Nanoscale Maghemite Iron Oxide Powders Prepared by Laser Pyrolysis

摘要

Nano-sized iron oxide particles have been directly synthesized by the laser induced pyrolysis of a mixture containing iron pentacarbonyl/air (as oxidizer)/ethylene (as sensitizer). By the controlled use of the synthesis parameters, mainly iron oxide nanoparticles in the gamma phase are obtained. The variation of the laser power resulted in nanopowders with different particle sizes and crystallinity. The grain size was measured using transmission electron microscopy. A general feature of the synthesized iron-based nanoparticles was their narrow size distributions. Mean particle diameters from about 4 to 9 nm are found. X-ray diffraction reveals different degrees of structural order in samples obtained at different laser powers. Temperature dependent Mossbauer spectroscopy shows that mainly maghemite is present in the sample obtained at higher laser power. The possibility to use selected samples for the preparation of water-dispersed magnetic nanofluids is discussed.