Novel biphasic high-entropy ceramic aerogels and their fiber composites with low thermal conductivity, high thermal stability and significant thermal insulation property

A novel biphasic high-entropy (Y_0.2Ho_0.2Tm_0.2Yb_0.2Lu_0.2)₂SiO₅/(Y_0.2Ho_0.2Tm_0.2Yb_0.2Lu_0.2)₂Zr₂O₇ ceramic aerogel (BP-HEZSA) was prepared using formamide/sol-gel, supercritical CO₂ drying and combined with a heat treatment process. The results indicate that BP-HEZSA exhibits a biphasic high-entropy structure at 1200 °C, and it maintained its stability at 1400 °C while demonstrating a homogeneous distribution of elements. BP-HEZSA exhibited nanoscale fine grains (with a size range of 18.82 nm to 27.62 nm), high BET specific surface area (16.24 m²·g⁻¹), and good pore structure, all of which were controlled by the thermal treatment temperature. BP-HEZSA had low room temperature thermal conductivity and high structural and phase thermal stability at high temperatures. Furthermore, the applicability of the aerogel was improved by compounding with aluminosilicate fibers. The composites exhibited low density and low thermal conductivities (0.04–0.14 W·m⁻¹K⁻¹). Butane blowtorch testing confirmed superior thermal insulation in the composites, meeting demands for high-temperature resistance in the advanced nanostructured materials.