A zeta potential and rheology study using electroacoustic spectroscopy on aqueous boron carbide suspensions

The zeta (ζ) potential of moderately concentrated (at 15 vol%) boron carbide (B4C) suspensions were characterised using electroacoustic spectroscopy. This technique has been validated for use in this application by correlating the ζ-potential to the suspension viscosity (at 30 vol%) across a range of pH values. Zeta potential has been shown to be effective in determining differences in B4C powders, reported to be nominally of the same specification in terms of particle size distribution and X-ray diffraction data. The isoelectric (IEP) points for three different as-received B4C powders were found to be 4, 7 and less than 2.5. The study showed that differences in ζ-potential across the powders can be minimised via heat treatment, which produced suspensions all with an IEP below 2.5. The study also established the effect of an anionic and a cationic dispersant on ζ-potential and rheology, demonstrating that excess dispersant from a ζ-potential perspective was required to obtain the lowest viscosity. The study concluded that as-received B4C powders most likely contain contaminants of a cationic nature and that electroacoustic spectroscopy is a useful tool in determining their behaviour in aqueous suspensions.