Preparation and formation mechanism of phase-controlled titanium dioxide microspheres by selective laser heating in liquid medium

Abstract

An approach for the fabrication of crystal-controlled microspheres from nanoparticles is presented, in which the nanoparticles were melted to form microspheres by selective laser heating in liquid medium. As an example, anatase titanium dioxide was selected as a typical material due to its metastability. The results showed that the single-crystalline rutile spheres, amorphous titanium dioxide spheres and polycrystalline anatase spheres could be prepared from anatase titanium dioxide nanoparticles. The formation of the microspheres was investigated under a variety of irradiation wavelengths and input laser fluences, and the formation mechanisms were discussed according to three aspects: melting–quenching process, laser-induced chemical transition process and liquid-medium heat transfer process.