scholarly journals Short-time diffusion of charge-stabilized colloidal particles: generic features

2010 ◽  
Vol 43 (5) ◽  
pp. 970-980 ◽  
Author(s):  
Marco Heinen ◽  
Peter Holmqvist ◽  
Adolfo J. Banchio ◽  
Gerhard Nägele
Keyword(s):  
Experimental Data ◽  
Colloidal Particles ◽  
Stokesian Dynamics ◽  
Self Diffusion ◽  
Wide Range ◽  
Theoretical Predictions ◽  
Dynamics Simulations ◽  
Short Time ◽  
Hydrodynamic Function

Analytical theory and Stokesian dynamics simulations are used in conjunction with dynamic light scattering to investigate the role of hydrodynamic interactions in short-time diffusion in suspensions of charge-stabilized colloidal particles. The particles are modeled as solvent-impermeable charged spheres, repelling each otherviaa screened Coulomb potential. Numerical results for self-diffusion and sedimentation coefficients, as well as hydrodynamic and short-time diffusion functions, are compared with experimental data for a wide range of volume fractions. The theoretical predictions for the generic behavior of short-time properties obtained from this model are shown to be in full accord with experimental data. In addition, the effects of microion kinetics, nonzero particle porosity and residual attractive forces on the form of the hydrodynamic function are estimated. This serves to rule out possible causes for the strikingly small hydrodynamic function values determined in certain synchrotron radiation experiments.

General Trend of Negative Transference Number in Li Salt/Ionic Liquid Mixtures

2019 ◽  
Author(s):  
Nicola Molinari ◽  
Jonathan P. Mailoa ◽  
Boris Kozinsky
Keyword(s):  
Ionic Liquid ◽  
Transference Number ◽  
Liquid Mixtures ◽  
Single Linkage ◽  
Self Diffusion ◽  
Wide Range ◽  
Single Linkage Cluster ◽  
Concentrated Solution ◽  
The One ◽  
Dynamics Simulations

We show that strong cation-anion interactions in a wide range of lithium-salt/ionic liquid mixtures result in a negative lithium transference number, using molecular dynamics simulations and rigorous concentrated solution theory. This behavior fundamentally deviates from the one obtained using self-diffusion coefficient analysis and agrees well with experimental electrophoretic NMR measurements, which accounts for ion correlations. We extend these findings to several ionic liquid compositions. We investigate the degree of spatial ionic coordination employing single-linkage cluster analysis, unveiling asymmetrical anion-cation clusters. Additionally, we formulate a way to compute the effective lithium charge that corresponds to and agrees well with electrophoretic measurements and show that lithium effectively carries a negative charge in a remarkably wide range of chemistries and concentrations. The generality of our observation has significant implications for the energy storage community, emphasizing the need to reconsider the potential of these systems as next generation battery electrolytes.<br>

SCALING OF THE TIME-DEPENDENT SELF-DIFFUSION COEFFICIENT

1995 ◽  
Vol 09 (04n05) ◽  
pp. 469-494 ◽  
Author(s):  
PEP ESPAÑOL ◽  
IGNACIO ZÚÑIGA
Keyword(s):  
Diffusion Coefficient ◽  
Colloidal Particles ◽  
Time Dependent ◽  
Short Time Scale ◽  
Transient Effects ◽  
Self Diffusion ◽  
Open Questions ◽  
Brownian Particles ◽  
Short Time ◽  
Self Diffusion Coefficient

The advent of the new light scattering technique of Diffusing Wave Spectroscopy has aroused great interest on the very short time scale dynamics of colloidal particles in suspension. Here we review some advances in the experimental, computer simulation and theoretical fronts on the problem of the dynamics of Brownian particles at time scales where hydrodynamic transient effects become very important. We also present some open questions regarding the scaling of the time-dependent self-diffusion coefficient and propose possible ways of attacking them.

General Trend of Negative Transference Number in Li Salt/Ionic Liquid Mixtures

2019 ◽  
Author(s):  
Nicola Molinari ◽  
Jonathan P. Mailoa ◽  
Boris Kozinsky
Keyword(s):  
Ionic Liquid ◽  
Transference Number ◽  
Liquid Mixtures ◽  
Single Linkage ◽  
Self Diffusion ◽  
Wide Range ◽  
Single Linkage Cluster ◽  
Concentrated Solution ◽  
The One ◽  
Dynamics Simulations

We show that strong cation-anion interactions in a wide range of lithium-salt/ionic liquid mixtures result in a negative lithium transference number, using molecular dynamics simulations and rigorous concentrated solution theory. This behavior fundamentally deviates from the one obtained using self-diffusion coefficient analysis and agrees well with experimental electrophoretic NMR measurements, which accounts for ion correlations. We extend these findings to several ionic liquid compositions. We investigate the degree of spatial ionic coordination employing single-linkage cluster analysis, unveiling asymmetrical anion-cation clusters. Additionally, we formulate a way to compute the effective lithium charge that corresponds to and agrees well with electrophoretic measurements and show that lithium effectively carries a negative charge in a remarkably wide range of chemistries and concentrations. The generality of our observation has significant implications for the energy storage community, emphasizing the need to reconsider the potential of these systems as next generation battery electrolytes.<br>

scholarly journals On the role of the Knudsen layer in rapid granular flows

2007 ◽  
Vol 585 ◽  
pp. 73-92 ◽  
Author(s):  
J. E. GALVIN ◽  
C. M. HRENYA ◽  
R. D. WILDMAN
Keyword(s):  
Heat Flux ◽  
Granular Flows ◽  
Order Theory ◽  
Knudsen Layer ◽  
Navier Stokes ◽  
Experimental Systems ◽  
Theoretical Predictions ◽  
Flux Measurements ◽  
Dynamics Simulations

A combination of molecular dynamics simulations, theoretical predictions and previous experiments are used in a two-part study to determine the role of the Knudsen layer in rapid granular flows. First, a robust criterion for the identification of the thickness of the Knudsen layer is established: a rapid deterioration in Navier–Stokes order prediction of the heat flux is found to occur in the Knudsen layer. For (experimental) systems in which heat flux measurements are not easily obtained, a rule-of-thumb for estimating the Knudsen layer thickness follows, namely that such effects are evident within 2.5 (local) mean free paths of a given boundary. Secondly, comparisons of simulation and experimental data with Navier–Stokes order theory are used to provide a measure as to when Knudsen-layer effects become non-negligible. Specifically, predictions that do not account for the presence of a Knudsen layer appear reliable for Knudsen layers collectively composing up to 20% of the domain, whereas deterioration of such predictions becomes apparent when the domain is fully comprised of the Knudsen layer.

The role of charge on the diffusion of solutes and nanoparticles (silicon nanocrystals, nTiO2, nAu) in a biofilm

2013 ◽  
Vol 10 (1) ◽  
pp. 34 ◽  
Author(s):  
Mahmood Golmohamadi ◽  
Rhett J. Clark ◽  
Jonathan G. C. Veinot ◽  
Kevin J. Wilkinson
Keyword(s):  
Carboxylic Acid ◽  
Diffusion Coefficients ◽  
Electrostatic Interactions ◽  
Emerging Contaminants ◽  
Correlation Spectroscopy ◽  
Fluorescence Correlation ◽  
Self Diffusion ◽  
Wide Range ◽  
Tetramethylrhodamine Methyl Ester

Environmental context The mobility and bioavailability of both contaminants and nutrients in the environment depends, to a large extent, on their diffusion. Because the majority of microorganisms in the environment are embedded in biofilms, it is essential to quantify diffusion in biofilms in order to evaluate the risk of emerging contaminants, including nanomaterials and charged solutes. This study quantifies diffusion, in a model environmental biofilm, for a number of model contaminants of variable size and charge. Abstract The effect of solute and biofilm charge on self-diffusion (Brownian motion) in biofilms is examined. Diffusion coefficients (D) of several model (fluorescent) solutes (rhodamine B; tetramethylrhodamine, methyl ester; Oregon Green 488 carboxylic acid, succinimidyl ester and Oregon Green 488 carboxylic acid) and nanoparticles (functionalised silicon, gold and titanium) were determined using fluorescence correlation spectroscopy (FCS). Somewhat surprisingly, little effect due to charge was observed on the diffusion measurements in the biofilms. Furthermore, the ratio of the diffusion coefficient in the biofilm with respect to that in water (Db/Dw) remained virtually constant across a wide range of ionic strengths (0.1–100mM) for both negatively and positively charged probes. In contrast, the self-diffusion coefficients of nanoparticles with sizes >10nm greatly decreased in the biofilms with respect to those in water. Furthermore, much larger nanoparticles (>66nm) appeared to be completely excluded from the biofilms. The results indicated that for many oligotrophic biofilms in the environment, the diffusion of solutes and nanoparticles will be primarily controlled by obstruction rather than electrostatic interactions. The results also imply that most nanomaterials will become significantly less mobile and less bioavailable (to non-planktonic organisms) as they increase in size beyond ~10nm.

Investigation of Stator Induced Unsteadiness on a Centrifugal Impeller Using a Mach-Independent Non-Linear Harmonic Method

2015 ◽  
Author(s):  
Benoît Tartinville ◽  
Charles Hirsch
Keyword(s):  
Experimental Data ◽  
Computing Time ◽  
Computational Effort ◽  
Centrifugal Impeller ◽  
Flow Solver ◽  
Wide Range ◽  
Non Linear ◽  
Unsteady Simulation ◽  
Number Flow ◽  
Short Time

The objective of this paper is to numerically investigate the unsteadiness generated by a bladed diffuser on an upstream centrifugal impeller. The Non-Linear Harmonic (NLH for short) time-spectral method has been retained here. The major advantage of such a method is that it requires much less computational effort than a standard unsteady simulation. In order to further reduce the computing time, the NLH method has been extended to low speed flows by using a preconditioning technic. Therefore, the NLH method can be accurately applied to any Mach number flow and even to purely incompressible fluids. This extension of the flow solver has been validated on a wide range of simple test cases at various reduce frequencies. Solutions have been compared to purely unsteady approach and also to experimental data. In a second step, the NLH method has been applied to a centrifugal impeller and its downstream diffuser. Numerical results have been analyzed and compared to the available experimental data showing the significant influence of the downstream diffuser on the impeller pressure load.

scholarly journals Micelle stability in water under a range of pressures and temperatures; do both have a common mechanism?

RSC Advances ◽  
2015 ◽  
Vol 5 (86) ◽  
pp. 70005-70009 ◽  
Author(s):  
Yanis Ricardo Espinosa Silva ◽  
J. Raul Grigera
Keyword(s):  
Experimental Data ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Self Assembly ◽  
The Self ◽  
Common Mechanism ◽  
Wide Range ◽  
Dynamics Simulations

Using molecular dynamics simulations, we present a description compatible with experimental data of the self-assembly aggregation of SDS molecules in H2O and D2O for a wide range of pressures and temperatures.

scholarly journals Dependence of the structural parameters and properties of low density polyethylene on the synthesis conditions

1999 ◽  
Vol 64 (10) ◽  
pp. 577-587
Author(s):  
Dragoslav Stoiljkovic ◽  
Radmila Radicevic ◽  
Milovan Jankovic
Keyword(s):  
Experimental Data ◽  
Structural Parameters ◽  
Low Density Polyethylene ◽  
Low Density ◽  
Structure And Properties ◽  
Synthesis Conditions ◽  
Wide Range ◽  
Theoretical Predictions ◽  
Mathematical Relationships ◽  
Polymerization Conditions

In a previous publicaitons from the authors.laboratotry a method was developed to predict the structure and properties of low density polyethylene (PE-LD) that could be obtained over a very wide range of polymerization conditions. The method was proved using experimental data from the literature. However, some shortcomings of the method were noticed. The aim of this work was to overcome the shortcomings and to enable the better manipulation of experimental data using a computer. A computer program has been developed to establish the mathematical relationships between ethylene entropy and the structural parameters and density of Pe-LD. All available experimental data (more than 300 experimental points) have elaborated and confirmed our mathematical models and our theoretical predictions.

scholarly journals Transport Properties of the Lennard-Jones Truncated and Shifted Fluid from Non-equilibrium Molecular Dynamics Simulations

2021 ◽  
Author(s):  
Martin P. Lautenschläger ◽  
Hans Hasse
Keyword(s):  
Molecular Dynamics ◽  
Simulation Method ◽  
Self Diffusion ◽  
Lennard Jones ◽  
Wide Range ◽  
Data Correlations ◽  
Non Equilibrium Molecular Dynamics ◽  
Dynamics Simulations ◽  
Good Agreement ◽  
Non Equilibrium

The thermal conductivity λ, shear viscosity η, and self-diffusion coefficient D of the Lennard-Jones fluid truncated and shifted at the cut-off radius rc=2.5σ (LJTS fluid) are determined for a wide range of liquid and supercritical states (T*=[0.6,10.0] and ρ*=[0.2,1.2]). The simulations are carried out using a non-equilibrium molecular dynamics (NEMD) method that was introduced recently and in which two gradients are applied simultaneously. It is shown that the two-gradient method is well-suited for studies of liquid and supercritical states. Data for λ, η, and D for about 350 state points are reported. Two variants of the simulation method, which differ in the accuracy and efficiency, are explored and found to yield consistent data. Correlations for λ, η, and Dρ of the LJTS fluid are provided. The data and the correlations are compared to literature data of Lennard-Jones (LJ) type fluids and good agreement is observed. The truncation of the LJ potential causes a slight increase in D, while it has no significant effect on λ and η.

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