Module 8 : Surface Chemistry
Lecture 37 : Surface Characterization Techniques
37.4

Microscopic methods of characterization

(a)
 Scanning Electron Microscope (SEM):

Instrumentation and working:

5.

Photomultiplier tube:

The secondary electrons are made to fall on the surface of a photosensitive plate a in a photomultiplier tube (PMT), and then, the strength of these electrons is increased to several hundred of times.
6.
Phosphorescent screen:
 
Thus, amplified electrons are made to fall on a phosphorescent screen, which provides magnified image of the surface.
 
Applications:
1.

Materials: Microphotography and chemical analysis to determine failure mechanisms of metals and ceramics

 
due to erosion and corrosion.
High resolution imaging.
Elemental mapping.
Quantitative point and area analysis.
Automated point analysis of corrosion products.
2.

Environmental: Particles automated particle sizing and typing of combustion ash residues, dust, and other

 
particulate matter.
Particle size and shape.
Fly ash resistivity for electrostatic precipitator performance.
Particle classification or typing based on composition — used to determine the source of particles.
Imaging — high resolution images.
3.

Deposits and wear debris analysis.
4.
Particle sizing and characterization.
5.
Failure analysis.
6.
Contaminant analysis.
7.
Metallurgical studies.
   
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