Investigation on Microstructures, Strengths and Fracture Behavior of Lightweight MgO-Mg(Al, Fe)2O4 2 O 4 Refractories: Effect of the Mg(Al, Fe)2O4 2 O 4 Content of Microporous Aggregates

In this work, lightweight refractories were successfully prepared by using microporous MgO-Mg(Al, Fe)2O4 2 O 4 aggregates and magnesia powder as raw materials. The effect of the Mg(Al, Fe)2O4 2 O 4 content of microporous aggregates on the microstructures, strengths and fracture behavior of the lightweight refractories was studied and compared with the dense periclase-hercynite refractory obtained from the markets via SEM, EDS and the wedge splitting test (WST) with the digital image correlation (DIC), etc. The results showed that the porous surface of the microporous aggregates increased the contact area between the aggregates and the matrix, and then promoted the formation of interface bonding between them. Meanwhile, the Mg(Al, Fe)2O4 2 O 4 in microporous aggregates possessed the ability to induce crack deflection. And the microporous structure effectively absorbed the stress. Furthermore, the aggregate/matrix interface bonding, the Mg(Al, Fe)2O4 2 O 4 as well as microporous structure of the aggregates jointly affected the mechanical properties of the lightweight MgO-Mg(Al, Fe)2O4 2 O 4 refractories. Compared with the dense periclase-hercynite refractories, the thermal conductivity of the lightweight MgO-Mg(Al, Fe)2O4 2 O 4 refractories (LPCS11) reduced by 40.8 %, and then the compressive strength, the flexural strengths before and after thermal shock were enhanced by 78.5 %, 246.8 % and 114.9 %, respectively. The lightweight MgO-Mg(Al, Fe)2O4 2 O 4 refractories prepared from the microporous aggregates with 11.0 wt% Mg (Al, Fe)2O4 2 O 4 exhibited better comprehensive properties with the apparent porosity of 26.0 %, compressive strength of 105.7 MPa, flexural strength before the thermal shock of 21.5 MPa, flexural strength after the thermal shock of 10.1 MPa and thermal conductivity of 1.262 W/(m center dot K). center dot K).