Effect of Reaction Temperature and Flow Rate of Precursor on Formation of Multi-Walled Carbon Nanotubes

Abstract

The effect of reaction temperature and flow rate of precursor on the quantity and quality of the multi‐walled carbon nanotubes (MWNTs) produced by catalytic chemical vapour deposition (CCVD) was studied. The MWNTs were grown over zeolite supported catalyst at 700 and 850° C with flow rate of acetylene at 15 and 30 sccm. The effect of an in‐situ heat treatment on the as‐grown MWNTs at 200° C was investigated. Thermogravimetric analysis (TGA) results show that CNT purity decreases with increasing reaction temperture, from 63.31 wt% at 700° C to 61.68 wt% at 850° C. However, the increase of acetylene flow rate from 15 sccm to 30 sccm has improved the yield of MWNT yield from 63.31 wt% to 69.28 wt%. The MWNTs grown at 850° C with 30 sccm of acetylene show 68.23 wt% of purity, attributed to the higher acetylene flow rate. The in‐situ heat treatment at 200° C gave the highest purity of MWNTs at 87.52 wt%. TEM and HRTEM images suggest that the impurities on the wall layers of MWNT yield were burn off at 200° C. ...