Effect of using chlorine-containing precursors in the synthesis of FeNi-filled carbon nanotubes

doi:10.1016/j.carbon.2007.03.032

Carbon

Volume 45, Issue 7, June 2007, Pages 1433-1438

https://doi.org/10.1016/j.carbon.2007.03.032 Get rights and content

Abstract

A method for the in situ filling of thin-walled carbon nanotubes (CNTs) with long continuous ferromagnetic nanowires is described, using chlorine substituted benzene, C₆H_6−xCl_x (x = 0–3), as the carbon precursor. This method can be used to prepare not only single-metal (e.g. Fe, Co, Ni) nanowires, but also alloy (e.g. FeNi) nanowire-filled CNTs. As an example, we show the successful synthesis of FeNi-filled CNTs. A ratio d_in/W is used to evaluate quantitatively the hollow degree of CNTs, where d_in is the inner diameter and W is the wall thickness of a nanotube. The larger this ratio is, the wider inner cavity of the CNTs will be. Statistical results show that the hollow degrees of CNTs increase with the increase of Cl content in carbon precursors, which in turn affords a convenient way to control the hollow degrees of CNTs.

Introduction

Carbon nanotubes (CNTs) filled with ferromagnetic materials have attracted considerable attention due to their fundamental interests and potential applications, for example in electromagnetic wave absorption [1], magnetic data storage devices [2], human tumor therapy [3] and sensors for magnetic force microscopy [4], etc. In these new types of metal-filled nanostructures, CNTs can provide effective protection against the oxidation of the encapsulated metal. Therefore, they can be used as high-temperature magnetic materials [5]. Several methods have been proposed to prepare metal-filled CNTs, such as template-assisted method [1], powder pyrolysis method [2], [3] and spray pyrolysis method [6], [7], [8], etc. Despite of the great progresses, many of these methods still suffer from various drawbacks such as complicated procedure [1] and poor growth control of metal-filled CNTs [2], [3]. In addition, the efficiency of encapsulation of metal into nanotubes of previous reports seems very low. This can be seen from two facts: (1) most of the encapsulated metals exist as particles or short rods (length < 500 nm) and distribute periodically far away from the next one along the nanotube [6], [7], [8], and (2) the wall thicknesses of nanotubes are very thick [7]. Such low filling efficiency limits the production of large amount of nanowires with high aspect ratio for practical applications. So it is crucial to develop an easy, high-efficiency and well-controlled method to prepare metal-filled CNTs.

Previous work of our group has shown that the use of chlorobenzene can facilitate the growth of CNTs with large inner cavity [9]. In this work, we systematically investigate the effect of different chlorine-contained benzenes, C₆H_6−xCl_x (x = 0–3), on the microstructures of FeNi-filled CNTs (FeNi@CNTs). To the best of our knowledge, the effect of different chlorine-contained carbon precursors on the growth of FeNi-filled CNTs has never been reported before.

Section snippets

Experimental

The experimental setup and procedure are similar to that described in our previous report about aligned CNTs [8], but we use C₆H_6−xCl_x (x = 0–3) rather than xylene as carbon precursor. About the same amounts of ferrocene and nickelocene powders were dissolved in 10 ml C₆H_6−xCl_x (x = 0–3) to form solutions with concentration of 0.06 g/ml, and fed into CVD furnace by a syringe pump at a constant rate of 0.12 ml/min for 30 min. A mixture of Ar and H₂ was flowing through the system at 2000 and 300 sccm,

Results and discussion

Fig. 1 are the SEM images of as-grown products with different carbon precursors. It can be seen from Fig. 1a and b that the products prepared with benzene (BEN, x = 0) and chlorobenzene (CB, x = 1) are dominant CNTs with very few amorphous carbon; while when dichlorobenzene (DCB, x = 2) and trichlorobenzene (TCB, x = 3) are used as carbon precursors, the surfaces of CNTs are very clean and free of impurity particles (see Fig. 1c and d). The XRD patterns of as-grown products with different carbon

Conclusions

In summary, we described a simple method (introducing Cl in the carbon precursor) for the first time to produce micrometer-long and continuous permalloy (FeNi) nanowires inside thin-walled CNTs. FeNi content of as-obtained samples increases in the order of BEN (x = 0) < CB (x = 1) < DCB (x = 2) < TCB (x = 3). Cl can combine with reactive hydrogen and thus provide a C-rich and H-deficient condition to favor the formation of sp²-like graphitic structures, which are favorable to the formation of thin-walled

Acknowledgements

The authors are grateful to the financial support from National Natural Science Foundation of China (Grant No. 50572047). This project was also partly supported by National Center for Nanoscience and Technology, China.

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Effect of using chlorine-containing precursors in the synthesis of FeNi-filled carbon nanotubes

Abstract

Introduction

Section snippets

Experimental

Results and discussion

Conclusions

Acknowledgements

Solid State Sci

J Magn Magn Mater

Chem Phys Lett

Microwave absorption enhancement and complex permittivity and permeability of Fe encapsulated within carbon nanotubes

Adv Mater

Magnetic force microscopy sensors using iron-filled carbon nanotubes

J Appl Phys