Particle Size Analysis Flashcards
Challenges
- HETEROGENEOUS powder particle size - RANGE
- IRREGULAR particle shapes
- 2D
Solutions
Equivalent sphere diameter
Statistics
Analytical techniques
Particle shape considers
Convexity, aspect ratio, circularity, solidity
Particle size ANALYTICAL TECHNIQUES
Sieving sedimentation microscopy image analysis laser diffraction dynamic light scattering electrozone sensing
LASER DIFFRACTION:
particle size range
0.01-3500ym
LASER DIFFRACTION:
mechanism
Particles passing through the laser beam scatter light.
ANGLE OF LIGHT SCATTER is measured by photodetectors around sample chamber
- measures LIGHT INTENSITY
LASER DIFFRACTION:
smaller particles have a ____ scatter angle
WIDER
LASER DIFFRACTION:
advantages
RAPID (mins)
minimal sample prep
NO CALIBRATION
DYNAMIC LIGHT SCATTERING:
particle size range
0.3nm-10ym
DYNAMIC LIGHT SCATTERING:
mechanism
(same as laser diffraction)
BUT
Photodetectors measure FLUCTUATIONS in scatter.
Scatter due to BROWNIAN MOTION
Compare LD & DL:
LD uses wet & dry samples (DL: wet only)
LD: broader particle size range
LD measures ANGLE OF LIGHT SCATTER
DL measures FLUCTUATIONS of light scatter
NORMAL DISTRIBUTION CURVE:
mean
median
mode
mean=median=mode
NORMAL DISTRIBUTION CURVE:
shows
UNIFORMITY of particle size
BIMODAL DISTRIBUTION:
relate modes & peaks
1 peak = 1 mode
2 peaks = 2 modes
BIMODAL DISTRIBUTION:
shows
2 or more distinct populations in powder