The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Kandadai Srinivasan - One of the best experts on this subject based on the ideXlab platform.
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theoretical insight of Physical Adsorption for a single component adsorbent adsorbate system ii the henry region
Langmuir, 2009Co-Authors: Anutosh Chakraborty, Bidyut Baran Saha, Shigeru Koyama, Kandadai SrinivasanAbstract:The Henry coefficients of a single component adsorbent + adsorbate system are calculated from experimentally measured Adsorption isotherm data, from which the heat of Adsorption at zero coverage is evaluated. The first part of the papers relates to the development of thermodynamic property surfaces for a single-component adsorbent+adsorbate system (Chakraborty, A.; Saha, B. B.; Ng, K. C.; Koyama, S.; Srinivasan, K. Langmuir 2009, 25, 2204). A thermodynamic framework is presented to capture the relationship between the specific surface area (Ai) and the energy factor, and the surface structural and the surface energy heterogeneity distribution factors are analyzed. Using the outlined approach, the maximum possible amount of adsorbate uptake has been evaluated and compared with experimental data. It is found that the adsorbents with higher specific surface areas tend to possess lower heat of Adsorption (DeltaH degrees) at the Henry regime. In this paper, we have established the definitive relation between Ai and DeltaH degrees for (i) carbonaceous materials, metal organic frameworks (MOFs), carbon nanotubes, zeolites+hydrogen, and (ii) activated carbons+methane systems. The proposed theoretical framework of Ai and DeltaH degrees provides valuable guides for researchers in developing advanced porous adsorbents for methane and hydrogen uptake.
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theoretical insight of Physical Adsorption for a single component adsorbent adsorbate system i thermodynamic property surfaces
Langmuir, 2009Co-Authors: Anutosh Chakraborty, Bidyut Baran Saha, Shigeru Koyama, Kandadai SrinivasanAbstract:Thermodynamic property surfaces for a single-component adsorbent + adsorbate system are derived and developed from the viewpoint of classical thermodynamics, thermodynamic requirements of chemical equilibrium, Gibbs law, and Maxwell relations. They enable us to compute the entropy and enthalpy of the adsorbed phase, the isosteric heat of Adsorption, specific heat capacity, and the adsorbed phase volume thoroughly. These equations are very simple and easy to handle for calculating the energetic performances of any Adsorption system. We have shown here that the derived thermodynamic formulations fill up the information gap with respect to the state of adsorbed phase to dispel the confusion as to what is the actual state of the adsorbed phase. We have also discussed and established the temperature-entropy diagrams of (i) CaCl2-in-silica gel + water system for cooling applications, and (ii) activated carbon (Maxsorb III) + methane system for gas storage.
Alexandre Tkatchenko - One of the best experts on this subject based on the ideXlab platform.
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Physical Adsorption at the nanoscale towards controllable scaling of the substrate adsorbate van der waals interaction
Physical Review B, 2017Co-Authors: Alberto Ambrosetti, Pier Luigi Silvestrelli, Alexandre TkatchenkoAbstract:The Lifshitz-Zaremba-Kohn (LZK) theory is commonly considered as the correct large-distance limit for the van der Waals (vdW) interaction of adsorbates (atoms, molecules, or nanoparticles) with solid substrates. In the standard approximate form, implicitly based on "local" dielectric functions, the LZK approach predicts universal power laws for vdW interactions depending only on the dimensionality of the interacting objects. However, recent experimental findings are challenging the universality of this theoretical approach at finite distances of relevance for nanoscale assembly. Here, we present a combined analytical and numerical many-body study demonstrating that Physical Adsorption can be significantly enhanced at the nanoscale. Regardless of the band gap or the nature of the adsorbate specie, we find deviations from conventional LZK power laws that extend to separation distances of up to 10--20 nanometers. Comparison with recent experimental observation of ultra long-ranged vdW interactions in the delamination of graphene from a silicon substrate reveals qualitative agreement with the present theory. The sensitivity of vdW interactions to the substrate response and to the adsorbate characteristic excitation frequency also suggests that Adsorption strength can be effectively tuned in experiments, paving the way to an improved control of Physical Adsorption at the nanoscale.
Andrew M Rappe - One of the best experts on this subject based on the ideXlab platform.
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Physical Adsorption theory of van der waals interactions between particles and clean surfaces
Physical Review Letters, 2014Co-Authors: Andrew M RappeAbstract:: van der Waals (vdW) interactions between particles and surfaces are critical for the study of Physical Adsorption. In this work, we develop a method to calculate the leading- and higher-order coefficients, describing the dependence of vdW interaction on height above the surface. We find that the proposed method can produce the vdW coefficients for atoms on surfaces of metals and semiconductors, with a mean absolute relative deviation of about 5%. As an important application, we study the Adsorption energies for rare-gas atoms on noble-metal surfaces by combining the present method, which accounts for the long-range part, with semilocal density functional theory (DFT), which accounts for the short-range part. This combined DFT+vdW approach yields Adsorption energies in excellent agreement (5%) with experiments. This suggests that the present method may serve as a useful dispersion correction to density functional approximations.
Anutosh Chakraborty - One of the best experts on this subject based on the ideXlab platform.
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theoretical insight of Physical Adsorption for a single component adsorbent adsorbate system ii the henry region
Langmuir, 2009Co-Authors: Anutosh Chakraborty, Bidyut Baran Saha, Shigeru Koyama, Kandadai SrinivasanAbstract:The Henry coefficients of a single component adsorbent + adsorbate system are calculated from experimentally measured Adsorption isotherm data, from which the heat of Adsorption at zero coverage is evaluated. The first part of the papers relates to the development of thermodynamic property surfaces for a single-component adsorbent+adsorbate system (Chakraborty, A.; Saha, B. B.; Ng, K. C.; Koyama, S.; Srinivasan, K. Langmuir 2009, 25, 2204). A thermodynamic framework is presented to capture the relationship between the specific surface area (Ai) and the energy factor, and the surface structural and the surface energy heterogeneity distribution factors are analyzed. Using the outlined approach, the maximum possible amount of adsorbate uptake has been evaluated and compared with experimental data. It is found that the adsorbents with higher specific surface areas tend to possess lower heat of Adsorption (DeltaH degrees) at the Henry regime. In this paper, we have established the definitive relation between Ai and DeltaH degrees for (i) carbonaceous materials, metal organic frameworks (MOFs), carbon nanotubes, zeolites+hydrogen, and (ii) activated carbons+methane systems. The proposed theoretical framework of Ai and DeltaH degrees provides valuable guides for researchers in developing advanced porous adsorbents for methane and hydrogen uptake.
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theoretical insight of Physical Adsorption for a single component adsorbent adsorbate system i thermodynamic property surfaces
Langmuir, 2009Co-Authors: Anutosh Chakraborty, Bidyut Baran Saha, Shigeru Koyama, Kandadai SrinivasanAbstract:Thermodynamic property surfaces for a single-component adsorbent + adsorbate system are derived and developed from the viewpoint of classical thermodynamics, thermodynamic requirements of chemical equilibrium, Gibbs law, and Maxwell relations. They enable us to compute the entropy and enthalpy of the adsorbed phase, the isosteric heat of Adsorption, specific heat capacity, and the adsorbed phase volume thoroughly. These equations are very simple and easy to handle for calculating the energetic performances of any Adsorption system. We have shown here that the derived thermodynamic formulations fill up the information gap with respect to the state of adsorbed phase to dispel the confusion as to what is the actual state of the adsorbed phase. We have also discussed and established the temperature-entropy diagrams of (i) CaCl2-in-silica gel + water system for cooling applications, and (ii) activated carbon (Maxsorb III) + methane system for gas storage.
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theoretical insight of Physical Adsorption for a single component adsorbent adsorbate system
ASME International Mechanical Engineering Congress and Exposition Proceedings (IMECE), 2007Co-Authors: Anutosh Chakraborty, Bidyut Baran Saha, Shigeru Koyama, Ibrahim I ElsharkawyAbstract:The thermodynamic property surfaces for a single-component adsorbent + adsorbate system have been derived and developed from the view point of classical thermodynamics. These thermodynamic frameworks enable us to compute the specific heat capacity, partial enthalpy and entropy for the analyses of Adsorption processes thoroughly. A theoretical framework for the estimation of the isosteric heat of Adsorption between an adsorbate (vapor) and an adsorbent (solid) is also derived for the thermodynamic requirements of chemical equilibrium, Maxwell relations and the entropy of the adsorbed phase. Conventionally, the specific heat capacity of the adsorbate is assumed to correspond to its liquid phase specific heat capacity and more recently to that of its gas phase. We have shown here that the derived specific heat capacity fills up the information gap with respect to the state of adsorbed phase to dispel the confusion as to what is the actual state of the adsorbed phase.© 2007 ASME
Matthias Thommes - One of the best experts on this subject based on the ideXlab platform.
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insights into the pore structure of kit 6 and sba 15 ordered mesoporous silica recent advances by combining Physical Adsorption with mercury porosimetry
New Journal of Chemistry, 2016Co-Authors: Remy Guilletnicolas, R Ahmad, Katie A Cychosz, Freddy Kleitz, Matthias ThommesAbstract:We have performed a systematic study of N2 Adsorption at 77 K and Hg porosimetry experiments at 298 K on highly ordered KIT-6 and SBA-15 silicas exhibiting noticeably different pore structures with pore diameters in the 7–11 nm range. Accurate pore structure analysis was performed by applying appropriate NLDFT methods to the N2 physisorption data. Mercury intrusion/extrusion experiments on KIT-6 silicas (up to 415 000 kPa) showed no collapse of the pore structure quite remarkably. To the best of our knowledge, this is the first successful example of Hg porosimetry on KIT-6 materials. Hence, it was possible to utilize KIT-6 mesoporous molecular sieves for quantitatively testing the validity of the Washburn equation applied to mercury intrusion for pore size analysis. KIT-6 silicas also allowed investigating the analogies between condensation/evaporation mechanisms of wetting (N2 at 77 K) and non-wetting (Hg at 298 K) fluids as a function of the pore size confirming the thermodynamic consistency between Hg intrusion/extrusion and capillary evaporation/condensation. Contrary to KIT-6 silicas, Hg porosimetry experiments on SBA-15 materials of identical pore diameters show an inconsistent behavior in a sense that both reversible Hg intrusion/extrusion data and partial collapse of the pore structure were observed. Our work clearly demonstrates that combining advanced Physical Adsorption and Hg porosimetry studies provides a more thorough understanding of textural features and shed some light on the fundamental questions concerning the effect of confinement on the phase behavior of wetting and non-wetting fluids.
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Physical Adsorption characterization of nanoporous materials: progress and challenges
Adsorption, 2014Co-Authors: Matthias Thommes, Katie A CychoszAbstract:Within the last two decades major progress has been achieved in understanding the Adsorption and phase behavior of fluids in ordered nanoporous materials and in the development of advanced approaches based on statistical mechanics such as molecular simulation and density functional theory (DFT) of inhomogeneous fluids. This progress, coupled with the availability of high resolution experimental procedures for the Adsorption of various subcritical fluids, has led to advances in the structural characterization by Physical Adsorption. It was demonstrated that the application of DFT based methods on high resolution experimental Adsorption isotherms provides a much more accurate and comprehensive pore size analysis compared to classical, macroscopic methods. This article discusses important aspects of major underlying mechanisms associated with Adsorption, pore condensation and hysteresis behavior in nanoporous solids. We discuss selected examples of state-of-the-art pore size characterization and also reflect briefly on the existing challenges in Physical Adsorption characterization.
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advanced Physical Adsorption characterization of nanoporous carbons
Novel Carbon Adsorbents, 2012Co-Authors: Matthias Thommes, Katie A Cychosz, Alexander V NeimarkAbstract:Within the last two decades, major progress has been achieved in understanding the Adsorption and phase behavior of fluids in ordered nanoporous materials and in the development of advanced theoretical approaches based on statistical mechanics such as density functional theory (DFT) of inhomogeneous fluids and molecular simulation, leading to advances in structural characterization by Physical Adsorption. It was demonstrated that the application of DFT-based methods provides a much more accurate and comprehensive pore-size analysis compared to macroscopic, thermodynamic methods such as the Dubinin–Radushkevich, Horvath Kawazoe, and Kelvin equation approaches. In particular, the recently developed quenched solid density functional theory (QSDFT) method quantitatively accounts for surface heterogeneity and gives a reliable pore-size assessment for disordered micro- and mesoporous carbons. This chapter provides an overview of the major underlying mechanisms associated with Adsorption, pore condensation, and hysteresis behavior in micro- and mesoporous carbons and discusses selected examples of state-of-the-art surface and pore-size characterization.
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Physical Adsorption characterization of nanoporous materials
Chemie-Ingenieur-Technik, 2010Co-Authors: Matthias ThommesAbstract:During recent years, major progress has been made in the understanding of the Adsorption, pore condensation and hysteresis behavior of fluids in novel ordered nanoporous materials with well defined pore structure. This has led to major advances in the structural characterization by Physical Adsorption, also because of the development and availability of advanced theoretical procedures based on statistical mechanics (e.g., density functional theory, molecular simulation) which allows to describe Adsorption and phase behavior of fluids in pores on a molecular level. Very recent improvements allow even to take into account surface geometrical in-homogeneity of the pore walls However, there are still many open questions concerning the structural characterization of more complex porous systems. Important aspects of the major underlying mechanisms associated with the Adsorption, pore condensation and hysteresis behavior of fluids in micro-mesoporous materials are reviewed and their significance for advanced Physical Adsorption characterization is discussed.
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chapter 15 textural characterization of zeolites and ordered mesoporous materials by Physical Adsorption
Studies in Surface Science and Catalysis, 2007Co-Authors: Matthias ThommesAbstract:This chapter discusses the important aspects of applying gas Adsorption for the textural characterization of zeolites and ordered mesoporous materials. The chapter discusses the experimental requirements and procedures necessary to obtain accurate Adsorption data with high resolution. It is necessary to have a detailed understanding of the underlying Adsorption mechanisms in order to correctly analyze gas Adsorption isotherms for surface and pore size analysis. It discusses some important developments concerning state-of-the-art pore size- and surface area analysis of micro/mesoporous molecular sieves. Gas Adsorption is a widely used method for the characterization of micro-mesoporous materials with regard to the determination of surface area, pore size, pore size distribution, and porosity. The concept of surface area is of great practical value, although no single experimental technique can be expected to provide an evaluation of the absolute surface area.
