Super-insulated, flexible, and high resilient mullite fiber reinforced silica aerogel composites by interfacial modification with nanoscale mullite whisker

Fiber-reinforced aerogel composites are extensively used in thermal insulation and energy-saving fields, while the inherently weak interface combination between fiber and aerogel undermines the effect of fiber reinforcement. To deal with this problem, mullite whiskers were in-situ synthesized on the surface of alumina silicate fiber through a facile and environmentally benign method. The nanoscale mullite whiskers growing on the fiber strengthen the interfacial bonding, thereby improving the mechanical properties of the composite. The alumina silicate fiber/mullite whisker/silica aerogel composites delivered ultrahigh compression stress and modulus of 6.45 MPa and 69.74 MPa at 50% strain, which is 6.14 times and 9.07 times higher than those of bare fiber reinforced silica aerogel. Meanwhile, the composite maintained a high retention rate of maximum stress of 97.8% after being compressed at 30% strain for 200 cycles. Moreover, the composite exhibits an ultralow thermal conductivity of 27.5 mW m-1 K-1 and a low density of 0.26 g cm-3. The strong, resilient, lightweight composite with ultralow thermal conductivity is applicable for heat preservation and energy saving.