Carbon nanotube growth from alkali metal salt nanoparticles

Abstract

We demonstrate that alkali metal salts, including KCl, NaCl, K2SO4, Na2SO4, K2CO3, and Na2CO3, can act as catalysts for carbon nanotube (CNT) growth in chemical vapor deposition (CVD). The solution of alkali metal salt, water and ethanol was nebulized and was introduced into the CVD reactor, producing CNT with a multi-walled structure. Individual CNT are terminated with an onion-shaped carbon tip even when different alkali metal salt catalysts are used. Through observation and analysis of the catalyst particles and the resulting product, we elucidate the mechanism by which the alkali metal salt nanoparticles are served as “seeds” and provide nucleation sites for CNT growth. The ethanol decomposes to release carbon atoms into the catalyst particles, and the carbon nucleates and then begins to assemble on the surface of the catalyst particles, resulting in the CNT growth. By altering growth conditions, branched CNT and single-walled CNT also can be grown on alkali metal salt nanoparticles.