Large-scale synthesis and connections adjustment of the carbon nanotube foams

Carbon nanotubes (CNTs) catch the attention of many social science researchers, due to the remarkable mechanical, thermal, and electrical properties. Among the assemblies of the CNTs, CNT foams are self-assembled three dimensional (3D) network structures that have ultra-low densities, high conductivity, and novel chemical stability, which made them have great potential to use as structure components, heat and electric insulation, cushioning and energy absorption, molecular adsorption and filtration, scaffolds and templates, and composites. [1, 2] However, the mass production technology of the CNT foams is still the bottleneck restricting the industrialization and forward practical applications. In this paper, a novel large-scale synthesis technology of the highly stable carbon nanotube foams is reported. During the production, growing conditions of the floating catalyst chemical vapour deposition method (FCCVD) is modified to control the CNTs fabrication in the reaction zone,[3] and an ideal self-assembled CNT 3D network, which can be continually produced, is finally got. The 3D network can be collected by a rotating barrel, and a CNT foam with 1.5 m in length, 1 m in width, and 2-5 cm in thickness is obtained after 8 hours rolling. However, due to the weak connection points between CNTs, this as-formed foam is easy to collapse, even in the conditions of Gent pressure and solvent spraying. In order to maintain the structure of the CNT foam and make the foam stable, we further explore welding technology between the CNTs. high temperature BNs directly growing, metal ion sputtering, Al₂O₃ atomic layer deposition, and amorphous carbon (AC) welding are compared. It is found that the AC welding can firmly fix the contact points of the CNTs, and increase the mechanical robustness of the CNT foam. This joint-welded CNT foam shows remarkable elastic recoverability on both tensile and compressive strains, and could keep their electrical resistances almost unchanged during stretching, compressing and bending. The FCCVD directly growing with AC welding provides a way to produce large quantity high stable CNT foams that are close to meter scale and lays the foundations for the industrial application.