The influence of a variety of supported catalyst combinations, Fe/Al2O3, Co/Al2O3, Ni/Al2O3, Fe/MnO, Co/MnO, and Ni/MnO, on the growth morphology of carbon nanotubes (CNTs) on aluminum foils is studied. CNT arrays are synthesized by thermal CVD at 645 °C using acetylene as the precursor. The morphology and distribution of the synthesized CNT arrays are analyzed by scanning electron microscopy (SEM). The chemical constitution of each combined catalyst is determined by performing X-ray diffraction (XRD) investigations on the decomposed and reduced catalysts. Thermodynamic calculations are performed to understand the correlation between the chemical state of the catalyst particles on the substrate and the morphology of the resulting nanotube arrays.