Flame synthesis of Ni-catalyzed nanofibers

Flame synthesis of Ni-catalyzed nanofibers is illustrated. Ni nanoparticles are formed by thermal decomposition of a nebulized Ni nitrate solution entrained into a reactive fuel mixture. Although at the earliest stages of growth, the Ni nanoparticles are sufficiently small to catalyze single-wall nanotubes (SWNTs). only the larger particles appear catalytically active yielding only nanofibers. Using different reactive gas mixtures consisting of CO or C2H2 or their combination, Ni nanoparticles exhibited a high preferential reactivity towards C2H2 to form nanofibers. These results are interpreted as a result of CO enhancing the dissociative adsorption of C2H2 through electronic charge donation mediated by the Ni nanoparticle and physically protecting active sites against blockage by aromatic molecules. (C) 2002 Elsevier Science Ltd. All rights reserved.