The Experts below are selected from a list of 79092 Experts worldwide ranked by ideXlab platform

J.m. Drake - One of the best experts on this subject based on the ideXlab platform.

  • porous vycor glass the microstructure as probed by electron microscopy direct energy transfer small angle scattering and Molecular Adsorption
    Journal of Chemical Physics, 1991
    Co-Authors: Pierre Levitz, Gerd Ehret, S K Sinha, J.m. Drake
    Abstract:

    We provide a comprehensive analysis of the microstructure of the porous glass, vycor. Using transmission electron microscopy, small‐angle x‐ray scattering, Molecular Adsorption, and the dynamic process of direct energy transfer, a consistent picture of the mass, pore, and interfacial features of this material is presented. From a transmission‐electron‐microscopy image of an ultrathin section of vycor the material appears to have a homogeneous distribution of mass with no hierarchical organization. The pore interface exhibits a roughness which is probed by both small‐angle x‐ray scattering and Molecular Adsorption. The roughness has an upper cutoff of <20 A which is not resolved in the transmission‐electron‐microscopy image and is shown to be unimportant to the dynamics of the direct energy transfer process. The dimensionality probed by direct energy transfer is shown to be related to interfacial geometrical crossover from two dimensional to three dimensional, which is characterized by a persistent length of the interface of 45 A.

  • Porous vycor glass: The microstructure as probed by electron microscopy, direct energy transfer, small-angle scattering, and Molecular Adsorption
    The Journal of Chemical Physics, 1991
    Co-Authors: Pierre Levitz, Gerd Ehret, Sumi Sinha, J.m. Drake
    Abstract:

    We provide a comprehensive analysis of the microstructure of the porous glass, vycor. Using transmission electron microscopy, small‐angle x‐ray scattering, Molecular Adsorption, and the dynamic process of direct energy transfer, a consistent picture of the mass, pore, and interfacial features of this material is presented. From a transmission‐electron‐microscopy image of an ultrathin section of vycor the material appears to have a homogeneous distribution of mass with no hierarchical organization. The pore interface exhibits a roughness which is probed by both small‐angle x‐ray scattering and Molecular Adsorption. The roughness has an upper cutoff of

  • Molecular Adsorption on Porous Silica Gels from Binary Solutions
    Israel Journal of Chemistry, 1991
    Co-Authors: J.m. Drake, Pierre Levitz, Joseph Klafter
    Abstract:

    In this paper we present a detailed experimental study of Molecular Adsorption on interfaces of silica gels from binary solutions of alcohol/toluene. The Adsorption measurements are corroborated with infrared spectra of the surface hydroxyl groups and with NMR results. The Adsorption isotherms are analyzed within the framework of the Everett approach and possible scaling relations between alcohol monolayer capacities and adsorbate cross sections are discussed. We conclude that reliable morphological information on the interfaces cannot be obtained from these Adsorption experiments.

Pierre Levitz - One of the best experts on this subject based on the ideXlab platform.

  • porous vycor glass the microstructure as probed by electron microscopy direct energy transfer small angle scattering and Molecular Adsorption
    Journal of Chemical Physics, 1991
    Co-Authors: Pierre Levitz, Gerd Ehret, S K Sinha, J.m. Drake
    Abstract:

    We provide a comprehensive analysis of the microstructure of the porous glass, vycor. Using transmission electron microscopy, small‐angle x‐ray scattering, Molecular Adsorption, and the dynamic process of direct energy transfer, a consistent picture of the mass, pore, and interfacial features of this material is presented. From a transmission‐electron‐microscopy image of an ultrathin section of vycor the material appears to have a homogeneous distribution of mass with no hierarchical organization. The pore interface exhibits a roughness which is probed by both small‐angle x‐ray scattering and Molecular Adsorption. The roughness has an upper cutoff of <20 A which is not resolved in the transmission‐electron‐microscopy image and is shown to be unimportant to the dynamics of the direct energy transfer process. The dimensionality probed by direct energy transfer is shown to be related to interfacial geometrical crossover from two dimensional to three dimensional, which is characterized by a persistent length of the interface of 45 A.

  • Porous vycor glass: The microstructure as probed by electron microscopy, direct energy transfer, small-angle scattering, and Molecular Adsorption
    The Journal of Chemical Physics, 1991
    Co-Authors: Pierre Levitz, Gerd Ehret, Sumi Sinha, J.m. Drake
    Abstract:

    We provide a comprehensive analysis of the microstructure of the porous glass, vycor. Using transmission electron microscopy, small‐angle x‐ray scattering, Molecular Adsorption, and the dynamic process of direct energy transfer, a consistent picture of the mass, pore, and interfacial features of this material is presented. From a transmission‐electron‐microscopy image of an ultrathin section of vycor the material appears to have a homogeneous distribution of mass with no hierarchical organization. The pore interface exhibits a roughness which is probed by both small‐angle x‐ray scattering and Molecular Adsorption. The roughness has an upper cutoff of

  • Molecular Adsorption on Porous Silica Gels from Binary Solutions
    Israel Journal of Chemistry, 1991
    Co-Authors: J.m. Drake, Pierre Levitz, Joseph Klafter
    Abstract:

    In this paper we present a detailed experimental study of Molecular Adsorption on interfaces of silica gels from binary solutions of alcohol/toluene. The Adsorption measurements are corroborated with infrared spectra of the surface hydroxyl groups and with NMR results. The Adsorption isotherms are analyzed within the framework of the Everett approach and possible scaling relations between alcohol monolayer capacities and adsorbate cross sections are discussed. We conclude that reliable morphological information on the interfaces cannot be obtained from these Adsorption experiments.

Gerd Ehret - One of the best experts on this subject based on the ideXlab platform.

  • porous vycor glass the microstructure as probed by electron microscopy direct energy transfer small angle scattering and Molecular Adsorption
    Journal of Chemical Physics, 1991
    Co-Authors: Pierre Levitz, Gerd Ehret, S K Sinha, J.m. Drake
    Abstract:

    We provide a comprehensive analysis of the microstructure of the porous glass, vycor. Using transmission electron microscopy, small‐angle x‐ray scattering, Molecular Adsorption, and the dynamic process of direct energy transfer, a consistent picture of the mass, pore, and interfacial features of this material is presented. From a transmission‐electron‐microscopy image of an ultrathin section of vycor the material appears to have a homogeneous distribution of mass with no hierarchical organization. The pore interface exhibits a roughness which is probed by both small‐angle x‐ray scattering and Molecular Adsorption. The roughness has an upper cutoff of <20 A which is not resolved in the transmission‐electron‐microscopy image and is shown to be unimportant to the dynamics of the direct energy transfer process. The dimensionality probed by direct energy transfer is shown to be related to interfacial geometrical crossover from two dimensional to three dimensional, which is characterized by a persistent length of the interface of 45 A.

  • Porous vycor glass: The microstructure as probed by electron microscopy, direct energy transfer, small-angle scattering, and Molecular Adsorption
    The Journal of Chemical Physics, 1991
    Co-Authors: Pierre Levitz, Gerd Ehret, Sumi Sinha, J.m. Drake
    Abstract:

    We provide a comprehensive analysis of the microstructure of the porous glass, vycor. Using transmission electron microscopy, small‐angle x‐ray scattering, Molecular Adsorption, and the dynamic process of direct energy transfer, a consistent picture of the mass, pore, and interfacial features of this material is presented. From a transmission‐electron‐microscopy image of an ultrathin section of vycor the material appears to have a homogeneous distribution of mass with no hierarchical organization. The pore interface exhibits a roughness which is probed by both small‐angle x‐ray scattering and Molecular Adsorption. The roughness has an upper cutoff of

Joseph Klafter - One of the best experts on this subject based on the ideXlab platform.

  • Molecular Adsorption on Porous Silica Gels from Binary Solutions
    Israel Journal of Chemistry, 1991
    Co-Authors: J.m. Drake, Pierre Levitz, Joseph Klafter
    Abstract:

    In this paper we present a detailed experimental study of Molecular Adsorption on interfaces of silica gels from binary solutions of alcohol/toluene. The Adsorption measurements are corroborated with infrared spectra of the surface hydroxyl groups and with NMR results. The Adsorption isotherms are analyzed within the framework of the Everett approach and possible scaling relations between alcohol monolayer capacities and adsorbate cross sections are discussed. We conclude that reliable morphological information on the interfaces cannot be obtained from these Adsorption experiments.

Bengt I Lundqvist - One of the best experts on this subject based on the ideXlab platform.

  • atomic and Molecular Adsorption on transition metal carbide 111 surfaces from density functional theory a trend study of surface electronic factors
    Journal of Physics: Condensed Matter, 2010
    Co-Authors: Aleksandra Vojvodic, Carlo Ruberto, Bengt I Lundqvist
    Abstract:

    This study explores atomic and Molecular Adsorption on a number of early transition-metal carbides (TMCs) in NaCl structure by means of density-functional theory calculations. The investigated substrates are the TM-terminated TMC(111) surfaces, of interest because of the presence of different types of surface resonances (SRs) on them and because of their technological importance in growth processes. Also, TM compounds have shown potential in catalysis applications. Trend studies are conducted with respect to both period and group in the periodic table, choosing the substrates ScC, TiC, VC, ZrC, NbC, delta-MoC, TaC, and WC (in NaCl structure) and the adsorbates H, B, C, N, O, F, NH, NH2, and NH3. Trends in Adsorption strength are explained in terms of surface electronic factors, by correlating the calculated Adsorption-energy values with the calculated surface electronic structures. The results are rationalized by use of a concerted-coupling model (CCM), which has previously been applied successfully to the description of Adsorption on TiC(111) and TiN(111) surfaces (Ruberto et al 2007 Solid State Commun. 141 48). First, the clean TMC(111) surfaces are characterized by calculating surface energies, surface relaxations, Bader charges, and surface-localized densities of states (DOSs). Detailed comparisons between surface and bulk DOSs reveal the existence of transition-metal localized SRs (TMSRs) in the pseudogap and of several C-localized SRs (CSRs) in the upper valence band on all considered TMC(111) surfaces. The spatial extent and the dangling bond nature of these SRs are supported by real-space analyses of the calculated Kohn-Sham wavefunctions. Then, atomic and Molecular Adsorption energies, geometries, and charge transfers are presented. An analysis of the adsorbate-induced changes in surface DOSs reveals a presence of both adsorbate-TMSR and adsorbate-CSRs interactions, of varying strengths depending on the surface and the adsorbate. These variations are correlated to the variations in Adsorption energies. The results are used to generalize the content and applications of the previously proposed CCM to this larger class of substrates and adsorbates. Implications for other classes of materials, for catalysis, and for other surface processes are discussed.

  • atomic and Molecular Adsorption on transition metal carbide 111 surfaces from density functional theory a trend study of surface electronic factors
    arXiv: Materials Science, 2010
    Co-Authors: Aleksandra Vojvodic, Carlo Ruberto, Bengt I Lundqvist
    Abstract:

    This study explores atomic and Molecular Adsorption on a number of early transition-metal carbides (TMC's) by means of density-functional theory calculations. Trend studies are conducted with respect to both period and group in the periodic table, choosing the substrates ScC, TiC, VC, ZrC, NbC, delta-MoC, TaC, and WC and the adsorbates H, B, C, N, O, F, NH, NH2, and NH3. Trends in Adsorption strength are explained in terms of surface electronic factors, by correlating the calculated Adsorption energy values with the calculated surface electronic structures. The results are rationalized with use of a concerted-coupling model (CCM), which has previously been applied succesfully to the description of Adsorption on TiC(111) and TiN(111) surfaces [Solid State Commun. 141, 48 (2007)]. First, the clean TMC(111) surfaces are characterized by calculating surface energies, surface relaxations, Bader charges, and surface-localized densities of states (DOS's). Detailed comparisons between surface and bulk DOS's reveal the existence of transition-metal localized SR's (TMSR's) in the pseudogap and of several C-localized SR's (CSR's) in the upper valence band on all considered TMC(111) surfaces. Then, atomic and Molecular Adsorption energies, geometries, and charge transfers are presented. An analysis of the adsorbate-induced changes in surface DOS's reveals a presence of both adsorbate--TMSR and adsorbate--CSR's interactions, of varying strengths depending on the surface and the adsorbate. These variations are correlated to the variations in Adsorption energies. The results are used to generalize the content and applications of the previously proposed CCM to this larger class of substrates and adsorbates. Implications for other classes of materials, for catalysis, and for other surface processes are discussed.