Composition-dependent sintering behaviour of chemically synthesised CuNi nanoparticles and their application in aerosol printing for preparation of conductive microstructures

Copper, nickel and copper-nickel nanoparticles were prepared by solution combustion method for use in direct write printing. Structural (X-ray diffraction) and morphological (transmission electron microscope) investigations showed that pure metal (Cu and Ni) and CuNi alloy particles with face-centred cubic crystal structure were formed. Atomic absorption spectrometer studies confirmed that the nanoparticle compositions corresponded to the initial Cu/Ni molar ratios selected for synthesis. Particle size and morphology were significantly influenced by composition, with high Cu content coinciding with small, spherical particles as opposed to larger, irregular shapes observed at high Ni concentrations. X-ray photoelectron spectroscopy measurements revealed that after the reduction process the surface of the alloy nanoparticles was partially oxidised in air and the amount of metallic surface species decreased, while the concentration of oxidic surface species and hydroxides increased with increasing Cu concentration (i.e. decreasing particle size). Dispersions of CuNi nanoparticles have been deposited by use of AerosolJet® and sintered under reducing atmosphere at 300-800 °C in order to prepare conductive structures. Resistivity measurements and microscopical studies (SEM-FIB) of printed and sintered CuNi structures showed that the sintering properties of nanoparticles were dependent on their chemical composition.