pmi europe work shop advances in characterization techniques dr. krishna gupta technical director...

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Advances In Characterization Techniques

Advances In Characterization Techniques

Dr. Krishna Gupta

Technical Director

Porous Materials, Inc., USA


TopicsTopics

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

Flow Porometry


TopicsTopics

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

Permeametry


TopicsTopics

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

Mercury Intrusion Porosimetry


TopicsTopics

Conclusions

Gas Adsorption


Flow Porometry (Capillary Flow Porometry)

Flow Porometry (Capillary Flow Porometry)

Design modified to minimized errors Appropriate corrections incorporated

Accuracy and Reproducibility Most important sources of random &

systematic errors identified


Pore diameter, m Sample SEM Micrograph SEM PMI Porometer

Etched stainless steel disc

81.7 + 5.2 86.7 + 4.1

Flow Porometry(Capillary Flow Porometry)


Accuracy

Polycarbonatemembrane

4.5 + 0.5 4.6 + 0.1




Same operator Same machine Same wetting liquid Same filter

Repeatability Bubble point repeated 32 times




Filter Wetting Liquid

Porewick Silwick

Sintered Stainless Steel 1.8% 1.2%

Battery Separator 0.2% 1.5%

Paper 1.7% 1.1%




Errors due to the use of different machines

Machine Bubble point pore diameter, Mean Value, m

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%




Operator errors

Machine Average of mean, m

Difference between mean values by operators

m 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%


Technology for Characterization under Simulated Application Environment


Compressive Stress Arrangement for testing sample

under compressive stress

Arrangement for testing sample under compressive stress




Sample size as large as 8 inches Programmed to apply desired stress,

perform test & release stress

Compressive Stress

Features: Any compressive stress up to 1000

psi (700 kPa)




Effect of compressive stress

on bubble point pore diameter




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




Sample chamber for cyclic compression porometer




Stress may be applied and released at fixed rates

Duration of cycle 10 s Frequency adjustable by changing the

duration of application of stress

Features: Any desired stress between 15 and

3000 psi




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

Features:




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

Features:

Fully automated




Change of bubble point pore diameter

with number of stress cycles

0

2

4

6

8

10

12

14

0 200 400 600 800 1000 1200

Number of compression-decompression cycles

Bu

bb

le p

oin

t p

ore

dia

met

er,

mic

ron

s

0

2

4

6

8

10

12

14

0 200 400 600 800 1000 1200


Bu

bb

le p

oin

t p

ore

dia

met

er,

mic

ron

s




Effects of Cyclic compression on

permeability

0

0.2

0.4

0.6

0.8

1

1.2

0 200 400 600 800 1000 1200


Per

mea

bili

ty, D

arcy

0

0.2

0.4

0.6

0.8

1

1.2

0 200 400 600 800 1000 1200


Per

mea

bili

ty, D

arcy




Aggressive environment

Pore size of separator

determined using KOH

solution




Directional Porometry In this technique, Gas is allowed to

displace liquid in pores in the specified direction




Sample chamber for determination of

in-plane (x-y plane) pore structure




Sample chamber for determination of pore structure in a specific direction such as x or y




Material Bubble point, m Mean flow pore diameter, m

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 ―


Clamp-On PorometryClamp-On Porometry

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

Typical chambers for

clamp-on porometer


Clamp-On PorometryClamp-On Porometry

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

location in the bulk material

Advantages: Very fast


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


Plates

Shapes:

Sheets Hollow Fibers

Pen tips Discs Cartridges Rods Diapers Tubes Odd shapes Powders Nanofibers




8 inch wafers Two feet cartridges Entire diaper

Size: Micron size biomedical devices




Materials: Ceramics Nonwovens Metals Composites Textiles Gels Sponges Hydrogels


Ease of OperationEase of Operation

Fully automated Test execution Data storage Data Reduction

User friendly interface Menu driven windows based software


Ease of OperationEase 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


Advanced PermeametryAdvanced Permeametry

Different directions; x, y and z directions, x-y plane

At elevated temperatures, high pressure & under stress

Very low or very high permeability

Capability: A wide variety of gases, liquids &

strong chemicals


Diffusion Gas PermeametryDiffusion Gas Permeametry

Principle of diffusion permeameter


Diffusion Gas Permeameter Diffusion Gas Permeameter

The PMI Diffusion Permeameter


Diffusion Gas PermeametryDiffusion 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 < 0.75x10-4 cm3/s

Change of outlet gas pressure with time for two samples measured in the

PMI Diffusion Permeameter.


High Flow Gas PermeametryHigh Flow Gas Permeametry

Can measure flow rates as high as 105 cm3/s

Can test large size components

Uses actual component; Diaper, Cartridges, etc.


High Flow Gas PermeametryHigh Flow Gas Permeametry

PMI High Flow Gas Permeameter


Microflow Liquid PermeametryMicroflow Liquid Permeametry

Ceramic discs Membranes Potatoes Other vegetables & fruit

Uses a microbalance to measure small weights of displaced liquid, 10-4 cm3/s

Measures very low liquid permeability in materials


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




The PMI high pressure, high temperature and high flow

liquid permeameter




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

Capability: Temperature 100C


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


The PMI Envelope Surface Area, Average

Fiber Diameter and Average Particle Size

Analyzer




Envelope Surface Area Computes surface area from flow rate

using Kozeny and Carman relation




Envelope Surface Area [Fl/pA] ={P3/[K(1-P)2S2]}+[ZP2]/[(1-

P)S(2p)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, [(pi+po)/2], where pi is the inlet b = bulk density of sample

pressure and po is the outlet pressure a = true density of sample

A = cross-sectional area of sample = viscosity of gas

P = porosity (pore volume/total volume) = [1-(rb/ra)]

p = average pressure, [(pi+po)/2], where pi is the = 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 (48/13K = a constant dependent on the geometry of the pores in the media. It has a value close to 5 for random pored media




Comparison between BET and ESA Methods

Sample ID ESA surface area (m^2/g)

BET surface area (m^2/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




d = the average particle size

S = specific surface area of the sample (total Surface area/mass)

= true density of the material

Average particle size Computes from surface area

assuming same size & spherical shape of particles

d =6S




Comparison between BET and ESA Methods

Sample ID ESA surface area (m^2/g)

BET surface area (m^2/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




(4pAR2)/(Fl) = 64 c1.5[1+52c3]

Average fiber diameter Computed from flow rate using Davies

equation

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

= viscosity of gas

F = gas flow rate average pressure

L = thickness of sample




Measured fiber diameters in

microns plotted against the actual

fiber diameters0

5

10

15

20

25

0 5 10 15 20 25

Actual Fiber Diameter

Cal

cula

ted

Fib

er D

iam

ter

0

5

10

15

20

25

0 5 10 15 20 25

Actual Fiber Diameter

Cal

cula

ted

Fib

er D

iam

ter




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/SDf = average fiber diameter

V = volume of fibers per unit mass

S = envelope surface area of fibers per unit mass

= true density of fibers


Water Vapor TransmissionWater Vapor Transmission

Transmission under pressure gradient

Principle of Water vapor transmission analyzer


Water Vapor TransmissionWater Vapor Transmission

Transmission under pressure gradient

Change of pressure on the outlet side of two samples of the naphion membrane

in the PMI Water Vapor Transmission Analyzer


Water Vapor Transmission Water Vapor Transmission

Transmission under concentration gradient

Line diagram showing the operating principle

of PMI Advanced Water Vapor Transmission

Analyzer


Water Vapor Transmission Water Vapor Transmission

Transmission under concentration gradient

Water vapor transmission rate

through several samples

0.00E+00

2.00E-05

4.00E-05

6.00E-05

8.00E-05

1.00E-04

1.20E-04

1.40E-04

1.60E-04

0 0.2 0.4 0.6 0.8Average humidity, RH

Wat

er v

apo

r fl

ux

(kg

/m^

2-s)

Diaper

Plastic sheet

Carbon filter

0.00E+00

2.00E-05

4.00E-05

6.00E-05

8.00E-05

1.00E-04

1.20E-04

1.40E-04

1.60E-04

0 0.2 0.4 0.6 0.8Average humidity, RH

Wat

er v

apo

r fl

ux

(kg

/m^

2-s)

Diaper

Plastic sheet

Carbon filter


Mercury Intrusion PorosimetryMercury Intrusion Porosimetry

Stainless Steel Sample Chamber

Stainless Steel Sample Chamber of The PMI

Mercury Intrusion Porosimeter



Special design to minimize contact with mercury

The PMI Mercury Intrusion Porosimeter



Sample chamber is evacuated and pressurized without transferring the chamber and contacting mercury

Automatic cleaning of the system by evacuation

Separation of high-pressure section from low-pressure section



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

Automatic refilling of penetrometer by mercury


Non-Mercury Intrusion ProsimetryNon-Mercury Intrusion Prosimetry

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

Sample Chamber for use to perform non-mercury intrusion tests in the

PMI Mercury Intrusion Porosimeter


Water Intrusion Porosimeter (Aquapore)


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

mixture

Uses absolutely no mercury




The PMI Aquapore


Gas AdsorptionGas Adsorption

Capable of very fast measurement (<10 min) of single point and multi-point surface areas

The PMI QBET for fast surface area measurement

A new technique developed by PMI


ConclusionsConclusions

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



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



compressive stress cyclic compression aggressive conditions elevated temperatures high pressures

have been illustrated with examples

Measurement of characteristics under application environments involving:


Thank YouThank You

pmi europe work shop advances in characterization techniques dr. krishna gupta technical director...

Documents

pmi europe work shop

operator f

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