Mercury Porosimetry Advantages and Limitations Herbert Giesche New

Mercury Porosimetry Advantages and Limitations Herbert Giesche New York State College of Ceramics at Alfred University NYSCC Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

Outline: • Introduction / Theory • The Measurement Technique – Tips and Tricks – Precision and Accuracy • • NYSCC What Information do we get? Hysteresis Pore-Network Models Alternative Techniques Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

But first, “Where on earth is NYSCC Porotec Workshop 15 & 16 th Nov. 2004 Alfred ? ” Alfred University

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 Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

Theory Essentially all calculations are based on the assumption of cylinder pores. This is a major assumption !!! NYSCC Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

What are the basic parameters to be measured ? • Pressure • Intruded volume • Contact angle, θ • Surface tension, γ NYSCC Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

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 Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

Volume Measurement • The “antique” techniques: Optically Contact wire Resistance wire • Nowadays used in essentially all instruments: Precision capacitance bridge NYSCC Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

Contact angle (which one ? ) NYSCC Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

Contact angle (cont. ) • Bashforth-Adams tables • Anglometer • Max. Height NYSCC Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

Contact angle (cont. ) • Adjust θ in order to get close to N 2 -surface area Hg-Porosimetry Tungsten powder Iron powder Zinc dust 0. 34 Copper powder Silver iodide Aluminum dust Fluorspar 2. 48 Iron oxide Anatase Graphitized carbon black Boron nitride Hydroxyapatite Carbon black, Spheron-6 NYSCC 0. 11 0. 20 0. 32 0. 34 0. 48 1. 35 2. 12 14. 3 15. 1 15. 7 19. 6 55. 2 107. 8 N 2 -Adsorption 0. 10 0. 30 0. 49 0. 53 1. 14 13. 3 10. 3 This assumes a reversible process ! 12. 3 20. 0 It is strongly effected by small pores, 55. 0 even in minor quantities ! 110. 0 Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

The Instrument NYSCC Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

Sample Cell and Calibration-kit NYSCC Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

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 Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

Tips and Tricks (cont. ) • Artificial pores due to sample positioning stainless 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 acid with Cu a light oxidation might be sufficient • Watch out for compressibility of the sample: especially with highly porous sol-gel or polymer samples. NYSCC Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

Removing Mercury • Repeat measurements on same sample after removing Hg at > 360°C under vacuum • Collect spilled Hg with Cu-wire brush (activated with HNO 3 and dipping in mercury) “Quecksilber Teufel” • Or vacuum suction NYSCC Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

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 °C Pressure: 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 Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

Kinetic Effects • Time for mercury to move through pores • Over-pressure is needed • Smaller pore take longer Example: 110% injection pressure Pore radius 0. 5 to 50 μm NYSCC Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

Equilibration rate - example NYSCC Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

Equilibration rate - example Pore Volume (cm 3/g) • • • 0 seconds 2 seconds 10 seconds 30 seconds 0. 001 l/g-sec NYSCC 0. 5823 0. 5938 0. 5939 0. 6161 0. 6210 Porotec Workshop 15 & 16 th Nov. 2004 Pore diameter ( m) 0. 0081 0. 0089 0. 0095 0. 0098 0. 0102 Alfred University

Equilibration Kinetics of FCC-catalyst NYSCC Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

Equilibration Kinetics of FCC-catalyst (Intrusion) NYSCC Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

Equilibration Kinetics of FCC-catalyst (Extrusion) NYSCC Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

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 Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

Compressibility NYSCC Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

Compressibility (cont. ) NYSCC Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

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 Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

Particle Size (? ) • We use the inter-particle pore size as an estimation of the particle size (Mayer & Stove) NYSCC Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

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 Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

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 Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

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 Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

Hysteresis and Pore-Shape NYSCC Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

Hysteresis due to Surface Chemistry Alumina sample coated with Cu-sulfate Intrusion: a) for all samples Extrusion: b) untreated c) 0. 5% d) 2% e) 40% Cu. SO 4 NYSCC Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

Network models Mercury intrusion in model porous media. By C. Tsakiroglou and A. Payatakes; Adv. Colloid Interface Sci; 75, 215 -53 (1998) NYSCC Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

Network models Mercury retraction in model porous media. By C. Tsakiroglou and A. Payatakes; Adv. Colloid Interface Sci; 75, 215 -53 (1998) NYSCC Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

“Snap-off in ‘lenticular’ Throats” By C. Tsakiroglou and A. Payatakes; Adv. Colloid Interface Sci; 75, 215 -53 (1998) NYSCC Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

Pore-Connectivity / Network - Effect By C. Tsakiroglou and A. Payatakes; Adv. Colloid Interface Sci; 75, 215 -53 (1998) Initial stage ↓ Final stage NYSCC Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

“Energy Barrier Model” Conical-Cylinder Pore Cylindrical Pore 1 μm diameter; Θ = 140°; γ = 0. 48 N/m Length Intrusion Extrusion μm MPa 100 0. 735 0. 726 1. 01 10 0. 735 0. 650 1. 13 5 0. 735 0. 566 1. 31 2 0. 735 0. 309 2. 78 1. 5 0. 735 0. 166 7. 58 1. 4 0. 735 0. 050 14. 66 NYSCC PI/PE Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

Pore-Cor Simulation Model Generates a 3 -D representation of the pore space using information derived directly from mercury intrusion data. Pore. Cor 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 Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

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 Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

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 Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

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) • • Thanks for your interest Ordered silica sphere structures and C. Tsakiroglou et. al. ; Adv. Colloid Interface Sci; 75 215 -53 thanks organizer for the (1998) 2 -D modelto porethe structures; experiments & simulations Others not specifically referenced in this presentation: opportunity to be here! Sean Rigby; numerous publications over the last 5 years Network 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 years Surface curvature; intrusion and extrusion in simple rod-plate structures • Powder Technology, Vol. 29 (1981), special issue Hg-porosimetry NYSCC Porotec Workshop 15 & 16 th Nov. 2004 Alfred University

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) • • Thanks for your interest Ordered silica sphere structures and C. Tsakiroglou et. al. ; Adv. Colloid Interface Sci; 75 215 -53 (1998) 2 -D model pore structures; experiments & simulations thanks to the organizer for the Others not specifically referenced in this presentation: Sean Rigby; numerous publications over here! the last 5 years opportunity to be Network 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 years Surface 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 Porotec Workshop 15 & 16 th Nov. 2004 Alfred University