A wet-chemical preparation of a Fe3O4-CuO composite powder in core-shell structure

We developed a process for coating CuO powder with magnetite film from an aqueous solution. Reaction solution contained 0.12 M of FeCl2 and 0.03 M Of CuCl2. The Cu2+ ions prornoted the oxidation of Fe(OH)(2) to form Fe3O4. The solution was maintained at pH similar to6 using CH3COONH4 of 0.2 M as a buffer to prevent the formation of hematite. The CuO grains of a spherical shape and similar to50 pm in size were mechanically suspended in the solution, on which magnetite particles were directly deposited. The mole ratio of Cu2+ / Fe2+ strongly influenced the coverage of the magnetite film as well as the morphology of the constituent grains. When the Fe2+ / Cu2+ mole ratio was 1: 0.5, the spherical magnetite particles of similar to60 nm in diameter coated well each CuO grain with the thickness of similar to3 mum. The prepared powder exhibited that the saturation magnetization and the coercivity reached to similar to5.4 emu/g and similar to575 Oe, respectively. On heating up to 450 degreesC, the powder experienced two oxidations below 400 degreesC, indicating the formation of gamma-Fe2O3. The magnetic composite powder appeared to be stable up to 400 degreesC.