Preparation of CuO nanoparticles by metal salt-base reaction in aqueous solution and their metallic bonding property

This article describes a method for preparing CuO nanoparticles in aqueous solution, and a demonstration of feasibility of metallic bonding with the use of the CuO particles. Colloid solution of CuO nanoparticles was prepared from Cu(NO₃)₂ aqueous solution (0.01 M) and NaOH aqueous solution (0.019 M) at 5–80 °C. Leaf-like aggregates with an average size of 567 nm composed of CuO nanoparticles were produced at 20 °C. The size of leaf-like aggregates decreased with increasing reaction temperature. Metallic copper discs could be bonded using the CuO nanoparticles under annealing at 400 °C and pressurizing at 1.2 MPa for 5 min in H₂ gas. A shear strength required for separating the bonded discs was 25.4 MPa for the CuO nanoparticles prepared at 20 °C, whose aggregates were the largest among the CuO particles examined. These results indicated that the formation of leaf-like aggregates of CuO nanoparticles led to efficient metallic bonding.