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Author: Subject: Alloying nickel and aluminum to make Raney nickel
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[*] posted on 20-11-2018 at 15:33
Alloying nickel and aluminum to make Raney nickel

I finally have access to a gas welder with an oxygen tank, and figured it could produce temperatures hot enough to alloy nickel and aluminum. First I got the nickel (1970s Canadian nickels) hot enough that it melted and glowed sort of a white-orange color, in a shallow granite crucible. The coins gradually melted until they fused, then melted into a pool. Then I tried to add aluminum. It sort of worked. At the temperatures I was working with, aluminum catches fire and burns pretty easily, even with a reducing flame.

But I did manage to make several samples, and some worked better than others. A few times, the resulting alloy was brittle enough to break using two pairs of pliers, but other times it wasn't. In no cases did sodium hydroxide disintegrate any of the samples though. They all resulted in a small amount of powder with the bulk of the sample remaining untouched. Does anyone have any suggestions for obtaining better results? Would it hurt anything to use an excess of aluminum, to allow the sodium hydroxide to do a better job at disintegrating samples? Has anyone had real success at doing this before?

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[*] posted on 20-11-2018 at 16:19

Aluminum oxidizes readily with exposure to air. The wiki article is probably a good starting place and has a few links that might be followed. I imagine shielding gas, as you would use when welding aluminum is a good choice, probably argon. A graphite crucible might be ideal. You need to reach 1300C for the 50:50 alloy to be liquid, which is below the mp of pure nickel. Nickel powder might be more easily dissolved in molten aluminum than the approach you're taking.

It seems like a small amount of a third metal is usually added, the alloy is also powdered before activation in relatively concentrated, hot NaOH solution.
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S.C. Wack

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[*] posted on 20-11-2018 at 17:04

Weygand/Hilgetag details a process. Raney also claims a thermite process can give an active catalyst.

More Al would presumably give more NiAl3, which dissolves better than Ni2Al3 but naturally gives less active Ni. Raney alloy is probably best made in large batches (edit: or little crucibles).

[Edited on 21-11-2018 by S.C. Wack]

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[*] posted on 20-11-2018 at 19:33

While I know absolutely nothing about this subject, personally, I'd just put everything in the crucible and put a lid on it then melt it, checking under the lid occasionally and maybe stirring with a steel rod. A flux might help keep things from oxidizing.

I think Raney nickel typically starts out as a finely powdered aluminum-nickel alloy. I'm not really sure about the best way to crush it, but I'd probably try hammering it and running it through a ball mill.

The rate of cooling might affect the properties of the alloy, especially if it contains significant amounts of carbon. Can you dump the molten metal immediately into water after removing the heat? (Warning: probably super dangerous without a long-handled ladle.)

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