Inorganic Materials (v.49, #4)
Morphology, structure, and composition of polycrystalline CdTe films grown on three-dimensional silicon substrates by G. A. Il’chuk; I. V. Kurilo; R. Yu. Petrus’; V. V. Kus’nezh; T. N. Stan’ko (329-334).
Polycrystalline CdTe films have been produced on various substrates (glass, ITO-coated glass, sapphire, and microtextured silicon) by quasi-closed space growth, and their structural perfection and surface morphology have been studied by optical microscopy and scanning electron microscopy. Using an energy dispersive X-ray spectrometer and the scanning electron microscope, we have obtained the X-ray emission spectra of the CdTe films and determined their elemental composition. The morphological features of the films have been investigated and the cadmium-to-tellurium atomic ratio in the films has been determined experimentally.
CeNi3-based Intermetallic hydrides by S. A. Lushnikov; T. V. Filippova (335-339).
A hydride phase containing 5.0 H atoms per formula unit has been synthesized in the CeNi3-H2 system at a hydrogen pressure of 5 MPa and a temperature of 273 K. The hydride is very stable during storage in air, with no hydrogen release. Its lattice parameters have been determined by X-ray diffraction for different synthesis conditions.
Thermal properties of high-porosity monoliths based on exfoliated graphite by S. V. Filimonov; N. E. Sorokina; N. V. Yashchenko; A. P. Malakho; V. V. Avdeev (340-346).
High-porosity monoliths with densities in the range 50 to 300 kg/m3 have been prepared by uniaxial pressing of exfoliated graphite and their thermophysical properties have been investigated both along and across the pressing direction. We have determined strength characteristics of the monoliths: elastic modulus in compression and bending strength. The procedure used to prepare exfoliated graphite is shown to influence the physicomechanical properties of the monoliths.
Preparation and microstructure of VC0.875 nanopowder by A. S. Kurlov; A. I. Gusev (347-354).
Nanocrystalline VC0.875 nonstoichiometric vanadium carbide powder has been prepared by high-energy milling. The crystal structure, microstructure, morphology, and particle size distribution of the starting and milled powders have been studied by X-ray diffraction, laser diffraction, and scanning electron microscopy. The particle size of the VC0.875 nanopowder has been calculated as a function of milling time in a model of the milling process. Comparison of experimental data and calculation results demonstrates that 10-h milling of vanadium carbide powder with an average particle size 6 μm yields nanopowder 40 to 80 nm in average particle size.
Physicochemical interaction at the MnSi1.71–1.75/Mo interface by L. I. Petrova; M. I. Fedorov; V. K. Zaitsev; A. E. Engalychev (355-358).
Diffusion processes at the interface between higher manganese silicide (HMS) MnSi1.71–1.75 and Mo at elevated temperatures have been studied by microstructural analysis and X-ray microanalysis. The results demonstrate the formation of a reaction diffusion zone at the HMS/metal interface. The compositions of the phases identified in intermediate layers are consistent with phase equilibria in the ternary system Mn-Mo-Si, and their electrical and thermal conductivity is high enough not to create an energy barrier in the contact zone with the semiconductor. The thermal expansion mismatch between the phases in contact may degrade the bonding between the layers.
An X-ray fluorescence method for determining the mass absorption coefficient in thin-film V/Ge and Cr/Ge bilayer systems by N. I. Mashin; E. A. Chernyaeva; A. N. Tumanova; A. A. Ershov (359-362).
A new approach has been proposed for determining the mass absorption coefficient in the X-ray fluorescence characterization of V/Ge and Cr/Ge thin bilayer structures using simple-to-prepare unified layers grown by depositing vanadium or chromium on a polymer film. We have calculated correction coefficients that take into account the absorption of the primary X-ray tube radiation and that of the analytical line of an element from the lower layer in the upper layer.
Et3GeN(SiMe3)2 and Et3SnN(SiMe3)2: New precursors for chemical vapor deposition processes by S. V. Sysoev; L. D. Nikulina; E. N. Ermakova; M. L. Kosinova; V. I. Rakhlin; I. P. Tsyrendorzhieva; A. V. Lis; M. G. Voronkov (363-367).
We have synthesized the germanium- and tin-containing organosilicon compounds Et3GeN(SiMe3)2 and Et3SnN(SiMe3)2 as new precursors for the preparation of materials by chemical vapor deposition. The compounds were characterized by NMR, IR and UV spectroscopies and thermal analysis. Using vapor pressure measurements, we obtained temperature dependences of their saturated vapor pressure. We assessed their thermal stability and calculated the thermodynamic characteristics of vaporization of the organosilicon compounds.
Assessment of interlaboratory and between-method discrepancies in composition certification of high-purity solid elemental substances and nanomaterials by I. D. Kovalev; Yu. A. Karpov; A. M. Potapov; V. G. Pimenov; K. K. Malyshev; O. P. Lazukina; E. N. Volkova; M. F. Churbanov (368-375).
We have assessed interlaboratory and between-method discrepancies in the certification of standards of high-purity nanomaterials and precursors and analyzed the dependence of the discrepancy on the impurity concentration (an important factor, influencing the discrepancy value) and analytical method.
Microstructure and phase composition of ZrO2-CeO2-Al2O3 materials modified with MgO and Y2O3 by L. I. Podzorova; L. I. Shvorneva; A. A. Il’icheva; N. A. Alad’ev; O. I. Pen’kova (376-381).
This paper presents our findings on phase formation processes during heat treatment of sol-gel synthesis products with the composition (mol %) 65(88ZrO2 + 12CeO2) + 35Al2O3 modified with 1 mol % MgO or Y2O3. The composites modified with 1 mol % MgO have been shown to differ significantly in phase composition from the parent nanopowders. Sintering is accompanied by partial decomposition of the tetragonal zirconia (T-ZrO2) based solid solution and the formation of a monoclinic zirconia (M-ZrO2) based solid solution and two aluminum-containing phases: corundum and the mixed oxide MgAl11CeO19. The addition of 1 mol % Y2O3 leads to successive formation of T-ZrO2 and corundum and improvement of their structural perfection. The observed differences in phase formation during heat treatment result in different grain size compositions in the microstructure of the composites.
TiO2- and Nb2O5-based photocatalytic composites by T. A. Sedneva; E. P. Lokshin; M. L. Belikov; A. T. Belyaevskii (382-389).
We have studied the influence of Nb content (0.35–60 wt %) and heat treatment on the phase composition, texture, and photocatalytic activity (PCA) of composites based on titanium(IV) and niobium(V) oxides and obtained materials that possess PCA under illumination at λ ≥ 900 nm.
Thermal transformations in In-MoO3 nanofilms by E. P. Surovoi; G. O. Eremeeva (390-394).
Transformations in In-MoO3 nanosystems have been studied by optical spectroscopy, micros-copy, and gravimetry in relation to the thickness of the In and MoO3 layers and heat-treatment temperature and time. We have measured the contact potential difference across the In and MoO3 films and the photo-voltage in the In-MoO3 system and constructed the energy band diagram of the In-MoO3 system. A model has been proposed for the thermal transformation of the MoO3 films in In-MoO3 bilayers, which involves a redistribution of equilibrium charge carriers at the contact, the formation of a [(V a)++e] center during the preparation of the MoO3 film, transformation of the center into a [e(V a)++e] center during the fabrication of the In-MoO3 bilayer, and thermal ionization of the [e(V a)++e] center.
Synthesis and properties of magnetic sorbents based on transition metal ferrites by L. P. Storozhuk; S. V. Khutornoi; I. M. Mudrak (395-400).
We have developed and optimized a procedure for the synthesis of magnetically controlled nano-composites based on transition metal oxides (MFe2O4, M = Fe2+, Ni2+, and Co2+) with a biocompatible (SiO2) x coating. The relationship between the structure, composition, and magnetic properties of the nanocomposites has been examined. We have studied adsorption interactions of immunoglobulins (Ig) and DNA with the surface layer of the magnetically controlled nanocomposites. The amount of Ig adsorption was determined to be ∼0.5 mg for 100 mg of the adsorbents, and that of DNA adsorption, 0.55–0.6 mg for 100 mg of the adsorbents. Our results demonstrate complete Ig and DNA desorption from the surface of the nanocomposites.
A new layered phase in the alumina-terephthalic acid-water system by D. G. Shabalin; G. P. Panasyuk; L. A. Azarova (401-407).
Reactions between aqueous solutions of aluminum salts and ammonium terephthalate at pH 6–8 lead to the formation of a previously unknown, weakly ordered phase. It has signs of a layered compound with a unit cell parameter of 1.072–1.073 nm. Its empirical composition can be represented by the formula Al2O3 · xC8H6O4 · yH2O · δ(NH3), where x = 0.7–1.2, y = 4.4–6.0, and δ = 0–0.4. It has good structural order across the layers, whereas the order along the layers is weaker and depends on synthesis conditions. Calcination at 120°C leads to partial dehydration and changes the order along the layers, whereas the order across the layers changes little, with a slight increase in lattice strain. Heat treatment at 400°C leads to almost complete dehydration and fully eliminates the order along the layers, whereas the order across the layers is partially retained. Firing at 800°C leads to the formation of γ-Al2O3. A structural model has been proposed for the new phase.
Experimental and calculational approaches to determining the mineralogical composition of rocks in mineral-fiber fabrication and stone casting by V. A. Krenev; I. Z. Babievskaya; N. P. Dergacheva; S. V. Fomichev (408-411).
This paper presents data on the effect of the mineralogical composition of gabbro-basalt rocks on the properties of mineral fibers and stone-cast materials prepared from them. We consider experimental and calculational approaches to determining the mineralogical composition of magmatic rocks, discuss possible origins of discrepancies in results, and demonstrate that the mineralogical compositions determined by physicochemical calculations can be used to roughly estimate the performance of natural raw materials in mineral-fiber production and stone casting.
Synthesis of a bismuth germanium oxide source material for Bi4Ge3O12 crystal growth by I. I. Novoselov; I. V. Makarov; V. A. Fedotov; N. V. Ivannikova; Yu. V. Shubin (412-415).
A technique has been developed for the preparation of a modified source material for the crystal growth of bismuth orthogermanate, Bi4Ge3O12 (BGO). It includes dispersion of molten bismuth through mixing with germanium oxide (GeO2) powder in a rotating reactor, followed by oxidation with oxygen. The source material thus prepared contains, in addition to bismuth and germanium oxides, considerable proportions of germanates (Bi2GeO5, Bi4Ge3O12, and Bi12GeO20), which improve the reactivity of the components of the source material during homogenization before the crystal growth process. After sintering at 880°C, the density of the modified source material (3.9 g/cm3) is a factor of 1.5 higher than that of a source material prepared from Bi2O3 and GeO2 powders. BGO crystals grown using the synthesized source material possess good scintillation characteristics.
Hardness and the nature of microplasticity of hydroxyapatite by V. M. Ievlev; A. V. Kostyuchenko; E. K. Belonogov; S. M. Barinov (416-422).
The hardness of thin (1.0–4.0 μm) hydroxyapatite (HA) coatings with different structures (nanocrystalline, amorphous-crystalline, and amorphous) grown on Ti and Si by rf magnetron sputtering has been studied using nanoindentation. In all of the coatings, deformation was observed to have an elastoplastic nature. The hardness of the nanocrystalline coatings corresponds to medium hardness values of HA microcrystals. The structure of the nanocrystalline coatings has been studied by high-resolution transmission electron microscopy in the indent zone and away from it. Comparison of the hardness values of coatings with different structures and analysis of the intragranular structure leads us to assume a nondislocation mechanism of plastic deformation. Its nature is interpreted in terms of a cluster representation of the structure of HA and amorphous calcium phosphates and cluster-boundary sliding in the course of deformation.
Autosegregation and phase formation on the surface of calcium niobate crystals by Yu. Ya. Tomashpolsky; N. V. Sadovskaya; V. M. Matyuk (423-426).
Nanoscale changes in the surface morphology and elemental composition of calcium niobate, Ca2Nb2O7, crystals in response to thermally stimulated surface autosegregation have been studied for the first time. The results demonstrate that, depending on annealing temperature and duration, the calcium niobate surface becomes niobium-enriched. This is accompanied by the formation of surface phases identical in composition to the host crystal. At 770 K, the surface phase consists of oriented nanocrystallites. With increasing annealing temperature and duration, the nanocrystallites transform into partially oriented microcrystallites identical in composition to the host crystal. Annealing at 1270 K, that is, well below the melting point of Ca2Nb2O7 (1873 K) leads to disproportionation of the surface phase and formation of both niobium-enriched and niobium-deficient phases, including pure CaO. The high-temperature surface phases consist of individual crystallites and intergrowths, which form layers with a rather large surface coverage.
Thermal conductivity of single crystals of M1−x M x ′F2 (M = Ca, Sr; M′ = Mn, Co) isovalent solid solutions by P. A. Popov; A. A. Luginina; P. P. Fedorov; V. V. Osiko (427-429).
The thermal conductivity of single crystals of the Ca0.99Co0.01F2, Ca0.97Co0.03F2, Sr0.99Mn0.01F2, Sr0.989Mn0.01Co0.001F2, and Sr0.995Co0.005F2 solid solutions has been measured in the temperature range 50–300 K. The results demonstrate that doping of CaF2 and SrF2 crystals with small amounts of isovalent transition metal impurities is accompanied by a significant reduction in thermal conductivity.
Calorimetric monitoring of early hardening of cement in the presence of admixtures by A. V. Usherov-Marshak; A. V. Kabus’ (430-433).
This paper considers the key ideas and results of temperature-time monitoring of cement hardening in the presence of admixtures. We demonstrate that the proposed method is highly informative for quantitatively assessing the effectiveness of admixtures in the technologies of cement and concrete.