Filling of multiwalled carbon nanotubes with oxides and metals

The search for new materials leads to the creation of nanocomposite structures, such as oxide or metal-filled MWNTs, offering the possibility to enhance, on a nanometric scale, the physical properties of both the encapsulated and encapsulating materials. In the present study, MWNTs are synthesized by catalytic decomposition of acetylene and using a template method, filled with transition metal oxides (V, Mn, Fe, Mo, Bi) or semi-metals (Se) to study the restricted crystallization behaviour of the encapsulates due to filling. For transition metal oxides, a one-step filling chemical method was used, where nanotubes are treated with refluxing nitric acid containing a soluble metal nitrate. The corresponding metal oxide is obtained by calcination of the dried insoluble material. For open nanotubes, this method was compared with a filling via capillary action using molten media. Filling rates from 10 to 20 % were observed with all the oxides and the products consisted either of aggregates (Fe2O3) or continuous crystals (V2O5, MoO2). For Se, filling was realized in vapor phase using the two-bulb method, allowing a filling of 50% to 80% of the tubes.