Work

Low‐Temperature Construction of Self‑Strengthening, Reusable, Ultralight Mullite Fiber Composites with Fish‑Scale‑Like Adaptive Boron‑Rich Layers

Year: 2026

Type: article

Abstract: ABSTRACT Reusable thermal protection materials are prone to structural damage accumulation and performance degradation under cyclic thermomechanical loading. Overcoming the conventional “cycling equals damage” paradigm is a critical challenge for long‐term service. Here, we exploit low‐temperature ceramization of a boron‐rich precursor at 600°C to in situ construct a fish‐scale‐like adaptive ceramic reinforcement layer (ACRL) on mullite fiber surfaces and junctions. The composite exhibits remarkable thermomechanical‐cycling‐induced strengthening (TMCIS) during cyclic compression at 420°C, with the average modulus nearly tripling after 100 cycles. In situ SEM reveals that thermomechanical coupling drives local displacement of adjacent fiber segments and node reconstruction; the ACRL of viscous softening acts as a dynamic “high‐temperature solder” that bridges fiber contacts and reconfigures the load‐transfer network, enabling a service‐induced strengthening mechanism. After 50 cycles (totaling 25 h) at 420°C, the mass loss per cycle is only 0.07%. Furthermore, the material simultaneously achieves a low density (0.29–0.35 g/cm 3 ), high compressive strength (1.60 MPa), and low thermal conductivity (0.062 W/(m·K)), realizing a synergy of lightweight, load‐bearing, and thermal insulation. This work converts cyclic loading from a damage source into a driving force for structural strengthening, establishing a new adaptive paradigm for long‐life reusable thermal protection materials.

Source: Advanced Functional Materials

DOI: 10.1002/adfm.79403