observation of pore scale liquid behavior with nir-microscopy and advanced laser techniques markus...
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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
Microscopic Observation of Capillary Condensation in Glass Micromodels
Dew Point Generator
Temperature Controller
Video Microscope
MicroscopeControl Units
HeatExchangerSealed
Chamber
A high resolution video microscope (1000x) with black&white 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.
Environmentally Controlled Observation Chamber
VideoMicroscope
IR Backlight880 nm
Thermistor
Glass Model
SampleManipulator
Chamberwith
Water Jacket
X-Y Positioning Stage
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.
A LI-COR dew point generator with an accuracy of 0.02 oC was used to control the vapor pressure within the observation chamber.
Observation of Capillary Menisci in Micro Glass Beads
The experimental setup was tested with micro glass beads having an average diameter of 325 m.
Observed capillary menisci for various chemical potentials were compared with calculated menisci obtained from solutions of the Young-Laplace equation for pendular water.
- 3500 J/kg - 4500 J/kg - 7000 J/kg - 12000 J/kg - 25000 J/kg
0
400
800
400 8000
[m]
[m
]
- 4500 J/kg
a Glass bead radius [m] Liquid-vapor surface tension [N/m] Liquid density [kg/m3] Chemical potential [J/kg]
Observation of Capillary Menisci and Liquid Redistribution in Micro Glass Cells
0
0.4
0.8
1.2
1.6
0 0.5 1 1.5 2 2.5[mm]
[mm
]
- 0.25 J/kg
- 0.16 J/kg- 0.16 J/kg
- 0.15 J/kg
- 0.18 J/kg
- 0.28 J/kg - 0.18 J/kg - 0.16 J/kg- 0.17 J/kg - 0.21 J/kg
Quasi equilibriumNon equilibrium
- 0.19 J/kg
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:
Laser Interferometer
EllipsometryFor layers from 0.5 nm to 10 nm
InterferometryFor layers from 10 nm to 1 m
Phase-Contrast MicroscopyResolution down to 2 m
Diffraction Analysis
Conceptual Sketch of the Experimental Setup
Reflectometry for Measurement of Film Thickness
IlluminationFibers
ReadFiber
ReflectionProbe
Probe Holder
Quartz Sample
Pulsed XenonLight Source
ReflectanceSpectrum
EXPERIMENTAL SETUP
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.
Reflectometry – Preliminary Results
Air Between Quartz Slides (38 mm Spacers)
Air Between Quartz Slides (No Spacers)
h=12.4 m
h=41.6 m
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.
Model Prototype
45 m
Diffraction Order
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
Re
lati
ve
Op
tic
al
Po
we
r
10-8
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
101
Diffraction Order
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
Re
lati
ve
Op
tic
al
Po
we
r
10-8
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
101
DRY WET
Theoretically Derived Diffraction Patterns for Dry and Liquid-Filled Periodical Structures
Diffraction Order
0 1 2 3 4 5
Rel
ativ
e O
pti
cal P
ow
er
10-8
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
101
DryWet
Measured Diffraction Patterns for Dry and Liquid-Filled Periodical Structures