Synthesis and characterization of ultra-small magnetic FeNi/G and NiCo/G nanoparticles

Abstract

Ultra-small magnetic nanoparticles consisting of NiCo and FeNi alloys enclosed within graphitic shells (NiCo/G and FeNi/G) have been synthesized. The particles, which retained the face centered cubic (fcc) symmetry of the original bulk metals, together with the graphitic coating were characterized by means of aberration corrected scanning transmission electron microscopy (STEM), obtaining mean particle sizes of 2.6 nm and 6.2 nm for NiCo/G and FeNi/G, respectively. Due to the enhancement of the thermal stability by the graphite shell, the graphite coated FeNi and NiCo were stable under oxygen atmosphere up to 170 °C. The effectiveness of the graphite shell was confirmed when unprotected bimetallic FeNi and NiCo were prepared and chemical characterization revealed that more than 60 at.% of the samples was oxygen due to the massive oxidation of the bimetallic nanoparticles.

Enhanced purification of carbon nanotubes by microwave and chlorine cleaning procedures

“…5). Upon microwave treatment the zero valent iron is decreased to only 4% and the residue is mostly a mixture of Fe 2+ and Fe 3+ , [31][32][33] which is the relative composition (Fe…”

Quantum phase transition and Fermi liquid behavior inPd1−xNixnanoalloys

“…These observations indicate the presence o f m agnetic nanoparticles w ith size and shape dispersions, as also evidenced by the H RTEM im ages, in all the sam ples [40]. Broadly speaking, the system is in a blocked ferrom agnetic (FM ) state below Tirr, is in a superparam agnetic (SPM ) state up to the tem perature Tc beyond w hich the tem perature dependence o f m agnetization curve (M -T curve) starts obeying the C urie-W eiss law, and then even the individual SPM particles becom e param agnetic (PM ) [40,41], Tc s in the present study have been determ ined sim ply by finding the low est tem perature to w hich the high-71 part o f the M -T curve fits w ell w ith a C urie-W eiss law. The FC or ZFC curves for all the sam ples, however, do not show a distinct inverse tem perature dependence betw een Tirr and Tc ; they quite apparently have a pow er-law tem peraturedependence com ponent, akin to ferrom agnetism , as well.…”

Nitrogen-doped, FeNi alloy nanoparticle-decorated graphene as an efficient and stable electrode for electrochemical supercapacitors in acid medium

“…Figure 1a displays the XRD spectra of the anchoring FeNi alloy nanoparticles (NPs) on graphene sheets after the calcination process. The broad diffraction peak observed at 2θ = 22.2°to 26.8°indicates the disordered stacking of graphene sheets; however, three distinctive diffraction peaks at 2θ values of 43.8°, 51.1°, and 75.6°c orresponding to (111), (200), and (220) crystal planes, respectively, indicate the formation of FeNi alloy [34]. XPS spectra presented in Figure 1b confirm the successful doping with nitrogen contents up to 10.1%.…”