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Dr. Jeff Bodycomb of HORIBA Particle discusses how image analysis technologies can be used to measure particle shape parameters. This presentation is archived with the original webinar video in the Download Center at www.horiba.com/us/particle.
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© 2010 HORIBA, Ltd. All rights reserved.
Image Analysis: Evaluating Particle Shape
Jeffrey Bodycomb, Ph.D.
HORIBA Scientific
www.horiba.com/us/particle
© 2010 HORIBA, Ltd. All rights reserved.
Why Image Analysis? Verify/Supplement diffraction results (orthogonal technique) Replace sieves
Need shape information, for example due to importance of powder flow
These may have the same size (cross section), but behave very differently.These may have the same size (cross section), but behave very differently.
© 2010 HORIBA, Ltd. All rights reserved.
Why Image Analysis? Crystalline, acicular powders needs more than
“equivalent diameter”
We want to characterize a needle by the length (or better, length and width).We want to characterize a needle by the length (or better, length and width).
© 2010 HORIBA, Ltd. All rights reserved.
Why Image Analysis Pictures: contaminants, identification, degree of
agglomeration Screen excipients, full morphology Root cause of error (tablet batches), combined
w/other techniques Replace manual microscopy
© 2010 HORIBA, Ltd. All rights reserved.
Why Shape Information?
Evaluating packingEvaluate flow of particlesEvaluate flow around particlesRetroreflection (optical properties)Properties of particles in aggregate
(bulk)
© 2010 HORIBA, Ltd. All rights reserved.
Effect of Shape on Flow Yes, I assumed density doesn’t matter. Roundness is a measure based on particle
perimeter.
cc
© 2010 HORIBA, Ltd. All rights reserved.
Major Steps in Image Analysis
Image Acquisitionand enhancement
Object/Phase
detection
Measurements
© 2010 HORIBA, Ltd. All rights reserved.
Dynamic:particles flow past camera
Static:particles fixed on slide,stage moves slide
1 – 3000 microns0.5 – 1000 microns2000 microns w/1.25 objective
Two Approaches
© 2010 HORIBA, Ltd. All rights reserved.
Size Parameters -> Shape Parameters
Shape parameters are often calculated using size measures
© 2010 HORIBA, Ltd. All rights reserved.
Size Parameters
FeretMax (length)Perpendicular to Max (width)Min (width)Perpendicular to Min (main length)
AreaCircular DiameterSpherical Diameter
PerimeterConvex Perimeter
© 2010 HORIBA, Ltd. All rights reserved.
Ferets Size as measured with a caliper Result depends on orientation of caliper
MinMaxPerpendicular to MinPerpendicular to Max
to Max
Mi
n
to Min Max
© 2010 HORIBA, Ltd. All rights reserved.
Area (Circular Diameter)
Count pixels to find area of particle
Convert to circle with equivalent area
Diameter
same AREAsame AREA
Area
2
© 2010 HORIBA, Ltd. All rights reserved.
Perimeter, Convex Perimeter
Perimeter follows exact contours of object
Convex perimeter is like a rubber band.
© 2010 HORIBA, Ltd. All rights reserved.
Shape Descriptors
aspect ratioroughnessroundnesssphericity
© 2010 HORIBA, Ltd. All rights reserved.
Shape Using a Chart
Krumbein, Journal of Sedimentary Petrology, vol 11, no 2, pp 64-72, plate 1, August, 1941Krumbein, Journal of Sedimentary Petrology, vol 11, no 2, pp 64-72, plate 1, August, 1941
© 2010 HORIBA, Ltd. All rights reserved.
A different chart
Compare particles to a chart like the one below.
Round cornersRound corners
Overall shape like a sphere
Overall shape like a sphere
© 2010 HORIBA, Ltd. All rights reserved.
Aspect Ratio
Length of longest Feret over Length of shortest Feret
Longest Feret over Feret perpendicular to longest Feret
Feret perpendicular to shortest Feret over shortest Feret
Or their reciprocal!
Nice measure of deviation from roundness. Is not profoundly affected by bumps on particle surface.
Measures “large scale shape”
© 2010 HORIBA, Ltd. All rights reserved.
Aspect ratios of square
1
1
Fe Max is diagonal: 1.414Fe Max is diagonal: 1.414
Perp to Fe Max is diagonal: 1.414Perp to Fe Max is diagonal: 1.414
Fe Min is 1Fe Min is 1
Fe Max / Fe Min = 1.414/1 = 1.414Fe Max / Fe Min = 1.414/1 = 1.414
Fe Max / Perp to Fe Max = 1.414/1.414 = 1Fe Max / Perp to Fe Max = 1.414/1.414 = 1
Perp to Fe Min / Fe Min = 1/1 = 1Perp to Fe Min / Fe Min = 1/1 = 1
© 2010 HORIBA, Ltd. All rights reserved.
Salt Shape in Aluminum Foam
NaCl is used to manufacture aluminum foams as a filler. The NaCl is subsequently dissolved away to leave a porous structure.
The shape and size of the NaCl affects the foam structure and the final properties of the foam.
C. Gaillard, J. F. Despois and A. MortensenProcessing of NaCl powders of controlled size and shape for the microstructural tailoring of aluminium foams Materials Science and Engineering AVolume 374, Issues 1-2, 15 June 2004, Pages 250-262
C. Gaillard, J. F. Despois and A. MortensenProcessing of NaCl powders of controlled size and shape for the microstructural tailoring of aluminium foams Materials Science and Engineering AVolume 374, Issues 1-2, 15 June 2004, Pages 250-262
Image courtesy of Wikimedia Commons User StehfunImage courtesy of Wikimedia Commons User Stehfun
© 2010 HORIBA, Ltd. All rights reserved.
NaCl Shape
HORIBA Application Note AN189: size and Shape Analysis of Salt using Dynamic Image AnalysisHORIBA Application Note AN189: size and Shape Analysis of Salt using Dynamic Image Analysis
© 2010 HORIBA, Ltd. All rights reserved.
Glass beads for reflective pavement marking
Beads must be round to reflect light back to driver. Check aspect ratio of each particle, fail if too many
particle have a value that is too low.
HORIBA Application Note AN140: Particle size and Shape analysis of glass beads for pavement markingsHORIBA Application Note AN140: Particle size and Shape analysis of glass beads for pavement markings
Aspect ratio 0.5051Aspect ratio 0.5051
Aspect ratio 0.9660Aspect ratio 0.9660
© 2010 HORIBA, Ltd. All rights reserved.
Acetaminophen (API)
© 2010 HORIBA, Ltd. All rights reserved.
Roughness
Jaggedness of edges
Short scale. Roughness is sensitive to bumps on surface
As surface has more concavities, the convex perimeter increases and therefore roughness decreases
Perimeter
meterConvexPeri
© 2010 HORIBA, Ltd. All rights reserved.
Roundness
As particle becomes circular, value approaches one.
2)(
)(4
FeMaxLength
Area
Length
© 2010 HORIBA, Ltd. All rights reserved.
Roundness of metal particles Metal particles are used for powder metallurgy Round particles flow better (e.g., during injection
molding) and provide stronger partsLow quality nickel alloy powder. Note the small fraction of very round particlesLow quality nickel alloy powder. Note the small fraction of very round particles
HORIBA Application Note AN164: Particle Size and Shape Analysis of Metal PowdersHORIBA Application Note AN164: Particle Size and Shape Analysis of Metal Powders
© 2010 HORIBA, Ltd. All rights reserved.
Pharmaceutical Globules
Spheres from sugar are often used. Shape matters for future process steps
incorporation or coating of API’sFlow through dispensers
HORIBA Application Note AN140: Particle size and Shape analysis of glass beads for pavement markingsHORIBA Application Note AN140: Particle size and Shape analysis of glass beads for pavement markings
© 2010 HORIBA, Ltd. All rights reserved.
Acetaminophen (API)
© 2010 HORIBA, Ltd. All rights reserved.
Sphericity
As particle becomes spherical, value approaches one.
More sensitive to small scale bumps that increase perimeter than roundness.
2)(
)(4
Perimeter
Area
© 2010 HORIBA, Ltd. All rights reserved.
Circularity, Sphericity, Perimeter, Diameter
area of the particle
perimeter of the particle
circle with same area as particle
diameter of circle of same area
Circularity = perimeter of circle / perimeter of particle
Sphericity = Circularity2 =
Agreen ~ 77 pixel, diameterred = 10 pixel, perimetergreen ~ 38,5 pixel, circularity ~ 31 / 38,5 = 0.81, sphericity = 4 * π * 77 / (38.5)2 = 0.812 = 0.65
2
4
P
A
Aparticle is inside of
particle perimeter
© 2010 HORIBA, Ltd. All rights reserved.
Proppants
Hold open cracks in oils wells to allow oil to flow to well (Hydraulic Fracturing).
Sand is one example of a proppant High roundness and sphericity leads to better
permeability. ISO/DIS 13503-2 recommended sphericity
and roundness of 0.6 or greater, 0.7 for high strength materials.
Note that these definitions of sphericity and roundness are different from, but related to the one’s used in this talk.
© 2010 HORIBA, Ltd. All rights reserved.
Distributions
Just like size, many particle samples have a distribution of shapes.
Sometimes a distribution of shapes is desirable. For example, according to the USGA, sand that is highly uniform in size and shape tends to be less stable. Therefore, sand with a variety of grain sizes and shapes is better for use in sand traps.
http://www.usga.org/course_care/articles/construction/bunkers/How-to-Select-the-Best-Sand-for-Your-Bunkers/http://www.usga.org/course_care/articles/construction/bunkers/How-to-Select-the-Best-Sand-for-Your-Bunkers/
© 2010 HORIBA, Ltd. All rights reserved.
Size- & Shape ResultsMeasurement Results
shape
• shape + shape distribution
- shape by size
- amount by shape
shape
size
amount
• size + size distribution
- amount by size
© 2010 HORIBA, Ltd. All rights reserved.
SortingRoughness, “too rough” is redRoughness, “too rough” is red
Roundness, not round enough is greenRoundness, not round enough is green
© 2010 HORIBA, Ltd. All rights reserved.
Particle Shape: Amounts in a Mixture
Measurement Results
b/l0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.90
10
20
30
40
50
60
70
80
90
Q3 [%]AK_22,15g_0,3%_BZ_LB_n Ü_xc_min_001.rdfIA_22,15g_0,3%_BZ_LB_n Ü_mit Aerosil_xc_min_001.rdfIA + AK_je 22,15g_0,3%_BZ_LB_n Ü_als Mischung_xc_min_001.rdf
Graph of measurement results:C:\...h-3jhwpyax\Camdat\Messungen 030603\AK_22,15g_0,3%_BZ_LB_n Ü_xc_min_001.rdfTask file: RT 502 IA_BZ_LB_0,7%_R40-Trocknung_.afg
B
A
80
90
Q3 [%]
A B A + B
B A
© 2010 HORIBA, Ltd. All rights reserved.
Particle Shape:
Amounts in a Mixture
32.8%
67.2%
xFe max
xc min
Measurement Results
Q3 (round particles) =
© 2010 HORIBA, Ltd. All rights reserved.
The HORIBA PSA300
Turnkey SystemMore time getting results and less time
engineering Automated
FasterLess operator laborLess operator bias
Powerful Software FeaturesImage EnhancementParticle separation
Separate Disperser OptionMore flexible sample preparation
© 2010 HORIBA, Ltd. All rights reserved.
Static or Dynamic Image Analysis?
DynamicBroad size distributions (since it is easier to obtain
data from a lot of particles)Samples that flow easily (since they must be
dropped in front of camera)Samples tumble so sometimes you see more
orientationsPowders, pellets, granules
StaticSamples that are more difficult to disperse (there
are more methods for dispersing the samples)Samples that are more delicatePastes, sticky particles, suspensions
© 2010 HORIBA, Ltd. All rights reserved.
Conclusions
Image Analysis is good for SizeShapeSupplementing other techniques
Shape Analysis is the next step beyond sizeChoice of parameters is very application
dependent.
© 2010 HORIBA, Ltd. All rights reserved.
Questions?
www.horiba.com/us/particle
Jeffrey Bodycomb, [email protected]
866-562-4698