Synthesis of Micron and Submicron Nickel and Nickel Oxide Particles by a Novel Laser-Liquid Interaction Process

The laser-liquid-solid interaction is a new technique for synthesis of nickel and nickel oxide particles. The process uses a continuous-wave CO₂ laser beam as the source of thermal energy required to induce precipitation reactions in solution. The uniqueness of the process is the synthesis reaction taking place in a localized region, which allows better control of the chemical reaction. Porous nickel and nickel oxide powders have been synthesized by laser-induced reactions between a nickel nitrate hexahydrate [Ni(NO₃)₂ · 6H₂O] precursor and 2-ethoxyethanol-based mixtures. Nickel powders were produced after irradiating a solution of the precursor salt and a 2-ethoxyethanol and d-sorbitol mixture. Crystalline nickel oxide (NiO) powders were isolated after irradiating a solution containing the precursor salt and a 2-ethoxyethanol and water mixture. Powders containing both nickel and nickel oxide crystalline phases were produced after irradiating a solution of the precursor salt and 2-ethoxyethanol. The mean particle diameter is found to be sensitive to irradiation time, substrate thermal conductivity, irradiation power density, and solution concentration. It is hypothesized that nucleation and growth of crystalline phases occurring in irradiated solutions are thermal driven.