Recent Advances in Particle Analysis

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Recent Advances in Particle Analysis

• Paul Kester
• Micromeritics Instrument Corporation

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Areas of Interest for Ceramics

• Density
• Skeletal
• New uses of old technique
• Particle Size
• Comparison of Techniques
• New technique for nanoparticles
• Surface Area
• High Pressure Studies

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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

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Future ASTM Method for Density

• Committee B09 on Powdered Metals and Powdered
  Metal Products
• Sub-Committee B09.05 Structural Parts
• Work to start in 6-8 months
• Applies to parts after sintering
• Standard Method for Gas Pycnometry

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Density Equilibration Rate

• Measure Rate of Equilibration for a material to
  determine proper analysis parameters
• Study Rate of Equilibration for various gases on
  a material
• May give information about tortuosity of pores

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Particle Size Techniques

• Laser Light Scattering
• X-ray Sedimentation
• Electrical Sensing Zone
• Particle Size by Surface Area

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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

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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

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Types of Scattered Light
Laser Scattering

• Diffraction
• Reflection
• Refraction
• Absorption

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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.

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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

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X-Ray Sedimentation
X-ray Sedimentation

• Stokes Law for Sedimentation, 1891.
• Mature, well understood and widely practiced
  technique.
• Now fully automated

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Stokes equation
X-ray Sedimentation

• D particle diameter
• ? liquid viscosity
• v sedimentation velocity
• ? particle density
• ?o liquid density
• g acceleration due to gravity

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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.

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Particle Size Distribution Analysis of Fine
Calcium Carbonate Sample.
X-ray Sedimentation
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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

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Elzone II Principle of Operation
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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

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Particle Size from Surface Area

• Increasing interest in nanomaterials
• Particle sizes lt 100 nm are of interest
• Most 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

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Tantalum TEM Image
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TiSi2 TEM Image
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Nickel TEM Image
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Carbon TEM Image
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Particle Size from Surface Area

• 1 Volume (4/3)pr3)
• ----------------------
  -------------------
• BET x Density Area (4pr2)
• Reduces to
• 6
• D (nm) ---------------------- x 1000
• BET x Density

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Comparison of Techniques
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High Pressure Adsorption

• Increasing interest in measurement of adsorption
  capacity of materials above atmospheric pressure
• Adsorbent materials
• Gas purification
• Hydrogen Storage
• Catalysts
• Operate above atmospheric pressure

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Static Adsorption

• Van der Waals forces
• Pressures to 150 psi
• Measure uptake of gases at various real life
  pressures

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High Pressure Isotherm
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Dynamic Adsorption

• Chemical bonding
• Pressures to 1,000 psi
• Pulse Chemisorption
• Temperature Programmed
• Oxidation
• Reduction
• Desorption
• BET SA

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High Pressure Chemisorption
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Conclusions

• Our research is letting us use old techniques in
  new ways to meet the needs of todays materials
  and applications

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Acknowledgments

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