Submitted by Nick / Hope College on Fri, 06/11/2010 - 16:00
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Research
We have samples that are Ni and Fe alloys electrodeposited on Au.  We have evidence to suggest that the metal deposit has migrated from the edges to the center over the course of a year.  Specifically the center is 1.7 times thicker than it used to be.  The diameter has decreased by 26% over the course of the year.  Does anyone have any insight or know anyone with insight with this phenomenon?
Tags
migration
metal
Nickel
Iron
Gold
creep
Nancy Williams / Scripps College, Pitzer College, Claremont McKenna College

I don't know **** from shiniola in your field, but it seems like you're moving from a sheet toward a sphere. That should increase the number of metal-metal bonds, I would think. It's not anything I've heard of happening, but it seems like the thermodynamics would be on your side. I'm envisioning something like the formation of water droplets.

 

Fri, 06/11/2010 - 17:32 Permalink
Barbara Reisner / James Madison University

I've never observed this particular phenomenon, but I think I know a term that might help you learn more - creep. According to Wikipedia,

Creep is the tendency of a solid material to slowly move or deform permanently under the influence of stresses. 

When I did a search on "creep metal migration" I can across a number of hits which could potentially help.

I hope that this is enough to get you started!

Mon, 06/14/2010 - 21:22 Permalink
Joanne Stewart / Hope College
So this begs the question, what is the "stress" in this case? And I'm also wondering if oxidation is playing a role. Maybe we need some engineers to weigh in.
Mon, 06/14/2010 - 23:09 Permalink
Barbara Reisner / James Madison University
I'm speaking out of my field of expertise, but it could be something as simple as lattice mismatch between the deposited and underlying materials. Of course, it could have to do with chemical potential.
Tue, 06/15/2010 - 05:51 Permalink
Jennifer Hampton / Hope College
We don't have evidence of significant oxidation of the metal films.  A bit surprising to me, because they are not exactly thick films, and they've been sitting in air for a year...  But we dont' see oxygen in proton RBS.
Tue, 06/15/2010 - 08:41 Permalink