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Multilayer Al/Cu foils have a high potential to be used as filler materials for diffusion welding or friction stir welding of difficult-to-weld materials. In this work, we study EB-PVD-deposited multilayer Al/Cu foils with the modulation periods (sum thickness of one Al layer and one Cu layer) of 50 nm and 1000 nm. The total composition for both the foils is of about Al--30 wt.% Cu and the total thickness is varied from 20 µm to 30 µm. The phase formations within the foils during heating up to 500°C are investigated by x-ray diffractometry, scanning and transmission electron microscopies, differential scanning calorimetry, and electrical-resistance measurement. The correlation between the modulation period and the formation of the Al2Cu, AlCu3, and Al4Cu9 phases is studied. The sequence, temperatures, and kinetics of phase transformations, as well as the heat of the reactions, are found to correlate significantly with the modulation period. Mechanisms of the phase formations within the foils and their mechanical properties are discussed. [ABSTRACT FROM AUTHOR]

Peri-implant bone tissue regeneration involves complex processes that are not yet fully understood at the cellular and molecular levels, leaving significant gaps in our knowledge that require further investigation. Aim. The study aimed to compare peri-implant osteogenesis on titanium femoral implants with alumina composite coatings applied by different methods to conventional titanium implants in an animal model. Materials and methods. Implants underwent sandblasting with silicon carbide, plasma torch treatment, and coating with titanium, corundum, sprayed titanium wire, or hydroxyapatite, resulting in seven different surfaces. 105 female Wistar rats received implants in their right femurs and were divided into 7 groups based on implant type and exposure duration (1, 2, or 4 weeks). Implant fragments were analyzed using scanning electron microscopy and energy dispersive X-ray spectroscopy to quantify chemical elements. Ratios of carbon to nitrogen and calcium to phosphorus were calculated. Data were analyzed using the U-Mann–Whitney test, with р < 0.05 as a significant value. Results. The energy dispersive X-spectrometry results confirmed morphological analysis findings by quantitatively and qualitatively assessing implants surface chemical composition. The key elements were evaluated, relevant for identifying bone tissue components like collagen (C and N) and hydroxyapatite (Ca and P), as well as implant coatings (Ti, Al, Ca, and P). Carbon and phosphorus showed fluctuations over time, with notable differences among groups. Aluminum appeared stable in some groups but varied in others. Calcium levels remained low initially and increased steadily in hydroxyapatite coated implants. Titanium levels were high initially, decreasing slightly over time. Morphological analysis correlated with surface roughness measurements. Notably, fibrin, collagen, and bone tissue presence varied among groups over time, with some groups showing significant mineralized bone tissue accumulation. After four weeks, blood clots persisted in some groups, while others exhibited bone tissue remodeling with the presence of osteoblasts and osteoclasts. Alumina-based coatings showed signs of degradation, with alumina cement scales found among macrophages and fibers. Conclusions. Our study found that stable bone implants outperform alumina-composite coatings in long-term osseointegration due to mechanical stability. Although ceramic composites initially enhance osteoinductive properties, better attachment to titanium substrates is needed. [ABSTRACT FROM AUTHOR]

An erbium-doped β -GaLaS3 crystal has been grown by the solution-melt method, and the effect of γ -irradiation on their vibrational and radiative properties has been investigated. Experiments have demonstrated that the crystal is transparent in the near and mid-infrared (IR) regions (transparency ∼62% in the range of 350–7100 cm−1), which allows it to be used as an effective matrix for creating lasers in this spectral range. For the first time, the vibrational spectrum of the crystal and the density of phonon states have been calculated using the density-functional theory (DFT) method. Both the original and γ -irradiated β -GaLaS3:Er crystals were investigated by Raman and IR spectroscopy. It has been established that irradiation with a dose of up to 5000 Gray does not lead to structural changes in the crystals. The effect of the formed defects is more clearly manifested in the IR reflection spectra, compared to the Raman spectra. The mechanism of the occurrence of excited states and the emission of Er ions embedded in the lattice has been established, and the effect of γ -irradiation on the radiative properties of β -GaLaS3:Er due to the occurrence of radiation-induced defects has been analyzed. A model has been constructed that explains the Stokes and anti-Stokes radiation of the erbium ions in the crystal. It has been demonstrated that the grown crystal has good prospects for sensor and laser technology of the near and mid-IR ranges due to relatively high values of optical transparency and the intense radiative capacity of the erbium ions. [ABSTRACT FROM AUTHOR]

Copyright of Progress in Physics of Metals / Uspehi Fiziki Metallov is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Progress in Physics of Metals / Uspehi Fiziki Metallov is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The review offers a comprehensive analysis of additive manufacturing (AM) processes in the application of high-entropy alloys (HEAs). HEAs have gained considerable attention in recent years due to their unique mechanical and physical properties. We provide the historical background and a clear definition of HEAs, outlining their development over time. The focus is concentrated on examining the utilization of AM processes in HEAs. Specifically, three prominent AM techniques are discussed: electron-beam processes, laser-processed HEAs, and wire-arc additive manufacturing. Each technique is explored in detail, including its advantages, restrictions, and current applications within the HEAs field. An attention is stressed on the significance of AM-process parameters during the fabrication of HEAs. Parameters such as laser power, scanning speed, and powder-feed rate are analysed for their influences on the microstructure and mechanical properties of the final product. The post-processing techniques for additive-manufactured HEAs are considered. The importance of steps such as heat treatment, surface finishing, and machining in achieving the desired material properties and dimensional accuracy in AMproduced HEA components is underlined. Overviewing the HEAs, their application in AM processes, the influence of process parameters, and post-processing considerations, this work can act as a useful source of information for researchers on the way to amendment of the understanding and implementation of AM in the HEAs. [ABSTRACT FROM AUTHOR]

Biomorphic carbon matrices (BCMs) were produced by pyrolysis from wood species of different forest and garden trees, after which the as-prepared BCMs were converted to SiC ceramics through their impregnation with liquid silicon and further heat-treatment. Both types of obtained samples were studied by scanning electron microscopy (SEM), Raman scattering (RS), and electron spin resonance (ESR) methods. The SEM data reveal that all BCM samples contain large (10–50 μm) and small (1–5 μm) micro-pores with surface densities ∼109 m−2 and 1011 m−2, respectively. Analysis of RS allowed to estimate carbon cluster sizes of about 5–11 nm depending on the sample type. The study of the electronic structure using ESR spectroscopy is carried out for BCM and SiC ceramics samples. Using theoretical analysis of the ESR spectra, it was found that spin resonance in BCMs is due to the contribution of three spin systems: free electron spins, "pseudo-free" electron spins from the tail of density states below the conduction band, and localized spins at dangling carbon bonds (DCBs). Their contributions depend on the ratio of different structural phases such as sp2-hybridized graphite-like carbon network and amorphous carbon phase. For most BCM samples, the large ESR line width is dramatically narrowed when samples are pumped out due to the exclusion of the broadening effect of molecular oxygen. The transformation of BCM into SiC by impregnation with liquid silicon can be clearly traced in the Raman spectra and in the ESR spectra. It is established that the electronic properties of synthesized SiC ceramics are due to the presence of residual graphite-like carbon nanoclusters. [ABSTRACT FROM AUTHOR]

Copyright of Progress in Physics of Metals / Uspehi Fiziki Metallov is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Aluminum nitride (AlN) film coatings on flexible substrates (polymeric Teflon, Mylar) have been obtained using a hybrid helicon-arc ion-plasma deposition technique with high adhesion of coatings. Studies of optical, morphological, and structural properties of AlN films have been carried out. It was found that AlN coatings on Teflon and Mylar thin-film substrates substantially suppress transmission of infrared (IR) radiation within the spectral range λ∼5-20 μm at certain technological parameters and thickness of AlN. Transmission in THz regions by using quasioptics attains T≈79%-95%, and losses measured in the channels within the microwave region 2 to 36 GHz are <0.06 dB. The obtained composite structures (AlN coatings on Teflon and Mylar thin-film substrates), due to a high thermal conductivity of AlN, could be used as efficient blocking structures in the infrared spectral range ("infrared stealth") withdrawing the heat from filters warmed by IR radiation. At the same time, they can be used as the transparent ones in the microwave and THz regions, which can be important for low-temperature detector components of navigation, positioning, and telecommunication systems due to reducing the background noise. [ABSTRACT FROM AUTHOR]

The photocatalytic properties of metal-containing nanocomposites based on crystalline graphite-like carbon nitride (CGCN), synthesized in situ by photoreduction of palladium, platinum, and gold ions in the reaction of hydrogen evolution from 96% ethanol under the action of visible light, were determined. The H2 formation rate increases in the sequence of CGCN/Au(1%) < CGCN Pd(0.4%) < CGCN/Pt(0.5%) at the optimal metal content in the composite. The efficiency of hydrogen evolution increases significantly even at half the metal content in the presence of HCl additives. The effective quantum yield of H2 formation is ~54% at 405 nm for the most active CGCN/Pt composite (0.25%). [ABSTRACT FROM AUTHOR]

Using the method of chemical synthesis, effective SERS substrates were developed, which were the films of gold nanoparticles possessing the form of stars. The peculiarity of star-shaped nanoparticles is that they could enhance the electric field of the radiating dipole not only by setting the frequency of the plasmon absorption band at the frequency of the exciting laser radiation, but additionally due to significant contribution to Raman scattering of the so-called "hot spots" that exist at the edges of the stars. "Nanostar"-based films were prepared using both direct deposition of gold nanoparticles from colloidal solution on the glass substrate and on the layer of polycation of polydiallyldimethyl ammonium bromide on the surface of glass substrates. Surface morphology of the obtained films was investigated using scanning electron microscopy. Plasmon absorption spectra were obtained using the method of optical absorption. Variation of geometrical parameters inherent to these nanostructures allows configuring the position of the plasmonic absorption band maximum close to the laser excitation wavelength. The coefficient of enhancement of Raman signal was evaluated for Rhodamine 6G molecules deposited on the designed SERS substrates (for different wavelengths of the exciting laser radiation, namely: λ = 633, 532 and 457 nm). [ABSTRACT FROM AUTHOR]