Preparation and characterization of porous MgO–Al2O3 refractory aggregates using an in-situ decomposition pore-forming technique

The porous MgO–Al2O3 refractory aggregates containing 30–92 wt% Al2O3 were prepared via an in-situ decomposition pore-forming route using magnesite and Al(OH)3 as starting raw materials. The phase compositions, pore characteristics and mechanical strengths were characterised by means of X-ray diffractometry (XRD), scanning electron microscopy (SEM), and mercury porosimetry measurements, etc. The results showed that the Al2O3 contents in the porous refractory aggregates strongly affected the spinel formation, change of the neck bonds between the particles, pore structure (porosity, average pore size and pore size distributions), and then affected the strengths. The porous MgO–Al2O3 refractory aggregates of 62–72 wt% Al2O3 showed the best combination of high apparent porosities of 42.1–44.2%, high compressive strengths of 51.1–52.0 MPa, high flexural strengths of 17.7–18.6 MPa and small average pore size of 10.81–12.07 μm.