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Equilibrium for diffusion of gases in metals

by hannaha
Tags: diffusion, equilibrium, gases, metals
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hannaha
#1
Jan7-13, 05:10 PM
P: 1
Hi there,

This could be absolute nonsense but I just got thinking about this. Say you had a certain metal into which a quantity of hydrogen had diffused, and then you placed it in communication with another hydrogen-free metal (say, titanium), would it be possible that the hydrogen would move into the titanium metal, out of the other metal? Coming from a a biology background I was thinking about osmosis (well, any concentration gradient-type process) - does the same apply to gases in metals i.e. would an equilibrium be reached? Or is there no driving force created by the "empty" metal?

Any ideas would be appreciated, thanks!
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Enthalpy
#2
Jan8-13, 07:22 AM
P: 661
I understand it just as you suggest, and this is backed by diffusion processes in semiconductors. Not just for hydrogen, but as well for dopants.

You need an excellent contact between the solids so (1) the diffusing species don't need to pass through air in between (2) hydrogen doesn't go away through the slit.

Also interesting: solids have some affinity for the diffusing species, so the equilibrium between contacting solids is not at identical concentrations.
chill_factor
#3
Jan9-13, 02:01 PM
P: 896
there is a driving force indeed. there is a driving force even for a hydrogen permeated metal in empty space. its just the kinetics that's a problem.

if you weld 2 alloys together, even the alloys start diffusing into one another; however, it may be extremely slow.

mzain
#4
Jan18-13, 12:29 PM
P: 4
Equilibrium for diffusion of gases in metals

there are certain conditions that needs to be fulfilled for a specific reaction to occur. for example for titanium and hydrogen the start of reaction takes place at 300 C. and for the reaction to occur the there must be a contact between the metals in your case. and it will be diffusion controlled process.

i hope it will help u to some extent


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