Grain Boundary Diffusion in Nanocrystalline Materials Produced by Severe Plastic Deformation

The model of diffusional mass transfer in the medium with a strong spatial dependence of diffusivity and its application to the grain boundary (GB) diffusion problem is presented. A significant decrease of diffusion activation energy is shown to take place takes place in the vicinity of non-equilibrium grain boundary, which leads to the formation of a region of enhanced diffusion. The generalization of grain boundary diffusion theory is given which accounts for the diffusion enhancement near GB. An original mathematical approach is developed and general asymptotic solutions of the one-and two-dimensional diffusion problems are derived for two types of diffusant source — constant and instant. The applicability domain of presented model is discussed.

Interfacial peroxidase-like catalytic activity of surface-immobilized cobalt phthalocyanine on multiwall carbon nanotubes

The rapid diffusional mass transfer process (DMTP) always results in a highly efficient reaction.