2, Nanoscience Center, University of Cambridge, Cambridge, Cambridgeshire, United Kingdom
Copper is the dominant material used in electrical conductors due to its availability and excellent electrical conductivity. However as the electronic devices are getting smaller concerns regarding the ampacity of copper conductors have arisen. Moreover poor mechanical properties and relatively high weight resistivity of copper wires and cables have motivated researchers to develop new materials and systems for power transmission. Carbon nanotubes (CNTs) offer high electrical and thermal conductivity, excellent mechanical properties and ampacity 1000 times higher than copper. Although these outstanding properties make CNTs a very promising candidate, complex and costly processing impedes their application as a sole conductor. On the other hand previous research has shown that utilizing CNTs as a filler in a metallic matrix can simplify the processing and results in remarkable properties. In this case interfacial interactions between the two phases significantly influence the morphology and properties of the composite.
In this report electrospinning was utilized to produce Cu-CNT nano-fibers. The effect of CNT surface treatment and electrospinning parameters on the morphology and electrical conductivity of copper-CNT electrospun fibers were studied. For this purpose four different types of CNTs (pristine, oxidized, exfoliated and thiol activated) in different concentrations were used. Also two types of polymeric carriers were studied. Results showed that generally CNT introduction will decrease the uniformity and smoothness of the Cu-CNT fibers. Above a certain critical concentration, fibers cannot be produced. Pristine CNTs have the lowest and exfoliated CNTs have the highest critical concentration. Exfoliated CNTs with concentration as high as 5 wt% yields very smooth fibers with high uniformity which can improve the electrical conductivity. Also, it was shown that although PVP application as the carrier polymer makes the electrospinning process easier, PVA produces fibers with higher smoothness and uniformity. It should be noted that that in nano-scale surface smoothness has a significant effect in the conductivity of fibers.