Laser diffraction particle size analysis - uni-goettingen.de · • Large grain size range • Very...
Transcript of Laser diffraction particle size analysis - uni-goettingen.de · • Large grain size range • Very...
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Laser diffraction particle size analysis
Methodological aspects, limitations, examples
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Laser diffraction instrument
Retsch Technology, Product catalogue
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Zimmermann, 1996
Intensity vs. angle
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Scattering pattern of different particles
ISO/FDIS 13320-1, 1999
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Beckman Coulter
Measurement of Sub-mircon particles
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Light – particle interaction
Retsch Technology, Product catalogue
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Optical Models
• Fraunhofer diffraction• Particles are spheres• Particles are much
larger than the light wavelength (approx. >10 µm)
• Diffraction angle is small (only near forward scattering is considered)
• Mie-Theory• Particles are spheres• Refraction and
absorption are included
• A complex refraction-index (RI) is necessary
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ISO/FDIS 13320-1, 1999
Differences between Fraunhofer-and Mie-scattering
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ISO/FDIS 13320-1, 1999
Complex Refractive Index (RI)
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ISO/FDIS 13320-1, 1999
Influence of RI and grain size
1µm RI=1.62 - 0i- 0.01i- 0.1i- 1i
0.5 µm RI=1.62 - 0i- 0.1i
5 µm RI=1.5 - 0i- 0.1i
LÜ-Sedimentologie Laser Particle Sizer 11Beckman Coulter
Polarization Intensity Differential Scattering (PIDS)
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LS 13320
Range:0.04 – 2000 µmSample demand:Max. ~ 60 mg (Silt)Max. ~ 10g (Coarse sand)Analysis time:~ 5-7 min (full cycle)
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LS 13320 – Sample chamber
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Grain mixtures
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Starck, unveröff.
Comparison of methods
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Summary
Advantages• Rapid measurement• Large grain size range• Very good resolution• Statistical parameters for
characterisation of grain size distribution
Disadvantages• Restricted comparability
with other methods• Complex refraction
indices partly uncertain or unknown
• Matrix inversion can have more than one solution
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Praktische Durchführung
• Jede Gruppe analysiert ihre Proben
• je eine Probe der Siebanalyse
• Fraktionen der Korntrennung
• Probe der Aräometeranalyse einmal für alle Gruppen