Jia Chee Tee

A review of purification techniques for carbon nanotubes

Purification of carbon nanotubes (CNTs) is a very actively discussed topic in contemporary CNT literature. To a large extent, impurities embedded in CNTs influence the physical and chemical characteristics of the CNTs. Different purification methods yield different CNT characteristics and may be suitable for the production of different types of CNTs. Developments in the purification methods of CNTs are reviewed, and the production methods are briefly discussed and summarized. This is followed by a detailed description of the three major purification methods, viz. chemical, physical, and multi-step purification.

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

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. ...

Template Synthesis of Carbon Nanotubules

The template synthesis of carbon nanostructures formed in porous anodic aluminium oxide (AAO) template with a pore size of 200 nm by a liquid phase impregnation of the template with a polymer, polyfurfuryl alcohol, followed by carbonization is studied. The temperatures of exposure to furfuryl alcohol vapour were varied between 50 and 70° C. The resultant carbon nanotubules formed were hollow with open ends having diameter ranging from 220–300 nm which is in agreement with the pore size of the template used. The BET surface area was found to increase from 11.64 m2/g before pyrolysis to 90.19 m2/g after pyrolysis as a result of the formation of carbon nanotubules.