Highly ordered carbon nanotubes based on porous aluminum oxide: fabrication and mechanism

Highly ordered carbon nanotubes (CNTs) are wildly pursued due to their unique properties. Anodic aluminum oxide (AAO) exhibits great possibility for this purpose. Here, CNTs based on AAO template were produced using acetylene or ethylene as the hydrocarbon sources with or without the presence of Co catalysts. CNTs grown on the Co-embedded AAO samples were normally confined within the nanopores of the AAO template. It was found that C2H4 normally requires 100 degrees C higher pyrolysis temperature than C2H2 under otherwise identical conditions. The pyrolysis temperature is greatly reduced with the presence of Co catalysts. CNTs can grow out of the nanopores, if Co particles are present at the bottom of the nanopores and if the nanopores are short in length or large in diameter. The graphitization of AAO template grown CNTs was studied by Raman spectroscopy. The CNTs produced from ethylene are generally better in graphitization than those from acetylene, and the CNTs grown with the presence of Co catalysts deposited at the bottom of nanopores are better than those without Co catalysts or with Co catalysts coated on the entire inner wall of nanopores. The growth temperature is found not to play a critical role in graphitization.