Ablation behavior, microstructure, phase evolution and in situ ceramization mechanism of ZrC-LaB6 modified carbon fiber/phenolic resin ceramizable composite

Carbon fiber/phenolic resin composite (CF/Ph) has drawn great interest in thermal protection for its characteristics of high specific strength and easy fabrication. However, oxidation failure limits further application of CF/Ph in hostile environments. Herein, a novel carbon fiber/phenolic resin ceramizable composite modified with ZrC and LaB6 was reported. The synergistic effects between ZrC and LaB6 on high-temperature thermal degradation behavior, oxidative corrosion and ablation resistance were systematically studied based on thermal analysis and oxyacetylene ablation experiment of the resulting ceramizable composite as well as microstructure evolution, phase evolution, and thermodynamic calculation analysis of the ablated surface. The resulting ceramizable composite exhibited excellent oxidative corrosion and ablation resistance, with the residue yield at 1500 °C as high as 32.8 % and the linear ablation rate at 4.3 MW/m2 for 30 s as low as -0.00231 mm/s, respectively. Further, the ablation mechanisms were revealed. Dense B-C-O-Zr-La ceramic layers with a mosaic structure, which acted as efficient thermal protection barriers, were constructed in situ, and significantly reduced corrosion to carbon. Moreover, an intense endothermic effect during the carbothermal reaction between ZrO2, B2O3 and PyC led to an abnormally better insulation capacity.