The effect of changes in catalyst temperature produced by direct plasma heating on the preparation of carbon nanotubes

The catalyst temperature was adjusted by changing the position of catalyst bed in the column reactor tube for the preparation of carbon nanotubes (CNTs) from methane using the microwave plasma technique. The maximum value of the carbon yield (80%) was obtained for a catalyst temperature of 794 K. CNTs grew at temperatures as low as 588 K with this method. CNTs prepared at temperatures above 794 K were cylindrical and that of those prepared at 588 K were herringbone type.