Recent Advances in Particle Analysis

Paul Kester

Micromeritics Instrument Corporation

Areas of Interest for Ceramics

DensitySkeletal

• New uses of old technique

Particle SizeComparison of TechniquesNew technique for nanoparticles

Surface AreaHigh Pressure Studies

Measure Skeletal Density at Various Stages

Molded Debound Sintered

Fully dense• Check for theoretical Density

Indicator for occluded pores• Excessive sintering

Indicator for removal of binder

Future ASTM Method for Density

Committee B09 on Powdered Metals and Powdered Metal ProductsSub-Committee B09.05 Structural Parts

Work to start in 6-8 months Applies to parts after sintering Standard Method for Gas

Pycnometry

Density – Equilibration Rate

Measure Rate of Equilibration for a material to determine proper analysis parameters

Study Rate of Equilibration for various gases on a materialMay give information about tortuosity of

pores

Particle Size Techniques

Laser Light Scattering

X-ray Sedimentation

Electrical Sensing Zone

Particle Size by Surface Area

Laser Light Scattering

Widely used fast technique that can be applied to various particulate systems

Easily automated in a variety of commercially available instruments

Requires knowledge of Refractive Index of the material

Data presented as Equivalent Spherical Diameter

Laser Light Scattering

Historically laser scattering was performed at small angles only, typically up to 14 °, called Fraunhofer diffraction Forward light scattering Low-angle laser light scattering (LALLS)

Gave results down to 1 µm Now broadened to include wider angles

with Mie Theory optical modeling Expanded range down to 0.1 µm

Types of Scattered Light

Diffraction Reflection Refraction Absorption

Laser Scattering

Transmitted ray

No interaction- undeviated ray

Diffracted ray

Refracted ray

Reflected ray

Transmitted after

internal reflectionTransmitted ray

Laser Light Scattering Groups of particles scatter light essentially equal to the

sum of light scattered by the individual particles. Optical models for selected particle sizes, and

mathematical deconvolution, allow computation of the particle size distribution.

It is difficult to differentiate between single particles and agglomerates or aggregates.

X-ray Sedimentation

Based Upon a Classical Particle Sizing Method - Stokes’ Law.

Same Sizing Principle as Andreasen Pipette and Long-Arm Centrifuge.

Direct Mass Concentration Detection. X-Ray Attenuation is Proportional to Mass in

Beam. Material Density must be Known Widely used in the Ceramic Industry

X-Ray Sedimentation

Stoke’s Law for Sedimentation, 1891.

Mature, well understood and widely practiced technique.

Now fully automated

X-ray Sedimentation

Stoke’s equation

D = particle diameter

η = liquid viscosity

v = sedimentation velocity

ρ = particle density

ρo = liquid density

g = acceleration due to gravity

gρρ

v*η*18D

o

X-ray Sedimentation

Accounts for Particle Mass Outside Analysis Range.

Analyzes Higher Concentrated Slurries than Most Other Techniques.

Provides Reliable Analyses of Wide Size Range: 300 µm to 0.1 µm.

Requires Only Readily-Available Physical Constants as Parameters.

X-ray Sedimentation

Particle Size Distribution Analysis of Fine Calcium Carbonate Sample.

X-ray Sedimentation

Electrical Sensing Zone

Same principle as Elzone 5380/5382 and Coulter Multisizer 3

Described by ISO 13319 Particle suspended in a conductive

liquid, passing through a narrow orifice, increases resistance through the orifice

Voltage must increase to keep constant current through orifice, same as Elzone 5380 and Multisizer 3

Voltage change proportional to particle volume

Elzone II Principle of Operation

Elzone II Advantages

Counts and sizes organic and inorganic particles

Analyzes materials with mixed optical properties, densities and shapes

Higher resolution than other sizing methods

Lower quantity of sample needed for accurate, easy analysis

Compact size takes up little lab space Automatic orifice blockage detection

Particle Size from Surface Area

Increasing interest in nanomaterialsParticle sizes < 100 nm are of interestMost techniques in this range

questionable• Dynamic Light Scattering

– Provides Mean Size– Difficult if bimodal

Agglomerates make sizing difficult Obtain average size of primary

particles from the surface area and density of the material

Tantalum – TEM Image

TiSi2 – TEM Image

Nickel – TEM Image

Carbon – TEM Image

Particle Size from Surface Area

1 Volume (4/3)πr3)

---------------------- = -------------------

BET x Density Area (4πr2)

Reduces to:

6D (nm) = ---------------------- x 1000

BET x Density

Comparison of Techniques

Sample BET SA

(m2/g)

Avg. PS from SA

Mean PS (TEM)

DLS PS(Sympatec)

Tantalum 89.73 8 nm 6.8 nm 316 nm

TiSi2 97.25 19 nm 12.6 nm 157 nm

Nickel 26.3 35 nm 23.6 nm 1.3 μm

Carbon 62.05 45 nm 31 nm N/A

High Pressure Adsorption

Increasing interest in measurement of adsorption capacity of materials above atmospheric pressureAdsorbent materials

• Gas purification• Hydrogen Storage

Catalysts• Operate above atmospheric pressure

Static Adsorption

Van der Waals forces Pressures to 150 psi Measure uptake of gases at various

real life pressures

High Pressure Isotherm

Dynamic Adsorption

Chemical bondingPressures to 1,000 psiPulse Chemisorption Temperature Programmed:

• Oxidation• Reduction• Desorption

BET SA

High Pressure Chemisorption

Conclusions

Our research is letting us use old techniques in new ways to meet the needs of today’s materials and applications

Acknowledgments

Jeff Kenvin - Micromeritics Greg Thiele - Micromeritics Tony Thornton - Micromeritics Rick Brown – MVA Scientific

Consultants