Synthesis and reactivity of nanophase ferrites in reverse micellar solutions

Self assembly preparative techniques in confined media that lead to magneti c materials with nanometer dimensions are described Synthesis of nanopartic les using the restricted environments offered by surfactant systems such as wafer-in-oil microemulsions (reverse micelles) provide excellent control o ver particle size, infer-particle spacing, and particle shape. These enviro nments have been used in the synthesis of gamma-Fe2O3, Fe3O4, MnFe2O4, and CoFe2O4 with particle sizes ranging from 10-20 nm. The controlled environme nt of the reverse micelle also allows sequential synthesis which can produc e a core-shell type structure, for example Fe3O4 nanoparticles with MnO coa tings. Lyotropic liquid crystal media also offer template effects for the s ynthesis of magnetic nanostructures. The nanoscale ordering of magnetic par ticles when synthesized in lyotropic liquid crystal gels is characterized. The structures, theory and modeling concepts, and novel physical properties of these materials are discussed with emphasis given to the differences be tween course and fine grained magnetic materials. (C) 1999 Acta Metallurgic a Inc.