In line with the modern trend of searching for inexpensive alternatives to noble-metal based catalysts, in the present work a comparative study of the process of carbon monoxide oxidation on the surface of the ternary system Mo-B-O, on the one hand, and the Au/TiO2(110) system, on the other hand, is carried out. Model systems of both types as substrates were created in a controlled way under ultrahigh vacuum (UHV) conditions and studied in situ by X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, low-energy electron diffraction, scanning tunneling microscopy, temperature-programmed reaction, and work function measurements. To form the Mo-B-O system, a 4-monolayer-thick film of boron atoms was first formed on the surface of the Mo(110) crystal, after which the formed film system was annealed to form a binary Mo-B compound. Then, this compound was oxidized in situ by oxygen admitted to the UHV chamber to form a ternary compound Mo-B-O with an atomically ordered surface structure of c(1 & times; 3)R30 degrees symmetry relative to bare Mo(110). The peculiarity of this system is its rather high efficiency of CO oxidation, comparable to that of the Au/TiO2 system, a prototype widely used in practical applications for low-temperature CO oxidation. The basis for such high efficiency of Mo-B-O is a significant transformation of the electronic state of both CO and O2 molecules during their co-adsorption. In addition to high catalytic activity, the Mo-B-O system exhibits high stability during the reaction, which, along with its low cost, can be a more acceptable alternative to the currently widely used Au/TiO2 catalyst.

Nickel foam (NF) has been recognized to have great application potential in catalysis. In this study, cobalt oxide (Co3O4) nanoarrays were synthesized on NF using a hydrothermal method and applied for carbon oxide-free (COX-free) production via ammonia (NH3) decomposition at atmospheric pressure. The application of varying hydrothermal temperatures from 80 degrees C to 180 degrees C enabled the synthesis of Co3O4 nanostructured arrays with diverse morphologies, presenting a novel approach to catalyst design. Among the synthesized catalysts, the optimal Co/NF-120-8 nanoarray catalyst synthesized with the hydrothermal temperature of 120 degrees C achieved 100 % NH3 conversion under a WHSV of 12,858 ml gcat-1 h-1 at 625 degrees C and maintained its activity for 45 h without noticeable degradation. SEM, TEM and XRD characterization results demonstrated that the hydrothermal temperature significantly influenced the morphologies, crystallite size and microstructure of the prepared catalysts, thereby affecting their catalytic performance for NH3 decomposition. XPS and H2-TPR measurements further indicated that the most abundant metallic Co and lattice oxygen were the key factors for the superior performance of NH3 decomposition over Co/NF-120-8 catalyst. Such a monolithic nanoarray catalyst proposed herein may open a new window in the efficient hydrogen production via NH3 decomposition and may also serve as a promising material in other heterogeneous reactions.

The adsorption and reaction of nitric oxide (NO) molecules on the surface of the model-supported metal/oxide system, consisting of Ni nanoparticles deposited on α-Al2O3 (0001) in ultra-high vacuum, have been studied using in situ surface-sensitive techniques and density functional theory (DFT) calculations. As a combination of X-ray and Auger electron spectroscopy (XPS, AES), Fourier-transform infrared (FTIR) spectroscopy, and temperature-programmed desorption (TPD) techniques reveals, there is a threshold of Ni particle mean size () of c.a. 2 nm, differentiating the electron state of adsorbed NO molecules and their reaction. The main feature of Ni particles normally not exceeding 2 nm is that the NO adsorbs in the form of (NO)2 dimers, whereas, for larger particles, the NO molecules adsorb in the form of monomers, usually characteristic for the bulk Ni substrate. This difference is demonstrated to be the main reason for the different reaction of NO molecules on the surface of Ni/alumina. The striking feature is that, in the case of ultra-small Ni particles ( ≤ 2 nm), the nitrous oxide (N2O) molecules are formed upon heating as a result of the NO self-reduction mechanism, which are otherwise not formed in the case of larger Ni particles. According to DFT results, this is due to the significant synergistic impact of NO co-adsorption on the neighboring NO dissociation reaction over ultra-small Ni particles, mediated by the metal/oxide perimeter interface. The observed molecular conversion effects offer an opportunity to tune the catalytic selectivity of this and related metal/oxide systems via varying the supported metal particle size.

To probe the properties of single atoms is a challenging task, especially from the experimental standpoint, due to sensitivity limits. Nevertheless, it is sometimes possible to achieve this by making corresponding choices and adjustments to the experimental technique and sample under investigation. In the present case, the absolute value of the electronic charge the Fe atoms acquire when they are adsorbed on the surface of aluminum oxide α-Al2O3(0001) was measured by a set of surface-sensitive techniques: low-energy ion scattering (LEIS), Auger electron spectroscopy (AES), low-energy electron diffraction (LEED), and work function (WF) measurements, in combination with density functional theory (DFT) calculations. The main focus was the submonolayer coverage of Fe atoms in situ deposited on the well-ordered stoichiometric α-Al2O3(0001) 7 nm thick film formed on a Mo(110) crystal face. An analysis of the evolution of the Fe LVV Auger triplet upon variation of the Fe coverage shows that there is electronic charge transfer from Fe to alumina and that its value gradually decreases as the Fe coverage grows. The same trend is also predicted by the DFT results. Extrapolation of the experimental Fe charge value versus coverage plot yields an estimated value of a single Fe atom adsorbed on α-Al2O3(0001) of 0.98e (electron charge units), which is in reasonable agreement with the calculated value (+1.15e). The knowledge of this value and the possibility of its adjustment may be important points for the development and tuning of modern sub-nanometer-scale technologies of diverse applied relevance and can contribute to a more complete justification and selection of the corresponding theoretical models.

A 5 nm thick polycrystalline Ni81Fe19 film was sputter-deposited onto a circular 3-inch diameter, 390 μm thick single-crystal wafer with SiO2 surface layers. The magnetoresistance (MR) of the sample was analyzed as a function of applied DC magnetic field and temperature using the Van der Pauw technique. Magnetic measurements were carried out over a temperature range of 25 °C to 350 °C using a Lake Shore Hall Effect Measurement System (HEMS). An external magnetic field ranging from +14 kG to −14 kG was applied at each temperature value to observe changes in resistance. Hall coefficients and resistance were obtained by applying current in both directions with different contact configurations. Machine learning techniques, including Random Forest Regression, were employed to predict magnetoresistivity beyond 350 °C; the best-performing model achieved R2 values up to 0.9449 with MSE as low as 0.0071, and enabled Curie temperature estimation with TC≈590.97 °C . This study highlights the potential of machine learning in accurately forecasting material properties beyond experimental limits, providing enhanced predictive models for the magnetoresistive behavior and critical temperature transitions of Ni81Fe19 .

Achieving a maximum thermoelectric figure of merit causes an increase in the efficiency of conversion processes by improving the thermoelectric properties of the material. In this regard, it is relevant to study the thermoelectric efficiency of chalcogenide semiconductor compounds and the efficiency of the conversion process of film converters based on them. The position of the maximum value of thermoelectric efficiency is predetermined by the scattering parameters and the ratio of the mobilities and effective masses of charge carriers. Increasing the thermoelectric efficiency of the material is achieved by optimizing the thermoelectric parameters by improving the properties, which leads to optimization of the concentration of charge carriers. Improving the thermoelectric properties of the material and increasing the efficiency of conversion processes is ensured when the concentration corresponds to the optimal value. The use of film transducers provides information in the process of monitoring and measuring physical quantities, as well as in the manufacture of high-tech products.

Due to the strong dependence on the intrinsic defectiveness of structures, semiconductor compounds based on metal chalcogenides have a wide spread in kinetic properties and high growth temperatures of materials, as well as a tendency to self-compensation of defects. It has been shown that an increase in defectivity in the cation sublattice leads to a decrease in ionic conductivity in copper chalcogenides, and an increase in temperature leads to an increase in ionic conductivity due to a change in mobility. The low activation energy indicates a strong intrinsic disorder of the cation part of the lattice. In copper chalcogenides, the presence of hopping conductivity at small deviations from stoichiometry is explained by compensation and a high concentration of vacancies. Under such conditions, this activation energy is the activation energy for the movement of copper ions throughout the crystal and almost all metal ions contribute to the ionic electrical conductivity. In semiconductor compounds based on metal chalcogenides with deviations from stoichiometry, the activation energy of cationic conductivity does not change, since the defects that arise in this case do not introduce large changes in ionic conductivity with temperature. The increase in ionic conductivity with increasing temperature is due to a change in mobility, since the carrier concentration remains unchanged. The latter is determined only by the structural features of the phases. Deviation from stoichiometry in compounds makes it necessary to take into account the movement of the main charge carriers in the allowed zones, and the movement of carriers along vacancies. The properties of metal chalcogenides are largely determined by the characteristics of their preparation and depend on the relative ratio of metal and chalcogen atoms, as well as the presence of intrinsic defects and their influence on the mechanism of behavior of charge carriers and transfer phenomena.

ABSTRACT It is demonstrated by means of ultra high vacuum (UHV) surface‐sensitive techniques and periodic density functional theory (DFT) calculations that the electronic and NO− adsorption properties of nanosized Ni clusters deposited onto the α‐Al 2 O 3 (0001) surface significantly depend upon the size of the cluster. The properties of the Ni cluster of the size of 2 nm and lower are predominantly determined by the formation of the Ni/Al 2 O 3 interface bond notably polarized towards the oxide. As a result, the metal cluster acquires a net positive charge manifested by the bond strengthening of adsorbed NO compared to the bulk Ni substrate. With the increasing size of the cluster, the Ni/Al 2 O 3 interfacial bond depolarizes due to the growing of lateral Ni–Ni interaction. With a mean coverage of Ni on the alumina surface exceeding 0.25 equivalent monolayers, their properties in terms of adsorption behavior of NO resemble those that are characteristic for the bulk Ni substrate. Such a size dependence offers an opportunity to tune the properties of metal clusters and the metal/oxide system as a whole, for example, to achieve the required electronic and adsorption‐reaction properties.

В настоящей статье представлены результаты инструментального исследования состава металла 18 артефактов Адайдонского и Эльхотовского некрополей кобанской культуры. Эти предметы погребального инвентаря датируются от про-токобанской до «классической» эпохи Кобани (период Кобан 1 А-Б - период Кобан III, по периодизации В. И. Козенковой). В результате исследования установлено, что украшения из металлической сурьмы были распространены на территории бытования кобанской культуры Кавказа не только на ранних этапах ее становления и развития («протокобанская эпоха»; период Кобан I А-Б), но и значительно позже, в предскифское - раннескифское время. Кроме того, в процессе исследования установлено, что металлическая сурьма использовалась древним населением, оставившим вышеотмеченные памятники, не только как основа металлоизделий (до 97-98 %), но и в ряде случаев в качестве легирующей добавки к меди для придания бронзовым изделиям дополнительной прочности и привлекательного внешнего вида. Также инструментальным методом установлено, что сурьма использовалась древними мастерами для изготовления инсигний и вотивных предметов (навершие булавы из Адайдонского могильника с содержанием сурьмы в 97 %). This paper analyzes the results of the instrumental examination of the metal composition of 18 artifacts from the Adaydon and Elkhotovo cemeteries of the Koban Culture in the Caucasus. These items of the funerary offerings date to the time span from the proto-Koban period to the «classical» Koban period (Koban I A-B period - Koban III period after V I. Kozenkova). The analysis found that the jewelry made of metallic antimony was spread in the region of the Koban culture of the Caucasus not only during the early stages of its evolvement and development («proto-Koban» period; Koban IA-B period), but also much later in the pre-Scythian - early Scythian period. Besides, the study showed that metallic antimony was used by the ancient population which left behind the aforesaid sites not only as metal to produce various items (up to 97-98 %) but also, in a number of cases, as an alloying element added to copper to improve its strength and durability as well as make it improve its appearance. The instrumental method also found that antimony was used by ancient artisans to make insignia and votive items (e. g. a macehead from the Adaydon cemetery with 97 % antimony content).

A method for measuring the resistive characteristics of channels in the blanks of microchannel plates was developed. Two probes were used for measurements, which minimized leakage currents through adjacent channels. The resistive properties of single channels of the microchannel insert in the reduced blank of MCP 18-10 were studied. It was established that the resistance of the channels depends on their position in the microchannel honeycomb. It was shown that the channels located in close proximity to the monolithic frame have less resistance compared to those located in the middle of a multicore glass honeycomb.

The article presents a method for one-sided etching of channel openings in unetched microchannel plate blanks using dilute hydrofluoric acid. In this work, we used the blanks of MCP 18-10 microchannel plates. The treatment was carried out in 0.2 N hydrofluoric acid solution at room temperature without oscillating or stirring the solution. Following etching, the diameter of channel openings increased by over 10

With the aim to find out the value of an electronic charge that the Fe atoms acquire when they are doped in Ge bulk, a set of experimental and density functional theory (DFT) studies have been carried out of the model systems consisting of intermixed Fe-Ge films. Such films were prepared by electron and thermal evaporation in ultra-high vacuum (UHV) on the surface of Mo(110) substrate by initial formation of the Ge film of a mean thickness of 75 nm, onto which the Fe films were subsequently deposited, maintaining certain Fe to Ge concentration ratio, namely, 0.2, 04, 0.7 and 1.0. Annealing of such double Fe-Ge films results in notable interdiffusion of the components with quite uniform distribution of the elements throughout the intermixed layer. The details of formation of such layers were in-situ controlled by Auger electron spectroscopy (AES), low-energy ion scattering spectroscopy (LEIS), low-energy electron diffraction (LEED) and work function measurements, in combination with Ar ion depth profiling. By analyzing the Fe Auger LMM-triplet, the absolute values of the charge that Fe atoms acquire when doped in Ge, were estimated for four different Fe-Ge intermixed layers with above-mentioned different Fe to Ge concentration ratio. The corresponding plot of the charge versus Fe to Ge concentration allows to estimate the charge of a single doped Fe atom, which equals to +0.34e (electron charge units) and gradually decreases to 0.07e for high Fe concentration. To verify the experimental values of the Fe charge the calculations were done by periodic DFT as implemented in full-potential FHI-aims code. Among the used algorithms of Mulliken, Hirshfeld, and Bader’s atoms-in-molecules, the latter gives good correlation between charges of Fe dopant and its concentration.

Introduction. Despite a fairly wide range of methods currently used for the chemical and elemental analysis of rocks and archaeological artifacts, many questions regarding the qualitative and quantitative accuracy of the analysis and the distribution of elements over the surface and volume of the sample with a high degree of locality remain open. In this regard, to solve these issues, in this work, for the first time, the method of X-ray photoelectron spectroscopy (XPS) was proposed and tested, which allows unambiguous and high-precision chemical identification of an object and the construction of its elemental map of the surface and volume. Materials and methods. The physical principles of the XPS method operation, which determine its record high qualitative and quantitative accuracy, are considered, a description of one of the most highly efficient X-ray photoelectron spectrometers Escalab 250 Xi, features of its operation and methods of adaptation for the study of rocks and archaeological artifacts are given. A special methodological advantage is the possibility of sample preparation and research under ultrapure conditions of ultrahigh vacuum. Results. XPS spectra were obtained in a wide range of photoelectron binding energies, which makes it possible to cover a fairly wide range of chemical elements that make up rocks and archaeological artifacts. With a high degree of spatial locality – at the level of 30 μm – elemental maps of the objects under study were built. Using the additional advantage of the method, based on the analysis of the energy position and the shape of the photoelectron spectral line, the chemical states of the elements that make up the samples were determined. Discussion. The obtained results of high-precision chemical analysis, combining both the general composition of the elements of the test sample as a whole and their spatial distribution with a high degree of locality, make it possible to achieve greater unambiguity in the identification of the objects under study compared to currently used analysis methods. Such high accuracy makes it possible to establish a correspondence between the composition of the rock and the archaeological artifact from the same area. The non-destructive nature of the XPS method, combined with ultrapure analysis conditions, makes it possible to ensure the safety of often unique objects. Conclusion. As a result of the study, it was shown that the XPS method can be quite effectively used for high-precision qualitative and quantitative analysis of rocks and archaeological artifacts, which is achieved both by the features of the method itself and by sample preparation and study of materials in ultrapure conditions of ultrahigh vacuum. The advantage of the method is the combination of a number of possibilities, such as not only the elemental, but also the chemical composition of objects, as well as the possibility of chemical mapping of the surface and analysis of the depth of the object with high spatial resolution. The research results can be used in solving a wide range of problems – from archeology to the development of mountainous areas, in particular, solving environmental problems by developing a scientific reserve for creating effective geochemical barriers. Further research should be focused on the development of techniques for adapting the XPS method to obtain three-dimensional tomographic models of the studied objects, which will improve the quality of their identification, in particular, from the point of view of geology and archeology.

The change in the resistive characteristics of lead silicate glasses (LSGs) after treatment in alkaline and acid solutions is studied. It is established that the chemical treatment of glasses and, accordingly, blanks of microchannel plates (MCPs) affects the high-temperature ionic conductivity at a constant activation energy of electrical conductivity. It is shown that the treatment of glasses in NaOH and HF solutions can significantly change the electrical resistance.

Three types of α-Mn2O3 catalysts with different well-defined morphologies (cubic, truncated octahedra and octahedra) and exposed crystal facets have been successfully prepared via hydrothermal processes, and evaluated for ethanol total oxidation with low ethanol concentration at low temperatures. The α-Mn2O3-cubic catalyst shows a superior catalytic reaction rate than that of α-Mn2O3-truncated octahedra and α-Mn2O3-octahedra under high space velocity of 192,000 mL/(g·h). Based on the characterization results obtained from XRD, BET, FE-SEM, HR-TEM, FT-IR, H2-TPR, XPS, ethanol-TPD, and CO-TPSR techniques, the observed morphology-dependent reactivity of α-Mn2O3 catalysts can be correlated to the good low-temperature reducibility, abundant surface Mn4+ and adsorbed reactive oxygen species, which was originated from the exposed (001) crystal planes. Through tuning the morphology and exposed (001) crystal facet of α-Mn2O3, a highly active ethanol oxidation catalyst with high selectivity and excellent stability is obtained. The developed approach may be applied broadly to the development of the design principles for high-performance low-cost and environmentally friendly Mn-based oxidation catalysts.

Electron Auger spectroscopy is used to study the surface segregation of gallium in diluted solid solutions of Al–Ga with volume concentrations of 1.1, 2.4, 4.2, 7.4 wt % Ga at temperatures of room temperature to 573 K. Considerable segregation of gallium is observed for all of the studied alloys. Values obtained for the surface concentration of Ga are used to construct the dependence of the energy of segregation on the surface concentration of Ga atoms at different temperatures.

A comparison of the surface of solid lithium in the atomically pure state, after contact with oxygen, nitrogen and after irradiation with N + ions with an energy of 0.6 keV at a current density of 2 μA/mm 2 was carried out. The analysis of surface characteristics was carried out using electron Auger spectroscopy. To obtain an atomically pure surface, low-energy electron bombardment was used. It is shown that the contact of an atomically pure Li surface with oxygen leads to the formation of lithium oxide, and with nitrogen with a partial pressure of 10 -6 Pa, lithium oxide and oxynitride in a mixture with free lithium atoms. Irradiation of lithium with nitrogen ions leads to the formation of the surface compound Li3N. It is noted that the resulting compound is unstable in ultrahigh vacuum and eventually decays to form lithium oxide due to interaction with the residual oxygen of the spectrometer chamber. Keywords: lithium, vacuum, ions, electrons, surface.

In-situ formation of boron thin films on the Mo(110) surface, as well as the formation of the molybdenum boride and its oxide and the trends of carbon monoxide catalytic oxidation on the substrates formed, have been studied in an ultra-high vacuum (UHV) by a set of surface-sensitive characterization techniques: Auger and X-ray photoelectron spectroscopy (AES, XPS), low-energy ion scattering (LEIS), reflection-absorption infrared spectroscopy (RAIRS), temperature-programmed desorption (TPD), electron energy loss spectroscopy (EELS) and work function measurements using the Anderson method. The boron deposited at Mo(110) via electron-beam deposition at a substrate temperature of 300 K grows as a 2D layer, at least in submonolayer coverage. Such a film is bound to the Mo(110) via polarized chemisorption bonds, dramatically changing the charge density at the substrate surface manifested by the Mo(110) surface plasmon damping. Upon annealing of the B-Mo(110) system, the boron diffuses into the Mo(110) bulk following a two-mode regime: (1) quite easy dissolution, starting at a temperature of about 450 K with an activation energy of 0.4 eV; and (2) formation of molybdenum boride at a temperature higher than 700 K with M-B interatomic bonding energy of 3.8 eV. The feature of the formed molybdenum boride is that there is quite notable carbon monoxide oxidation activity on its surface. A further dramatic increase of such an activity is achieved when the molybdenum boride is oxidized. The latter is attributed to more activated states of molecular orbitals of coadsorbed carbon monoxide and oxygen due to their enhanced interaction with both boron and oxygen species for MoxByOz ternary compound, compared to only boron for the Mox'By' double alloy.

Highly selective production of valuable ethylene from electrocatalytic CO2 reduction reaction (ECO2RR) is particularly desirable yet challenging. Morphology engineering is an effective strategy for catalyst design, which can adjust the electronic structure of catalyst surface, change the adsorption behavior of critical reaction intermediates over catalyst surface, and thus regulate the activity of electrocatalytic CO2 reduction reaction. In this work, we prepared copper phosphate catalysts with different morphologies and tested their catalytic activity for the ECO2RR in the flow cell. Compared with irregular flocculent aggregates, copper phosphate nanospheres exhibit a high and stable ethylene Faradaic efficiency of 47

Despite the recent activity in the field of studying the properties of systems formed during the adsorption of metal atoms on the surface of oxides, many questions of a fundamental nature remain open. Elucidation of the fundamental features of the behavior of systems of the type under consideration will improve the technological basis for the practical development and application of existing materials. In this regard, in the present work, the system Ni/Al2O3/Mo(110) is studied in ultrahigh vacuum using surface-diagnostic methods. Investigations using X-ray photoelectron and Auger electron spectroscopy, low-energy-ion backscattering spectroscopy, and Fourier-transform infrared spectroscopy show that the electronic and adsorption properties of nickel nanoclusters on the surface of aluminum oxide depend significantly on the cluster size. The properties of clusters no larger than 2 nm are determined by the formation of a bond polarized toward the oxide substrate at the Ni/Al2O3 interface. With growth of the cluster, depolarization of this bond occurs with redistribution of the electron density to lateral bonds between Ni atoms. Such a size dependence makes it possible to tune the properties of metal clusters and the metal-oxide system as a whole, for example, to achieve the required electronic and adsorption–reaction parameters.