Microwave absorbing properties of NiZn-ferrite synthesized from waste iron oxide catalyst

NiZn-ferrite was synthesized from iron oxide catalysts which were thrown away as an industrial waste in the styrene monomer process. Nickel oxide and zinc oxide powders were mixed with finely ground and acid refined waste catalysts, and spinel type ferrite was synthesized by calcination at 900 °C for 2 h followed by sintering at 1325 °C for 5 h. Microwave absorbing properties were investigated by measuring complex permeability and complex permittivity for the composition of NixZn1 − xFe2O4 (x = 0.36, 0.50 and 0.66). The rubber complex ferrite absorber was also produced from calcined ferrite powders without refining. This study showed feasibility of recycling waste iron oxide catalyst as an electromagnetic wave absorber.