M. V. Kalinina

Liquid-phase synthesis and physicochemical properties of xerogels, nanopowders and thin films of the CeO2–Y2O3 system

Low-agglomerated xerogels, ultrafine oxide powders with particle sizes of 12–20 nm, and uniform thin films with particle sizes of 8–14 nm are prepared in the CeO2–Y2O3 system using liquid-phase low-temperature methods, namely via coprecipitation of hydroxides and cocrystallization of salts, sol—gel technology. A comparative characterization of the prepared xerogels and nanopowders is performed using a set of physicochemical analytical methods. A dependence of phase composition, microstructure, and particle size on synthetic parameters is elucidated.

Study of the effect of methods for liquid-phase synthesis of nanopowders on the structure and physicochemical properties of ceramics in the CeO 2 –Y 2 O 3 system

Two alternative chemical synthesis methods—cryotechnological coprecipitation of hydroxides and cocrystallization of salts—were used for preparing (CeO2)1–x(Y2O3)x nanopowders (x = 0.10, 0.15, 0.20) with a mean coherent scattering domain size of ~7–11 nm and Ssp = 2.1–97.5 m2/g. From these nanopowders, ceramic nanomaterials with mean coherent scattering domain sizes of ~61–85 nm were synthesized. It was studied how the phase composition, microstructure, and electrical transport properties of the produced samples depend on the Y2O3 content of a CeO2-based solid solution and on the synthesis method. It was shown that, in the series (CeO2)1–x(Y2O3)x (x = 0.10, 0.15, 0.20), the solid solution (CeO2)0.90(Y2O3)0.10 has the highest ionic conductivity with the ion transport number ti = 0.73 (600°C). In its physicochemical characteristics, this ceramic can be used as a solid electrolyte of intermediate-temperature fuel cells.

Electroconducting ceramics based on In2O3, CdO, and LaCrO3

The possibility of fabricating electroconducting (101–104 S cm–1) ceramics based on In2O3, CdO, and LaCrO3 by liquid-phase synthesis methods has been demonstrated. The results of studies of the effect of temperature, dopants, and partial oxygen pressure on the specific electroconductivity of ceramic composites are presented.

NiMn2O4 spinel as a material for supercapacitors with a pseudocapacity effect

Nanopowders of the NiMn2O4 spinel of a grain size of about 30 nm are obtained by the method of coprecipitation. The specific capacity in an aqueous electrolyte (1 М LiNO3) is determined by the method of cyclic voltammetry. Using computer simulation, the peculiarities of the mechanism of intercalation of Li+ into a NiMn2O4 spinel are studied by the method of crystal chemical analysis.

Preparation and Characterization of Nanoceramics for Solid Oxide Fuel Cells

Precursor powders in the ZrO2–HfO2–Y2O3–CeO2, In2O3–ZrO2, and NiO–Nd2O3 systems for components of solid oxide fuel cells have been prepared by liquid-phase synthesis. We have determined formation conditions and the particle size of ZrO2- and In2O3-based solid solutions and neodymium nickelate (Nd2NiO4), demonstrated the feasibility of producing nanocrystalline powders (10–30 nm) of tailored chemical composition in the temperature range 500–900°C, and optimized powder consolidation conditions. Nanoceramics with a crystallite size from 60 to 90 nm have been obtained and their microstructure and phase composition have been investigated. We have studied the electrical properties of the ZrO2- and In2O3-based solid solutions and the Nd2NiO4 compound and established the range of their electrical conductivity at temperatures from 300 to 1000°C: 2.27 × 10–3 to 2.51 S/cm for the ZrO2-based solid solution, 8.91 × 101 to 6.59 × 103 S/cm for the In2O3-based solid solution, and 3.98 × 102 to 5.02 × 102 S/cm for Nd2NiO4.

Synthesis and Physicochemical Properties of Nanopowders and Ceramics in a CeO2–Gd2O3 System

Nanopowders with a composition of (СeO2)1–x(Gd2O3)x (x = 0.03, 0.05, 0.07, and 0.10) are synthesized by the coprecipitation method using cryotechnologies. The coherent scattering region (CSR) of the powders is 10–14 nm and the specific surface area is 70–81 m2/g. Based on the powders, ceramic nanosized materials with CRS of 64–71 nm are obtained. The dependence of the phase composition, microstructure, and electrical transport properties of the obtained samples on the Gd2O3 content is established. In a CeO2–Gd2O3 system, a solid solution with the composition of (CeO2)0.90(Gd2O3)0.10 has the highest ionic conductivity with the transfer number of ions of ti = 0.74 at a temperature of 700°C. It is shown that ceramics of this composition can be used as a solid electrolyte of intermediate-temperature fuel cells due to their physicochemical characteristics.

Computational Identification of a New Form of Li 2 MnSiO 4 for Battery Applications

The reversibility of phase transformations in Li2MnSiO4 and related materials during charge/discharge of the material is an important factor to enable the practical application of the cathode materials. However, the stability of this material is still unattainable. Here we report the computational identification of a new form of Li2MnSiO4 as a stable candidate with acceptable characteristics. The stability could arise due to the presence of the three-dimensional structure of the inorganic framework. The presence of a structure with a compact unit cell forms the basis for high capacity. Surprisingly it was found to have a stable analogue occurring in nature – Na2CaSiO4 with the same structure. Using this information the possible routes of obtaining such material are presented. The prediction of such material has been not found in the literature previously. Of course the problems such as phase transformations upon delithiation may exist, and to check the data the experimental and computer studies needed.

Preparation and properties of porous ceramics based on alumomagnesium spinel and zirconium dioxide

The foundations of the technology for the preparation of porous nanoceramics based on alumomagnesium spinel (MgAl2O4) and zirconium dioxide stabilized in the tetragonal structure (t-ZrO2) with an open porosity of >40% are developed. It is revealed that the cocrystallization of salt solutions with subsequent mechanochemical activation of crystallohydrates can be used for the production of nanosized MgAl2O4 and t-ZrO2 powder precursors (<20 nm). A possible way to control the open porosity and the pore size by choosing the optimal sintering temperature and the kind and the amount of pore-forming additives is shown. The width of the pore size distribution increases with increasing volume fraction of the blowing agent in the initial powder. Nanoporous ceramic materials with pores 25–100 nm in size for MgAl2O4 and 100–300 nm for t-ZrO2 are produced. The technological scheme for applying an α-Al2O3 membrane layer on a t-ZrO2 porous matrix is developed.

Optimization of the properties of cathode materials based on lithium manganese silicate compounds using computer simulation

Using the method of crystallochemical analysis (the TOPOS program package), the 14 most promising and stable structures of lithium manganese (iron) silicate compounds have been selected based on the data on 132 experimentally received and predicted compounds (Materials Project resource).

Synthesis of the study of solid solutions based on the ZrO2–HfO2–Y2O3(CeO2) system

The results of the studies of the conditions of the liquid-phase synthesis of highly dispersed xerogels with a low degree of agglomeration and precursor nanopowders (~10–12 nm) based on zirconium dioxide in the ZrO2–HfO2–Y2O3(CeO2) system are presented. The thermal decomposition of xerogels and formation of crystalline solid solutions with the structure of fluorite are investigated. The optimal conditions for the solidification of nanodispersed powders for fabricating compact ceramics based on solid solutions of ZrO2 and the physical–chemical properties of these ceramics are studied.