Numerical Study on the Effect of Insulator and Wire Mesh Toward Carbon Nanotubes Growth Region in Quasi Pyrolysis Chamber

Abstract

Flame synthesis is known to be a more energy- and time-efficient method for producing carbon nanotubes (CNTs) compared to other techniques. However, due to the presence of soot formation and highly oxidizing flame sheet in diffusion flame, synthesized CNT in flame suffers low growth rate and low CNT morphology quality. In this study, feasibility of utilising a quasi-pyrolysis chamber (QPC) with and without wire-mesh at the inlet, located on top of methane diffusion flame which separates the CNT growth region from the flame sheet was numerically simulated. Flame quenching effect by the wire-mesh at the inlet of QPC creating a pyrolysis condition within the chamber with methane flame formed outside the chamber, producing the required high temperature for CNT growth. Furthermore, application of insulator surrounding the flame was also numerically tested to evaluate its effect on temperature distribution within the QPC. The study found that the quasi-pyrolysis condition inside the chamber can be established without using wire-mesh only up to chamber with 12 mm diameter before oxygen starts to seep into the QPC and formed flame inside the chamber. Nevertheless, the temperature increase inside the QPC is minimal with removal of wire-mesh. Besides that, the addition of insulation surrounding the flame has significantly increased the predicted synthesized CNT length by 2.5 times. This is due to the increment of CO concentration more than 3 times inside QPC with application of insulator. Consequently, higher CO concentration helps to enhance the CNT growth region within the QPC from initially confined to the region near to the inlet of QPC, to all areas within the QPC. Hence, to ensure high energy efficiency and robustness, utilization of QPC with wire-mesh and insulator should be incorporated in the future development of practical CNT synthesis process in flame.

Keywords

• carbon nanotubes
• computational fluid dynamics
• flame synthesis
• insulator
• quasi-pyrolysis chamber