Polar-molecules-driven enhanced colloidal electrostatic interactions and their applications in achieving high active electrorheological materials

2008 ◽  
Vol 23 (2) ◽  
pp. 409-417 ◽  
Author(s):  
L. Xu ◽  
W.J. Tian ◽  
X.F. Wu ◽  
J.G. Cao ◽  
L.W. Zhou ◽  
...  
Keyword(s):  
Yield Stress ◽  
Electrostatic Interactions ◽  
Colloidal Particles ◽  
Sol Gel ◽  
Polar Molecules ◽  
Highly Active ◽  
Static Yield ◽  
Er Fluids ◽  
Er Fluid ◽  
Static Yield Stress

We have fabricated a class of colloidal electrorheological (ER) fluids, in which suspended TiO2 particles were synthesized by a sol-gel method and modified by 1,4-butyrolactone molecules with a permanent molecular dipole moment of 4.524 D. Compared with pure TiO2 ER fluids, the quasi-static yield stress of the polar- molecules-modified ER fluid is enhanced as high as 48.1 kPa when subjected to an external electric field of 5 kV/mm. Also, it possesses other attractive characters such as low current density (<14 μA/cm2) and low sedimentation. Based on a Green’s function method, we present a first-principles approach to investigate colloidal electrostatic interactions. Excellent agreement between experiment and theory has been shown for the enhancement ratio of quasi-static yield stress, which quantitatively reveals that enough polar molecules oriented within the field-directed gap between the colloidal particles can unexpectedly enhance the interactions, thus yielding the unusual enhancement. This shows a promising and flexible direction for achieving more highly active ER materials.

LANTHANUM TITANATE NANOPARTICLES ER FLUIDS WITH HIGH PERFORMANCE

2012 ◽  
Vol 26 (13) ◽  
pp. 1250079 ◽  
Author(s):  
DE WANG ◽  
RONG SHEN ◽  
SHIQIANG WEI ◽  
KUNQUAN LU
Keyword(s):  
Yield Stress ◽  
Silicone Oil ◽  
Heating Temperature ◽  
Hydroxyl Group ◽  
Lanthanum Titanate ◽  
Different Temperatures ◽  
Static Yield ◽  
Er Fluids ◽  
Er Fluid ◽  
Static Yield Stress

A new type of electrorheological (ER) fluid consisting of lanthanum titanate (LTO) nanoparticles is developed. The ER fluids were prepared by suspending LTO powder in silicone oil and the particles were fabricated by wet chemical method. This ER fluid shows excellent ER properties: The static yield stress reaches over 150 kPa under 5 kV/mm with linear dependence on the applied DC electric field, and the current density is below 10 μA/cm2. In order to investigate the affect factor on the ER behavior, the LTO powder were heated under different temperatures. The ER performances of two particles treated under different temperatures were compared and the composition changes for those particles were analyzed with TG-FTIR technique. It was found that the static yield stress of the suspensions fell from over 150 kPa to about 40 kPa and the current densities decreased prominently as the rise of the heating temperature. TG-FTIR analysis indicated that polar groups remained in the particles such as alkyl group, hydroxyl group and carbonyl group etc., contribute to the ER effect significantly. The experimental results are helpful to understand the mechanism of the high ER effect and to synthesize better ER materials.

Static yield stress of ER fluids and the role of electric current

1997 ◽  
Vol 40-41 ◽  
pp. 699-704
Author(s):  
T. Sakai ◽  
K. Kobayashi ◽  
M. Sato
Keyword(s):  
Electric Current ◽  
Yield Stress ◽  
Static Yield ◽  
Er Fluids ◽  
Static Yield Stress

scholarly journals Strong Electrorheological Performance of Smart Fluids Based on TiO2 Particles at Relatively Low Electric Field

2021 ◽  
Vol 8 ◽  
Author(s):  
Yuchuan Cheng ◽  
Zihui Zhao ◽  
Hui Wang ◽  
Letian Hua ◽  
Aihua Sun ◽  
...  
Keyword(s):  
Electric Field ◽  
Yield Stress ◽  
Sol Gel ◽  
Interfacial Polarization ◽  
High Yield ◽  
Characteristic Structure ◽  
High Yield Stress ◽  
Large Yield ◽  
Er Fluids ◽  
Er Fluid

Electrorheological (ER) fluids are a type of smart material with adjustable rheological properties. Generally, the high yield stress (&gt;100 kPa) requires high electric field strength (&gt;4 kV/mm). Herein, the TiO2 nanoparticles were synthesized via the sol–gel method. Interestingly, the ER fluid-based TiO2 nanoparticles give superior high yield stress of 144.0 kPa at only 2.5 kV/mm. By exploring the characteristic structure and dielectric property of TiO2 nanoparticles and ER fluid, the surface polar molecules on samples were assumed to play a crucial role for their giant electrorheological effect, while interfacial polarization was assumed to be dominated and induces large yield stress at the low electric field, which gives the advantage in low power consumption, sufficient shear stress, low leaking current, and security.

TOWARDS UNDERSTANDING ER FLUIDS USING SALS/RHEOMETRY

1996 ◽  
Vol 10 (23n24) ◽  
pp. 3029-3036
Author(s):  
Bryan J. Crosby ◽  
Tom McLeish ◽  
Harry Block
Keyword(s):  
Yield Stress ◽  
Indium Tin Oxide ◽  
Volume Fraction ◽  
Ethylene Vinyl Acetate ◽  
High Volume ◽  
Polystyrene Solution ◽  
Static Yield ◽  
Poly Ethylene ◽  
Er Fluids ◽  
Er Fluid

This paper details work in Cranfield and Leeds Universities of making a stock of transparent ER fluids, which could later be utilised in a new optical electro rheometer (OER) to be assembled at Leeds University. Two basic routes were attempted. One was to use glass microspheres and the other was to use polymer spheres. In order to increase the strength of the ER effect, it was necessary to increase the volume loading while still maintaining sufficient transmission (about 75% over 2 mm). It was found to be possible to increase the ER effect quite substantially in some instances, and in others it was possible to get a near perfect refractive index match. It was not possible to combine both requirements in one fluid such that a high static yield stress was apparent in a transparent ER fluid. However one fluid was made which gave acceptable diffraction losses at high volume fractions, remained in suspension for extended periods and provide about 700 Pa yield stress at 4kV/mm and about 30% volume fraction viz: untreated poly(ethylene vinyl acetate) microspheres in Cereclor/bromonaphthalene/polystyrene solution. The OER being assembled at Leeds University is intended to record small angle light scattering (SALS) profiles, electrical and mechanical properties of ER fluids simultaneously. The OER is based around a DSR 500 machine purchased from Rheometric Scientific with quartz tools coated with transparent indium tin oxide(ITO), which is capable of measuring both steady state (DC) and oscillatory (AC) material parameters.

Coating of Polyaniline with an Insulating Polymer to Improve the Power Efficiency of Electrorheological Fluids

1999 ◽  
Vol 13 (14n16) ◽  
pp. 1931-1939 ◽  
Author(s):  
J. Akhavan ◽  
K. Slack ◽  
V. Wise ◽  
H. Block
Keyword(s):  
Power Efficiency ◽  
Electrorheological Fluids ◽  
Emeraldine Base ◽  
Heavy Duty ◽  
Base Form ◽  
Static Yield ◽  
High Fields ◽  
Er Fluids ◽  
Er Fluid ◽  
A Current

Currents drawn under high fields often present practical limitations to electrorheological (ER) fluids usefulness. For heavy-duty applications where large torques have to be transmitted, the power consumption of a ER fluid can be considerable, and for such uses a current density of ~100μ A cm -2 is often taken as a practical upper limit. This investigation was conducted into designing a fluid which has little extraneous conductance and therefore would demand less current. Selected semi-conducting polymers provide effective substrates for ER fluids. Such polymers are soft insoluble powdery materials with densities similar to dispersing agents used in ER formulations. Polyaniline is a semi-conducting polymer and can be used as an effective ER substrate in its emeraldine base form. In order to provide an effective ER fluid which requires less current polyaniline was coated with an insulating polymer. The conditions for coating was established for lauryl and methyl methacrylate. Results from static yield measurements indicate that ER fluids containing coated polyaniline required less current than uncoated polyaniline i.e. 0.5μ A cm -2. The generic type of coating was also found to be important.

scholarly journals A study of the static yield stress in a binary Lennard-Jones glass

2004 ◽  
Vol 120 (6) ◽  
pp. 2788-2801 ◽  
Author(s):  
F. Varnik ◽  
L. Bocquet ◽  
J.-L. Barrat
Keyword(s):  
Yield Stress ◽  
Lennard Jones ◽  
Static Yield ◽  
Static Yield Stress
Sign in / Sign up

Export Citation Format

Share Document