O.L. Khasanov

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.

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”).

Effect of Ultrasonic Compaction of Nanopowder on Structure and Fracture Character of Zirconia Nanoceramics

The structural-scale hierarchy and phase composition of zirconia nanoceramics (ZrO2 — 5.4wt%Y2O3) fabricated from plasma chemical zirconia nanopowder compacted by ultrasonic (US) action and without it are studied and compared. It has been shown, that US-action is rather effective method in technological process of nanoceramics production. It involves a reduction of grain sizes and grain aggregate sizes of sintered ceramics; the grain in such ceramics is a layered pack of subgrains, nuclei of which are the scaly particles of initial nanostructured powder (NP). The ceramics consists of cubic and tetragonal phases of zirconia

The use of the ultrasonic compaction method for the PZT piezoelectric ceramics fabrication

The method of ultrasonic (US) compaction for the fabrication of Pb(ZrTi)O/sub 3/ PZT piezoceramics was approved. The values of density, granularity, shrinkage of ceramic samples, sintered from the compacts compacted by traditional uniaxial pressing and by ultrasound action are compared. It is shown that US compaction contributes to sintering temperature lowering and to PZT piezoceramics granularity reduction.

Influence of the shape factor on efficiency of the green compact ultrasonic compacting and properties of sintered zirconia ceramics

The properties of green compacts and ceramics from ZrO/sub 2/-Y/sub 2/O/sub 3/ nanopowder compacted under ultrasonic action (power of 0.5; 1; 2; 3 kW) were studied. The shape factor of the green compacts (the ratio of height to diameter) was h/D=0.05 and 0.37. Phase constitution, grain structure, density and shrinkage, of ceramics sintered at 1650/spl deg/C from the green compacts with different h/D, were investigated. The possibility for improvement of mechanical properties of advanced ceramics by using optimum regimes of ultrasonic compaction was shown.

Dry ultrasonic compaction of (Ba,Sr)TiO/sub 3/ nanopowder for ceramics production

The method of dry ultrasonic compaction was applied to press sol-gel ultrafine powder of (Ba,Sr)TiO/sub 3/. Green compacts and sintered ceramics densities were compared depending on the powder compaction conditions (compaction pressure P, ultrasound power W). The grain size of sintered ceramics was analysed in dependence on the compaction conditions and sintering regimes (sintering temperature, holding time, heating rate). It was shown that dry ultrasonic compacting is possible for thin as well as thick green compacts with diameter of 50 mm. To make the most dense ceramics, the existence of optimum BST nanopowder compaction regimes was shown.

Influence of applied oscillation mode at nanopowder ultrasonic compaction on Y-TZP nanoceramics properties

The properties of the green compacts from (ZrO/sub 2/-5% Y/sub 2/O/sub 3/) ultrafine powders (UFP) compacted under action of ultrasonic oscillations (USO), which were supplied perpendicularly and parallel to pressing axis have been studied. The distinctions of such properties as density, granularity, hardness and fracture toughness of ceramics sintered from the compacts of both types are shown.

Ultrasonic compacting of zirconium ceramics from ultradispersed powders

A method for compacting ultradisperse powders (UDP) of ZrO2-3% Y2O3 by radially transmitted ultrasonic vibrations (USV) by imposing static pressing pressure is developed. The optimized USV regimes provide compacts from UDP with optimum properties.

The structure and phase condition's evolution in the silicon carbide ceramics surface layer under the electron-beam treatment

The elemental constituents, phase composition and substructural evolution were investigated in the article in the silicon carbide ceramics surface layer which was subjected to the intense pulsed electron beam the density of the electron beam being varied. It was shown that the ceramic layer surfaces structure and phase conditions were controlled by the electron beam characteristics. The SiC-ceramics surface layer nanostructuring was detected and the electron beam treatment conditions which lead to this effect were defined.

The Precipitation of the Nanoparticles by the Thermophoresis at the Cryogenic Temperatures

The conditions of nanodispersed particles precipitation from a gas flow on the surface cooled to cryogenic temperatures are analyzed. The range of allowable values of precipitation surface temperature has been defined in dependence of dispersed flow characteristics. The method can be used both for catching of nanopowders, and for gas cleaning from aerosol and dust particles for ecological purposes.