Structure Engineering of Quartz Fiber Preforms Enabling ZrO2-SiO2 aerogel Composites Light-weight, Mechanical Robustness and Ultra-low Thermal Conductivity

The configurations of the embedded fibers within aerogel composites influence the mechanical and thermal performances significantly, rendering the composites suitable for harsh conditions. With this regard, quartz fiber preforms were designed by carding quartz fibers wool, then layer-by-layer stacking in a space-confined mold, where the fibers were pre-compressed, resulting in spring-back behavior that opposes the direction of compression. ZrO 2 -SiO 2 aerogel precursor was infiltrated into the fiber preform to form quartz fiber reinforced ZrO 2 -SiO 2 aerogel (QFZSA) composites with the assistance of vacuum impregnation, sol-gel chemistry and supercritical drying. Thanks to the spring back effect of the fiber preform, the QFZSA composite exhibits exceptional out-plane mechanical strengths; compressive and bending strengths both reached nearly 1 MPa. In addition, the layer stacking structure of the fiber preforms efficiently suppressed conductive heat transfer as well as radiative heat transfer, endowing ultra-low thermal conductivities of 0.036 W m -1 K -1 and 0.070 W m -1 K -1 at 1000 ºC and 1200 ºC, respectively. The densities of the QFZSA composites with varying fiber volume fractions were in the range of 0.16-0.24 g cm -3 . X-ray computed tomography provided comprehensive characterization of the QFZSA composites, including fiber configuration, fiber volume fraction, interfacial area, and defect volume fraction, among others, which are important parameters governing composite properties. The as-prepared QFZSA composites are capable of finding applications in many leading-edge thermal protection fields.