Multi-walled carbon nanotubes have been synthesized through the solid-phase transformation
of metal-containing glass-like carbon nanoparticles by heating at temperatures
of 800–1000 _C. From microscopic observations on the morphologies and structures of
the nanotubes and various intermediate objects, it is shown that the transformation occurs
by nanoparticles first assembling into wire-like nanostructures, and then transforming into
nanotubes via particle–particle coalescence and structural crystallization