A gas-phase, one-step method for producing various aerosol carbon nanostructures is described. The carbon nanostructures can be selectively tailored with either straight, coiled, or sea urchin-like structures by controlling the size of Ni-Al bimetallic nanoparticles and the reaction temperature. The carbon nanostructures were grown using both conventional spray pyrolysis and thermal chemical vapor deposition. Bimetallic nanoparticles with catalytic Ni (guest) and non-catalytic Al (host) matrix were reacted with acetylene and hydrogen gases. At the processing temperature range of 650-800 degrees C, high concentration straight carbon nanotubes (S-CNTs) with a small amount of coiled carbon nanotubes (C-CNTs) can be grown on the surface of seeded bimetallic nanoparticle size <100 nm, resulting from consumption of the melting Al matrix sites; sea urchin-like carbon nanotubes (SU-CNTs) of small diameter (similar to 10 +/- 4 nm) can be grown on the bimetallic nanoparticle size >100 nm, resulting from the significant size reduction of the available Ni sites due to thermal expansion of molten Al matrix sites without consumption of Al matrix. However, at the processing temperature range of 500-650 degrees C, C-CNTs can be grown on the bimetallic nanoparticle size <100 nm due to the presence of Al matrix in the bimetallic nanoparticles; SU-CNTs of large diameter (similar to 60 +/- 13 nm) can also be grown on the bimetallic nanoparticle size >100 nm due to the isolation of Ni sites in the Al matrix. (C) 2011 Elsevier Inc. All rights reserved.