Iron Catalysts for the Growth of Carbon Nanofibers: Fe, Fe3C or Both?

He et al. Chem. Mater. 2011, 23, 5379−5387

铁催化长出来的管子是直的

碳化铁催化长出来的管子是竹节状的

有意思。。。

Iron is a widely used catalyst for the growth of carbon nanotubes (CNTs) or carbon nanofibers (CNFs) by catalytic chemical vapor deposition. However, both Fe and Fe–C compounds (generally, Fe₃C) have been found to catalyze the growth of CNTs/CNFs, and a comparison study of their respective catalytic activities is still missing. Furthermore, the control of the crystal structure of iron-based catalysts, that is α-Fe or Fe₃C, is still a challenge, which not only obscures our understanding of the growth mechanisms of CNTs/CNFs, but also complicates subsequent procedures, such as the removal of catalysts for better industrial applications. Here, we show a partial control of the phase of iron catalysts (α-Fe or Fe₃C), obtained by varying the growth temperatures during the synthesis of carbon-based nanofibers/nanotubes in a plasma-enhanced chemical vapor deposition reactor. We also show that the structure of CNFs originating from Fe₃C is bamboo-type, while that of CNFs originating from Fe is not. Moreover, we directly compare the growth rates of carbon-based nanofibers/nanotubes during the same experiments and find that CNFs/CNTs grown by α-Fe nanoparticles are longer than CNFs grown from Fe₃C nanoparticles. The influence of the type of catalyst on the growth of CNFs is analyzed and the corresponding possible growth mechanisms, based on the different phases of the catalysts, are discussed.

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