Flexible, high strength and low thermal conductivity of a novel high entropy oxide ceramic fiber membranes

Abstract

Single-component oxide fibers encounter various issues, including grain transition growth and mechanical property degradation at high temperatures, which restrict their potential usage for high-temperature applications. The unique properties of high-entropy materials, including lattice distortion, sluggish diffusion, and cocktail effects, can effectively maintain small grains and excellent mechanical properties even in extreme conditions. Therefore, developing high-entropy oxide fibers provides a dependable solution to address the issues associated with single-component fibers. This paper successfully obtained the (Zr0.2Hf0.2Ti0.2Gd0.2Y0.2)O2-δ (ZHTGY) high-entropy oxide fibers by commencing from molecular design. Compared to other high entropy oxide materials, ZHTGY fibers exhibit a low crystallization temperature of 700 °C and exceptional high-temperature stability with no phase changes observed from RT to 1500 °C. In addition, the ZHTGY fiber membranes exhibit a density of merely 33 mg·cm−3, a tensile strength of 2.73 MPa@1000 °C, excellent flexibility, knot-free and fold-free properties, as well as the ability to bend freely even in environments with butane flame or liquid nitrogen. The ZHTGY fiber membranes have excellent thermal insulation properties due to their ultra-low density and high-temperature structural stability. With a thermal conductivity of only 25.7 mW·m−1K−1, an 8 mm thick sample laminated with these fiber membranes can reduce the temperature of a 1370 °C heat source to just 320 °C. The fiber membranes maintain good flexibility and strength even after heat treatment at 1200 °C for 50 h and 1400 °C for 180 s. This study provides a novel approach for preparing high-entropy oxidation fibers, thereby enabling the development of lightweight high-temperature thermal protection materials.