Synthesis of metallic copper nanoparticles using copper oxide nanoparticles as precursor and their metal–metal bonding properties

Abstract

This work proposes a method for preparing metallic Cu nanoparticles using CuO nanoparticles as a precursor, and performs metal–metal bonding by using the metallic Cu nanoparticles. Colloid solution of CuO nanoparticles with a longitudinal particle size of 13·0±3·0, a lateral particle size of 8·4±2·2 and a crystal size of 7·8 nm was prepared with salt base reaction using Cu(NO₃)₂ aqueous solution and NaOH aqueous solution. Preparation of the metallic Cu particle colloid solution was performed in water using the CuO nanoparticles, hydrazine and cetyltrimethylammonium bromide, which resulted in production of the metallic Cu nanoparticles with a particle size of 50·6 nm and a crystal size of 30·5 nm. Metallic copper discs could be bonded using the metallic Cu nanoparticles under annealing at 400°C and pressurising at 1·2 MPa for 5 min in H₂ gas. A shear strength required for separating the bonded discs was recorded as high as 39·6 MPa.

Keywords:

• Metallic Cu
• Copper oxide
• Nanoparticle
• Metal–metal bonding

This work was partially supported by Hitachi Ltd. We express our thanks to Professor T. Noguchi in College of Science of Ibaraki University, Japan for his help for TEM observation.