Flame-synthesized nickel-silver nanoparticle inks provide high conductivity without sintering

A new concept for the synthesis of conductive metal nanoparticle inks (nano-inks) is introduced using a one-step continuous flame-based process. Bimetallic nickel (Ni)-silver (Ag) nanopowders are simultaneously produced and functionalized in a High Temperature Reducing Jet (HTRJ) reactor. The HTRJ process allows rapid aerosol (gas phase) formation of multicomponent metal nanoparticles with relatively high production rates from low-cost metal precursors. Octylamine, a volatile aliphatic amine, is sprayed into the reactor effluent after the particle formation zone to cap nanoparticles as they form. Ni-Ag Functionalized Nano Powders (FNPs) were characterized and compared with Bare Nano Powders (BNPs) to verify that in situ ligand attachment was successful. Nano-inks were prepared by dispersing FNPs in an organic solvent. Conductive films were fabricated using different nano-ink compositions starting from pure Ni to 50 wt% Ni. With the use of a small capping agent, films containing 50 wt% (65 at%) Ni provide an electrical conductivity of 5.14 × 10⁴ S m⁻¹ without any post-processing. Conductivity increased to 4.22 × 10⁵ S m⁻¹ after thermal annealing in an inert environment. These sintering-free bimetallic conductive nanoparticles can be used as a lower cost replacement for current silver inks for single-step printing of conductive traces without post-processing.