Preparation of nanostructured alumina–titania composite powders by spray drying, heat treatment and plasma treatment

Nanostructured Al2O3–13 wt.%TiO2 composite powders were successfully prepared by spray drying, heat treatment and plasma treatment. The as-prepared composite powders were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy, respectively. The tap density and flowability were measured by tap density instrument and hall flowmeter, respectively. The results showed that the minimum water content of the slurry suitable for spray drying was 47 wt.%, and the corresponding spray dried powders had the maximum density and flowability. Spherical and porous powders had been obtained by spray drying technology. The sphericity of the particles and the pores in the particles were decreased after heat treatment, and the density of the powders was increased. The composite particles underwent fast liquid sintering process in high energy plasma flame. After plasma treatment, spherical powders with smooth surface were formed. The plasma treated composite particles were composed of a large number of nano-sized grains. The tap density of the spray dried powders was increased after heat treatment, and the tap density of the heat treated powders was further increased after plasma treatment. The flowability of the spray dried powders was decreased after heat treatment, and the flowability of the heat treated powders was significantly improved after plasma treatment.