Search

The stabilization of γ-Fe inside carbon nanotubes (CNTs) and its magnetic-coupling with α-Fe or Fe 3 C has attracted a great interest for the possible control of the hysteresis-loss processes in magnetic hyperthermia. Being interested in exploring further the stabilization-dynamics of this phase (γ-Fe), we have performed novel investigations on the fabrication and manipulation of filled CNTs films (buckypapers) with major focus on the effects of vapour-flow- and cooling-rate synthesis-parameters. X-ray diffractograms (XRD) and Rietveld refinements evidence an unusual stabilization of γ-Fe upon cooling, with a maximum relative abundance of 26 % after a slow-cooling step of 30 min. In-situ post-growth manipulation of the CNT-structure, in presence of tris(tetramethylcyclopentadienyl)‑gadolinium (III), allows for a particularly efficient functionalization of the CNT-walls, with in-situ surface-deposition of an amorphous Gd-phase. The rapid-cooling approach employed in the post-growth Gd-functionalization-step is found to have beneficial effects on the γ-Fe stabilization, with an enhanced relative abundance of 30 %, as extracted from Rietveld refinements. Extended characterization through magnetometry, evidence a dependence of the coercive-field value on both cooling and flow-rate parameters. The reported dataset confirms the existence of a magnetic-coupling within the encapsulated nanocrystals, with the unit-cell-volume being in the order of 45.9 Å3. [Display omitted] • We report a novel investigation on the fabrication and manipulation of filled CNTs. • New insights on the effects of flow- and cooling-rate CVD-parameters are presented. • We show an unusual stabilization of γ-Fe upon-cooling. • Tris(tetramethylcyclopentadienyl)Gd(III) was employed for the CNT-functionalization. • A dependence of the coercive-field value on both cooling and flow-rate is shown. [ABSTRACT FROM AUTHOR]

The appearance of coexisting ferromagnetic and superconductive phenomena in graphite‑sulfur and amorphous carbon‑sulfur composites has recently attracted an important attention. In this work we propose a novel re-investigation of the carbon‑sulfur doping mechanism performed by employing carbon nanotube networks (cm-scale buckypapers) and graphene-oxide films as host-materials. In the buckypaper-case, the presence of multiple sulfidation processes involving formation of 1) carbon‑sulfur and 2) metal-sulfide phases was demonstrated. Presence of carbon‑sulfur bonding was identified by employing both Raman spectroscopy and X-ray photoelectron spectroscopy. The conductive and magnetic properties of the sulfur-rich areas within the buckypaper were also investigated. An enhanced carbon‑sulfur bonding was then identified in sulfur-doped graphene-oxide films. In this latter case we demonstrate an almost complete annihilation of ferromagnetic-signals. ESR-spectroscopy of this second-type of system revealed the appearance of a paramagnetic transition for g ~ 2.08 at T ~ 77 K, possibly originating from the carbon‑sulfur bonding. A weak enhancement in the diamagnetic component could be interestingly detected below T ~ 60 K as a consequence of sulfur doping, after subtraction of the percolative ferromagnetic signals. [Display omitted] • We investigate carbon-sulfur doping by employing CNT- networks and graphene-oxide as host-materials. • In the buckypaper-case, formation of carbon-sulfur and metal-sulfide phases was demonstrated. • The conductive and magnetic properties of the sulfur-rich areas were investigated. • Carbon-sulfur bonding was identified also in sulfur-doped graphene-oxide films • Annihilation of ferromagnetic-signals is demonstrated, with appearance of a paramagnetic transition for g~2.08 (T~77K) • A weak enhancement in the diamagnetic component could be interestingly detected below T ~ 60K [ABSTRACT FROM AUTHOR]