Preparation and electrical conductivity of Ni/NiO composites using microwave radiation

Nanocrystals of nickel (Ni) and nickel oxide (NiO) composites were synthesized in a short time by the microwave assisted sol-gel process using nickel nitrate hexahydrate as the raw material and nitric acid as the catalyst. For conventional calcination, Ni/NiO composites showed the electrical conductivity in the range of 1.94 times 10^-9 - 8.40 times 10^-9 S/m. For a microwave-induced solution combustion synthesis, the electrical conductivity of Ni/NiO composites was in the range of 0.1-3.4 S/m. The amount of Ni and its crystallite size can be tuned by the microwave parameters (microwave power and exposure time), leading to the formation of Ni/NiO nanocomposites. With increasing the total exposure energy above 40 kJ during microwave radiation, the crystallite size of NiO phase was enhanced and the electrical conductivity of Ni/NiO composites was reduced. Moreover, SEM and TEM analysis revealed that the Ni/NiO nanoparticles were obtained.