Pore Size Analysis Using
Liquid Methods
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What can be measured using these techniques?
Who would be interested in such results?
A brief overview of measurement fundamentals.
Meso-/macroporous solids
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Ceramics
Batteries and Fuel Cells
Geological samples
Cement, concrete, stone and bricks
Pharmaceuticals
Filters
Membranes
• Instrument selection for these materials
• Specific features of benefit to such materials
Pore Size Analysis Using
Liquid Methods
• What can be measured using these
techniques?
– Pore size distributions (meso/macro, not micro)
– Pores too large for gas sorption
– Through-pores (porometry)
• Who would be interested in such results?
– Anyone who forms powders into solids
– Anyone who makes non-woven fabrics
– Membrane manufacturers
Meso-/macroporous solids
– Ceramics
• Strength, absorbence, filtration
– Batteries and Fuel Cells
• Electrolyte contact, separator efficiency
– Geological samples
• Oil and gas, strength, liquid permeation
– Cement, concrete, stone and bricks
• Curing, strength, freeze/thaw resistance
– Pharmaceuticals
• Tablet structure, strength, dissolution
– Filters & Membranes
• Efficiency
Ceramics
Bioceramics
Battery Pores
Electrode Pores
Separator Pores
Geological
sandstone
Diatomaceous earth
Cement, Concrete, Mortar etc
Pharmaceuticals
Tablet porosity provides pathways for the penetration of fluid into tablets. The
disintegrant particles (with low cohesiveness & compressibility) themselves act to
enhance porosity and provide these pathways into the tablet. Liquid is drawn up
or “wicked” into these pathways through capillary action and rupture the
interparticulate bonds causing the tablet to break apart.
Pharmaceuticals
Filters & Membranes
Nitrocellulose membrane
Filters & Membranes
Washburn methods
Wetting / Contact Angles
Wetting  < 90
Non-wetting  > 90
Washburn Equation
Pr  2 cos
  480 N / m
and

  140
0.736
P
r
Where P is in MPa and r in µm
Sample Cell
Max measurable intrusion volume
The sample cell or
penetrometer (sometimes
called a dilatometer) is
used both to contain the
sample and to facilitate
the measurement of
intrusion and extrusion
volumes.
Low Pressure Intrusion
Mercury level sensor
Pressure transducer
Dry gas (e.g. 400 kPa)
Metal cap
Sample
Vacuum
Cold trap
Volume (capacitance)
sensing circuit
Concentric sheath
Mercury reservoir
High Pressure Intrusion
Check valve
Oil return line
Rupture disk
Cylinder
Oil filter
Polished shaft
Oil pump
Worm gear
Contact electrode
Oil reservoir
Pressure transducer
Motor
and gearbox
Volume
Increasing Pressure Causes Intrusion
Pressure
Pressure
Mercury Porosimetry - Overview
Intrusion into
internal pores
volume
Compression
of solid (rare)
Intrusion into
powder voids
Powder compaction
Apparent pore size (log scale)
Results Overview
Hysteresis
• Intrusion curves are not retraceable.
(Extrusion curves lie above the intrusion curve)
• Can be explained by changes in  between
intrusion and extrusion.
•Some mercury remains in the pores…
Entrapment
• Mercury left behind in the pores:
entrapment.
• Entrapment ceases after the first
few cycles.
• Complex network of pores responsible
for such entrapment.
THE state-of-the-art porometer
sample holders support the sample
Real-time data presentation
Repeatability
Application/Technique Selector
Mercury
Porosimeter
3D structures

Capillary
Porometer
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2D structures
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
What Defines a Mercury Intrusion
Porosimeter?
• Pressure Range
– Lowest pressure defines largest pore.
– Highest pressure defines smallest pore.
• NOTE: Effect of Contact Angle
– A lower contact angle shifts pore size range to
smaller values. Merely mathematical.
– A higher contact angle shifts pore size to
larger values. Merely mathematical.
The 3G Series
3G micro
Pore size minimum
0.09 µm
or 0.06 µm
3G Macro
3G z
3G zh
0.09 µm
<0.04 µm
<0.02 µm
Pore size maximum
100 µm
>500 µm
500 µm
500 µm
Pressure controllers
1
2
2
2
0-5 psi
0-30 psi
0-30 psi
n/a
0-100 psi
0-300 psi
0-500 psi
2
2
3
3
Sensor #1
0-5 psi
0-5 psi
0-5 psi
0-5 psi
Sensor #2
0-100 psi
or 0-150 psi
0-100 psi
0-100 psi
0-100 psi
Sensor #3
n/a
n/a
0-250 psi
0-500 psi
1
1
1 or 2
2
0-200 L/min
0-100 L/min
0-10 L/min
n/a
n/a
Optional 5, 50,
200 L/min
0-200 L/min
n/a
n/a
manual
Controller #1
Controller #2
Pressure sensors
Flow sensors
Sensor #1
Sensor #2
Flow sensor
switching
0-100 psi
or 0-150 psi
0-100 L/min
or 0-200 L/min
or 0-20 L/min
auto