Inorganic Materials (v.52, #4)
Approaches to the fabrication of calcium phosphate-based porous materials for bone tissue regeneration by S. M. Barinov; V. S. Komlev (339-346).
This paper reviews advances in the fabrication of calcium phosphate materials for injured bone tissue regeneration. We examine the key features of rapid prototyping for the fabrication of porous ceramic scaffolds with tailored architectures, the technology of biopolymer-based composite materials reinforced with calcium phosphate particles, and the fabrication of porous scaffolds via cement route.
Keywords: calcium phosphates; scaffolds; ceramics; additive technologies; three-dimensional (3D) printing; bone tissue regeneration
CaGa2Se4–GaSe system by N. I. Yagubov; I. I. Aliev; S. I. Tagiev; F. A. Novruzova (347-350).
The phase relations in the CaGa2S4–GaSe system have been studied using differential thermal analysis, X-ray diffraction, microstructural analysis, microhardness tests, and density measurements, and its T–x phase diagram has been mapped out. The CaGa2S4–GaSe system has been shown to be a pseudobinary join of the ternary system Ca–Ga–Se. The CaGa2S4–GaSe system has been found to contain limited solid solutions based on the constituent selenides. The electrical conductivity of CaGa2S4 has been measured and its current–light behavior and photoelectric properties have been studied.
Keywords: pseudobinary; eutectic; solid solution; microhardness; photoconductivity
Behavior of detonation nanodiamond at high pressures and temperatures in the presence of a hydrogen-containing fluid by T. D. Varfolomeeva; A. G. Lyapin; S. V. Popova; N. F. Borovikov; I. P. Zibrov; V. V. Brazhkin (351-356).
The recrystallization of detonation nanodiamond in the presence of hydrogen-containing fluids has been studied at pressures from 6 to 8 GPa and temperatures above 1000°C. Electron microscopy and Xray diffraction data demonstrate that, in the presence of a hydrogen-containing fluid, nanocrystalline diamond recrystallizes to micron dimensions. We discuss the mechanism underlying the influence of hydrogencontaining media on the growth of diamond nanocrystals.
Keywords: nanodiamond; high pressure; hydrocarbons
Magnetotransport effects in granular Cd3As2 + MnAs structures at high pressures by A. G. Alibekov; A. Yu. Mollaev; L. A. Saipullaeva; S. F. Marenkin; I. V. Fedorchenko (357-360).
The transport properties of granular Cd3As2 + MnAs (44.7% MnAs) composite structures have been studied near room temperature at high hydrostatic pressures of up to 9 GPa. The results demonstrate that the composite undergoes a structural phase transition and has a pressure-induced negative magnetoresistance.
Keywords: high pressure; Hall effect; resistivity; magnetic granular structures; negative magnetoresistance; electrical transport; structural phase transition; nanocluster
Influence of isovalent and heterovalent substitution for Bi3+ and Fe3+ on the properties of Bi2Fe4O9-based solid solutions by A. A. Zatsiupa; L. A. Bashkirov; I. A. Vialikanava; G. S. Petrov; S. V. Shevchenko (361-366).
Bi2–х La х Fe4O9 and Bi2Fe4–2x Ti x Co x O9 ferrites have been prepared by solid-state reactions at a temperature of 1073 K. X-ray diffraction data indicate that, in the Bi2–х La х Fe4O9 system, the limiting degree of La3+ substitution for Bi3+ ions in Bi2Fe4O9 does not exceed 0.05 and that the limiting degree of substitution in the Bi2Fe4–2x Ti x Co x O9 system lies in the range 0.05 < x < 0.1. The specific magnetization and specific magnetic susceptibility of the samples have been measured at temperatures from 5 to 300 K in a magnetic field of 0.86 T. The field dependences of magnetization obtained for the Bi2–х La х Fe4O9 and Bi2Fe4–2x Ti x Co x O9 ferrites at temperatures of 300 and 5 K demonstrate that partial isovalent substitution of La3+ for Bi3+ ions in Bi2Fe4O9 and heterovalent substitution of Ti4+ and Co2+ ions for two Fe3+ ions leads to partial breakdown of the antiferromagnetic state and nucleation of a ferromagnetic state.
Keywords: bismuth ferrite; magnetization; magnetic susceptibility; effective magnetic moment
Behavior of the Mo–Al2O3 system in a controlled reducing atmosphere by D. V. Kostomarov (367-371).
Stochastic simulation (Monte Carlo method) has been used to evaluate the Mo–Al2O3 system at T = 2400 K and p = 1 × 105 Pa in a controlled Ar + H2 atmosphere. The results demonstrate that the qualitative and quantitative compositions of the system differ markedly from those in an inert (Ar) atmosphere: the presence of hydrogen in the system leads to the formation of hydrogen-containing vapor species (OH, H2O, AlOH, AlOOH, AlH, AlH2, and smaller amounts of H2O2, HO2, and AlH3). Increasing the hydrogen concentration in a controlled atmosphere leads to a reduction in the total concentration of oxygen and molybdenum oxides, accompanied by an increase in the concentration of elemental Al in the vapor phase. We have identified the main chemical processes that take place in the system and have shown that such processes have a cyclic nature and involve repeated interactions with the participation of the basic components of the system.
Keywords: molybdenum; aluminum oxide; stochastic simulation; Gibbs free energy
Synthesis of supported SnO2–CeO2 catalysts for the deep oxidation of methane by O. S. Khalipova; S. A. Kuznetsova; S. I. Galanov (372-377).
A new method has been proposed for the synthesis of catalytically active 80 wt % SnO2 + 20 wt % CeO2 materials supported on glass fiber, which involves the use of an ethanolic film-forming solution based on cerium(III) nitrate and salicylic acid, with the addition of tin(IV) chloride. We have studied the morphology of the materials thus prepared and assessed their catalytic activity for the deep oxidation of methane. The results indicate that the appreciable catalytic activity of the materials is ensured by their uniform distribution over the support surface and the small oxide aggregate size ( 10 μm), which is due to the use of the filmforming solution of the proposed composition.
Keywords: Synthesis of oxide catalysts; film-forming solution; cerium(IV) oxide; tin(IV) oxide; properties of oxide catalysts
Relationship between effective and ideal separation factors for distillation and sublimation by A. I. Kravchenko (378-385).
General aspects of the relationship between the effective (β) and ideal (βi) separation factors for the distillation and sublimation of elemental substances containing low-volatile impurities have been established. It has been shown that the difference between β and βi may be both insignificant and extremely large: 4 to 16 orders of magnitude or even more. In host–impurity systems having the same host, the difference between β and βi decreases as βi approaches unity, all other factors being the same. The difference between β and βi is moderate, within one order of magnitude, when βi differs from unity by no more than three orders of magnitude. In a given host–impurity system, the difference between β and βi increases with decreasing impurity concentration. In individual systems, the difference between β and βi increases with increasing yield at a given initial impurity concentration.
Keywords: refining; distillation; sublimation; efficiency
Hydrophobization of porous ceramic materials using supercritical carbon dioxide by A. S. Bespalov; V. M. Buznik; D. V. Grashchenkov; L. N. Nikitin; V. K. Ivanov; V. O. Lebed’; I. S. Chashchin (386-392).
A process has been proposed for hydrophobizing an inorganic porous material consisting of silica fibers using fluoroalkane dissolution in supercritical carbon dioxide. The process allows one to produce thin, homogeneous polymer coatings both on the surface and in the bulk of the material, ensuring that the material has excellent hydrophobic properties, which significantly improves its performance parameters and extends its potential application field.
Keywords: superhydrophobicity; supercritical carbon dioxide; fluoroalkane; ceramic material
Synthesis and properties of Na x CoO2 (x = 0.55, 0.89) oxide thermoelectrics by N. S. Krasutskaya; A. I. Klyndyuk; L. E. Evseeva; S. A. Tanaeva (393-399).
Na x CoO2 (x = 0.55, 0.89) sodium cobaltites have been prepared by solid-state reactions; their structural parameters have been determined; their microstructure has been studied; and their thermal (thermal expansion, thermal diffusivity, and thermal conductivity), electrical (electrical conductivity and thermoelectric power), and functional (power factor, thermoelectric figure of merit, and self-compatibility factor) properties have been investigated in air at temperatures from 300 to 1100 K. The results demonstrate that, with increasing sodium content, the electrical conductivity and thermoelectric power of the materials increase and their thermal conductivity decreases. As a result, the power factor and thermoelectric figure of merit of the Na0.89CoO2 ceramic at a temperature of 1100 K reach 0.829 mW/(m K2) and 1.57, respectively. The electron and phonon (lattice) contributions to the thermal conductivity of the ceramics have been separately assessed, and their linear thermal expansion coefficients have been evaluated.
Keywords: oxide thermoelectrics; sodium cobaltite; power factor; thermoelectric figure of merit
Preparation of fine-grained ceramics by hot-pressing of Ce0.09Zr0.91O2/MgO/Al2O3 nanopowder by E. A. Trusova; A. A. Khrushcheva; A. S. Lysenkov; N. A. Alad’ev (400-404).
We have studied the effect of hot-pressing conditions (different pressure rise rates and isothermal holding temperatures in the range 1450–1550°C) on the microstructure of ceramics produced from nanopowder with the composition Ce0.09Zr0.91O2/MgAl6O10/γ-Al2O3 (20.6, 37.4, and 42.0 wt %, respectively). Firing at 1450°C for 1 h made it possible to obtain fine-grained ceramics with less than 3 μm in grain size. The compaction pressure rise rate was shown to be a key parameter under such thermal conditions (20 + 10°C/min → 1450°C). Grain growth was prevented most effectively when the maximum load, 30 MPa, was reached at a temperature of 1000°C. Under such conditions, the grain size was 0.4–0.8 μm and the relative density reached 98.8%.
Keywords: composite nanoparticles; hot pressing of ultrafine powders; high-density fine-grained ceramics
Effect of polarizing signal duty cycle on the composition, morphology, and protective properties of PEO coatings on AMg3 aluminum alloy by V. S. Egorkin; I. E. Vyaliy; S. L. Sinebryukhov; S. V. Gnedenkov; V. M. Bouznik (405-411).
This paper presents a study aimed at assessing the effect of polarizing signal duty cycle D in the plasma electrolytic oxidation (PEO) process on the composition, morphology, and protective properties of coatings produced on AMg3 aluminum alloy in a tartrate-containing electrolyte. It is shown that increasing the duty cycle of a short-pulse (τ = 5 μs) polarizing signal leads to a decrease in the porosity of the growing PEO layers. This, in turn, improves the protective properties and surface strength of the alloy. The pulse duty cycle influences the chemical composition and thickness of the growing oxide coatings.
Keywords: plasma electrolytic oxidation; protective coatings; chemical composition; aluminum; duty cycle; microhardness
Structure, thermal stability, and microhardness of ZrO2 coatings produced by different techniques by S. G. Valyukhov; O. V. Stognei; M. S. Filatov; M. A. Kashirin (412-418).
Using ion-beam and rf magnetron sputtering of oxide targets, we have grown thin ZrO2 coatings on 12Kh18N10T high-temperature steel substrates. Depending on the deposition technique, amorphous or crystalline (t + c) coatings have been obtained. The amorphous zirconia retains a disordered structure and high microhardness values up to 600°C. Its crystallization leads to a sharp drop in its microhardness and peeling from the substrate. The initially crystalline coating retains continuity and high microhardness values despite the t → с phase transition at 600 and 700°C. Only annealing at 800°C or higher temperatures reduces its microhardness. This is tentatively attributed to the influence of the substrate.
Keywords: thin coating; microhardness; annealing; thermal stability; structural changes
High-temperature synthesis of composites based on nickel aluminides by V. V. Gostishchev; I. A. Astapov; A. V. Seredyuk; S. N. Khimukhin; Ri Hosen (419-422).
We have examined conditions for the preparation of a NiAl + MoB + Mo composite material through thermally conjugate self-propagating high-temperature synthesis reactions with an aluminothermic reduction step. The reduction reactions involved have been thermodynamically assessed, and the elemental and phase compositions of the obtained materials have been determined. The composite has been shown to consist of the intermetallic phase NiAl with β-MoB inclusions, which have high microhardness values (26.32 GPa).
Keywords: nickel aluminides; self-propagating high-temperature synthesis metallurgy; molybdenum boride; microhardness
Anisotropic electrical properties of a eutectic InSb + MnSb composite by I. Kh. Mamedov; D. H. Arasly; A. A. Khalilova; R. N. Rahimov (423-428).
The temperature dependences of the Hall coefficient, electrical conductivity, and thermoelectric power for a eutectic InSb + MnSb composite have been studied in the temperature range from 80 to 700 K. Electron-microscopic results confirm that the system is in a two-phase state and consists of an InSb matrix and needle-like MnSb metallic inclusions. The inclusions are surrounded by interfacial zones ~0.3 μm in width. The observed anisotropy in the transport properties of the material is attributed to a short-circuiting effect of the metallic inclusions. Interpretation in terms of effective medium theory with allowance for the interfacial zones suggests that they make a significant contribution to the electrical conductivity anisotropy.
Keywords: eutectic composite; metallic inclusions; interfacial zone; microstructure; differential thermal analysis
Local elastic moduli of particle-filled B83 babbitt-based composite materials prepared by powder metallurgy techniques by I. E. Kalashnikov; N. B. Podymova; A. A. Karabutov; L. K. Bolotova; L. I. Kobeleva; A. G. Kolmakov (429-434).
We have measured local elastic moduli of particle-filled B83 babbitt-matrix composite materials produced by powder metallurgy techniques and containing silicon carbide (SiC) ceramic and modified shungite rock particles as fillers. The measurements were made by an optoacoustic laser method, whose basic principle is to determine the phase velocities of thermo-optically excited longitudinal and shear ultrasonic waves. The addition of 3 wt % of high-modulus SiC particles tends to increase the Young’s and shear moduli (by 10–12%) and decrease Poisson’s ratio (by 5%) relative to a hot-pressed B83 babbitt sample without fillers.
Keywords: composite material; babbitt metal; micron- and nanometer-sized fillers; optoacoustic laser method; longitudinal and shear acoustic waves; elastic moduli
Functional kinetic analysis of the effect of admixtures on cement hardening by A. V. Usherov-Marshak; A. V. Kabus’ (435-439).
This paper discusses the problems of ensuring compatibility and functionality of admixtures with cements. We analyze the methodology—developed on the principles of continuity and superpositions—of functional kinetic analysis of the effect of admixtures on the hardening of cement systems using calorimetric monitoring of early hardening stages and illustrate the possibility of using this methodology by the examples of the technologies of summer ready mix and mass concretes, assessing the levels of the effect of admixtures on the hardening kinetics of cements.
Keywords: admixtures; functionality; compatibility; continuity principle; calorimetry