Synthesis of cobalt and cobalt oxide filled carbon nanotubes

Abstract

Carbon nanotubes (CNT) are one of the most fascinating discoveries in 20th century which exhibits superior properties in mechanical , electrical, optical and thermal properties. CNT can be either semiconducting or metallic, based on its chirality. Electronic industry uses CNT as an active element in the fabrication of electrical circuit. CNT can also be used for spintronics applications. Spintronics has emerged as a new field where electron spin is used as a carrier of information instead of electron charge. Fe filled CNT are usually synthesized by pyrolysis of ferrocene, however this process is not known to yield good quality Ni and Co filled CNT. In the present work, the synthesis of cobalt-filled multi - walled carbon nanotubes has been achieved by the process of Chemical Vapor Deposition using pyrolysis of Cobaltocene. Here cobaltocene along with camphor was used as a precursor. This combination yields highly aligned forests of Co filled CNT with length of the forest upto a few 100 micro-meters. Synthesis of these filled tubes has been achieved by adjusting experimental parameters like sublimation temperature, pyrolysis temperature, argon flow rate and the amount of precursor. These samples have been characterized by Raman, X-ray diffraction and Scanning Electron Microscopy. The Raman spectroscopy shows well defined D and G bands with the Id/Ig ratio of 0.639 with the occurrence of 2D band as well. Magnetic measurement shows that it exhibit ferromagnetic behaviour with the coercive field of 660 Oe due the filling of cobalt inside the nanotube shell. These filled CNTs forests have been drop-cast on a glass substrate and preliminary electron transport measurements have also been reported here. The aligned forest of Co filled CNT have also been converted to Co oxides by suitable annealing and the sample thus formed has been characterized by SEM, XRD and Raman. These samples are relevant for battery material as well as for spintronic applications.