Industrial compatible re-growth of vertically aligned multiwall carbon nanotubes by ultrafast pure oxygen purification process

Reproducible high-yield purification process of multiwalled carbon nanotubes (CNTs) was developed by thermal annealing in ultrapure oxygen. The optimized condition involves thermal annealing via a PID controlled heater in high purity oxygen at temperature of 450 °C for 180 s, which burns out amorphous carbon and reactivate nickel catalyst. Controlling of the purification temperature is important for high yield CNTs, as excessive high annealing temperature results in deformation of the CNTs. Unlike hazardous wet purification treatments, purified CNTs remained vertically aligned and offer the possibility of tailored CNTs length through layer-by-layer process. The purification process is glass compatible and can be adapted to industrial synthesis of CNTs.

Research Highlights
► Pure oxygen process, reduced contamination.
► Lower temperature (400 °C) than previously reported (540 °C).
► Explosive 120% increase in growth rate when compared without oxygen purification.
► Fully transparent and suitable for flexible transparent conductive oxide applications.
► Fully industrial compatible process.