Preparation and properties of magnetic alumina microspheres with a γ-Fe2O3/SiO2 core and Al2O3 shell

Magnetic alumina composite microspheres with γ-Fe2O3 core/Al2O3 shell structure were prepared by the oil column method. A dense silica layer was deposited on the surface of γ-Fe2O3 particles (denoted as γ-Fe2O3/SiO2) with a desired thickness to protect the iron oxide core against acidic or high temperature conditions. γ-Fe2O3/SiO2/Al2O3 particles with about 85 wt% Al2O3 were obtained and showed to be suitable for practical applications as a magnetic catalyst or catalyst support due to their magnetic properties and pore structure. The products were characterized with scanning electron microscope (SEM) and transmission electron microscope (TEM), nitrogen adsorption-desorption, and vibrating sample magnetometer (VSM). The specific surface area and pore volume of the γ-Fe2O3/SiO2/Al2O3 composite microspheres calcined at 500 °C were 200 m2/g and 0.77 cm3/g, respectively.