Upcoming SlideShare
×

# Introduction to Laser Diffraction

3,491
-1

Published on

Ian Treviranus, Product Line Manager for HORIBA Particle, discusses fundamental principles and practical considerations of laser diffraction for particle size analysis.

This presentation is archived with the original webinar video in the Download Center at www.horiba.com/us/particle.

Published in: Technology
1 Like
Statistics
Notes
• Full Name
Comment goes here.

Are you sure you want to Yes No
• Be the first to comment

Views
Total Views
3,491
On Slideshare
0
From Embeds
0
Number of Embeds
0
Actions
Shares
0
115
0
Likes
1
Embeds 0
No embeds

No notes for slide

### Introduction to Laser Diffraction

4. 4. Core Principle Why? Because the angle and intensity of the scattered light depends on its size Larger Particle Smaller Particle© 2011 HORIBA, Ltd. All rights reserved.
5. 5. Core Principle So all we need is a light source, a particle, light detectors, and a German mathematician Joseph von Fraunhofer Gustav Mie or …but this guy has a better solution© 2011 HORIBA, Ltd. All rights reserved.
11. 11. A “particle” in disguise Light Scatter occurs whether from a slit, a pinhole or a particle. It occurs at the edge of an object. A SLIT and θ PARTICLE of the same size produce the same diffraction pattern θ θ© 2011 HORIBA, Ltd. All rights reserved.
12. 12. Size affects angle Large particles scatter light through SMALLER angles θ Small particles scatter light through LARGER anglesLarge Particle θ Small Particle © 2011 HORIBA, Ltd. All rights reserved.
13. 13. Size affects intensity LARGE PARTICLE: Low angle scatter Large signal Wide Pattern - Low intensity SMALL PARTICLE: Narrow Pattern - High intensity High Angle Scatter Small Signal© 2011 HORIBA, Ltd. All rights reserved.
14. 14. Other factors Size, Shape, and Optical Properties also affect the angle and intensity of scattered light Extremely difficult to extract shape information without a priori knowledge Assume hard sphere model Optical properties (refractive index) explain refraction Key difference between Fraunhofer and Mie© 2011 HORIBA, Ltd. All rights reserved.
16. 16. Most flexible size analysis The core relationship between size and scattered light works for: Nanoparticles Small micronized particles Large micronized particles Wide dynamic size range© 2011 HORIBA, Ltd. All rights reserved.
17. 17. Most flexible size analysis The core relationship between size and scattered light works for: Suspensions – solid-liquid Powders – solid-gas Emulsions – liquid-liquid Flexible sample types© 2011 HORIBA, Ltd. All rights reserved.
18. 18. Most flexible sizing Wide dynamic size range Multiple sample types No a priori information needed to monitor size change Accuracy is improved with refractive index (when smaller than approx. 30 microns) Very fast measurement think seconds, not minutes Easy to use, easy to interpret First principal measurement no calibration© 2011 HORIBA, Ltd. All rights reserved.
19. 19. Nanoparticle Sensitivity Laser diffraction can measure 30 nm! Typical setup is 2 light sources: red & blue 30, 40, 50, 70 nm latex standards 30 nm colloidal silica© 2011 HORIBA, Ltd. All rights reserved.
20. 20. Nanoparticle Sensitivity Some (unfounded?) concerns with particles < 100 nm Diffraction good at determining sub-100 nm particles in presence of larger particles Software set to display % under any given size Data shown left is for skin cream and TiO2 suspension© 2011 HORIBA, Ltd. All rights reserved.
21. 21. Large Particle Sensitivity 14 100 90 12 80 10 70 60 8 Coffee Results q(%) 50 6 40 4 30 20 2 10 0 0 10.00 100.0 1000 3000 Diameter(µm)© 2011 HORIBA, Ltd. All rights reserved.
22. 22. Flexible Sample Handlers 10 ml 35 ml 200 ml powders •Wide range of sample cells depending on application •High sensitivity keeps sample requirements at minimum •Technology has advanced to remove trade-offs© 2011 HORIBA, Ltd. All rights reserved.
24. 24. Monitor Process Quality •Black size distribution is internal standard •Red result is considered a passing batch •Blue result is a bad batch •Highlights problem in production •All accomplished with complex product formulation© 2011 HORIBA, Ltd. All rights reserved.
25. 25. Monitor Product Quality Median (Peak 1) : 0.031 μm Median (Peak 2) : 1.75 μm 0.05wt% •Product quality and performance can be located at tails •Diffraction is “resolution limited” technique, but can still have success finding outlier populations© 2011 HORIBA, Ltd. All rights reserved.
26. 26. Minimize Sample (MiniFlow) Colloidal Silica (weak scatterer) Magnesium Stearate Median (D50): 35 nm Median (D50): 9.33 μm Sample Amount: 132 mg Sample Amount: 0.165 mg Bio-degradable Polymer Median (D50): 114 μm Sample Amount: 1.29 mg© 2011 HORIBA, Ltd. All rights reserved.
28. 28. Measurement Workflow Prepare the system Align laser to maximize signal-to-noise Acquire blank/background to reduce noise© 2011 HORIBA, Ltd. All rights reserved.
31. 31. Measurement Workflow Measurement Click “Measure” button – Hardware measures scattered light distribution – Software then calculates size distribution© 2011 HORIBA, Ltd. All rights reserved.