In this paper Co3O4 nanoparticles were synthesized via two different synthesis procedures. In the first method, hydrothermally synthesized β-Co(OH)2 particles were calcined at different temperatures. In the other method, H2O2 was used to eliminate the production of cobalt hydroxide. The amount of H2O2 was the main variable investigated in this study. All samples synthesized via these methods, were investigated for their structure, morphology, specific surface area and magnetization. The results showed that an increase in the temperature of the post heat treatment substantially increased particle sizes and consequently decreased the specific surface area of nanoparticles which influences magnetization. In the H2O2 assisted route, the minimum amount of the oxidant necessary for the complete elimination of the β-Co(OH)2 phase and production of the pure Co3O4 phase was determined to be 0.25 volume fraction. In the H2O2 assisted method, due to elimination of the post heat treatment, the nanoparticles become smaller with a higher specific surface area in comparison with the calcination method. However, the magnetic properties of the nanoparticles in the H2O2 assisted method are influenced by changing the amount of H2O2

Keywords: Cobalt Oxide, Nanostructure, Hydrothermal Method, Magnetic Properties