T. I. Panova

Synthesis and investigation of properties of nanocrystalline zirconia and hafnia

The effect of the temperature and pH of chemical precipitation on the degree of agglomeration of zirconium and hafnium hydroxides has been investigated. The specific features of crystallization of zirconium and hafnium hydroxides have been revealed. A technological scheme has been proposed for synthesizing ZrO2 and HfO2 nanocrystalline powders.

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.

Effect of the modification of barium titanate on the permittivity of its composites with cyanoethyl ester of polyvinyl alcohol

The effect of chemical modification of submicron barium titanate particles by the deposition of MxOy (x = Ti, Co, Ni) oxide layers from aqueous solutions of the corresponding precursors is studied upon the surface properties of modified BaTiO3 particles and dielectric permittivity of organo-inorganic composites obtained by their dispersion in the matrix of cyanoethyl ester of polyvinyl alcohol and useful in electroluminescent light sources. It is shown that a significant increase (by about 25%) of the dielectric permittivity is observed only when adding Nb2O5, in comparison with a similar composite which contains unmodified BaTiO3. A correlation is found between the dielectric permittivity of the organo-inorganic composites and the presence of Brensted neutral and basic centers with pKa = 6−13, localized on the surface of a filler, being capable of interacting with the polymer matrix. It is shown that an increase of the dielectric permittivity upon deposition of niobium oxide on the surface of BaTiO3 is caused by formation of such centers and modification of the surface layer structure of BaTiO3 particles, with transformation of rutile-like Ti-O bonds to anataselike ones.

Preparation of Ultrafine Tetragonal ZrO2–CeO2Solid Solutions

Nanometer-sized tetragonal Zr1 – xCexO2 – δpowders were prepared by hydroxide precipitation and sol–gel processing. The effects of gel-aging time and solution concentration on the phase composition and particle size of the powders were studied. The ceramics prepared by sintering ultrafine powders at 1500°C had a density of ≃6.0 g/cm3 , open porosity of ≃4%, and closed porosity below 1%.

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.

Preparation of ZrO2-CeO2 and HfO2-CeO2 nanopowders

We prepared weakly agglomerated powders of ZrO2-CeO2 and HfO2-CeO2 solid solutions 5–8 nm in particle size, consisting of monoclinic and tetragonal phases. After heat treatment at 1200°C, the crystallite size was 30 and 14 nm, respectively. We also examined the effect of precipitate freeze drying on the crystallization of hafnia-based solid solutions containing up to 20 mol % CeO2.

Nanocrystalline ceramics based on the ZrO2-HfO2-Y2O3 system

The formation of nanopowders of cubic solid solutions in the ZrO2–HfO2–Y2O3 system is investigated using the coprecipitation method. Conducting ceramic materials are prepared from the powders at 1450°C.

Mechanochemical Synthesis of ZrO2–CeO2 Solid Solutions

ZrO2–CeO2 solid solutions (12 and 13 mol % CeO2) were prepared by mechanochemical synthesis in different media. The mechanical activation medium was shown to have a significant effect on the phase composition and particle size of the resultant powders. The conditions for sintering the powders were optimized.

Mechanochemical synthesis and sintering of (ZrO2)0.97(Y2O3)0.03

The (ZrO2)0.97(Y2O3)0.03 tetragonal solid solution was prepared by solid-state reaction from mechanically activated powder mixtures. The effects of the activation medium and particle size on the sintering behavior of the material was examined.

Synthesis and study of mesoporous xerogels and nanopowders of a metastable solid solution 97ZrO2–3Y2O3 for the fabrication of catalyst substrates

The—technology of the liquid-phase synthesis of metastable phases in the ZrO2–Y2O3 system has been developed. Mesoporous xerogels with the specific surface area of ~350 m2/g and monophase nanopowders (5–10 nm) of the tetragonal solid solution (ZrO2)0.97(Y2O3)0.03 have been obtained and their structural peculiarities have been revealed. The efficiency of the suggested technology and good prospects of the synthesized ZrO2-based precursors in creating catalysts’ substrates have been demonstrated.