V. Ya. Shevchenko

Structure of Nanosized Zirconia Centaur Particles

The crystal structure of structurally inhomogeneous zirconia particles (centaurs) is investigated. It is shown that centaur particles consist of monoclinic and tetragonal fragments which obey rigorous orientational relationships.

Effect of synthesis conditions on the phase composition of ZrO2-CeO2-Al2O3 sol-gel powders

The morphology and phase composition of ultrafine ZrO2–CeO2–Al2O3 powders prepared by heat-treating coprecipitated and successively precipitated hydroxides were shown to depend on the precipitation procedure. The relative amounts of tetragonal and monoclinic zirconia in the sol–gel powders can be controlled by adjusting the precipitation conditions.

Investigation of the Structure of Zirconia Nanoparticles by High-Resolution Transmission Electron Microscopy

The structure of zirconia nanoparticles is investigated by high-resolution transmission electron microscopy (HRTEM). The structurally inhomogeneous nanoparticles with coherent interfaces (centaurs) are observed. The orientation relationships of the conjugated structures are determined.

Wollastonite as a New Kind of Natural Material (A Review)

An analysis of literature and patent data on the problem of producing and using wollastonite and wollastonite-based materials is carried out; the results of studying the properties of heat-insulating articles produced by the vacuum pumping technology are summarized. The theoretical possibility of using natural wollastonite as a material for the production of heat-insulating articles is demonstrated.

New types of two-layer nanoclusters with an icosahedral core

New types of 63-atom two-layer nanoclusters based on the icosahedral core and having the maximum symmetry D3d or Th in crystal have been found using the method of the nanocluster analysis (the TOPOS program package) in the database that was created of crystal structures of intermetallides containing 20319 compounds. It has been shown that these nanoclusters may participate in assembling the crystal and/or be present there as stable fundamental configurations of atoms. The possibilities of the method of the nanocluster analysis have been demonstrated by the example of calculating the chemical composition of the crystal presented as an ensemble of nanoclusters.

Cellular automata and local order in the structural chemistry of the lovozerite group minerals

The structural chemistry of the lovozerite group of minerals is considered using concepts of coordination polyhedra, finite automata and local order. A formal language for these lovozerite-type structures is constructed and the concept of a genetic code for this structure family is suggested. Information and structure are seen to be dialectically interlinked.

Structure of Nanoparticles: I. Generalized Crystallography of Nanoparticles and Magic Numbers

The structure of a nanoparticle of a material is generally determined by the chemical composition of the material, the number of atoms in the particle, and the character of the chemical interaction between atoms. Nanoparticles can have a regular crystalline structure, can be amorphous, or can form a pseudoclose packing undescribable by any of the crystallographic space groups. For each of these structural states of a nanoparticle, there is a certain set of numbers of the atoms involved in the particle that corresponds to optimum stable configurations. These numbers are usually called the magic numbers.

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%.

Effect of Preparation Conditions on the Phase Composition of ZrO2–Al2O3–CeO2 Powders

Data are presented on the phase composition of ZrO2–Al2O3–CeO2 powders containing 10, 30, and 70 mol %, prepared via coprecipitation and successive precipitation. The precipitation procedure is shown to have a strong effect on the phase composition of the heat-treated powders and the state (inter- or intracrystalline) of the T-ZrO2 phase, thereby changing its stability. At an Al2O3 content of 30 mol %, the M-ZrO2 content is independent of the precipitation procedure.

Coexistence of Cubic and Tetragonal Structures in Yttria-Stabilized Zirconia Nanoparticles

Experimental evidence is presented for the coexistence of cubic and tetragonal phases in yttria partially stabilized zirconia nanoparticles (“centaurs”).