Title :
Oxidation Effect in Cobalt Nanoparticles Magnetic Fluids
Author :
Hong, Jong Soo ; Pyun, Jeffrey ; Park, Yong Wook ; Kim, Chul Sung ; Shim, In-Bo
Author_Institution :
Dept. of Nano & Electron. Phys., Kookmin Univ., Seoul
fDate :
6/1/2009 12:00:00 AM
Abstract :
Cobalt nanoparticles were synthesized by modified thermal decomposition and oxidized in the condition of solution. Crystal structure of fabricated cobalt nanoparticles is determined to be cubic of Fm-3m space group from X-ray diffraction (XRD) measurement. Microstructure of cobalt nanoparticles after the oxidation process show core-shell structure. The particle size and thickness of oxide shell can be controlled by oxidation temperature. The shell thickness of cobalt nanoparticles after the oxidation at 300degC is 4.7 nm, when compared to those oxidized at 250degC with the shell thickness of 2.4 nm due to the change in the oxidation temperature. The magnetic properties of cobalt particles have been measured with VSM. Our results show that cobalt metal (core)/cobalt oxide (shell) has two magnetic behaviors of ferromagnetic and antiferromagnetic properties in magnetic fluid.
Keywords :
X-ray diffraction; antiferromagnetic materials; cobalt; crystal microstructure; magnetic fluids; magnetic particles; nanoparticles; nanotechnology; oxidation; particle size; pyrolysis; space groups; Co; VSM; X-ray diffraction; XRD; antiferromagnetic properties; cobalt metal-cobalt oxide; cobalt nanoparticles; core-shell structure; crystal structure; ferromagnetic properties; magnetic fluids; magnetic properties; microstructure; oxidation process; oxide shell thickness; particle size; space groups; temperature 250 C; temperature 300 C; thermal decomposition; Cobalt nanoparticles; core-shell structure; magnetic fluid; oxidation process;
Journal_Title :
Magnetics, IEEE Transactions on
DOI :
10.1109/TMAG.2009.2018613
