Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques最新文献

This work presents data on the X-ray diffraction analysis of air-dry, water-saturated, and working samples of the MFFK-G-025 and MMK-045 membranes obtained during microfiltration separation of process solutions. A decrease in crystallinity of the membrane samples is noted during their water saturation and operation, which affects the microfiltration separation of process solutions. The reduced peak intensities of the bands are analyzed in the X-ray diffraction patterns. Five distinct reflections responsible for the crystallinity of the membrane and four amorphous halos are observed in the diffraction patterns of all MFFK-G-025 membrane samples, and two distinct reflections responsible for the crystallinity of the membrane and two amorphous halos are visible in the MMK-045 membrane samples. The crystallinity of the MFFK-G-025 membrane decreased from 58.16 to 36.83, and that of the MMK-045 membrane from 33.51 to 20.21. The decrease in peak intensity in the diffraction patterns of working membrane samples compared to air-dry ones indicates a change in the structure of water in the membrane itself: molecular water becomes weakly bound liquid water. It can be assumed that the structural rearrangement of the macromolecules of the active layer of the MFFK-G-025 and MMK-045 membranes affects their conformation, i.e., a redistribution of the ratio of amorphous and crystalline segments of the membranes occurs.

In this paper, the formation process and time evolution of the crystal structure of thin films of yttria-stabilized zirconia ZrO₂:Y₂O₃ (YSZ) and gadolinia-doped ceria Ce_0.9Gd_0.1O₂ (GDC) were investigated. YSZ and GDC films for use as an electrolyte layer in microtubular solid oxide fuel cells were formed by reactive mid-frequency magnetron sputtering on WC-Co alloy substrates. The films were deposited in a vacuum setup specially designed for in situ X-ray diffraction studies of thin film growth using synchrotron radiation. It was shown that the texture of the formed films is determined by the substrate temperature. At a substrate temperature of 100‒187°C, YSZ and GDC films with a cubic crystal lattice are formed. Under such deposition conditions, YSZ films have a preferred orientation of (200), whereas for GDC films the preferred orientation changes from (111) to (220) during growth. To obtain YSZ and GDC films with a preferred orientation (111), which have the highest ionic conductivity, it is necessary to increase the mobility of adsorbed atoms by increasing the substrate temperature or applying a bias voltage to it. It was also shown that with the deposition parameters used, compressive residual stresses are formed in both films, which decrease slightly in amplitude with increasing film thickness due to the increase in grain size.

An approach to rapid (in less than 1 h) prototyping of X-ray microlenses from silica with an aperture of about 50 μm and a radius of curvature of 10 μm is presented. The formation of a concave microlens surface is achieved by using focused ion beam systems and isotropic etching in hydrofluoric acid. The presented approach allows obtaining a gain in the fabrication time by about 10 times compared to ion-beam lithography. Furthermore, the fabrication of a series of lenses will lead to a reduction in time costs proportional to the number of simultaneously processed lenses in an acid solution.

The paper examines the influence of the decay process of plasmon (Langmuir) excitations on secondary electron emission processes. An assessment of the lifetime of the plasmon excitation decay process is carried out. A connection is established between the relaxation process of plasmon excitations and the electron-photon emission yield. The electron-ion plasma of a solid body, interacting with an electron beam whose energy substantially exceeds the Fermi energy, is considered based on quantum electrodynamics. It is shown that the quantum description of plasmons leads to the concept of the electromagnetic vacuum of longitudinal Langmuir waves. The vacuum of longitudinal waves significantly alters the dielectric permeability of the solid-body plasma, resulting in the broadening and shifting of peaks associated with energy losses of fast electrons scattered by the solid. The interaction of plasmons with the plasmonic vacuum leads to the relaxation of plasma excitations and the generation of longitudinal photons. The relaxation mechanism of plasmons presented in this work helps to explain a number of seemingly anomalous phenomena, namely, the polarization of electron-photon emission observed at plasmonic frequencies and the features of the spectra of secondary electron emission at plasmonic energies observed during ion and electron bombardments. The paper presents a comparison of the spectra of electron-photon emission with the differential cross sections of inelastic energy losses of fast electrons due to plasmon excitation. Possible practical applications of the phenomena observed during the relaxation of collective excitations of solid-body plasma are discussed.

The results of studies on the effect of gamma radiation on polymer composites based on epoxy resin and bismuth oxide are presented. The surface microstructure and physical and mechanical characteristics were studied, and experimental studies of the effects of gamma quanta on the synthesized composites were carried out. It was found that the filler is evenly distributed over the entire surface of the composite during synthesis. With an increase in the content of bismuth oxide in the material from 0 to 60 wt % in increments of 20 wt %, flexural strength increases by 3.4–36.9%, while the tensile strength decreases slightly (by 15.0, 13.3, and 9.1% for 20, 40, and 60 wt % additives, respectively) compared with the additive-free sample. As a result of the study of the obtained composites for resistance to gamma radiation, it can be concluded that the composite containing 60 wt % bismuth oxide has the best radiation protection characteristics. The values of the linear and mass attenuation coefficients, as well as the half attenuation layer at a gamma-ray energy of 0.662 MeV for this material, were 0.096 cm^–1, 0.075 cm²/g, and 7.220 cm, respectively.

The study investigates the microstructure, phase composition, and hydrogen absorption properties of (TiVCr)_94.8Me_5.2(Me = Ni, Co, Zr) alloys to evaluate the influence of doping elements on hydrogen storage performance. Phase and microstructural analyses reveal the formation of multiphase systems, with distinct secondary phases depending on the additive. The research emphasizes the role of empirical parameters such as valence electron concentration (VEC), average electronegativity difference (EVD), and lattice parameter, rather than the conventional Ti/Cr = 0.75 ratio, in determining hydrogen storage properties. Results indicate that hydrogenation behavior correlates more strongly with EVD and lattice parameter than with VEC. Among the tested alloys, (TiVCr)_94.8Zr_5.2 exhibited the highest hydrogen capacity (1.79 wt %), along with superior kinetics and activation characteristics. The study also examines phase stability after hydrogen sorption/desorption cycles, noting transformations in secondary phases and their impact on performance. These findings suggest that optimizing hydrogen storage materials requires a holistic approach, balancing VEC, EVD, and lattice parameters, rather than adhering strictly to empirical compositional ratios. The insights gained can guide future alloy design for improved hydrogen storage efficiency under practical conditions.

Silicon-carbon films were deposited by electron beam evaporation of silicon carbide in helium, nitrogen and propane in the fore-vacuum pressure range of 3–4 Pa at various substrate temperatures. The composition, as well as optical and mechanical properties of the films were measured. We find that the composition of the films changes towards increased silicon content as the substrate temperature increases. This increases the film hardness and reduces the optical band gap. When deposited in helium and nitrogen, the films are enriched in silicon. Deposition in propane makes it possible to deposit films with a composition approaching stoichiometric.

The organometallic polymer UiO-66 was synthesized and characterized. Samples of the resulting material after drying at two different temperatures (100 and 300°C) were studied using various analytical methods. IR absorption spectra of the synthesized samples were recorded in the range from 500 to 3500 cm^–1, and the main absorption bands of the synthesized polymer UiO-66 were confirmed. The crystal lattice parameters of the samples for two temperatures were determined to be 20.10(5) Å at 100°C and 20.52(4) Å at 300°C, with the characteristic sizes of coherent scattering regions (CSR) of X-ray radiation being ~44 Å at 100°C and ~37 Å at 300°C. The specific surface area was calculated using the BET method, and the specific surface area of the sample after drying at 100°C was estimated to be S ~ 363 m²/g, while the characteristic size of microparticles was ~18 μm. As a result of the synthesis, a single-phase material with a type of X-ray diffraction pattern characteristic of UiO-66 was obtained. It has been shown that drying at 300°C structures the resulting material in the [111] direction, while other directions become amorphized.

A simple one-stage sol–gel technique for the synthesis of nanostructured ZnO films modified with Al has been developed. A comparative study of the effect of zinc oxide modification with aluminum, as well as the simultaneous action of methyl orange and ultraviolet radiation on their optical band gap, has been carried out. The contribution of each factor to the transformation of the band structure of the samples has been estimated. It has been shown that for all considered aluminum concentrations, the role of dye adsorption is predominant. A nonmonotonic dependence of the optical band gap of the material on the modifier content has been demonstrated, as well as its significant decrease upon dye adsorption and exposure to ultraviolet radiation. It has been suggested that the growth of the considered value in ZnO with an increase in the Al concentration to 2 at % is associated with the manifestation of the Burstein–Moss effect due to the filling of the lower levels of the conduction band with electrons. The results of the study of the samples by spectroscopy in the visible and ultraviolet wavelength ranges are supplemented by experimental data obtained using scanning electron microscopy. It was found that at all considered aluminum concentrations, the ZnO films are characterized by a nanostructured surface formed by intertwined “branches” of different sizes. A model is proposed that describes the fixation of methyl orange on the surface of the studied samples.

A combination of surface analysis methods and density functional theory calculations showed that the electronic and adsorption properties of nickel nanoclusters on the α-Al₂O₃(0001) film surface toward nitric oxide (NO) molecules strongly depend on the cluster size. The properties of Ni clusters with an effective size not exceeding 2 nm are mainly determined by the formation of a Ni–Al₂O₃ chemisorption bond polarized toward the oxide substrate. As a result, Ni nanoparticles acquire a positive charge, which strengthens the intramolecular bond of NO molecules adsorbed on their surface compared with adsorption on the surface of bulk Ni. With an increase in cluster size, the chemisorption bond is depolarized due to stronger lateral Ni–Ni interactions, and at a coverage thickness exceeding 0.25 equivalent monolayers, the adsorption properties become similar to those of bulk Ni. This size dependence of properties provides a means of controlling the electronic and adsorption characteristics of the metal cluster and the metal–oxide system as a whole.