Diffusion coefficients cation

In part the parabolic law may also apply to multilayer oxide systems where the cation diffusion coefficient is much higher in the lower oxide tlran in the higher oxide, which, growing as a thin layer, undergoes plastic deformation at high temperatures, thus retaining the overall oxide layer as impervious to enuy of tire gas. 

In the case of Fe3 504, the difference in cation diffusion coefficients in the growing compound on the one hand and in the non-growing one on the other was found by S. Tinkler and R. Dieckmann160 to be approximately two orders of magnitude. 

Tsitsishvili et al., in their book on natural zeolites [29] tabulate values of cation diffusion coefficients. 

Only cation diffusion coefficients were determined. 

The overall diffusion current is not zero because of the difference between the anion and cation diffusion coefficients. As shown in an example already described In section 4.2.1.5 the calculation gives ... 

This value for the diffusion coefficient would apply to the case of interstitial diffusion in a metal having its atoms in cubic close-packing. It should also apply to the case of cation diffusion in the NaCl structure if the diffusion is by a vacancy mechanism. However, this calculated cation diffusion coefficient would have to be reduced by the correlation factor. It would probably not be applicable to interstitialcy diffusion, because the sequence of energy barriers to be surmounted for diffusion by that mechanism would probably differ from those proposed here. 

Oxygen and cation diffusion coefficients in alumina scales... 

Chromium is used as an isotopic marker for aluminium. Taking into account that both chromium and aluminium cations diffuse in the same way, the results obtained on chromium diffusion coefficients in alumina scales can be applied to aluminium cation diffusion coefficients in the same scale. Indeed, it is easier to use a chromium isotope as a diffusive species than to use aluminium, which has no natural isotope one can only use an artificial aluminium isotope, Al, which is radioactive and very expensive. Very few works have used this radioactive tracer [90,101]. 

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