Zero sintering-induced shrinkage of porous oxide ceramics

Porous oxide ceramics are widely used in extreme working conditions owing to their excellent resistance to high temperatures and corrosion. However, sintering is an inevitable process applied to ceramics, from the green body to the final product. The highly complex structures exacerbate the shrinkage-induced irregular deformation and crack formation in the sintering process. A pioneering approach is developed in this study to achieve zero shrinkage for porous alumina ceramics during multistep sintering, using a combination of active fillers - ZrAl3 and Al75Si25. The response surface method is used to optimize the material compositions and sintering process, to achieve shrinkages of less than 0.05% for the entire process. The sintering expansion mechanism is investigated by analyzing the pyrolysis and microstructures of samples at different temperatures. The combination of ZrAl3 and Al75Si25 can attain the continuous expansion of the matrix in a wide temperature range of 600–1400 °C. Furthermore, typical alumina components are fabricated and used to verify the effectiveness of the proposed approach. Owing to shrinkage suppression, the profile deviation of the samples is less than 0.1 mm, and the proportion of microcracks is reduced by 97.8%. The suggested approach shows potential applications in near-net, low-defect fabrication of complex fine ceramic components.