This paper reports a method for the fabrication of mineral-like SrMoO4 ceramics with a powellite structure, which is promising for the immobilization of the high-energy 90Sr radioisotope. The reported method is based on the solid-phase “in situ” interaction between SrO and MoO3 oxides initiated under spark plasma sintering (SPS) conditions. Dilatometry, XRD, SEM, and EDX methods were used to investigate the consolidation dynamics, phase formation, and structural changes in the reactive powder blend and sintered ceramics. The temperature conditions for SrMoO4 formation under SPS were determined, yielding ceramics with a relative density of 84.0–96.3%, Vickers microhardness of 157–295 HV, and compressive strength of 54–331 MPa. Ceramic samples demonstrate a low Sr leaching rate of 10−6 g/cm2·day, indicating a rather high hydrolytic stability and meeting the requirements of GOST R 50926-96 imposed on solid radioactive wastes. The results presented here show a wide range of prospects for the application of ceramic matrixes with the mineral-like composition studied here to radioactive waste processing and radioisotope manufacturing.

The paper presents a reliable technology combining sol–gel synthesis and spark plasma sintering (SPS) to obtain SrTiO3 perovskite-type ceramics with excellent physicomechanical properties and hydrolytic stability for the long-term retention of radioactive strontium radionuclides. The Pechini sol–gel method was used to synthesize SrTiO3 powder from Sr(NO3)2 and TiCl3 (15%) precursors. Ceramic matrix samples were fabricated by SPS in the temperature range of 900–1200 °C. The perovskite structure of the synthesized initial SrTiO3 powder was confirmed by X-ray diffraction and thermal analysis results. Scanning electron microscopy revealed agglomeration of the nanoparticles and a pronounced tendency for densification in the sintered compact with increasing sintering temperature. Chemical homogeneity of ceramics was confirmed by energy dispersive X-ray analysis. Physicochemical characteristic studies included density measurement results (3.11–4.80 g·cm−3), dilatometric dependencies, Vickers microhardness (20–900 HV), and hydrolytic stability (10−6–10−7 g·cm−2·day−2), exceeding GOST R 50926-96 and ISO 6961:1982 requirements for solid-state matrices. Ceramic sintered at 1200 °C demonstrated the lowest strontium leaching rate of 10−7 g/cm2·day, optimal for radioactive waste (RAW) isolation. The proposed approach can be used to fabricate mineral-like forms suitable for RAW handling.

Ti/TiO2–ZrTiO4–ZrO2, Ti/TiO2–CeO2, and Ti/TiO2–ZrTiO4 composites have been fabricated by the one-stage plasma electrolytic oxidation (PEO) in aqueous electrolytes containing 0.05 mol/L Zr(SO4)2, 0.05 mol/L Ce(SO4)2, or their mixtures, respectively. The surface morphology and composite composition have been studied by scanning electron microscopy, X-ray powder diffraction, and energy dispersive analysis. The photoelectrochemical properties of the composites have been studied under UV light in the potential range of 0.0–1.2 V. The Ti/TiO2–ZrTiO4–ZrO2 composites exhibit high photoelectrochemical activity: they generate photocurrents of 73 μA without potential and 230 μA in the potential range from 0.2 to 1.2 V. Such composites are promising as active photoanodes for water splitting. The introduction of cerium into the PEO coatings leads to a sharp decrease in photocurrents (0.1–10 μA).

We present a study of the scanning electron microscopy images of the TiO2 nanotube array. The initial and modified samples were examined before and after annealing. It has been found that the annealing of the modified and unmodified samples results in different degrees of the local ordering. The nanotubular coverings were modified by Pt nanoparticles formed by the H2PtCl6 solutions infiltration for change of their electro- and photo catalytic properties estimated by measuring the photoelectric currents. The influence of the morphology and ordering degree of the nanotubular coverings on the manifestation of their functional properties has been studied. A two-dimensional Fourier transform was applied for obtaining information on the occurrence of periodicities in the ordering of nanotubes. Correlation analysis was performed to find out the invisible regularities and periodicities in the structure of the nanotube arrays. The analysis of the photoactivity of the samples was also carried out.

The results of a cross-correlation analysis of the relationship between the process conditions for obtaining CoNiFeSiB amorphous alloys, their physical and chemical properties and structure are presented. The alloys are obtained by single-roll rapid quenching on a copper wheel at frequencies from 30 to 60 Hz, which corresponds to linear velocities from 22 to 38 m/s, a chamber pressure from 0.05 to 0.6 atm, and a pressure in the crucible from 0.4 to 0.6 atm. Elemental analysis is carried out; the atomic and surface structures, phase-transition parameters upon heating, and the corrosion properties are investigated. Correlations between the structural-ordering parameters and physical and chemical properties are determined. Regression models of the dependence between the structural characteristics, physical and chemical properties, and process conditions of production are formulated. A regression model for the dependence of the average cluster area in the atomic image on the specific energy of structural changes is proposed. The concentrations of nickel, silicon, and boron in cobalt-based alloys are found to play an important role in determining the structural characteristics and properties of the alloys.

This paper describes the photoelectrochemical properties of titanium oxide formed by plasma electrolytic oxidation. The possibility of correlation between the photoactivity of the formed systems and their impedance characteristics was investigated. Equivalent circuitries which allow explanation of the character of the impedance spectra were constructed and interpreted. The role of heat treatment and surface modification with platinum on the photoelectrochemical and electrochemical characteristics of the formed systems was demonstrated.

This paper explores TiO2 nanotubes array ordering on the basis of representation of coordination Cayley tree graphs (CTG). Nanotubes array are obtained by the method of anodic oxidation in different voltage and time modes in aqueous and non-aqueous fluorinated electrolytes, containing glycerin and some surface-active substances (SAS). It is shown that such characteristics of CTG as mode of branchiness distribution and average branchiness correlate to basic type of structure ordering.

Analysis of formation of highly-ordered titanium oxide nanotubes array at the level of currents is carried out. It has been found that marking impulse possesses fine structure characterized by uncommon behavior. It is a series of small steps alternated by sharp overshoots that can be identified as Levy flights. Attractor obtained from current realizations points at the existence of quasistochastic in terms of phase and strictly periodic mode of partial Levy flights. It corresponds to trigger mode of system behavior with two stable states peculiar to auto-oscillating process.

Nanotubular titanium oxide coatings with different morphology and dimensional parameters are formed by anodic oxidation under different voltage and time modes in fluorine aqueous-nonaqueous electrolytes containing glycerin as well as several surface-active agents (SAA). Their morphological peculiarities are examined and qualitative and quantitative analysis of obtained types of ordering is carried out, geometric configuration entropy are calculated on the base of analysis SEM images and theory of self-organization.

The comparative analysis of formation of highly-ordered nanotubes array of titanium oxide obtained by the method of anodizing in non-aqueous (No. 1) and semi-aqueous (No. 2) electrolytes is considered in this paper. Analysis of nanotubes formation current of both samples has shown that the fine structure of the current is observed: a series of small steps alternated by sharp swells. Attractor obtained from current implementation of sample No. 1 points at the existence of quasistochastic in terms of phase and strictly periodic mode of partial Levy flights. Attractor of sample No. 2 is more smoothed. Current realizations of both samples points at trigger mode of system behavior peculiar to auto-oscillating process.

In this work, an octavinylsilsesquioxane film has been formed on an anodized aluminum substrate with a highly organized surface oxide layer. Transferring the resulting film on a polyvinylsilsesquioxane substrate, multilayer film waveguides are formed on the basis of octavinylsilsesquioxane nanowhiskers. Their optical properties are studied.

Исследованы элементный и фазовый составы, морфология поверхности и параметры пористой структуры оксидных покрытий на титане, сформированных методом плазменно-электролитического оксидирования в водных силикатных электролитах. Покрытия изучены рентгеноспектральным методом, рентгенофазовым анализом, электронной микроскопией и методом адсорбции паров воды. Параметры пористой структуры покрытий зависят от времени формирования покрытий, состава электролита и дополнительной термической обработки.

Elemental and phase compositions, surface morphology, and parameters of the porous structure of oxide coatings formed on titanium by plasma-electrolytic oxidation in aqueous silicate electrolytes are determined. The coatings are studied with the use of the X-ray spectral method, X-ray phase analysis, electron microscopy, and the water-vapor adsorption method. The parameters of the porous structure of coatings are found to depend on the duration of formation of the coatings, composition of the electrolyte, and additional thermal treatment.

The behavior of metal-oxide electrodes formed using the method of plasma electrolytic oxidation in a tetraborate electrolyte and additionally modified by platinum at acid-base and precipitation potentiometric titration has been investigated. The possibility of application of the fabricated electrodes in analysis of man-made waste waters on the example of potentiometric determination of alkalinity and chlorides content has been demonstrated. The advantages of the fabricated metal-oxide systems related to their polyfunctional character and the possibility to determine two hydrochemistry parameters using a single electrode have been shown. Key words: metal-oxide electrodes, plasma electrolytic oxidation, potentiometry, hydrochemistry parameters (Russian) DOI: http://dx.doi.org/10.15826/analitika.2013.17.3.003 G.I. Marinina, A.S. Lapina, M.S. Vasilyeva, O.D. Arefyeva, and N.B. Kondrikov School of Natural Sciences, Far East Federal University, Vladivostok, Russia

The behavior of metal-oxide electrodes formed using the method of plasma electrolytic oxidation in a tetraborate electrolyte and additionally modified by platinum at acid-base and precipitation potentiometric titration has been investigated. The possibility of application of the fabricated electrodes in analysis of man-made waste waters on the example of potentiometric determination of alkalinity and chlorides content has been demonstrated. The advantages of the fabricated metal-oxide systems related to their polyfunctional character and the possibility to determine two hydrochemistry parameters using a single electrode have been shown. Key words: metal-oxide electrodes, plasma electrolytic oxidation, potentiometry, hydrochemistry parameters (Russian) DOI: http://dx.doi.org/10.15826/analitika.2013.17.3.003 G.I. Marinina, A.S. Lapina, M.S. Vasilyeva, O.D. Arefyeva, and N.B. Kondrikov School of Natural Sciences, Far East Federal University, Vladivostok, Russia

Composition, surface structure (including those after annealing at high temperature) and the catalytic activity in the steam conversion of naphthalene were studied for Ce-, Zr- and Mn-containing oxide layers obtained on titanium by means of plasma electrolytic oxidation. The composition and structure of oxide systems were studied by means of XRD phase analysis, energy dispersion analysis and scanning electron microscopy. It was demonstrated that Ce-, Zr-containing structures exhibit a rather high thermal stability: the elemental and phase composition, the structure of their surface remain almost unchanged after annealing in atmospheric air at the temperature values up to 800 degrees C. The catalytic studies demonstrated a rather high activity of Ce-, Zr-containing coatings in the reaction of naphthalene steam conversion at the temperature values up to 850 degrees C. Mn-containing oxide structures have developed surface covered with nano-whiskers those were not detected after thermal treatment. Mn-containing oxide systems exhibited a lower level of naphthalene conversion as compared to Ce-, Zr-containing coatings, which could be connected with substantial changing their surface and with the formation of low-active fused manganese silicates at high temperature values.

Layered oxide coatings catalyzing oxidation of CO to CO2 by plasma-electrolytic oxidation in aqueous electrolytes with trilonate complexes of manganese were studied. Data on the elemental composition of their surface and deep layers, phase composition, and specific features of growth were obtained.

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.

We have studied the composition and structure of films 20–30 µm thick prepared by plasmaassisted electrochemical oxidation (PEO) and additionally modified by impregnation in aqueous solutions of nickel and copper nitrates and then annealed. The investigative tools used were powder X-ray diffraction, electron probe microanalysis (EPMA), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy. Unmodified film/titanium composites have a certain catalytic activity in CO oxidation to CO2 at temperatures above 300°C; for modified layers, these temperatures are noticeably higher. Modification influences the surface structure, relief, and elemental composition. Relations between the composition and catalytic properties of the oxide layers are discussed.