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.

Graphical abstractAfter the plasma treatment process, the spherical powders with smooth surface were formed. The energy of the plasma flame was high enough to melt the granules on the particle surface which cause the particle size become smaller. The surface of the plasma treated powders showed obvious signs of melting and there were lots of nano-sized grains formed in the surface of the plasma treated powders.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Nanostructured Al2O3–TiO2 powders were prepared by spray drying, heat and plasma treatment. ► The minimum water content of the slurry suitable for spray drying was 47 wt.%. ► The composite particles underwent fast liquid sintering process in plasma flame. ► The tap density of the heat treated powders was increased after plasma treatment. ► The flowability of the heat treated powders was improved after plasma treatment.