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.