Multi-Metal Phenolic Network Engineered Low Density Polymeric Ablator for Thermal Protection and Insulation up to 2900K.

Abstract

Planetary-entry and sample-return missions demand thermal protection materials that simultaneously minimize mass, suppress recession, and withstand prolonged exposure to ultrahigh-temperature oxidative environments. Here, we report a metal-phenolic-network (MPN) engineered low-density-ablator that resolves this longstanding trade-off through molecularly programmable multimetal ceramization. The material is constructed by controlled ligand exchange between a quasi-linear Ti/Zr/Hf multimetal polymer and phenolic ligands, followed by polymerization into a nanoporous aerogel-like-matrix with low density, low thermal conductivity, and scalable processability. The molecular-level dispersion of multimetal species governs the in situ evolution of hierarchical ceramic architectures during extreme heating: the surface transforms into a dense interpenetrating oxide protection layer, in which (Hf, Zr)O form a rigid skeleton while (Ti, Si)O fill the intergranular space to suppress oxygen penetration and outward mass transport; meanwhile, the interior develops a mass-fractal carbon-ceramic network that disrupts heat-flux propagation. The composite exhibits near-zero recession at ultrahigh temperatures, with linear ablation rates of 0.0017 mm s^-1 at 2800 K and 0.0031 mm s^-1 at 2900 K, while sustaining 2500 K for 1500 s with a back-temperature-rise of only 369 K. This work establishes an MPN-based materials platform for lightweight thermal protection systems that integrate ultrahigh-temperature stability, oxidation resistance, and effective thermal insulation.