Preparation of aligned carbon nanotubes with prescribed dimensions: Template synthesis and sonication cutting approach

Aligned multiwalled carbon nanotubes (CNTs) with good crystallinity have been obtained by cutting the CNTs grown on an anodic aluminum oxide (AAO) template by a sonication method. AAO templates were fabricated by two-step anodization of Al. After the cobalt catalyst had been electrochemically deposited at the bottom of the pores in the AAO template, CNTs were grown in a gas mixture Of 10% C2H2 and 20% H-2 in an Ar carrier gas at 650 degreesC. After the 40 min growth, CNTs grew out of pores up to 10 mum with a wide length distribution. Sonication of CNTs on the AAO template in an acetone solution cut the overgrown CNTs effectively, resulting in short multiwalled CNTs on the AAO template. We obtained CNTs with a narrow length distribution by etching the AAO template away. The formation mechanism of these cut CNTs is discussed along with their potential applications.