We describe particle coating using ultrasonic irradiation in liquid carbon dioxide (M). Talc (Mg3Si4O10(OH)(2)) microparticles were coated with hydrophilic and hydrophobic TiO2 nanoparticles. Shock waves generated by collapsing cavitation bubbles induced with ultrasonic irradiation accelerated the deagglomeration and dispersion of TiO2 nanoparticles and achieved dry particle coating in liquid CO2. Talc particles coated with TiO2 nanoparticles were observed using scanning electron microscopy (SEM). This revealed that the talc was completely coated with TiO2 nanoparticles, and a smooth coating surface was obtained. The flowability and wettability of the talc was improved by TiO2 nanoparticle coating. A comparative study was also conducted with conventional hand mixing and ultrasonic irradiation in water as a coating media. Effects of the experimental conditions (depressurizing method, ultrasonic intensity, TiO2 concentration, and TiO2 particle size) on the morphology and properties of the composite microparticles were also investigated.