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

A near-net-shape ZrO2-mullite fibrous ceramic has been successfully fabricated by a novel aqueous gel-casting using the hydratable alumina (rho-Al2O3), 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 Y2O3 additive on the improvement of the comprehensive performance were investigated and discussed. The results showed that the hydrates from rho-Al2O3 could react with zircon to form the binder to combine the mullite fibers together into a bird nest structure, and mullite strips and ZrO2 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 Y2O3 additive could remarkably increase the compressive strength to 18.8 MPa by promoting the formation of YSZ and Y-Al-Si-O glass phase.