;K). The simulation shows that the temperatures at ablation center and backside of the ceramics were 1094 degrees C and 446 degrees C, respectively, after plasma ablation at 2300 degrees C for 20 s. And the actual backside temperature was detected to be 438 degrees 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 & PLUSMN;0.007 mg/s) and linear ablation rate (-0.715 & PLUSMN;0.056 & mu;m/s). This research presents a novel insight for designing and fabricating excellent ablation-resistance ultra-high temperature ce-ramics (UHTCs).