APPLICATION OF MOSSBAUER-SPECTROSCOPY IN THE CHARACTERIZATION OF NANOSTRUCTURED MATERIALS

Understanding of nanostructured materials is often limited by experime ntal characterization methods that measure only bulk properties. For e xample, numerous studies have characterized nanostructured materials u sing X-ray diffraction for phases present, average grain size, interna l strain, etc. In this study, Mossbauer analysis is used to characteri ze the local atomic site characterization, distribution, and concentra tions of attrition milled nanostructure powder. Interatomic analysis p rovided insight into the mechanical alloying process and the resulting nanostructure not previously reported. Iron powder, blends of iron wi th 2 wt% aluminum powder, and prealloyed iron-aluminum powder were pro cessed with both argon and nitrogen gas as the processing environments . Mechanical processing resulted in micrometer-size particles with ess entially defect-free nanograin interiors. Mechanical alloying iron pow der with aluminum resulted in the aluminum being restricted to the gra in boundary region. Mechanical processing iron powder in a nitrogen ga s 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. (C) 1998 Elsevier Science S.A. All rights reserved.