Advances In Characterization Techniques

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Advances In Characterization Techniques

• Dr. Krishna Gupta
• Technical Director
• Porous Materials, Inc., USA

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Topics

• Flow Porometry

• Accuracy and Reproducibility
• Technology for Characterization under Application
  Environment
• Directional Porometry
• Clamp-On Porometry
• Flexibility to Accommodate Samples of Wide
  Variety of Shapes, Sizes and Porosity
• Ease of Operation

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Topics

• Permeametry

• Diffusion Gas Permeametry
• High Flow Gas Permeametry
• Microflow liquid permeametry
• High flow liquid permeametry at high temperature
  high presure
• Envelope surface area, average particle size
  average fiber diameter analysis
• Water vapor transmission rate

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Topics

• Mercury Intrusion Porosimetry

• Stainless steel sample chamber
• Special design to minimize contact with mercury
• Non-Mercury Intrusion Porosimetry
• Sample chamber that permits mercury intrusion
  porosimeter to be used as non-mercury intrusion
  porosimeter
• Water Intrusion Porosimeter

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Topics

• Gas Adsorption

• Conclusions

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Flow Porometry (Capillary Flow Porometry)

• Accuracy and Reproducibility
• Most important sources of random systematic
  errors identified

• Design modified to minimized errors
• Appropriate corrections incorporated

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Flow Porometry(Capillary Flow Porometry)

• Accuracy

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Flow Porometry(Capillary Flow Porometry)

• Repeatability
• Bubble point repeated 32 times

• Same operator
• Same machine
• Same wetting liquid
• Same filter

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Flow Porometry(Capillary Flow Porometry)
Filter Wetting Liquid Wetting Liquid
Filter Porewick Silwick
Sintered Stainless Steel 1.8 1.2
Battery Separator 0.2 1.5
Paper 1.7 1.1
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Flow Porometry(Capillary Flow Porometry)

• Errors due to the use of different machines

Machine Bubble point pore diameter, Mean Value, mm Standard deviation Deviation from average of all machines
1 18.35 0.53 -1.34
2 18.78 0.48 0.93
3 18.37 2.34 0.28
4 18.63 0.75 0.13
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Flow Porometry(Capillary Flow Porometry)

• Operator errors

Machine Average of mean, mm Difference between mean values by operators Difference between mean values by operators
Machine Average of mean, mm mm Percentages
1 18.38 0.058 0.32
2 18.77 0.005 0.03
3 18.77 0.222 1.19
4 18.73 0.213 1.14
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Technology for Characterization under Simulated
Application Environment

• Compressive Stress
• Arrangement for testing sample under compressive
  stress

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Technology for Characterization under Simulated
Application Environment
Compressive Stress

• Features
• Any compressive stress up to 1000 psi (700 kPa)

• Sample size as large as 8 inches
• Programmed to apply desired stress, perform test
  release stress

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Technology for Characterization under Simulated
Application Environment
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Technology for Characterization under Simulated
Application Environment
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Technology for Characterization under Simulated
Application Environment

• Cyclic stress
• Stress cycles are applied on sample sandwiched
  between two porous plates and the sample is
  tested during a pause in the stress cycle

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Technology for Characterization under Simulated
Application Environment
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Technology for Characterization under Simulated
Application Environment

• Features
• Any desired stress between 15 and 3000 psi

• Stress may be applied and released at fixed rates
• Duration of cycle 10 s
• Frequency adjustable by changing the duration of
  application of stress

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Technology for Characterization under Simulated
Application Environment
Features

• Programmed tointerrupt after specified number of
  cycles, wait for a predetermined length of time,
  measure characteristics and then continue
  stressing

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Technology for Characterization under Simulated
Application Environment
Features

• Sample can be tested any required number of times
  within a specified range

• Fully automated

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Technology for Characterization under Simulated
Application Environment
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Technology for Characterization under Simulated
Application Environment
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Technology for Characterization under Simulated
Application Environment

• Aggressive environment

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Technology for Characterization under Simulated
Application Environment

• Directional Porometry

• In this technique, Gas is allowed to displace
  liquid in pores in the specified direction

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Technology for Characterization under Simulated
Application Environment
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Technology for Characterization under Simulated
Application Environment
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Technology for Characterization under Simulated
Application Environment
Material Bubble point, mm Mean flow pore diameter, mm
Fuel cell component
z-direction 14.1 1.92
x-direction 14.6 1.04
y-direction 7.60 0.57
Printer Paper
z-direction 12.4 4.20
x-y plane 1.11 0.09
Transmission fluid filter felt
z-direction 80.4 ?
x-y plane 43.3 ?
Liquid filter
z-direction 34.5 ?
x-y plane 15.3 ?
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Clamp-On Porometry

• Sample chamber clamps on any desired location of
  sample (No need to cut sample damage the
  material)

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Clamp-On Porometry

• Advantages
• Very fast

• No damage to the bulk material
• Test may be performed on any location in the bulk
  material

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Flexibility to Accommodate a Wide Variety of
Sample Shape, Size and Porosity
Shapes

• Sheets

• Hollow Fibers

• Plates

• Pen tips

• Discs

• Cartridges

• Rods

• Diapers

• Tubes

• Odd shapes

• Powders

• Nanofibers

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Flexibility to Accommodate a Wide Variety of
Sample Shape, Size and Porosity

• Size
• Micron size biomedical devices

• 8 inch wafers
• Two feet cartridges
• Entire diaper

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Flexibility to Accommodate a Wide Variety of
Sample Shape, Size and Porosity

• Materials
• Ceramics

• Nonwovens

• Metals

• Composites

• Textiles

• Gels

• Sponges

• Hydrogels

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Ease of Operation

• Fully automated
• Test execution
• Data storage
• Data Reduction
• User friendly interface
• Menu driven windows based software

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Ease of Operation

• Graphical display of real time test status and
  results of test in progress
• Many user specified formats for plotting
  display of results
• Minimal operator involvement

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Advanced Permeametry

• Capability
• A wide variety of gases, liquids strong
  chemicals

• Different directions x, y and z directions, x-y
  plane
• At elevated temperatures, high pressure under
  stress
• Very low or very high permeability

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Diffusion Gas Permeametry
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Diffusion Gas Permeameter
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Diffusion Gas Permeametry

• (dVs/dt) (TsVo/Tps)(dp/dt)
• Vs gas flow in volume of gas at STP
• Vo volume of chamber on the outlet side
• Flow rate lt 0.75x10-4 cm3/s

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High Flow Gas Permeametry

• Uses actual component Diaper, Cartridges, etc.

• Can measure flow rates as high as 105 cm3/s
• Can test large size components

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High Flow Gas Permeametry
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Microflow Liquid Permeametry

• Measures very low liquid permeability in materials

• Ceramic discs
• Membranes
• Potatoes
• Other vegetables fruit
• Uses a microbalance to measure small weights of
  displaced liquid, 10-4 cm3/s

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High Flow Liquid Permeametry at High Temperatures
and High Pressures

• Measures high permeability of application fluids
  at high temperature through actual parts under
  compressive stress

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High Flow Liquid Permeametry at High Temperatures
and High Pressures
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High Flow Liquid Permeametry at High Temperatures
and High Pressures

• Capability
• Temperature 100?C

• Compressive stress on sample 300 psi
• Liquid Oil
• Flow rate 2 L/min

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Envelope Surface Area, Average Particle Size
Average Fiber Diameter Measurement
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Envelope Surface Area, Average Particle Size
Average Fiber Diameter Measurement

• Envelope Surface Area
• Computes surface area from flow rate using Kozeny
  and Carman relation

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Envelope Surface Area, Average Particle Size
Average Fiber Diameter Measurement
Envelope Surface Area

• Fl/pA P3/K(1-P)2S2mZP2p/(1-P)S(2ppr)1/2
  

F gas flow rate in volume at average pressure,
p l thickness of sample per unit
time p pressure drop, (pi-po) p average
pressure, (pipo)/2, where pi is the inlet rb
bulk density of sample pressure and po is
the outlet pressure ra true density of
sample A cross-sectional area of sample m
viscosity of gas P porosity (pore volume/total
volume) 1-(rb/ra) p average pressure,
(pipo)/2, where pi is the r density of the
gas at inlet pressure and po is the
outlet pressure the average pressure, p S
through pore surface area per unit volume Z
a constant. It is shown to of solid in
the sample be (48/13p) K a constant
dependent on the geometry of the pores in the
media. It has a value close to 5 for random
pored media
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Envelope Surface Area, Average Particle Size
Average Fiber Diameter Measurement

• Comparison between BET and ESA Methods

Sample ID ESA surface area (m2/g) BET surface area (m2/g) ESA particle size (microns) BET particle size (microns)
Magnesium stearate A 11.13 12.16 0.43 0.39
Magnesium stearate B 6.97 7.13 0.69 0.67
Glass bubbles A 0.89 0.915 14.82 14.83
Glass bubbles B 1.76 1.91 22.25 20.53
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Envelope Surface Area, Average Particle Size
Average Fiber Diameter Measurement

• Average particle size
• Computes from surface area assuming same size
  spherical shape of particles

• d the average particle size
• S specific surface area of the sample (total
  Surface area/mass)
• r true density of the material

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Envelope Surface Area, Average Particle Size
Average Fiber Diameter Measurement

• Comparison between BET and ESA Methods

Sample ID ESA surface area (m2/g) BET surface area (m2/g) ESA particle size (microns) BET particle size (microns)
Magnesium stearate A 11.13 12.16 0.43 0.39
Magnesium stearate B 6.97 7.13 0.69 0.67
Glass bubbles A 0.89 0.915 14.82 14.83
Glass bubbles B 1.76 1.91 22.25 20.53
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Envelope Surface Area, Average Particle Size
Average Fiber Diameter Measurement

• Average fiber diameter
• Computed from flow rate using Davies equation

• (4?pAR2)/(mFl) 64 c1.5152c3

P ? 0.7-0.99 c packing density (ratio of volume
of fibers to volume of sample) (1-P) ?p
pressure gradient A cross-sectional area of
sample R average fiber radius m viscosity of
gas F gas flow rate average pressure L
thickness of sample
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Envelope Surface Area, Average Particle Size
Average Fiber Diameter Measurement
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Envelope Surface Area, Average Particle Size
Average Fiber Diameter Measurement

• Average fiber diameter can also be computed from
  the envelope surface area. Assuming the fibers to
  have the same radius and the same length

Df 4V/S 4/Sr Df average fiber
diameter V volume of fibers per unit mass S
envelope surface area of fibers per unit mass r
true density of fibers
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Water Vapor Transmission

• Transmission under pressure gradient

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Water Vapor Transmission

• Transmission under pressure gradient

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Water Vapor Transmission

• Transmission under concentration gradient

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Water Vapor Transmission

• Transmission under concentration gradient

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Mercury Intrusion Porosimetry

• Stainless Steel Sample Chamber

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Mercury Intrusion Porosimetry

• Special design to minimize contact with mercury

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Mercury Intrusion Porosimetry

• Separation of high-pressure section from
  low-pressure section

• Sample chamber is evacuated and pressurized
  without transferring the chamber and contacting
  mercury
• Automatic cleaning of the system by evacuation

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Mercury Intrusion Porosimetry

• Automatic refilling of penetrometer by mercury

• Automatic drainage of mercury
• In-situ pretreatment of the sample
• Fully automated operation

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Non-Mercury Intrusion Prosimetry

• Sample Chamber That permits Mercury Intrusion
  Porosimeter to be used as a Non-Mercury Intrusion
  Porosimeter

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Water Intrusion Porosimeter (Aquapore)

• Uses absolutely no mercury

• Water used as intrusion liquid
• Can test hydrophobic materials
• Can detect hydrophobic pores in a mixture

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Water Intrusion Porosimeter (Aquapore)
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Gas Adsorption

• A new technique developed by PMI

• Capable of very fast measurement (lt10 min) of
  single point and multi-point surface areas
• The PMI QBET for fast surface area measurement

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Conclusions

• Recent advances made in the technology of
  measurement and novel methods of measurement of
  properties using porometry, permeametry,
  porosimetry and gas adsorption have been discussed

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Conclusions

• Results have been presented to show the
  improvements in accuracy and repeatability of
  results and ease of operation of the test.

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Conclusions

• Measurement of characteristics under application
  environments involving

• compressive stress
• cyclic compression
• aggressive conditions
• elevated temperatures
• high pressures
• have been illustrated with examples

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Thank You