Measurements were made of the diffusivity of B in nanocrystalline Fe. It was shown that the B diffused more slowly in the grain boundaries than in the lattice. The diffusion data were analyzed in terms of type-C' diffusion kinetics. In this situation, the diffuser was confined to the grain boundaries by a large segregation factor. Therefore, although lattice diffusion was faster than grain-boundary diffusion, the grain-boundary diffusion coefficient was easily obtained. The data could be described by:

D(cm2/s) = 1.7 x 10-7exp[-0.59(eV)/kT]

H.J.Höfler, R.S.Averback, H.Gleiter: Philosophical Magazine Letters, 1993, 68[2], 99-105