Single-Crystalline Permalloy Nanowires in Carbon Nanotubes:  Enhanced Encapsulation and Magnetization

Abstract

We report the use of dichlorobenzene as a carbon source to produce carbon nanotubes with thinner walls and a relatively large cavity, boosting the efficiency of metal encapsulation inside nanotubes. As an example, we show that Permalloy (FeNi) was encapsulated in nanotubes in the form of long nanowires and reached more than 30 wt % of the final product. These Permalloy nanowires are single crystalline, with a typical length of several micrometers and an aspect ratio of >100, and sheathed by several graphene layers. Such Permalloy nanowires show much-enhanced magnetization and microwave absorption properties, compared with Fe or FeNi nanowires produced by the source materials without adding Cl. The improved magnetic properties are due to a more efficient in situ encapsulation of Permalloy and a lesser number of nanotube walls coated on the surface of nanowires.

Structural and magnetic characterization of batch-fabricated nickel encapsulated multi-walled carbon nanotubes

“…The formation and filling of CNTs can also occur simultaneously through the pyrolysis of aerosols of organometallic compounds; metallocenes can serve as a source of both the carbon shell and the magnetic core [13]. However, pyrolysis of aerosols leads to a partial and discontinuous filling of the CNTs [14]. A more convenient method of producing magnetic carbon-based shells is by the template-assisted chemical vapor deposition (CVD) [15].…”

Boundary layer chemical vapour synthesis of self-organised ferromagnetically filled radial-carbon-nanotube structures

“…C1 and C2 refers to the two species of graphitic carbon observed on the shell of the encapsulated nanocrystals (here referred to as 'nano-onions') and multiwall carbon nanotubes 15 . Fig.7 shows the hysteresis loop for a powder sample of the radial structures; the saturation 25 magnetization is 18.5 emu/g and the coercivity is 500 Oe at 5 K. The latter value is higher than those previously measured for counterpart structures produced by steady-state CVD using dichlorobeneze (90 Oe), trichlorobenzene (415 Oe), and benzene (214 Oe) precursors 33,37 . Similar comparisons of the saturation magnetisation value is difficult since the ferromagnetic oxide and diamagnetic MWCNT contributions are rarely considered.…”

“…This is surprising since Fe3C and Ni3C are considered essential intermediates for MWCNT growth [41][42][43][44][45][46][47][48][49][50] . Previous reports of this synthesis using conventional solid-and liquid-source CVD do not comment on the absence of Ni3C and Fe3C in the final product nor attempt to describe the growth mechanism [31][32][33][34][35][36][37][38] . The absence of Fe3C and Ni3C diffraction peaks in Fig.5 suggests that 45 there is direct formation of FeNi alloys without the intermediate metal carbide formation, or MWCNT growth is driven by the carbon supply from an unstable carbide that decomposes that high rate.…”

Synthesis, field emission and microwave absorption of carbon nanotubes filled with ferromagnetic nanowires

“…Both theoretical calculations [15] and experimental measurements [16] have demonstrated that the field-emission performance of CNTs depends sensitively on their tip structure, and particularly an open-ended CNT is superior to a cap-ended one. Therefore, in order to promote their practical applications in associated areas, it is crucial to develop a highly efficient and well-controlled method for the preparation of open-ended, thin-walled CNTs filled with long and continuous ferromagnetic nanowires.In this paper, we summarized our recent progress [17][18][19][20][21] in the synthesis of open-ended, thin-walled CNTs filled …”

“…In this paper, we summarized our recent progress [17][18][19][20][21] in the synthesis of open-ended, thin-walled CNTs filled…”