Flow-small angle neutron scattering measurements of colloidal dispersion microstructure evolution through the shear thickening transition

Abstract

The shear induced microstructure for electrostatic and Brownian suspensions are compared using in situ small angle neutron scattering ͑SANS͒. The dispersions consist of 75 nm Stöber silica coated with 3-͑trimethoxysilyl͒ propyl methacrylate ͑TPM͒ and have a zeta potential of Ϫ42.6 Ϯ4.7 mV. Neutralizing the surface charge with 0.066 M nitric acid yields stable hard-sphere dispersions. SANS is conducted over a range of shear rates on the charge-stabilized and Brownian suspensions to test the order-disorder transition and hydrocluster mechanisms for shear thickening, and demonstrate the influence of stabilizing forces on the shear induced microstructure evolution. Through treatment of the colloidal micromechanics, shear induced changes in the microstructure are correlated to the hydrodynamic component of the shear stress and the thermodynamic component of the normal stress, i.e., the method of ''Rheo-SANS'' is developed. The results demonstrate that hydrocluster formation accompanies the shear thickening transition.

Design and Manufacturing of a Novel Shear Thickening Fluid Composite (STFC) with Enhanced out-of-Plane Properties and Damage Suppression

“…As the hydroclusters are made of particles momentarily compressed together to form agglomerates, the particles' ability to flow around each other is hindered and requires more energy, leading to an abrupt increase in viscosity [12,13]. When the shear stress is removed, the hydroclusters spread apart and the particles are separated, forming again a stable suspension (Fig.…”

“…As for the particles used, there are several examples in literature of the different materials that can be employed, such as CaCO 3 [20], PMMA [21,22], PVC [23], PS and SiO 2 [6,13,20]. For our purposes, different solutions were produced using two types of commercially available SiO 2 with average diameters of 7 and 14 nm (Sigma Aldrich).…”

Stress Chains Formation under Shear of Concentrated Suspension

“…Two flow states are present: one plastic, which is the same as that in the plastic zone and the second flow state, where the stress is higher. The organization of the particles can be followed by experimental techniques such as confocal microscopy or neutron scattering [3][4][5]. While these techniques are used to follow the global organization of the particles under shear, they can not give information on the stress distribution in the suspension.…”

A Review on Stab and Spike Resistance Performance of Shear Thickening Fluids (STF) Impregnated Fabrics

“…Among these proposed theories, Hydrocluster widely accepted, this theory stated the viscosity of concentrated colloidal fluids increase dramatically due to formation of aggregates particles and jammed the fluid flow [15] as shown in Fig. 2 and these theory are supported with rheological, rheo-optics and flow-SANS experiments [16], [17]. Hydrocluster can provided tools to predict the onset of shear thickening, but it unable to explain the orders of magnitude increase in viscosity during discontinuous shear thickening [18].…”