knowledgevschaos
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Silicon Powder Via Al/Sn Alloy
The other day I was looking at a video of someone melting aluminium with copper, creating the brittle intermetallic CuAl2. I had the idea
that a brittle aluminium alloy can be made by alloying it with other metals, which can easily be crushed into aluminium powder, as long as impurities
of other metals aren't an issue (I'm pretty sure this is what they do with magnalium, but I don't have the balls to alloy this myself, considering
what magnesium does when set on fire)
While researching an aluminium - tin alloy, I came across this document
Here's what it says:
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Aluminium and tin may be melted together in all proportions to give uniform fluid mixtures. The melting cannot be done in the ordinary fireclay or
plumbago crucibles, since the admixture of tin appears to increase greatly the power which aluminium has to reduce the silicates of fireclay, the
reduced silicon becoming absorbed in the body of the metal. In our earlier experiments on these alloys we learned that, even with careful melting at a
temperature not higher than about 750° C., it was impossible to prevent this rapid reduction of silicon. In a few minutes the alloys became badly
contaminated with the m etalloid; in one instance as much as 11 per cent., partly crystalline and partly amorphous, was found in the cooled ingot.
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The idea is that an aluminium tin alloy can be melted in a steel crucible with sand or another form of silica, and the silicon will be reduced and
dissolve in the mixture. Then an ingot is cast from it, which can be dissolved in acid. Aluminium and tin should dissolve, leaving behind finely
powdered silicon which is resistant to acid.
Is this plausible? Is there even any use for finely divided silicon?
Thanks.
Know thy incompatibilities
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Precipitates
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In theory, but aluminium and sand thermite is probably an easier route to elemental silicon:
https://www.sciencemadness.org/talk/viewthread.php?tid=17900
Lots of videos on YouTube. One example:
Make Thermite out of Sand
This reaction is also detailed on the Silicon sciencemadness wiki page, with possible silicon-related projects. If you look up the suggestions there will be lots of threads.
You could try making silicone:
silicon -> copper silicide -> dimethyldichlorosilane -> silicone
i.e.,. silicon to silicone 
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j_sum1
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Aaah. A video from MrHomeScientist.
It was his thermite videos that led me to his blog and then to this board.
I am very grateful!
On topic. I suspect the route you suggest will lead to an impure product.
If the alloy formed contains grains of true intermetallic species, then these will either not dissolve or will dissolve fully, not producing solid
elemental silicon.
OTOH, if it contains grains of a silicon alloy, then after acid treatment it is likely to contain tin/aluminium within the crystal lattice as well as
pockets of material that was not reached by the acid.
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averageaussie
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Magnesium silicide, used to make silane
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