Elevated temperature resistance of SiC-carbon/phenolic nanocomposites reinforced with zirconium diboride nanofibers

Carbon fiber-reinforced composites with matrices containing ultra-high temperature ceramics show excellent potential as high ablation-resistant materials. In this study, two non-oxide nanostructures, ZrB₂ nanofibers and SiC nanoparticles, as reinforcement phases were utilized to develop the carbon/phenolic-ZrB₂-SiC (C/Ph-ZS) nanocomposite for the first time. Thermogravimetry analysis illustrated that the residue yield of C/Ph composite at high temperatures was increased by the introduction of above-mentioned nanostructure ceramics. The addition of 7 wt% of ZrB₂/SiC nanoadditives homogeneously in a C/Ph composite resulted in an enhancement of the room temperature thermal diffusivity, from 0.00622 to 0.00728 cm²/s. The incorporation of 4–7 wt% of ZrB₂/SiC nanofillers in C/Ph composites leads to a reinforced material with about 73% increasing of Shore D hardness. The modified thermal behavior of prepared nanocomposites was examined using oxyacetylene torch at 2500℃ for 160 s. It suggested that the C/Ph-ZS7% nanocomposites with lower density may drastically contribute to meliorate the thermal insulation and ablative properties. The linear ablation rates of C/Ph composites were decreased after adding 7 wt% ZrB₂/SiC nanofillers by 18%. The formation of a dense and uniform SiO₂ and ZrO₂ layer on the ablated surface of C/Ph-ZS nanocomposites could function as an effective oxygen barrier which greatly reduced the ablation rates of the nanocomposites because of the evaporation at elevated temperature, which absorbs heat from the flame and reduces the erosive attack to C/Ph. The ablated C/Ph-ZS nanocomposite with complicated cross-section structure displayed four dense oxidized, porous surface, transient and matrix regions.