Preparation and characterization of porous zircon aggregates by granulation method: Roles of the polymorphism of Al2O3

In this paper, eight zircon granules were prepared by granulation method, using zircon powders as raw material, alpha-Al2O3 and gamma-Al2O3 as additives and sodium carboxymethyl cellulose (CMC) as binder, respectively. Then, the influence of alpha-Al2O3 and gamma-Al2O3 addition on phase composition, lattice parameters, microstructure and physical characterization were investigated by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The results reveal that Al2O3 could influence the Al2O3-ZrSiO4 system by reacting with SiO2 and dissolving into the zircon crystal lattice. The changing of the crystal lattice and the formation of mullite were the main influence factor. The zircon aggregate with 3.0 wt% gamma-Al2O3 rendered an optimal apparent porosity of 25.2 %, a high cylinder compressive strength retention rate of 55.1 %, a relatively homogeneous pore size distribution and a smaller changing in lattice parameters.