Effect of Particle Size and Distribution on the Viscosity of a Model Electrorheological (ER) Fluid

1999 ◽  
Author(s):  
Ying Chen ◽  
Hans Conrad
Keyword(s):  
Particle Size ◽  
Reasonable Agreement ◽  
Volume Fraction ◽  
Silicone Oil ◽  
Zero Field ◽  
Effect Of Particle Size ◽  
Er Fluids ◽  
Er Fluid ◽  
Modified Equation ◽  
Single Size

Abstract The zero-field viscosity of model ER fluids consisting of glass beads in silicone oil was determined as a function of average particles size (D¯ = 3–75 μm), volume fraction (ϕ = 0.1–0.3) and bimodal mixtures of two sizes. The viscosity increased with ϕ and decreased with D¯. The viscosity of the suspensions ηs in all cases was described reasonably well by the following relation:ηs=ηs,o(ϕ)+b(ϕ)D¯2/D¯3 where ηs,o(ϕ) and b(ϕ) are constants which increase with ϕ. Reasonable agreement with the Mooney crowding equation occurred for the single size particles, giving for the crowding factor k = 1.3 + 1.5/D¯. For ϕ < 0.2 the viscosity of the bimodal mixtures could be described by a modification of the Mooney equationηsηo=exp(2.76ϕ11-k1ϕ1)exp(2.76ϕ21-k2ϕ2) where ηo is the viscosity of the silicone oil, ϕi the volume fraction of each particle size Di and ki the normal crowding factor for that size. At ϕ = 0.3 the measured values of ηs for the bimodal mixtures became appreciably larger than those calculated from the modified equation. The decrease in particle size leads to both an increase in surface area of the particles per unit volume of the suspension and to a decrease in spacing (crowding); both factors probably contributed to the increase in ηs.

Computer Simulation of Electrorheological Fluids in the Binary System of Particle Size

1999 ◽  
Vol 13 (14n16) ◽  
pp. 1822-1827
Author(s):  
Yasushige Mori ◽  
Tetsu Tsunamoto ◽  
Hitoshi Nakayama
Keyword(s):  
Computer Simulation ◽  
Particle Size ◽  
Shear Stress ◽  
Fine Particles ◽  
Volume Fraction ◽  
Dielectric Polarization ◽  
Uniform Size ◽  
Polarization Model ◽  
Effect Of Particle Size ◽  
Er Fluids

One of the typical electrorheological (ER) fluids consists of suspension of fine particles in the liquid of low dielectric constant. Particles for ER fluids generally have a size distribution, and some experimental results were reported which showed the effect of particle size on the shear stress of ER fluids. On the other hand, the simulation by dielectric polarization model concluded that the shear stress calculated did not depend on the particle size under the same volume fraction of particles. In order to understand the effect of particle size, the two dimensional computer simulation was carried out for a system containing particles of different size, by using a model similar to that reported by Klingenberg et al. It was found that the shear stress of uniform size system did not depend on the particle size. When small and large particles, with the diameter ratio of 1:2, were mixed in equal numbers of particles, the chain-like clusters consisiting of both sizes of particles were formed. The shear stress and the response time of the binary size system were close to those of uniform size system, if the total volume fraction of particles was kept constant.

Effect of Particle Size of W-Brass Composite on Gamma-Ray Absorption Coefficient

2015 ◽  
Vol 754-755 ◽  
pp. 19-23
Author(s):  
Kahtan S. Mohammed ◽  
Ali Basheer Azeez ◽  
Mohd Mustafa Al Bakri Abdullah ◽  
Kamarudin Hussin ◽  
Azmi B. Rahmat
Keyword(s):  
Particle Size ◽  
Absorption Coefficient ◽  
Gamma Ray ◽  
Vickers Microhardness ◽  
Volume Fraction ◽  
Milled Powder ◽  
Microstructural Characterization ◽  
Effect Of Particle Size ◽  
Gamma Ray Attenuation ◽  
Attenuation Values

In this study, the dependence of gamma-ray absorption coefficient on amount and particle size of tungsten (W) in W-brass sintered compacts was investigated. To attain this goal, two sets of different W wt. % were prepared (W 65wt. %, W75wt. % and W85 wt. %). One set has compacts of as received powder and the other set has compacts of ball milled powder. The results showed that gamma-ray attenuation coefficient is inversely proportional to the particle size of the tested sintered compacts and directly proportional to the W content. Vickers microhardness, attenuation properties and microstructural characterization were carried out on the sintered samples. The attenuation test was conducted using gamma spectrometer with Genie 200 software. The samples of ball milled powder and of the highest volume fraction of W showed the highest hardness and attenuation values.

SYNTHESIS AND VISCOELASTIC BEHAVIORS OF POLY(ANILINE-CO-O-ETHOXYANILINE) PARTICLES SUSPENDED ELECTRORHEOLOGICAL FLUID

2001 ◽  
Vol 15 (06n07) ◽  
pp. 649-656 ◽  
Author(s):  
H. J. CHOI ◽  
J. W. KIM ◽  
M. S. SUH ◽  
M. J. SHIN ◽  
K. TO
Keyword(s):  
Particle Size ◽  
Silicone Oil ◽  
Loss Modulus ◽  
Chemical Oxidation ◽  
Steady Shear ◽  
Rheological Parameters ◽  
Linear Viscoelastic Region ◽  
Linear Viscoelastic ◽  
Er Fluids ◽  
Poly Aniline

Copolyanilines are synthesized by a chemical oxidation of aniline and o-ethoxyaniline with various molar ratios in an acidic media, and then characteristics of these polymers such as chemical structure, particle size and the particle size distribution were examined by using FT-IR, SEM and particle size analyzer, respectively. Suspensions of copolyaniline containing ethoxy group, namely poly(aniline-co-o-ethoxyaniline), in silicone oil have been investigated as one of many potential candidates for dry-base electrorheological (ER) fluid systems. Rotational rheometer (Physica) equipped with a high voltage generator was used to characterize the rheological properties of ER fluids from both steady shear and dynamic tests. From the steady shear experiment, we obtained flow properties and found that ER fluids exhibited the yield phenomenon. On the other hand, viscoelastic property was also obtained from the dynamic experiment. Since viscoelastic properties for ER fluids are mainly dominated by the particle chain structure, the state at different time scale was analyzed from the rheological parameters such as storage modulus (G'), loss modulus (G'') and tan δ. We conducted a strain amplitude sweep at 1 Hz under an applied electric field to determine a linear viscoelastic region first. The G' and G'' were then measured by a frequency sweep from 0.1 to 100 Hz in the linear viscoelastic region.

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.

HIGH PERFORMANCE CALCIUM TITANATE NANOPARTICLE ER FLUIDS

2005 ◽  
Vol 19 (07n09) ◽  
pp. 1110-1113 ◽  
Author(s):  
XUEZHAO WANG ◽  
RONG SHEN ◽  
WEIJIA WEN ◽  
KUNQUAN LU
Keyword(s):  
High Performance ◽  
Silicone Oil ◽  
Calcium Titanate ◽  
Hydroxyl Group ◽  
Long Term Stability ◽  
Dc Electric Field ◽  
Wet Chemical ◽  
Er Fluids ◽  
Er Fluid

A type of calcium titanate (CTO) nanoparticles was synthesized by means of wet chemical method [1] without coating on the particles. The CTO/silicone oil ER fluid exhibits excellent electrorheological properties: high shear stress (~50-100 kPa ) under dc electric field, a low current density (less than 2μA/cm2 at 5kV/mm), and long term stability against sedimentation. Although there are not special additives in the ER fluids, it is found from the chemical analysis that a trace of alkyl group, hydroxyl group, carbonyl group and some ions is remained in the particles which may dominate the ER response.

ELECTRORHEOLOGICAL BEHAVIOR OF CHITOSAN DERIVATIVE SUSPENSIONS

2001 ◽  
Vol 15 (06n07) ◽  
pp. 1025-1032 ◽  
Author(s):  
Ung-su Choi ◽  
Byeng-gil Ahn ◽  
Oh-kwan Kwon
Keyword(s):  
Electric Field ◽  
Volume Fraction ◽  
Silicone Oil ◽  
Flow Behavior ◽  
Chitosan Derivative ◽  
Shear Yield Stress ◽  
Bingham Flow ◽  
Shear Yield ◽  
The Difference ◽  
Er Fluid

The electrorheological (ER) behavior of chitosan and chitosan phosphate suspensions in silicone oil was investigated. Chitosan and chitosan phosphate suspensions showed a typical ER response (Bingham flow behavior) upon application of an electric field. However, chitosan phosphate suspension exhibited excellent shear yield stress compared with chitosan suspension. The difference in behavior results from the difference in the conductivity of the chitosan and chitosan phosphate particles due to their degree of the polarizability. The shear stress for chitosan and chitosan phosphate suspensions showed a linear dependence on the volume fraction of particles. The values of structure factor, A s obtained 1 and 3~4 for chitosan and chitosan phosphate suspensions and it may be due to the formation of single-row chains and multiple chains upon application of the electric field. Throughtout the experimental results, chitosan and chitosan phosphate suspensions were shown to be an ER fluid.

INFLUENCE OF PARTICLE SIZE ON THE DYNAMIC STRENGTH OF ELECTRORHEOLOGICAL FLUIDS

1994 ◽  
Vol 08 (20n21) ◽  
pp. 2835-2853 ◽  
Author(s):  
YUNG-HUI SHIH ◽  
HANS CONRAD
Keyword(s):  
Particle Size ◽  
Electric Field ◽  
Volume Fraction ◽  
Low Voltage ◽  
Silicone Oil ◽  
Particle Surface ◽  
Dynamic Strength ◽  
Columnar Structure ◽  
Particle Surface Area ◽  
Polarization Component

The electrical properties, rheology and structure of model ER fluids consisting of glass beads in silicone oil were investigated as a function of electric field E (0–4 kV/mm ), particle size D (6–100 µ m ) and shear rate [Formula: see text]. The conductivity of the suspensions was 3 orders of magnitude greater than that of the host oil at E ⋝ 1 kV/mm ; their low-voltage d.c. permittivity was about 1.35 times larger. The flow stress of the suspensions was given by [Formula: see text] where τE is the polarization component and τ vis the viscous component. The linear dependence of τE on E was attributed to dipole saturation. The observed opposing effects of D and [Formula: see text] on τE were concluded to result from their respective influence on the strength of the columnar structure normally produced by the electric field and its fragmentation during shear. The constant C1 was in agreement with the Einstein equation for the effect of volume fraction of particles on the viscosity of suspensions. The parameter C2/D was concluded to reflect either the effect of particle surface area on viscosity or a polydispersion effect. The present results did not correlate with the Mason number as normally formulated, but did when it was appropriately modified.

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