Long Zhang,Shan He,Chaopeng Zhao,Huadong Fu,Yan Qin
Aerodynamic heating threatens hypersonic vehicles, making lightweight, flexible thermal protection coatings essential. This paper designs and prepares a multifunctional B 4 C-LaB 6 /silicone rubber high-emissivity ceramicizable thermal protection coating. By incorporating chopped high-silica silica fibers and aramid fibers as ablation-resistant fillers into the silicone rubber matrix, and combining them with the high-emissivity functional components B 4 C and LaB 6 , a coating material with both ablation protection and radiative heat dissipation capabilities was achieved. Research indicates that the synergistic effect of B 4 C-LaB 6 significantly enhances the thermal stability and thermal insulation performance of the composite coating: At a B 4 C:LaB 6 ratio of 20:20, the coating's mass retention rate at 1000°C increased from 43.45% to 80.68%, with an average infrared emissivity reaching 0.947. Concurrently, the coating exhibited lower linear ablation rates and a denser ceramic layer structure. This research offers new insights for multifunctional silicone rubber thermal protection coatings, showing potential for hypersonic vehicles. Highlights The B 4 C-LaB 6 system significantly improves the thermal stability of silicone rubber composites. The B 4 C-LaB 6 system densifies the ceramic layer during high-temperature ablation. The B 4 C-LaB 6 system achieves high near-infrared emissivity. The B 4 C-LaB 6 /silicone rubber coating demonstrates a multifunctional design for thermal protection materials.
In this work, two ceramizable phenolic adhesives were prepared using ZrSi 2 particles or ZrSi 2 /B 4 C mix particles as the inorganic fillers. The thermal stability, bonding strength , microstructure and phase composition of the adhesives were investigated by TGA , shear strength of Al 2 O 3 joints, SEM, EDS , XRD and XPS . The results show that these two adhesives have different bonding performances and ceramicization evolutions above 600 °C in air due to the addition of the second phase particles B 4 C. The bonding strength of ZrSi 2 /B 4 C modified phenolic adhesive after treatment at 1200 ℃ can be as high as 36.6 MPa, while the bonding strength of ZrSi 2 modified phenolic adhesive under the same conditions is only 17.5 MPa. B 4 C undergoes oxidation reaction before ZrSi 2 , and the oxidation product B 2 O 3 liquid phase not only reacts with ZrSi 2 to form oxidation-resistant ZrB 2 , but also can dissolve the high temperatures defects of the adhesive and chemically bond with the Al 2 O 3 substrates at the interface.
Liu Yang,Deng Zongyi,Zhang Wei,Jiang Guoqin,Cao Wenjing,Huang Zhixiong,Shi Minxian,Li Jian
Lightweight ablative materials are commonly utilized as thermal protection materials for hypersonic vehicles. Ceramizable phenolic aerogel/carbon fiber (PA/CF) composites modified with TiB 2 and B 4 C were fabricated, which had the characteristics of lightweight, high strength, and low thermal conductivity. The acid-catalyzed phenol-aldehyde polymerization reaction was used to significantly shorten the gelation time, which facilitated the uniform distribution of ceramic fillers. The oxygen-consuming, oxygen-blocking, and carbon-fixing synergistic effects of TiB 2 and B 4 C high-temperature ceramic reactions, as well as the multiphase ceramic structure (C-B 2 O 3 -TiO 2 -TiC) formed, conferred excellent thermal stability (the residual weight of 58.8% at 1200 °C), oxidation resistance (the residual strength of 3.44 MPa after static ablation), and ablation resistance (the linear and mass ablation rates as low as 0.045 mm/s and 0.0115 g/s) on the composites. The lightweight, high-strength materials with anti-thermal insulation properties demonstrate significant competitiveness and application potential in the field of thermal protection.
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