Structure and magnetic properties of iron nanoparticles synthesized by chemical vapor condensation

Iron nanoparticles were synthesized by chemical vapor condensation (CVC) without the aid of LN2 chiller. The powder synthesized at 400 degreesC was a mixture of amorphous and crystalline alpha-Fe. Fully crystallized iron particles were then obtained at and above 600 degreesC. When the reactor temperature was 1000 degreesC, however, nonmagnetic gamma-Fe was stabilized together with alpha-Fe. The synthesized particles, mostly possessing the core-shell type structure, were all nearly spherical, but the average particle size rapidly increased as the temperature increased. The surface layer that enclosed the iron core and became thicker in smaller particles was Fe3O4 or Fe3O4-related amorphous. Except for the one synthesized at 1000 degreesC, the iron nanoparticles were not fully saturated. The iron nanoparticles (similar to20 nm) synthesized at 600 degreesC exhibited, H-i(c) similar to 1.0 kOe and M-s similar to 170 emu/g. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.