Influence of polyelectrolyte dispersants on the surface chemical properties of aluminum in aqueous suspension

Colloidal processing is widely used for forming ceramics. However, its application to metal was rarely reported. To apply colloidal processing to form IrAl intermetallic compound, detailed knowledge about the surface properties of Al and its interaction with the solvent and dispersants is indispensable. In this study, the hydration process, the surface potential and particle dispersion of Al in aqueous suspension with and without dispersants were investigated. The effects of two polyelectrolyte dispersants, an anionic PAA^- and a cationic PEI-H⁺, were studied. Time dependence of pH value indicated that both dispersants promoted the hydration of Al, while the slow hydration stopped in several hours due to the formation of the bayerite layer. Addition of the dispersants greatly increased the absolute zeta potential values, indicating strong interactions with the Al particle. Comparison of particle size suggested that PEI-H⁺ was better than PAA^- for the dispersion of Al, although the latter could induce a much higher absolute zeta potential. FTIR spectroscopy indicated that the interaction in the Al-PAA^- system was mainly between the -COO^- group of PAA^- with the Al surface groups, while hydrogen bonding was the main interaction in the Al-PEI-H⁺ system. The results also implied that not the electrostatic effect, but the steric effect was dominant for the dispersion of Al.