Thermal-insulating ceramic fiber aerogels reinforced by fusing knots of overlapping fibers for superelasticity and high compression resistance.

Ceramic fiber aerogels, a unique feature of mesopores and/or macropores formed by overlapping fibers, are currently one of the most appropriate materials for use in high-temperature thermal insulation. However, they usually exhibit incredibly limited mechanical stability derived from random weak links among ceramic fibers, which can lead to disastrous consequences especially under extreme conditions especially. Here, we report a thermal-insulating silica-based ceramic fiber aerogel with excellent compressive strength, modulus of elasticity, and a very high-temperature resistance limit. A unique feature of the obtained ceramic aerogels is that silica based fibers are connected and welded at their common joints together with remain these abundant multiscale porosities, forming multiple fusing knots in contrast to networks from random placement of weakly connected fibers. Synchronously, under shocks from external forces the introduction of the ZrO₂ crystalline phase effectively produces microcrack bifurcations which slow down the crack extension behaviour while maintaining the fracture toughness of the single silica-based ceramic fiber, thereby significantly enhancing the mechanical strength. Consequently, the bulk ceramic aerogels obtained can withstand a maximum elastic strain of more than 80%, and the measured compressive strength is as high as 3.89 × 10⁵ Pa (80% compressive strain). These ceramic aerogels show stable elasticity and structural integrity in an ultra-wide temperature range of -196–1300 °C. Meanwhile, the aerogels have superior mechanical strength, with the energy loss coefficient stabilized at 0.35 after 500 cycles and the lowest thermal conductivity of 0.092 Wm⁻¹ K⁻¹ at 800 ^oC, which is ahead of most of the ceramic aerogels currently available. This work broadens the application of ceramic aerogels and provides new strategies for their development and design. [ABSTRACT FROM AUTHOR]