Extension of a Classic Thin Double Layer Polarization Theory of Colloidal Suspensions to Include the Stagnant Layer Conductivity

2011 ◽  
Vol 115 (29) ◽  
pp. 8996-9004 ◽  
Author(s):  
Constantino Grosse
Keyword(s):  
Double Layer ◽  
Colloidal Suspensions ◽  
Polarization Theory

Nanoparticle Transport Through Boundaries of Nanoporous Structures

2012 ◽  
Author(s):  
T. S. Mahadevan ◽  
M. Milosevic ◽  
M. Kojic ◽  
F. Hussain ◽  
N. Kojic ◽  
...  
Keyword(s):  
Double Layer ◽  
Colloidal Suspensions ◽  
Characteristic Size ◽  
Dlvo Theory ◽  
Debye Screening Length ◽  
Particle Interactions ◽  
Complex Environments ◽  
Surface Charges ◽  
Nanoparticle Transport ◽  
Counter Ions

In transport phenomena involving colloidal nanoparticle (NP) suspensions in complex environments, the inter particle interactions play an important role especially when the sizes of the confining environments approaches the particle sizes. Specific examples of such systems are encountered in NP transport through nanochannels used in drug delivery and nanofluidic cooling[1–5]. In ionic colloidal suspensions like the ones encountered in the above applications, the NPs acquire characteristic surface charges which results in a surface potential and a double layer of co- and counter-ions from the solution. DLVO theory predicts the interaction energy resulting from the double layer to be [6]:(1)Wr=64πkBTRρ∞γ2κ2exp-κr where r is the separation between NP surfaces, and R is the radius of the NP, ρ∞ is the concentration of ions in the suspension, κ−1 is the Debye screening length (characteristic size of the double layer) and kB and T are the Boltzmann constant and the temperature. As κ−1 approaches the size range of the particles, the interactions amongst the particles may span several times the particle size and contributes to particle diffusion.

scholarly journals On electrical effects due to sound waves in colloidal suspensions

1951 ◽  
Vol 207 (1090) ◽  
pp. 329-342 ◽  
Keyword(s):  
Double Layer ◽  
Colloidal Particles ◽  
Wave Train ◽  
Wave Length ◽  
Colloidal Suspensions ◽  
Exact Expression ◽  
Particle Radius ◽  
Potential Difference ◽  
Sound Waves ◽  
Leading Term

In this paper, the electrical effects accompanying the propagation of sound waves through a suspension of spherical colloidal particles in an electrolyte are examined. It is shown that, for charged colloidal particles, differences of potential arise between different points in the wave train. A general method is given for obtaining the amplitude of the potential difference in the case when the thickness of the double-layer surrounding the particles is small compared with the particle radius, as a power series in the zeta-potential and the leading term in this series is evaluated, so that the results will be adequate for zeta-potentials which are not too large. An exact expression is obtained for the case when the thickness of the double-layer is very much greater than the particle radius but still much less than the mean separation. An attempt is also made to estimate the effect for intermediate values of the double-layer thickness. The amplitude of the potential difference decreases with increasing concentration of electrolyte and, when measured between points a half-wave-length apart, is substantially independent of the frequency of the sound waves, except at very high frequencies. The results are compared with the experimental data.

A metal- coating Chamber for High-Resolution Cryo-SEM

1990 ◽  
Vol 48 (1) ◽  
pp. 418-419
Author(s):  
John G. Sheehan
Keyword(s):  
High Resolution ◽  
Colloidal Suspensions ◽  
Metal Coating ◽  
Colloidal Interactions ◽  
Amorphous Ice ◽  
High Vapor ◽  
Particulate Coatings ◽  
20 Nm ◽  
Film Nucleation ◽  
Coating Chamber

Improvements in particulate coatings for printable paper require understanding mechanisms of colloidal interactions in paper coating suspensions. One way to deduce colloidal interactions is to mage particle spacings and orientations at high resolution with cryo-SEM. Recent improvements in cryo-SEM technique have increased resolution enough to image particles in coating paints,vhich are sometimes smaller than 100 nm. In this report, a metal-coating chamber is described for preparation of colloidal suspensions for cryo-SEM at resolution down to 20 nm. It was found that etching is not necessary to achieve this resolution.A 120 K cryo-SEM sample will remain in an SEM for hours without noticeable condensation of imorphous ice. This is due to the high vapor pressure of vapor-condensed amorphous ice, measured by Kouchi. However, clean vacuum is required to coat samples with the thinnest possible continuous metal films which are required for high magnification SEM. Vapor contaminants, especially hrydrocarbons, are known to interfere with thin-film nucleation and growth so that more metal is needed to form continuous films, and resolution is decreased. That is why the metal-coating chamber in fig. 1 is designed for the cleanest possible vacuum. Feedthroughs for the manipulator md the shutter, which are operated during metal coating, are sealed with leak-proof stainless-steel Dellows. The transfer rod slides through a baseplate feedthrough that is double o-ring sealed.

Cracking at the fold in double layer coated paper: the influence of latex and starch composition

TAPPI Journal ◽  
2019 ◽  
Vol 18 (2) ◽  
pp. 93-99
Author(s):  
SEYYED MOHAMMAD HASHEMI NAJAFI ◽  
DOUGLAS BOUSFIELD, ◽  
MEHDI TAJVIDI
Keyword(s):  
Mechanical Properties ◽  
Double Layer ◽  
Starch Content ◽  
Single Layer ◽  
Double Layers ◽  
Coated Paper ◽  
Coated Papers ◽  
Coating Layers ◽  
Scanned Images ◽  
Packaging Paper

Cracking at the fold of publication and packaging paper grades is a serious problem that can lead to rejection of product. Recent work has revealed some basic mechanisms and the influence of various parameters on the extent of crack area, but no studies are reported using coating layers with known mechanical properties, especially for double-coated systems. In this study, coating layers with different and known mechanical properties were used to characterize crack formation during folding. The coating formulations were applied on two different basis weight papers, and the coated papers were folded. The binder systems in these formulations were different combinations of a styrene-butadiene latex and mixtures of latex and starch for two different pigment volume concentrations (PVC). Both types of papers were coated with single and double layers. The folded area was scanned with a high-resolution scanner while the samples were kept at their folded angle. The scanned images were analyzed within a constant area. The crack areas were reported for different types of papers, binder system and PVC values. As PVC, starch content, and paper basis weight increased, the crack area increased. Double layer coated papers with high PVC and high starch content at the top layer had more cracks in comparison with a single layer coated paper, but when the PVC of the top layer was low, cracking area decreased. No measurable cracking was observed when the top layer was formulated with a 100% latex layer.

A Survey on Crypto-Steganographic Schemes and A Use Case in Healthcare System

2019 ◽  
Vol 1 (2) ◽  
pp. 25-33
Author(s):  
Mei Ling Phang ◽  
Swee Huay Heng
Keyword(s):  
Social Networking ◽  
Information Sharing ◽  
Healthcare System ◽  
Double Layer ◽  
21St Century ◽  
Electronic Devices ◽  
Third Party ◽  
Use Case ◽  
Comparison Analysis ◽  
Information Assets

Information sharing has become prevalent due to the expansion of social networking in this 21st century. However, electronic devices are vulnerable to various kinds of attacks. Information might be disclosed, modified and accessed by an unauthorised third party which consequently leads to the breach of confidentiality, integrity and availability of the information. Therefore, it is of utmost importance to employ the technology of cryptography and steganography to protect information assets. Cryptography and steganography have weaknesses when they are working alone. Therefore, crypto-steganography, the combination of cryptography and steganography are introduced to overcome the weaknesses in order to provide a double layer of security and protection. This paper provides a general overview of steganography and cryptography as well as a comparison analysis of different crypto-steganographic schemes. A secure crypto-steganographic system for healthcare is then developed with the implementation and integration of the secure crypto-steganographic scheme proposed by Juneja and Sandhu. This healthcare system enables users to store and deliver message in a more secure way while achieving the main goals of both cryptography and steganography.

Sign in / Sign up

Export Citation Format

Share Document