Halos mechanism in stabilizing of colloidal suspensions: Nanoparticle weight fraction and pH effects

Nanoparticle halo is a novel method that stabilizes colloidal suspensions with high efficiency compared to conventional methods. But, up to now few articles have been published on the stabilization mechanism of this method. This article investigates the dispersion behavior of colloidal Al2O3 aqueous suspensions in the presence of highly charged CeO2 nanoparticles and the effect of two key parameters; the ceria nanoparticle concentration and pH on the stability of Al2O3–CeO2 bidispersed suspensions. The stability behavior of these suspensions was investigated by sedimentation technique. It was concluded from this work that by increasing ceria nanoparticle concentration the stability of these bidispersed systems reaches an optimum condition, but further increasing of nanoparticles results in decreasing of the colloidal suspension stability. Also, the results showed that the suspensions have optimum dispersion state and high stability at pH 10. The calculated DLVO interparticle interaction potentials verified the experimental results of the pH effect on the stability behavior. The stabilization of the bidispersed suspensions was also evidenced by scanning electron microscopy (SEM) and SEM energy dispersive X-ray analysis (SEM/EDXA) of the sediment layers after 3 weeks.