Žurnal neorganičeskoj himii

Finely dispersed СeO₂–Nd₂O₃ and Gd₂O₃–La₂O₃–SrO–Ni(Co)₂O_3–δ mesoporous powders are synthesized by co-crystallization of the corresponding nitrates solutions with ultrasonic treatment and used to prepare nanoceramic materials with a fluorite-like, orthorhombic perovskite and tetragonal perovskite crystal structures respectively with CSR ~ 55–90 нм (1300ºC). The study of physicochemical properties of the obtained ceramic materials revealed an open porosity 7–11% for СeO₂–Nd₂O₃ and 17–42% for Gd₂O₃–La₂O₃–SrO–Ni(Co)₂O_3–ä. Cerium oxide-based materials possess a predominantly ionic electrical conductivity with σ_700ºС = 0.31 · 10^–2 S/cm (ion transfer number t_i = 0.71–0.89 in the temperature range 300–700°C) due to the formation of mobile oxygen vacancies at heterovalent substitution of Nd³⁺ for Се⁴⁺. Solid solutions based on lanthanum nickelate and cobaltite feature a mixed electronic-ionic conductivity with σ_700°С = 0.59 ∙ 10^–1 S/cm with the electron and ion transfer numbers t_e = 0.92–0.99 and t_i = 0.08–0.01. The obtained ceramic materials are shown to be promising as solid oxide electrolyrtes and electrodes for medium temperature fuel cells.

The paper shows for the first time that 2D ZnO nanocrystals with the structure of wurtzite and Mn₃O₄ hausmanite and morphology of perforated nanoflakes can be obtained on the basis of compounds that are formed as a result of reactions occurring on the surface of aqueous solutions of acetates of the corresponding metals when it is treated in air atmosphere with gaseous NH₃. Application of the marked nanocrystals on the silicon surface makes it hydrophobic in the case of ZnO and superhydrophilic in the case of Mn₃O₄. Using the proposed synthesis technique, sequential and multiple deposition of these compounds on the substrate surface can be performed and such “multilayers” can exhibit new properties.

The review is devoted to the production of 2D graphene nanostructures (few-layer graphene) using the method of carbonization of biopolymers developed by the authors by self-propagating high-temperature synthesis (SHS). The work analyzed and generalized the experimental and some theoretical results obtained, on the basis of which a phenomenological model for the synthesis of 2D graphene structures by SHS process was proposed. The main focus is on results obtained over the past 10 years. Finally, the prospects for ongoing research on the carbonization of biopolymers are discussed. Particular attention is paid to areas of research that are expected to be of most interest for the practical use of few-layer graphene in the near future.

Nanopowders of the magnetite-maggemite series were synthesized by both aqueous precipitation and using sol-gel technology. A comprehensive comparative study of the structure of the synthesized powders was carried out using the methods of X-ray phase analysis (XPA), scanning electron microscopy (SEM), low-temperature nitrogen adsorption and small-angle polarized neutron scattering (SAPNS). It has been established that the synthesized iron oxide nanopowders are porous systems that, depending on the synthesis method, have a one-level or two-level (for powders obtained by aqueous synthesis) and three-level (for powders obtained by the sol-gel method) hierarchical structure organization with different characteristic scales and types of aggregation for each from structural levels, and the characteristic size for the larger level in both cases exceeds 45 nm. It was revealed that the magnetic structure of the obtained iron oxide powders, regardless of the synthesis method, consists of superparamagnetic particles with a characteristic magnetic radius R_М ≈ 4 nm and magnetic-nuclear cross-correlations R_MN ≈ 3 nm for powders obtained by the sol-gel method; and with R_M ≈ 5–11 nm and R_MN ≈ 4–8 nm for powders obtained by aqueous synthesis, depending on the production conditions.

Layered perovskite-like niobate CsBa₂Nb₃O₁₀ has been synthesized in a pure single-phase state for the first time using both nitrates and carbonates of cesium and barium. Unlike its Ca-, Sr- and Pb-containing analogues, the niobate obtained was shown not to undergo substitution of interlayer alkali cations with protons (protonation) upon acid treatments under various conditions. A potential reason for its chemical inactivity may consist in partial disordering of cesium and barium cations between the interlayer space and perovskite slab, hindering the interlayer ion exchange. Optical bandgap energy of CsBa₂Nb₃O₁₀, being equal to 2.8 eV, potentially allows using visible light (λ < 443 nm) for driving photocatalytic reactions. However, the photocatalytic potential of this niobate towards hydrogen production remains untapped since the activity of the interlayer space in protonation and hydration reactions, as shown earlier, is a fundamentally important factor determining the photocatalytic performance of ion-exchangeable layered perovskite-like oxides.

In present work Mn²⁺-doped MgO-Al₂O₃-ZrO₂-SiO₂ materials were synthesized. Their structure, morphology, chemical composition and luminescent properties were studied using X-Ray diffraction, scanning electron microscopy, EDX analysis and luminecent spectroscopy. It was shown that the application of sol-gel method provides the high-volume homogeneity of chemical composition of synthesized materials. Introduction of Mn into the composition of sol-gel materials accelerates significantly the crystalization processes during the thermal treatment. In the luminescence spectra several groups of emission bands are observed. These bands are situated in blue and yellow-red part of spectrum. this phenomenon is related with incorporation of Mn²⁺ into the structure of different crystals formed during the thermal treatment of gels. Obtained materials can be perspective for application as luminophores in the lighting for plant production.

The results of analysis and experimental studies of the possibilities of using synthetic aluminosilicates (montmorillonites, kaolinites, zeolites) in medicine, in particular in the field of entero- and hemosorption, in the development of targeted drug delivery systems with prolonged and pH-controlled release of the active substance in various environments, as well as components of wound dressings are presented. Montmorillonites, aluminosilicates of the kaolinite subgroup with different particle morphologies and zeolites of structural types Beta, Rho and Y were obtained under hydrothermal conditions and characterized by a complex of physicochemical research methods. The results of studying the adsorption and desorption of model drugs (thiamine hydrochloride, 5-fluorouracil) from porous aluminosilicate matrices of various chemical compositions in various media simulating body environments, adsorption of markers of endogenous intoxication (methylene blue), the ability of aluminosilicates to biodegrade in body environments, and also studies of biological activity, in particular cytotoxicity and hemolytic activity of synthetic aluminosilicates are presented. The results obtained show significant prospects for the use of synthetic aluminosilicates to obtain non-toxic, highly effective sorbents for medical use and drug carriers.

The goal of this study was to examine the phase equilibria in the La₂O₃–SrO–ZrO₂ system, which is promising as a base for the development of high-temperature ceramics and materials with unique optical, electrochemical, and catalytic properties. Thermodynamic modeling of the phase equilibria in the system under consideration was carried out using the NUCLEA database and the GEMINI2 Gibbs energy minimizer. As a result, thirteen isothermal and one polythermal sections of the phase diagram of the La₂O₃–SrO–ZrO₂ system were calculated in the temperature range 600-3023 K. The obtained data on the phase equilibria in the La₂O₃–SrO–ZrO₂ system were discussed in comparison with the known information for the corresponding binary systems. The phase relations in the system under study were shown to correlate completely with the presence of the phases present in the corresponding binary systems. Temperature changes in the phase relations and boundaries of single-phase, two-phase, and three-phase regions in the system under study were considered. Four ternary eutectic points were identified at the temperatures equal to 2039 K, 2105 K, 2120 K, and 2351 K.