Abstract
The dispersion effect of a focused ultrasonic field is investigated in aqueous suspensions of TiO2 and Al2O3 nanoparticles under various exposure conditions. Within a narrow time range, the effect was proportionally enhanced with exposure time. However, the nanoparticles agglomerated again with long-time exposure. For the TiO2 nanoparticles, the optimum exposure time was 10 min at an acoustic power of 28.1 W. For the Al2O3 particles, the optimum exposure time was 3 min at an acoustic power of 11.2 W.