Novel catalyst particle production method for CVD growth of single- and double-walled carbon nanotubes

Chemical vapor deposition (CVD) is described as the most versatile method for the production of carbon nanotubes (CNTs). Typically metallic nanoparticle catalysts for the CNT synthesis by CVD are prepared by wet chemical routes [1], [2], [3], involving several intermediate stages, or by depositing thin metal film on substrates by sputtering [4] or evaporation [5]. Aerosol methods offer simple alternative for production and deposition of catalyst nanoparticles with controlled sizes. As an example, Sato et al. [6] have used size-selected Ni nanoparticles generated by laser ablation for the synthesis of diameter-controlled multiwalled CNTs by CVD. Similarly, Kohno et al. [7] used the same technique to create alloy particles for the synthesis of single-walled CNTs (SWNTs). Our group has recently reported on well size-controlled production of Fe and Ni aerosol catalyst particles using a resistively heated metal wire. Fe and Ni particles have been used successfully for the synthesis of SWNTs in the gas phase [8]. In our aerosol method, catalyst particles embedded in SWNTs were found to have a mean diameter from 1.4 to 2.0 nm depending on the growth conditions [9]. Furthermore, a method for the efficient homogeneous deposition of catalyst particles via thermophoretic forces was developed [10].