elementcollector1
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Selective Dissolution of Copper and Manganese metals
I have a copper PCB, plated on both sides with a tiny amount of manganese metal. Because copper is so much less reactive than manganese under almost
any circumstances, I needed something that can selectively dissolve copper. I tried ammonium nitrate, hoping for the ammonia complex, and it works,
however slowly. The manganese, however, seems to be oxidising as well.
Does anyone have thoughts on a better method of separating these two metals (with the goal of leaving the manganese metal untouched)?
Pics as soon as I can get them.
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elementcollector1
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Here are some pics (attached):
The first one is showing the copper electrode in the ammonium nitrate solution.
The second shows the manganese plating cell, with copper cathode, MnCl2 aqueous catholyte, vinegar/water/MnCl2 mix anolyte, and lead-tin solder anode
(the last two are not visible).
Unfortunately, it seems as if most of the manganese had oxidized to useless MnO2, rendering a need for another plating.
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weiming1998
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Maybe immerse the PCB in ammonia solution, then bubble oxygen through? That's the only way I could think of without the manganese becoming oxidized.
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blogfast25
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Quote: Originally posted by weiming1998  | Maybe immerse the PCB in ammonia solution, then bubble oxygen through? That's the only way I could think of without the manganese becoming oxidized.
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Freshly prepared manganese is apparently reactive enough to react with water (I've actually seen this happen). EC1 is trying to dissolve the less
reactive metal (Cu) while leaving the very reactive one (Mn) untouched: that's a bit of a tall order...
[Edited on 23-11-2012 by blogfast25]
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AJKOER
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OK, try melting in an inert gas/vacuum.
Cu melts at 1,085 C.
Mn melts at 1,246 C.
May be workable, perhaps using a butane torch whose flame temperature is around 1,300 C in air (which can be lowered by increasing the nitrogen
content of the air intake).
[Edited on 23-11-2012 by AJKOER]
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White Yeti
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Are you sure you can't rather separate out the manganese from the copper once both are dissolved? I don't think you can pull this off without
oxidising the manganese at least to some extent, no matter what method is used. If both the copper and manganese are dissolved, you can simply
precipitate them according to their reduction potentials.
"Ja, Kalzium, das ist alles!" -Otto Loewi
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watson.fawkes
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I can't tell what the real goal is. Are you trying to use the manganese metal as a kind of resist for
removal of the non-masked copper? Or what?
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elementcollector1
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The real goal is the isolation of the thin manganese plate.
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blogfast25
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As per this source:
http://www.americanmanganeseinc.com/wp-content/uploads/2011/...
“Using typical commercial electrowinning conditions, a sheet of manganese metal was
plated over a 24 hour period at a current efficiency of up to 67%. This represents
typical commercial performance.”
A stainless steel 316 cathode was used (see p.68)
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watson.fawkes
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Given the dimensions, I'd call it a foil rather
than a plate.
Given what you've said, I'm quite pessimistic about the prospects of recovering an intact foil from your current piece. If there were a
solvent-reagent that had a very high differential etch rate for copper over manganese, you might have a hope, and even then, getting a liquid in and
out of a thin film between the foil and the substrate seems hard. Getting a manganese foil seems realistic, though, just not with this method.
The biggest chemical problem you've got is that anything that will oxidize a metal plating substrate is likely to oxidize manganese. So you need a
different conductive substrate, one that doesn't need to be oxidized for removal. What comes immediately to mind is a conductive lacquer. Take a
solvent-based lacquer and load it with graphite. Apply it to your mechanical substrate and let it dry. Dissolve it out with lacquer thinner (or any
other handy organic solvent) when you're done. For a substrate, I'd recommend mylar or polyethylene film, something that's unreactive in the plating
bath, flexible, and inexpensive.
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blogfast25
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Or perhaps something much simpler: use a manganese sheet or film as cathode (substrate) in the manganese electrowinning process. That may present some
problems too but from a development starting point it's quite promising, I think.
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12AX7
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You can't just peel it off? Try stainless or titanium instead, few things adhere to these readily.
Tim
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MrHomeScientist
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Myst32YT on Youtube posted a very interesting video some time ago about chemically removing the copper shell from a penny. He found a mixture that
would react with the copper plating but not with the zinc core. A pretty impressive achievement in my opinion, because zinc is usually so much more
reactive. Since Mn is very close to zinc on the activity series, you might consider giving this a try! Here's the link: http://www.youtube.com/watch?v=jRiBYMv6Tz4
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elementcollector1
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That might be something to try, as soon as I get my hands on powdered sulfur. Furthermore, if that works and I get a very thin Mn sheet as the
product, I could follow up on blogfast's suggestion to use Mn itself as the cathode for the electrolytic cell.
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elementcollector1
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I rewatched the video, and frankly I'm a bit worried about his cleanup procedure. I would have to very carefully remove the manganese (because it's on
the surface) from the plate, or figure out some other method of breaking such a potentially fragile item.
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