Hot Filament for In Situ Catalyst Supply in the Chemical Vapor Deposition Growth of Carbon Nanotubes

A simplified chemical vapor deposition (CVD) method is described for in situ synthesis of multiwalled carbon nanotubes. The synthesis apparatus is similar to that used to deposit CVD diamond. However, an Fe–Cr wire is selected and coiled as the filament to grow nanotubes. The tubes grow because the filament acts as both a heat source for pyrolysis, and a source of metal for the catalyst. The evaporated metal atoms can be considered to catalyze the growth of carbon nanotubes. The system has the potential to inexpensively synthesize large amounts of nanotubes continuously by combining physical and chemical vapor deposition.