Abstract Submitted to the NANOTUBE'02 Workshop:

The controlled production of nanotubes made of layered BC2N and CNx using thermolytic processes is presented. In addition, the electronic and field emission properties, as well as the density of states (DOS) of CNx and BCx nanotubes will be discussed from an experimental and theoretical standpoint. Experimentally, it is also found that B-doped tubes produced using arc discharge techniques, which contain B mainly at the tips, exhibit stable electron field emission at lower turn on voltages (1.4 V/micron) when compared to pure single- and multi-walled carbon nanotubes (2.8 and 3.0 V/micron respectively) measured under the same conditions. The production of aligned Fe-doped carbon nanotubes using pyrolytic approaches will also be discussed. The magnetic properties of these material are also investigated using SQUID magnetometry. We find that the material exhibits large magnetic coercivities ranging from 500-2500 Oe, a value which is much higher than that reported for bulk Fe (e.g. 60-80 Oe) These results indicate that these material could be used in the fabrication of high magnetic density data storage devices. From a theoretical point of view, we also study the magnetic properties of BCC Fe nanowires of various morphologies and dimensions, using a phenomenological approach involving a classical Heisenberg Model in conjunction with the Monte Carlo approach. We determine the magnetization and spin polarizations under various applied fields. We also report on the magnetization of ferromagnetic/antiferromagnetic nanowires at zero field. Our results indicate that the magnetic properties of the nanowires are mainly influenced by their surface. Antiferromagnetic contributions are also observed when the material is not purely ferromagnetic. Finally, it will be shown that high electron irradiation during annealing at 700 – 800 °C, is capable of coalescing and joining single-walled nanotubes (SWNTs). The merging process is also investigated at the atomic level using tight-binding molecular dynamics (TBMD) and Monte Carlo (MC) simulations. Vacancies induce the merge via a zipper-like mechanism, imposing a continuous reorganization of atoms on individual tube lattices within the adjacent tubes. Other topological defects induce the polymerization of tubes and creation of “Y”, “T” and “X” junctions. The latter results pave the way to the fabrication of nanotube contacts, nanocircuits and strong 3D composites using irradiation doses under annealing conditions.