Encapsulation of high pressure Fe5C2/Fe7C3 single crystal phases inside few walled carbon nanotubes in presence of sulfur as growth promoter

Abstract:

Recent works have shown that sulfur can be considered as useful growth-promoter for the fabrication of carbon nanostructures with different types of morphologies, such as: Y-junctions, urchin-like structures, single wall CNTs (SWCNTs) strands, double-walled CNTs films, amorphous CNTs, and others. In addition, it has been shown that the encapsulation of high pressure Fe7C3 and Fe5C2 can be achieved in conditions involving the use of small concentrations of sulfur and very low vapour flow rates. However further investigations are necessary in order to understand not only the conditions of encapsulation of such high pressure phases inside CNTs but also the parameters necessary for their morphological control and fabrication in the form of continuous vertically aligned films, which could be of interest for magnetic data recording applications. In the attempt to address these missing points in this work we performed detailed investigations on the encapsulation of such unusual iron carbide phases inside CNTs by using sulfur/ferrocene mixtures as growth promoter and catalyst/hydrocarbon sources and smoot Si/SiO2 substrates as localized growth area in presence of laminar Ar-flow. The obtained CNTs structures were characterized by using SEM, TEM, HRTEM, XRD and VSM techniques. The results indicate the possible presence of junctions between the carbide phases encapsulated inside the CNTs, namely Fe5C2 and Fe7C3 which could be of interest for data recording applications.