Perovskite nanomaterials based on LaMnO3+delta doped with alkali metals are effective and inexpensive catalysts for the oxidation of soot, a byproduct of the incomplete combustion of fuels or organic compounds. Present study examines the synthesis characteristics and properties of the La(0.9)A(0.1)MnO(3+delta) (A=Li, Na, K, Rb, Cs) catalysts for soot oxidation with atmospheric oxygen as a function of the crystallographic radii and electronegativity of the alkali dopants in the perovskite A-site. Correlations are established between the combustion temperature of the initial precursors, the intensity of the electrical charges generated in the precursors during combustion, the specific surface area of the resulting complex oxides, and the activation energy of the catalytic oxidation of carbon black. The relationship between the above parameters and the ionic radius and electronegativity of the dopants is also considered. It is shown that in the presence of the LaMnO3+delta-based catalysts: 1) the concentration of released carbon(II) oxide is reduced by >50 times, 2) soot is more completely oxidized to CO2, and 3) the degree of soot conversion increases when the catalyst is applied to the nickel foam support.

The development and characterization of synthesis techniques for oxide materials based on ceria is a subject of extensive study with the objective of their wide-ranging applications in pursuit of sustainable development. The present study demonstrates the feasibility of controlled synthesis of Ce1−xMxO2−δ (M = Fe, Ni, Co, Mn, Cu, Ag, Sm, Cs, x = 0.0–0.3) in combustion reactions from precursors comprising glycine, polyvinyl alcohol, polyvinylpyrrolidone, polyethylene glycol, and cellulose as organic components. Controlled synthesis is achieved by varying the composition of the precursor, the type of organic component, and the amount of organic component, which allows for the influence of the generation of high-density electrical charges and outgassing during synthesis. The intensity of charge generation is quantified by measuring the value of the precursor–ground potential difference. It has been demonstrated that an increase in the intensity of charge generation results in a more developed morphology, which is essential for the practical implementation of ceria as a catalyst to enhance contact with gases and solid particles. The maximum value of the potential difference, equal to 68 V, is obtained during the synthesis of Ce0.7Ni0.3O2−δ with polyvinyl alcohol in stoichiometric relations, which corresponds to a specific surface area of 21.7 m2 g−1. A correlation is established between the intensity of gas release for systems with different organic components, the intensity of charge generation, morphology, and the value of the specific surface area of the samples.

The generation of electric charges during the combustion of nitrate organic precursors in the synthesis of strontium hexaferrite SrFe12O19-based complex oxide materials, including those doped with lanthanum and cobalt ions, was established. The precursors included polyvinyl alcohol or glycine. The intensity of charge generation was lower for precursors containing a larger amount of the organic component. Magnetic characteristics of the samples (magnetization, coercive field) were measured. An external magnetic field applied during the hexaferrite synthesis significantly affected the coercive field of the samples, which could be increased via the formation of extended ensembles of nanoparticles. The effect was more pronounced for samples with a moderate level of charge generation. The relationship between the factors influencing the formation of extended aggregates was analyzed. The maximum coercive field was found for Sr0.8La0.2Fe11.8Co0.2O19. One way to increase the coercive field is a two-stage magnetic heat treatment including a low-temperature stage. The formation of branched extended structures at the macro- and micro-levels was found during the combustion of glycine-containing precursors.

The aim of this work is to establish the relationship between the electrochemical performance of the Pr 1.6 C & acy; 0.4 Ni 0.6 Cu 0.4 O 4+delta- based electrodes and the properties of the electrode powders, conditioned by their synthesis history, as well as the electrode design and the sintering conditions of the electrode layers. The Pr 1.6 C & acy; 0.4 Ni 0.6 Cu 0.4 O 4+delta (PCNCO) powders are synthesized by combustion of salt compositions using different fuels: glycine, polyvinyl alcohol and citric acid. The influence of the composition of the redox mixture on the synthesis process, the phase composition of the obtained powders and their properties have been studied. The microstructure of the PCNCO electrodes formed from the powders with different dispersions is studied by electron microscopy. The electrochemical performance of the electrodes in contact with the Ce 0.8 Sm 0.2 O 1.9 (SDC) electrolyte is studied by impedance spectroscopy. Based on the correlations established between the chemical stability and dispersion of the powders and the microstructure and polarization resistance of the corresponding electrodes, the optimal parameters for the synthesis of the PCNCO complex oxide for the use as a cathode material have been determined. The lowest polarization resistance equal to 0.38 Omega cm2 2 at 700 degrees C is obtained for the bilayer electrode with the PCNCO functional layer synthesized by the citrate-nitrate combustion and sintered at 1050 degrees C, and the LaNi 0.6 Fe 0.4 O 3-delta oxide collector sintered at 900 degrees C. The developed synthesis procedure and electrode design can be recommended as promising for the fabrication of air electrodes in the intermediate- temperature electrochemical devices.

The mutual influence of the process of electric charge generation in nitrate organic precursors and a constant external magnetic field on the magnetic properties formation was considered for lanthanum strontium manganite La0.7Sr0.3MnO3 +/- y powders obtained via combustion reactions. The investigated properties of the obtained samples include hysteresis, magnetocaloric and magnetoresistive effects. The correlation between formation process of extended ensembles of nanoparticles and the functional properties of complex oxide materials was also discussed. The manifestation of a strong magneto-gas-selective effect has been observed during the combustion of precursors in a constant magnetic field, which affects the charge generation process.

As an initial sample of aluminum oxide, we used material of industrial production for the manufacture of ceramic products. Aluminum oxide powders were prepared as additives introduced into the basic material in an amount of 3% by mass obtained by electric wire explosion as well as in combustion reactions of nitrate-polymer precursor based on polyvinyl alcohol. The obtained additives were characterized in terms of the structure and particle morphology. The samples of the first type included a mixture of different modifications of aluminum oxide, the second type included hydrated aluminum oxide. The first two samples consisted mainly of unaggregated spherical nanoparticles with specific surface area of 20 and 69 m2/g, and the powder obtained in combustion reactions contained flat flake particles, it had a specific surface area of 8 m2/g. The introduction of nano-sized additives led to a shift of the dilatometric sintering curve of compacted samples to lower temperatures, up to 140 degrees maximum. The sample with the largest specific surface was more active in lowering the sintering temperature. The result obtained for the pyrolytically synthesized additive was comparable with the above-mentioned shift in the sintering curve.

The processes of strontium hexaferrite (permanent magnet material) fabrication in combustion reactions followed by heat treatment of organic nitrate precursors containing glycine or polyvinyl alcohol have been studied. The formation of iron-glycine complexes of organic precursor components affects the formation of the morphology of the obtained samples. When using glycine-containing systems during combustion, a branched fibrous texture of the material with extended internal cavities with elongated oxide particles emerges. Such samples have a higher coercivity; the external magnetic field has no significant influence on the texture formation during combustion. It was established that charges are generated in precursors during their combustion, which manifests itself in the appearance of a potential difference between the ground and the precursor. In this case, the appearance of lower intensity charges allows us to obtain samples with higher magnetization, as well as with a greater ability to increase the magnetic characteristics during further thermomagnetic processing.

Features of processes for the synthesis of nanosized complex perovskite-type oxides (lanthanum manganite) and doped cerium dioxide in combustion reactions of nitrate–polymer precursors under conditions of high-density electrical charges generation have been studied. Effect of external electromagnetic field on charges generation allowing change in the sign and magnitude of precursor charge has been established. It has been shown that the labile oxidation state of metals comprising resulting oxides is the requirement for charges generation. Examples of aluminum and zirconium oxides illustrate this conclusion by the absence of charges during precursors combustion. Inert (N 2 ) or reducing atmosphere (N 2 + CO) prevents the reversible oxidation of manganese ions in perovskite and cerium in dioxide, which in turn prevents charges formation. Addition of nitrogen (NО) and carbon oxides (CO) to nitrogen as combustion medium that suppresses charges formation does not result in their increase, hence, charges appear immediately when molecular species form during combustion. Metal carriers of precursors decrease accumulated charge due to higher electric capacity, while porous carriers also provide charge dissipation.

Исследованы образцы частично окисленного микро- и нанопористого железа, полученного методом высокотемпературного деаллоинга железо-марганцевого сплава в солевом расплаве. При помощи электронной микроскопии получены данные о морфологии образцов и составе их поверхности, установлено, что уже после отмывки при комнатной температуре на воздухе образовались оксидные фазы железа в виде вискеров толщиной порядка 10 нм. В ходе получения образцов достигалось количественное удаление марганца из исходного сплава. Оценена каталитическая активность полученных образцов в гетерогенной реакции Фентона по окислению красителя метилового оранжевого пероксидом водорода. На первом этапе протекания реакции, описываемой уравнением реакции первого порядка, ее скорость определялась наиболее активной расходуемой частью образцов, далее реакция переходила в стационарный режим. Более высокой каталитической активностью обладали нанопористые образцы. The samples of partially oxidized micro- and nanoporous iron obtained by high-temperature dealloing of an iron-manganese alloy in a molten salt were investigated. The data concerning the structure of the samples and the composition of their surface were obtained by electron microscopy; it was found that after washing at room temperature in air the oxide phases of iron were formed as whiskers with a thickness of about 10 nm. During the preparation of the samples a quantitative removal of manganese from the initial alloy was achieved. The catalytic activity of the obtained samples in the heterogeneous Fenton reaction was estimated by oxidation of methyl orange by hydrogen peroxide. The rate of the first stage of the reaction, which was described by the first-order equation, was determined by the most active spent part of the samples, and then the reaction passed into the stationary mode. The nanoporous samples possessed a higher catalytic activity.

The Sr2Ni0.7Mg0.3MoO6-delta double perovskites synthesis has been performed by a pyrolysis of organic-nitrate compositions with various ratios of f (glycerol-or glycine content) and R (ammonium nitrate content). The solution combustion study revealed that the redox mixture composition for the Sr2Ni0.7Mg0.3MoO6-delta synthesis influenced the pyrolysis temperature, thermochemical charge generation, particles size, phase composition and physicochemical properties of the final oxide material. Investigations of thermodynamic stability, thermal expansion and electrical conductivity demonstrated that the Sr2Ni0.7Mg0.3MoO6-delta sample, obtained via pyrolysis synthesis with glycine triple excess without exothermic additive, may be considered as a prospective anode material for intermediate-temperature solid oxide fuel cells. It was confirmed by the sample stability in oxidative and reducing atmospheres, optimal values of linear coefficient of thermal expansion (14.4.10-6 K-1 in air; 13.1.10-6 K-1 in 50% H-2/Ar) and the highest electrical conductivity value (0.53 S cm(-1) at 800 degrees C in air) among glycine-samples. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Complex oxides on the basis of LaMnO3 +/- y were obtained via combustion of precursors containing nitrates and soluble organic agents (polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide, polyethylene glycol, cellulose; glycine, glycerine and citric acid). The phenomenon of charge generation processes during the synthesis was analysed by measuring the potential difference between the ground and precursor. It was proposed that one of the main factors determining the processes of charge generation is the release of gaseous molecular charged particles into the environment. The maximum value of generated charges was fixed for polyvinyl alcohol containing precursors and the lowest for glycine containing ones. The composition of the initial precursors (used organic component and the phi value) effects the maximum temperature achieved during synthesis (300 x25e6;C-1100 x25e6;C), concentration of released gases (50-600 ppm (CO), 250-2800 ppm (NO)) and the potential difference between the ground and precursor. The dependence of specific surface area (7.5-21 m2/g), the temperature of the beginning of the intense sintering (750 x25e6;C-1150 x25e6;C) and the maximum achievable shrinkage (5-21%) on the value of measured potential difference in precursors was shown. The established regularities allow expanding ability for the production of complex oxide materials with the specified properties.

The solution combustion synthesis of iron oxides from nitrate solutions with a dual fuel comprising urea and citric acid on the earlier synthesized FeOx powder was studied. The possibility of the synthesis of up to 100 g of the desired product under laboratory conditions in a relatively small (4 dm3) reactor was demonstrated for the first time. The obtained nanodisperse materials were a well-crystallized mixture of Fe3O4 and α-Fe2O3 oxides. A consistent increase in the weight of the FeOx powder led to an increase in the mass fraction of the α-Fe2O3 phase to 91% at the final stage of the synthesis.

The indication of affiliation of the second author should read:

The indication of affiliation of the second author should read:

Double perovskite Sr2Ni0.75Mg0.25MoO6-δ powders were synthesized by the combustion method using systems containing nitrates and varying amounts of the following organic components: glycine, glycerol, and polyvinyl alcohol. The characteristics (temperature, gas composition, etc.) of the synthesis process were studied and the optimal conditions for obtaining single-phase samples were determined. It was established that the usage of one-and-a-half excess of glycerol as organic component provides the formation single-phase complex oxide. The crystal structure of the obtained complex oxide, which is of interest as an anode material for solid oxide fuel cells, was refined and its physico-chemical properties (specific surface area, particle size, electrical conductivity, and catalytic activity in the reaction of methane oxidation) were investigated.