Catalytic growth of carbon nanoballs with and without cobalt encapsulation

Carbon nanoballs encapsulated with cobalt were prepared by decomposition of methane. After acid treatment, the encapsulated cobalt can be removed to p roduce hollow carbon nanoballs. The content of hollow carbon nanoballs as h igh as 90 vol% in acid-treated carbon product can be obtained by increasing the content of cobalt from 50 to 75 mol% in the catalysts. However, under the same catalytic conditions, the main carbon products are multi walled ca rbon tubes (MWNTs) over Co/Al2O3, Co/La2O3, Co/CeO2 and Ni/MgO catalysts by decomposition of CH4, Or by decomposition of CO over Co/MgO catalysts. The se carbon nanoballs encapsulated with cobalt are novel magnetic materials. (C) 2000 Elsevier Science B.V. All rights reserved.