Iron–iron oxide core–shell nanoparticles synthesized by laser pyrolysis followed by superficial oxidation

• Published in: Applied surface science 2005-07, Vol.247 (1), p.25-31
• Main Authors: Dumitrache, F., Morjan, I., Alexandrescu, R., Ciupina, V., Prodan, G., Voicu, I., Fleaca, C., Albu, L., Savoiu, M., Sandu, I., Popovici, E., Soare, I.
• Format: Article
• Language: English
• Subjects: Carbon nanotube; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Iron core–oxide shell nanocomposite; Laser pyrolysis; Low-dimensional structures (superlattices, quantum well structures, multilayers): structure, and nonelectronic properties; Materials science; Nanoscale materials and structures: fabrication and characterization; Other topics in nanoscale materials and structures; Passivation; Physics; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties)
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2005.01.037

Iron-based core–shell nanostructures were synthesized by laser pyrolysis in a two-steps procedure. In a first step, using a cross-flow configuration, the laser radiation was heating a gas phase mixture containing iron pentacarbonyl (vapors) entrained by an ethylene flow, which plays also the role of an energy transfer agent. Secondly, a carefully controlled in situ passivation of the freshly formed pyrophoric iron nanoparticles created a protective iron oxide shell. The produced nanoparticles (22 nm size diameters) with core–shell features were analyzed by TEM, XRD, SAED and Raman spectroscopy. Majoritary iron and gamma iron oxide/magnetite and minoritary carbon phases were identified. In laser pyrolysis experiments in which the reaction temperature was increased, the catalyzed homogeneous nucleation and growth of carbon nanotubes in the gas phase was observed and is presented here for the first time.