Structural transformations in carbon nanoparticles induced by electron irradiation

This paper reviews the electron-irradiation effects in graphitic nanoparticles. Irradiation-induced atomic displacements cause structural defects in graphite lattice forming the basis of carbon nanoparticles such as nanotubes or carbon onions. Defects of the type of non-six-membered rings induce topological alterations of graphene layers. The generation of curvature under electron irradiation leads to the formation of new structures, such as spherical carbon onions or coalescent nanotubes. At high temperatures, the self-compression of carbon onions can promote the nucleation of diamond cores or phase transformations of foreign materials that are encapsulated by onionlike graphitic shells. Under the nonequilibrium conditions of intense irradiation, the phase equilibrium between graphite and diamond can be reversed. It is shown that graphite can be transformed into diamond even if no external pressure is applied. All electron-irradiation and electron-microscopic studies described here were carried out using in situ transmission electron microscopy. (C) 2002 MAIK "Nauka / Interperiodica".