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

Abstract

ray scattering (including small-angle scattering). PACS. 82.70.Dd -Colloids. PACS. 83.80.Gv -Electro-and magnetorheological fluids.Abstract. -Microscopy observations show that suspensions of synthetic and natural nanolayered 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 nonswelling 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 electrorheological smectite suspensions may be tuned by controlling the nature and quantity of the intercalated species, at the nanoscale.In this letter we study colloidal suspensions of electrically-polarizable particles in nonconducting fluids. When such suspensions are subjected to an external electric field, usually of the order of 1kV/mm, the particles become polarized, and subsequent dipolar interactions are responsible for aggregating a series of interlinked particles that form chains and columns parallel to the applied field. This structuring occurs within seconds, and disappears almost instantly when the field is removed [1][2][3][4][5]. It coincides with a drastic change in rheological properties (viscosity, yield stress, shear modulus, etc.) of the suspensions [6], which is why they are sometimes called electrorheological fluids (ERFs). This makes the mechanical behavior readily controllable by using an external electric field [1][2][3][4][5][6][7]. Particle size has a quite diverse impact on the behavior of ERFs [8]. The nature of the insulating fluid and of the colloidal particles determines the electrorheological behavior of the suspensions. The mechanism is not fully understood yet, but it is mainly triggered by the so-called interfacial polarization, EDP Sciences

Active structuring of colloidal armour on liquid drops

“…In addition, we show that colloidal ribbons, once assembled, can be dynamically modulated by tuning the electric field strength, provided the colloidal particles are polarizable and can form dipolar chain structures on the drop surface. To our knowledge, this is the first realization of a Winslow electro-rheological type system3132 confined to a 2D surface.…”

Electrorheological properties of organically modified nanolayered laponite: influence of intercalation, adsorption and wettability

“…Because of their controllable viscosity and short response time, ER materials are potential materials for use in active devices, brakes, clutches, shock absorbers and actuators. [10][11][12][13][14][15][16][17][18] The wettability of the particle with respect to silicone oil is very important for enhancing the ER effect. Moreover, anti-electric breakdown, stability and strong polarization are closely related to the wettability of particles.…”

Electric field nematic alignment of fluorohectorite clay particles in oligomeric matrices

“…In previous studies by our group, the average orientational clay distribution was measured in a silicone oil system [9,11]. In the present study the clay particles are instead dispersed in melted paraffin-wax.…”