First of all Terry I love this interaction and the site!!!! Thank you. I also would like to express thanks to wulimaster for sharing the UOA.
Second and more specifically regarding MolaKule's theoretical hypothesis on Fick's Law. I am sure you could not be talking about Fick's first law because it is strictly confined to steady state diffusion such as hydrogen gas ‘leaking’ through a steel pipeline, in which it is assumed that the inner and outer surface concentrations are constant.
So that brings us to Fick's second law but before we go there we need to consider a more detailed insight into the term diffusivity. This is explained in terms of the atomic jump frequency, which is highly temperature-dependent. If I understood the UBB coding I could actually write the mathematical expressions here. Instead it comes out in bad grammar
. But here goes: D-Doexp{-Qid/RT}.
where D0 is the frequency factor and QID is equivalent to the enthalpy of interstitial atom migration, DeltaHm. Both these terms can be taken as material constants.
We also need to consider the type of distances involved in interstitial diffusion. It also highlights the difference between total and net diffusion distances (i.e. as given by a ‘random walk’).
That brings us to Fick's second law which requires A derivation. This applies to non steady-sate conditions, i.e. those in which interstitial concentration, CB varies with time. The general form of Fick's 2nd law is given by:
aCb/at=a/ax{Db aCb/ax} The solution for this using carburisation of Fe materials is C=Cs-(Cs-Co)erf{2square root of Dt}
CS = Surface concentration
C0 = Initial bulk concentration
Mojo please point out the discrepancies as you see them on the comparative analysis of different products on our website and I would be happy to respond.
Oilyriser please contact Nick Castellano at
[email protected] for a sample. Good luck with the Canadian fuel!!