Novel porous film by electroplating with an emulsion of supercritical CO2

We conducted an electroplating reaction in a constantly agitated ternary system of dense carbon dioxide (CO2) and electroplating solution with a novel fluorinated surfactant, F(CF(CF3)CF2O)3CF(CF3)COO(CH2CH2O)CH3. The reaction in the emulsion was investigated as a function of the CO2 volume fraction and surfactant concentration. With a low surfactant concentration, the nickel film plated in an emulsion composed of less than 20% CO2 by volume was flat with many pinholes. Electroplating with a 0.09% surfactant concentration in the plating solution by volume formed a smooth film surface free of pinholes. The novel porous film of nickel was fabricated with a 0.12% concentration in the emulsion by volume. Electroplating was found to be possible in an emulsion composed of 40% CO2 and 60% electroplating solution by volume. Smooth plated films free of pinholes were obtained from the emulsion system in the composition range of 20–40% CO2 by volume with the novel fluorinated surfactant. With an increase of the surfactant concentration, nickel films with a multi-porous structure were obtained in an emulsion composed of less than 20% CO2 by volume. This metallic film had a complicated porous structure made up of spheroidal pores of various diameters. We suggested that this novel porous structure could have originated from the emulsion of the electroplating solution and dense CO2 with the novel fluorinated surfactant. The structure could have been fabricated via the formation of “hard” micelles in the reaction system with a specific surfactant concentration and CO2 composition. CO2 in a water micro-emulsion was formed in this reaction system and the dispersion states influenced the novel multiporous structure of the plated film.