Morphology and Oxide Shell Structure of Iron Nanoparticles Grown by Sputter-Gas-Aggregation
Much recent research effort has been made on the synthesis, characterization, and property evaluation of core-shell structured Fe nanoparticles. Fundamental properties of these particles depend on both their external crystal faceting planes and the nature of a protective oxide layer. In this paper, the crystal faceting planes and oxide coating structures of core-shell structured iron/iron oxide nanoparticles synthesized by a sputter-gas-aggregation process were studied using transmission electron microscopy (TEM), electron diffraction and Wulff shape construction. The particles grown by this process and deposited on a support at room temperature process have been compared with particles grown and deposited at high temperature as reported in literature. Most synthesis processes produce round particles for particles less than 20 nm in diameter. For larger particles crystallographic facets are observed. It has been found that the Fe nanoparticles formed at RT are invariantly faceted on the {100} lattice planes and truncated by the {110} planes at different degrees. Substantial fraction of particles are confined only by the 6 {100} planes (not truncated by the {110} planes), this contrasts with the Fe particles formed at high temperature (HT) for which a predominance of {110} planes has been reported. Furthermore, at RT no particle was identified to be only confined by the 12 {110} planes which is relatively common for the particles formed at HT. The Fe cubes defined by the 6 {100} planes show a characteristic inward relaxation along the <100> and <110> directions and the reason for this behavior is not fully understood. The oxide shell on the Fe {100} plane maintains an orientation relationship: Fe(001)//Fe3O4(001) and Fe[100]//Fe3O4[110], which is same as the oxide formed on a bulk Fe(001) through thermal oxidation. Orientation of the oxide that forms on the Fe{110} facets differs from that on Fe{001}, therefore, properties of core-shell structured Fe nanoparticle faceted primarily with one type of lattice plane may be fully different from that faceted with another type of lattice planes.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 909473
- Report Number(s):
- PNNL-SA-53940; 2573b; 2573; KC0303020
- Journal Information:
- Nanotechnology, 18(25):Art. No. 255603, Journal Name: Nanotechnology, 18(25):Art. No. 255603
- Country of Publication:
- United States
- Language:
- English
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