Composition, surface structure, and thermal behavior of ZrO2 + TiO2/Ti and ZrO2 + CeOx + TiO2 composites formed by plasma-electrolytic oxidation

Specific surface structures of ZrO₂ + TiO₂ (I) and ZrO₂ +CeO_x + TiO₂ (II) coatings on titanium before and after annealing at 850°C for 24 h in air are studied. Whiskers are found on the surface of type-I coatings before annealing, and perfectly edged crystals composed of TiO₂ and ZrO₂ oxides are found upon annealing. Pores in both coatings have a multilevel structure. In the case of type-I coatings, orifices of pores are covered with titanium. In type-II coatings, pore orifices contain titanium, zirconium, and oxygen. Oxygen deficiency implies that titanium and zirconium are present in pore orifices in metallic state. In type-II coatings, the surface distribution of cerium is heterogeneous. Mechanical treatment of the annealed coatings causes their exfoliation from the substrate metal. In the case of both coatings, the exfoliating surfaces are composed of TiO₂ blocks containing excess oxygen.     

Functional oxide structures on a surface of metals and alloys

The investigations of the plasma electrolytic processes in our laboratory are aimed to the development of conditions of formation of oxide layers with determined composition, structure and functional properties on the surface of valve metals (Al, Ti) and their alloys.……     

Magnetoactive oxide layers formed on titanium by plasma-electrolytic technique

Two kinds of iron-containing coatings, specifically those obtained from electrolytes containing polyphosphate iron complexes (no. 1) and from electrolyte suspensions (no. 2), are formed and studied. According to the microprobe analysis, the iron content in the coatings is 6–7 at %. Coatings of type 1 are paramagnetic, while coatings of type 2 are ferromagnetic. The distribution of elements over the depth of coatings is heterogeneous and the typical components of the surfaces have different compositions. Iron and titanium are concentrated at the bottom and walls of pores. Upon annealing in air, iron and titanium phosphates crystallize in coatings no. 1, while maghemite is formed in coatings no. 2. Based on the results obtained, the supposition is made that the ferromagnetic properties of type 2 coatings are determined by the presence of fine-dispersed magnetite and/or maghemite particles in them, as well as titanium-magnetite and/or titanium-maghemite grains.     

Spark-Anodic Oxide Coatings Formed on Al and Ti Alloys in Tungstate-Containing Phosphate–Vanadate Baths

Oxide coatings superficially, enriched with P, V, or W, were formed on aluminum and titanium alloys by their spark-anodizing in aqueous baths containing NaH₂PO₄ · 2₂ (45.9 g/l), NaVO₃ · 2₂ (15 g/l), and different concentrations of Na₂WO₄ · 2₂. The coatings' composition was investigated with laser mass spectrometry and microprobe analysis, while the state of phosphate groups in solution, was with NMR spectroscopy using ³¹P nuclei. The elemental composition of the coatings presumably depends on the composition and concentration of vanadate-tungstate-phosphates and vanadate-tungstates in solution.     

On the Effect of an Electrolyte and Impregnating Solution on Microcrystal Growth on the Surface of W-Containing PEO Coatings on Titanium at Oxidative Annealing

Protection of Metals and Physical Chemistry of Surfaces - It has been confirmed in the present work that the components of an electrolyte and impregnating solution accumulated in pores can serve as...     

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

Theoretical Foundations of Chemical Engineering - To support Pt on finely dispersed SiO2 or TiO2/Ti structures obtained via the plasma-electrochemical technique, the extraction-pyrolytic method was...     

Catalytic properties of metallic fibers fabricated by tempering of melt on a rotating heat-receiver

Metallic fibers fabricated by the method of directly suspended melt-droplet extraction are promising for application in catalysis as carriers of catalytically active compounds and as catalytic systems themselves due to their physicochemical properties, structure, surface defects, and low hydrodynamic resistance of porous permeable materials formed from them. The catalytic activity of fibers based on copper, nickel, iron, aluminum, and titanium, also containing noble, transition, refractory, and rare-earth metals, in the reaction of CO oxidation has been estimated. Among the studied samples, fibers based on copper, copper–nickel alloy, and Nichrome with addition of noble metals have been found promising to perform further studies for their application as catalysts of oxidation–reduction reactions.     

The Effect of Iron Precursors in an Electrolyte on the Formation,Composition, and Magnetic Properties of Oxide Coatings on Titanium

The effect of iron sulfate and citrate addition into the base alkaline phosphate-borate-tungstate electrolyte on the peculiarities of plasma-electrolytic formation of coatings on titanium, their thickness, surface morphology, composition, and magnetic characteristics has been investigated. In the first electrolyte, dispersed particles of iron hydroxides and hydroxo salts are formed, whereas the second one comprises a true solution. Numerous Fe-containing crystallites of a size of ~50 nm united into agglomerates have been found in the suspension electrolyte with FeSO₄. Such coatings manifest ferromagnetic properties: coercive force Hc of the samples is 62 and 148 Oe at 300 and 2 K, respectively. In pores of the coatings obtained in the electrolyte with FeC₆H₅O₇ (true solution), the presence of crystallites is less clearly expressed, while crystallites themselves are larger and molten to a higher degree. At room temperature, such coatings are paramagnetic; at 2 K, they manifest ferromagnetic behavior with the Н _с value of up to 200 Oe. The available data enable one to associate ferromagnetic properties of the formed coatings with metals concentrated in pores.     

Subgroup decomposition of plasmonic resonances in hybrid oligomers: modeling the resonance lineshape

Plasmonic resonances with a Fano lineshape observed in metallic nanoclusters often arise from the destructive interference between a dark, subradiant mode and a bright, super-radiant one. A flexible control over the Fano profile characterized by its linewidth and spectral contrast is crucial for many potential applications such as slowing light and biosensing. In this work, we show how one can easily but significantly tailor the overall spectral profile in plasmonic nanocluster systems, for example, quadrumers and pentamers, by selectively altering the particle shape without a need to change the particle size, interparticle distance, or the number of elements of the oligomers. This is achieved through decomposing the whole spectrum into two separate contributions from subgroups, which are efficiently excited at their spectral peak positions. We further show that different strengths of interference between the two subgroups must be considered for a full understanding of the resulting spectral lineshape. In some cases, each subgroup is separately active in distinct frequency windows with only small overlap, leading to a simple convolution of the subspectra. Variation in particle shape of either subgroup results in the tuning of the overall spectral lineshape, which opens a novel pathway for shaping the plasmonic response in small nanoclusters.     

Surface structure of multicomponent oxide coatings on titanium

Data on the surface structure of Cu-Ni containing oxide films formed on titanium under the effect of electric spark and arc discharges are considered at the scale of tens to hundreds nanometers. The surface sites of films around electric discharge channels are perforated with pores of diameters around 10 nm. Spheroids with diameters of tens to hundreds of nanometers, which chiefly elements contain involved in the electrolyte components including heightened amounts of copper and carbon, are distributed over the surface. Furthermore, agglomerates formed by planar particles with sizes of tens to hundreds of nanometers of irregular geometric shapes are also present on the surface. Elemental compositions of the film surface and planar agglomerates coincide. The particles are supposedly the products of the electric-discharge erosion of the film material.