Hierarchical mullite structures and their heat-insulation and compression-resilience properties

Near-net-shaped hierarchical structure-adjustable short mullite fibers/mullite whiskers frameworks (MF/MW frameworks) were prepared by slurry-filtration and heat-treating method. The main structure of MF/MW framework was constituted by lap-jointed mullite fibers. Every single fiber in the framework was densely covered by mullite whiskers which formed through fluorine-catalyzed gas-phase reaction, and the fibers actually served as curved substrates for the mullite whiskers' growth. The lap-jointing points of the fibers were served by movable intersected mullite whiskers. Moreover, the microstructure of the frameworks could be adjusted by tailoring the raw materials mass ratio. The volume densities, the apparent porosities and the thermal conductivities of the MF/MW frameworks in different raw materials mass ratios were 0.459-0.487 g/cm3, 79.7-82.8% and 0.1356-0.1965 W/k m, respectively. The compression-resilience property of the samples was tested under 0.4 MPa at room temperature. The compression ratio and resilience ratio of the MF/MW frameworks in different raw materials mass ratios were 1.63-2.25% and 92.67-98.16%, respectively. The MF/MW frameworks with advanced thermal and mechanical properties were considered to be promising high-temperature heat-insulation material.