Metal-metal bonding process using cuprous oxide nanoparticles

This work performs metal-metal bonding by using cuprous oxide (Cu2O) nanoparticles prepared by reduction in aqueous solution. A colloid solution of Cu2O nanoparticles was prepared by mixing Cu(NO3)(2) aqueous solution and NaBH4 aqueous solution. Cu2O nanoparticles with a size of 111 f 34 nm, cubic crystal phase, and crystal size of 21.2 nm were produced at initial concentrations of 0.010M Cu(NO3)(2) and 0.010M NaBH4 at a temperature of 40 degrees C. The Cu2O particles contained not only Cu O bonds but also Cu-0-Cu-0 bonds, which indicated formation of fine cluster-like domains composed of Cu-0-Cu-0 bonds. The shear strength required for separating the metallic Cu discs bonded by using the particles as a filler at 400 degrees C in H-2 gas was as high as 27.9 MPa, which was comparable to the shear strengths of metallic Cu particles and CuO particles reported in our previous works. Metallic Cu single crystallites were produced during the bonding process. The presence of the fine cluster-like domains promoted epitaxial particle growth of the metallic Cu and formation of the micron-sized domains composed of nano-sized and submicron-sized single crystals, which provided the strong bonding. (C) 2016 Brazilian Metallurgical, Materials and Mining Association. Published by Elsevier Editora Ltda.