Rev.Adv.Mater.Sci. (RAMS)
No 2, Vol. 48, 2017, pages 112-130

TOWARDS INTERNAL LENGTH GRADIENT CHEMOMECHANICS

E.C. Aifantis

Abstract

This survey on past, current and possible future directions on chemomechanics was written on the occasion of the 55th birthday of Ilya Ovid'ko. The seminal contributions of his and his team on nanomechanics of defects in solids, based on earlier developments of his mentors and the Russian school on dislocation and disclination theory, can serve as a foundation for extending their work to include the synergy of internal stress and a diffusing chemical agent. Such synergy governs, for example, the fabrication (by electrodeposition) and subsequent use (as filters and nanocatalysts) of micro/nano-sized metallic particles and objects exhibiting large spatial gradients and developed surface in the presence of structural disclination defects. One possible way for achieving this extension (by modeling the underlying physico-chemo-mechanical couplings) is outlined in the present paper which is partly based on a 2016 proposal to European Research Council (ERC) and a 2017 MegaGrant project funded by the Government of Russian Federation. In particular, the paper outlines a number of key concepts and ideas that have not been explored in the area of chemomechanics or mechanochemistry, i.e. at the meeting point of mechanics and chemistry. The aim is to cast these ideas into an initial mathematical framework for describing a variety of coupled chemomechanical phenomena occurring in earth and the human body, as well as in novel engineering nanomaterials and modern technological processes such as those employing nanofilters and nanocatalysts. The new viewpoint advanced here is that in order to capture and control chemomechanical instabilities at the nanoscale we need to resort to internal length and time scales associated with the evolution of the underlying local mechanical stress and chemical agent. One convenient way to account for this is through the introduction of second spatial (Laplacian) and time (inertia) derivatives of the pertinent mechanical and chemistry variables in the constitutive equations describing the evolution of the chemomechanical system at hand.

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