Come togliere la grafite da una sezione lucida analizzata?

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Marco E. Ciriotti
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Come togliere la grafite da una sezione lucida analizzata?

Messaggioda Marco E. Ciriotti » gio 12 apr, 2012 9:58

Alcune risposte alla domanda "Come togliere la grafite da una sezione lucida analizzata?".

1. We use 1/4 µm diamond spray/polish and a polishing pad (on glass) to clean the carbon coating off, then wipe with IPA with a delicate task kimwipe. This has been very effective at cleaning off coatings and also removing fingerprints and other surface contamination.

2. We used to re-polish the section with 1 micron diamond followed by 0.05 micron alumina.

3. One micron alumina on a kimwipe or a polishing pad works pretty well, too. Just the normal concerns about particulate alumina residue in crevices.

4. The simplest way to remove a carbon coat or a gold coat is via a 1 micron Al2O3-H2O slurry (1 part Al2O3 to 8 parts H2O) on a Buehler Polishing Cloth ( Catalog No. 40-7218 Microcloth with adhesive for a 8 inch wheel) aka "moleskin". Gentle rubbing of the thin section or grain mount by hand on the mole skin polishing cloth (on a flat surface) with a generous amount of the slurry will completely remove the coating both on the surface of the mineral grains as well as in between the cracks and grain boundaries. This is due to the the action of the very fine short hairs of the moleskin. The Al2O3 can be easily removed under a running tap (preferably distilled water) or else (if fussy) in distilled water for five minutes under ultrasound. Afterwards the thin section or grain mount should be dried using a soft cloth or a kleenex wipe.

5. I`m polishing coated sections on a Struers grinding cloth called DP Dur using Struers 1 micron diamant DP-Spray P. The cloth is mounted on a rotating steel plate. After 1 min a clean the section in an ultrasonic bath filled with petrol ether and dry carefully with a weak polishing cloth.

6. Normally we would follow the general polishing line as presented by most of you folks over the last day or two; but for soft samples it is required to go back one step:
We apply a technique for all TS preparation using diamond coated rollers; i.e. fixed diamonds. The automated equipment further allows us to adjust the final surface level with high precision. The provided surfaces are reached fast with no undercutting, also with composite materials like concrete or asphalt. The abrasions are fully removed due to the effective cooling media and cylindrical shape of the rollers; hence virtually no pollution of the samples takes place. Our daily routine work requires removing ~5 microns from the already prepared surface of thin sections or 'thick sections'; this level can be easily adjusted to say 1-2 microns, which would suffice to remove the carbon coating (as there is no undercutting). Same trick is used to remove cover glass from thin sections, should it be needed.

7. Occasionally it is necessary to remove cover glasses from archival thin sections for further study.
If the thin section is old enough, the cover glass was affixed with Canada balsam or its successors (not epoxy). Peter Laugensen suggests one method. A simpler one is to place an ice cube on the (cover side up) section and wait until the ice melts. Then insert a razor blade under one corner of the section and lift. Do this while wearing safety glasses, lest the cover glass fly into your eye (a bit of vitreous humor there). I never had success doing this with epoxy-bonded cover glasses.
Marco E. Ciriotti

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