The
formation of oxide nanorolls decorated with nanotubes during
anodic oxidation of amorphous Fe70Cr15B15 alloy in hydrophobic ionic
liquid 1-butyl-3-methylimidazolium tetrafluoroborate (IL) was revealed.
The unusual architecture was observed for the first time on the surface
of amorphous alloy. The generation of the novel type of nanostructure
by electrochemical oxidation of the amorphous Fe70Cr15B15 alloy occurs
only in hydrophobic ionic liquid and in the presence of the natural
oxide film at the surface. Anodization of the oxide-free metal surface
of the amorphous Fe70Cr15B15 alloy to be achieved by the treatment
of the electrode with benzoic acid was found to result in no formation
of both nanorolls and nanotubes. Electrochemical behavior of the amorphous
Fe70Cr15B15 alloy in ionic liquid was proved to depend strongly on
the state of the electrode surface before oxidation. The influence
of the state of the surface of amorphous Fe70Cr15B15 alloy leading
to the nanostructure formation was studied by means of preliminary
partial etching with benzoic acid of various concentrations.
The impact of preliminary treatment (mechanical abrasion; chemical etching and anodization in ionic liquid) on the surface structure and corrosion behavior of Fe70Cr15B15 metal glass was studied. The detachment of the anodic oxide film from untreated Fe-amorphous alloy under anodization in ionic liquid was observed for the first time. The formation of hexagonal nanostructures (cells) on the surface of the Fe70Cr15B15 alloy after mechanical abrasion and following anodization in 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) ionic liquid was also detected for the first time. Electrochemical corrosion of the initial and pretreated amorphous alloy was tested in a Na2SO4 aqueous solution. The resistance to corrosion was found to be enhanced slightly after mechanical abrasion. The sample with hexagonal nanostructures obtained after anodization of the mechanically abraded sample demonstrated a more significant anodic shift in the corrosion potential (Ecorr = + 379 mV) compared with that for the initial alloy (Ecorr = −125 mV).
The article presents the results of studies on the formation of nanostructures on the surface of an amorphous alloy Co₇₅Si₁₅Fe₅Cr₄.₅Al₀.₅ using electrochemical anodizing at a controlled current in an ionic liquid BmimNTf₂. The corrosion (polarization resistance) stability of the alloy modified under different conditions of anodization in a Ringer's solution has been studied. The samples showed sufficient resistance to corrosion. Modification of the surface under certain anodizing conditions (5 mA, 200 s) leads to coating of the surface with oxide nanostructures – nanocells, which contribute to increasing resistance of the alloy to corrosion.
The electro-oxidation of iodide has been investigated using cyclic voltammetry on a platinum electrode in ionic liquids tributylmethylammonium bis(trifluoromethylsulfonyl)imide (N4441NTf2) , trioctylmethylammonium salicylate (TOMAS) and 1-butyl-3-methylimidazolium tetrafluoroborate. The hydrophobic/hydrophilic THOMAS ionic liquid was used for the first time in electrochemical research. Two electro-oxidation processes are observed in all of the investigated ionic liquids. The calculation of the number of electrons corresponding to every electro-oxidation stage suggested that in N4441NTF2 electro-oxidation follows a different path than those described in the literature. The hydrophobicity/hydrophilicity of ionic liquids affects electrochemical processes. It was shown that the best electrolyte for electro-oxidation of iodide is hydrophobic ionic liquid N4441NTf2.
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