G. M. Zeer

Synthesis, microstructure, and the transport and magnetic properties of Bi-containing high-temperature superconductors with a porous structure

Preliminary data on the synthesis and physical properties of polycrystalline Bi1.8Pb0.3 Sr2Ca2Cu3Ox high-temperature superconductors of low density with a foam-like microstructure are reported.

Structural and magnetic resonance investigations of CuCr2S4 nanoclusters and nanocrystals

Nanoclusters and nanocrystals of the room temperature magnetic spinel CuCr2S4 synthesized using a facile solution-based method have been examined by transmission electron microscopy, magnetic measurements, and magnetic resonance over a wide frequency range 9.6–80u2009GHz and at temperatures down to 4.2u2009K. Decreasing of the resonance field and broadening of the resonance lines below 50u2009K for both samples are due to the freezing of magnetic moments of nanocubes and nanocrystalline particles constituting nanoclusters. The effective fields of averaged magnetic anisotropy ⟨HA⟩≅ 2.4 kOe are similar for both nanopowder samples as estimated from resonance measurements at Tu2009=u20094.2u2009K. An additional blocking temperature Tb ≅ 300u2009K appears in nanoclusters due to freezing of the magnetic moment of the entire cluster as a whole. Below this blocking temperature, the magnetic dipolar field acting in boundary areas of interacting constituent nanocrystals is responsible for the additional low-field resonance line observed in th...

Solid-State Reactions in Fe/Si Multilayer Nanofilms

Solid-state reaction processes in Fe/Si multilayer nanofilms have been studied in situ by the methods of transmission electron microscopy and electron diffraction in the process of heating from room temperature up to 900ºС at a heating rate of 8-10ºС/min. The solid-state reaction between the nanolayers of iron and silicon has been established to begin at 350-450ºС increasing with the thickness of the iron layer.

Diffusion bonding through interlayers

Studies of the application of interlayers in diffusion bonding (DB) are reviewed. A method for the classification of these layers for DB of dissimilar materials is proposed. The role of the interlayers and their contribution to the formation of the joint in all stages of bonding are investigated.

Microstructure and properties of a copper electrocontact material with a nanodispersed titanium dioxide additive

The influence of TiO2 nanopowder additive on the microstructure, physicomechanical properties, and performance characteristics of a copper-based composite is studied. The properties of the composites are compared with those of pure copper compacts. The microstructure and state of the composite’s working surface after performance tests are examined. It is shown that, when the amount of TiO2 grows, the hardness of the material rises and the arc quenching effect is enhanced.

Microwave synthesis of hydroxyapatite and physicochemical study of its properties

Method for microwave liquid-phase synthesis of hydroxyapatite samples was developed. The composition of the synthesis products obtained and natural hydroxyapatite was studied by X-ray phase and X-ray fluorescence microanalysis. IR spectra were measured and the dispersity of hydroxyapatite powders obtained, their solubility in water at 20°C, and structural parameters were determined in comparison with natural hydroxyapatite and that produced by the common (“classical”) liquid-phase technique. The microwave-synthesized hydroxyapatite compares well in its properties with the biological and “classical” hydroxyapatites.

Microstructure and properties of an electrocontact Cu–(ZnO/TiO2) material

A copper-based electrical-contact composite material hardened by disperse zinc oxide and zinc titanate is studied by scanning electron microscopy and energy dispersive X-ray microanalysis. The distribution of oxide phases in the samples containing 2.5 wt % oxide nanopowder mixture in an initial charge is found to be uniform. An increase in the amount of oxides leads to an increase in their sized in sintering. A relation between the sample wear and the sample composition is obtained during laboratory tests. It is shown that the introduction of more than 2.5 wt % oxide mixture results in intense wear of the working surface of the sample and an increase in the running-in period of contacts.

Formation of Phases and Microstructure of ZnO and TiO2 Based Ceramic

Nanopowders of zinc and titanium oxides were used to obtain samples of Zn2TiO4–ZnO ceramic. Phase formation as well as the microstructure and elemental composition of the phases formed were studied by means of electron microscopy. The density and porosity were calculated, and the sizes of grains and pores in the ceramic were determined. The temperature at the zinc titanate forms was determined. It was shown that it corresponds to the sintering temperature of electrocontact materials with this composition. It is proposed that zinc titanate and oxide be used as arc-suppressing and dispersion-hardening additional additives in copper-based electrocontact materials.

Physicochemical properties of spent Achinsk refinery reforming platinum-rhenium catalyst

The physicochemical and technical properties of the R-98 reforming catalyst partially spent on a LK-6Us unit in the Achinsk refinery and changes in these characteristics during operation after four regeneration cycles have been studied. It has been found that during the time on stream of the catalyst, a reduction in the specific surface area, partial phase transformation of the oxide support, and buildup of carbon deposits and metal impurities serving as catalyst poisons take place. The regeneration did not afford complete recovery of the properties. In total, the above irreversible changes in the catalyst characteristics led to gradual degradation of the efficiency upon reforming.

Magnetic Resonance in a Cu-Cr-S Structure

A layered Cu-Cr-S structure composed of single-crystal CuCrS2 layers and thin CuCr2S4 plates embedded in them has been investigated by the magnetic resonance and scanning electron microscopy methods. The Curie temperature and saturation magnetization of the spinel phase of the investigated samples have been determined. The thickness of the CuCr2S4 layers has been estimated. The dependence of the growncrystal topology on synthesis conditions has been established. An interpretation of the anomalous behavior of the magnetostatic oscillation intensity is offered.