Synthesis of flexible ThO2 nanofibers with high-temperature resistance by designing the precursor structure

Thorium dioxide (ThO₂) fibers exhibit exceptional structural stability, low density and superior flexibility, coupled with a remarkably high melting point, positioning them as promising candidates for thermal protection applications. Additionally, their commendable secondary processing characteristics enable the development of diverse composite materials when integrated with other materials, significantly broadening the potential utilization of ThO₂ materials and thorium resources in industrial fields. In this work, the ThO₂ fiber was fabricated by the sol–gel precursor method, and the precursor with good spinnability and excellent stability was synthesized for the first time. The ThO₂ fiber with a mean diameter of 868 nm is both highly flexible and strong (max. tensile strength 2.21 MPa), capable of bending freely across a wide temperature range from − 196 °C (in liquid nitrogen) to 1200 °C. Meanwhile, it exhibits excellent temperature stability and heat insulation properties. The ThO₂ nanofiber membranes with layered structure have low density (32–37 mg·cm⁻³), low thermal conductivity (27.3–30.1 mW·m⁻¹·K⁻¹@25 °C). The ThO₂ nanofiber membranes with 15 mm thickness can reduce the temperature from 1200 to 282 °C and maintain a high aspect ratio and bendability after 1200 °C@90 min. The results show that the ThO₂ fiber can be used as a new kind of high-temperature resistant material.