Synergistic gradient CTE matching and viscoelastic interfacial engineering for high-fidelity in situ thermometry on ceramic matrix composites

In situ temperature monitoring of ceramic matrix composites (CMCs) under extreme high-temperature conditions is critical for thermal safety management. However, existing thin-film sensors suffer from cracking and signal drift in their sensitive layers due to the spatial heterogeneity of the CMC matrix’s coefficient of thermal expansion and high-temperature interfacial degradation. Here, a multiscale synergistic regulation strategy is proposed. First, the distribution characteristics of CMC fiber volume fraction are quantified using a Weibull random field model, guiding the design of a TiB₂/B₂O₃ gradient transition layer. Leveraging the viscoelastic transition of B₂O₃ within the temperature range 450–1860 ℃, dynamic thermal stress dissipation is achieved, reducing interfacial shear stress by 62%. A 3D interpenetrating thermal expansion matching layer is constructed using micro/nano SiC composite powders, enhancing interfacial bonding strength to 19.7 MPa. An Al₂O₃ insulating layer is subsequently fabricated to improve electrical insulation. Finally, an indium tin oxide/In₂O₃ thermocouple-sensitive layer is deposited via Weissenberg direct writing, utilizing a polymer-derived ceramic solution as the powder solvent. The resulting sensor exhibits exceptional performance in static air at 1100 ℃: thermoelectric response linearity (R² > 0.999), a Seebeck coefficient of 168.65 μV/℃, and a low thermoelectric potential drift rate of 1.27%/h over 8 h. This study provides a theoretical foundation and technological prototype for high-precision health monitoring of hot-section components in aeroengines.