Synthesis of Ni base nanoparticles by W/O emulsion combustion

To develop a process of fine particle production by spray pyrolysis, spray combustion of W/O (water-in-oil) emulsion, of which water phase was raw material solution and oil phase was fuel for heat source of high-temperature reaction field, was investigated. In this study, nickel oxide particles, which were a preliminary step of the nickel fine particle production, were synthesized and its structural characteristics were evaluated. Mixed solution of nickel nitrate and white kerosene was used as raw material. W/O emulsions were prepared using ultrasonic homogenizer and stirring these raw materials adding a surfactant. These emulsions were burning in a high temperature furnace to produce nickel oxide particles. The mean particle diameter of produced particles was less than 20 nm according to TEM observation. The diameter of the particles was much smaller than the estimated value based on the size distribution of dispersed solution phase in the emulsions and its concentration. Moreover, there is no effect of the concentration of the aqueous solution phase. On the other hand, X-ray diffraction pattern showed that the produced particles were complex of metal nickel with nickel oxide.