Nested-Structure ZrO2–MoSi2–SiC High-Emissivity Coating on the Flexible Fiber Fabric with Enhanced Bonding Strength and Thermal Insulation Performance

Research on high-emissivity coatings for flexible thermal insulation felts used in aerospace vehicles has achieved substantial progress. However, the bonding strength of these systems remains a critical challenge that necessitates further improvement. Herein, a nested-structure high-emissivity coating, comprising a Zr precursor-based shell integrated with an Al2O3–MoSi2–SiC (AMS) layer, is applied on alumina fiber fabric (AFF). The nested-structure Zr precursor-based shell not only improves interfacial properties through structural design but also effectively enhances thermal insulation by facilitating multiple reflections and absorptions of infrared radiation. The Zr precursor shell penetrates into the interior of the fiber fabric, providing direct thermal protection to the fiber matrix. Simultaneously, at high temperatures, it reacts with the surface high-emissivity coating to form a ZrSiO4-modified mechanical interlocking structure, thereby significantly enhancing the bonding strength. The bonding strength between the nested-structure precursor composite coating (NPCC) and the AFF substrate was measured to be 0.34 MPa at 1300 °C, showing an 80% enhancement compared to that of the single-layer AMS coating. Upon continuous heating at 1445 °C for 10 min using a butane torch, the temperature on the backside of the NPCC-coated AFF remained relatively stable at 212 °C, which is notably decreased by 50 °C compared to that of the single-layer AMS-coated AFF. In the wavelength range of 3–8 μm, the average emissivity of the coating was 0.91. The NPCC significantly enhances both the bonding strength and thermal insulation performance of AFF, offering promising prospects for applications in thermal protection systems.