Observation of Pore Scale Liquid Behavior with NIR-Microscopy and Advanced Laser Techniques Markus Tuller and Dani Or Dept. of Plants, Soils and Biometeorology, Utah State University

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Observation of Pore Scale Liquid Behavior with
NIR-Microscopy and Advanced Laser Techniques
Markus Tuller and Dani OrDept. of Plants, Soils
and Biometeorology, Utah State University
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Microscopic Observation of Capillary Condensation
in Glass Micromodels

• A high resolution video microscope (1000x) with
  blackwhite CCD camera was used to detect liquid
  configurations using IR light (880 nm) emitted
  from a LED light source (capitalizing on water
  adsorption properties at this wavelength).

• A narrow bandpass interference filter with a
  central wavelength of 880 nm was installed on the
  CCD camera to increase image contrast for water.
• The observations were performed in a temperature
  and vapor pressure controlled chamber.

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Environmentally Controlled Observation Chamber

• A LI-COR dew point generator with an accuracy of
  0.02 oC was used to control the vapor pressure
  within the observation chamber.

• A temperature controller connected to a
  thermistor and two thermoelectric Peltier cooling
  elements are used to maintain a constant
  temperature within the chamber.
• Two heat exchangers connected to two closed water
  loops are attached to the hot and cool sides
  of the Peltier plates.
• One loop is guided through the water jacket
  surrounding the observation chamber, and the
  second loop is connected to a larger water
  reservoir.

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Observation of Capillary Menisci in Micro Glass
Beads

• The experimental setup was tested with micro
  glass beads having an average diameter of 325 mm.
• Observed capillary menisci for various chemical
  potentials were compared with calculated menisci
  obtained from solutions of the Young-Laplace
  equation for pendular water.

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Observation of Capillary Menisci and Liquid
Redistribution in Micro Glass Cells
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Advanced Techniques to Measure Thickness and
Configuration of Adsorbed Liquid Films

• Several micro-scale techniques will be applied to
  measure the thickness of adsorbed liquid films.
• Currently we are testing the following methods to
  measure the structure of surface water on
  channeled silica substrates

• EllipsometryFor layers from 0.5 nm to 10 nm
• InterferometryFor layers from 10 nm to 1 mm
• Phase-Contrast MicroscopyResolution down to 2 mm
• Diffraction Analysis

Conceptual Sketch of the Experimental Setup
Laser Interferometer
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Reflectometry for Measurement of Film Thickness

• A miniature fiber optic spectrometer (Ocean
  Optics PC2000) with high-performance CCD-array
  detector and high-speed A/D converter is used to
  measure the reflectance spectrum of thin films
  coating solid substrates.

• All measurements are conducted with an incidence
  angle perpendicular to the sample surface and
  relative to a standard sample with known absolute
  reflectance.

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Reflectometry Preliminary Results
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Diffraction Analysis to Determine
LiquidConfigurations within Periodic Structures

• Analysis of the diffraction pattern is used to
  determine the average interfacial curvature of
  liquid, filling the periodic structure.

Measured Diffraction Patterns for Dry and
Liquid-Filled Periodical Structures