The Growth of Carbon Nanotubes via Chemical Vapor Deposition Method; its Purification and Functionalization

Objectives: The main motive behind proposed work is to enhance the solubility of CNTs in aqueous medium and in various other solvents. Purification and functionalization helped in accomplishing aforementioned task. Methods/Statistical Analysis: Initially, CNTs were grown by Chemical Vapor Deposition method. Nickel metal catalyst solution was prepared and loaded onto SiO2 wafer, which is kept in vacuum assisted quartz tube. Acetylene was used as a hydrocarbon source and at 750 oC it decomposes at nickel metal surface resulting in growth of Carbon Nanotubes. Several characterizations such as SEM, EDX, XRD and FTIR were performed for confirmation of CVD grown CNTs. SEM confirms the formation of tubular structure i.e. carbon nanotube and EDX illustrates the presence of carbon and metal catalytic impurities. Findings: Such impurities restrict their use in physical, chemical, biological and environmental systems, thus purification is required. Among all purification methods, acid treatment suits best for removal of metallic impurities. An acid mixture of H2SO4 and HNO3 in ratio of 3:1 was utilized to remove the impurities present. These acid purified CNTs now contain carboxylic acid groups attached over defects, sidewalls and at ends. However another major shortcoming of CNTs is their insolubility in various liquids and polymers. Improvements: Therefore, to improve the solubility and to allow bonding with polymer matrix, amide functionalization was carried out. By the effect of thionyl chloride, the -OH bond was replaced by –Cl group, which was further replaced by -NH moiety. Characterizations were carried out at each step of CNT processing. Moreover, these functionalized CNTs encourages us to extend the present work to quantify the effect of as grown and f-CNT on the average static and dynamic mechanical properties of CNT/epoxy nanocomposites in future.