Intercalation-enhanced electric polarization and chain formation of nano-layered particles

TL;DR

This study investigates how nano-layered smectite clay particles polarize and form structures under electric fields, revealing the role of intercalated ions and water in their polarization and potential for tuning suspension properties.

Contribution

It demonstrates the electric polarization and structuring mechanisms of nano-layered smectite clay particles, highlighting the influence of intercalated species on their electro-rheological behavior.

Findings

Clay particles polarize along silica sheets under electric fields

Intercalated ions and water molecules affect polarization and separation

Electric field induces macroscopic structuring of suspensions

Abstract

Microscopy observations show that suspensions of synthetic and natural nano-layered smectite clay particles submitted to a strong external electric field undergo a fast and extended structuring. This structuring results from the interaction between induced electric dipoles, and is only possible for particles with suitable polarization properties. Smectite clay colloids are observed to be particularly suitable, in contrast to similar suspensions of a non-swelling clay. Synchrotron X-ray scattering experiments provide the orientation distributions for the particles. These distributions are understood in terms of competing (i) homogenizing entropy and (ii) interaction between the particles and the local electric field; they show that clay particles polarize along their silica sheet. Furthermore, a change in the platelet separation inside nano-layered particles occurs under application of the electric field, indicating that intercalated ions and water molecules play a role in their electric polarization. The resulting induced dipole is structurally attached to the particle, and this causes particles to reorient and interact, resulting in the observed macroscopic structuring. The macroscopic properties of these electro-rheological smectite suspensions may be tuned by controlling the nature and quantity of the intercalated species, at the nanoscale.