High-Emissivity M2+@TiO2/High-Entropy Coating on Flexible Aluminosilicate Fiber Fabric for Enhanced Bonding Strength and Thermal Insulation Performance

High-emissivity coatings on flexible fibrous fabrics are promising thermal-insulation materials for thermal protection systems in hypersonic vehicles. However, the interfacial bonding strength between the high-emissivity coating and the flexible fibrous substrate remains a critical challenge. A high-emissivity double-layer TiO2 interlayer modified by metal ions (Mg2+, Co2+, Ni2+, and Zn2+) with high-entropy (M2+@TiO2-HE) coating was developed on an aluminosilicate fiber fabric. The interlayer of the M2+@TiO2-HE coating not only enhances bonding strength through mechanical interlocking but also improves thermal insulation performance by acting as an infrared reflective layer. The bonding strength between the M2+@TiO2-HE coating and the ASFF substrate showed an 183% enhancement compared to that of the single-layer high-emissivity high-entropy coating. Under one-sided heating at 1400 °C, the backside temperature of the coated ASFF stabilizes at 330 °C, which is approximately 50 °C lower than that of the sample with the single-layer high-emissivity high-entropy coating. In the wavelength range of 0.3–2.0 μm, the average reflectivity of the M2+@TiO2 coating was 0.70, and in the wavelength range of 1–14 μm, the average emissivity of the M2+@TiO2-HE coating was 0.89. The M2+@TiO2-HE coating with high emissivity and reflectivity enhances both the bonding strength and thermal insulation performance of ASFF, showing its potential for applications in aerospace thermal protection systems.