Hydrolysis‐induced simultaneous foaming and coagulation casting of secondary aluminum dross aqueous suspension.

The reactive AlN, heavy metal ions, and salts in secondary aluminum dross make them harmful to the environment and difficult to handle, and therefore categorized as hazardous solid waste. A novel, simple, and versatile technique has been proposed here to prepare hierarchically porous ceramics using secondary aluminum dross as the sole raw material, namely, the hydrolysis‐induced simultaneous foaming and coagulation casting method. As the main component, Al and AlN could be hydrolyzed to generate aluminum hydroxide sol, which can form three‐dimensional network and lead to the outstanding compressive strength of green body (7.03 MPa). Gas release during hydrolysis, high‐temperature oxidation of AlN, and metallic Al based on Kirkendall effect could account for the final multilevel pores. The utilization of harmful components in secondary aluminum dross, supplys an alternative colloidal forming way for porous green body with complex shape when combined with other ceramic powders or inorganic solid waste. Low sintering shrinkage of 1.38%–3.60% for hierarchically porous ceramics offers this highly effective and low‐cost method to be easily promoted for industrial production. [ABSTRACT FROM AUTHOR]