Preparation of VO2 (M) nanoparticles with exemplary optical performance from VO2 (B) nanobelts by Ball Milling

Abstract Vanadium oxide (B) (VO2 (B)), easily obtained by a hydrothermal method, can be transformed to VO2 (M/R) under high-temperature annealing treatment (>500 °C) without oxygen atmosphere. However, the coarsening of VO2 (M/R) particles is always observed after high-temperature annealing, which may seriously degrade optical properties. In this study, the ball milling method is used, for the first time, to transform VO2 (B) nanobelts into spherical VO2 (M/R) nanoparticles with the average particle size of 38 nm at room temperature and under atmospheric conditions. The effects of ball-to-powder weight ratio (BPR) and milling time on crystalline phase and morphology of VO2 were systematically investigated and found the optimum processing parameters with BPR of 10:1 and the milling time of 3 h. The thin coating based on the obtained VO2 (M/R) nanoparticles shows good optical properties that the modulation ability can reach up to 14.03% while the visible light transmittance is 41%, which promotes the practical application in smart windows. In addition, the mechanism of the phase transformation from VO2 (B) to VO2 (M/R) is analyzed and confirms that the pressure caused by ball collision plays a major role in the ball milling process.