(271a) The Effect of Nanoparticles on the Structure and Rheology of Kaolinite Suspensions

Suspensions of clay particles (kaolinite) combined with silica nanospheres and various salts undergo a dramatic stabilization process, which increases suspension viscosity as well as elasticity to the point where the suspensions can support their own mass as well as be sectioned. The suspensions develop significant yield stresses (from 2 to >3500 Pa, which exceeds instrument capabilities), which can be overcome by vigorous shaking, before rejuvination to their original, gelled state. From oscillatory measurements, the development of |η*| versus time indicates two distinct time scales for gelation; one less than one hour and another at tens of hours (long times). Thus far, these transitions have been observed for kaolinite concentrations at 14% vol., nanosphere concentrations as small as 2% vol, 3 different nanosphere sizes and 4 different salts. SEM imaging obtained by cryogenic drying of the samples indicates that the added nanospheres induce a more ordered sponge-like microstructure, possibly arising from highly localized phase separation.