Powder 2005

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Materials Characterization Labwww.mri.psu.edu/mcl

Materials Research InstituteUniversity Park, PA 16802

R.I. Malek

Particle Characterization

Outline

• Particle Characterization Laboratory•Techniques

•Particle SizingStatic and Dynamic Light Scattering, Sedimentation, Microscopy, Sieve analysis.

•Zeta PotentialElectrophoresis, Electroacoustic.

• Porosity, Surface Area, Density.• Rheology

• Instruments

•Some Applications

•New Instruments

Particle Characterization LaboratoryExtensive laboratory services for routine analysis and QA/QC. The cooperative alliance with other

laboratories across the University provides expanded access to high-tech equipment for all testing needs.Atomic Force MicroscopyParticle Size Distribution

• Malvern Mastersizer S - Wet and Dry Laser Diffraction (0.05 to 900 mm)• Malvern Zetasizer Nanosizer (0.6 nm to 6 mm)• Horiba CAPA 700 Centrifugal Sedimentation Particle Size Analyzer (0.01 to 300 mm)• Hosokawa Micron Air Jet Sieve

Mercury Intrusion Porosimetry• Pascal 140, 440 Mercury Porosimeter (0.004 mm -116 mm)

BET Surface Area and Porosimetry• Micromeritics Gimini (5 points BET Analysis)• Micromeritics ASAP 2020 for full adsorption/desorption isotherm and pore size distribution.

Zeta Potential• Brookhaven ZetaPALS Zeta Potential Analyzer• Coulter Delsa 440SX Zeta Potential Analyzer• Electro/Acoustic Spectroscopy Zeta Potential and Particle Size Analyzer

Chemisorption and Catalysis • Micromeritics AutoChem 2920, TPD, TPO, TPR, pulse chemisorption, heat of adsorption (-70 °C to 1100 °C) .

Helium PycnometryRheology

• CSL Instruments RheometerTA Instruments Thermal Analysis System (Air-Nitrogen-Argon-Specialty gas)

• Differential Scanning Calorimeter (DSC) -70oC - 600oC• Thermogravimetric/Mass Spectrometry Analysis (TGA/Mass) 1000oC, 1-300 amu• Simultaneous DSC/TGA or DTA/TGA 1500oC–– Contact R. Malek– (814) 865-7341– RQM@PSU.EDU

Particle Sizing• Centrifugal Sedimentation.

• Static Light Scattering (SLS).

• Dynamic Light Scattering (DLS)

Quasi Elastic Light Scattering (QELS)

Photon Correlation Spectroscopy (PCS).

• Electroacoustic (the ultrasound equivalent to light scattering).

• Electrozone Sensing.

Static Light Scattering.Static Light Scattering.

Malvern Mastersizer S - Wet and Dry Laser Diffraction (0.05 to 900 µm)

Instruments at MRL

Dynamic Light Scattering (DLS)Quasi Elastic Light Scattering (QELS)Photon Correlation Spectroscopy (PCS)

relies on measuring the Brownian motion of small particles and relating this to the hydrodynamic diameter, dh of the particle system by means of the Stokes-Einstein equation:

d h = kT/3πηD

where k is Boltzmann's Constant, T is the absolute temperature,η is the viscosity of the medium and D is the diffusion coefficient.

Malvern Zetasizer Nanosizer (0.6 nm to 6 µm)

Brownian MotionParticles move or diffuse as a consequence of thermally driven solvent collisions.

Translational diffusion is not the same as linear diffusion.

The diffusion coefficient (D) is calculated by fitting the correlation curve to an exponential function G(t), with D being proportional to the lifetime of the exponential decay

where I is the scattering intensity, to is the initial time, t is the delay time, A is the amplitude or intercept of the correlation function, B is the baseline, D is the diffusion coefficient, and q is the scattering vector.

Classical vs. Backscatter

Backscatter Benefits

• Enhanced Sensitivity• Larger Size Range

Dilute low MW samples

Concentrated high MW samples

Increased scattering volume and variable cell position

• Higher Concentrations• Better Reproducibility

Typical Analysis Algorithms

• Cumulants– Assumes a single exponential decay, i.e. one particle size– Gives only the Z average size and polydispersity index– Recommended by International Standards Organization

G(t) = B + A e-2q2D

• Multimodal– Fits the curve to the optimal number of exponentials

G(t) = B + ΣA e-2q2D

Ideal Samples

Cumulant & multimodal distribution results are consistent

Typical Samples

Cumulant & multimodal distribution results are NOT consistent

By definition, the DLS measured radius is the radius of a hypothetical hard sphere that diffuses with the same speed as the particle under examination. In practice, particles are solvated. As such, the radius calculated from the diffusional properties of the particle is indicative of the size of the dynamic hydrated/solvated particle.

Hydrodynamic radius

High Concentration - Issues• Multiple Scattering - light scattered from diffusing

particles is re-scattered by other particles => size reduction.

• Excluded Volume - the presence of other particles blocks or hinders free particle diffusion => size increase.

• Aggregation Equilibrium - concentration dependent aggregation of primary particles => increase distribution, polydispersity and average size.

• Electrostatic Interactions - overlapping electric fields lead to interactions that can influence the translational diffusion => change in size.

High Concentration - Solutions• Use the bulk, rather than the solvent,

viscosity.• Use salt.• Dispersion:Chemical dispersion: Dispersants.Mechanical dispersion: Sonication:Excess thermal and mechanical agitation increases thePossibility of collisions between particles causing agglomeration,Rule:

Use absolute minimum mechanical agitation and in short periodic bursts.

0.000001 0.00001 0.0001 0.001 0.01 0.1 1 10 100

Ionic strength (M)

Hydrodynamic size

The solution, add salt!!

Sedimentation

Rate dependent on densityUnderestimates sizeLimited dynamic rangeSlow

Liquid

uSt= (rs - rf)g D²18h

Horiba CAPA 700 Centrifugal Sedimentation Particle Size Analyzer (0.01 to 300 µm)

Conductivity changes as particle passes through apertureRequires electrolytic solution & calibrationProblems w/porous materials

Electrozone Method

+ -----

Coulter Counter

Sieve AnalysisSolids onlyLarge particles38 µm minInexpensiveLimited accuracy,resolution,precision

Hosokawa Micron Air Jet Sieve

Technique and Dynamic Range

.001 .01 .1 1µm 10 100 1000

SieveMicroscope

Sedimentation

Electro zone

Diffraction

Acoustic

Image Analysis

{ Ster

n laye

Zeta PotentialThe liquid layer surrounding the particle exists as two parts; an inner region (Stern layer) where the ions are strongly bound and an outer (diffuse) region where they are less firmly associated.

Within this diffuse layer is a notionalboundary within which the particleacts as a single entity.

The potential at this boundary is theZETA POTENTIAL

Slipping plane

Diffuse layer--100

Distance from particle surface

Surface potentialStern potentialZeta potential

Particle withParticle withnegative negative surface surface chargecharge

Why Is Zeta Potential ImportantParticles do not interact electrostatically according to the magnitude of their surface charge, but according to the zeta potential at the slipping plane.

• The magnitude of the zeta potential gives an indication of the stability of the system

- If all the particles have a large negative or positive zeta potential they will repel each other and there is dispersion stability.

- If the particles have low zeta potential values then there is no force to prevent the particles coming together and there is dispersion instability (aggregation).

Brookhaven ZetaPALS Zeta Potential and Particle Size Analyzer

Instruments at MRL

Coulter Delsa 440SX Zeta Potential Analyzer

Electro/Acoustic Spectroscopy Zeta Potential and Particle Size Analyzer

Acoustic Attenuation

Acoustic wave inFrequency f

Acoustic wave outFrequency f

SuspensionI0 Is

α =⎛

⎝⎜

⎠⎟

∆ LII S

lo gAttenuation

• The double layer is disturbed by an ultrasonic wave. The displacement of the ionic cloud with respect to the surface creates a dipole moment. The sum of these dipole moments over many particles creates an electrical field which is sensed by a receiving antenna immersed in the sample.

Washburn-equation is:

Pascal 140, 440 Mercury Intrusion Porosimeter

WashbornEquation

Mercury Porosimetry of powders

Micromeritics

Gemini BET

Surface Area

Analyzer

Helium Pycnometer

Carrimed CSL Rheometer

ASAP 2020 Accelerated Surface Area and Porosimetery Analyzer. New Instruments

Unique Capability• Two Independent

vacuum systems. • Oil-free “dry” vacuum

pump.• Intelligent degas

system.• New long-duration

cryogen system.• Automated selection of

gas• Ability to connect to a

mass spec.

ASAP 2020 Chemisorption Option

Uses the static volumetric technique to determine the percent metal dispersion, active metal surface area, size of active particles, and surface acidity of catalyst materials.

AutoChem II 2920

•Adsorption

Pulse Chemisorption

•Temperature

•Programmed Studies

–TPR

–TPD

–TPO

Source Material

• Instrument Manuals.

• Several books on specific materials.

• journals.

• Conferences

Acceptable sample forms:

Powders

Suspensions

Charges

• Instrument Charge = $7/Sample.

• Training, data interpretation, sample set-up, etc) = $30/hr.

• Consultation time to discuss your samples, data, etc is free.

Campus resources- people• Raafat Malek, 109 Materials Research Lab Building, Hastings Road

865-7341

rqm@psu.edu

• Jeff Shallenberger, 196 MRI Bldg

865-0337

jxs124@psu.edu

Other resources:• www,mri.psu.edu/mcl/techniques/thermal.asp (links, applications, etc)

• MRI links to publications and abstract (Web of Science) searching (www.mri.psu.edu/linkspubs/)

• The Libraries (http://www.lias.psu.edu/)

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