CNT Coalescence within CNT Fibers via Ultraviolet Pulsed Laser Annealing

Carbon nanotube fibers (CNTFs), composed of numerous aligned CNTs, show promise for a range of industries and applications based on the extraordinary thermal and electrical conductivities of individual CNTs. However, poor interfacial junctions between adjacent CNTs hinder phonon and electron transport, resulting in CNTFs with significantly lower conductivities than individual CNTs. Coalescing smaller-diameter CNTs into larger-diameter CNTs may create a more integrated network with reduced junction resistances, thereby improving interfacial junctions and, thus, transport properties. In this work, we employ ultraviolet pulsed laser annealing (UV-PLA) for targeted heating of CNTFs to induce coalescence. Raman spectroscopy is used to quantify CNT coalescence by analyzing radial breathing modes (RBMs), and the G- (graphitic) and D- (disordered) peaks. Our findings indicate that CNT coalescence can be induced within microseconds using UV-PLA. UV-PLA-coalesced CNTFs were shown to have exceptional thermal conductivities of up to 777 W/mK and electrical conductivities of up to 13.4 MS/m, after redoping.