Synthesis of cobalt ferrite colloidal nanoparticle clusters by ultrasonic-assisted solvothermal process

In the present work, cobalt ferrite colloidal nanoparticle clusters were synthesized via solvothermal method using cobalt and iron chlorides, sodium acetate, and ethylene glycol as starting materials. The effects of ultrasonication process of the primary solution on the structure, microstructure, specific surface area, and molecular and magnetic characteristics of the synthesized powders were investigated. Results showed that solvothermal method with/without ultrasonication resulted in nanoscale cobalt ferrite clusters. Field emission scanning electron microscopy micrographs revealed that the synthesized powders were consisted of well-dispersed raspberry-like clusters. Applied ultrasonic waves decreased the mean cluster size while increased the cluster dispersion. The synthesized cobalt ferrite powders had high specific surface area of about 127 m(2)g(-1) which slightly decreased to about 122 m(2)g(-1) after ultrasonication. Generally, the powders showed superparamagnetic properties with a minimum saturation magnetization of 55 emu/g. Ultrasonication for 60 min reduced the coercivity and the effective magneto-crystalline anisotropy of the cobalt ferrite powders.