Abstract
Magnetic cobalt ferrite (CoFe2O4) nanoparticles were prepared by hydrolysis of non-aqueous cobalt-iron(III) carboxylate solution with water. When the initial concentrations of cobalt and iron(III) in the starting solution were 0.075kmol/m3 and 0.15kmol/m3, the complete precipitation of cobalt ferrite was achieved within 20 min at 190°C and 1.3 MPa. The resulting cobalt ferrite particles were free from contamination by the organic starting materials. The particle size of cobalt ferrite drastically decreased from 110 nm to 13 nm as the stirring speed of the starting solution increased from 200 to 800 rpm. The magnetic properties of the resulting cobalt ferrite particles were dependent on the particle size, and the magnetization at a magnetic field of 0.8 MA/m and the coercive force were 51.7μWb·m/kg and 4.8kA/m for the ferrite nanoparticles of 13 nm.
