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Materials Characterization Labwww.mri.psu.edu/mcl
Materials Research InstituteUniversity Park, PA 16802
R.I. Malek
Particle Characterization
Materials Characterization Labwww.mri.psu.edu/mcl
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
Materials Characterization Labwww.mri.psu.edu/mcl
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– [email protected]
–
Materials Characterization Labwww.mri.psu.edu/mcl
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.
Materials Characterization Labwww.mri.psu.edu/mcl
Static Light Scattering.Static Light Scattering.
Materials Characterization Labwww.mri.psu.edu/mcl
Malvern Mastersizer S - Wet and Dry Laser Diffraction (0.05 to 900 µm)
Instruments at MRL
Materials Characterization Labwww.mri.psu.edu/mcl
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.
Materials Characterization Labwww.mri.psu.edu/mcl
Malvern Zetasizer Nanosizer (0.6 nm to 6 µm)
Materials Characterization Labwww.mri.psu.edu/mcl
Brownian MotionParticles move or diffuse as a consequence of thermally driven solvent collisions.
Translational diffusion is not the same as linear diffusion.
Materials Characterization Labwww.mri.psu.edu/mcl
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.
Materials Characterization Labwww.mri.psu.edu/mcl
Classical vs. Backscatter
Materials Characterization Labwww.mri.psu.edu/mcl
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
Materials Characterization Labwww.mri.psu.edu/mcl
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
Materials Characterization Labwww.mri.psu.edu/mcl
Ideal Samples
Cumulant & multimodal distribution results are consistent
Materials Characterization Labwww.mri.psu.edu/mcl
Typical Samples
Cumulant & multimodal distribution results are NOT consistent
Materials Characterization Labwww.mri.psu.edu/mcl
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
Materials Characterization Labwww.mri.psu.edu/mcl
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.
Materials Characterization Labwww.mri.psu.edu/mcl
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.
Materials Characterization Labwww.mri.psu.edu/mcl
0
100
200
300
400
500
600
0.000001 0.00001 0.0001 0.001 0.01 0.1 1 10 100
Ionic strength (M)
Hyd
rody
nam
ic r
adiu
s (nm
)
1/k
Hydrodynamic size
The solution, add salt!!
Materials Characterization Labwww.mri.psu.edu/mcl
Sedimentation
Rate dependent on densityUnderestimates sizeLimited dynamic rangeSlow
Liquid
f
f
b
g
fd
uSt= (rs - rf)g D²18h
Materials Characterization Labwww.mri.psu.edu/mcl
Horiba CAPA 700 Centrifugal Sedimentation Particle Size Analyzer (0.01 to 300 µm)
Materials Characterization Labwww.mri.psu.edu/mcl
Conductivity changes as particle passes through apertureRequires electrolytic solution & calibrationProblems w/porous materials
Electrozone Method
+ -----
Materials Characterization Labwww.mri.psu.edu/mcl
Coulter Counter
Materials Characterization Labwww.mri.psu.edu/mcl
Sieve AnalysisSolids onlyLarge particles38 µm minInexpensiveLimited accuracy,resolution,precision
Hosokawa Micron Air Jet Sieve
Materials Characterization Labwww.mri.psu.edu/mcl
Technique and Dynamic Range
.001 .01 .1 1µm 10 100 1000
SieveMicroscope
Sedimentation
Electro zone
PCS
Diffraction
Acoustic
Image Analysis
Materials Characterization Labwww.mri.psu.edu/mcl
{ Ster
n laye
r
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
0
mV
Distance from particle surface
Surface potentialStern potentialZeta potential
Particle withParticle withnegative negative surface surface chargecharge
Materials Characterization Labwww.mri.psu.edu/mcl
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).
Materials Characterization Labwww.mri.psu.edu/mcl
Brookhaven ZetaPALS Zeta Potential and Particle Size Analyzer
Instruments at MRL
Materials Characterization Labwww.mri.psu.edu/mcl
Coulter Delsa 440SX Zeta Potential Analyzer
Materials Characterization Labwww.mri.psu.edu/mcl
Electro/Acoustic Spectroscopy Zeta Potential and Particle Size Analyzer
Materials Characterization Labwww.mri.psu.edu/mcl
Acoustic Attenuation
DL
Acoustic wave inFrequency f
Acoustic wave outFrequency f
SuspensionI0 Is
α =⎛
⎝⎜
⎞
⎠⎟
1 0
∆ 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.
Materials Characterization Labwww.mri.psu.edu/mcl
Washburn-equation is:
Pascal 140, 440 Mercury Intrusion Porosimeter
WashbornEquation
Materials Characterization Labwww.mri.psu.edu/mcl
Mercury Porosimetry of powders
Materials Characterization Labwww.mri.psu.edu/mcl
Micromeritics
Gemini BET
Surface Area
Analyzer
Materials Characterization Labwww.mri.psu.edu/mcl
Helium Pycnometer
Materials Characterization Labwww.mri.psu.edu/mcl
Carrimed CSL Rheometer
Materials Characterization Labwww.mri.psu.edu/mcl
Materials Characterization Labwww.mri.psu.edu/mcl
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.
Materials Characterization Labwww.mri.psu.edu/mcl
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.
Materials Characterization Labwww.mri.psu.edu/mcl
AutoChem II 2920
•Adsorption
Pulse Chemisorption
•Temperature
•Programmed Studies
–TPR
–TPD
–TPO
Materials Characterization Labwww.mri.psu.edu/mcl
Source Material
• Instrument Manuals.
• Several books on specific materials.
• journals.
• Conferences
Materials Characterization Labwww.mri.psu.edu/mcl
Acceptable sample forms:
Powders
Suspensions
Materials Characterization Labwww.mri.psu.edu/mcl
Charges
• Instrument Charge = $7/Sample.
• Training, data interpretation, sample set-up, etc) = $30/hr.
• Consultation time to discuss your samples, data, etc is free.
Materials Characterization Labwww.mri.psu.edu/mcl
Campus resources- people• Raafat Malek, 109 Materials Research Lab Building, Hastings Road
865-7341
• Jeff Shallenberger, 196 MRI Bldg
865-0337
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/)