Gd ₂ O ₃ –Al ₂ O ₃ –C Ternary Aerogel/Mullite Fiber Composites for High-Efficiency Synergistic Thermal Insulation and Neutron Shielding

High-performance neutron shielding materials are essential for advanced nuclear energy technologies. However, it remains a challenge to integrate high thermal insulation and neutron shielding capabilities. In this work, mullite fiber mats with good thermal insulation properties and stability were used as the reinforcing skeleton. First, Gd 2 O 3 –Al 2 O 3 binary aerogels were in situ synthesized on the skeleton via the sol–gel and ambient pressure drying method. Subsequently, the organic precursor derivatives in the aerogel were converted into carbon through high-temperature calcination, thereby obtaining Gd 2 O 3 –Al 2 O 3 –C ternary aerogel/mullite fiber composites. Benefiting from the effective suppression of heat transfer by the micronano pores and the high neutron absorption capability of Gd 2 O 3, the as-prepared composites achieved high-efficiency synergistic thermal insulation and neutron shielding. At a thickness of 10 mm, the composites achieved a thermal conductivity of 0.041 W/(m·K) and a thermal neutron shielding efficiency of 88.15%. This provides a novel strategy for the design and development of multifunctional protective materials for thermal insulation and radiation shielding in the field of nuclear energy.