ENCAPSULATION OF LANTHANUM CARBIDE IN CARBON NANOTUBES AND CARBON NANOPARTICLES

The morphologies of lanthanum-filled carbon nanotubes and nanoparticles, made by arc-discharging carbon-La2O3 composites, were examined with high-resolution transmission electron microscopy and selected-area electron diffraction technique. The HRTEM images and corresponding SAED patterns obtained from the are-discharge product confirmed that alpha-LaC2 nanocrystals, most of which are single crystals, had been formed within the nanotubes and nanoparticles. The encapsulated alpha-LaC2 crystals showed a tendency to grow epitaxially on the 001 planes of neighboring carbon layers. Twins and polycrystals had also been observed in the closed-off environment. Although partial filling was the most typical growth characteristic for encapsulated alpha-LaC2 nanocrystals, some nanoparticles were found to be completely, or near-completely, filled with alpha-LaC2 nanocrystals. Most encapsulated crystals showed planar and well-defined crystal boundaries with the surrounding carbon layers. The STEM images and nanodiffraction patterns obtained from the interfaces of alpha-LaC2 and carbon sheets provided no evidence for the existence of any possible intermediate layers.