Rheological Properties and Small-Angle Neutron Scattering of a Shear Thickening, Nanoparticle Dispersion at High Shear Rates

2006 ◽  
Vol 45 (21) ◽  
pp. 7015-7024 ◽  
Author(s):  
Young S. Lee ◽  
Norman J. Wagner
Keyword(s):  
Neutron Scattering ◽  
Rheological Properties ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Shear Thickening ◽  
High Shear ◽  
Nanoparticle Dispersion ◽  
Shear Rates ◽  
High Shear Rates

Capillary RheoSANS: measuring the rheology and nanostructure of complex fluids at high shear rates

Soft Matter ◽  
2020 ◽  
Vol 16 (27) ◽  
pp. 6285-6293
Author(s):  
Ryan P. Murphy ◽  
Zachary W. Riedel ◽  
Marshall A. Nakatani ◽  
Paul F. Salipante ◽  
Javen S. Weston ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Complex Fluids ◽  
Inorganic Nanoparticles ◽  
High Shear ◽  
Capillary Rheometry ◽  
Shear Rates ◽  
High Shear Rates

Capillary rheometry is combined with small-angle neutron scattering to simultaneously measure the viscosity and nanostructure of complex fluids containing proteins, surfactants, polymers, and inorganic nanoparticles at shear rates up to 106 s−1.

Shear Induced Phase Behavior of Polymer Blends by Small Angle Neutron Scattering

1989 ◽  
Vol 166 ◽  
Author(s):  
Alan I. Nakatani ◽  
Hongdoo Kim ◽  
Charles C. Han
Keyword(s):  
Neutron Scattering ◽  
Polymer Blends ◽  
Phase Behavior ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Large Body ◽  
Concentric Cylinder ◽  
Shear Rates ◽  
Lower Shear ◽  
High Shear Rates

ABSTRACTThe phase behavior of polymer blends and solutions can be changed dramatically by a flow field using a variety of flow geometries. Unlike simple binary fluids which require extremely high shear rates to produce only small shifts in the phase boundary, polymer phase behavior may be influenced by as much as 10 degrees with the application of much lower shear rates. However, there is a large body of conflicting data concerning the nature of these shear effects in polymers.Here we report on the effects of shear on the phase behavior of polymer blends by small angle neutron scattering (SANS). Experiments were conducted using a specially constructed, concentric cylinder apparatus for in situ studies of concentrated polymer solutions and melts. Two separate systems will be discussed: 1) a blend of polystyrene and polybutadiene. 2) a blend of polystyrene and poly(vinylmethylether). Both systems exhibit shifts in the phase behavior which indicate shear induced mixing in agreement with previous results obtained by other techniques. These results will be interpreted within the context of existing theories of shear induced phase behavior.

Small-angle neutron scattering study of shear-induced phase separation in aqueous poly(N-isopropylacrylamide) solutions

e-Polymers ◽  
2004 ◽  
Vol 4 (1) ◽  
Author(s):  
Markus Stieger ◽  
Peter Lindner ◽  
Walter Richtering
Keyword(s):  
Phase Separation ◽  
Shear Flow ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Separation Process ◽  
High Shear ◽  
Shear Rates ◽  
High Shear Rates ◽  
Strong Shear ◽  
Phase Separation Process

Abstract The influence of shear flow on the structure of concentrated aqueous poly(N-isopropylacrylamide) solutions near the lower critical solution temperature was investigated by means of small-angle neutron scattering. Two samples, both in the semi-dilute regime above the overlap concentration, were studied. The scattering curve of the less concentrated sample was not influenced by shear flow, although high shear rates were reached. The more concentrated 4 wt.-% sample, however, displayed shear-induced demixing under strong shear flow conditions. Experiments at different shear stresses indicated the existence of a threshold shear stress and the phase separation process became faster with increasing stress. The two-dimensional scattering patterns remained isotropic even during the phase separation process and the correlation length as obtained from an Ornstein- Zernike plot increased. The influence of shear flow on the phase separation process is thus similar to a temperature increase. The results are in excellent agreement with data from recent rheo-optical experiments where shear-induced phase separation was also observed for the concentrated solution at high shear rates. Apparently, strong shear flow exerts an effect analogous to a temperature increase.

scholarly journals A small-angle neutron scattering investigation of rigid polyelectrolytes under shear

2003 ◽  
Vol 36 (4) ◽  
pp. 1000-1005 ◽  
Author(s):  
E. Mendes ◽  
S. Viale ◽  
O. Santin ◽  
M. Heinrich ◽  
S. J. Picken
Keyword(s):  
Neutron Scattering ◽  
Cross Sections ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Deuterated Water ◽  
Shear Rates ◽  
Scattering Spectrum ◽  
High Shear Rates ◽  
Low Concentrations ◽  
Small Shear

Solutions of a rigid polyelectrolyte molecule, sulfo-poly(phenyleneterephthalamide) (SPTTA), in deuterated water have been investigated using small-angle neutron scattering. At low concentrations (1 wt%) the scattering spectrum presents a soft maximum similar to that of the interaction of rod-like objects. Two counterions are used, H+and Li+, and it is shown that aggregation is favoured as the proportion of Li+counterions increases. When kept at rest at room temperature, the solutions exhibit spontaneous birefringence. A 1 wt% solution was investigated under shear and it is shown that a very small shear rate is needed to produce a very strong alignment of rod-like objects. Such alignment saturates at high shear rates. Upon cessation of shear, a very long relaxation time is observed. The set of results strongly suggest aggregation of rigid polyelectrolyte molecules into long needles exhibiting very small cross sections.

Shear Thinning and Thickening of Alumina Suspensions

2010 ◽  
Vol 105-106 ◽  
pp. 833-836
Author(s):  
Xiang Yang Lu ◽  
Li Ming Zhang ◽  
Yong Huang
Keyword(s):  
Zeta Potential ◽  
Particle Surface ◽  
Shear Thickening ◽  
Shear Thinning ◽  
High Shear ◽  
Shear Rates ◽  
High Shear Rates ◽  
Stern Potential ◽  
Thickening Behavior ◽  
Alumina Suspensions

The rheological behavior of alumina suspension stabilized with Tri-ammonia citrate (TAC) was studied. It was thought that there would form some particle clusters due to the collisions between particles caused by their relative motion in the suspension, and such particle clusters are classified as thermodynamic clusters and hydrodynamic clusters by their origin. Shear thinning is the result of decomposition of the thermodynamic clusters, while shear thickening is the result of formation of the hydrodynamic clusters. From the view of cluster-forming potential barrier, it was deemed that the viscosities of alumina suspensions at low and high shear rates are respectively determined by zeta potential and Stern potential on the particle surface, and shear thickening behavior can be suppressed with some excessive TAC.

Rheology of Nanofluids in Microchannels

2008 ◽  
Author(s):  
Fre´de´ric Ayela ◽  
Olivier Tillement ◽  
Julien Chevalier
Keyword(s):  
Rheological Properties ◽  
Peclet Number ◽  
High Shear ◽  
Shear Rheology ◽  
Péclet Number ◽  
Shear Rates ◽  
High Shear Rates ◽  
On Chip ◽  
Very High ◽  
High Shear Rheology

Microfluidics is often presented for applications where only microliters sample volumes are available. But the benefits of microchannels do not reduce to a low consumption of fluids. From a physical and mechanical point of view, microfluidics can offer high shear rates combined with low Reynolds number and low viscous heating. It becomes possible to explore high shear rheology on a lab-on-chip. We have micromachined microviscometers to study the rheological properties of nanofluids under very high shear rates conditions. Nanofluids are fluid suspensions of solid nanoparticles. Recent experiments have indicated an anomalous increase in thermal conductivity of these suspensions. But less attention has been payed to the rheological properties of nanofluids. The few results concerning the viscosity of nanofluids exhibit scattered values higher than those of fluid suspensions of microparticles, because of a higher rate of collisions due to Brownian motion and shearing motion which enhance aggregation. These experiments were performed with commercially available rheometers over a limited range of shear rates. Our viscometers on chip are silicon — Pyrex microchannels (H ≈ 10 – 20 μm) equipped with local pressure drop sensors. Nanofluids under test were ethanol-based SiO2 nanoparticles. For particle sizes from 20 nm to 190 nm, and solid volume fractions from 1.4% to 7%, a newtonian behaviour has been observed up to 5.104 s−1. High shear rheology is the only way to reach high Peclet number values with nanoparticles in a laminar flow. It was possible to cover a wide range of Peclet number and to have Pe > 1 with diameter in the tens of nanometers range. Our results have demonstrated that an apparent solid volume fraction φa > φ, due to aggregation, was responsible of the increment of viscosity. More important was the demonstration that the shape of the clusters could be modified and that the ratio φa/φ could be lowered by a very high shear rate. Very high shearing rates in microchannels appear to be a way for nanofluids to converge to a well-defined value of viscosities.

Sign in / Sign up

Export Citation Format

Share Document