Microstructure of mullite fiber-based hierarchical structures adjusted by Al/Si mole ratio of the raw material powders

Mullite fiber-based hierarchical structures were prepared by mixed slurry filtration and heat-treating method. Mullite fibers׳ framework served as the main structure of the material, and mullite fibers acted as curved substrates for the secondary structures׳ growth. The secondary structures formed on the fibers through fluorine-catalyzed gas phase reaction, and their morphology could be adjusted by tailoring (Al/Si)mol of the raw material powders (mixed AlF3–SiO2 powders). Inter-locked corundum hexagon plates as secondary structures grew on the mullite fibers when (Al/Si)mol of the raw material powders was 3/0. Mullite whiskers became the only secondary structures on the fibers when (Al/Si)mol of the raw material powders was 3/2–3/3. The inserted corundum plates or the intersected mullite whiskers acted as the unfixed lap-jointing points of the mullite fibers in the frameworks. The compression–resilience performance of the frameworks was tested at 1 MPa, and the resilience ratio of the frameworks was higher than 90%.