SEM
EDX extended analysis
Particles
not (or nearly not) detectable in optical analysis can be found by
SEM analysis and subsequent EDX spectra analysis.
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NaCl (Salt) optical image: Particle is not detectable in VDA 19.1 - ISO 16232 frame |
NaCl (Salt) SEM image |
SEM image can look quite different than optical image and can reveal much information |
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Optical image |
SEM image |
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Corundum optical image |
Corundum SEM image |
Critical components (glass, abrasive materials) cannot be detected with optical methods |
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Optical image (glass fiber) |
SEM image (glass fiber) |
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One
cannot compare particle counts of optical and SEM
methods:
These two detection princples
"see" particles different.
Material |
Optical detection |
SEM detection |
Organic (fiber) |
good |
bad |
Graphite |
good |
bad |
Corundum |
bad |
very good |
Glass |
not at all |
very good |
Salts |
bad |
very good |
SEM-EDX
versus LIBS
(Laser Induced Breakdown Spectroscopy):
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SEM
EDX versus LIBS, Pros and Cons
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LIBS |
SEM-EDX |
Velocity |
Very fast |
Slow (needs vacuum) |
Material depth |
100 µm |
1-2 µm |
Particles |
Only particles visible in optical microscope |
All particles with elements > Boron |
Repeatabilty |
No (particle is destroyed) |
Yes (EDX analysis is non destructive) |
Detection size |
Only particles > 10 µm (laser spot size) |
< 1µm |