Vol 53, No 2 (2017)

We demonstrate that, in the case of InSb〈Mn〉 synthesis through quenching from the liquid state, a second phase in InSb precipitates at higher manganese concentrations than in the case of Czochralski growth. The observed concentration delay of second-phase precipitation can be accounted for in terms of both the complex, multistep formation of Lomer–Cottrell sessile dislocations, accompanying the crystallization of III–V compound semiconductors, and diffusion hindrances to dopant motion to dislocations, associated with the high quenching rate and the presence of other lattice defects.

A novel technique has been demonstrated for direct chemical vapor deposition of carbon nanotubes (CNTs) on aluminum foil. It has been shown that the foil surface acquires catalytic properties after being held in an aqueous nickel nitrate solution for a certain time. CNTs were deposited by the catalytic pyrolysis of ethanol vapor. The hybrid materials thus prepared have the form of aluminum foil coated with “carbon wool” from CNTs on both sides. The layers have good adhesion to the aluminum substrate, which allows it to be deformed without causing the CNT layer to peel off. Such material is potentially attractive, in particular, for the fabrication of supercapacitors.

Cast NiAl–Mo₂C and NiAl–WC alloys have been prepared by self-propagating high-temperature synthesis involving the reduction of starting metal oxides. Synthesis conditions have been found experimentally. The elemental and phase compositions of the alloys have been determined and their microstructure has been studied. The composites have been shown to have higher microhardness than do NiAl intermetallic alloys containing Mo and W inclusions.

We have studied the effect of silver nitrate additions on the anatase–rutile transformation of titanium dioxide in TiO₂/Ag composites at low temperature (500°C). The structure and phase composition of the composites with different Ag(I) concentrations have been determined by X-ray diffraction and transmission electron microscopy. The results demonstrate that the percentage of rutile increases with increasing Ag(I) ion concentration, reaching 60 wt %. A mechanism of the anatase–rutile transformation in the composites has been proposed.

This paper examines the effect of supercritical drying parameters (including the nature of the solvent) on the electrochemical properties of vanadium oxide-based aerogels. It is shown that, among vanadium oxide-based aerogels prepared using different solvents (supercritical CO₂, n-hexane, and n-octane), the material obtained in n-hexane is superior in discharge capacity characteristics: its capacity is 350 to 250 mAh/g in the first seven cycles. The aerogel obtained in supercritical CO₂ has a far lower capacity: 80–105 mAh/g.

Co_xNi_1–xAl₂O₄ (x = 0, 0.25, 0.5, 0.75, 1) aluminate spinels have been prepared by solid-state reactions and their crystal structures have been refined by the Rietveld method. We have analyzed whether the results are consistent with theoretical relationships stemming from the hard sphere model. Using high- and low-temperature X-ray diffraction measurements, we have obtained the temperature dependences of the unit-cell parameters for the synthesized compounds and determined their thermal expansion coefficients. The rate of cation exchange reactions has been shown to be very slow at temperatures below 200°C.

The [B₁₂H₁₂]^2– anion, a three-dimensional aromatic system with a uniform electron density distribution over its boron skeleton, has been shown to react with sodium silicate water glass (WG) to form a supramolecular structure. The WG/[B₁₂H₁₂]^2– system has both short-range and weaker, long-range contacts, which influences the chemistry of the thermolysis process and, as a consequence, the thermal and thermomechanical properties of the composites. At 60% (Et₃NH)₂[B₁₂H₁₂] in the starting mixture, the reaction products contain ~6.6% [B₁₂H₁₁NEt₃]^2–, a substituted derivative that has a plasticizing effect in the case of thermomechanical processing. At an optimal ratio of the starting reagents, the thermo-oxidative stability of the [B₁₂H₁₂]^2– anion and the deformation resistance of the WG/[B₁₂H₁₂]^2– system persist up to 600°C.

Dense SiC-based ceramic materials containing yttrium aluminum garnet (YAG) as an oxide sintering aid have been prepared by hot pressing in the temperature range 1750–1850°C. As a result of melting, the oxides fill spaces between the SiC particles, contributing to the densification of the material and mass transport during the hot pressing process. The present results demonstrate that relatively small amounts of the oxides (≤5 wt %) are needed to ensure a high degree of densification of the SiC–YAG materials. The best physicomechanical properties are offered by the SiC + 3 wt % YAG material sintered at a temperature of 1850°C: ρ = 3.24 ± 0.01 g/cm³, П = 1.1 ± 0.1%, σ_b = 640 ± 10 MPa; K_Ic = 6.4 ± 0.2 MPa m^1/2, Еel = 410 ± 20 GPa, and HV = 26.0 ± 0.2 GPa. This material experiences predominantly intercrystalline fracture.

Data are presented on the purity of the samples of elemental substances, including isotopically enriched samples, received by the Exhibition–Collection of Extrapure Substances in 2007–2015. During this time period, the permanent exhibition received 26 samples of elemental substances from 11 institutes and research and production centers of Russia. The first samples of high-purity isotopically enriched silicon, germanium, sulfur, and selenium were provided. The total impurity concentration in the best samples is 3 × 10^–5 to n × 10^–4 at %. More than half of the new samples compare well to the current world level.