Hydrogen-induced Ostwald ripening of cobalt nanoparticles on carbon nanotubes
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Nanoparticles on carbon nanotubes can be used as a high surface area catalyst or as a means to produce well-defined particles. In this study, cobalt nanoparticles were formed on xxsingle-walled carbon nanotubes during hydrogen exposure at an elevated temperature. The average particle size increased as a function of reaction time ranging from 1.5 to 40 nm, indicating hydrogen-induced Ostwald ripening which is remarkable for a nonhydrogen-absorbing material. Mass abundances and cobalt shells were observed which possibly contained hydrogen. The combination of large surface area, high atomic mobility, and hydrogen-induced Ostwald ripening resulted in a novel method to prepare various cobalt nanoparticle shapes and sizes.
KeywordsCobalt Nanoparticle Hydrogen Carbon nanotube, magic number Ostwald ripening Nanocomposites
The authors thank the National Science Foundation (NSF CBET-0828771) and AFOSR MURI (FA9550-08-1-0309) for financial support. Electron microscopy on the T20 was accomplished at the Electron Microscopy Center for Materials Research at Argonne National Laboratory, the U.S. Department of Energy Office of Science Laboratory operated under Contract No. DE-AC02-06CH11357 by UChicago Argonne, LLC. TEM assistance by R. E. Cook is appreciated by the authors.
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