Mercury intrusion porosimetry

Question 1

What materials are measured using mercury porosimetry?

Answer 1

~ natural mineral particles, calcined aggregates and soft agglomerates that contain open pores and fissures

~ size distribution of these pores are from 200μm down to 5nm

Question 2

Why is mercury used?

Answer 2

~ it’s non-wetting to all solids

~ fluid is repelled rather than drawn into capillary pores

Question 2

Why is mercury used? How?

Answer 2

~ it’s non-wetting to all solids

~ fluid is repelled rather than drawn into capillary pores

~ an external pressure is required to force mercury into a capillary

Question 3

What is the Washburn equation?

Answer 3

~ p = -2γcosθ/r

~ γ: surface tension of mercury
~ cosθ: contact angle
~ r: cylindrical capillary radius

Question 4

How is mercury intrusion porosimetry done?

Answer 4

1. specimen is inserted into a chamber and the chamber is evacuated and then filled with mercury
2. pressure is increased in a step-wise fashion and the volume of mercury is measured via capacitance measurement in the capillary reservoir
3. the volume of liquid decreases (=increasing intruded volume) with increasing pressure, as pores of decreasing r are filled (p ∝ 1/r)
4. this will generate a cumulative penetration plot, or a fractional pore size distribution plot

Question 5

What does mercury intrusion porosimetry indicate for ink-bottle (constricted entrance) pores

Answer 5

~ it will indicate neck sizes

Question 6

What becomes an issue at higher pressures?

Answer 6

~ elastic/plastic compression of particles (small r)

Question 7

How is the extent of particle agglomeration indicated?

Answer 7

~ in a penetration volume plot