In-situ synthesis of NiCo/(Ni,Co)O/(Ni,Co)Fe2O4 composite as high-performance microwave absorber

NiCo/(Ni,Co)O/(Ni,Co)Fe2O4 composites were in-situ prepared by solution combustion method using metal nitrates as oxidant and glycine as organic fuel. The amounts of various intermetallic and oxide phases were controlled by amounts of metal precursor. The magnetic properties proved the presence of Ni1-xCox phase instead of pure Ni and Co phases. The combusted composites showed spongy microstructure without any special morphology for various phases. The (Ni,Co)O-49 wt % NiCo composite powders had the effective absorption bandwidth (EAB) of 3.6 GHz at a matching thickness (1.8 mm) in Ku band. By using the ferric precursor, the (Co,Ni)O-30 wt %NiCo-15 wt % (Co,Ni)Fe2O4 composite exhibited a rather broader EAB of 3.9 GHz at a smaller matching thickness of 1.2 mm in Ku band.