Single-crystalline FeCo nanoparticle-filled carbon nanotubes: synthesis, structural characterization and magnetic properties

Abstract

In the present work, we demonstrate different synthesis procedures for filling carbon nanotubes (CNTs) with equimolar binary nanoparticles of the type Fe–Co. The CNTs act as templates for the encapsulation of magnetic nanoparticles and provide a protective shield against oxidation as well as prevent nanoparticle agglomeration. By variation of the reaction parameters, we were able to tailor the sample purity, degree of filling, the composition and size of the filling particles, and therefore, the magnetic properties. The samples were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), superconducting quantum interference device (SQUID) and thermogravimetric analysis (TGA). The Fe–Co-filled CNTs show significant enhancement in the coercive field as compared to the corresponding bulk material, which make them excellent candidates for several applications such as magnetic storage devices.

The effect of magneto-crystalline anisotropy on the properties of hard and soft magnetic ferrite nanoparticles

“…The increase of coercivity is mainly related to the increase of anisotropy. An increase of H c with increasing crystallite size has been reported for single-domain NPs [13,42].…”

Fe1-xNix Alloy Nanoparticles Encapsulated Inside Carbon Nanotubes: Controlled Synthesis, Structure and Magnetic Properties

“…Saturation magnetization M s measured at 5K for the annealed samples correlates well with M s calculated from Slater-Pauling curve for FeNi alloys of the same stoichiometry (~186.0 emu/g) [ 39 ]. Further, the magnetization data gives evidence for the importance of the annealing step, since the as-prepared samples exhibit M s significantly lower than the reported data for the bulk material of the same stoichiometry [ 32 ]. This may be attributed to the lower crystallinity of the MNPs for the as-prepared samples compared to the annealed samples, and the formation of a bulk-like ferromagnetic core and a shell composed of disordered moments [ 21 , 45 ].…”

“…This procedure reduces the iron content (i.e., the catalyst) to a very low level (<100 ppm) [ 29 , 30 , 31 ]. Previously, we reported the filling of CNTs with FeCo binary alloys by following two approaches of filling [ 32 ]. In this study, we adapted these approaches for the preparation of Fe 50 Ni 50 @CNT and Fe 67 Ni 33 @CNT samples.…”

Filled Carbon Nanotubes as Anode Materials for Lithium-Ion Batteries

“…Mostly, CNT of type PR-24-XT-HHT (Pyrograf Products, Inc., Cedarville OH, USA) have been used as templates. For introducing materials into the inner cavity of the CNT, mainly extensions of solution-based approaches reported in [38][39][40][41][42][43] have been applied [44,45]. This is illustrated by the example of Mn3O4@CNT which has been obtained by filling CNT with a manganese salt solution and a subsequent reducing step yielding homogeneously MnO-filled CNT (MnO@CNT) [4].…”