Physical mesomechanics and nonequilibrium thermodynamics as a methodological basis for nanomaterials science

Abstract

The dependence of the Gibbs thermodynamic potential on the molar volume in external force fields has been analyzed to show that all structural-scale states of a solid can be represented by a scale hierarchy of crystal fragmentation as the degree of nonequilibrium of the material increases. In the hierarchy ofscale levels, particular emphasis has been placed on structural ranges: submicrocrystalline (d > 100 nm), nanosized (d = 30−100 nm) and nanostructural (d 30 nm). Special thermodynamic-nanostructural states that differ in qualitative terms from other structural-phase states of solids are associated with a size range less than 30 nm. The nanostructural states are formed solely in highly nonequilibrium solids as a pre-transition stage where translation invariance of the materials is violated in the vicinity of zero Gibbs thermodynamic potential. A central role of local hydrostatic-tension zones in the fragmentation mechanisms seen at all scale levels is substantiated. It is essential that the Gibbs thermodynamic potential for a nonequilibrium crystal be kept within a range of negative values to provide continuity of the material under loading. The nanostructural state of a highly nonequilibrium solid arises in the regions surrounded by quasi-amorphous interlayers characterized by the Gibbs thermodynamic potential of positive sign. Further increase in the degree of nonequilibrium of the solid causes porosity to develop in the local hydrostatic tension zones. A logical implication of this work is that physical mesomechanics and nonequilibrium thermodynamics form a fundamental methodological basis for nanomaterials science.