Colloidal dispersion of nano-scale ZnO powders using amphibious and anionic polyelectrolytes

This article describes the dispersion of aqueous suspensions containing nano-scale ZnO powder by utilizing a hybrid of chemical dispersant and mechanical mixing/grinding process. The chemical dispersants included anionic or amphibious polyelectrolytes, i.e., sodium salt of polymethylacrylic acid (PMAA-Na) or polyacrylamide/(α-N, N-dimethyl-N-acryloyloxyethyl) ammonium ethanate (PDAAE). The optimum critical concentrations for each dispersants to achieve the lowest viscosity, smallest final sediment volume and particle size (d50) for the nano-ZnO suspensions, 3 wt.% for PMAA-Na and 5 wt.% for PDAAE, were identified. The finely dispersed nano-ZnO powders were transferred to prepare sputtering target. The root-mean-square roughness (RRMS) of thin films deposited by utilizing such a target was found to be 2.05 nm, which was lower than the RRMS of the film (≈27.57 nm) deposited by using a commercial ZnO target comprised of micro-scale granules.