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

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

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

Alfred UniversityPorotec Workshop 15 & 16 th Nov. 2004NYSCC 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!

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

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

Alfred UniversityPorotec Workshop 15 & 16 th Nov. 2004NYSCC 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”

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

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

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

Alfred UniversityPorotec Workshop 15 & 16 th Nov. 2004NYSCC Contact angle (cont.) Adjust θ in order to get close to N 2 -surface area Hg-PorosimetryN 2 -Adsorption Tungsten powder Iron powder Zinc dust Copper powder Silver iodide Aluminum dust Fluorspar Iron oxide Anatase Graphitized carbon black Boron nitride Hydroxyapatite Carbon black, Spheron This assumes a reversible process ! It is strongly effected by small pores, even in minor quantities !

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

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

Alfred UniversityPorotec Workshop 15 & 16 th Nov. 2004NYSCC 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

Alfred UniversityPorotec Workshop 15 & 16 th Nov. 2004NYSCC 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.

Alfred UniversityPorotec Workshop 15 & 16 th Nov. 2004NYSCC 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

Alfred UniversityPorotec Workshop 15 & 16 th Nov. 2004NYSCC Precision and Accuracy < 1 – 2% for “data” in repeat tests Contact angle uncertainty: Surface tension value: Impurities can reduce γ Hg up to 20% Temperature has only a minor effect: N/m °C Pressure : γ (N/m) – ΔP (MPa) e.g. up to 12% at 200 MPa ! Temperature changes by up to 15°C during compression and expansion;  volume changes

Alfred UniversityPorotec Workshop 15 & 16 th Nov. 2004NYSCC 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

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

Alfred UniversityPorotec Workshop 15 & 16 th Nov. 2004NYSCC Equilibration rate - example Pore Volume (cm3/g) Pore diameter (  m) 0 seconds seconds seconds seconds  l/g-sec

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

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

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

Alfred UniversityPorotec Workshop 15 & 16 th Nov. 2004NYSCC 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 (?)

Alfred UniversityPorotec Workshop 15 & 16 th Nov. 2004NYSCC Compressibility

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

Alfred UniversityPorotec Workshop 15 & 16 th Nov. 2004NYSCC 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 (?)

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

Alfred UniversityPorotec Workshop 15 & 16 th Nov. 2004NYSCC 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

Alfred UniversityPorotec Workshop 15 & 16 th Nov. 2004NYSCC 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 (?)

Alfred UniversityPorotec Workshop 15 & 16 th Nov. 2004NYSCC 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)

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

Alfred UniversityPorotec Workshop 15 & 16 th Nov. 2004NYSCC 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% CuSO 4

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

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

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

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

Alfred UniversityPorotec Workshop 15 & 16 th Nov. 2004NYSCC “Energy Barrier Model” LengthIntrusionExtrusionP I /P E μmμmMPa Conical-Cylinder PoreCylindrical Pore 1 μm diameter; Θ = 140°; γ = 0.48 N/m

Alfred UniversityPorotec Workshop 15 & 16 th Nov. 2004NYSCC Pore-Cor Simulation Model sandstone sample: showing mercury intrusion (grey), after injection by polymer (blue). Yellow volumes are empty. 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

Alfred UniversityPorotec Workshop 15 & 16 th Nov. 2004NYSCC 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)

Alfred UniversityPorotec Workshop 15 & 16 th Nov. 2004NYSCC 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 !!

Alfred UniversityPorotec Workshop 15 & 16 th Nov. 2004NYSCC 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, (1989) Ordered silica sphere structures C. Tsakiroglou et.al.; Adv. Colloid Interface Sci; (1998) 2-D model pore structures; experiments & simulations Others not specifically referenced in this presentation: 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

Alfred UniversityPorotec Workshop 15 & 16 th Nov. 2004NYSCC Literature H. Giesche; Chapter 2.7 in ‘Handbook of Porous Solids’, Wiley (2002) Overview article H. Giesche, et.al.; Colloid & Surfaces, 37, (1989) Ordered silica sphere structures C. Tsakiroglou et.al.; Adv. Colloid Interface Sci; (1998) 2-D model pore structures; experiments & simulations Others not specifically referenced in this presentation: 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 Literature Thanks for your interest and thanks to the organizer for the opportunity to be here!