Carbon nanotubes grown on nanostructured flake substrates are disclosed. The nanostructured flake substrates include a catalyst support layer and at least one catalyst layer. Carbon nanotubes grown on the nanostructured flake substrates can have very high aspect ratios. Further, the carbon nanotubes can be aligned on the nanostructured flake substrates. Through routine optimization, the nanostructured flake substrates may be used to produce single-wall, double-wall, or multi-wall carbon nanotubes of various lengths and diameters. The nanostructured flake substrates produce very high yields of carbon nanotubes per unit weight of substrate. Methods for making the nanostructured flake substrates and for using the nanostructured flake substrates in carbon nanotube synthesis are disclosed.