数理科学・先端技術研究分野 & 海洋生命理工学研究開発センター　共同セミナー

開催日時

2016年4月12日（火）13：00～14：00

開催場所

横浜研究所情報技術棟5階　居室（MATシアター）

タイトル

Microstructure and yielding of colloidal clay gels

講演者

Prof. Ranjini Bandyopadhyay (Raman Research Institute)

要旨

Na-montmorillonite is a natural clay mineral and is available in abundance in nature. The aqueous dispersions of charged and anisotropic platelets of this mineral exhibit non-ergodic kinetically arrested states ranging from soft glassy phases dominated by interparticle repulsions to colloidal gels stabilized by salt induced attractive interactions. When the salt concentration in the dispersing medium is varied systematically, the viscoelasticity and yield stress of the dispersion show non-monotonic behavior at a critical salt concentration, thus signifying a morphological change in the dispersion microstructures. We directly visualize the microscopic structures of these kinetically arrested phases using cryogenic scanning electron microscopy. We observe the existence of honeycomb-like network morphologies for a wide range of salt concentrations. The transition of the gel morphology, dominated by overlapping coin (OC) and house of cards (HoC) associations of clay particles at low salt concentrations to a new network structure dominated by face–face coagulation of platelets, is observed across the critical salt concentration. We further assess the stability of these gels under gravity using direct imaging and electroacoustics. Our study, performed for concentrated clay dispersions for a wide concentration range of externally added salt, is useful in our understanding of many geophysical phenomena that involve the salt induced aggregation of natural clay minerals.