title: Synthesis and morphology of iron-iron oxide core-shell nanoparticles produced by high pressure gas condensation.
abstract: Core-shell structured Fe nanoparticles (NPs) produced by high pressure magnetron sputtering gas condensation were studied using transmission electron microscopy (TEM) techniques, electron diffraction, electron energy-loss spectroscopy (EELS), tomographic reconstruction, and Wulff shape construction analysis. The core-shell structure, which is composed of an Fe core surrounded by a maghemite (γ-Fe2O3) and/or magnetite (Fe3O4) shell, was confirmed by fast Fourier transform (FFT) analysis combined with EELS. It was found that the particle size and shape strongly depend on the gas environment. Moreover, extensive analysis showed that NPs with a size between 10-20 nm possess a truncated cubic morphology, which is confined by the 6 {100} planes that are truncated by the 12 {110} planes at different degrees. For NPs larger than 20 nm, the rhombic dodecahedron defined by the 12 {110} planes is the predominant crystal shape, while truncated rhombic dodecahedrons, as well as non-truncated and truncated cubic NPs, were also observed. The NPs without truncation showed a characteristic inward relaxation indicating that besides thermodynamics kinetics also plays a crucial role during particle growth.
authors.affiliation: Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.
authors.forename: Lijuan
authors.initials: L
authors.lastname: Xing
authors.forename: Gert H
authors.initials: GH
authors.lastname: Ten Brink
authors.forename: Bin
authors.initials: B
authors.lastname: Chen
authors.forename: Franz P
authors.initials: FP
authors.lastname: Schmidt
authors.forename: Georg
authors.initials: G
authors.lastname: Haberfehlner
authors.forename: Ferdinand
authors.initials: F
authors.lastname: Hofer
authors.forename: Bart J
authors.initials: BJ
authors.lastname: Kooi
authors.forename: George
authors.initials: G
authors.lastname: Palasantzas