Dear colleagues,
Does anybody have an experience with Al polishing? We are going to align the polished samples using X-ray reflectivity, so a good quality of polishing and as little roughness as possible are essential. However, we don't care (for the moment) about the crystallographic orientation of the samples, these are likely to be polycrystalline and/or Al alloys. We have the support resins and a range of diamond paste (10um to 10nm)... Could anybody comment on the procedure? Are there any tricks? - because I heard it may be very tricky to polish soft metals (Al, Cu, etc).
Regards and thanks in advance for your contributions.
I can recomment electropolishing, this will give you probably the best surface quality. There are recipes using a mixture of Phosphoric acid (H3PO4) and sulfuric acid (H2SO4) at temperatures around 65°C, some use slightly higher or lower temps. in the range from maybe 50 to 80°C. The polishing time varies between about very few minutes 2-3 min.) to maximum about 10 minutes, depending on the starting surface finish of your sample and eventually the alloying elements, current densitites are around some mA for a sample of 1 cm^2.
I have made quite good experience with an alcoholic solution of perchloric (HClO4) in a molar ratio of about 1:4 molar, and under a reduced temperature of abnout -20°C. Start with a cooled alcohol, and add the HClO4 slowly while cooling and stirring - take care, the reaction is exothermic! Current densities are similar to the above treatment. Starting with a fine-grinded Al surface, you may obtain a mirror-like finish within about 5-10 minutes!
Good luck, Dirk
Thank you for the answer, Dirk!
I'll got to discuss it with the guys in the lab and we'll see which route to stick to. Just in case anybody else is interested there's a web seminar on Al materialographic preparation on the Struers webpage:
http://www.struers.com/e-seminar
which I found useful at least as a starting point.
Regards
N
I think in this case could help electropolishing used after a thorough mechanical polishing. Basics of electropolishing you can found here: https://www.youtube.com/watch?v=RVSB2Mo_PMY
or in special literature (see attached file)
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