Flame-driven Aerosol Synthesis of Copper–Nickel Nanopowders and Conductive Nanoparticle Films

Abstract

We report the continuous one-step synthesis of bimetallic copper-nickel nanostructured coatings by deposition and sintering of metal nanoparticles produced as an aerosol using a flame driven high temperature reducing jet (HTRJ) process. The HTRJ process allows gas-phase (aerosol) formation of metal nanoparticles from low-cost metal salt precursors. These can be collected as discrete powders for subsequent use in formulating conductive inks or for other applications. However, direct deposition of nanoparticles to form coatings allows measurements of electrical conductivity of films of deposited nanoparticles as a function of composition and sintering temperature, without actually formulating and printing inks. This is the approach taken here for the purpose of screening nanoparticle compositions quickly. We characterized the microstructure and composition of both nanopowders and films and found that their composition consistently matched the ratio of metals in the precursor solution. The electrical conductivity was highest (∼10(4) S/m) for films with 60:40 and 40:60 copper-to-nickel mass ratios. These films maintained their conductivity during extended storage (1 month) under ambient conditions. The oxidation resistance and high conductivity observed here suggest that 60:40 and 40:60 Cu:Ni nanoparticles have promise as lower cost replacements for silver nanoparticles in conductive ink formulations.

Flame synthesis of mixed tin‐silver‐copper nanopowders and conductive coatings

“…The consistency of the results in this study (EDX‐based composition in good agreement with nominal composition, similar nanoparticles observed in TEM) with those previous studies provides confidence that the product films consist of partially sintered nanoparticles of approximately the same composition as the nominal precursor composition. The morphology of particles obtained from the HTRJ process is irregular and nonspherical as seen in our earlier published studies . The morphology of particles of four different compositions are shown in Supporting Information Figure S1.…”

“…In this study, we have not performed detailed analysis of the film and powder composition, based in our prior observations in other systems for which the film and powder composition matched the precursor composition almost exactly. In our study of Cu‐Ni powders and films in the HTRJ system, we performed extensive composition analysis of powders collected on filter paper and particulate films deposited on glass substrates, using both inductively coupled plasma optical emission spectroscopy (ICP‐OES) and EDX. We found close agreement between the two techniques and also between the measured compositions and the nominal compositions based on precursor composition.…”

“…However, few studies have reported aerosol synthesis of materials in the SAC system. In earlier work, we demonstrated continuous one‐step synthesis of bimetallic copper‐nickel and copper‐silver nanostructured coatings by deposition and sintering of nanoparticles produced as an aerosol using the flame driven high temperature reducing jet (HTRJ) process. Blattmann et al used flame aerosol deposition of silver nanoparticles onto bare or polymer‐coated glass substrates followed by polymer spin‐coating to produce flexible, free‐standing conductive films .…”

Annealing-induced highly-conductive and stable Cu–organic composite nanoparticles with hierarchical structures

“…Three types of methods to solve this problem have been proposed. The first one is adding alloying elements, such as Ag [8,9] and Ni [10], to enhance its corrosion resistance. For macro-scale materials, alloying is a simple and standard technique; however, for nanosized materials, to control and retain the precise stoichiometry remains a challenge [11].…”

Formation and electrical conductivity of low-dimensional copper structures in porous glass

“…Much research has been done on small copper particles ( [1][2][3][4][5][6], just to mention a few selected recent publications), whereas only sporadic publications were dedicated to the formation and studies of electrically conducting small-dimensional copper structures. Features of formation of conductive chains of copper nanoparticles deposited onto the silicon and glass surface by laser ablation were considered in [7,8]; the factors determining the electrical conduction include the packing density and the degree of the particle surface oxidation.…”