Dispersion of Nanoparticles in Water Using a High Pressure Wet-type Jet Mill

Abstract

The quality of dispersion of nanoparticles, which agglomerate strongly, greatly influences the processing process and the quality of final products such as sintered bodies. Therefore, the technology of nanoparticle dispersion is considered as an important element in industry.
In the present work, aqueous suspensions of nanoparticles were produced by a high pressure wet-type jet mill, using SiO₂ (primary particle diameter: about 20 nm) and Al₂O₃ (primary particle diameter: about 13 nm) as dispersed particles. The effects of the operating conditions on the mean size of particles, and the relation of the mean particle size to aqueous suspension viscosity were examined.
The volumetric mean diameter (d_v) decreased with increasing processing pressure (P), number of passages (N) and concentration of particles (C), but did not decrease to the primary particle size. The agglomerated particle size was 5.9-7.4 and 6.5-8.1 times the primary particle size for SiO₂ and Al₂O₃, respectively. Therefore, dispersion became increasingly difficult as primary particle size decreased. For all the present experimental conditions, the relationship between d_v and the energy dissipation rate (ε) could be expressed by a straight line with a slope of −0.03 on logarithmic paper. Aqueous suspensions of both types of particles exhibited plastic behavior at N=0, and pseudo-plastic behavior at N≥1. Furthermore, the pseudo-plasticity decreased with increasing N, and at N≥10 the aqueous suspensions apparently exhibited Newtonian behavior.