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 sandstoneDiatomaceous 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 and 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 sensor Pressure 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
Pressure Volume Increasing Pressure Causes Intrusion
Mercury Porosimetry - Overview Apparent pore size (log scale) volume 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 Series3G micro3G Macro3G z3G zh Pore size minimum 0.09 µm or 0.06 µm 0.09 µm<0.04 µm<0.02 µm Pore size maximum100 µm>500 µm500 µm Pressure controllers1222 Controller # psi or psi 0-5 psi0-30 psi Controller #2 n/a psi0-300 psi0-500 psi Pressure sensors2233 Sensor #10-5 psi Sensor # psi or psi psi Sensor #3n/a psi0-500 psi Flow sensors111 or 22 Sensor # L/min or L/min or 0-20 L/min L/min0-100 L/min0-10 L/min Sensor #2 n/a Optional 5, 50, 200 L/min L/min Flow sensor switching n/a manual auto