The effects of particle concentration, ionic strength and shearing on the microstructure of alumina nanorod suspensions

Abstract

In the present study we investigated the microstructure of suspensions of alumina nanorods while varying particle loading and pH. The diameter and length of rod particles were 10 and 50 nm, respectively and particle loading was varied from 1 to 5 vol%. Using the optical microscopy, dynamic light scattering, Turbiscan and rheological measurement, we showed that the suspensions existed as weakly flocculated gels at pH = 4 while they became strongly flocculated gels when pH was 7 or 11. The cryo-SEM images confirmed that the rod suspensions had gel structures. Strong shearing by milling or sonication changed the microstructure to a certain degree but the basic honeycomb structure was maintained.