In Situ Nanoscale Rapid Phase Stabilization Enables Zr-Phenolic Aerogel Composites with Excellent Ablation Resistance in Extreme Thermal Environments

Element-hybrid phenolic aerogel composites are often utilized as lightweight thermal protection materials for aerospace craft. Zr-phenolic (Zr-PR) aerogels have been extensively studied due to their exceptional high-temperature resistance. However, the phase transformation of ZrO2, the pyrolysis product of Zr-PR, caused the volume changes and internal stresses, greatly limiting the application of Zr-PR. In this work, a small amount of nano-Y2O3 particles was directly doped into the Zr-PR aerogel composites to form the nanoscale mosaic structure. This aerogel composite exhibited properties of low density (0.51 g/cm3) and low thermal conductivity (<0.151 W/(m K)); moreover, it showed a significant improvement in oxidative ablation resistance with a 33% reduction in the linear ablation rate. The research indicated that the doping of nano-Y2O3 effectively addressed the adverse effects associated with ZrO2 phase transformation by in situ rapidly forming (<60s) the dense yttria-stabilized zirconia (YSZ) thermal barrier layer on the ablation surface, which significantly delayed the thermal-oxidative ablation of the composites. Additionally, the pyrolytic carbon (PyC) on the ablation surface can form abundant multilayered graphene structures due to the catalytic graphitization effect produced by the solid-solution reaction of YSZ, which further enhanced the oxidation resistance. This work provides a simple and efficient approach to improve the ablation performance of Zr-PR aerogel composites, broadening their application in extreme thermal environments.