The work focuses on developing eco-friendly "soft" chemistry techniques. Thus, perforated nanosheets can be prepared at room temperature by interfacial interactions. A reaction between ethylenediamine (EDA) vapor and zinc cations in zinc salt aqueous solution produced a thin solid film of zinc-layered hydroxide salts (ZnLHS) on the solution surface. The composition, crystalline structure and morphology of the film were controlled by hydrochemical equilibrium in aqueous solution and depended on the precursor salt. The conditions were identified under which ZnLHS hierarchical porous films were formed at the solution-gas interface. Pores of about 50 nm in size occurred due to dissolution of an intermediate compound. Decomposition caused by heat treatment resulted in the formation of voids up to 10 mu m in size. The layered structure of the synthesized film had an interlayer spacing of 2 nm allowing intercalation of silver ions. ZnAg0LHS composite film was obtained which contained Ag nanoparticles of 2-3 nm in size and demonstrated high photocatalytic activity in the decomposition reaction of the methylene blue aqueous solution. This facile synthesis method of hierarchical-porous films is promising for the design of new materials for sensors, biomedicine, and environmental applications.

Heat-resistant fibers made of semi-crystalline R-ODA thermoplastic polyimide synthesized in our laboratory were produced by melt extrusion. Aiming a modification of mechanical properties, these fibers underwent high-temperature orientation drawing to various draw ratios. Morphological structures of both the nascent R-ODA powder and the fibers were examined using scanning electron microscopy. Wide-angle X-ray scattering showed that the polymer crystallized, and the crystallites' orientation depended on the filament orientation degree. Differential scanning calorimetry was employed to analyze thermal characteristics of R-ODA-based fibers. In addition, the mechanical properties of the polyimide fibers with different draw ratios were investigated.

The corrosion behavior of the diffusion zinc coatings based on the 8-phase FeZn7-10 in a solution of 3 wt.% NaCl in water was studied using electrochemical and physicochemical methods. Initial corrosion of the coatings involves selective dissolution of zinc from the 8-phase. As exposure duration increases, both components of the coating alloy dissolve. The physicochemical nature and electrochemical properties of the corrosion product layer were studied under conditions of simultaneous dissolution of the coating components. Iron can accumulate in the layer of corrosion products during prolonged corrosion of the coatings. In this case, the chemical composition of the electrolyte near the electrode and the structural and phase state of the corrosion products change. After long-term corrosion, the layer of products consisted of zinc oxide and amorphous hydroxide compounds of zinc and iron.

Anomalous changes were found in the properties of thin films of zinc and cadmium oxides on fused quartz substrates during oxidation. Depending on the oxidation temperature, absorption shifted towards shorter wavelengths in a narrow temperature range, and the band gap increased. The effect was not reversible. On other substrates (sapphire, MgO) the same films demonstrated no sharp changes in the absorption spectra during oxidation at up to 800 °C. XPS (X-ray Photoelectron Spectroscopy) and XRD (X-ray Diffraction) measurements revealed the changes in the film composition—the appearance of silicon atoms and a relative decrease in the number of metal atoms which could be responsible for the effects observed. Phase transitions in quartz and the effect of lattice vibrations on its surface structure (soft mode) could result in the compositional change. Additionally, EM (Electron Microscopy) and XRD data showed an increase in the crystallinity of the samples in the same narrow temperature range.

Silicon carbide (SiC) is a wide-band gap semiconductor that exceeds other semiconducting materials (except diamond) in electrical, mechanical, chemical, and radiation stability. In this paper, we report a novel approach to fabrication of SiC nano films on a Si substrate, which is based on the endotaxial growth of a SiC crystalline phase in a graphite-like carbon (GLC) matrix. GLC films were formed by carbonization of rigid rod polyimide (PI) Langmuir-Blodgett (LB) films on a Si substrate at 1000 degrees C in vacuum. After rapid thermal annealing of GLC films at 1100 degrees C and 1200 degrees C, new types of heterostructures SiC(10 nm)/GLC(20 nm)/Si(111) and SiC(20 nm)/GLC(15 nm)/SiC(10 nm)/Si(111) were obtained. The SiC top layer was formed due to the Si-containing gas phase present above the surface of GLC film. An advantage of the proposed method of endotaxy is that the SiC crystalline phase is formed within the volume of the GLC film of a thickness predetermined by using PI LB films with different numbers of monolayers for carbonization. This approach allows growing SiC layers close to the 2D state, which is promising for optoelectronics, photovoltaics, spintronics.

Abstract The composite material for the study was obtained by wire-arc additive manufacturing on the basis of AA1050 (commercially pure aluminum) and AA5056 (commercial alloy of the Al-Mg system) aluminum alloys. The influence of the degree of deformation by high-pressure torsion technique on the mechanical properties and microstructure of the composite material was investigated. The dependences of the static strength and plasticity of the material on the degree of deformation were obtained. The microstructure of the material was investigated by scanning electron microscopy and X-ray diffraction analysis. The optimal deformation route providing the best combination of mechanical properties is revealed, the key microstructure parameters providing optimal properties are determined.

Composite threads based on polylactide (PLA) containing up to 20 wt% carbon nanofibers (CNF) were produced using melt technology. The formation of a percolation cluster was studied in composite filaments with various morphologies (non-oriented, subjected to isothermal crystallization, and oriented by six times). By adding 20 wt% CNF, a specific resistance of 10(0) Ohm m was achieved in the PLA filament. With orientation stretching, the specific resistance was 10(7) Ohm m, regardless of the CNF concentration. The scanning electron microscopy study showed poor adhesion between PLA and CNF. Threads containing 1 wt% CNF demonstrated stable conductive characteristics under dynamic loading for 24 h (50% of their breaking load). Studies of the creep of composite fibers have shown that small amounts of CNFs promote the sliding of polymer fibrils. In vivo tests showed that the addition of 5 wt% CNF led to an increase in the rate of bioresorption of PLA filaments. Additionally, the conductive properties were maintained for 12 months after implantation. The prepared filaments can be used in flexible electronics for biomedical applications.

Atomic layer deposition (ALD) is a useful tool for producing ultrathin films and coatings of complex composition with high thickness control for a wide range of applications. In this study, the growth of zinc–titanium oxide nanofilms was investigated. Diethyl zinc, titanium tetrachloride, and water were used as precursors. The supercycle approach was used, and wide ZnO/TiO2 (ZTO) ALD cycles were prepared: 5/1, 3/1, 2/1, 1/1, 1/2, 1/3, 1/5, 1/10, 1/20. Spectral ellipsometry, X-ray reflectometry, X-ray diffraction, scanning electron microscopy, SEM-EDX, and contact angle measurements were used to characterize the thickness, morphology, and composition of the films. The results show that the thicknesses of the coatings differ considerably from those calculated using the rule of mixtures. At high ZnO/TiO2 ratios, the thickness is much lower than expected and with increasing titanium oxide content the thickness increases significantly. The surface of the ZTO samples contains a significant amount of chlorine in the form of zinc chloride and an excessive amount of titanium. The evaluation of the antibacterial properties showed significant activity of the ZTO–1/1 sample against antibiotic-resistant strains and no negative effect on the morphology and adhesion of human mesenchymal stem cells. These results suggest that by tuning the surface composition of ALD-derived ZTO samples, it may be possible to obtain a multi-functional material for use in medical applications.

Phase-homogeneous LiFePO4 powders have been synthesized. The content of impurity crystalline phases was less than 0.1%, according to synchrotron diffractometry (SXRD) data. Anisotropic crystallite sizes L¯Vhkl were determined by XRD. A low resistance covering layer of mechanically strong ferric-graphite-graphene composite with impregnated ferric (Fe3+) particles < 10 nm in size increases the cycleability compared to industrial cathodes. In accordance with the corrosion model, the destruction of the Fe3+-containing protective layer of crystallites predominates at the first stage, and at the second stage Fe escapes into the electrolyte and to the anode. The crystallite size decreases due to amorphization that starts from the surface. The rate capability, Q(t), has been studied as a function of L¯Vhkl, of the correlation coefficients rik between crystallite sizes, of the Li diffusion coefficient, D, and of the electrical relaxation time, τel. For the test cathode with a thickness of 8 μm, the values of D = 0.12 nm2/s, τel = 8 s were obtained. To predict the dependence Q(t), it is theoretically studied in ranges closest to experimental values: D = 0.5 ÷ 0.03 nm2/s, τel = 8/1 s, average sizes along [010] L¯1 = 90/30 nm, averaged r¯ = 0/1.

Epitaxial layers of Al x Ga 1-x As 1-y Sb y with an aluminum content x~60% and antimony content y~3% were successfully grown by molecular-beam epitaxy at low temperature. A developed system of AsSb nanoinclusions was formed in the semiconductor matrix by subsequent annealing. The extended transparency window of the obtained metamaterial allows us to document the absorption of light near the interband absorption edge of the Al x Ga 1-x As 1-y Sb y semiconductor matrix. Parameters of the observed extinction band allow us to attribute the optical absorption to the plasmon resonance in the system of AsSb nanoinclusions. Keywords: molecular beam epitaxy, x-ray diffraction analysis, transmission electron microscopy, optical properties, plasmon resonance.

Interaction at the interface between aqueous solution and gaseous reagent opens up the possibility of engineering hollow crystals of metal fluorides.

Методом молекулярно-лучевой эпитаксии при низкой температуре с использованием прерываний роста успешно выращены эпитаксиальные слои Al x Ga 1-x As 1-y Sb y с содержанием алюминия x~60% и содержанием сурьмы y~3%. Путем последующего отжига в полупроводниковой матрице сформирована развитая система нановключений AsSb. Увеличенное окно прозрачности полученного метаматериала позволило надежно документировать широкую полосу поглощения света вблизи края межзонного поглощения полупроводниковой матрицы Al x Ga 1-x As 1-y Sb y . Параметры наблюдаемой полосы экстинкции позволяют связать такое поглощение света с плазмонным резонансом в системе нановключений AsSb. Ключевые слова: молекулярно-лучевая эпитаксия, рентгенодифракционный анализ, просвечивающая электронная микроскопия, оптические свойства, плазмонный резонанс.

The average sizes L¯i, and their dispersion Wi along the i-th axis, of crystallites in powders are used to determine X-ray diffraction sizes, Di XRD, averaged over crystallite columns within the BWA method. Numerical calculations have been carried out for an orthorhombic lattice of crystallites, such as LiFePO4, NMC, having a Lamé’s g-type superellipsoid shape. For lognormal distributions, the analytical expression for the normalized coefficient Kn has been found: Kn=Di XRD/L¯i=Kg,0+KgW2, where Kg,0 is a constant at W→0, Kg is a constant depending on the g -type shape. The dependences of Di XRD are also calculated for normal distribution. A fairly simple equation can be obtained as a result of analytical transformations in the framework of experimentally validated approximations. However, a simpler way is to carry out numerical computer calculations with subsequent approximation of the calculated curves. Using the obtained analytical expressions to control technologies from nuclear fuel to cathode materials will improve the efficiency of flexible energy network, especially storage in autonomous and standby power plants.

Reactor particles of nascent polyetherimid (PI) R-BAPB powder consist of numerous morphological units of the lamellar type, which have semicrystalline structure. Two endo-peaks at 318 °C and 340 °C were observed in the DSC thermogram of the PI powder. A unique in-situ thermo-WAXS experiment showed no significant difference in X-ray peak profiles when the sample was heated from room temperature up to 330 °C, (the valley between the low- and high-temperature endo-peaks). At that point the WAXS reflections became sharper and much better resolved without a visible crystal cell transformation. It was revealed that the degree of crystallinity dropped near 330 °C and continued decreasing until the complete melting of the sample. The low-temperature endo-peak is associated with melting of numerous small crystallites leading to the sharp amorphization of the sample and to a significant increase in the apparent crystallite size at 330 °C. The high-temperature endo-peak can then be attributed to melting of the larger crystallites formed from the melt during isothermal crystallization at 330 °C. Using WAXS profiles, it was also possible to evaluate the volumetric coefficient of thermal expansion of the crystalline part of the studied polymer as CTEvol = 3.8·10−4 K−1.

This study demonstrates the advantages of using a hybrid compliant substrate containing a porous silicon (porSi) layer, obtained through electrochemical etching of the original silicon substrate, and a silicon carbide (SiC) layer, formed on its surface through the Kukushkin method, to grow high-quality, ultra-thin nanostructured Al?Ga1-xN/GaN heterostructures with nanocolumnar morphology by molecular beam epitaxy with plasma-activated nitrogen. Comparison of our experimental results with information from prior literature illustrates that the use of such a hybrid SiC/porSi substrate has a number of undeniable advantages for the growth of ultra-thin Al?Ga1-xN/GaN nanoheterostructures without the use of thick AIIIN buffer layers. Direct growth on a hybrid compliant substrate and SiC/porSi leads to a substantial relaxation of elastic stresses between the epitaxial film, porous silicon, and silicon carbide; this consequently affects the structural quality and optical characteristics of AIIIN nitride-based transistor ultra-thin structures. The experimental and computational data obtained in our research are important for understanding the physics and technology of Al?Ga1-xN/GaN nanoheterostructures, and they will contribute to their potential applications in optoelectronics.

We carried out a structural-spectroscopic study of AlGaN/GaN epitaxial layers grown by molecular-beam epitaxy with nitrogen plasma activation on a hybrid substrate containing layers of silicon carbide and porous silicon. Using X-ray diffractometry, Raman and photoluminescence spectroscopy, it is shown that thin films formed on a hybrid substrate have minimal residual stresses and intense photoluminescence.

AlGaAsSb and AlGaAs films as thick as 1 μm with Al content as high as 60% were successfully grown by low-temperature (200 °C) MBE. To overcome the well-known problem of growth disruption due to a high aluminum content and a low growth temperature, we applied intermittent growth with the temperature elevation to smooth out the emerging roughness of the growth front. Post-growth annealing of the obtained material allowed us to form a developed system of As or AsSb nanoinclusions, which occupy 0.3–0.6% of the material volume. While the As nanoinclusions are optically inactive, the AsSb nanoinclusions provide a strong optical absorption near the band edge of the semiconductor matrix due to the Fröhlich plasmon resonance. Owing to the wider bandgap of the grown Al0.6Ga0.4As0.97Sb0.03 compound, we have expanded the spectral range available for studying the Fröhlich plasmon resonance. The grown metamaterial represents an optically active medium of which the formation process is completely compatible with the epitaxial growth technology of semiconductors.

In this work, we studied the efficiency of introducing nanoporous silicon as a buffer layer in the growth of AlxGa1–xN/AlN/Si(111) on a single-crystal silicon by molecular beam growth technology. We also considered its influence on the morphological characteristics and atomic composition of the surface layers of heterostructures. As determined by X-ray diffraction, microscopic, and X-ray photoelectron methods, the heterostructure grown on Si(111) n-type monocrystalline silicon wafer with nanoporous por-Si buffer layer has a more homogeneous epitaxial layer, and the surface morphology of the layer is also more homogeneous.

The growth of GaN films on preliminarily treated Si(001) substrates by chloride–hydride vapor-phase epitaxy through a buffer layer is reported. It is demonstrated that the use of the technology proposed in the study brings about the formation of a Si transition sublayer in the Si substrate, so that further growth on this sublayer provides the formation of columnar GaN grains, between which there is a thin interlayer of the AlN phase. The epitaxial GaN film possesses low residual stresses, which is reflected in high-intensity luminescence.

HDPE-based nanocomposite fibers have been extruded from a melt and drawn up to draw ratio DR = 8. Two kinds of carbon nanodiscs (original ones and those exposed to additional annealing) have been used as fillers. Obtained nanocomposite fibers have been investigated with the help of different experimental methods: rheology, SEM and WAXS. It has been demonstrated that the annealed carbon nanodiscs possess a nucleation ability that finally leads to strong transformation of the material morphology.