Annealing effects on the transformations of Fe nanowires encapsulated in the alumina template pores

In this study we have focused our attention on the transformations of iron nanowires (Nws) encapsulated in the alumina template pores with the diameter Øpore from 8 to 30 nm when the samples are stored and annealed in air at temperatures up to 600 °C. Using Mössbauer, XRD and SEM methods we have shown that annealing in air of Fe0Nw arrays in a sealed alumina matrix results in the formation of paramagnetic Fe(II) and Fe(III) compounds, most probably, in a spinel FeAl2O4 (hercynite) and (FexAl1−x)2O3. The diameter of Fe0Nws defined the annealing temperature Tann, at which the ferromagnetic component disappeared, as well as an outcome of transformations. A decrease in the diameter Øpore results in the disappearance of ferromagnetic iron at lower Tann and in a prevailing formation of a (FexAl1−x)2O3 component. The obtained results were used to clear up a mechanism of these transformations.