document: In contrast with polymers, which are typically synthesized in the liquid phase, SWNTs are produced through a variety of synthesis techniques that typically involve the reaction of a gaseous carbon feedstock to form the nanotubes on catalyst particles. MWNTs were first observed in arc discharge fullerene reactors [1,26]; this technique was later adapted to produce SWNTs [3]. Similarly, the fullerene production method of laser ablation [27] was adapted to produce SWNTs (∼1.4nm diameter) in larger quantities on metal catalyst particles [28–30]. A number of chemical vapor deposition (CVD) processes have been developed to grow SWNTs and MWNTs, all involving the reaction of a gaseous carbon compound as feedstock. These processes include fluidized bed [31], “carpet” growth of carbon nanotubes (CNTs) from catalyst particles embedded in a substrate [32–35] as shown in Fig. 3, and “catalytic gas flow CVD” [36,37]. One of the most effective, cheap, and scalable CVD techniques is the HiPco (high-pressure CO) process, which does not use pre-formed catalyst particles unlike most other CVD techniques [38].
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