The thermal stability of multi-walled carbon nanotubes (MWCNTs) was assessed in situ by transmission electron microscopy. Upon heating, Ni catalysts in MWC-NTs containing bamboo structures shrank from the tail due to evaporation, leading to additional bamboo formation and tube elongation at 800 degrees C, while the MWCNTs with FeSi catalysts remained intact up to 1050 degrees C except for better crystallinity. The physisorbed carbon and/or hydrocarbon on surfaces and super-saturated carbon in the Ni catalysts should be responsible for the phenomena.
Wang, C-Y., Liu, C-P., & Boothroyd, C. (2009). Thermal stability of catalytically grown multi-walled carbon nanotubes observed in transmission electron microscopy. Applied Physics A: Materials Science & Processing, 94(2), 247-251. https://doi.org/10.1007/s00339-008-4765-y