Production and decay of subcritical nuclei in a solid solution |
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Authors: | P M Valov V I Leiman O Yu Derkacheva and V M Maksimov |
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Institution: | (1) Laboratory of Phase-change and Interfacial Transport Phenomena, Tsinghua University, Beijing, 100084, China;(2) Department of Thermal Engineering, Tsinghua University, Beijing, 100084, China; |
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Abstract: | The decay of “subcritical” nuclei in a solid solution has been revealed in the investigation of the CuCl phase nucleation
kinetics in glass. As soon as “supercritical” nuclei with an average radius R = 1.1 nm are created at 500°C, a sharp temperature increase up to 650°C transforms most nuclei created in the first annealing
stage into “subcritical” ones, and this results in the decay of 80% of the nuclei in 5 min, while the remaining 20% of the
nuclei grow in size to 2.4 nm. Their growth provides a sixfold increase in the CuCl phase growth rate against that in conventional
annealing at 650°C. The kinetic dependences of the nucleation parameters—the amount of the phase and the average radius and
concentration of the particles—were determined by the intrinsic absorption spectra of the CuCl nanocrystals. The critical
radius of the CuCl nanomelt at 650°C has been estimated as 1.3 nm and the evaporation heat of the CuCl phase molecules in
glass, as 13 kJ/mol. It is shown that multistage annealing makes it possible not only to control the parameters of the particles
of the new phase, but also to determine the critical parameters of the initial nucleation stage. |
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