Ultra-long carbon nanotube forest via in situ supplements of iron and aluminum vapor sources

A carbon nanotube forest with a length of 14 cm grew with an average growth rate of 1.5 mu m s(-1) and a growth lifetime of 26 h. Several key factors to realize this unprecedented long growth such as catalyst conditions, growth conditions in chemical vapor deposition, and reactor system were clarified. It was found that the combination of the catalyst system of iron/gadolinium/aluminum oxide (Fe/Gd/Al2Ox) and the in situ supplements of Fe and Al vapor sources at very low concentration was crucially important. A cold-gas system, where only the substrate is heated while keeping the gas at room temperature, was employed to suppress unnecessary reactions and depositions. The long carbon nanotube forest enabled macroscopic measurements of the tensile and electrical properties of the carbon nanotube wires, and it gave several important insights for industrial applications of the carbon nanotubes in the future. (C) 2020 Elsevier Ltd. All rights reserved.