L. M. Tyrina

Titanium-supported nickel-copper oxide catalysts for oxidation of carbon(II) oxide

Nickel-copper compositions for catalytic oxidation of carbon(II) oxide to carbon(IV) oxide were prepared by impregnation of oxide films on titanium surface, obtained by plasma electrolytic oxidation followed by annealing. Plasma electrolysis oxide coatings with a layer thickness of 5 to 50 μm were generated using different electrolytes. The compositions were studied by X-ray powder diffraction, X-ray spectral analysis, and electron microscopy, and moisture absorption of the initial plasma electrolytic structures was estimated. A linear correlation was found between the overall concentration of nickel and copper (4 to 25 mol %) in the surface layer of ∼2–5-μm compositions and their catalytic activity. The overall concentration of nickel and copper was found to increase in parallel with the moisture absorption of plasma electrolytic oxidation coatings. Nickel-copper compositions based on plasma electrolytic oxidation coatings generated in a silicate electrolyte displayed the best catalytic, mechanical, and adhesion properties.

Comparative analysis of the composition, structure, and catalytic activity of the NiO-CuO-TiO2 on Titanium and NiO-CuO-Al2O3 on aluminum composites

The catalytically active oxide structures based on Al and Ti prepared by plasma-electrolytic oxidation (PEO) and additionally modified by impregnation with an aqueous solution of nickel and copper nitrates followed by annealing were studied. The oxide film-metal composites were studied using X-ray diffraction and X-ray spectroscopic analysis, X-ray electron spectroscopy, and electron microscopy. The catalytic activity of the composites in the reaction of CO oxidation was studied. In spite of differences in the elemental composition and morphology, the initial oxide layers on Al and Ti were comparable in terms of activity. Microgranules of size ∼ 1 µm and formations from tens to hundreds of nanometers in size were detected on the surface of PEO layers. The modified layers contained crystalline CuO, NiO, and Al2O3 or TiO2 phases. The surface layers of the modified structures about 3 nm in thickness on AMg5 aluminum alloy and VT1-0 titanium had the same elemental composition but exhibited different activity in the reaction of CO oxidation to CO2.

Catalytic properties of aluminum/nickel-, copper-containing oxide film compositions

The possibility of the single-step formation of nickel- and copper-containing thin-film oxide systems on aluminum by plasma electrolytic oxidation was demonstrated. The resulting structures were found to be active in the reaction of CO oxidation to CO2 in the temperature region 300–500°C. However, the resulting structures exhibited stable catalytic activity only in the simultaneous presence of nickel and copper compounds. The films were studied using X-ray diffraction, X-ray spectroscopic analysis, X-ray photoelectron spectroscopy, and electron microscopy. The resulting films exhibited an essentially inhomogeneous composition through the thickness. Electrolyte elements such as nickel, copper, sodium, and phosphorus were concentrated at the surface. Nickel occurred as Ni2+, and copper occurred as Cu+ and Cu2+. The surface contained carbon in detectable amounts.

Obtaining ZrO2 + CeOx + TiO2/Ti compositions by plasma-electrolytic oxidation of titanium and investigating their properties

Regularities of the effect produced by Ce2(SO4)3 salt introduced in an aqueous electrolyte containing Zr(SO4)2 on the plasma-electrolytic formation of oxide coatings on titanium, their composition, and structure are studied. ZrO2 + CeOx + TiO2 three-phase oxide coatings with a thickness about 10 μm are obtained. The coatings involve ZrO2 cubic phase. The ZrO2-to-TiO2 phase ratio in the coatings can be controlled. The zirconium content in the coatings reaches 20 at %, while that of cerium is 3–5 at %. The surface layer (∼3-nm thick) contains Ce3+ (∼30%) and Ce4+ (∼70%). Pores in the surface part of coatings have diameters around or smaller than 1 μm and are regularly arranged. The obtained systems have a certain catalytic activity with respect to the oxidation of CO to CO2 at temperatures above 400–450°C. The coatings are corrosion-resistant in chloride-containing environments. The thickness h of coatings depending on the charge Q supplied to the cell is described by the equation h = h0(Q/Q0)n, where n = 0.35 and h0 is the thickness of the coating formed at Q0 = 1 C/cm2.

Formation, structure, composition, and catalytic properties of Ni-, Cu-, Mn-, Fe-, and co-containing films on aluminum

Layers containing oxygen compounds of copper and nickel and(or) of one of transition metals (manganese, cobalt, iron) were formed on an aluminum alloy by the plasma-electrolytic oxidation method. The layers were characterized by means of X-ray phase analysis, X-ray fluorescence microanalysis, and scanning electron microscopy and tested in the reaction of CO oxidation to CO2.

Deposition, composition, and activity in CO oxidation of anodic layers with platinum on aluminum and titanium

Pt + TiO2/Ti(Al) and Pt + CeO2 + ZrO2 + TiO2/Ti composites were formed by plasma electrolytic oxidation and their surface composition and catalytic activity in CO oxidation to CO2 were studied.

Phase Composition of Coatings Formed on Titanium in Borate Electrolyte by Microarch Oxidation

The effect of oxidation conditions, temperature and concentration of the electrolyte, and its transformation from the true to colloidal solution on the phase composition and electrical resistance of coatings was studied.

Pt/SiO2 and Pt/TiO2/Ti compositions and their catalytic properties

To support Pt on finely dispersed SiO2 or TiO2/Ti structures obtained via the plasma-electrochemical technique, the extraction-pyrolytic method was used. By means of scanning electron microscopy and X-ray spectral analysis, it was shown that the oxide compositions contain up to 3.5 wt % of Pt. The resulting compositions, Pt/SiO2 and Pt/TiO2/Ti, were tested as catalysts for CO conversion. In the first case, the complete conversion of CO can be reached at 250°C, while in the second case it can be reached at 300°C.

Silicate coatings on titanium, modified with transition metal oxides and their activity in CO oxidation

CuO+MxOy/TiO2+SiO2/Ti composites (M = Mn, Fe, Co, Ni) were produced by plasma-electrolytic oxidation and impregnation, followed by annealing. The elemental and phase composition of these composites were examined and their activity series in CO oxidation was determined.

Catalytic properties of Ni-, Cu-containing oxide film/aluminum alloy composition

Copper and nickel oxide compounds containing layers were formed using the plasma electrolytic oxidation technique on aluminum and its alloys. It was studied how the aluminum alloy compound impacted on the Ni-, Cu-containing oxide film/aluminum alloy combinations catalytic activity in a CO oxidation reaction.