Molecular dynamics study on the zeta potential and shear plane of montmorillonite in NaCl solutions

2021 ◽  
Vol 212 ◽  
pp. 106212
Author(s):  
Huafu Pei ◽  
Siqi Zhang
Keyword(s):  
Molecular Dynamics ◽  
Zeta Potential ◽  
Shear Plane

scholarly journals Interaction Between Edge Dislocation and Single-Layered Graphene in Aluminum Matrix Investigated by Molecular Dynamics Simulation

2022 ◽  
Vol 2152 (1) ◽  
pp. 012034
Author(s):  
Liu Chen ◽  
Zhencheng Li ◽  
Sai Xu ◽  
Aixue Sha
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Mechanical Response ◽  
Aluminum Matrix ◽  
Shear Plane ◽  
Computational Method ◽  
Dynamics Simulation ◽  
Size Dependent ◽  
Graphene Interface ◽  
Dislocation Movement

Abstract The influence of graphene on dislocation movement and subsequent mechanical response of aluminum is investigated by the computational method of molecular dynamics simulation. A Lennard–Jones potential describing Al-C interaction was obtained through ab initio calculation. It was observed that the 2D graphene could reinforce Al matrix similar to the traditional Orowan mechanism. The Al/graphene interface first attract the gliding dislocation to reduce the system energy, which is unlike the grain boundary to repel gliding dislocations through pile-up mechanism. With the increase of stress, dislocation attracted and trapped at the front of graphene could glide along the interface and finally bypass it through climbing when graphene is orientated out of the shear plane. In addition, the strengthening ability of graphene is size dependent, showing a linear relationship between strength increment and graphene size.

A dynamic Stern layer model to explain high salinity zeta potential measurements on sandstones

2020 ◽  
Author(s):  
Philippe Leroy ◽  
Shuai Li
Keyword(s):  
Electrical Properties ◽  
Zeta Potential ◽  
Water Flow ◽  
High Salinity ◽  
Surface Complexation ◽  
Streaming Potential ◽  
Shear Plane ◽  
Mineral Surface ◽  
Stern Layer ◽  
Counter Ions

<p>Exploring the electrical properties of the mineral-water interface for interpreting geophysical electrical measurements is a very challenging work because of the low specific surface area of minerals such as quartz or calcite. Only few methods exist to probe the properties of the electrical double layer (EDL) compensating the surface charge of minerals. Among them, there is the streaming potential (SP) method where the applied water pressure difference generates a pore water flow displacing the mobile counter-ions in excess in the EDL, hence creating a measurable electrical potential difference, the streaming potential. During SP measurements, the exact position of the shear plane from the mineral surface is not known and it is widely accepted that the shear plane is located between the compact Stern layer and the diffuse layer. In our study, we show that the assumption that there is no water flow in the Stern layer has no physical basis for sandstones in contact with a NaCl electrolyte because water molecules around counter-ions in the Stern layer may have bulk-like properties. Using a basic Stern model to simulate surface complexation reactions and considering water flow in the Stern layer, we reproduced the zeta potential measurements on sandstones over a large salinity range from about 10<sup>-2</sup> to 5.5 M NaCl. The “anomalous” high salinity zeta potential data can not be reproduced by a surface complexation model considering water flow only in the diffuse layer. Our ability to explain these measurements suggests that the shear plane may be located between the mineral surface and the Stern layer, i.e. closer to the surface than previously thought, which may have strong implications for the modelling of the surface electrical properties of the minerals.</p>

Stagnant Layer Conduction in Surfactant-Stabilized Hexadecane Emulsion Systems Measured by Electroacoustics

2003 ◽  
Vol 56 (10) ◽  
pp. 1081 ◽  
Author(s):  
Alex M. Djerdjev ◽  
James K. Beattie ◽  
Robert J. Hunter
Keyword(s):  
Zeta Potential ◽  
Size Distribution ◽  
Droplet Size ◽  
Volume Fraction ◽  
Sodium Dodecyl ◽  
Shear Plane ◽  
Surface Conductance ◽  
Zeta Potentials ◽  
Emulsion Droplets ◽  
Dynamic Mobility

Previously reported zeta-potentials calculated from the electroacoustic behaviour of sodium dodecyl sulfate (SDS) stabilized hexadecane emulsion droplets show certain anomalies. These can be resolved when electrical conduction in the stagnant layer behind the shear plane is included in the analysis. If stagnant layer conduction is ignored the addition of salt causes the apparent droplet size to increase and the magnitude of the zeta-potential to show a maximum. When stagnant layer conduction is included the dynamic mobility spectra can be fitted to a constant size distribution independent of the salt concentration with zeta-potentials that decrease as expected with increasing electrolyte concentration. Increasing SDS concentration, before the homogenization process, causes a decrease in droplet size and an increase in the total surface conductance to a constant value corresponding to the saturation of the surface with SDS. It is shown that the surface conductance and particle size distribution of hexadecane at any given volume fraction are functions of the concentration of SDS and the oil volume fraction. The zeta-potential changes log-linearly with added electrolyte and is independent of the SDS concentration or oil volume fraction used during the emulsification process.

scholarly journals Development of a Nanostructured Lipid Carrier (NLC) by a Low-Energy Method, Comparison of Release Kinetics and Molecular Dynamics Simulation

Pharmaceutics ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 531
Author(s):  
Andrea C. Ortiz ◽  
Osvaldo Yañez ◽  
Edison Salas-Huenuleo ◽  
Javier O. Morales
Keyword(s):  
Molecular Dynamics ◽  
Zeta Potential ◽  
Energy Method ◽  
Water Soluble ◽  
Low Energy ◽  
Rhodamine 123 ◽  
Nanostructured Lipid Carrier ◽  
Poorly Water Soluble Drugs ◽  
Water Soluble Drugs ◽  
Poorly Water Soluble

Lipid nanocarriers have a great potential for improving the physicochemical characteristics and behavior of poorly water-soluble drugs, such as aqueous dispersibility and oral bioavailability. This investigation presents a novel nanostructured lipid carrier (NLC) based on a mixture of solid lipid glycerides, fatty acid esters of PEG 1500 (Gelucire® 44/14), and an oil mix composed of capric and caprylic triglycerides (Miglyol® 812). These NLCs were developed by a simple low-energy method based on melt emulsification to yield highly encapsulating and narrowly distributed nanoparticles (~100 nm, PdI = 0.1, and zeta potential = ~−10 mV). Rhodamine 123 was selected as a poorly water-soluble drug model and owing to its spectroscopic properties. The novel NLCs were characterized by dynamic light scattering (DLS), zeta potential, nanoparticle tracking analysis (NTA), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and colloidal stability. The drug release was determined through a dialysis bag and vertical Franzs’ cells to provide insights about the methods’ suitability, revealing similar performance regardless of their different fluid dynamics. Rhodamine 123 followed a characteristic biphasic release profile owing to the swelling of the hydrophilic polymer coating and diffusion process from the lipid core as revealed by the Korsmeyers–Peppas kinetic modeling. Moreover, to elucidate the formation and incorporation of Rhodamine 123 into the NLC core, several molecular dynamics simulations were conducted. The temperature was shown to be an important condition to improve the formation of the nanoparticles. In addition, the liquid lipid incorporation to the formulation forms nanoparticles with imperfect centers, in contrast to nanoparticles without it. Moreover, Miglyol® 812 improves hydrophobic molecule solubility. These results suggest the potential of novel NLC as a drug delivery system for poorly water-soluble drugs.

The Study on the Nanocutting by Rigid Body Tool at the Gas Environment Using Molecular Dynamics Simulations

2014 ◽  
Vol 494-495 ◽  
pp. 400-403
Author(s):  
Jen Ching Huang ◽  
Fu Jen Cheng
Keyword(s):  
Molecular Dynamics ◽  
Rigid Body ◽  
Equivalent Stress ◽  
Shear Plane ◽  
Nitrogen Gas ◽  
Machined Surface ◽  
Chip Surface ◽  
Single Crystal Copper ◽  
Gas Environment ◽  
Dynamics Simulations

This study successfully simulated the single crystal copper nanocutting with a rigid body tool at the nitrogen gas environment using molecular dynamics, and analyzed the workpiece stress distribution and dislocation during nanocutting. After simulations, a diamond rigid tool with a completely sharp produce a shear plane during cutting. The distribution of equivalent stress was greatest at the shear zone and that residual stress occurred on the machined surface. And the stress gets smaller as the distance from the chip surface is farther.

Zeta potential in porous rocks in contact with monovalent and divalent electrolyte aqueous solutions

Geophysics ◽  
2016 ◽  
Vol 81 (4) ◽  
pp. D303-D314 ◽  
Author(s):  
Luong Duy Thanh ◽  
Rudolf Sprik
Keyword(s):  
Zeta Potential ◽  
Streaming Potential ◽  
Shear Plane ◽  
Theoretical Models ◽  
Porous Rocks ◽  
Electrokinetic Phenomena ◽  
Reservoir Rocks ◽  
Partially Saturated ◽  
Different Types ◽  
Stern Potential

Electrokinetic phenomena are the result of a coupling between a fluid flow and an electric current flow in porous rocks. The zeta potential is an important parameter that influences the electrokinetic coupling. Most reservoir rocks are saturated or partially saturated by natural water containing various types of ions. Therefore, it is important to understand how the zeta potential and therefore the electric double layer (EDL) behave for different types of ions or electrolytes. Types of electrolytes influence the zeta potential most by affecting the surface charge — by changing the thickness of the EDL and the exact location of the shear plane. To study the dependence of the zeta potential on various electrolytes, we have carried out streaming potential measurements for consolidated rock samples saturated by monovalent and divalent electrolytes. From streaming potential coefficients, the zeta potential is obtained for different systems of electrolytes and rocks. The experimental results of silica-based rocks are then compared with theoretical models. For 1:1 or 1:2 electrolytes, a theoretical model for the zeta potential that has been available in literature is used. For 2:2 or 2:1 electrolytes, we have developed a new model to calculate the Stern potential and the zeta potential. The comparison found that the theoretical models can explain the main behavior of the zeta potential against types of electrolytes and types of silica-based rocks. The results show that the zeta potential for monovalent electrolytes is higher than that for divalent electrolytes. The zeta potential of the silica-based samples is higher than that of the nonsilica-based samples when they are saturated by the same types of electrolyte.

scholarly journals Molecular Dynamics Simulation of Mechanical Deformation of Ultra-Thin Metal and Ceramic Films

1995 ◽  
Vol 389 ◽  
Author(s):  
J. Belak ◽  
J.N. Glosli ◽  
D.B. Boercker ◽  
I.F. Stowers
Keyword(s):  
Molecular Dynamics ◽  
Orthogonal Cutting ◽  
Amorphous State ◽  
Computer Experiment ◽  
Shear Plane ◽  
Simulation Method ◽  
Dynamics Simulation ◽  
Interesting Phenomenon ◽  
Entire Volume ◽  
Embedded Atom

ABSTRACTWe present an overview of the molecular dynamics computer simulation method as employed in the study of the mechanical properties of surfaces at the nanometer scale. The embedded atom method is used to model a clean metal surface and the bond-order model is used to model ceramic surfaces. The computer experiment consists of the indentation and scraping of a hard diamond-like tool into and across the surface. Results are presented for the (111) surface of copper and silver and for the (100) surface of silicon. We explicitly demonstrate in our point indentation simulations that nanoscale plasticity in metals takes place by nondislocation mechanisms, a result suggested by recent nanoindentation experiments. We also observe the surface to accommodate nearly the entire volume of the tip and the annealing out of plastic work as the tip is removed. In our orthogonal cutting simulation, we observe an interesting phenomenon: the system dynamically reorients the grain in front of the tool tip to minimize the work performed on the shear plane (i.e. the shear plane becomes an easy slip plane). Silicon transforms into an amorphous state which then flows plastically.

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