Experimental Analysis and Power Law Model of Multiwall Carbon Nanotubes Yield on Fe-Co-Ni Ternary Metal Catalyst

Abstract

This article presents the synthesis of multi wall carbon nanotubes (MWCNTs) via chemical vapour deposition (CVD) method. The CVD technique is widely used due to high throughput of CNTs as compared to laser ablation (LA) and arc discharge techniques (ADT). The ternary transition metal catalyst used for CNTs synthesis. The use of ternary metal catalyst provided favorable conditions for high yield and high quality CNTs as against binary of singular metal catalyst. The ternary metal catalyst Fe-Co-Ni with 3%, 5%, 7% and 10% loadings on the CaCO3 substrate prepared by the wet impregnation method. The active range of temperature for the CNTs synthesis was kept between 600°C to 750°C with a temperature step of 50°C. The acetylene (C2H2) gas is used as an active carbon source and argon gas as carrier element. The time of deposition kept in all the experimental evaluation is 30 minutes with the mass flow rate of carbon bearing gas at 60 ml/min. The maximum carbon deposits 0.786 gm obtained is with 10% metal catalyst at 700°C reaction temperature and it decreases thereafter. The experimental results obtained with variable temperature are then modelled with analytical models. The power law model and the third-degree polynomial model used to predict the CNTs yield for the variable temperature. The power law model predicts the modelled CNTs mass is well below the 10% error for all the input conditions, whereas the third-degree polynomial model deviates considerably from the experimental CNTs deposits. The purity of the carbon deposit is tested with Raman analysis and ID/IG ratio obtained for as synthesized CNTs is 1.31. The SEM imaging shows bundles of CNTs present after three stage purification.

Keywords: Carbon Nanotubes; Catalyst; Synthesis; Scanning Electron Microscopy