Effect of heat treatment on the structure and stability of multiwalled carbon nanotubes produced by catalytic chemical vapor deposition technique

The multiwalled carbon nanotubes (MWCNTs) produced by catalytic chemical vapor deposition (CCVD) route were heat treated to 2500 °C to improve the structure, morphology and purity level. The process has lead to substantial reduction in the catalytic impurity along with an improved thermal stability and degree of graphitization of these tubes that can possibly lead to its better utilization in various applications. The structural changes following heat treatment have been correlated using various characterization techniques such as Raman spectroscopy, X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy, thermo gravimetric analysis and electron paramagnetic resonance spectroscopy. The electrical and mechanical properties of the polymer composites prepared with heat treated MWCNT show improved properties over the one prepared by as produced MWCNT.

► Post synthesis heat treatment of the nanotubes introduces long range ordering of the layer planes.
► Increased purity and thermal stability of the tubes has been achieved by the removal of catalyst impurity.
► Development of the sword-in-scabbard structure in the multiwalled carbon nanotubes due to heat treatment.
► Improved performance (electrical and mechanical) of the polymer composites using heat treated carbon nanotubes as reinforcement.