A strategy for controlling microstructure and mechanical properties of microporous spinel (MgAl2O4) aggregates from magnesite and Al(OH)3

Abstract

In the present work, a novel strategy is proposed to control the microstructures of microporous spinel aggregates and improve their strengths. This strategy controls the in-situ decomposition behavior of raw material particles and the Kirkendall effect through preheating magnesite and Al(OH)3, then milling with balls and water. Thus, the expected microstructures of microporous spinel aggregates can be obtained. Four microporous magnesium aluminate spinel aggregates of stoichiometric ratio were prepared using magnesite, Al(OH)3, calcined magnesite, and calcined Al(OH)3. The microstructures and strengths of microporous spinel aggregates were analyzed by XRD, SEM, image analysis method, etc. The microporous spinel aggregates prepared from magnesite and Al(OH)3 had slightly lower apparent porosity (58.2%) than the one (59.2%) synthesized from Al(OH)3 and calcined magnesite. In addition, the median pore size significantly reduced from 9.5 to 6.8 µm, and the compressive strength dramatically increased from 7.3 to 15.2 MPa. These results verify the reliability of this strategy.