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1Universität [email protected] Nanotechnology – L4www.bioceramics.uni-bremen.de
Ceramic NanotechnologyCeramic NanotechnologyLecture 4Lecture 4Characterization ofCharacterization ofNano and Micro ParticlesNano and Micro Particles
Prof.Dr.Prof.Dr.--IngIng..Kurosch RezwanKurosch Rezwan
krezwan@[email protected]
Bioceramics, FB4Bioceramics, FB4UniversitUniversitäät Brement BremenAm Biologischen Garten 2, IW3Am Biologischen Garten 2, IW3D D -- 28359 Bremen28359 Bremen
Tel: +49 421 218 4507Tel: +49 421 218 4507Fax: +49 421 218 7404Fax: +49 421 218 7404
http://www.bioceramics.unihttp://www.bioceramics.uni--bremen.debremen.de//
2Universität [email protected] Nanotechnology – L4www.bioceramics.uni-bremen.de
Outline Course Outline Course „„Ceramic NanotechnologyCeramic Nanotechnology““1. Introduction: Applications, Goals and Challenges2. Powder Synthesis and Conditioning3. Particle Interactions in Colloidal Systems4. Characterization of Nano- and Micro Particles5. Properties of Suspensions6. Stabilization of Suspensions and Additives I7. Stabilization of Suspensions and Additives II8. Colloidal Processing and Rheology9. Shaping Ceramics I: Bulk Materials10. Shaping Ceramics II: Foams11. Shaping Ceramics III: Thin Films12. Sol – Gel Technology: From Molecules to Advanced Ceramics13. Selected Applications of Ceramic Nanotechnology14. Summary
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3Universität [email protected] Nanotechnology – L4www.bioceramics.uni-bremen.de
From Powder to Advanced CeramicsFrom Powder to Advanced Ceramics
Colloid Crystals
Surface Micro Patterning
?? ?? Bulk Materials
SurfaceCoatings
??
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Requirements for Ceramic Powder SynthesisRequirements for Ceramic Powder Synthesis
• Exact fixation of chemical composition• Production of specific particle sizes and particle size distributions• High sintering activity• Economic synthesis: broad application/usability of powders• Environment-friendly and energy saving processes
surface properties e.g. of colloid surface
Processing properties
crack formation/crack propagation
absence of large size secondary phasesabsence of agglomerates/aggregates
→ low ppm range→ defined
microstructure compositionlow impurity level in powder particlesphase composition
→ < 1 μm→ narrow ± 10 %→ uniform
microstructure homogeneity
particle sizeparticle size distributionparticle shape
RemarksImpact on finished partProperties / Requirements
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How to Characterize Nano and Micro Particles?How to Characterize Nano and Micro Particles?
• Density
• Morphology
• Diameter & Size Distribution
• Specific Surface Area
• Surface & Bulk Composition
• Crystal Phase
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Outline LectureOutline Lecture
• Particle Morphology and Size
DensityDefinition Particle SizeMethods
• Other Particle Properties
Crystal PhaseZetapotential / IEPElemental CompositionInterfacial Tension
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Overview Methods Particle Size MeasurementsOverview Methods Particle Size Measurements
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Overview Methods Particle Size MeasurementsOverview Methods Particle Size Measurements
Resolution
> 20 μm
1 nm - 5 μm
50 nm – 1000 μm
> 1 μm
1 nm – 100 μm
10 nm – 1000 μm
50 nm – 1000 μm
Method
Sieving
Light Scattering
Laser Diffraction
Coulter – Counter („Electrozone Sensing“)
Microscope (Optical / SEM / TEM)
Centrifuge Sedigraph with X-Ray Detection
Acoustic Spectroscopy
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What is Porosity / Density?What is Porosity / Density?
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Measuring the Density: Liquid or Gas Measuring the Density: Liquid or Gas PycnometeryPycnometery
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What is What is ““Particle SizeParticle Size””??
deq: equivalent diameter
2-dimensional:circle with equivalent area as projection area of particle
3-dimensional:sphere with similar total volume as particle
deq
XF: Feret diameter
Distance between 2 tangentsto the particle contour
XFmin: smallest feret diameterXFmax: largest feret diameter
XFminXFmax
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Particle Size Distribution ModesParticle Size Distribution Modes
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Cumulative and Differential Particle Size DistributionCumulative and Differential Particle Size Distribution
cumulative volume distribution differential distribution
Particle Diameter D Particle Diameter Dd50
The MEDIAN Diameter is called D50.
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Example Bimodal DistributionExample Bimodal Distribution
DMedian ≈ 30 µm
DMean ≈ 27 µm
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Different Particle Size DefinitionsDifferent Particle Size Definitions
volume distribution: the contribution to the mass is mostly caused by the bigger particles
numerical distribution(each particlecontributes)
Different Measurement methods can result in different results!
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Comparison number/volume distributionComparison number/volume distribution
volume distributionnumber distribution
Emphasis on small particles due to their large number.
Particles are weighted according to their volume
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Light Microscope / SEM / TEMLight Microscope / SEM / TEM
Size Range> 1 µm> 10 nm SEM> 1 nm TEM
AdvantageMorphology directly observableNo assumptions need to be made
DisadvantageSEM/TEM expensivePoor Statistics
Size Agglomerate: 5 µmSize Particle : 37 nm !
The National Bureau of Standards has stated that at least 10,000 separate images (not particles) need to be measured for statistical accuracy in image analysis
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SievingSieving
Size range> 20 µm
Advantagevery cheap
DisadvantageNot suitable for submicron and nano particlesLow resolution
“Sieving Towers” on a vibrating device
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19Universität [email protected] Nanotechnology – L4www.bioceramics.uni-bremen.de
Scattering of light by particles. Detector, shown in red, measures angles and light intensities.
The diffusion coefficient D of the moving particles is obtained from the fluctuating scattering pattern. From the diffusion coefficient the hydrodynamic radius RH is calculated.
Particle Size: Light/Laser ScatteringParticle Size: Light/Laser Scattering
1. The scattered lights from each particle reach to the to detector together
2. They interfere mutually.3. As the particles move, the intensity of the
scattered lights are changed with time.
StrenghtenedPosition Scattered
Light Detecto
r
Size Range1 nm – 5 µm (Light Scattering)50 nm - 5 µm (Laser Scattering)AdvantageSmall particles measurableDisadvantageExpensive, small particles may be concealed
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Coulter Counter (Coulter Counter (““Electro sensing ZoneElectro sensing Zone””))
Particles suspended in a weak electrolyte solution are drawn through a small aperture, separating two electrodes between which an electric current flows. The voltage applied across the aperture creates a "sensing zone". As particles pass through the aperture (or "sensing zone"), they displace their own volume of electrolyte, momentarily increasing the impedance of the aperture. the pulse is directly proportional to the 3-dimensional volume of the particle that produced it.
Size range1 - 100 µm
AdvantageIn situ usable
DisadvantageSmall particle range
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Particle Size: XParticle Size: X--Ray Ray SedigraphySedigraphyParticles falling in a liquid medium. Yellow line coming from the left represents the X-ray source. Not all the X-rays reach the detector. Amount of X-rays adsorbed by the sample represents the mass of particles at specific size.
Size Range10 nm – 100 µm
AdvantageWide size range, Particle Size and Distribution are measured
DisadvantageParticles to be measured should not be X-ray transparent
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XX--Ray Disc Centrifuge (XDC)Ray Disc Centrifuge (XDC)
X – RaySource
DetectorSpinningDisc
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XX--Ray Disc Centrifuge (XDC)Ray Disc Centrifuge (XDC)
( )( ) ifp
ifm
it
tSr
D
tBCII
⋅−=
−=
ρρωη
22
0
/ln18
))(exp(
sign
alin
tens
itytime
diameter
perc
enta
ge
X – RaySource
DetectorSpinningDisc
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Acoustic Spectroscopy: UltrasoundAcoustic Spectroscopy: Ultrasound
[Adapted from Meier L., Zürich]
Size Range10 nm - 1000 µm
AdvantageFast technique that can be applied in situ without altering the system.
DisadvantageOnly mono – and bimodal characterization possible.
Sound Absorption as a function of Frequency is measured.
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BET Measurement: Specific Surface AreaBET Measurement: Specific Surface Area
From the amount of gas adsorbed on the surface the surface area is calculated.Assumption: Monolayer Formation (Langmuir type of adsorption).
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BET ApparatusBET Apparatus
Detection Range> 0.2 m2/g
AdvantageBest technique to determine the Specific Surface Area
DisadvantageParticle Size Distribution not measurable
ParticleBETAD
ρ⋅=
6Calculation Particle Diameter:
Gas Adsorption Method:Mostly N2 used
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27Universität [email protected] Nanotechnology – L4www.bioceramics.uni-bremen.de
BET Surface BET Surface vsvs Particle Diameter for SiOParticle Diameter for SiO22
1
10
100
1000
10000
1 10 100 1000
ABET [m2/g]
Part
icle
Dia
met
er [n
m]
ParticleBETAD
ρ⋅=
6
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Particle Size (μm)0.01 0.1 1 10 100 1000
Erro
r
Dispersion
SamplingInstrumentation
General Note: Repeatability/reproducibility of Particle Size MeGeneral Note: Repeatability/reproducibility of Particle Size Measurementsasurements
Relevance of Factors in repeatability and reproducibility
“Novices in the size-measurement field must understand that most errors in size measurement arise through poor sampling and dispersion and not through instrument inadequacies.”
[Advances in Ceramics, Vol 21: Ceramic Powder Science, page 721, The American Ceramic Society Inc. (1987)]
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Outline LectureOutline Lecture
• Particle Morphology and Size
DensityDefinition Particle SizeMethods
• Other Particle Properties
Crystal PhaseZetapotential / IEPElemental CompositionInterfacial Tension
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Characterization of other Particle PropertiesCharacterization of other Particle Properties
Output
Crystal Phase
Elemental Composition
Zetapotential / Isoelectric Point
Interfacial Tension(Hydrophilicity / Hydrophobicity)
Method
X-Ray Diffraction (XRD)
X-Ray Fluorescence (XRF)
Colloidal Vibration Potential (CVP)
Pendant Drop Method (PDM)
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XX--Ray Diffraction (XRD): Determination of Crystal PhaseRay Diffraction (XRD): Determination of Crystal Phase
OutputsDetection of crystal structureCrystallite size from peak broadening with ScherrerEquation
2 Θ
Cou
nts/
s
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XX--Ray Fluorescence (XRF): Determination of Elemental CompositionRay Fluorescence (XRF): Determination of Elemental Composition
OutputsDetection of Single Elements and their Ratio
Typical XRF Spectra
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Principle XPrinciple X--Ray Fluorescence (XRF)Ray Fluorescence (XRF)
1. An electron in the K shell is ejected from the atom by an external primary excitation x-ray, creating a vacancy.
2. An electron from the L or M shell “jumps in” to fill the vacancy. In the process, it emits a characteristic x-ray unique to this element and in turn, produces a vacancy in the L or M shell.
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The Colloidal Vibration Potential (CVP) Technique: ZetapotentialThe Colloidal Vibration Potential (CVP) Technique: Zetapotential and IEPand IEP
Information about:Zetapotential andIsoelectric point (IEP)
Accuracy: ± 0.15 pH± 1 mV
ultra soundfrequency ≈ 3 MHz
CVP
elec
trode
elec
trode
deflection
particle
[Dukhin, Langmuir, 1999]
''
''
*'
sg
sg
m
mpe
ZZZZCCVP
+⋅
⋅⋅−
⋅⋅⋅=ρκρρμϕ
C’: calibration constantϕ: volume fractionμe: dynamic electrophoretic mobility κ*: complex conductivity of dispersed
systemρp: density particleρm: density mediumZg, Zs: acoustic impedances of
the sound transducer and thedispersed system
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Zeta Potential of selected Oxides and the IEPZeta Potential of selected Oxides and the IEP
-105-95-85-75-65-55-45-35-25-15
-55
1525354555657585
1 2 3 4 5 6 7 8 9 10 11 12
pH
Zeta
pote
ntia
l [m
V]
SilicaTitaniaZirconiaAlumina
IEP towardsbasic pH
Definition Isoelectric Point (IEP):pH where the Zetapotential equals Zero.
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TaskDetermination of the interface and surface tension of liquids
OutputMeasurement of the static interfacial or surface tension as a function of time or of temperature
Measurement of the adsorption/diffusion coefficients of surfactant molecules in oscillating/relaxing drops
Typical measuring range0,05 ... 1000 mN/m
1 2
1 1Op gz
R Rρ γ
⎛ ⎞+ Δ = +⎜ ⎟
⎝ ⎠
where is the fitting parameterand the resulting surface tension
γ
Pendent Drop Method: Pendent Drop Method: HydrophilicityHydrophilicity / / --phobicityphobicity
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t0
Interfacial tension measurementInterfacial tension measurement
1 2
1 1Op gz
R Rρ γ
⎛ ⎞+ Δ = +⎜ ⎟
⎝ ⎠where γ is the fitting parameterand the resulting surface tension
tequilibrium
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Surface Tension measured for Oxide Particle SuspensionsSurface Tension measured for Oxide Particle Suspensions(at pH 7 in water/air, (at pH 7 in water/air, ““pendant drop methodpendant drop method””))
64
65
66
67
68
69
70
71
72
73
74
0 100 200 300 400 500 600 700Time [s]
Surf
ace
Tens
ion
[mN
m-1
]
Water, Silica
AluminaTitania
Zirconia
[Rezwan K., Diss. ETH 2005]
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Surface Tension measured for Oxide Particle SuspensionsSurface Tension measured for Oxide Particle SuspensionsInterpretationInterpretation
60
65
70
75
Water Silica Titania Alumina Zirconia
Surf
ace
Tens
ion
[mN
/m]
decrease surface decrease surface tensiontension
Surface tension decreasesin the following order
SiO2>TiO2>Al2O3>>ZrO2
hydrophobicity
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Outline Course Outline Course „„Ceramic NanotechnologyCeramic Nanotechnology““1. Introduction: Applications, Goals and Challenges2. Powder Synthesis and Conditioning3. Particle Interactions in Colloidal Systems4. Characterization of Nano- and Micro Particles5. Properties of Suspensions6. Stabilization of Suspensions and Additives I7. Stabilization of Suspensions and Additives II8. Colloidal Processing and Rheology9. Shaping Ceramics I: Bulk Materials10. Shaping Ceramics II: Foams11. Shaping Ceramics III: Thin Films12. Sol – Gel Technology: From Molecules to Advanced Ceramics13. Selected Applications of Ceramic Nanotechnology14. Summary