The Experts below are selected from a list of 246 Experts worldwide ranked by ideXlab platform
Subramanian K. R. S. Sankaranarayanan - One of the best experts on this subject based on the ideXlab platform.
-
machine learning applied to a variable charge atomistic model for cu hf binary alloy oxide heterostructures
Chemistry of Materials, 2019Co-Authors: Kiran Sasikumar, Badri Narayanan, Subramanian K. R. S. Sankaranarayanan, Henry ChanAbstract:Alloy oxide heterostructures are essential for a wide variety of energy applications, including anticorrosion coatings, bifunctional catalysis, energy storage, as well as emerging platforms for multilevel nonvolatile memory and neuromorphic devices. The key role played by oxide composition, density, and stoichiometry in governing electrochemical reactions, interface structure, and Ionic transport in alloy oxides remains largely unknown. This is primarily due to the lack of variable charge interatomic Potential models that can adequately describe the various atomic/Ionic interactions in alloy oxides within a unified framework. Here, we introduce a charge transfer Ionic Potential (CTIP) model for Cu/Hf/O alloy system and demonstrate its ability to accurately capture the complex Potential energy surface owing to dynamically varying interactions, including metallic (Cu/Hf), Ionic (Cu/Hf/Ox), mixed environment (interfaces). We leverage supervised machine learning methods powered by genetic algorithms coupled w...
-
Evolutionary Optimization of a Charge Transfer Ionic Potential Model for Ta/Ta-Oxide Heterointerfaces
Chemistry of Materials, 2017Co-Authors: Kiran Sasikumar, Badri Narayanan, Mathew J. Cherukara, Alper Kinaci, Stephen K. Gray, Maria K. Y. Chan, Subramanian K. R. S. SankaranarayananAbstract:Heterostructures of tantalum and its oxide are of tremendous technological interest for myriad technological applications, including electronics, thermal management, catalysis, and biochemistry. In particular, local oxygen stoichiometry variation in TaOx memristors comprising thermodynamically stable metallic (Ta) and insulating oxide (Ta2O5) have been shown to result in fast switching on the subnanosecond time scale over a billion cycles. This rapid switching opens up the Potential for advanced functional platforms such as stateful logic operations and neuromorphic computation. Despite its broad importance, an atomistic scale understanding of oxygen stoichiometry variation across Ta/TaOx heterointerfaces, such as during early stages of oxidation and oxide growth, is not well understood. This is mainly due to the lack of a unified interatomic Potential model for tantalum oxides that can accurately describe metallic (Ta) and Ionic (TaOx) as well as mixed (Ta/TaOx interfaces) bonding environments simultaneo...
Bernard Auclair - One of the best experts on this subject based on the ideXlab platform.
-
Bi-Ionic Potential through a cation exchange membrane separating two electrolyte solutions at different concentrations
Electrochimica Acta, 2001Co-Authors: S. Tran, Lasâad Dammak, Christian Larchet, Bernard AuclairAbstract:Abstract We have studied the bi-Ionic Potential (BIP) through an ion-exchange membrane separating two electrolyte solutions having the same co-ion, different counter-ions and different concentrations. This study is carried out for a cation exchange membrane (CM1: a polystyrene and divinylbenzene sulfonated membrane), for three electrolyte pairs (ACl—BCl where A, B ∈ {K, Na, Li}) and for two stirring rates (ω 0 = 0 rpm and ω max = 900 rpm). Our experimental results show that the higher the concentration of the more mobile counter-ion (A) the higher the BIP, and conversely for B. The BIP variation versus the logarithm of the concentration of one solution is almost linear until 0.1 M for all the systems studied. The stirring rate, ω, has no influence on the BIP values if the concentration of A or B is very small (of the order of 0.001 M). However, if the concentrations of A and B are greater than 0.01 M, ω has a non-negligible effect which is attributed to the existence of diffusion boundary layers. The influences of the co-ion flux, of the solvent flux and of the counter-ion hydrated volumes have been examined.
-
Theoretical study of the bi-Ionic Potential and confrontation with experimental results
Journal of Membrane Science, 1999Co-Authors: Lasâad Dammak, Christian Larchet, Bernard AuclairAbstract:A theoretical study of the bi-Ionic Potential (BIP) has been carried out using the extended Nernst‐Planck equation in the case of a mixed control of the interdiffusion process by the ion-exchange membrane (IEM) and the diffusion boundary layers (DBLs), a non-zero co-ion flux, a non-zero water flux, a variable selectivity coefficient and an affinity coefficient different from unity. The numerical integration of the two coupled differential transport equations allowed, for a given common concentration C0, the computation of the BIP from the values of 12 parameters required. Three of these 12 parameters are taken from the literature, the others are determined from independent experiments except the DBL thickness and the co-ion diffusion coefficient in the membrane. We have developed a procedure to deduce these two parameters from the experimental curves of the BIP vs. C0. For the NaCl/CM2/LiCl bi-Ionic system, the DBL thickness changes from 59 mm at high stirring rate to 196 m mi n the absence of stirring. The chloride diffusion coefficient in the CM2 membrane has been estimated to be equal to 2.110 ˇ7 cm 2 s ˇ1 . Using these values, we have studied theoretically the influence of each of the three parameters: affinity coefficient, selectivity coefficient and water flow. We have shown that the affinity coefficient has the most important contribution but the selectivity coefficient and the water flow influence only the BIP at high common concentrations. # 1999 Elsevier Science B.V. All rights reserved.
-
Water transport in bi-Ionic systems: theoretical treatment and effect on the bi-Ionic Potential
New Journal of Chemistry, 1998Co-Authors: Lasâad Dammak, Christian Larchet, Roger Lteif, Bernard AuclairAbstract:In a previous paper, we have proposed a new experimental method for measuring the water flow and the convection velocity, vM, in the case of a bi-Ionic system. In the present paper, we propose analytical and numerical treatments to evaluate the contribution (ΔBIP) of the measured convection velocities to the bi-Ionic Potential values. These theoretical treatments are based on the pseudo-thermodynamic equation and show a linear relationship between ΔBIP and vM. The ΔBIP values were less than 0.8 mV for concentrations less than 2.0 M. This represents about 4–6% of the experimental bi-Ionic Potential values obtained with a high selective ion exchange membrane (CM2). The convection velocity vM and its contribution to the BIP values are theoretically more important for less selective membranes. Transport d'eau dans les systemes bi-ioniques: traitement the′orique et effet sur le potentiel bi-ionique. Dans un article pre′ce′dent, nous avons propose′ une me′thode expe′rimentale pour mesurer le flux d'eau et la vitesse de convection vM dans le cas d'un systeme bi-ionique. Dans le pre′sent article, nous proposons des traitements analytiques et nume′riques pour e′valuer la contribution, ΔBIP, des vitesses de convection mesure′es sur les valeurs du potentiel bi-ionique. Ces traitements the′oriques sont base′s sur l'e′quation pseudo-thermodynamique et montrent une relation line′aire entre ΔBIP et vM. Les valeurs de ΔBIP sont en dessous de 0.8 mV pour des concentrations infe′rieures a 2.0 M. Ceci repre′sente environ 4–6% des valeurs expe′rimentales du potentiel bi-ionique obtenues avec une membrane e′changeuse d'ions tres se′lective (CM2). La vitesse de convection vM et ses contributions aux valeurs du BIP sont the′oriquement plus importantes pour des membranes moins se′lectives.
-
A MATHEMATICAL MODEL FOR THE BI-Ionic Potential
European Polymer Journal, 1997Co-Authors: Victor Nikonenko, K. A. Lebedev, V.i. Zabolotsky, Lasâad Dammak, Christian Larchet, Bernard AuclairAbstract:The influence of the salt concentration (c0), the diffusion boundary layers, and the ratio of the counter-ions diffusion coefficients on the bi-Ionic Potential (BIP) values have been analysed theoretically on the basis of a simple mathematical model based on the Nernst-Planck equations and on the TMS model. For c0 < 0.1 M, the numerical solution of the boundary-value problem for an ideal permselective membrane gives a theoretical BIP vs c0 curves similar to those obtained experimentally by Dammak et al. The diffusion coefficient ratio in the membrane plays an important role in determining the BIP values. © 1997 Elsevier Science Ltd
-
The influence of the salt concentration and the diffusion boundary layers on the bi-Ionic Potential
Journal of Membrane Science, 1996Co-Authors: Lasâad Dammak, Christian Larchet, Bernard Auclair, José A. Manzanares, Salvador MaféAbstract:Measurements of bi-Ionic Potential (BIP) across three cation-exchange membranes (CEMs) have been carried out for KCl/CEM/NaCl, KCl/CEM/LiCl, and NaCl/CEM/LiCl systems, where CEM is a polystyrene and divinylbenzene sulfonated membrane (CM2, from Tokuyama Soda), a perfluorosulfonic acid membrane (Nafion® 117, from Du Pont De Nemours) and an heterogenous membrane prepared by inclusion of cation-exchange resin in PVC (CRP, from Rhone Poulenc). The influence of the salt concentration and the diffusion boundary layers (DBLs) on the BIP values has been analysed both theoretically and experimentally. The theoretical model is based on the Nernst-Planck equations, and gives a good description for salt concentrations higher than 5×10−4 M. For the CM2 membrane, the DBL thickness changes from 20–23 μm in absence of stirring to 3–4 μm for high stirring rates. Also, the ion diffusion coefficients in this membrane have been estimated to be of the order of 10−6 cm2/s. It has been observed that the counter-ion diffusion coefficients ratio (DA/DB) in the membrane increases significantly when the membrane water content decreases, which suggests the possibility of achieving highly selective ion transport with low water content membranes.
John Reginald Bunt - One of the best experts on this subject based on the ideXlab platform.
-
reducing atmosphere ash fusion temperatures of a mixture of coal associated minerals the effect of inorganic additives and ashing temperature
Fuel Processing Technology, 2014Co-Authors: Christien A. Strydom, Paul J Beukes, Harold H Schobert, John Reginald BuntAbstract:Abstract The influence of the ashing temperature and inorganic additives on the reducing-atmosphere ash fusion temperatures of a mixture of coal-associated minerals was investigated. Different inorganic compounds were added to the mixture to represent trace minerals in coal or coal ash. The samples were ashed at either 500 °C or 815 °C in air as preparation for ash fusion temperature experiments. The ashing temperature influenced the ash fusion temperatures of the mineral mixture doped with 4% NaCl, PbCO3 and CrO3 at one or both of the ashing temperatures. The addition of GeS and SrCO3 resulted in a decreasing trend in the AFTs of the mineral mixture, and that of GeO2 resulted in an increasing trend. The lowering of the AFTs from the addition of PbCO3 was comparable to the effect from NaCl. The concept of Ionic Potential provides an insight into why different additives produce different effects. In general, additives containing elements of low Ionic Potential (
Lasâad Dammak - One of the best experts on this subject based on the ideXlab platform.
-
Bi-Ionic Potential through a cation exchange membrane separating two electrolyte solutions at different concentrations
Electrochimica Acta, 2001Co-Authors: S. Tran, Lasâad Dammak, Christian Larchet, Bernard AuclairAbstract:Abstract We have studied the bi-Ionic Potential (BIP) through an ion-exchange membrane separating two electrolyte solutions having the same co-ion, different counter-ions and different concentrations. This study is carried out for a cation exchange membrane (CM1: a polystyrene and divinylbenzene sulfonated membrane), for three electrolyte pairs (ACl—BCl where A, B ∈ {K, Na, Li}) and for two stirring rates (ω 0 = 0 rpm and ω max = 900 rpm). Our experimental results show that the higher the concentration of the more mobile counter-ion (A) the higher the BIP, and conversely for B. The BIP variation versus the logarithm of the concentration of one solution is almost linear until 0.1 M for all the systems studied. The stirring rate, ω, has no influence on the BIP values if the concentration of A or B is very small (of the order of 0.001 M). However, if the concentrations of A and B are greater than 0.01 M, ω has a non-negligible effect which is attributed to the existence of diffusion boundary layers. The influences of the co-ion flux, of the solvent flux and of the counter-ion hydrated volumes have been examined.
-
Theoretical study of the bi-Ionic Potential and confrontation with experimental results
Journal of Membrane Science, 1999Co-Authors: Lasâad Dammak, Christian Larchet, Bernard AuclairAbstract:A theoretical study of the bi-Ionic Potential (BIP) has been carried out using the extended Nernst‐Planck equation in the case of a mixed control of the interdiffusion process by the ion-exchange membrane (IEM) and the diffusion boundary layers (DBLs), a non-zero co-ion flux, a non-zero water flux, a variable selectivity coefficient and an affinity coefficient different from unity. The numerical integration of the two coupled differential transport equations allowed, for a given common concentration C0, the computation of the BIP from the values of 12 parameters required. Three of these 12 parameters are taken from the literature, the others are determined from independent experiments except the DBL thickness and the co-ion diffusion coefficient in the membrane. We have developed a procedure to deduce these two parameters from the experimental curves of the BIP vs. C0. For the NaCl/CM2/LiCl bi-Ionic system, the DBL thickness changes from 59 mm at high stirring rate to 196 m mi n the absence of stirring. The chloride diffusion coefficient in the CM2 membrane has been estimated to be equal to 2.110 ˇ7 cm 2 s ˇ1 . Using these values, we have studied theoretically the influence of each of the three parameters: affinity coefficient, selectivity coefficient and water flow. We have shown that the affinity coefficient has the most important contribution but the selectivity coefficient and the water flow influence only the BIP at high common concentrations. # 1999 Elsevier Science B.V. All rights reserved.
-
Water transport in bi-Ionic systems: theoretical treatment and effect on the bi-Ionic Potential
New Journal of Chemistry, 1998Co-Authors: Lasâad Dammak, Christian Larchet, Roger Lteif, Bernard AuclairAbstract:In a previous paper, we have proposed a new experimental method for measuring the water flow and the convection velocity, vM, in the case of a bi-Ionic system. In the present paper, we propose analytical and numerical treatments to evaluate the contribution (ΔBIP) of the measured convection velocities to the bi-Ionic Potential values. These theoretical treatments are based on the pseudo-thermodynamic equation and show a linear relationship between ΔBIP and vM. The ΔBIP values were less than 0.8 mV for concentrations less than 2.0 M. This represents about 4–6% of the experimental bi-Ionic Potential values obtained with a high selective ion exchange membrane (CM2). The convection velocity vM and its contribution to the BIP values are theoretically more important for less selective membranes. Transport d'eau dans les systemes bi-ioniques: traitement the′orique et effet sur le potentiel bi-ionique. Dans un article pre′ce′dent, nous avons propose′ une me′thode expe′rimentale pour mesurer le flux d'eau et la vitesse de convection vM dans le cas d'un systeme bi-ionique. Dans le pre′sent article, nous proposons des traitements analytiques et nume′riques pour e′valuer la contribution, ΔBIP, des vitesses de convection mesure′es sur les valeurs du potentiel bi-ionique. Ces traitements the′oriques sont base′s sur l'e′quation pseudo-thermodynamique et montrent une relation line′aire entre ΔBIP et vM. Les valeurs de ΔBIP sont en dessous de 0.8 mV pour des concentrations infe′rieures a 2.0 M. Ceci repre′sente environ 4–6% des valeurs expe′rimentales du potentiel bi-ionique obtenues avec une membrane e′changeuse d'ions tres se′lective (CM2). La vitesse de convection vM et ses contributions aux valeurs du BIP sont the′oriquement plus importantes pour des membranes moins se′lectives.
-
A MATHEMATICAL MODEL FOR THE BI-Ionic Potential
European Polymer Journal, 1997Co-Authors: Victor Nikonenko, K. A. Lebedev, V.i. Zabolotsky, Lasâad Dammak, Christian Larchet, Bernard AuclairAbstract:The influence of the salt concentration (c0), the diffusion boundary layers, and the ratio of the counter-ions diffusion coefficients on the bi-Ionic Potential (BIP) values have been analysed theoretically on the basis of a simple mathematical model based on the Nernst-Planck equations and on the TMS model. For c0 < 0.1 M, the numerical solution of the boundary-value problem for an ideal permselective membrane gives a theoretical BIP vs c0 curves similar to those obtained experimentally by Dammak et al. The diffusion coefficient ratio in the membrane plays an important role in determining the BIP values. © 1997 Elsevier Science Ltd
-
The influence of the salt concentration and the diffusion boundary layers on the bi-Ionic Potential
Journal of Membrane Science, 1996Co-Authors: Lasâad Dammak, Christian Larchet, Bernard Auclair, José A. Manzanares, Salvador MaféAbstract:Measurements of bi-Ionic Potential (BIP) across three cation-exchange membranes (CEMs) have been carried out for KCl/CEM/NaCl, KCl/CEM/LiCl, and NaCl/CEM/LiCl systems, where CEM is a polystyrene and divinylbenzene sulfonated membrane (CM2, from Tokuyama Soda), a perfluorosulfonic acid membrane (Nafion® 117, from Du Pont De Nemours) and an heterogenous membrane prepared by inclusion of cation-exchange resin in PVC (CRP, from Rhone Poulenc). The influence of the salt concentration and the diffusion boundary layers (DBLs) on the BIP values has been analysed both theoretically and experimentally. The theoretical model is based on the Nernst-Planck equations, and gives a good description for salt concentrations higher than 5×10−4 M. For the CM2 membrane, the DBL thickness changes from 20–23 μm in absence of stirring to 3–4 μm for high stirring rates. Also, the ion diffusion coefficients in this membrane have been estimated to be of the order of 10−6 cm2/s. It has been observed that the counter-ion diffusion coefficients ratio (DA/DB) in the membrane increases significantly when the membrane water content decreases, which suggests the possibility of achieving highly selective ion transport with low water content membranes.
Mohd Arsalan - One of the best experts on this subject based on the ideXlab platform.
-
Synthesis, characterization and electrochemical observation of PVC based ZMP composite porous membrane and its physicochemical studies by applying some strong electrolytes through TMS equation
Journal of Solid State Electrochemistry, 2015Co-Authors: Mohd ArsalanAbstract:PVC based zinc molybdophosphate (ZMP) has been synthesized via sol gel method of material synthesis, which is used to design a mechanically stable organic-inorganic composite membrane. The composite material plus membrane has been characterized by using various sophisticated techniques like x-ray diffraction, fourier transforms infrared spectroscopy, scanning electron microscopy, thermo gravimetric/differential thermal analysis and simultaneously potentiometer analysis also. The characterizations confirmed that there is a strong interaction found between PVC and ZMP particles and the resulting composite has indicated higher thermal stability than the pure material. It also demonstrated the material nature, functional groups, surface structure, thermal stability, porosity, and ion transportation etc. Teorell, Meyer, and Sievers (TMS) theoretical approach is used to explain the various electrochemical applications of membrane like charge density, transport number, mobility ratio, charge effectiveness etc. Some strong electrolytes like KCl, NaCl and LiCl are used to explain the membrane behavior which has been confirmed by observing the Ionic Potential and charge density of membrane.
