Abstract
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.
Highlights
Boron carbide (B4C) owes to its suitability as a material for armour, abrasives and cutting tools to its impressive mechanical and thermal properties which include ultra-high hardness, high strength, low specific gravity (2.52) and high melting point (2450 °C) [1,2]
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
This paper focuses on determining the zeta (ζ) potential and rheology of aqueous B4C suspensions which each contain powder of nominally the same specification to reveal variances in colloidal performance
Summary
Boron carbide (B4C) owes to its suitability as a material for armour, abrasives and cutting tools to its impressive mechanical and thermal properties which include ultra-high hardness, high strength, low specific gravity (2.52) and high melting point (2450 °C) [1,2]. Hunter and Greenwood have produced excellent reviews of electroacoustic technology used within this study when applied to colloids [22,23], Dukhin provides a thorough presentation of the mathematics involved in characterising colloids using ultrasound whilst debating the differences in approach of the electrokinetic sonic amplitude (ESA) and the colloidal vibration potential (CVP) methods [24]. Another issue this work begins to address is the disparity between different batches of B4C which are observed when processing. Understanding this behaviour will allow appropriate treatments to be devised for powders of different batches and from different manufacturers
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