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The paper presents structural, surface, thermodynamic and kinetic characteristics of titanium dioxide samples obtained by means of alkaline hydrolysis of TiCl4 by LiOH solutions and further heat treatment. TiO2 samples have the anatase structure with crystallite size of 7–10 nm. An increase in the heat treatment temperature from 150 °C to 470 °C leads to a decrease in the specific surface area from 404 to 80 m2/g and the total pore volume from 0.340 to 0.152 cm3/g. The influence of electrolyte composition and surface properties of TiO2 on its behavior in cells with lithium anode investigated by means of galvanostatic cycling and impedance spectroscopy is discussed.

Citrate precursors of copper, nickel and cobalt oxides, namely Cu(C6H7O7)2·5H2O, Ni(C6H7O7)2·2.5H2O and CoC6H6O7·6H2O, have been synthesized from solutions with metal to citric acid ratio of 1:2, their thermal decomposition has been studied, and decomposition products have been analyzed. It has been found that the Cu salt loses water and then forms acidic aconitate and acidic itaconate, which then transforms to normal itaconate and further to CuO. The Ni salt dehydrates and decomposes directly to normal itaconates and then to NiO mixed with Ni metal. The Co salt dehydrates and then transforms to normal aconitate, normal itaconate and to Co3O4 containing CoO. While the oxides in question form crystallites of 15–25 nm size with pores of around 3–4 nm in radii, their morphology differs significantly. CuO particles are nanosized. Unlike them, NiO and Co3O4 develop aggregates of approx. 300–500 nm size. Similarities and differences in decomposition processes and morphology of the target oxides are analyzed and discussed, and possible improvements of the citric acid-aided route are suggested. It is shown, in particular, that the formation of metallic Ni and CoO is predetermined by thermodynamics of redox processes involving oxygen and carbon monoxide obtained by the decomposition of the organic part of precursors.

Еlectrochemical performance of Co 3 O 4 in lithium-ion batteries is briefly reviewed. Co 3 O 4 samples are synthesized via microwave-assisted solid state and citric acid aided methods. It is shown that the latter method leads to disperse nanosized materials having discharge capacity close to the theoretical value. Several electrolytes are probed so as to minimize capacity losses upon cycling, and the one containing lithium bis(trifluoromethane)sulfonimide in a mixture of fluoroethylene carbonate and dimethyl carbonate is selected. High-rate tests reveal that capacity retention of the samples obtained is well comparable with the best existing data, and at the current load of 5340 mA g −1 (6C) all materials studied retain more than 50% of initial capacity.

Overdischarge poses a significant threat to the safety and reliability of lithium ion batteries. In this paper, overdischarge (overlithiation) effect on electrochemical parameters of lithium manganese spinels of different origin is studied. Charge/discharge tests for 240 cycles are performed within recommended and lowered potential ranges. Insertion of lithium ions into spinels by decreasing potential to either +2.4 or +1.5 V against Li/Li+ is found to lead to the formation of the overlithiated Li2-x Mn2O4 spinel phase. Repeated cycling involving the low-potential regions worsens electrochemical parameters: cell resistance increases and specific capacity decreases. It appears that even small overdischarge is totally unacceptable for the nanosized home-made samples and microsized EQ–Lib–LMO (MTI) samples. The microsized BE–30 (NEI) sample better tolerates cycling at lowered potentials. The greatest resistance to overdischarge demonstrates the aluminum-doped microsized HPM–9051C (Toda) sample. Being treated at lowered voltages, this material acquires a steady trend towards an increase in specific capacity by half. This may signify that at least half of the gram equivalent of extra lithium ions can be electrochemically inserted into the 16с voids in the spinel structure resulting in the Li1.5Mn2O4 compound, which is able to reversibly work within the 2.4–4.6 V potential range.

Anthropogenic air pollution attracts attention of scientists and the public around the world for many years. Traveling over vast distances, particles and aerosols pollute the environment many kilometers away from emission sources. Primary anthropogenic aerosols enter the air mainly with industrial emissions from factories. Secondly aerosols are formed in the atmosphere through various physical and chemical processes involving water vapor, organic compounds, etc. This group includes sulphur dioxide. The article discusses issues related to the pollution of the environment as a result of the activities of the copper-nickel plant Severonickel, located on the Kola Peninsula. In particular, the problem of accumulation of sulfur compounds in the soil, which occurs over decades at a different distance from the industrial factory. Sulphur dioxide is a toxic substance, at high concentrations in the air there is a harmful impact on living organisms, precipitation leads to acidification of the soil, disturbance of soil and vegetation cover, changes balance and destroy ecosystems. For this reason, it is important to monitor the condition of ecosystems that are under the influence of industrial plants. This issue is dedicated to the work of researchers and students of the Department of Environmental Management of the Faculty of Geography of Lomonosov Moscow State University, who for more than twenty years have been monitoring the state of ecosystems in the impact zone of Severonickel plant, including a number of studies devoted to pollution of the soil with sulfur compounds.

Our recent Raman studies of cation and anion solvation and ion pairing in solutions of lithium salts in dimethyl sulfoxide, propylene carbonate, and dimethyl carbonate are briefly overviewed. Special attention is paid to differences in our and existing data and concepts. As follows from our results, cation solvation numbers in solutions are low (~2) and disagree with previous measurements. This discrepancy is shown to arise from correct accounting for dimerization, hydrogen bonding, and conformation equilibria in the solvents disregarded in early studies. Another disputable question touches upon the absence of free ions in solutions of lithium salts in carbonate solvents and the statement that the charge transfer in carbonate solutions is caused by SSIPs. Direct proofs of the nature of charge carriers in the solvents studied have been obtained by means of analyses of vibrational dynamics. It has been found that collision times for free anions are short and evidence weak interactions between anions and solvent molecules. In SSIPs, collision times are an order of magnitude longer thus signifying strong interactions between anions and cations. In CIPs, collision times become shorter than in SSIPs reflecting the transformation of the structure of concentrated solutions to that of molten salts.

Phase diagrams of lithium salt systems in dimethyl sulfoxide, propylene carbonate and dimethyl carbonate have been obtained and conductivity measurements have been performed in the concentration range up to 0.25 mole fraction of a salt. The shape of the phase diagrams has been analyzed thermodynamically and the following order of anions for decreasing association of salts with DMSO at cLiX = 0.2 has been suggested, ClO4− > CF3SO3− > BF4− > NO3−. The eutectic-type phase diagrams of the LiClO4-PC and LiClO4-DMC systems correspond to ideal, non-interacting solutions. The conductivity isotherms for the DMSO solutions at cLiX = 0.2 are arranged in the order of increasing conductivity as CF3SO3− c LiClO 4 = 0.5–1 mole fraction of the salt, the order of solvents for increasing conductivity is DMC

Raman study of cation and anion solvation in dimethyl sulfoxide, propylene carbonate and dimethyl carbonate solutions of six lithium salts has been performed in the concentration range from 0.05 to 0.25 molar fraction of a salt. The dependences of the amount of the solvent particles involved in dimerization, hydrogen bonding, and solvation have been determined, and the mean solvation numbers have been found. It is concluded that in all solutions studied, notwithstanding the differences in the physical properties of the solvent and in the structure of the anion, both the lithium cation and the anion solvation equilibria are quantitatively similar. In all cases, solvation numbers of cations are close to two and do not vary with the growth of concentration. In particular, in molten LiX·4S solvates, LiS 4 + entities expected from the phase diagrams do not exist. It has been found that for the solvent molecules in dimers and in solvation spheres, non-coincidences between vibrational frequencies of isotropic and anisotropic lines, Δ ν NCE = ν aniso − ν iso are of opposite signs signifying that the mutual orientation of molecules is different. In all systems studied, solvation numbers of anions decrease if the salt content is growing and are close to four in concentrated solutions. These striking similarities in the structure and concentration of solvated entities clearly signify that solvation phenomena have no decisive importance in determining the properties of salt systems.

In order to successively compete with supercapacitors, an ability of fast discharge is a must for lithium-ion batteries. From this point of view, stoichiometric and substituted lithium manganese spinels as cathode materials are one of the most prospective candidates, especially in their nanosized form. In this article, an overview of the most recent data regarding physico-chemical and electrochemical properties of lithium manganese spinels, especially, LiMn 2 O 4 and LiNi 0.5 Mn 1.5 O 4 , synthesized by means of various methods is presented, with special emphasis of their use in high-rate electrochemical applications. In particular, specific capacities and rate capabilities of spinel materials are analyzed. It is suggested that reduced specific capacity is determined primarily by the aggregation of material particles, whereas good high-rate capability is governed not only by the size of crystallites but also by the perfectness of crystals. The most technologically advantageous solutions are described, existing gaps in the knowledge of spinel materials are outlined, and the ways of their filling are suggested, in a hope to be helpful in keeping lithium batteries afloat in the struggle for a worthy place among electrochemical energy systems of the 21st century.

The citric acid aided synthesis, physico-chemical and electrochemical characterization of the nanosized nickel-doped lithium manganese spinel, LiNi 0.5 Mn 1.5 O 4 having excellent high-rate properties is described. An optimal electrode material represented by perfectly shaped, well-faceted particles of 100-400 nm size containing crystallites of the 15-22 nm size could be obtained upon the thermal treatment at 700 °C. In spite of a reduced specific capacity (102 mAh·g −1 ) it is able to retain a half of it upon the discharge current of 4400 mA·g −1 (30 C) and to endure the current load of 5870 mAh·g −1 (40 C) delivering the reversible specific capacity of 25 mAh·g −1 . It is suggested that the reduced specific capacity is determined primarily by the aggregation of material's particles, whereas the good high-rate capability is governed not only by the size of crystallites but also by the perfectness of crystals, and imperfections in big, well-shaped crystals (like dislocations, grain boundaries, etc.) less retard the diffusion of lithium ions than particle boundaries in small, randomly oriented, accreted crystals.

The Raman spectra of the mixtures containing the low-temperature ionic liquid ethylmethylimidazolinium bis(trifluoromethanesulfonyl)imide (EMIIm), the salt component lithium bis(trifluoromethylesulfonyl)-imide (LiIm), and the aprotic solvent ethylene carbonate (EC) are studied. It is found that the addition of the lithium salt to the ionic liquid results in the formation of ion pairs or more complex cation-anion aggregates. Dilution of these systems with ethylene carbonate leads to the solvation of lithium ions.

An analysis of the Raman spectra of the solutions of lithium salts in dimethyl sulfoxide, propylene carbonate, and dimethyl carbonate in a concentration range from diluted solutions to the mixtures of molten solvates with salts has been performed in terms of the dynamics, specifically, the dephasing (тv) and modulation (тw) times of all molecular entities present in solutions are determined and analyzed. It has been found that, in the picosecond time domain, the dephasing and modulation in solvent molecules hydrogen-bonded with an anion and/or solvating a cation are slower than in free solvent molecules. In solvent separated ion pairs, both тv and тw are much longer than in solvated anions, thus indicating the strong interactions between anions and their surrounding. In contact ion pairs, тv are great, whereas тw appear close to those for free anions. This reflects that the structure of the liquid tends to the structure of molten salts.

This work reports phase diagrams, conductivity isotherms, and data regarding the structure and dynamics of systems formed by lithium perchlorate and nitrate as solutes and sulfones as solvents. The LiClO4 + (CH3)2SO2 system behaves like typical electrolytic systems containing a lithium salt and a solvent and forms a 1:1 solvate; its conductivity isotherm demonstrates a maximum. Unlike typical systems, the phase diagrams of the LiNO3 + (CH3)2SO2 and LiNO3 + (C2H5)2SO2 systems appear to be simple eutectic. The dependences of specific conductivity on the concentration of LiNO3 are also uncommon showing no maximum characteristic to electrolyte solutions. Raman studies and analysis of dynamics performed using Raman data signify that, in the LiClO4 + (CH3)2SO2 system, solvated cations and contact ion pairs exist. In the LiNO3 + (CH3)2SO2 system, contact ion pairs are present as well, but signatures of cation solvation cannot be found.

The possibility of preparing lanthanum(III) hydroxide and a 1:1 mixture of lanthanum(III) hydroxide with hydrated titania by precipitation from aqueous solutions was explored. The maximal sorption capacities of the mixture with respect to phosphate ions in acid and alkaline media were determined. The mechanism by which phosphates are removed was elucidated by IR spectroscopy.

The oxidation of aqueous solutions of manganese (II) chloride by hydrogen peroxide leads to the mixture of hausmannite (Mn3O4) with manganite (MnOOH). Being air dried, this mixture undergoes slow oxidation at room temperature during which the content of manganite is rising, and an equilibrium molar ratio Mn3O4:MnOOH reaches 1:3 in approx. 1 year of storage. In terms of reversible first order reactions, rate constants for the forward and reverse reactions are 2.62 × 10−1 and 8.75 × 10−2 month−1, respectively. In the course of oxidation, additional IR adsorption bands emerge in the region of vibrations of physisorbed water molecules at 3160 and 3300 cm−1. These bands are absent in IR spectra of equilibrium mixtures and disappear after treatment of samples with Sr2+ ions as a result of ion exchange. This finding enables one to suggest that adsorbed water forms cation exchangeable surface groups Mn (OH)2 whose transformation into MnOOH is a step determining the oxidation rate. On the other hand, these data may be considered as the first spectroscopic evidence of sorption of spherical cations onto the surface of hydrous oxides.

The anodic formation of manganese dioxide is studied voltammetrically in a wide range of potential scan rate (V = 0.001–8 V/s). Using the diagnostic criteria of cronovoltammetric method, based on the original experimental data, the mechanism of electrooxidation of manganese ions in the acidic medium with subsequent reaction of disproportionation of the product of irreversible electrode reaction and hydrolysis yielding manganese dioxide is proposed. The kinetics of cathodic reduction of electrolytic manganese dioxide in the 0.5 M Na2SO4 solution is studied under the steady-state and non-steady-state potentiodynamic polarization conditions. From the experimental data, it is found that, in the acidic medium (pH 1–3), the mechanism of the electrode process changes depending on the cathodic potential scan rate: at the scan rate V < 0.5 V/s, MnOOH forms via one-electron transition leading, in its turn, to the partial deactivation of electrode surface with subsequent disproportionation of manganite. At the relatively high potential scan rates, manganite has no time to form, and the two-stage reduction via one-electron transitions at each stage is well pronounced. The parameters of the electrode processes are calculated.

Corrosion and adsorption properties of manganese dioxide, which was anodically deposited on platinum, its powder, and compacted tablets of manganese dioxide in the solutions with various pH values are studied using various experimental methods. It is shown that the corrosion rate of manganese dioxide decreases with increasing pH of solution, and the process proceeds by the electrochemical mechanism with conjugate chemical reactions of the formation and decomposition of the product of transition stage. The adsorption properties of manganese dioxide powder with respect to copper ions increase with increasing pH of solution, whereas the amount of manganese ions passing to the solution almost vanishes at pH 9.

Complex formation of zinc(II) with citric acid in acidic medium was studied by pH-potentiometric titration at various metal to acid ratios. The speciation diagrams of the complexes in relation to pH were plotted, and the stability constants of the complexes were determined. Precursors of the synthesis of metal oxide materials were prepared at two reactant ratios. A scheme of the precursor thermal decomposition based on data of derivatography and IR spectroscopy was suggested, and the compositions of compounds formed during decomposition were determined.

Samples with the best adsorption properties are selected as a result of investigations conducted on synthesis of manganese-dioxide-based materials and study of their physicochemical properties. Materials were selected on the basis of their low cost and the simplicity of their production technology. In the laboratory the synthesis and analyses of materials was carried out for selected samples. The sorption of a series of elements is studied for a more detailed investigation of materials obtained. The results obtained will promote the synthesis of materials with improved adsorption properties with the aim of their application for purification of water from strontium. It is shown that the most promising way for amendment of manganese oxide is modification of this material using acid-resistant oxides. These oxides are also less expensive than existing sorbents for strontium.

Hydrous, amorphous MnO2–TiO2 composites demonstrating high affinity towards strontium and uranium at pH = 7 are obtained by means of template synthesis. The best distribution coefficients, as found using model solutions (K d Sr = 55000 mL/g and K d U = 40000 mL/g) and Chernobyl shelter water (K d Sr = 3800 mL/g), are gained for the samples containing equimolar amounts of manganese dioxide and titania precipitated using K+ as template cation.

The paper deals with several novel approaches to the studies of interactions and dynamics in liquids. A new, flexible time-correlation function is introduced. It has an analytical counterpart in the frequency domain and enables one to fit even badly overlapped vibrational line profiles obtaining dynamical information at the same time. As examples, quantitative description of the interaction potential in molten salts containing halide complexes of zinc and manganese is presented, the dynamic criterion of complex entities in a melt is introduced, and the spectroscopic features of molten alkali and alkaline earth halides are explained in terms of short-lived collision complexes. Finally, the model treatment of "anomalous" noncoincidence effects in liquids is discussed, and the contribution of repulsion and attraction forces resulting in frequency non-coincidences is separated.

Lithium manganese spinels tend to aggregate upon annealing and do not allow for attaining high discharge rates when used as cathodes in lithium-ion batteries. To obtain spinel samples of lower aggregation and better high-rate properties, precursors synthesized by means of a citric acid-aided route are suggested to be pyrolyzed in an inert atmosphere, instead of pyrolysis in air. The synthesis of nanosized Li[Li0.033Mn1.967]O4 is described, and its characteristics including X-ray diffraction, scanning electron microscopy, and porosity, as well as electrochemical test results are presented. The particle size of the materials obtained is smaller, the degree of aggregation is lower, and high-rate properties are better than for analogues pyrolyzed in air. In particular, sample Li||Li[Li0.033Mn1.967]O4 cells deliver ~60 mAh g−1 at the current loads of 4,000 mA g−1 (30 C). After a sequence of 62 charge/discharge cycles with the currents growing from 0.1 to 100 C the specific capacity retains its initial value.

Hydrous, amorphous manganese oxide/titanium oxide composites (AMTO) obtained via template synthesis using alkali metal ions as templates have been characterized. Their applicability in remediation technologies has been tested, specifically for 90 Sr removal from Savannah River Site high-level waste supernatants (SHLW) and Chernobyl 4th Block Shelter water (CSW) simulants. Sorption isotherms were used to establish the efficiency of the templating process, while the proton-exchange capacity of AMTO was determined to show that the solids were really protonated. Use of the 90 Sr isotope showed that there was little dependence of the distribution coefficients for AMTO on pH, and at pH < 7, i.e., in neutral and acidic media, AMTO had a much greater affinity for strontium than commercial sorbents. Tests with SHLW and CSW simulants revealed that AMTO is capable of removing more than 99% of 90 Sr from such wastes. Hence, it could be useful for solving decontamination problems.

A comparison of the behaviour of commercial electrochemical manganese dioxide (γ-MnO 2 ) and non-stoichiometric anodic Mn x O y (OH) z was made. Anodic oxide proves to be composed mainly by MnO 2 (ramsdellite) and MnOOH (manganite), and contains more water and OH − than γ-MnO 2 . Hydroxide ions were shown to determine the ionic conductivity of Mn x O y (OH) z which, in turn, strongly affects the rate of electroreduction.

The species yields and velocity distributions in the vacuum plume of laser ablated pirolitic graphite were studied in detail by the time-of-flight mass spectrometry methods. Integral mass deposition on the opposite substrate was also investigated by use of quartz microbalance. At laser energy density near 2 J/cm2 high yield of evaporation of clusters C7 - C27 is revealed. It is substantially higher in the case of preliminary ground graphite as compared with laser treated samples. First irradiation shots of a fresh graphite sample reveal the highest yield of C7 - C27 clusters and do not reveal a detectable number of fullerenes in the plume. Fullerenes are more abundant in the case of target rotation or laser spot displacement. Fullerene evaporation yield increases during a certain time period of laser ablation of moving graphite target. Two- stage character of fullerenes appearance in the plume is proposed. Firstly high mass clusters are formed in the plume tail -- the most cool part of the plume. As the pressure in the hot plume body is higher, most of the fullerenes formed deposit back on the target surface. Next laser pulses evaporate these clusters, which are stable enough to stand in the hot plume body. The C7 - C27 cluster ions are proposed to be mainly produced as a result of ejection of the pieces of graphite slices.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.