Millimeter-tall carbon nanotube arrays grown on aluminum substrates

Millimeter-tall vertically aligned carbon nanotubes (VA-CNTs) were grown directly on Al substrates. Atmospheric pressure chemical vapor deposition is performed at 600 degrees C, which is well below the melting point of Al (660 degrees C), using Fe catalyst and C2H2 as a highly reactive carbon feedstock. The CNT height was sensitive to the C2H2 concentration and 0.06 vol% was optimum for balanced growth rate and catalyst lifetime, yielding 0.06 mm-tall VA-CNTs in 2 h. The CO2 addition at 1.8 vol% to the C2H2/Ar gas significantly enhanced the CNT growth, yielding 1.1 mm-tall VA-CNTs in 12 h. CO2 shows this remarkable effect when added in large excess to C2H2, differently from the well-known method of "small addition of water." Moreover, the resulting VA-CNTs showed electrical contact with the Al sheets with resistance of <0.7 Omega cm(-2). The effect of CO2 is systematically studied and discussed. (c) 2018 Elsevier Ltd. All rights reserved.