title: Methane-assisted chemical vapor deposition yielding millimeter-tall single-wall carbon nanotubes of smaller diameter.
abstract: We examined the use of low purity H2 (96 vol % H2 with 4 vol % CH4) in chemical vapor deposition (CVD) using a C2H2 feedstock, and obtained vertically aligned single-wall carbon nanotubes (VA-SWCNTs) with unexpectedly smaller diameters, larger height, and higher quality compared with those grown using pure H2. During the catalyst annealing, carbon deposited at a small amount from CH4 on the Fe particles, which kept them small and dense. During CVD, CH4 prevented the Fe particles from coarsening, resulting in an enhanced growth lifetime and suppressed diameter increase of growing SWCNTs. These effects were observed only for CH4, and not for C2H4 or C2H2. CH4-assisted CVD is an efficient and practical method that uses H2 containing CH4 that is available as a byproduct in chemical factories.
authors.affiliation: Department of Chemical System Engineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Zhongming
authors.initials: Z
authors.lastname: Chen
authors.forename: Dong Young
authors.initials: DY
authors.lastname: Kim
authors.forename: Kei
authors.initials: K
authors.lastname: Hasegawa
authors.forename: Suguru
authors.initials: S
authors.lastname: Noda