High entropy silicate ceramic aerogels with excellent thermal stability up to 1600 °C and their fiber-reinforced composites for high temperature insulation

Ceramic aerogels show promising applications in extreme environments such as aerospace, but are severely limited by the sintering-prone nature of nano-units at high temperatures. However, they typically exhibit inadequate dimensional stability when exposed to high-temperature atmospheres, which can result in the deterioration of macroscopic characteristics, eventually restricting their extreme-ambient conditions. Here, (YYbErDyGd)₂SiO₅ ceramic aerogel (ESA) was prepared at 1050 ℃ by introducing high entropy into ceramic aerogel, thereby enhancing its high-temperature thermal stability by using high entropy effect. ESA was exposed to a temperature of 1600 ℃ for 2 h without undergoing sintering. In addition, different fiber-reinforced ceramic aerogel composites are also explored, with a thermal conductivity of only 0.032 W/(m·K) at room temperature and 0.108 W/(m·K) at high temperatures at 1000 °C. These composites demonstrate without any visible damage or deformation to extreme conditions across a substantial temperature range (-196 to 1300 °C), a property that is paramount for applications in extreme environments. At 1100-1300 °C, after 2 h of calcination, the composites exhibit a shrinkage rate of only 0.25%. After 600 s of butane torch ablation at 1300 °C, the back temperature is only 110 °C. Meanwhile, under 60% compression deformation, its maximum compression strength is 0.386 MPa. Even after 20 high-temperature thermal cycles (each at 1300 °C for 2 h), the sample maintains a low thermal conductivity of 0.043 W/(m·K) and a compressive strength of 0.259 MPa. This work will provide a new perspective for exploring the limits of strength and thermal properties of ceramic composites in the field of high-temperature insulation, particularly in extreme conditions.