摘要
The dispersion stabilities of three titania (TiO 2 ) nanopowders with different particle sizes and surface chemistries in aqueous suspensions containing a common water-based dispersant, ammonium polyacrylate (PAA-NH 4 ), have been investigated and compared. According to adsorption isotherm and Fourier transform infrared spectroscopy analyses, the adsorption conformations of PAA-NH 4 are distinct for the different TiO 2 nanopowders. In addition, PAA-NH 4 exhibited the greatest adsorption affinity to the larger, hydrophilic TiO 2 nanopowder and the least affinity to smaller, hydrophobic nanopowder. From sedimentation and rheological results, the dispersion stability of the larger, hydrophilic TiO 2 nanopowder was demonstrated to be the greatest. Based on thermodynamic and kinetic calculations for the stabilization energies, the larger, hydrophilic TiO 2 nanopowder was also shown to be the best-stabilized powder, although it settles faster than the smaller, hydrophilic TiO 2 nanopowder; this is due to the greater affection of sedimentation flux on the larger nanopowder. In contrast, the hydrophobic TiO 2 nanopowder formed a gel-like structure in the aqueous suspension when the solid content was greater than 10 wt%, which is attributed to polymer bridging between PAA-NH 4 -adsorbed TiO 2 nanoparticles.