Application of Mössbauer spectroscopy in the characterization of nanostructured materials

Abstract

Understanding of nanostructured materials is often limited by experimental characterization methods that measure only bulk properties. For example, numerous studies have characterized nanostructured materials using X-ray diffraction for phases present, average grain size, internal strain, etc. In this study, Mössbauer analysis is used to characterize the local atomic site characterization, distribution, and concentrations of attrition milled nanostructure powder. Interatomic analysis provided insight into the mechanical alloying process and the resulting nanostructure not previously reported. Iron powder, blends of iron with 2 wt% aluminum powder, and prealloyed iron–aluminum powder were processed with both argon and nitrogen gas as the processing environments. Mechanical processing resulted in micrometer-size particles with essentially defect-free nanograin interiors. Mechanical alloying iron powder with aluminum resulted in the aluminum being restricted to the grain boundary region. Mechanical processing iron powder in a nitrogen gas environment resulted in nitrogen being either on the grain boundary or in the outer layer of the grain boundary distorting the local b.c.c.-Fe lattice into a b.c.t.-Fe lattice.