A process of making carbon nanotubes comprising the steps of: providing a precursor composition comprising at least one metallic compound and at least one organic compound; wherein the organic compound is selected from the group consisting of an ethynyl compound, a metal-ethynyl complex, and combinations thereof; wherein the precursor composition is a liquid or solid at room temperature; and heating the precursor composition under conditions effective to produce carbon nanotubes. A carbon nanotube composition comprising carbon nanotubes and a metal component selected from the group consisting of metal nanoparticles and elemental metal; wherein the carbon nanotube composition is rigid.