Full factorial design approach to carbon nanotubes synthesis by CVD method in argon environment

Abstract

Whereas meeting product quantity and quality are prime intent in process optimization of materials manufacturing, the application of the more reliable full factorial experiment has not been well-explored in optimization studies of Carbon nanotubes (CNTs) synthesis. In this study, statistical full factorial design of experiment was explored in the parametric studies of CNTs synthesis via acetylene-chemical vapour deposition (CVD). Bimetallic (FeCo) catalyst supported on CaCO3 was employed for the synthesis of CNTs. The dependence of CNTs yield on the growth time (45/60 min), growth temperature (700/750 °C), acetylene flow rate (150/190 ml/min), and argon flow rate (230/290 ml/min) was investigated in the 24 factorial design of experiment. The growth temperature and acetylene flow rate were found to have the most significant effects on the yield of CNTs, and a maximum yield of 170% was obtained at growth conditions of 60 min, 700 °C, 190 ml/min acetylene flow rate, and 230 ml/min argon flow rate. Since acetylene undergoes polymerization or dissolution during non-catalyzed thermal decomposition, the significant effects of temperature and acetylene flow rate as illustrated by the factorial analysis suggests that the selective ability of the FeCo/CaCO3 catalyst towards CNTs growth in the thermal decomposition of acetylene in CVD was mainly thermodynamics-controlled. Characterization of CNTs samples synthesized at different conditions shows that highest-yield conditions do not guarantee best quality properties.