M. Yu. Arsent’ev

Synthesis and investigation of the structure of ceramic nanopowders in the ZrO2-CeO2-Al2O3 system

A new technological scheme has been developed for synthesizing nanocrystalline powders in the ZrO2-CeO2-Al2O3 system. The powders have been used for preparing nanoceramic materials with an open porosity of ∼1%. The physicochemical properties of these ceramic materials have been investigated.

Preparation and Properties of Ceramic Composites with Oxygen Ionic Conductivity in the ZrO 2 -CeO 2 -Al 2 O 3 and ZrO 2 -Sc 2 O 3 -Al 2 O 3 Systems

Powder precursors in the ZrO2-CeO2-Al2O3 and ZrO2-Sc2O3-Al2O3 systems are prepared by the sol-gel synthesis. It is revealed that the electrical conductivity of the sample doped with scandium oxide is higher than the electrical conductivity of the sample doped with cerium oxide despite the higher content of the nonconducting phase Al2O3 (corundum). The thermal expansion coefficients are determined for all the ceramic samples under investigation. It is established that the Al2O3 dopant affects the thermal expansion coefficient. The ceramic materials studied can be used as solid-electrolyte sensors.

Features of the synthesis and the study of nanocrystalline cobalt-nickel spinel

A nanocrystalline compound nickel cobaltite (NiCo2O4) with the average size of crystals of ∼20 nm at 700°C has been synthesized using the method of combined crystallization of solutions of nitrates with the subsequent thermal and ultrasonic treatment. The optimal sintering mode of the NiCo2O4 powder (1300°C, 2 h, air) has been selected, and ceramics (60–65 nm) with open porosity of 25–30% have been prepared. The temperature and frequency dependences of the electrical conductivity of nickel cobaltite have been studied. It has been assumed that the high values of the electrical conduction and pseudo-capacity of NiCo2O4 are due to the variable valence of Ni and Co in oxides. It is recommended to use cobaltite nickel as an electrode material of a supercapacitor and a catalyst of the oxygen isolation in fuel elements.

Preparation of zirconia-based nanoceramics with a high degree of tetragonality

A synthesis technology for ceramics based on a tetragonal solid solution of zirconia in ZrO2-Y2O3-CeO2 and ZrO2-Y2O3-Al2O3 systems with a high degree of tetragonality (∼1.436) and an average crystal size of 45–70 nm has been developed; it can be recommended for producing bioceramics in restorative dentistry.

Physicochemical properties of nanocrystalline composites based on ZrO2, Al2O3, and rare-earth oxides

Powder precursors have been prepared by means of the sol-gel technique and codeposition, and nanoceramics in the ZrO2-Al2O3-rare-earth (RE) oxide system (RE = Ce, Sc, or Y) based on them have been obtained. Physicochemical properties of the resulting ceramic composites have been investigated. The energy model for oxygen-ionic transport processes in a solid solution based on ZrO2, which relies on computer simulation procedure, has been proposed, and the structural, strength, and electrophysical characteristics of the solid solution have been calculated. The obtained materials are promising as high-melting electrochemical sensors in molten oxides.

Investigation of some physicochemical properties of ceramics, single crystals, and nanofilms based on zirconia, hafnia, and rare-earth oxides

Precursor powders in the ZrO2-CeO2-Sc2O3-Al2O3 system have been prepared using the sol-gel method. A physicochemical analysis of the synthesized ceramics, single crystals, and nanofilms based on ZrO2 and HfO2 oxides has been performed. It has been revealed that the introduction of alumina Al2O3 into the ZrO2-based ceramic samples reduces the thermal expansion coefficient and that these ceramic materials possess a high electrical conductivity as compared to the other materials under investigation.

Ceramic nanocomposites based on oxides of transition metals for ionistors

Low-temperature synthesis methods are used to produce nanoceramic materials for electrodes of the following ionistors: (ZrO2)0.6(In2O3)0.4, praseodymium cobaltite, as well as neodymium, lanthanum, and nickel chromites; they operate in the presence of an ion-conducting phosphorosilicate separator membrane and phosphate impregnation. Film electrodes of ionistors are fabricated that consist of nanocrystalline oxide materials deposited as a thin film on a porous electroconductive metal substrate, i.e., foamed nickel. The MnO2-foamed nickel electrode has a specific capacity of 45.0 F g−1, which is compared with that of industrial supercapacitors.

Synthesis and study of sensor oxide nanofilms in a ZrO2-CeO2 system

Methods of the synthesis of nanostructured oxide films have been suggested for gas sensors based on zirconium and cerium dioxides with a cubic structure and crystallite size of 10–12 nm. The compositions in the CeO2-ZrO2 system having the highest sensitivity have been predicted, based on quantum-chemical calculations via the density functional method (DFT). These calculated data are correlated to the experimental results of the measurement of electroconductivity on air and in a reducing medium (CO2 + CO). The obtained nanosized oxide films have a high response time (5–6 s) and sensitivity; they are promising as resistive sensors for the detection of media with reduced oxygen content. The method of computer simulation allows the reduction of the search period of new materials for gas sensors.

Crystallization and thermochromism of annealed heterostructures containing titanium and tungsten oxide films

Crystalline phases in heterostructures containing titanium and tungsten oxide films are studied after step annealing in vacuum at temperatures between 500 and 750°C. The films are deposited on a silica glass substrate by dc reactive magnetron sputtering. It is found that crystalline phases in single layers and bilayer structures form in a different way. In the latter, crystallization is influenced by the order of layer arrangement on the substrate. Thermochromism in structures annealed in vacuum is due to the oxygen-deficient phase WO3 − x belonging to the hexagonal syngony. This phase intensely grows as the temperature rises from 650 to 750°C.

Synthesis and physicochemical properties of a solid oxide nanocomposite based on a ZrO2–Y2O3–Gd2O3–MgO system

A highly dispersive powder with a (ZrO2)0.92(Y2O3)0.03(Gd2O3)0.03(MgO)0.02 composition and specific surface area of 150 m2/g has been synthesized via a method of coprecipitation of hydroxides with the subsequent cryochemical treatment of the gel. Nanoceramics based on the cubic modification of zirconium dioxide with the grain size of ~40–45 nm have been obtained. The temperature dependence of the specific electrical conductance of the nanoceramics within a temperature range of 350–870°C in air has been studied, and the ratio of the ionic and electronic parts of the conductance has been determined. Recommendations for the use of the obtained oxide nanocomposite as an electrolyte for a high-temperature fuel cell have been given.