Abstract
This work performs metal–metal bonding using CuO nanoparticles prepared with salt base reaction in aqueous solution. A colloid solution of CuO nanoparticles was prepared by mixing Cu(NO3)2 aqueous solution and NaOH aqueous solution. Submicrometre sized leaf-like aggregates composed of CuO nanoparticles were produced at a Na/Cu ratio of 1·7 and at 20°C, though Cu2(OH)3NO3 was also obtained. An aging process, which is a process composed of preparation of the particles at 20°C and then aging them at 80°C, provided transformation from Cu2(OH)3NO3 to CuO with no damage of the leaf structure. The shear strength, which was required for separating discs bonded using the particles as a filler at 400°C in H2 gas, was 32·5 MPa at the maximum for the particles prepared at the Na/Cu ratio of 1·7 with the aging process. These results indicated that the formation of leaf-like aggregates of CuO particles with high purity led to efficient metal–metal bonding.
This work was partially supported by Hitachi Ltd. We thank Professor T. Noguchi (College of Science, Ibaraki University, Japan) for his help in TEM observation.