Special aspects of diffusion mechanisms and dynamic behavior of Mössbauer iron atoms on a nanoclay surface

Resumo

Using a technique that is developed using Mössbauer spectroscopy, parameters of the diffusion motion and data on geography of the exchangeable iron complexes on a silica–alumina surface of clays were presented. The analyzed natural causes of the temperature behavior of the dynamic Mössbauer parameters allowed the pattern of the atoms' motion to be determined on the basis of various models of diffusion motion. For iron atoms adsorbed in the interwrapper space of the mineral, a jumplike translational diffusion is typical, which allowed determination of the sizes of the fluctuation hollow (r ~ 0.16 nm) necessary for the diffusion of atoms. A nonisotropic character of the diffusion for the interlayer and surface iron atoms caused by structural anisotropy of a clay substrate and by the structure of the iron complexes themselves was found. The surface diffusion of iron dimers occurs in a bounded area (L ~ 0.25 nm) and is rotational.