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Fibers crystallize and become brittle at high temperatures for a long time, so the surface coating must maintain long-lasting emission performance, which requires superior antioxidant properties of the high-emissivity fillers. To improve the radiation performance of the coating and the tensile strength of the fiber fabric, a double-layer coating with high emissivity was prepared on the surface of flexible aluminum silicate fiber fabric (ASFF) using MoSi2 and SiC as emissive agents. The incorporation of borosilicate glass into the outer coating during high-temperature oxidation of ZrB2 results in superior encapsulation of emitter particles, effectively filling the pores of the coating and significantly reducing the oxidation rate of MoSi2 and SiC. Furthermore, the addition of an intermediate ZrO2 layer enhances the fiber bundle's toughness. The obtained double-coated ASFF exhibits an exceptionally high tensile strength of 57.6 MPa and a high bond strength of 156.2 kPa. After being subjected to a 3 h heating process, the emissivity exhibits a minimal decrease of only 0.032, while still maintaining a high value above 0.9. The thermal insulation composites, consisting of a flexible ASFF matrix and a ZrB2-modified double-layer coating, exhibit significant potential for broad applications in the field of thermal protection. [ABSTRACT FROM AUTHOR]

To improve the oxidation inhibition of TaSi 2 -based high-emissivity coatings at high temperatures, TaSi 2 –SiC coating modified by SiB 6 was prepared on the surface of alumina fibre fabrics. The effects of the SiB 6 content on the surface appearance and emissivity of the coating were investigated, and the mechanical properties of the coated fabrics were compared. When the SiB 6 content in the coating was 2.5%, the borosilicate glass liquid phase generated by SiB 6 oxidation effectively prevented the oxidation of TaSi 2. The bond strength between the coatings and fibre fabric was 207 kPa after calcination at 1200 °C, which was 39% higher than that of the coated fabric without SiB 6. The emissivity of the TaSi 2 –SiC coating, modified by a SiB 6 content of 2.5%, reached above 0.92 after calcination at 1200 °C for 5 h. Therefore, the TaSi 2 –SiC high-emissivity coating modified by SiB 6 has good application prospects in the field of thermal protection. [ABSTRACT FROM AUTHOR]

As a critical structure of thermal protection systems, flexible fibre insulation felts are widely used on the leeward surface of spacecrafts. To enhance the thermal resistance of flexible fibre felts, SiC w -ZrO 2 coatings with different SiC whisker (SiC w) contents were fabricated on the surface of a high-silica-fibre fabric (HSFF) by employing a sol-gel method combined with a spraying route. The introduction of SiC w having a length of 10–50 μm effectively improved the coating integrity. After calcination at 1000 °C for 1 h, the SiC w -ZrO 2 coating containing 8 wt% SiC w did not damage the tensile strength and flexibility of the fibre fabric, and the interfacial bonding strength between the coating and HSFF reached 0.40 MPa, benefitting from the whisker toughening mechanism. The SiC w -ZrO 2 coating with a high emissivity of 0.96 in the 2–14 μm wavelength range reduced the surface temperature of the flexible insulation felt by approximately 300 °C when a butane torch was applied at above 1300 °C. [ABSTRACT FROM AUTHOR]

High emissivity coatings on hypersonic vehicle surfaces dissipate heat by emitting thermal radiation. While the difficulty of increasing emissivity limits the performance of coatings to improve heat-dissipation of the thermal insulation felt. Herein, a novel high-reflectivity and high-emissivity integrated double-layer coating was developed to enhance the thermal insulation performance of the alumina fiber fabric. The coating comprised of TiO 2 @SiO 2 (T@S) as reflective agent and ZrO 2 /SiC w (ZSC) as emittance agents, was applied on the surface of alumina fiber fabric (AFF). The reflecting effect of radiation heat from the high reflective agent enhanced the thermal insulation properties of the double-layer coating. In the wavelength range of 0.4–2.5 μm, the average emissivity of the ZSC coating was 0.83 and the average reflectivity of the T@S coating was 0.63. With continuous heating at 1400 °C for 10 min with a butane torch, the temperature on the backside of the T@S–ZSC-coated AFF remained relatively stable at 225 °C, which is notably decreased by 80 °C compared to that of the single-layer ZSC-coated AFF. The tensile strength of AFF with T@S–ZSC coating reached 35 MPa after being heat treated at 1200 °C. Moreover, the bonding strength between the coating and the AFF substrate was measured to be 0.15 MPa. The double-layer coating with high emissivity and reflectivity, along with a flexible AFF substrate, offers a promising solution for addressing the challenging of surface heat-dissipation in hypersonic vehicles. [ABSTRACT FROM AUTHOR]

Aluminum silicate fiber fabric (ASFF) has been widely used in the outer surface of flexible insulation felt on the leeward side of aerospace vehicle. In order to improve the temperature resistance of ASFF, a kind of SiC–ZrC composite coating was prepared on the surface of fiber fabric via spraying method with SiC as emittance agent and ZrC as additive. The surface morphology and mechanical properties of the coating were studied. Compared with the single-component SiC coating, the composite coating could effectively avoid coating spalling and improve the surface integrity at high temperature. After thermal treatment at 1100 °C for 2 h, the interface bond strength of the composite coating/substrate was 52.41% higher than that of SiC coating/substrate. The tensile strength of fiber fabric with SiC–ZrC composite coating could reach 91.75 MPa, which was 101.76% higher than that of raw ASFF. Therefore, the SiC–ZrC coating could greatly improve the temperature resistance of ASFF, and has an attractive application prospect in the field of thermal protection system. [ABSTRACT FROM AUTHOR]

To prepare a coating with a high emissivity and low solar absorption ratio on the surface of aluminum silicate fiber cloth, the sol-gel method was used with silica sol as a binder. In this study, the effects of two white fillers, titanium oxide and zirconia, on the substrate and radiation properties of coatings were compared after heat treatment at 800–1200 °C. The ZrO 2 -based coating had good stability after heat treatment at 800–1200 °C, and maintained its white color, exhibiting solar absorption ratio of approximately 0.14 and emissivity of 0.84. ZrO 2 -based coatings prevented harmful cracking, as observed for the TiO 2 -based coatings after heat treatment, because of the ZrO 2 phase transformation. The ZrO 2 -based coating did not have strong bonding with the substrate, and the substrate strength was improved by maintaining a weak bonding interface. Compared with the TiO 2 -based coatings, which exhibit reduced substrate strength above 1000 °C, the ZrO 2 -based coating was more suitable for the surface of flexible fiber cloths as a temperature-resistant coating with good development prospects. [ABSTRACT FROM AUTHOR]

To improve the oxidation protective ability of carbon–bonded carbon fiber (CBCF) composites. A multilayer coating containing ZrB 2 , MoSi 2 , SiCw and borosilicate glass was prepared on ZrB 2 -modified carbon–bonded carbon fiber composites (CBCFs/ZrB 2 ) by a trace oxygen sintering method and a pre-oxidation process. The microstructure, surface emissivity and ablation resistance of the multilayer coating were studied. The coating containing dense surface layer and porous inner layer was obtained. The total emissivity of the coating in the wavelength range of 6–16 μm at 300, 500 and 800 °C was 0.72, 0.73 and 0.78, respectively. The prepared multilayer coating exhibited excellent ablation resistance for 1000 s under simulated atmospheric re-entry conditions by high frequency plasma wind tunnel test with a heat flux of 131.8 W/cm 2 and stagnation pressure of 2.7 KPa. [ABSTRACT FROM AUTHOR]