Pore Size Analysis Using Liquid Methods

• What can be measured using these techniques?• Who would be interested in such results?• A brief overview of measurement fundamentals.• Meso-/macroporous solids

– 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 & MembranesNitrocellulose membrane

Filters & Membranes

Washburn methods

Wetting / Contact Angles

Wetting < 90

Non-wetting > 90

Washburn Equation

cos2Pr

m/N480 140and

r

736.0P

Where P is in MPa and r in µm

Sample Cell

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.

Max measurable intrusion volume

Low Pressure Intrusion

Volume (capacitance) sensing circuit

Mercury reservoir

Vacuum

Cold trap

Sample

Metal cap

Concentric sheath

Mercury level sensorPressure transducer

Dry gas (e.g. 400 kPa)

High Pressure Intrusion

Pressure transducer

Cylinder

Polished shaft

Motor and gearbox

Worm gear

Check valve

Rupture disk

Oil return line

Oil filter

Oil reservoir

Oil pump

Contact electrode

PressurePressure

Vol

ume

Increasing Pressure Causes Intrusion

Mercury Porosimetry - Overview

Apparent pore size (log scale)

volu

me

Powder compaction

Intrusion into powder voids

Intrusion into internal pores

Compression of solid (rare)

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

Capillary Porometer

3D structures -

2D structures -

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 3G Macro 3G z 3G zh

Pore size minimum 0.09 µm or 0.06 µm

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

Controller #1 0-100 psi or 0-150 psi

0-5 psi 0-30 psi 0-30 psi

Controller #2 n/a 0-100 psi 0-300 psi 0-500 psi

Pressure sensors 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

Flow sensors 1 1 1 or 2 2

Sensor #1 0-100 L/min or 0-200 L/min or 0-20 L/min

0-200 L/min 0-100 L/min 0-10 L/min

Sensor #2n/a n/a

Optional 5, 50, 200 L/min

0-200 L/min

Flow sensor switching

n/a n/a manualauto