Carbon nanotube fibers with martensite and austenite Fe residual catalyst: room temperature ferromagnetism and implications for CVD growth

Abstract

We report on carbon nanotube fibers with stabilized room temperature ferromagnetic martensite and austenite residual Fe catalyst.

Surface Chemistry Analysis of Carbon Nanotube Fibers by X‐Ray Photoelectron Spectroscopy

“…Higher magnification images confirm that the CNTs are highly regular, as seen in the HRTEM micrograph example in Figure b, shown as perfectly aligned walls in the CNT and (hk0) reflections in the fast Fourier transform. However, some areas of the CNTs and bundles are coated by a carbonaceous layer (Figure c) and in addition to the CNTs, there is around 7 wt.% of residual encapsulated catalyst, typically in poorly‐graphitized tubules (Figure d).…”

“…Most of this carbonaceous layer is volatile and can be desorbed below 400 C. Thus, annealing of CNT fiber in UHV, more conveniently inside the XPS probing chamber, is expected to remove these impurities, as well as adventitious carbon and water molecules physically adsorbed on the CNT surface. Similarly, scanning photoelectron microscopy, which has a Figure 2c) and in addition to the CNTs, there is around 7 wt.% of residual encapsulated catalyst, [30] typically in poorly-graphitized tubules (Figure 2d). We identify the corresponding surfaces under analysis as: asmade, annealed and annealed bundle ( Table 2).…”

Engineering of oriented carbon nanotubes in composite materials

“…This work shows that adjustment of the size and shape of the catalyst nanoparticle can control the CNT ferromagnetism behavior. This phenomenon can be effective in developing the method [ 111 ].…”

Magnetocrystalline effects on the subsurface hydrogen diffusion in γ-Fe(0 0 1)

“…Alloying elements can alter the magnetic ground state and the critical temperature of γ-Fe, since Ni is ferromagnetic below TC = 631 K [10], whereas α-Mn adopts a complex non-collinear antiferromagnetic phase below TN = 95 K [11]. The magnetic properties are of paramount importance in magnetoelectronics [12][13][14][15] and biomedicine [16][17][18][19], and also in steel components close to the D-T plasma of magnetically-confined fusion reactors [20][21][22]. Three magnetically ordered phases are considered in the collinear approximation used in theoretical studies: the ferromagnetic (FM-↑↑↑↑ ...) phase, as well as multi-layered anti-ferromagnetic phases, namely the single (AFM1-↑↓↑↓ ...) and double (AFMD-↑↑↓↓ ...) layer phases [23][24][25][26].…”