Magnesia and Magnesium Aluminate Catalyst Substrates for Carbon Nanotube Carpet Growth

Carbon nanotube (CNT) carpet growth behavior is systematically investigated on a pristine and ion beam-bombarded family of basic catalyst substrates: MgAl2O4 (100), MgAl2O4 (110), MgAl2O4 (111), and MgO (100). Interrelationships between physicochemical properties of catalyst substrates (composition, phase, basicity, and surface structure) and CNT carpet growth efficiency (catalyst lifetime and CNT growth rate) for a conventional feedstock (C2H4) and an industrial waste (a gaseous product mixture from Fischer–Tropsch synthesis, FTS-GP) as a feedstock are established. Growth on MgAl2O4 spinel substrates shows ion beam bombardment is effective in transforming “inactive” basic catalyst substrates to “active” substrates that support CNT carpet growth. For “active” catalyst substrates (MgO and ion beam-damaged MgAl2O4), growth efficiency of a supported catalyst exhibits high sensitivity to the type of feedstock. FTS-GP outperforms C2H4 as a feedstock in terms of growth efficiency and the ability of a supported catalyst to promote CNT carpet growth. Superior growth efficiency and CNT quality associated with FTS-GP is attributed to the unique composition of the feedstock that consists of a mixture of hydrocarbons (saturated and unsaturated), nitrogen, and unreacted synthesis gas.