Recent Advances in Particle Analysis Paul Kester Micromeritics Instrument Corporation

Areas of Interest for Ceramics  Density ü Skeletal New uses of old technique  Particle Size ü Comparison of Techniques ü New technique for nanoparticles  Surface Area ü High Pressure Studies

Measure Skeletal Density at Various Stages  Molded  Debound  Sintered ü Fully dense Check for theoretical Density ü Indicator for occluded pores Excessive sintering ü Indicator for removal of binder

Future ASTM Method for Density  Committee B09 on Powdered Metals and Powdered Metal Products ü Sub-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 material ü May 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 ü Fraunhofer diffraction ü Forward light scattering ü 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 reflection Transmitted 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,  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 ρ o = liquid density g = acceleration due to gravity 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  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 nanomaterials ü Particle sizes < 100 nm are of interest ü Most techniques in this range questionable Dynamic Light Scattering –Provides Mean Size –Difficult if bimodal ü Agglomerates make sizing difficult  Obtain average size of primary particles from the surface area and density of the material

Tantalum – TEM Image

TiSi 2 – TEM Image

Nickel – TEM Image

Carbon – TEM Image

Particle Size from Surface Area 1 Volume (4/3)πr 3 ) = BET x Density Area (4πr 2 ) Reduces to: 6 D (nm) = x 1000 BET x Density

Comparison of Techniques SampleBET SA (m2/g) Avg. PS from SA Mean PS (TEM) DLS PS (Sympatec) Tantalum nm6.8 nm316 nm TiSi nm12.6 nm157 nm Nickel nm23.6 nm1.3 μm Carbon nm31 nmN/A

High Pressure Adsorption  Increasing interest in measurement of adsorption capacity of materials above atmospheric pressure ü Adsorbent materials Gas purification Hydrogen Storage ü 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 bonding ü Pressures to 1,000 psi ü Pulse Chemisorption ü Temperature Programmed: Oxidation Reduction Desorption ü 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