High-temperature investigation on morphology, phase and size of iron/iron-oxide core-shell nanoclusters for radiation nanodetector

Iron/iron-oxide (Fe-Fe3O4) core-shell nanoclusters (NCs) synthesized by a cluster deposition technique were subjected to a study of their high temperature structural and morphological behavior. Annealing effects have been investigated up to 800 degrees C in vacuum, oxygen and argon environments. The similar to 18nm average size of the as-prepared NCs increases slowly in temperatures up to 500 degrees C in all three environments. The size increases abruptly in the argon environment but slowly in vacuum and oxygen when annealed at 800 degrees C. The x-ray diffraction (XRD) studies have shown that the iron core remains in the core-shell NCs only when they were annealed in the vacuum. A dramatic change in the surface morphology, an island like structure and/or a network like pattern, was observed at the elevated temperature. The as-prepared and annealed samples were analyzed using XRD, scanning electron microscopy and imageJ software for a close inspection of the temperature aroused properties. This work presents the temperature induced size growth mechanism, oxidation kinetics and phase transformation of the NCs accompanied by cluster aggregation, particle coalescence, and diffusion.