Inorganic Materials最新文献

Regenerative medicine approaches require the creation of new types of resorbable inorganic materials for use in bone tissue engineering. This review considers magnesium-based materials, including magnesium phosphates, which are characterized by a high dissolution degree in the body environment, and their prospects for creating implants for the treatment of bone tissue defects, including cements, ceramics, and composite scaffolds.

The surface of oxygen-free copper has been modified by a focused beam of a nanosecond solid-state laser under a water layer at energy densities W_p in the range 20–32 J/cm², using uncoated copper and samples having absorbing coating. Laser treatment of the uncoated surface to an energy density of 32 J/cm² produced pits about 2.75 μm deep, whereas the pit depth on the coated surface was as large as 5 μm. The pit depth was determined as a function of laser pulse energy density. The effect of impact treatment of oxygen-free copper with a single high-power nanosecond laser pulse has been examined.

The surface of carbon electrodes has been modified by manganese oxide nanoparticles via anodic electrochemical deposition. The structural properties and elemental composition of the resultant MnO₂/C materials have been studied by energy dispersive X-ray microanalysis and transmission electron microscopy. Electrochemical characteristics of the electrodes have been investigated by cyclic voltammetry, galvanostatic charge–discharge measurements, and impedance spectroscopy. We have compared the specific capacitance of the MnO₂/C electrodes in 0.5 M Li₂SO₄, Na₂SO₄, and K₂SO₄ solutions. The materials studied have been shown to have the highest specific capacitance in the sodium sulfate solution.

This paper examines processes underlying the formation of layered materials, analogs of the natural mineral valleriite, CuFeS₂·1.53[(Mg,Al)(OH)₂], made up of alternating two-dimensional sulfide and hydroxide layers, under hydrothermal conditions. The synthesized materials have been characterized by X-ray diffraction, scanning and transmission electron microscopies, X-ray photoelectron spectroscopy, and laser diffraction. The results demonstrate that the formation of valleriite phase at 160°C in an autoclave proceeds through the formation and subsequent consumption of reaction intermediates: erdite (NaFeS₂·2H₂O), haycockite (Cu₄Fe₅S₈), and chalcopyrite (CuFeS₂). The formation of phase-pure valleriite has been shown to occur at a hydrothermal treatment time from 25 to 70 h, whereas shorter or longer treatment times lead to contamination of the reaction product with impurity phases. The nature of the anion in the starting materials (({text{SO}}_{4}^{{2 - }}) or ({text{NO}}_{3}^{ - })) has been shown to have little or no effect on characteristics of the synthesis product. The use of thiourea as a sulfur source instead of sodium sulfide makes it possible to obtain valleriite phase contaminated only slightly with spherical magnesium carbonate particles. Our results demonstrate that, under hydrothermal conditions, equilibrium in the formation of the material can be reached if chalcopyrite phase is used as a precursor of 2D valleriite layers.

A fine-particle Fe–Ni–Co–Cu polymetallic system has been prepared in an aqueous solution of metal chlorides using galvanic replacement by fine-particle aluminum. The elemental and phase compositions of the synthesized powders have been determined by X-ray fluorescence analysis and X-ray diffraction. The content of elemental metals (Fe, Ni, Co, and Cu) in the deposit has been shown to reach 98 wt %. X-ray diffraction data have been used to evaluate the crystallite size (~20 nm) and unit-cell parameters of the phases identified. The powder particles have the form of spherical micron-sized skeletal structures (~75 μm in size), with a large number of nuclei 50–60 nm in size.

Alkali halides have found wide application as thermal energy storage materials, electrolytes for electrochemical cells, and solvents of inorganic substances. Modeling with the use of data for bounding systems is important for constructing phase diagrams of ternary and multicomponent systems. Using three-dimensional vector graphics software, we have constructed a 3D model of equilibrium phase states in the pseudoternary system LiF–NaF–KBr, which is a stable composition triangle in the quaternary reciprocal system Li⁺,Na⁺,K⁺||F^–,Br^–. Based on the 3D model, we have constructed for the first time polythermal and crystallization polytherm. For two polythermal sections, we have demonstrated the presence of regions of limited sodium fluoride-based solid solutions and liquid miscibility gaps and identified the phase crystallization sequence. In the 620°C isothermal section, we have delineated liquid-phase and two- and three-phase fields. The polytherm comprises three crystallization fields: terminal solid solutions based on sodium fluoride, potassium bromide, and lithium fluoride, in which a liquid miscibility gap has been delineated. The stability of the LiF–NaF–KBr composition triangle has been confirmed by thermodynamic calculations for several temperatures of interaction in mixtures of substances in the unstable composition triangle LiBr–NaF–KF. The crystallization polytherm allows one to choose mixtures in the temperature ranges 625–650 and 625–700°C suitable for practical application as melting electrolytes of intermediate-temperature electrochemical cells and molten solvents of inorganic substances.

In this paper, we report a study of the temporal dynamics of photoluminescence intensity in cadmium telluride quantum dots coated with a silicon dioxide shell under continuous optical illumination. Our results demonstrate that at least two mechanisms influence emission from CdTe/SiO₂ quantum dots. In the early stages of our experiments, the luminescence intensity in CdTe/SiO₂ quantum dots is observed to rise, whereas in the final stage luminescence photodegradation begins to prevail. The former mechanism, related to photoenhancement, is due to passivation of surface defects by water molecules and a decrease in the number of nonradiative recombination centers. The latter mechanism, related to photodegradation, can be accounted for by the photooxidation of the CdTe core under the effect of oxygen.

Magnetic hyperfine interactions of ⁵⁷Fe probe Mössbauer nuclei introduced into the ScMnO₃ manganite lattice with a hexagonal crystal lattice have been studied for the first time. Based on the data obtained, the valence state of the probe iron atoms, their local crystal environment, and the orientation of magnetic Fe³⁺ cations in the ({text{ScMn}}_{{{text{0}}{text{.996}}}}^{{{text{57}}}}{text{F}}{{{text{e}}}_{{{text{0}}{text{.004}}}}}{{{text{O}}}_{{text{3}}}}) structure in a magnetically ordered state at T < T_N have been determined. Within the framework of the stochastic relaxation model, the temperature dependence of the Zeeman structure of the ⁵⁷Fe spectra has been analyzed, which has yielded new data on the frustrated Fe−O−Mn exchange interactions. The critical indices of the power-law dependence of the hyperfine magnetic field H_hf(T) on ⁵⁷Fe nuclei have been determined, indicating a reduced dimensionality of the magnetic subsystem of the magnetically ordered manganite ({text{ScMn}}_{{{text{0}}{text{.996}}}}^{{{text{57}}}}{text{F}}{{{text{e}}}_{{{text{0}}{text{.004}}}}}{{{text{O}}}_{{text{3}}}}).

Oxyfluoride glasses in the BaF₂–BaO–SiO₂–B₂O₃–Bi₂O₃–ZnO–Y₂O₃ system were developed and synthesized with various ratios of the initial components. The spectral-luminescent properties of glasses activated with oxides Er₂O₃ and Yb₂O₃ were investigated. According to X-ray powder diffraction, all glass samples are X-ray amorphous, and the glass transition temperature (T_g) was determined. The study of the local structure using IR spectroscopy revealed that the glasses, regardless of composition, contain complex polyborate anions formed by the [BO₃] and [BO₄] groups. It was also shown that bismuth integrates into the glass network, forming Bi–O–Si bonds and network formers in the form of the [BiO₆] groups.

We have studied the dielectric properties of (KNO₃)_1–x/(CeO₂)_x ferroelectric composites with the aim of assessing the effect of cerium oxide on the stability of the polar state of potassium nitrate. The results demonstrate that increasing the fraction of CeO₂ in the (KNO₃)_1–x/(CeO₂)_x composites to 0.25 < x < 0.35 leads to temporary stabilization of their ferroelectric state. The main mechanism of interaction between metal oxides and nitrates is the formation of an electrical double layer on interfaces between particles on account of the difference in adsorption energy between negative and positive ions.