Method for preparation cobalt-doped carbon nanopowders and nanowires and their characterization by NMR and magnetometry methods

Abstract

A technology combining of the hydrocarbon vapor pyrolysis and the chemical vapor deposition process in a horizontal continuous reactor was elaborated. These powders were agglomerate nanocomposite elements with a core-shell structure doped with cobalt clusters. The combined radiofrequency resonant magnetometry and NMR studies were carried out on polymer composites containing carbon nanoparticles doped with magnetic cobalt clusters, commercial cobalt nanowires and cobalt micropowders synthesized by electroless technology. Magnetometry data show the increase of magnetic susceptibility of samples during their magnetization reversal. NMR studies employing additional magnetic video-pulse excitation enabled rapid evaluation of the magnetic phase composition and coercive properties of nanopowders produced through different hydrocarbon pyrolysis processes.

This is accompanied by the NMR spin-echo signal enhancement effects which are most strong for nanowires and are much weaker for micropowders and are small for nanopowders due to their superparamagnetic properties.