"Face Bridging" of Silica Nanofibers: Enabling Monolithic Aerogels together with High Specific Strength and Low Thermal Conductivity.

Against the rising demand for advanced materials in high-temperature and high-tech applications, it is urgent to develop ceramic fiber aerogels with high specific strength and low thermal conductivity. Herein, we adopt an in situ polycondensation method to induce confined growth of a uniform face-connected network within partial pores of nanofiber frameworks, and successfully synthesize face-bridging silica aerogels (FBSAs). Relying on the interlocked face-bridging microstructure, the as-prepared monolithic aerogels gain improved structural robustness, high specific strength, and reduced thermal conductivity simultaneously. Versus conventional point-crosslinked silica aerogels, FBSAs exhibit greatly enhanced mechanical properties: a compressive strength of 318 kPa at 80% compression strain, tensile strength of 120 kPa, and flexural strength of 390.8 kPa. With an ultralow density ranging from 35 to 50 mg cm-3, the material achieves a specific strength of 6.36 MPa cm3 g-1, which is two to three times higher than that of typical ceramic fiber aerogels. Moreover, the aerogel delivers a room-temperature thermal conductivity of 0.028 W m-1 K-1, comparable to conventional silica aerogels. It maintains stable thermal insulation between -196°C and 1100°C, and can withstand short-term exposure at 1300°C. This confined growth strategy provides a reliable route to fabricate high-performance monolithic silica aerogels.