L. N. Paritskaya, V.V. Bogdanov , Department of Crystal Physics,
Karazin Kharkov National University, Kharkov 61077, Ukraine;
Yu. Kaganovskii, Department of Physics, Bar-Ilan University,
Ramat-Gan 52900, Israel
Diffusion penetration into nano-powder layers was measured in
two-layered Cu-Ni samples in the temperature range 300-700oC. One of
the layers was fabricated by sintering of coarse-grained powder and
served as a diffusion source; the nano-powder layer of 300 mm thick
was rolled up to the coarse-grained layer. The evolution of
microstructure and concentration distribution inside nano-layers was
examined by SEM provided by X-ray microprobe. Correct accounting both
the size dependent diffusion penetration and relaxation inside
nano-structure is one of the important problems in studying of kinetic
properties of nano-structured objects. We distinguish between two
diffusion stages. At the first stage diffusion along grain boundaries
(GBs) is accompanied by GB relaxation. At the second stage diffusion
occurs mainly along stable GBs with leakage into grain interior. We
present the theoretical analysis of diffusion penetration at the
second stage accounting small size of structure element. The triple
products P = kD[gb]d (k is the segregation factor, D[gb] is the GB
diffusion coefficient, d is the GB width) are calculated and analyzed
using different diffusion solutions. The concept of "diffusion grain
size" is introduced and evaluated using experimental data for
characterization the distance between fast diffusion circuits. It
differs from the grain size of the nanostructure.
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