RT Journal Article
T1 Carbon nanotube fibers with martensite and austenite Fe residual catalyst: room temperature ferromagnetism and implications for CVD growth
A1 Aleman, A.
A1 Ranchal Sánchez, Rocío
A1 Reguero, Victor
A1 Mas, Bartolomé
A1 Vilatela, J. J.
AB We report on the room temperature ferromagnetic properties of continuous macroscopic fibers made up of carbon nanotubes grown by floating catalyst chemical vapor deposition. Their ferromagnetic behavior originates from the presence of residual catalyst nanoparticles: martensite with 0.77 wt% C content and FCC Fe. The first is intrinsically ferromagnetic, but the latter only due to severe lattice distortion as a consequence of C supersaturation. The stabilization of martensite and austenite occurs mainly because of the small diameter of the nanoparticles, in the range of 4-20 nm. This is smaller than the embryonic nucleus of the relevant equilibrium phases, but also implies that large C concentrations can build up in FCC Fe before C can be segregated as a stable graphitic nucleus. The room temperature remanence ranges from 10% to 25% and the coercivity from 55 to 300 Oe, depending on the choice of promoter for fiber synthesis (S or Se). Superparamagnetic behavior is only observed in S-grown samples on account of the smaller diameter of residual catalyst particles. The results of this work provide an explanation for the widespread observation of magnetic properties in oxide-free CNT samples produced by catalytic growth under a wide range of synthesis conditions.
PB Royal Soc. Chemistry
SN 2050-7526
YR 2017
FD 2017-06-14
LK https://hdl.handle.net/20.500.14352/18091
UL https://hdl.handle.net/20.500.14352/18091
LA eng
NO © Royal Soc. Chemistry.Generous financial support was provided by the European Union Seventh Framework Program under grant agreements 678565 (ERC-STEM), FP7-People-Marie Curie Action-CIG (2012-322129 MUFIN), by MINECO (MT2012-37552-C03-02, MAT2015-62584-ERC, MAT2015-66888-C3-3-R, RyC-2014-15115) and by CAM MAD2D project (S2013/MIT-3007).
NO Unión Europea. H2020
NO Unión Europea. FP7
NO Ministerio de Economía y Competitividad (MINECO)
NO Comunidad de Madrid
DS Docta Complutense
RD 8 may 2024