Electrocrystallization and physicochemical properties of nanosized copper-containing powders

The electroctystallization mechanism of copper-containing powders from water-isopropanol solutions of copper dichloride is studied. The effect of the nature and concentration of solution components on the electroplating of cathodic deposits is considered. Morphological characteristics of particles of the synthesized powder are determined on a transmission electron microscope. The qualitative composition of synthesized powders is determined.     

Numerical simulation of structure transformation processes as the basis for regulating the properties of nanodisperse composition systems and materials

Using computer simulations, the regularities of structure formation in disperse systems under dynamic conditions that predetermine the nature of the structure formed and, hence, the properties of obtained nanodisperse composition materials (materials with a nanodisperse component) are considered. Phenomena of the appearance and the development of a macroscopic structural heterogeneity, namely, the break in continuity of the structure in highly concentrated systems are reproduced, as are the conditions for the removing the break using surface active substances and vibrational impacts, which allows one to control the properties of disperse materials synthesized based on highly disperse solid phases.     

The corrosion inhibition of Ti-alloy (VT-9) in mixture of H<Subscript>2</Subscript>SO<Subscript>4</Subscript>-NaF by organic compounds

This investigation deals with corrosion behavior of high strength titanium alloy in concentrated sulphuric acid solution containing different concentrations (500, 1000, 1500 ppm) of fluoride ion (F⁻) using various organic compounds (MPA, L-OH, NFP) as inhibitor, potentiodynamically. The open circuit potential values noted before and after each experiment, varied appreciably. These values were negative before polarization but after completion of the experiment turned positive and remained stable over long period of time. It is observed that cathodic current density values increase with increasing cathodic potential (more negative) and fluoride ion. The values of cathodic Tafel slopes derived from the curves (∼110 − 140 mV/dec I) indicate hydrogen evolution reaction (h.e.r). The corrosion potential (E _corr) varied slightly with addition of inhibitors. The corrosion current densities (I _corr) increased with increasing fluoride ion concentration, but these values decreased appreciably when inhibitor (MPA) was used. SEM micrograph reveals reduction of pits in the presence of inhibitor (MPA). So this concludes that organic compound was used in this case acts as a good inhibitor. The article is published in the original.     

Analysis of mathematical models and a theory of polarization distribution in continuous 3D-porous electrodes

Conventional and original mathematical models describing the distribution of an electrochemical process in a continuous 3D volume electrode as in a pseudohomogeneous environment are discussed. Some peculiarities of the operation of such electrodes related to the appearance of anodic zones on a cathodically polarized electrode are considered. Mathematical analysis of the model equations and their solutions is given.     

Study of the sorption-kinetic properties of carbon molecular sieves

To elucidate the role of the electron-exchange properties of arene molecules that form the pore walls of carbon molecular sieves in their interactions with sorbate molecules, the correlation between the electronexchange and sorption-kinetic properties was studied. The electron-exchange properties were estimated by using quantum-chemical modeling based on the energies of formation of singly charged anions and cations and neutral (both oxidized and reduced) molecules.     

Thermodynamic analysis of the gas phase composition over uranium-plutonium carbonitride irradiated with fast neutrons

A thermodynamic analysis of the gas phase composition over uranium-plutonium carbonitride U_0.8Pu_0.2(C_0.5N_0.5)_0.995 irradiated with fast neutrons was carried out with respect to temperature and burnout. In the temperature range of 900–2500 K, accumulation of fission products in fuel resulted in the formation of a multicomponent gas phase containing the following basic elements and compounds: volatile (Cs, Sr, Ba, Se, Te, I, Pd, CsI, Cs₂I₂, BaI, SrI, BaI₂, SrI₂, LaSe, TeSe, and LaTe), nitrogen-containing components (N₂, N, CN, CN₂, C₂N₂, UN, UN₂, PuN₂, CsN, CeN, LaN, YN, MoN, and ZrN), carbon-containing components (C, UC, UC₂, UC₄, PuC, PuC₂, PuC₄, ZrC, ZrC₂, YC₂, CeC₂, LaC₂, and NdC₂), and hardly volatile metals (U, Pu, Ru, Rh, Pd, Y, Ce, La, Nd, Tc, Mo, and Zr). The partial pressures of the said gas phase components over carbonitride fuel were calculated with respect to temperature and burnout (up to 18%).     

Voltammetric characteristics of the metal-oxide-electrolyte system at electrode polarization with pulse voltage

The method of formation of oxide coatings on anodically polarized electrodes under galvanostatic mode with the online, computer-controlled measuring, processing, and calculation of electric parameters is proposed. Voltammetric characteristics of these processes are considered using a variable reactive resistance. It is shown that a thermal breakdown is preceded by an electric breakdown of potential barriers formed in the metal-oxide-electrolyte system. In the oxide layer structure, three zones that differ in the structure and intensity of electric fields can be singled out. The ratio of these zones is determined by the electron work functions of metal, oxide, and electrolyte.     

Influence of the structures of hydrogen-bonded dimeric molecules on their adsorption at graphitized thermal carbon

This study is devoted to the influence of the structures of hydrogen-bonded dimeric molecules on their adsorption at graphitized thermal carbon (GTC). The thermodynamic adsorption characteristics (TACs) of amino acid dimers and dimers of amino acids with acetic acid and formamide at GTC were determined. The results obtained for the adsorption of dimeric molecules at the carbon sorbent were compared with the calculated data for the molecules of the corresponding amino acids at GTC. The geometric parameters of dimeric molecules were varied to analyze the influence of the hydrogen bond lengths on the TACs of the compounds under study.     

Laser-ellipsometric monitoring of corrosive attack

The problems under consideration are related to the development and practical application of laser, reflectometric, and ellipsometric methods of diagnostics of corrosion damage both at the micro and macro level. The following basic methods of probe laser and ellipsometric studies of corrosion electrochemical processes are considered: automatic and return-path ellipsometry, microscopic and video ellipsometric techniques, methods of light scattering, fluctuation and noise reflectometry, probe noise ellipsometry, microlocalized electrochemical processes, remote ellipsometry, laser and spectral tomography, and information optical 3D technologies for reconstructing the 3D structure of heterogeneous near-electrode layer. The primary attention was focused on the problems of application of laser and ellipsometric methods in the practice of real corrosion electrochemical studies.     

Synergistic inhibition between Schiff’s bases and sulfate ion on corrosion of aluminium in sulfuric acid

The effect of Schiff’s bases alone and Schiff’s bases with additive Na₂SO₄ on the corrosion of aluminium in H₂SO₄ have been investigated by using weight loss method. The present study revealed that aluminium in H₂SO₄ has been more efficiently inhibited by Schiff’s bases in the presence of additive Na₂SO₄ than Schiff’s bases alone due to the synergistic effect between Schiff’s bases and Na₂SO₄. Inhibition efficiency was found maximum upto 95.02% for aluminium in H₂SO₄ by Schiff’s bases in presence of additive NaNa₂SO₄. The adsorption of inhibitor accords with the Langmuir adsorption isotherm. Results obtained in both the cases indicate the dependence of inhibition efficiencies on the concentration of Schiff’s bases, additive Na₂SO₄ and also on the concentration of H₂SO₄ solution. The results show the increasing trends of inhibition efficiency with the concentration. The article is published in the original.     

Evolution of the structures and sorption properties of dehydrochlorinated chloropolymers during their thermal conversions

A microporous carbon material can be obtained by dehydrochlorination of the polymeric formulation poly(vinyl chloride)-poly(vinylidene chloride) in the presence of KOH followed by thermal treatment at a relatively low temperature (350°C in a nitrogen-oxygen gas mixture (10: 1 w/w)). This is because the chemical dehydrochlorination gives highly reactive chloro-containing polyconjugate systems. The conversion of chloropolyene systems into carbon structures is confirmed by Raman spectroscopy and TGA with MS analysis of volatile pyrolysis products. The resulting carbon material has a system of pores including ultramicropores 6.5 ± 0.5 Å), micropores (16 ± 1 Å), and mesopores (average pore size 150 ± 7 Å).     

Comparative analysis of the adsorption of the stereoisomers of hydroxy- and dihydroxyproline at graphitized thermal soot

The thermodynamic characteristics of the adsorption of proline and its derivatives at graphitized thermal soot (GTS) were determined. It was found that the arrangement of the hydroxy groups in the amino acid molecule influences its adsorption at GTS. The thermodynamic characteristics of the adsorption of the stereoisomers of hydroxy- and dihydroxyproline at GTS were calculated. The influence of the internal rotation angles in the molecules of proline and its derivatives on their adsorption at GTS was studied.     

Electroplating tin from acidic sulfate baths containing benzaldehyde

Voltammetry and electrochemical impedance spectroscopy (EIS) are used in studying the kinetics of electroplating tin from 0.01 M Sn(II) baths containing 1 M H₂SO₄ and millimolar benzaldehyde (BA) additives. BA substantially decreases the reduction rate of Sn(II) in a broad range of cathodic polarization. Experimental EIS data are analyzed in terms of an equivalent R_ω(Q_dl[R_aC_aW_a][R_ctQ_d]) circuit, including a Faraday process impedance ([R_ctQ_d] subcircuit), as well as diffusion and kinetic stages of BA adsorption ([R_aC_aW_a] subcircuit). Values of the subcircuit elements are found to depend on the duration of a contact between the electrode and solution and on the BA concentration. An increase in the charge transfer resistance (R_ct) and a simultaneous decrease in the double layer capacitance (Q_dl) indicate that the electrochemical reduction of Sn(II) is inhibited by the BA adsorption. With an increase in the cathodic polarization, the effect becomes more pronounced, which is manifested in the low current densities and negative impedance values.     

Heat-resistant glass-ceramic coatings protecting low-alloyed steels against high-temperature gas corrosion

Glass-ceramic coating aimed at protecting low-alloyed and low-carbon steels under technological heating is developed; it decreases the metal losses to scale by a factor of 12, as well as substantially decreases the decarbonizing and dealloying of the metal surface. The coating is characterized by an optimum ratio of the refractory to glasslike phases, which provides a reliable adhesion of the coating to the metal. As a result of sintering solid and liquid phases, a barrier layer forms that prevents the oxygen penetration to the metal and, hence, decelerates the corrosion processes at the coating-metal interface under heating conditions.     

To the mutual effect of surfaces of nanometallic systems and reagents in chemisorption layers

Transformations of the carbon-monoxide adsorption layers on metallic nanosystems including group VIII metals are studied with the use of Fourier-transform infra-red (FTIR) spectroscopy. Depending on the experimental conditions, not only the state of the chemisorption layers, but also the surface structure of the systems changes.     

On the problem of chromium effect on the passivability of Fe-Cr alloys

The hyperfine magnetic and electronic structure of annealed iron alloys containing 9.0, 11.8, and 12.7% chromium is studied using of Mössbauer spectroscopy. Probability distribution functions of hyperfine magnetic fields P(H_eff), mean-square intensities of the effective magnetic field H _{eff, m-sq}, average isomer (chemical) shifts δ, and other spectral parameters are calculated with the use of computer modeling. Data from Mössbauer spectroscopy are compared to the results of polarization measurements in 1 N H₂SO₄ solution at room temperature in order to find the correlation between the electronic structure and the passivability of the alloys studied.     

The effect of aggregate state of octa-(benzo-15-crown-5)-substituted phthalocyanines in aqueous solutions on the structure of self-organized composites of ultrathin ion layers

The method of layer-by-layer (LbL) deposition from aqueous solutions was used to obtain electrostatic self–organized composites consisting of cationic fragments of octa-[(4′-benzo-15-crown-5)oxy]phthalocyaninates of metals (Mcr8Pc)/K⁺ and anionic fragments of sodium polystyrenesulfonate or 4,4′,4″,4?-[cobalt phthalocyaninate-2,(3),9,(10),16,(17),23,(24)-tetrayl-tetrakis(oxy)]-tetrabenzoic acid. The electronic absorption spectra of composite coatings indicate preservation of structures formed in aqueous solutions of Mcr₈Pc: coaxial associates, noncoaxial associates, and high-order aggregates. An increase in the content of noncoaxial associates and the possible presence of suspension particles in the composite are observed.     

A study on the neck-in process by flow-forming

The neck-in process is developed to produce very small and thin cylindrical elements by flow forming machine. In this study, neck-in process is applied to the production of thin-walled combustion tube. The purpose of this study is to search for the relations among the processing parameters and find a optimal processing condition to produce precise product. For these purposes, we investigated some of the critical factors in neck-in process and processing parameters by experiment and numerical analysis. FEM analysis is carried out based on elastic-plastic work hardening model using commercially available code ABAQUS/ Standard. The results obtained from the numerical analysis and experimental data can be used to design the optimal production in neck-in process.     

Banding formation and eutectic lamellar growth in directional solidified Ni50Al20Fe30 alloy

Banding formation and eutectic lamellar growth in a directionally solidified Ni₅₀Al₂₀Fe₃₀ alloy were investigated. It was found that the banding area consists of two layers. The first layer is a γ layer, while the subsequent one is a γ layer. The composition of various phases around the banding area changes with the solidification process. The banding is formed by two steps process and caused by factors such as the fractions during the sample growth process. It was found that the band was found at relatively low growth rate. Therefore. this study indicates that increasing the growth rate is an effective method to eliminate the band formation. Eutectic lamellae nucleate and grow again after the banding formation. During the initial transition lamellar growth, the relationship between the square lamellar spacing, γ₂, and the distance from, the banding, d, can be described by the following equation: γ₂ = K [1-exp(A.d)] where K and A are constant.     

Development of sintered Ti-30mass%Mo alloy and its corrosion properties

Ti-30mass%Mo alloy is characterized by far better corrosion resistance than pure titanium in non-oxidizing acid such as 35% HC1 solution. This alloy was newly developed in this work by a powder metallurgical process, because the conventional melting-casting process had difficulties in manufacturing the alloy owing to its heavy gravity segregation. The corrosion behavior of sintered Ti-30Mo alloy was studied by both immersion test and electro-chemical measurement. The corrosion rate of 1.3X10⁻²[mm/yearxxx] was obtained by immersion test in 35% HC1 solution, which was 10³ times superior to that of pure titanium. The potentio-dynamic polarization curve of this alloy in 35% HC1 solution showed more noble corrosion potential and lower anodic current density than those of pure titanium. The passive film formed on the alloy, in which Mo was enriched by preferential dissolution of titanium, thought to suppress the anodic reaction and improve its corrosion resistance.