Fibrous ZrO2-mullite porous ceramics fabricated by a hydratable alumina based aqueous gel-casting process

Abstract A near-net-shape ZrO 2 -mullite fibrous ceramic has been successfully fabricated by a novel aqueous gel-casting using the hydratable alumina (ρ-Al 2 O 3 ), zircon and mullite fibers as the raw materials. The phase compositions, microstructure, sintering behaviors and properties of the as-prepared porous ceramic were observed and analyzed by XRD, FESEM with EDS, XRT and other testing methods. The effects of mullite fiber content and Y 2 O 3 additive on the improvement of the comprehensive performance were investigated and discussed. The results showed that the hydrates from ρ-Al 2 O 3 could react with zircon to form the binder to combine the mullite fibers together into a bird nest structure, and mullite strips and ZrO 2 grains wrapped on the fibers decreased with increasing the contents of fibers. The as-prepared porous ceramic had the increase of apparent porosity and the decrease of shrinkage and bulk density as the amounts of fibers increased. And the low thermal conductivity (0.752–0.854 W(m·K) −1 ) and high compressive strength (10.4–14.4 MPa) played an important role on its wide applications. In addition, the introduction of Y 2 O 3 additive could remarkably increase the compressive strength to 18.8 MPa by promoting the formation of YSZ and Y-Al-Si-O glass phase.