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Cu–carbon nanotube (CNT) hybrids combine the advantages of the high electrical conductivity of Cu with the low temperature coefficient of resistance for CNTs, but require enhanced interfacing to improve the electrical performance when exposed to elevated temperatures. In this work, Ti and Ni were investigated as adhesion metals by thermally evaporating 10 nm layers onto a CNT conductor. SEM analysis shows Ni deposits as discrete nanoscale crystallites which coalesce after annealing to 400 °C in H₂/Ar. Ti deposits uniformly along the CNT surface and is stable over such temperatures. A 100 nm deposition of Cu is shown to delaminate frommore » the CNTs after annealing, and the resistance per length (R/L) increases by 40%. The Cu–Ni–CNT exhibits a 125% increase, while the Cu–Ti–CNT achieves a 12% decrease in R/L, for similar annealing conditions. Thus, Ti emerges as an effective adhesion metal, warranting its use in metal–CNT wire technologies for elevated temperature operation.« less

In this work, site-selective copper nanometal seeding through chemical vapor deposition (CVD) is demonstrated as a viable method in concert with solution electrodeposition of bulk Cu to enhance the electrical conductivity of a porous, low-density (0.12 g/cm³, ~9 mg/m) CNT roving. An electrical bias applied directly to the CNT roving promotes Joule heating, which provides the thermal energy necessary for the decomposition of a bis(tert-butylacetoacetato)copper (Cu(tBAOAC)₂) precursor. Localized changes in the resistance within the bulk CNT conductor were used to selectively deposit the precursor at thermally active sites, which were evaluated through thermal imaging. The deposition varies from localized Cumore » deposits at currents producing average temperatures of ~225 °C to a consistent deposition of 10–40 nm Cu particles at applied currents producing average temperatures >300 °C, far above the threshold for the decomposition of the Cu(tBAOAC)₂ precursor. Scanning electron microscopy of a cross section of the roving reveals Cu depositions on the interior of the roving, demonstrating the penetration of the vapor into the CNT network and subsequent decomposition within the roving. A commercial acid-based Cu electroplating solution was used to deposit bulk Cu onto as-prepared and CVD seeded CNT wires, followed by planar densification and H₂/Ar annealing. The finished conductors with Cu loadings from ~30 to 95% w/w which combine CVD Cu seeding and electrodeposition result in specific conductivity values 3-5 times higher than Cu-CNT conductors produced by electrodeposition alone. Ultimately, a CNT hybrid conductor with 94.2% w/w Cu achieved a specific conductivity of 5632 S m²/kg and electrical conductivity of 28.1 MS/m—approaching values previously only seen in metallic conductors. Overall, the present results demonstrate the potential of site-specific CVD toward both seeding metal prior to electroplating and as a possible method toward the enhanced nanometal interconnection of carbon conductors (NICCs).« less