Electrokinetic instabilities of non-dilute colloidal suspensions

2009 ◽  
Vol 619 ◽  
pp. 331-365 ◽  
Author(s):  
GURU NAVANEETHAM ◽  
JONATHAN D. POSNER
Keyword(s):  
Electrical Conductivity ◽  
Electric Fields ◽  
Colloidal Particles ◽  
Volume Fraction ◽  
Flow Instability ◽  
Colloidal Suspensions ◽  
Critical Conditions ◽  
Scaling Analysis ◽  
Average Particle ◽  
Wide Range

An experimental investigation of electrokinetic instabilities (EKIs) of non-dilute colloidal suspensions in microchannels is presented. The addition of charged colloidal particles to a solution can alter the solution's electrical conductivity and permittivity as well as the average particle electrophoretic mobility. In this work, a colloidal (500 nm polystyrene) volume fraction gradient is achieved at the intersection of a Y-shaped polydimethylsiloxane (PDMS) microchannel. The flow becomes unstable when the electroviscous stretching and folding of the conductivity and permittivity interfaces exceed the dissipative effects of viscous forces and particle diffusion. The suspension conductivity as a function of the particle volume fraction is presented. The critical conditions required for flow instability are measured along with a scaling analysis which shows that the flow becomes unstable due to a coupling of applied electric fields and the electrical conductivity and permittivity gradients in the flow. The flow becomes unstable at a critical electric Rayleigh number of Rae = 1.8 × 105 for a wide range of applied electric fields spanning three orders of magnitude and colloid volume fractions varying two orders of magnitude. EKIs of non-dilute colloidal suspensions may be important for applications such as the electrophoretic deposition of micropatterned colloidal assemblies, electrorheological devices and on-chip electrokinetic (EK) manipulation of colloids.

DESIGN OF A SAMPLE HOLDER FOR LOW TEMPERATURE ELECTRICAL CONDUCTIVITY MEASUREMENTS

2013 ◽  
Vol 22 ◽  
pp. 741-744 ◽  
Author(s):  
YADUNATH SINGH
Keyword(s):  
Electrical Conductivity ◽  
Low Temperature ◽  
Electric Fields ◽  
Low Cost ◽  
Ambient Pressure ◽  
Liquid Nitrogen Temperature ◽  
Sample Holder ◽  
Ac Electrical Conductivity ◽  
Switching Phenomenon ◽  
Wide Range

Both DC and AC electrical conductivity of materials provide a number of valuable informationon the nature of current carriers, 3-D effects, scattering by defects and impurities, formation of CDW, soliton propagation, non – linear and switching phenomenon and other characters pertaining to these compounds. These measurements are therefore carried out over a wide range of temperature, pressure, electric fields and impurity concentrations. Besides these, the low temperature studies of the materials are performed to determine Optical and Magnetic properties and etc. Therefore, a suitable sample holder is required to perform these studies with low temperature variations. In this paper, we report a design of such a suitable and simple sample holder, which can work up to liquid nitrogen temperature (77 K). This model is easy to fabricate, low cost, more efficient with less wastage in terms of liquid gases than other models. This model can be used for both low temperature dependent electrical conductivity at ambient pressure and clamped high pressure measurements within the given range

scholarly journals Preparation and Investigation of Intelligent Polymeric Nanocapsule for Enhanced Oil Recovery

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1093 ◽  
Author(s):  
Fang Shi ◽  
Jingchun Wu ◽  
Bo Zhao
Keyword(s):  
Particle Size ◽  
Enhanced Oil Recovery ◽  
Oil Recovery ◽  
Colloidal Particles ◽  
Critical Concentration ◽  
Average Particle Size ◽  
Average Particle ◽  
Assembly Method ◽  
Recovery Capacity ◽  
Wide Range

Micro-/nanomotors colloidal particles have attracted increasing interest as composite surfactants, owing to the combined advantages of both Janus solid surfactants and micro-/nanomotors. Here we put micro-/nanomotors colloidal particles into hollow polymeric micro-encapsulates. An intelligent polymeric nanocapsule was prepared for enhanced oil recovery by the self-assembly method. The particle size range of the polymeric capsule can be controlled between 20 to 1000 nm by adjusting the cross-linking thickness of the capsule’s outer membrane. The average particle size of polymeric capsules prepared in the study was 300 nm. The structure and properties of the Intelligent polymeric nanocapsule was characterized by a wide range of technics such as Fourier transform infrared spectroscopy, scanning electron microscopy by laser diffraction, fluorescence microscopy, pendant drop tensiometer, laser particle size instrument, and interface tension analyzer. It was found that the intelligent polymeric nanocapsule exhibited significant interfacial activity at the oil-water interface. When the Janus particles’ concentration reached saturation concentration, the adsorption of the amphiphilic nanoparticles at the interface was saturated, and the equilibrium surface tension dropped to around 31 mN/m. When the particles’ concentration reached a critical concentration of aggregation, the Gibbs stability criterion was fulfilled. The intelligent polymeric nanocapsule system has a better plugging and enhanced oil recovery capacity. The results obtained provide fundamental insights into the understanding of the assembly behavior and emulsifying properties of the intelligent polymeric nanocapsule, and further demonstrate the future potential of the intelligent polymeric nanocapsule used as colloid surfactants for enhanced oil recovery applications.

Analysis of the Interplay Between Sedimentation and Thermophoresis in the Presence of Convection in Colloidal Suspensions

2014 ◽  
Author(s):  
Mahmoud DarAssi ◽  
Layachi Hadji
Keyword(s):  
Volume Fraction ◽  
Colloidal Suspension ◽  
Colloidal Suspensions ◽  
Analytical Investigation ◽  
Solid Particles ◽  
Critical Conditions ◽  
Thermophoretic Force ◽  
The Mean ◽  
Set Up ◽  
Rayleigh Benard

We report results of an analytical investigation of linear convection in a nanofluid. We consider a colloidal suspension of solid particles in a Rayleigh-Bénard geometry set-up. The analysis is confined to the mass-dominated convection regime so that results are obtained through analytical means. Our findings depict the dependence of the critical conditions for convection onset as function of several parameters. Thus, the influence of several factors, such as the particle size, the mean volume fraction of particles, the thermophoretic force as well as the sedimentation force, on the instability onset is quantified.

Theoretical Studies of Electromigration in Polycrystalline Metal Stripes

1993 ◽  
Vol 309 ◽  
Author(s):  
Dimitris Maroudas ◽  
Sokrates T. Pantelides
Keyword(s):  
Electric Fields ◽  
Structural Evolution ◽  
Building Blocks ◽  
Scaling Analysis ◽  
Theoretical Studies ◽  
Polycrystalline Metal ◽  
Systematic Analysis ◽  
Wide Range ◽  
Derived Set ◽  
Induced Stresses

AbstractA systematic analysis is presented of the mesoscopic mechanisms that govern the structural evolution of polycrystalline conductors under the action of applied electric fields. A recently derived set of general dynamical mesoscopic equations is specialized to study the behavior of microstructural building blocks. Scaling analysis is presented for the dynamics of the corresponding transport and micromechanical processes associated with a wide range of time scales. Results of numerical simulations are presented for vacancy migration along grain boundaries, evolution of current-induced stresses, surface diffusion, and void stability and growth. The calculated dependence of characteristic times on current density is discussed.

Measured scaling properties of the transition boundaries in a rotating suspension of non-Brownian settling particles

2008 ◽  
Vol 597 ◽  
pp. 233-259 ◽  
Author(s):  
W. R. MATSON ◽  
B. J. ACKERSON ◽  
P. TONG
Keyword(s):  
Phase Diagram ◽  
Scaling Laws ◽  
Volume Fraction ◽  
Scaling Analysis ◽  
Fluid Viscosity ◽  
Cross Sectional ◽  
Theoretical Understanding ◽  
Scaling Properties ◽  
Settling Particles ◽  
Wide Range

Series of concentration and velocity patterns are found for the rotating suspension of non-Brownian settling particles in a completely filled horizontal cylinder. Individual flow states, or phases, are studied using both side and cross-sectional imaging to examine the detailed flow structures. The overall steady-state phase diagram of the system is mapped over a wide range of the rotation rate and fluid viscosity. Effects of the particle radius a, volume fraction φ, and cylinder radius R on the transition boundaries are examined. It is found that the phase diagram of the rotating suspensions can be divided into three regions, in which the transition boundaries obey different scaling laws. A theoretical attempt is made to understand the scaling behaviour of the transition boundaries. The theoretical understanding is achieved at three different levels: a general dimensional consideration, a scaling analysis on the continuum equations of motion, and a specific instability calculation for the transition boundary at the centrifugal limit.

Dynamics of Concentrated Colloidal Suspensions

1989 ◽  
Vol 177 ◽  
Author(s):  
D. A. Weitz ◽  
L. Ye ◽  
Ping Sheng ◽  
J. S. Huang ◽  
D. J. Pine ◽  
...  
Keyword(s):  
Light Scattering ◽  
Acoustic Waves ◽  
Volume Fraction ◽  
Brillouin Scattering ◽  
Particle Diameter ◽  
Colloidal Suspensions ◽  
Colloid System ◽  
Wide Range ◽  
Diffusive Modes ◽  
Pmma Particles

ABSTRACTWe study the dynamics of concentrated colloidal suspensions by measuring the frequency dependent structure factor, S(q,w), using light scattering techniques. We introduce Diffusing Wave Spectroscopy, which extends dynamic light scattering to the multiple scattering regime, allowing us to study the lower frequency, diffusive modes of S(q,w), which reflect the Brownian motion of the particles. We study the behavior of the higher-frequency, propagating modes of S(q,w), which reflect acoustic waves, using Brillouin scattering. To study S(q,w) at low qa, where q is the scattering vector and a the particle diameter, we use inverted micelles, and find that the interactions between the micelles has a dramatic impact on the speed of sound as the volume fraction of micelles increases. To study S(q,w) at large qa, we use index matched PMMA particles, allowing us to measure the dispersion curve of phonons in a hard sphere colloid system. Together, these results provide a measure of S(q, w) over a wide range of q and of w.

Electro-optic observations of electrodynamic band formation in colloidal suspensions

1990 ◽  
Vol 427 (1873) ◽  
pp. 321-330 ◽  
Keyword(s):  
Electric Fields ◽  
Colloidal Particles ◽  
Local Density ◽  
Low Frequency ◽  
Colloidal Suspensions ◽  
Field Vector ◽  
High Concentration ◽  
Band Formation ◽  
Alternating Electric Fields ◽  
Field Lines

In static and low-frequency electric fields, colloidal particles in suspension tend to associate into ‘strings’ or ‘pearl chains’ along the field lines. A phenomenon has been observed in which, under long duration alternating electric fields, colloidal particles in aqueous or conducting media exhibit an electrodynamic instability in which they gather into high concentration ‘bands’ which run essentially perpendicular to the applied field vector. A detailed study is catalogued herein for aqueous suspensions of the discotic mineral kaolinite. A theory has been developed, which embraces the ‘pearl chain’ and ‘band’ formations, demonstrating that one can be formed from the other with increasing frequency and field strength and illustrating the dependence of band formation on electrophoretic mobility as observed in related electro-optical experiments. The value of the phenomenon as a mechanism for concentrating dispersed colloidal particles into regions of very high local density is apparent.

How to use alum with cationic dispersed rosin size

TAPPI Journal ◽  
2016 ◽  
Vol 15 (5) ◽  
pp. 331-335 ◽  
Author(s):  
LEBO XU ◽  
JEREMY MYERS ◽  
PETER HART
Keyword(s):  
Zeta Potential ◽  
Colloidal Particles ◽  
Streaming Potential ◽  
Excessive Amount ◽  
Paper Machine ◽  
Optimum Amount ◽  
Potential Measurement ◽  
Streaming Current ◽  
Wide Range ◽  
Laboratory Results

Retention of cationic dispersed rosin size was studied via turbidity measurements on stock filtrate with different alum and dispersed rosin size dosages. Stock charge characteristics were analyzed using both an analysis of charge demand determined via a streaming current detector and an evaluation of zeta potential of the fibers by streaming potential measurement. The results indicated that an optimum amount of alum existed such that good sizing retention was maintained throughout a wide range of dispersed rosin size dosages. However, when an excessive amount of alum was used and fines and colloidal particles were transitioned from anionic to cationic, the cationic size retention was reduced. Laboratory results were confirmed with a paper machine trial. All data suggested that a stock charge study was necessary to identify optimal alum dosage for a cationic dispersed rosin sizing program.

Critical conditions for organic thread cutting under electric fields

Soft Matter ◽  
2021 ◽  
Author(s):  
Shuai Yin ◽  
Yi Huang ◽  
Teck Neng Wong
Keyword(s):  
Electric Fields ◽  
Capillary Number ◽  
Critical Conditions ◽  
Thread Cutting ◽  
On Demand

Critical conditions with electric capillary number are investigated for triggering the on-demand cutting of an organic thread in a microchannel under electric fields.

scholarly journals Factors Affecting Acoustic Properties of Natural-Fiber-Based Materials and Composites: A Review

Textiles ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 55-85
Author(s):  
Tufail Hassan ◽  
Hafsa Jamshaid ◽  
Rajesh Mishra ◽  
Muhammad Qamar Khan ◽  
Michal Petru ◽  
...  
Keyword(s):  
Sound Absorption ◽  
Natural Fiber ◽  
Volume Fraction ◽  
Fiber Type ◽  
Alkali Treatment ◽  
Acoustic Properties ◽  
Synthetic Fiber ◽  
Sound Insulation ◽  
Factors Affecting ◽  
Wide Range

Recently, very rapid growth has been observed in the innovations and use of natural-fiber-based materials and composites for acoustic applications due to their environmentally friendly nature, low cost, and good acoustic absorption capability. However, there are still challenges for researchers to improve the mechanical and acoustic properties of natural fiber composites. In contrast, synthetic fiber-based composites have good mechanical properties and can be used in a wide range of structural and automotive applications. This review aims to provide a short overview of the different factors that affect the acoustic properties of natural-fiber-based materials and composites. The various factors that influence acoustic performance are fiber type, fineness, length, orientation, density, volume fraction in the composite, thickness, level of compression, and design. The details of various factors affecting the acoustic behavior of the fiber-based composites are described. Natural-fiber-based composites exhibit relatively good sound absorption capability due to their porous structure. Surface modification by alkali treatment can enhance the sound absorption performance. These materials can be used in buildings and interiors for efficient sound insulation.

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