Carbon Deposition from Aromatic Solvents onto Active Intact 3d Metal Surface at Ambient Conditions

Abstract

The process of carbon deposition onto 3d metal surface immersed in aromatic solvents (benzene, toluene, xylene) at ambient conditions was studied for as-prepared magnetic nanoparticles (MNPs) and Fe-based films by thermal analysis, mass spectrometry, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, electron microscopy, and energy-dispersive X-ray spectroscopy. The mechanism of the deposition at the interface is likely the heterogeneous Scholl oxidation of the aromatic hydrocarbons, which is the cationic polymerization of the aryl rings. It results in the formation of polycyclic aromatic hydrocarbons (PAH) chemically bonded to the surface of a MNP or thin metallic film. The benzene rings in the polycyclic deposit do not maintain planar aligned structures and do not provide delocalization of the π-electrons in the zone structure. Contrary to the dense graphite layers, the polycyclic layers, although chemically bonded, are not attached tightly to the surface. Such "hairlike" structure of the carboneous deposit might be especially favorable for the applications that imply the enhanced interaction at the surfaces incorporated in the functional matrices (polymeric composites or biosensors). The aromatic chemical nature of the deposit provides strong interaction with most polymers, while its loose structure favors conformational mobility of macromolecular chains at the interface.

Magnetic properties and giant magnetoimpedance of surface modified Co-based amorphous ribbons with carbon covering

“…Fig.1(c) shows the effect of carbon re-distribution as a result of covering interaction with electron beam during SEM studies (black squares are previously scanned areas). Observed compositional changes are consistent with proposed mechanism of the low temperature carbon deposition [10]. The next step is to understand the role of the surface modification in the change of magnetic properties.…”

“…Moreover, an appearance of dark circle areas on SEM images of the sample after the treatment can be noticed on Fig.1 (b). Similar defects corresponding to areas an accumulation of carbon were also observed in previous experiments with thin films [10]. Fig.1(c) shows the effect of carbon re-distribution as a result of covering interaction with electron beam during SEM studies (black squares are previously scanned areas).…”

“…Surface modification of the samples was done in the toluene at ambient conditions for one or two months period. Toluene was used because the best results in previous experiments were observed with a use of it [10]. Table 1 lists all samples and their states.…”

“…Room temperature carbon deposition was discovered for the case of Fe and Ni nanoparticles and Fe and FeNi films [10]. Heterogeneous Scholl oxidation of the aromatic hydrocarbons was proposed as possible mechanism of the reaction with the first step being an oxidation of atoms of metals by oxygen dissolved in the solvent.…”

Encapsulation of metallic iron magnetic nanoparticles by polyacrylamide in water suspensions

“…The detailed description of EEW equipment designed at the Institute of Electrophysics of RAS (Ekaterinburg, Russia) is given elsewhere [6][7][8]. The method is based on the evaporation of a portion of metal wire by the electric high power pulse in the explosion chamber filled with the inert atmosphere.…”