Preparation of low radioactivity spherical silicon oxide powders via chemical-flame spheroidizing process

In this work, a chemical-flame spheroidizing method was proposed to facilely prepare low radioactivity spherical silicon oxide powders. Firstly, the rice husks, composed of silicon oxide frame, were employed as the raw materials to prepare high-purity colloidal silica nanoparticles with the size 24 nm via a simple “pyrolyzation–ashing–dissolvation” process. Then, the silica colloid was further treated by a spraying–drying process to mainly form mushroomhead-shaped silica particles with particle size 0.5–10 μm. Most of the powders were hollow, the thickness of the walls of hollow silicon oxide powders was about 50–100 nm. The surfaces were rough, the powders had poor fluidity and the apparent density was only 0.21 g/cm3. Finally, almost all these submicro and microparticles were densified by an oxygen–acetylene flame spheroidizing process to get low radioactivity spherical silicon oxide powders with the size 0.5–5 μm. The fluidity, the apparent density and the content of U of the as-prepared spherical silicon oxide powders reached 94 s/50 g, 0.721 g/cm3 and 0.05 × 10−9g/g, respectively. Such silicon oxide material originating from rice husks could potentially be used in very large scale integration field.