Facile-low temperature route towards development of SiC-based coating on carbon nanotubes for improved oxidation resistance

Coating with silicon carbide is a preferred avenue for improving the oxidation resistance of carbon nanotubes. However, expensive and non-scalable techniques like vapor deposition are commonly used to develop such coatings. Against this backdrop, reported here is a facile, cost-effective and low temperature route, based on wet-chemical synthesis, for obtaining SiC-based coating on multi-walled carbon nanotubes (MWCNTs). The coating was achieved by dispersing surface-modified MWCNTs in silica sol (having optimized viscosity), followed by simultaneous reduction and 'carburization' of the silica (wetting MWCNTs) in the presence of Mg at 600 A degrees C. X-ray diffraction and RAMAN spectroscopy confirmed the presence of beta-SiC, while TEM observations revealed the development of uniform and thin coating (similar to 3 nm thick) on undamaged MWCNTs. Thermo-gravimetric and differential thermal analyses up to 1500 A degrees C in air confirmed significant improvement in oxidation resistance for the MWCNTs with SiC-based coating (just similar to 15 % mass loss; as against rapid mass loss of similar to 100 % for uncoated MWCNTs due to oxidation). Additionally, undamaged MWCNTs (with SiC-based coating) could be imaged in TEM after exposure in air at 1200 A degrees C for longer duration.