High Compaction and Physical Graphitization of CNT Bundles and Network Via Extreme-Load Compression Using Laser-Induced Shockwave

The physical properties of carbon nanotube (CNT) networks, which are one-dimensional assemblies of CNTs, are still far short of the theoretical limits of individual CNTs. These lowered physical properties of CNT networks are mainly due to their high porosity and relatively weak inter-tube load/electron/phonon transfer efficiency at van der Waals junctions between CNTs and their bundles. We present a simple post-treatment technique utilizing high-intensity laser-induced shockwaves of up to similar to 3 GPa that effectively densify CNT bundles and networks and physically transform CNT bundles into flattened multilayered graphene nanoribbons. CNT assemblies were selectively modified without chemical agents, and the network properties could be tuned by adjusting the laser compression intensity. After laser shockwave compaction, the CNT network structure showed two and three times higher specific strength and modulus than the as-prepared CNT networks. Furthermore, the thermal and electrical conductivities of the CNT networks were also amplified by 400-500% after laser shock compression. These enhancements can be explained by the substantial densification of CNT networks and physically activated graphitization leading to increased load/electron/phonon transfer between flattened CNTs and their bundles.