Scanning electron micrographs of the CNT fibres before (left) and after (right) the parameter optimisation.
Optimisation of the single-step process for spinning CNT fibres requires agility in a multi-dimensional parameter space, so one tends to find parameter ‘islands’ where spinning is possible while exploration tends to follow ‘routes’ through this space. We followed two such routes, one of which drastically improves fibre purity, the other changes the nature of the nanotubes comprising the fibres from multi-walled to single-walled. In terms of the conditions required to make fibres comprising predominately single-walled CNTs, the key appears to be the rigorous control of sulphur addition in trace quantities, coupled with the availability of carbon atoms at the earliest stage after injection.
Full article: http://dx.doi.org/10.1039/C4FD00066H