Preparation and oxidation behaviour of cobalt‐coated copper powder

Spherical copper (Cu) particles with an average particle size of ∼2 µm were coated with cobalt (Co) via electroless plating in an acid bath to prepare Co‐coated Cu particles. The prepared particles maintained the initial core–shell structure even under heating up to 350°C in air. However, as the temperature exceeded 350°C, oxide phases of the Co 3 O 4 , CuO, and Cu 2 O phases were formed with microstructural change. Immediately after the oxidation of the Co shell, out‐diffusion of the Cu core through the relatively porous cobalt oxide shell and copper oxidation occurred, thereby forming the outermost copper oxide shell. At 400°C, the copper oxide shell grew and the destruction of the cobalt oxide shell oxidised the edge region of an initial copper core. At the highest temperature of 600°C, a hole was formed at the centre of a particle due to excess out‐diffusion of Cu.