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Title: Studies of Dynamical Layering in Adsorbed Organic Films

Abstract

We are using state-of-the-art quasi-elastic neutron scattering (QNS) to study how molecular diffusive motion in prototypical films may correlate with their lubricating properties. Our experiments have demonstrated that the High Flux Backscattering Spectrometer at the National Institute of Standards and Technology Center for Neutron Research has sufficient energy resolution and throughput for probing relatively slow diffusive motions in molecular monolayers of model lubricants such as tetracosane (C{sub 24}H{sub 50} or C24). In particular, these measurements are sensitive to the molecular conformation al dynamics on a nanosecond time scale. It is well known from experiments using a surface force apparatus that organic fluids confined between two surfaces exhibit a layered structure at the molecular level. This static layering has motivated us to consider the possibility that the individual molecular layers in fluid films may also have different dynamical properties. Here we report high-resolution QNS measurements on fluid monolayer, bilayer, and trilayer films of C24 adsorbed on exfoliated graphite (Grafoil). The results indicate slower molecular diffusive motion in the bottom layer of a bilayer C24 film compared to that in a monolayer, while the rate of diffusive motion in the bottom two layers of the trilayer film is comparable to that inmore » a monolayer.« less

Authors:
 [1];  [1];  [1];  [2];  [3];  [3];  [4];  [5]
  1. University of Missouri, Columbia
  2. Technical University of Denmark
  3. National Institute of Standards and Technology (NIST)
  4. ORNL
  5. Pontifica Universidad Catolica de Chile
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
931457
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Conference
Resource Relation:
Conference: The Eighth International Conference on Quasi-Elastic Neutron Scattering, Bloomington, IN, USA, 20060614, 20060617
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; BACKSCATTERING; ENERGY RESOLUTION; GRAPHITE; LUBRICANTS; LUBRICATION; NEUTRONS; SCATTERING; SPECTROMETERS; SURFACE FORCES

Citation Formats

Diama, A, Simpson, M., Taub, H., Hansen, F.Y., Dimeo, R. M., Neumann, D. A., Herwig, Kenneth W, and Volkmann, U. G.. Studies of Dynamical Layering in Adsorbed Organic Films. United States: N. p., 2007. Web.
Diama, A, Simpson, M., Taub, H., Hansen, F.Y., Dimeo, R. M., Neumann, D. A., Herwig, Kenneth W, & Volkmann, U. G.. Studies of Dynamical Layering in Adsorbed Organic Films. United States.
Diama, A, Simpson, M., Taub, H., Hansen, F.Y., Dimeo, R. M., Neumann, D. A., Herwig, Kenneth W, and Volkmann, U. G.. Mon . "Studies of Dynamical Layering in Adsorbed Organic Films". United States. doi:.
@article{osti_931457,
title = {Studies of Dynamical Layering in Adsorbed Organic Films},
author = {Diama, A and Simpson, M. and Taub, H. and Hansen, F.Y. and Dimeo, R. M. and Neumann, D. A. and Herwig, Kenneth W and Volkmann, U. G.},
abstractNote = {We are using state-of-the-art quasi-elastic neutron scattering (QNS) to study how molecular diffusive motion in prototypical films may correlate with their lubricating properties. Our experiments have demonstrated that the High Flux Backscattering Spectrometer at the National Institute of Standards and Technology Center for Neutron Research has sufficient energy resolution and throughput for probing relatively slow diffusive motions in molecular monolayers of model lubricants such as tetracosane (C{sub 24}H{sub 50} or C24). In particular, these measurements are sensitive to the molecular conformation al dynamics on a nanosecond time scale. It is well known from experiments using a surface force apparatus that organic fluids confined between two surfaces exhibit a layered structure at the molecular level. This static layering has motivated us to consider the possibility that the individual molecular layers in fluid films may also have different dynamical properties. Here we report high-resolution QNS measurements on fluid monolayer, bilayer, and trilayer films of C24 adsorbed on exfoliated graphite (Grafoil). The results indicate slower molecular diffusive motion in the bottom layer of a bilayer C24 film compared to that in a monolayer, while the rate of diffusive motion in the bottom two layers of the trilayer film is comparable to that in a monolayer.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}

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