硫辅助填充高压Fe5C2/Fe7C3单晶相的碳纳米管研究

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

摘要:

硫可以用作生长促进剂制备具有不同形态的碳纳米结构, 例如: Y型和海胆状结构, 单壁碳纳米管(SWCNTs), 双壁碳纳米管薄膜等. 此外, 研究表明低浓度的硫和低气体流量可实现碳纳米管中高压Fe7C3和Fe5C2相晶体的填充. 然而, 碳纳米管中高压相的填充条件以及连续垂直取向的碳纳米管薄膜的合成和形貌控制的条件尚需进一步研究. 本文采用化学气相沉积(CVD),使用硫和二茂铁的混合物作为生长促进剂和碳源, 在氩(Ar)气环境中将Si/SiO2基底作为局部生长区域, 实现了在碳纳米管内填充碳化铁相, 并通过对所得碳结构进行详细表征, 揭示填充的碳化物相(Fe5C2和Fe7C3)之间可能存在结合, 这些结果在磁数据存储方面将有潜在应用.

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.