Types of Samples
- 1″ , 1.25 ” or 1.5 ” round epoxy mounts
- polished thin-sections (~30 um thick) or thick-sections (<100 um thick)
The objective is to produce a surface for analysis that is absolutely flat, highly polished, and squeaky clean.
- Cutting of Specimens to size
- Mounting the specimen
- Labeling the specimen
- Grinding the specimen
- The initial polish (1 micron diamond, polishing)
- The final polish (0.3 micron alumina on cloth)
- Carbon coating the samples
Why do we need coating for the samples?
Where an uncoated high-resistive material, i.e. exceeding 10E10 ohm, is subjected to electron probe microanalysis (EPMA), the electrons lose their escape way. Hence, an electric charge builds up on the surface of the specimen. This leads to variations in the surface potential, giving rise to the complex and dynamic image artifacts commonly referred to as “charging”. These artifacts will degrade the resolving power and analytical capabilities of the system by introducing astigmatism, instabilities, undue brightness and spurious z-ray signals. This situation is made more difficult because many of the adhesives used to attach specimens to the substrate are themselves non-conductors and prevent the electrical charge from leaking away even from conductive samples. Thus, a thin layer of conductive material (carbon in our lab) material is often applied on the samples prior to observation and analysis to eliminate the problems associated with charging.
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Thin Section Lab Equipment List:
Blue Slab Saw
Whole Rock Saw
Slow Speed Diamond Saw for small samples
Isomet 4000 Precision Saw
Petrothin Vertical Grinder
Metaserv 250 Grinder and Polisher
Logitec LP30 Precision Grinder