Scopul nostru este sprijinirea şi promovarea cercetării ştiinţifice şi facilitarea comunicării între cercetătorii români din întreaga lume.
Autori: Sangyun Lim, Dragos Ciuparu, Yuan Chen, Lisa Pfefferle, and Gary L. Haller
Editorial: Journal of Physical Chemistry B, 108, p.20095 - 20, 2004.
Cobalt silicate was studied as a model catalyst to seek an understanding of why Co-MCM-41 catalyst is not active for single wall carbon nanotubes (SWNT) upon treatment at high temperature. Cobalt orthosilicate was formed during high-temperature pretreatment of Co-MCM-41 (at 900 C) in an oxidizing environment. Cobalt silicate did not produce any carbon species during the first reaction cycle because the high thermal stability of cobalt silicate did not result in sufficient metallic Co clusters responsible for carbon dissociation in CO disproportionation. With repeated reaction cycles, however, undesirable carbon species, i.e., amorphous carbon and graphite, were produced resulting from larger metallic cobalt clusters formed at the high reduction temperature and without the confinement and/or anchoring of the MCM-41 matrix. These relatively large clusters do not catalyze the growth of SWNT.
Cuvinte cheie: carbon nanotubes, Co catalysts