Ball-Milling Assisted Pyrolysis Fabrication of VO ₂(M) Nanoparticles with Exemplary Optical Performance for Smart Windows

Abstract

Pyrolysis method has been regarded as one of the promising methods to prepare monoclinic vanadium dioxide (VO₂(M)) particles because of its low cost and easily precise phase control, while causing big particle size in the annealing process. To overcome this shortcoming, this study develops a facile but efficient ball-milling assisted pyrolysis method to synthesize VO₂(M) nanoparticles. In this process, the precursors of (NH₄)₃(VO₂(C₂O₄)₂)·2H₂O and NH₄VO₃ were obtained first through ball milling the resources of both V₂O₅ and (NH₄)₂C₂O₄·H₂O. And then, the as-obtained precursor with small size (30-100 nm) were pyrolyzed via annealing at high temperatures (>350 °C). The pyrolysis process was further in-situ tested and studied using mass spectrometry to detect and quantify the generated gas species. Finally, the as-achieved VO₂(M) nanoparticles (20-50 nm) can be used to prepare inks for window glass coatings, which exhibit exemplary optical properties with luminous transmittance (T_lum) of 56.6% and solar regulation efficiency (ΔT_sol) of 14.7% at the phase-transmit temperature (T_c) around 74.4 °C. The tungsten doping 1-3 at.% in the VO₂(M) nanoparticles can make T_c lower to ~37 °C, while keeping almost the coating with good thermochromic performance of ΔT_sol of 11.04% at T_lum of 47.63%. The results will be beneficial for fabrication of large-scale size-controllable VO₂(M) and W-doped VO₂(M) nanoparticles for smart windows.

Keywords: vanadium dioxide, pyrolysis, ball milling, nanoparticles