Ultralow Thermal Conductivity and Excellent Gamma-Radiation Resistance of a Novel Boron-Doped Silica Aerogel for Thermal Protection in Nuclear Applications

Silica (SiO₂) aerogels have been considered as promising materials for thermal insulation. However, SiO₂ aerogels’ poor high-temperature stabilities, mechanical properties, and radiation resistances mean that their application as thermal insulation materials in nuclear power is greatly limited. In this study, novel boron (B)-doped SiO₂ aerogels were prepared by a sol-gel process, and the aerogel with a Si/B molar ratio of 1:0.15 was found to exhibit excellent radiation resistance and low thermal conductivity. Specifically, investigations of the microstructure and performance changes of the B-free SiO₂ aerogel and B-doped SiO₂ aerogels after exposure to gamma (γ)-radiation revealed that the latter were more resistant than the former to γ-radiation. However, B-doped SiO₂ aerogels containing low concentrations of B³⁺ were damaged by high cumulative doses of γ-radiation, whereas those containing high concentrations of B³⁺ tended to undergo oxidation and thus contained boron trioxide. A B-doped SiO₂ aerogel with a Si/B molar ratio of 1.00:0.15 exhibited excellent structural stability and γ-radiation resistance, even when exposed to a high cumulative dose of γ-radiation (1700 kGy). Moreover, this B-doped SiO₂ aerogel exhibited desirable thermal conductivity (0.0147 W/m K at 25 °C), hydrophobicity, and high temperature resistance (3 μm infrared transmittance of 39.52%), even after γ-irradiation. In summary, these findings suggest that B-doped SiO₂ aerogels warrant exploration for use as thermal insulation materials for pipelines in nuclear power plants. It provides valuable insights for the study of the radiation effects of aerogel materials in nuclear power applications.