A novel process to high‐strength and controlled‐shrinkage Al <sub>2</sub> O <sub>3</sub> foams with open‐cell by Al powder hollowing technology
Zun Xia, Minghao Yang, Yedong Rong, Youfei Zhang, Yongjiao Li, Xiuhui Wang, Jinlong Yang
Abstract
Abstract Ceramic foams with open‐cell structures have attracted extensive attention due to their unique structure and superior properties. But these materials often exhibit the weakness of high sintered shrinkage and low strength at high porosity levels. In this work, novel ceramic foams with open‐cell structures have been obtained using Al powder by combining direct foaming and gelation freezing (DF–GF). The foams are assembled by hollow Al 2 O 3 particles resulting from the Kirkendall effect, in which expanded particles overcome the shrinkage of sintering. The influence of sintering temperature on the microstructure and properties of foams are investigated. The Al 2 O 3 foams show near‐zero‐shrinkage at 1773 K after undergoing the process of first expansion and then shrinkage. Compared to other conventional open‐cell foam, this foam displays relatively high compressive strength of 0.35–2.19 MPa at high porosity levels of 89.45%–94.45%, attributed to hierarchical pore structure and reaction bonding between Al and O 2 . This method from pore structure design provides a novel route for the preparation of controlled shrinkage and high‐compressive strength alumina foam with open‐cell toward potential application.