Non-shrinkage porous ceramics by In-situ hollow sphere method based on the Kirkendall effect of Al particle

The significant shrinkage of porous ceramics after sintering has produced a number of issues with their use and development. As a result, we proposed an in-situ hollow sphere method for producing non-shrinkage alumina porous ceramics. The obtained green samples were made up of Al2O3 and Al powders, with pores emerging inside the materials due to the Kirkendall effect of Al particles after sintering. The expansion of hollowing particles exactly offsets the shrinkage generated by sintering throughout the process. When 50 vol. % Al powder (10 µm) is added, the linear shrinkage rate of the sample after sintering at 1500 °C can reach −3.47 %, and its apparent porosity and flexural strength are 30.69 % and 44.03 MPa, respectively. According to approximate calculations, the pores formed by the oxidation of Al powder are smaller than the initial size of Al powder. This method suggests a novel approach for producing controlled shrinkage porous ceramics.