# Harnessing phase separation to easily make Li film

I want to make a thin, smooth film of pure lithium in a glovebox.

In general, I think that I can use a phase separation approach. I will heat a bath of mineral oil above Li's melting point, then pour liquid Li inside and let it cool slowly. The Li should cool on top and the only curvature should be due to miniscus effect.

I would think that if I used a third, lighter liquid than the Li, I could put a large column of it on top of the Li. However, this requires having a lighter liquid. Li, at melting point, has a density around $\pu{500 kg m-3}$.

Can anyone suggest a suitable lighter liquid?

• I can't think of any. Then again, what's the point? The meniscus would still be there. – Ivan Neretin Aug 25 '17 at 13:57
• Top liquid would supply more pressure and reduce meniscus. At least thats my thinking in theory, doesnt mean itll work in practice – User2341 Aug 25 '17 at 14:02
• I don't think there's any liquid that could be used here, pressurised gas may work. – Mithoron Aug 25 '17 at 14:07
• I have a suspicion it won't work. Molten metals usually have strong surface tension, so a thin film might fragment into rather large drops. – permeakra Aug 25 '17 at 14:55
• Do you have any better suggestions? I'm just trying to make an Li foil/film with a very, very smooth surface. – User2341 Aug 26 '17 at 19:19

It is the surface tension that matters, and adding liquid might change that in an unpredictable way. Then again, you can achieve the same result without any extra liquid. Just use different material for the container. I guess using metal instead of glass would make the meniscus bend in the opposite direction. With some tweaking, it might be possible to find the material with wetting angle of $90^\circ$ that would make lithium surface perfectly flat, but I don't think it is worth the effort.