Fabrication of porous Al2O3-based ceramics using ball-shaped powders by preceramic polymer process in N2 atmosphere

Porous Al2O3-based ceramics were successfully fabricated using ball-shaped powders by preceramic polymer process in N2 atmosphere. These results showed that the amorphous Si-O-C ceramics were formed on the surface of ball-shaped Al2O3 particles by the pyrolysis of the silicone resin during sintering in N2 atmosphere, which played a role in connecting the Al2O3 particles by forming the sintering necks. When the sintering temperatures increased from 1100 °C to 1600 °C, the formed Si-O-C ceramics still existed in the amorphous state and had no crystallization. Interestingly, the amorphous β-SiC formed at 1300 °C and its amount gradually increased with further increasing temperatures. The linear shrinkage rate of the samples varied from 0.49% to 0.73% and the weight loss rate increased from 2.01% to 10.77%. The apparent porosity remarkably varied with the range of 24.9% and 34.5%, as the bulk-density varied from 2.66 to 2.47 g/cm3. The bending strength gradually increased from 9.36 to 22.51 MPa with increasing temperatures from 1100 °C to 1500 °C, however, the bending strength remarkably decreased at 1600 °C, which was attributed to the comprehensive function of the high porosity, broken Al2O3 particles and weak connection between Al2O3 particles in the samples.