Can diffusion occur in solids?

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I see in most newer syllabus textbooks it says that diffusion is the mixing of fluids and diffusion cannot occur in solids
But when is search the web I see lectures and books written on the title diffusion in solids and when I studied I was taught that diffusion occurs in solids but at very very slow rate
So I was just wondering, in the newer findings, is diffusion considered non occuring in solids or is it so slow that they decided to say it doesn't happen?
 

Lord Jestocost

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Astronuc

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I see in most newer syllabus textbooks it says that diffusion is the mixing of fluids and diffusion cannot occur in solids
Please cite the textbooks, which make such a claim. Of course, diffusion occurs in solids, e.g., Cu in Ni, Mg in Al, or Zn in Cu. There is a temperature dependence described by Fick's through a diffusion coefficient given by an Arrhenius equation, D = Do exp (-Q/RT), where Do is some reference diffusion coefficient (pre-exponential), Q is the activation energy for the particular diffusing species, R is the gas constant, and T is the absolute temperature. See chapter 5 of William D. Callister, Materials Science and Engineering, An Introduction, 6th Ed., John Wiley & Sons, Inc., 2003.

https://en.wikipedia.org/wiki/Arrhenius_equation

Atomic diffusion is a significant factor in high temperature systems and nuclear energy systems. In corrosion, in some systems, oxygen (anion) diffuses through the metal oxide, as opposed to metal (cations) diffusing through the oxide. A thermal gradient is part of the physics, and in radiation systems, neutron scattering and ionization by gamma and electron radiation (producing atomic displacements and diffusivity) are factors.
 

Vanadium 50

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Rust is an example of diffusion of oxygen in a solid.
 
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Borek

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The book is wrong. Diffusion in solids is orders of magnitude slower, but other than that it is not different from what happens in liquids and gases.

I also don't like the statement "concentration is the same" - in most cases diffusion is about changing the local concentration. Total amount of the substance is what doesn't change.
 
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The book is wrong. Diffusion in solids is orders of magnitude slower, but other than that it is not different from what happens in liquids and gases.

I also don't like the statement "concentration is the same" - in most cases diffusion is about changing the local concentration. Total amount of the substance is what doesn't change.
I agree
It would have been better to say that molecules are evenly distributed
I don't understand why they would say that diffusion doesn't happen in solids just because it's not studied in the syllabus and it's a slow process which is much harder to observe it still happens. This would create lot of misconceptions as the student moves on to higher education. Children really would hold on to the foundation knowledge that they learn in highschool. The definitions are mostly simplified for easy learn but they are not altered
I still tell my students that diffusion occurs in solids but very slow.
I spent a great deal of time searching for any recent findings on diffusion but always end up between papers published around 1990 to 2013. So I guess that there haven't been any new findings that disprove that diffusion occurs in solids.
I kept on finding books and lectures based on the topic

Thank you for your input everyone
 

Astronuc

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So I guess that there haven't been any new findings that disprove that diffusion occurs in solids.
Probably near absolute zero, diffusion would not occur in solids. One might find examples, but to say unequivocally, that diffusion in solids does not occur is plain wrong, since there is substantial evidence that it does. There is a huge volume of literature that explore this phenomenon in thousands of systems, even without a radiation field. It certainly becomes very important in materials used in nuclear environments, such as nuclear reactors, and more so at higher temperatures.

"Diffusion creep is more sensitive to temperature than other deformation mechanisms. It usually takes place at high homologous temperatures (i.e. within about a tenth of its absolute melting temperature)." One would never use a structural alloy at homologous temperature of 0.9; the creep would be too great and the tensile strength to low for practical applications.

Another interesting study - SPECIAL TOPICS IN SOLID STATE DIFFUSION
https://cpb-us-e1.wpmucdn.com/sites.northwestern.edu/dist/4/1051/files/2016/04/Special-Topics-in-Solid-State-Diffusion-Mahyar-Mohebi-Moghadam-28jgc48.pdf

It is surprising that Cambridge would allow that glaring mistake. In this case, peer review failed miserably, and I wonder if the reviewer new anything about diffusion in solids. It was a basic piece of physics I learned in my first material course more than 50 years ago.
 
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Tom.G

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Printed circuit boards are often Gold plated where they plug into an edge connector. Without the Gold, the contacts oxidize and the contact resistance goes up dramatically. The base metal on circuit boards is generally Copper. If Gold is plated directly over the Copper, the Copper migrates thru the Gold and oxidizes, making poor contact. The fix, implemented on all Gold plated Copper boards is: Gold over Nickel over Copper. The Nickel serves as a barrier layer, preventing the Copper from diffusing into the Gold.

With the number of circuit boards produced, you can be fairly certain that if the Nickel was not needed it wouldn't be there!

Cheers,
Tom
 
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Carbon-carbon composites are often subjected to diffusion at high temperatures to increase the density of the surfaces. I worked for a company that made composite brake and clutch pads. The pads were heated in retorts and methane was introduced. The methane broke down, the carbon diffused into the pads and the hydrogen was drawn off and used to fuel the retorts.
 

CWatters

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I suppose the case hardening of steel is also an example. After the part is made its heated and carbon diffused into the surface.
 

BillTre

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From using cryobiological techniques (preserving living things (cells) in a frozen state), I learned that many frozen cells will not preserve for a long time at temperatures above -80˚C because, on time, water molecules will move from small ice crystals to larger ones, making them larger and thereby destroying cell membranes and cell viability.
Below -80˚C, things preserve much better.
 

Borek

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What about purifying hydrogen by passing it through palladium sheets?
 

russ_watters

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What about purifying hydrogen by passing it through palladium sheets?
Or concentrating it in palladium sheets...?

[runs and hides]
 

jrmichler

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Diffusion in solids is part of heat treating steel and aluminum. From the Wikipedia article on heat treating: the process of diffusion causes the atoms of the dissolved element to spread out, attempting to form a homogenous distribution within the crystals of the base metal. If the alloy is cooled to an insoluble state, the atoms of the dissolved constituents (solutes) may migrate out of the solution. This type of diffusion, called precipitation, leads to nucleation, where the migrating atoms group together at the grain-boundaries.

 
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So nice to see, half a century along, that GCSE stuff is still beset by gross over-simplification...

Our GCE (A-Level) teachers warned us thus, and that our Uni lecturers, first under-grad, then post-grad, would caution us about the previous level's over-simplified stuff...

Down-side, such changing 'truths' between GCSE & GCE totally bamboozled a quorum of kids who lacked the necessary mental agility to adapt. Their textbook was the unimpeachable, unquestionable SOURCE, the Font of all Wisdom ©. How dare it be wrong ?

And, yes, that was a highly regarded 'Faith School'. Sadly, even by mid-teen, an anti-correlation between Traditional Faith and Mental Flexibility was increasingly apparent.

Disclaimer: Even for that oft-weird bunch, I was an outlier. From my year's four-class intake, only two of us were allowed waivers from sitting 'RE' GCSEs, me and a nice young man from the SubContinent...
 

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