Coating of TiO₂ nanolayer on spherical Ni particles using a novel sol-gel route

A nano-thin TiO₂ layer was uniformly coated on spherical Ni particles for applications in multilayer ceramic capacitors via a controlled hydrolysis process using TiCl₄, (C₂H₅)₂NH (diethylamine, DEA), and C₄H₉OH as Ti-source, gradual (OH)^- former, and solvent, respectively. At the constant [DEA]/[TiCl₄] =10.6, the Ti-hydroxide could be coated uniformly using the dilute source solution ([TiCl₄] ≤ 0.2 M) while the Ti-hydroxide powder in a separated form was frequently observed at [TiCl₄] ≥ 0.4 M. A uniform coating was attained at the slower precipitation, and the kinetics of precipitation was controlled by tuning the trace amount of water in the solution. The TiO₂-coating not only prevented Ni oxidation but also retarded the sintering between the Ni particles to a large extent.