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Mercury Porosimetry Advantages and Limitations

Mercury Porosimetry Advantages and Limitations. Herbert Giesche New York State College of Ceramics at Alfred University. Outline:. Introduction / Theory The Measurement Technique Tips and Tricks Precision and Accuracy What Information do we get? Hysteresis Pore-Network Models

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Mercury Porosimetry Advantages and Limitations

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  1. Mercury PorosimetryAdvantages and Limitations Herbert Giesche New York State College of Ceramics at Alfred University NYSCC

  2. Outline: • Introduction / Theory • The Measurement Technique • Tips and Tricks • Precision and Accuracy • What Information do we get? • Hysteresis • Pore-Network Models • Alternative Techniques NYSCC

  3. But first, “Where on earth is Alfred ?” NYSCC

  4. What type or size of pore is measured ? Closed Pores Blind Pores Cross-linked Pores Through Pores In all cases, Hg-Porosimetry measures the largest available access to a pore, the size of the “entrance” towards a pore. Most times this is substantially smaller than the inner pore diameter! NYSCC

  5. Theory Essentially all calculations are based on the assumption of cylinder pores. This is a major assumption !!! NYSCC

  6. What are the basic parameters to be measured ? • Pressure • Intruded volume • Contact angle, θ • Surface tension, γ NYSCC

  7. Pressure • Pressure transducer have to cover the entire measurement range. (> 5 orders of magnitude !) • Use several transducer with overlapping ranges. • Avoid temperature drifts. • Avoid accidental over-range exposure. • Calibrate and check with “Standards” NYSCC

  8. Volume Measurement • The “antique” techniques: Optically Contact wire Resistance wire • Nowadays used in essentially all instruments:Precision capacitance bridge NYSCC

  9. Contact angle (which one ?) NYSCC

  10. Contact angle (cont.) • Bashforth-Adams tables • Max. Height • Anglometer NYSCC

  11. Contact angle (cont.) • Adjust θ in order to get close to N2-surface area Hg-Porosimetry N2-Adsorption Tungsten powder 0.11 0.10 Iron powder 0.20 0.30 Zinc dust 0.34 0.32 Copper powder 0.34 0.49 Silver iodide 0.48 0.53 Aluminum dust 1.35 1.14 Fluorspar 2.48 2.12 Iron oxide 14.3 13.3 Anatase 15.1 10.3 Graphitized carbon black 15.7 12.3 Boron nitride 19.6 20.0 Hydroxyapatite 55.2 55.0 Carbon black, Spheron-6 107.8 110.0 This assumes a reversible process ! It is strongly effected by small pores, even in minor quantities ! NYSCC

  12. The Instrument NYSCC

  13. Sample Cell and Calibration-kit NYSCC

  14. Tips and Tricks: Sample Preparation • Sample weight ??? • Heat treatment (?) • Evacuation (final vacuum & time) • Clean surfaces ! • Choice of ‘best’ penetrometer • Filling with mercury (head-pressure) • Use optimum switch-over between‘low’ and ‘high’ pressure port NYSCC

  15. Tips and Tricks (cont.) • Artificial pores due to sample positioningstainless steel wire as sample holder and as ‘separator’ • Space filler to reduce compressibility effects and amount of ‘wasted’ mercury. • Reactive metals (e.g. Zn, Ag, Pb) coated with stearic acidwith Cu a light oxidation might be sufficient • Watch out for compressibility of the sample:especially with highly porous sol-gel or polymer samples. NYSCC

  16. Removing Mercury • Repeat measurements on same sample after removing Hg at > 360°C under vacuum • Collect spilled Hg with Cu-wire brush (activated with HNO3 and dipping in mercury)“Quecksilber Teufel” • Or vacuum suction NYSCC

  17. Precision and Accuracy • < 1 – 2% for “data” in repeat tests • Contact angle uncertainty: • Surface tension value:Impurities can reduce γHg up to 20%Temperature has only a minor effect: 2.1 10-4 N/m °CPressure: γ(N/m) – 2.66 104 ΔP (MPa) e.g. up to 12% at 200 MPa • ! Temperature changes by up to 15°C during compression and expansion;  volume changes NYSCC

  18. Kinetic Effects • Time for mercury to move through pores • Over-pressure is needed • Smaller pore take longer Example: 110% injection pressurePore radius 0.5 to 50 μm NYSCC

  19. Equilibration rate - example NYSCC

  20. Equilibration rate - example Pore Volume (cm3/g) Pore diameter (m) • 0 seconds 0.5823 0.0081 • 2 seconds 0.5938 0.0089 • 10 seconds 0.5939 0.0095 • 30 seconds 0.6161 0.0098 • 0.001 l/g-sec 0.6210 0.0102 NYSCC

  21. Equilibration Kinetics of FCC-catalyst NYSCC

  22. Equilibration Kinetics of FCC-catalyst (Intrusion) NYSCC

  23. Equilibration Kinetics of FCC-catalyst (Extrusion) NYSCC

  24. What Information do we get? • Pore Size (which size ??) • Pore Volume • Density (bulk, skeletal, or at various stages) • Compressibility • Surface Area • Particle Size • Pore Shape (?) • Pore Connectivity (?) NYSCC

  25. Compressibility NYSCC

  26. Compressibility (cont.) NYSCC

  27. What Information do we get? • Pore Size (which size ??) • Pore Volume • Density (bulk, skeletal, or at various stages) • Compressibility • Surface Area • Particle Size • Pore Shape (?) • Pore Connectivity (?) NYSCC

  28. Particle Size (?) • We use the inter-particle pore size as an estimation of the particle size (Mayer & Stove) NYSCC

  29. Particle Size (cont.) • Pore size  particle size (as shown)This is highly dependent on the particle packing characteristics (particle shape, stickiness, compaction pressure, etc.) Approximation: pore = 20% of particle size • Alternatively we use the calculated surface area to convert this into an equivalent particle size NYSCC

  30. What Information do we get? • Pore Size (which size ??) • Pore Volume • Density (bulk, skeletal, or at various stages) • Compressibility • Surface Area • Particle Size • Pore Shape (?) • Pore Connectivity (?) NYSCC

  31. Pore Shape and Pore Networks • Intrusion describes primarily the pore opening or entrance • Hysteresis is caused by: • Network effects • Pore shape (or pore connections) • Surface properties (contact angle effects) • Permeability (flow through) provides additional information (check for simulations) NYSCC

  32. Hysteresis and Pore-Shape NYSCC

  33. Hysteresis due to Surface ChemistryAlumina sample coated with Cu-sulfate Intrusion: a) for all samples Extrusion: b) untreated c) 0.5% d) 2% e) 40% CuSO4 NYSCC

  34. Network modelsMercury intrusion in model porous media.By C. Tsakiroglou and A. Payatakes; Adv. Colloid Interface Sci; 75, 215-53 (1998) NYSCC

  35. Network modelsMercury retraction in model porous media. By C. Tsakiroglou and A. Payatakes; Adv. Colloid Interface Sci; 75, 215-53 (1998) NYSCC

  36. “Snap-off in ‘lenticular’ Throats”By C. Tsakiroglou and A. Payatakes; Adv. Colloid Interface Sci; 75, 215-53 (1998) NYSCC

  37. Pore-Connectivity / Network - EffectBy C. Tsakiroglou and A. Payatakes; Adv. Colloid Interface Sci; 75, 215-53 (1998) Initial stage ↓ Final stage NYSCC

  38. Cylindrical Pore1 μm diameter; Θ = 140°; γ = 0.48 N/m Conical-Cylinder Pore “Energy Barrier Model” NYSCC

  39. Pore-Cor Simulation Model • Generates a 3-D representation of the pore space using information derived directly from mercury intrusion data. • PoreCor data reduction shows: • porosity • pore connectivity • pore throat correlation • pore tortuosity • absolute gas permeability • (gas diffusion through a dry sample) • trapping of non-wetting fluids sandstone sample: showing mercury intrusion (grey), after injection by polymer (blue). Yellow volumes are empty. NYSCC

  40. Complimentary Porosity Characterization Techniques • Microscopy • Permeability measurements • Infiltration tests: • Wood’s metal • Water or other liquids • CT (computer tomography) • NMR studies of relaxation times • Light Scattering, SAXS (and SANS) NYSCC

  41. Conclusions • Hg-Porosimetry uniqueness; it covers 5 orders of magnitude; from mm to nm. • Safety and Environmental concerns; manageable. • Remember: Intrusion = Pore Entrance • Hysteresis may lead to understanding of pore shape and connectivity. • Work on model pore structures is needed to gain more understanding. • New simulation software offers great possibilities; but use with caution !! NYSCC

  42. Thanks for your interest and thanks to the organizer for the opportunity to be here! Literature • H. Giesche; Chapter 2.7 in ‘Handbook of Porous Solids’, Wiley (2002) Overview article • H. Giesche, et.al.; Colloid & Surfaces, 37, 93-113 (1989) Ordered silica sphere structures • C. Tsakiroglou et.al.; Adv. Colloid Interface Sci; 75 215-53 (1998) 2-D model pore structures; experiments & simulations Others not specifically referenced in this presentation: • Sean Rigby; numerous publications over the last 5 yearsNetwork models for hysteresis effects; experiments and interpretation • Peter Matthew; numerous publications over the last 10 years‘Pore Core’ simulation model • Geoffrey Mason; numerous publications over the last 20 yearsSurface curvature; intrusion and extrusion in simple rod-plate structures • Powder Technology, Vol. 29 (1981), special issue Hg-porosimetry NYSCC

  43. Literature Literature Thanks for your interest and thanks to the organizer for the opportunity to be here! • H. Giesche; Chapter 2.7 in ‘Handbook of Porous Solids’, Wiley (2002) Overview article • H. Giesche, et.al.; Colloid & Surfaces, 37, 93-113 (1989) Ordered silica sphere structures • C. Tsakiroglou et.al.; Adv. Colloid Interface Sci; 75 215-53 (1998) 2-D model pore structures; experiments & simulations Others not specifically referenced in this presentation: • Sean Rigby; numerous publications over the last 5 yearsNetwork models for hysteresis effects; experiments and interpretation • Peter Matthew; numerous publications over the last 10 years‘Pore Core’ simulation model • Geoffrey Mason; numerous publications over the last 20 yearsSurface curvature; intrusion and extrusion in simple rod-plate structures • Powder Technology, Vol. 29 (1981), special issue Hg-porosimetry http://people.alfred.edu/~giesche/Publications.htm NYSCC

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