issues and insights regarding particle size analysis

1

Issues and Insights Regarding

Particle Size Analysis

Moderator

Melissa Gorris

Sales and Marketing Manager

Additive Manufacturing Team Lead

Host

Dave van der Wiel, Ph.D.

Director of Technology Development

2

What we’ll talk about today…

Not a review of all the ways particle size can be measured

One method isn’t necessary better than another

Size range often limits potential techniques

Introduction to the most common measurement techniques

Degree of sample separation during measurement

Emphasis on basis of measurements

Testing standards

Factors that impact all technique

Sampling, agglomeration, dispersion

Particle shape assumptions

Measurement basis & data representation

Measurement calibrations & verification

Measurement comparisons

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NSL Analytical Services

NSL provides independent laboratory testing services to a diverse array of

customers where testing speed, accuracy and consistency are mission

critical to operations.

Our teams of chemists, engineers and metallurgists provide

scientific expertise in materials testing with a focus on metals,

polymers and technical ceramics used in critical end markets

such as aerospace, oil & gas, energy, chemicals and metallurgy.

Chemical Analysis Thermal Analysis Physical Properties

Microscopy &

Metallography

Particle

CharacterizationMechanical Testing

Metallurgical /

Failure AnalysisConsulting

Regulatory

Compliance

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Dynamic Light Scattering

Laser Diffraction

Acoustic Attenuation

Sedimentation/Centrifugation

Flow Field Fractionation

Sieve Analysis

Light Obscuration

Electro-Sensing Zone

Dynamic Image Analysis

Static Optical Imaging

Electron Microscopy

0.01 0.1 1 10 100 1000

microns

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Particle Size Analysis Methods

Counting Methods Separation Methods Ensemble Methods

Particles are analyzed

individually Rely on the segregation

of particles

All particles are

analyzed simultaneouslyImaging Non-Imaging

Basis of Data

Representation

Weighting

Number NumberMass/Density

or VolumeIntensity or Volume

Methods

Image Analysis

Microscopy


Optical Counting (TOT)

Light Obscuration (TOF)

Sieve Analysis

Sedimentation

Fractionation

Laser Diffraction


Air Permeability

Acoustic

Categorized by degree of separation

Method selection should align with how the results will be used

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Laser Diffraction

Acoustic Attenuation

Sedimentation/Centrifugation

Flow Field Fractionation

Sieve Analysis

Light Obscuration


Dynamic Image Analysis

Static Optical Imaging

Electron Microscopy

0.01 0.1 1 10 100 1000

Measurement Techniques

Counting

Separation

Ensemble

microns

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Basis of Measurement vs. Data Representation




of particles

All particles are


Basis of Data

Representation

Weighting

Number NumberMass/Density

or VolumeIntensity or Volume

Basis of

MeasurementArea Volume or Intensity Area, Density Intensity or Volume

Methods

Image Analysis

Microscopy


Optical Counting (TOT)

Light Obscuration (TOF)

Sieve Analysis

Sedimentation

Fractionation

Laser Diffraction


Air Permeability

Acoustic

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Basis of Measurement vs. Data Representation

2D Imaging Sieve Analysis

AREA 3AREA 2

AREA 1

SOFTWARE

COUNTING

MESH

OPENING

AREA

MASS OF

PASSING

FRACTION

MASS OF

RETAINED

FRACTION

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Testing Standards




of particles

All particles are


Image Analysis Sensing Zone

Sieve Analysis Light Scattering

ISO 3310

ASTM D4513

ASTM D5861

ISO 13320

ISO 22412

ASTM C1070

ASTM D4464

UOP856

ISO 13322

ASTM D8090

ISO 13319

ASTM C690

Sedimentation Air Permeability Acoustic

ISO 13317

ISO 13318

ASTM B761

ASTM C958

ASTM C1182

ASTM C1730

ASTM E2980

ASTM C721

ISO 20998

Excluding standards specific to metallic powders

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Testing Standards - Metallic Powders




of particles

All particles are


Image Analysis Zone Sensing

Sieve Analysis Light Scattering

ISO 4497

ASTM B214

MPIF 05

ISO 13320 ASTM B822

ISO 13322 ISO 13319 Sedimentation Air Permeability Acoustic

ISO 13317 ASTM B761ASTM B330

MPIF 32

Standards encompassing metallic powders

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Additional Particle Information




of particles

All particles are


Method Image Analysis Electro-Sensing Zone Sieve Analysis Laser Diffraction

Add’n Data Morphology Concentration Homogeneity Isometry

Method Microscopy

Sedimentation

Fractionation


Air Permeability

Acoustic

Add’n DataElemental

distributionDensity Diffusion Coefficients

Several techniques may measure more than just particle size

Most techniques can model other information like shape factors

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Contributors to Particle Size Measurement Results

Representative SamplingParent sample

Test portions (method specific)

Particle Agglomeration De-agglomeration must not breakup primary particles

Sample DispersionWet or dry

Uniformity

Method Suitability (incl. assumptions)

Test sample size

Particle shape – sphericity

Distribution, uniformity

Method ParametersIndex of refraction

Shape & distribution models

Data Analysis & Representation Correlation Values & Graphs

Results Analysis & Comparisons Direct results vs. converted data

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Sampling, Agglomeration

& Dispersion

14

Representative Sampling

Parent Samples• ASTM B215 – Sampling metal powders

• ISO 14488 – Sampling for the determination of particulate properties

• Microrifflers require about >10 cm3 to function properly

• >12 g for aluminum powder or >45 g for Inconel powder

Test Samples – example quantities for metal powders:• Sieve Analysis: <100 g (ASTM B214)

• Laser Diffraction: <5 g (2% to 10% obscuration)

• Microscopy: <0.1 g

• Representative analysis vs. sample size

15

Particle Agglomeration

Agglomerates vs. primary particles• Goal is to reduce apparent particle size without affecting primary particle size

or shape

• A shift from a monomodal to multi-modal size distribution may indicates

fracturing of primary particles

De-agglomeration• Stirring and sonication

• Minimum sonication time and power (ASTM B821)

• Dispersion (next slide)

• Re-testing to check for changes in size distribution after repeated analyses

• ISO/TR 13097 – Dispersion stability

• Common issue when sieving (shaking, use of brushes, etc.) or air-dispersing

(impact forces)

Chakrabarty et.al., Atmos. Chem. Phys. 16, 3033 (2016)

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Sample Dispersion

ASTM B821 – Liquid dispersion of metal powders and related compounds for particle size analysis• To be used for X-Ray Sedimentation (ASTM B761) and Laser Diffraction (ASTM B822)

• Carrier liquid, surfactant, ultrasonication

• Provides specific recommendations for steel, nickel, copper and several other materials

• Section 7.1.4 requires sample inspection for dispersion

ISO 13320 – Particle size analysis – laser diffraction• Wet procedures - Recirculation, small volume cells, etc.

• Annex B – Advice on dispersion liquids

• Liquid medium, surfactant, dispersant

• Annex C.2 – Liquid dispersion recommendations

• Dry procedures – Aerosolizing

• Annex C.1 – Gas dispersion recommendations

• Section 5.4.1 requires sample inspection for dispersion

ISO 14887 – Dispersing procedures for powders in liquids

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Particle Shape Effects

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Uniformity of dimensions

Isometric

dmaxdequiv x = d x = r

IsotropicAnisotropic

Similarity in dimensions

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Influence of Particle Shape

Isotropic shapes• Mathematical models may be able to do a good job of

correlating raw data to size data

Anisotropic shapes• Non-imaging techniques rely on various equivalency

models• Equivalent diffraction patterns

• Equivalent spherical area, volume, perimeter

• Equivalent dynamics

Such models may or may not provide valid correlations• Must be confirmed for a particle type, morphology

• A given model is not necessarily universal

oblate spheroid

prolate spheroid

sphere

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Anisotropic Particles

da = 30.8 m

dv = 30.2 mda = 31.4 m

dv = 30.4 m

da = 31.9 m

dv = 30.5 m

11 m

30 m

Isometric (area and volume equivalencies) measurements may be misleading

21

Anisotropic Particles

da = 30.8 m

dv = 30.2 mda = 31.4 m

dv = 30.4 m

da = 31.9 m

dv = 30.5 m

11 m

da = 32.2 m

dv = 30.0 m26 × 40 m

da = 29.8 m

dv = 27.7 m24 × 37 m

30 m

Area and volume equivalencies may provide different size results

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Measurement Basis &

Representation

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Distribution Basis

Number

Area

Volume

0%

10%

20%

30%

40%

50%

60%

20 40 60

0%

10%

20%

30%

40%

50%

60%

20 40 60

0%

10%

20%

30%

40%

50%

60%

70%

20 40 60

mean 40 m

median 40 m

mode 40 m

mean 49 m

median 50 m

mode 60 m

mean 52 m

median 60 m

mode 60 m

20 m

40 m

60 m

m

m

m

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Multimodal Distributions

70 m

40 m

10 m

100 m

25

Multimodal Distributions

Particle Diameter (m)

Laser

Diffraction

Image

Analysis

0%

5%

10%

15%

20%

25%

30%

35%

0 20 40 60 80 100 120

NumberVolume

Area Number Area Volume

mean 50 m 69 m 74 m

median (d50) 45 m 70 m 80 m

mode 40 m 70 m 70 m

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Converting Between Weighted Distributions

Applying different weightings to raw data Converting a weighted distribution

27

Size Sensitivity in Weightings

Measurement or

Reporting BasisNumber Area Volume Intensity

Size sensitivity r0 r2 r3 r2 to r6

Counting

Techniques

Imaging Methods

Sieve Analysis

Laser Diffraction

Dynamic Light

Scattering

Acoustic

Attenuation

28


HORIBA Guidebook to

Particle Size Analysis

horiba.com

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General advice is to don’t do it!• The results of conversions are often misleading or erroneous

Issues• Assumptions must be made to do conversions

• Particularly problematic for intensity-weighted distributions

• The resolution (signal-to-noise) of a given technique may not scale

well when converting to another basis

Do direct comparisons instead• Always note differences in basis

• Often such comparisons are insightful

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Data Representation - Bins

Sieve

Analysis

75 m 106 m 150 m

% Number

19% <75 m

45% 75-106 m

23% 106-150 m

13% >150 m

% Mass or Vol.

2% <75 m

18% 75-106 m

32% 106-150 m

48% >150 m

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Data Representation - Bins

% Number

19% <75 m 17% 45-75 m

45% 75-106 m 48% 75-106 m

23% 106-150 m 32% 106-150 m

13% >150 m 48% 150-180 m

% Mass or Volume

2% <75 m 2% 45-75 m

18% 75-106 m 22% 75-106 m

32% 106-150 m 39% 106-150 m

48% >150 m 38% 150-180 m

75 m 106 m 150 m 180 m45 m

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0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0%

5%

10%

15%

20%

25%

30%

0 20 40 60 80 100 120

Data Representation - Distributions

Graphical distributions• Size distribution and/or cumulative distribution

diameter (m)

Size

Fraction Cumulative

Fraction

%vol

33

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0%

5%

10%

15%

20%

25%

30%

0 20 40 60 80 100 120



diameter (m)

Size

Fraction25% of particles by volume are ~40 m

or

~40 m particles make up about 25%vol)

%vol

34

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0%

5%

10%

15%

20%

25%

30%

0 20 40 60 80 100 120



diameter (m)

d50

Cumulative

Fraction

d10 d90

%vol

of particlesdiameter

10% <28 m

50% <47 m

50% >47 m

90% <76 m

%vol

35

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0%

5%

10%

15%

20%

25%

30%

0 20 40 60 80 100 120


diameter (m)

MeanMode

d10 d90

Median

d50


Single values• Generally a bad idea

• Median (d50)

• Arithmetic vs. geometric mean

• Variance (2) or Span (d90-d10)/d50

Multiple values• Most common: d10, d50, d90

• Mean, median, mode

%vol

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Calibration & Verification

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Particle Size Reference Materials

Many suppliers

provide NIST

traceable particle

size reference

materials for

specific materials,

morphologies

and sizes

Weighting: Number Volume

d10 12.0 ± 1.9 nm 6.9 ± 2.7 nm

d50 18.5 ± 2.5 nm 12.6 ± 2.1 nm

d90 34.6 ± 4.8 nm 19.4 ± 2.2 nm

Exemplar RMs Size Range (m) Material

BAM-N001 0.012 to 0.035 Nano Ag

NIST RM 8988 0.1 to 0.5 TiO2

NIST SRM 1690 1 Polystyrene spheres

NIST SRM 1978 0.2 to 10 ZrO2 powder

NIST SRM 1021 2 to 12 Glass beads

BCR-067 2.4 to 32 Quartz

NIST SRM 1984 9 to 30 WC/Co needles

NIST SRM 1961 30 Polystyrene

NIST SRM 1985 18 to 55 WC/Co spheroids

BCR-069 14 to 90 Quartz particles

NIST SRM 1003c 20 to 50 Glass beads

NIST SRM 1982 25 to 80 Y-ZrO2 spheroids

NIST SRM 1004b 40 to 150 Glass beads

NIST SRM 1017b 100 to 400 Glass beads

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Proficiency Test Programs

ASTM AMPM - metal powders• Sieve Analysis ASTM B214 (equivalency to ISO 4497)

• Laser Diffraction ASTM B822 (equivalency to ISO 13320)

• Static Image Analysis ISO 13322-1

• Dynamic Image Analysis ISO 13322-2

BAM (Germany) - ceramics• Laser Diffraction ISO 13320

Swiss Institute for Interlaboratory Proficiency - ceramics• Laser Diffraction ISO 13320

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BAM Interlaboratory Comparison

https://rrr.bam.de/RRR/Navigation/EN/Proficiency-Testing/PARTICLE-SIZE/particle-size.html

Laboratories

Dia

mete

r

40

Comparative Measurements

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Comparing Techniques - Glass Spheres

Comparison Using 50-75 m Glass Spheres• Eliminates effects due to non-spherical shape factors/models

The Particle Size Paradox, Micromeretics Application Note 177

d10 d50 d90 dmode

Sedimentation 41.0 61.6 89.1 63.1 Diameter directly from Stokes equation

Dynamic Imaging 45.1 61.7 75.9 67.1 Spheres provide well-defined shape factor

Laser Diffraction 45.0 66.9 85.0 71.1 Spherical, isotropic particles – no need for equivalency

ESZ 49.5 66.5 82.4 72.4

Variation 7% 4% 6% 5%

42

Comparing Techniques - Coffee!

d10 d50 d90

Sieve Analysis* 128 418 714

Dynamic Imaging 168 559 875

Laser Diffraction 222 586 1200

Variation 22% 14% 22%

Retsch Technology Gmbh

dimension (mm)

• Sieve analysis corresponds with narrowest particle

dimension (width)

• As in previous example, laser provide larger sizes

than dynamic imaging

mass

area

volume

?

%vol

*requires interpolation between bins

43

See also…

Considerations in Particle Sizing

• Lubrizol Technical Brief – https://lubrizolcdmo.com/technical-briefs/

Particle Size Characterization

• NIST Special Publication 960-1

ISO 9276 Representation of Results of Particle size Analysis• Part 1 Graphical representation

• Part 2 Calculation of average particle sizes/diameter and moments

• Part 3 Adjustment of an experimental curve to a reference model

• Part 4 Characterization of a classification process

• Part 5 Particle size analysis using logarithmic probability distributions

• Part 6 Descriptive and quantitative representation of particle shape and morphology

Particle Size Distribution Measurement from Millimeters to Nanometers and from Rods to Platelets

• P. Bowen, Journal of Dispersion Science & Technology 23(5), 631-662 (2002)

https://doi.org/10.1081/DIS-120015368

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Take Aways

It’s important to know the basis of measurement vs basis of reported

distributions for techniques under consideration

– One doesn’t necessarily need to fully understand the fundamentals of each

Suitability of a measurement technique depends on:

– Nature of the sample – homogeneity, shape

– What type of size information is desired

– How the size data will be used

Converting measurement distributions from one basis to another is a

minefield best avoided

– Comparing measurements with different basis may actually be informative

Any measurement must be carefully calibrated, verified and re-verified

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Let’s Talk Tech!

Dave van der Wiel

Director of Technology Development

[email protected]

216.428.5215

Optical Microscopy

Hosted By

Rebecca Stawovy

Dave Kovarik

NSL Analytical Services

Join Us For Our Next Tech Talk!

December 10, 2020 at 2pm EDT

issues and insights regarding particle size analysis

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