Microstructures and properties of novel lightweight refractory aggregates with microporous MgO@MgAl2O4 core-shell structures.

Microporous aggregates are the key to the lightweight design and preparation of refractories for the working linings of the high temperature furnaces. In this work, the lightweight MgO-MgAl 2 O 4 refractory aggregates with core-shell structures were prepared by in-situ decomposition synthesis technology using Mg(OH) 2 and nano-size Al 2 O 3 as raw materials. The influence of the nano-size Al 2 O 3 content on the microstructures and properties was thoroughly studied. The results demonstrated that the microporous MgO core structures were formed after the decomposition of Mg(OH) 2 , and the MgAl 2 O 4 bonds between the microporous MgO core structures were formed through the reaction between the nano-size Al 2 O 3 and MgO. When the nano-size Al 2 O 3 contents were less than 9 wt%, the MgAl 2 O 4 bonds were discontinuous. With the increase of the nano-size Al 2 O 3 contents to 9–15 wt%, more continuous MgAl 2 O 4 bonds (i.e. MgAl 2 O 4 shell structures) were formed at the surface of the microporous MgO core structures. Overall, the optimized specimens were lightweight MgO-MgAl 2 O 4 refractory aggregates with the addition of 9 wt% nano-size Al 2 O 3 , which exhibited the microporous MgO@MgAl 2 O 4 core-shell structures, a median pore size of 268 nm, a high compressive strength of 105 MPa, and a low thermal conductivity of 4.1 W/(m·K) at 800 ℃. [ABSTRACT FROM AUTHOR]