Electrostatic charge dependence on surface hydroxylation for different Al2O3 powders

The effect of surface chemistry on the electrostatic charge in α-Al2O3 powders was studied. Net charge and tribo-charge of dry powders were measured by the Faraday double cup procedure. High electrostatic charge values were observed in powders with high surface hydroxylation by IR spectroscopy. The nature of hydroxyl groups at the surface determines the polarity of the electrostatic charge. Mixture of particles having intrinsic electrostatic positive and negative charges follows the lever rule. Dry mixtures of differently charged particles favour the dispersion of smaller particles on the surface of the largest ones. An effective random dispersion was achieved by a low-energy process that allowed preserving the morphology of the supporting and supported particles.