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BACKGROUND: Extracorporeal membrane oxygenation (ECMO) has been widely used in patients with COVID-19, but uncertainty remains about the determinants of in-hospital mortality and data on post-discharge outcomes are scarce. The aims of this study were to investigate the variables associated with in-hospital outcomes in patients who received ECMO during the first wave of COVID-19 and to describe the status of patients 6 months after ECMO initiation.METHODS: EuroECMO-COVID is a prospective, multicentre, observational study developed by the European Extracorporeal Life Support Organization. This study was based on data from patients aged 16 years or older who received ECMO support for refractory COVID-19 during the first wave of the pandemic-from March 1 to Sept 13, 2020-at 133 centres in 21 countries. In-hospital mortality and mortality 6 months after ECMO initiation were the primary outcomes. Mixed-Cox proportional hazards models were used to investigate associations between patient and management-related variables (eg, patient demographics, comorbidities, pre-ECMO status, and ECMO characteristics and complications) and in-hospital deaths. Survival status at 6 months was established through patient contact or institutional charts review. This study is registered with ClinicalTrials.gov, NCT04366921, and is ongoing.FINDINGS: Between March 1 and Sept 13, 2020, 1215 patients (942 [78%] men and 267 [22%] women; median age 53 years [IQR 46-60]) were included in the study. Median ECMO duration was 15 days (IQR 8-27). 602 (50%) of 1215 patients died in hospital, and 852 (74%) patients had at least one complication. Multiorgan failure was the leading cause of death (192 [36%] of 528 patients who died with available data). In mixed-Cox analyses, age of 60 years or older, use of inotropes and vasopressors before ECMO initiation, chronic renal failure, and time from intubation to ECMO initiation of 4 days or more were associated with higher in-hospital mortality. 613 patients did not die in hospital, and 547 (95%) of 577 patients for whom data were available were alive at 6 months. 102 (24%) of 431 patients had returned to full-time work at 6 months, and 57 (13%) of 428 patients had returned to part-time work. At 6 months, respiratory rehabilitation was required in 88 (17%) of 522 patients with available data, and the most common residual symptoms included dyspnoea (185 [35%] of 523 patients) and cardiac (52 [10%] of 514 patients) or neurocognitive (66 [13%] of 512 patients) symptoms.INTERPRETATION: Patient's age, timing of cannulation (FUNDING: None.

The development and production of thin-film coatings having very low friction is an urgent problem of materials science. One of the most promising solutions is the fabrication of special nanocomposites containing transition-metal dichalcogenides and various carbon-based nanophases. This study aims to explore the influence of graphite-like carbon (g-C) and Ni interface layers on the tribological properties of thin WS

The thermochemical treatment of tungsten trioxide (WO3) nanostructured films in hydrogen sulfide to obtain tungsten disulfide (WS2) layers in the WS2/WO3 hybrid structure is studied. The temperature and treatment time influence the structural-phase state, morphology, optical properties of a WS2/WO3/FTO photocathode (on fluorinated tin oxide (FTO) substrates), and its photoelectrocatalytic activity in the hydrogen evolution reaction in acidic solution is established. The sulfidation of WO3 nanoneedle films leads to the formation of a WS2/WO3 nanocrystalline hybrid structure under optimal conditions, which provides the separation of photogenerated carriers (electrons and holes) at the interphase boundaries (heterojunctions) necessary for the efficient photoactivated hydrogen evolution reaction according to Z scheme. The calculations of thermodynamic properties of the WS2/WO3 hybrid nanocatalyst show that synergistic effect of nanophases is possible in it to increase the catalytic activity of hydrogen evolution both on the basal planes of WS2 nanoclusters and on the surface of metal oxide nanoclusters.

The influence of the chemical state of a WOy thin-film precursor on formation of WSe2 nanofilms under rapid selenization on a glassy carbon substrate at 900°C is studied. A nanolayer of amorphous molybdenum sulfide (MoSx ~ 3), which has high catalytic activity in the electrochemical reaction of hydrogen evolution, is applied onto the surface of the obtained WSe2 films by pulsed laser deposition. It is shown that the composition of the WOy thin-film precursor has a significant effect on the morphology of the WSe2 nanolayers, and this characteristic largely determines the efficiency of hydrogen evolution by the MoS3/WSe2 heterostructure upon photoactivated water splitting. The most efficient hydrogen evolution is found for the MoS3/WSe2 photocathode heterostructure containing WSe2 in the form of crystal petals of ~50 nm in thickness, with these crystals oriented perpendicular to the substrate surface. A theoretical analysis of the possible effect of synergistic interaction at the MoS3/WSe2 interface on the efficiency of hydrogen evolution is carried out. Density functional theory calculations have shown that MoS3 clusters can increase the efficiency of the hydrogen evolution reaction upon contact with surface regions of WSe2 nanocrystals different in atomic packing.

Features of thermochemical treatment of nanostructured tungsten trioxide (WO3) films in hydrogen sulfide aimed at the formation of tungsten disulfide (WS2) nanolayers in the hybrid WS2/WO3 structure are investigated. The effect of temperature and treatment time on the structure, chemical state, morphology, and optical properties of the WS2/WO3/FTO photocathode (on the fluorinated tin oxide substrate), as well as on its photoelectrocatalytic activity in the reaction of hydrogen evolution in an acidic solution has been established. It is shown that sulfurization of nano-needle WO3 films under optimal conditions leads to the formation of a nanocrystalline hybrid WS2/WO3 structure that ensures the separation of photogenerated carriers (electrons and holes) at interphase boundaries (heterojunctions). This facilitates the efficient photo-activated hydrogen evolution reaction according to the Z-scheme. First-principal calculations of the thermodynamic properties of the hybrid WS2/WO3 nanocatalyst showed that a synergistic effect of nanophases is possible. This increases the catalytic activity of hydrogen evolution on both the basal planes of WS2 nanoclusters and the surface of metal oxide nanoclusters.

MoS2 nanofilms were created by thermochemical processing (sulfurization) of thin-film Мо and МоОу precursors in S vapor. The precursor films were created by pulsed laser deposition. The obtained molybdenum disulfide films consisted of 2H-MoS2 nanocrystals with laminar packing of basal planes oriented perpendicular to the film surface. The increase in the sulfurization temperature from 500°C to 800°C provided better quality of local packing and, as a consequence, reduction of electric resistance, higher concentration of carriers (electrons) and their mobility. The application of metal oxide precursor МоОу resulted in higher efficiency of synthesis of high quality MoS2 nanofilms. The efficiency of activation of the electrochemical processes of hydrogen production in an acidic solution was lower with crystalline MoS2 nanofilms than with amorphous MoSx films. Nanocrystalline MoS2 films, however, manifested improved photo- and electrocatalytic characteristics in activation of reactions of hydrogen and oxygen evolution in an alkaline solution.

The mechanisms of film formation during pulsed laser ablation of a MoS2 target were studied. The conditions for the deposition of laser erosion plume were determined. This made it possible to obtain coatings with a porous structure consisting of round Mo nanoparticles coated with a thin shell of amorphous molybdenum sulfide MoSx > 2. Due to its hybrid structure, the MoSx > 2/Mo nanomaterial can be effectively used for electro- and photocatalysis of water splitting. The MoSx > 2/Mo films deposited on a glassy carbon substrate are characterized by good current transport and high active surface area. When the film thickness increased due to the increased deposition time, the overvoltage of hydrogen evolution in an acid solution monotonically decreased to 142.5 mV, which was necessary in order to obtain current density of hydrogen evolution of 10 mA/cm2. The catalyst loading was 230 μg/cm2. Further increase in the loading did not significantly reduce the overvoltage. The results indicate that it is promising to use Mo nanoparticles as an ultrafine support for the catalytic nanolayers of amorphous molybdenum sulfide.

The possibility of using physicochemical methods for treating a nickel foam to increase its electrocatalytic activity in hydrogen and oxygen evolution reactions in an aqueous alkaline solution was studied. The modification of a 1-mm-thick sheet of the foam was carried out through its surface and included physical deposition of pulsed laser plasma for the formation of catalytic MoSx and MoSxSey films, followed by their annealing. The effect of foam pretreatment by sulfurization in H2S under varying conditions and formation of catalytic layers with different structures and compositions was studied. The best improvement in the electrocatalytic performance of the foam was exerted by thin-film coatings of molybdenum sulfide and sulfide/selenide with a nanocrystalline structure formed on the surface of a foam with a Ni3S2 underlayer. The possibility of a synergetic effect of the formed phases was analyzed by DFT calculations. For the optimum composition of the modified layers, the overvoltage of H2 evolution (for a current density of 10 mA/cm2) decreased to 155 mV, and the overvoltage of O2 evolution did not exceed 160 mV. The electrocatalytic characteristics obtained by this treatment are not inferior to those for the best modern electrocatalysts created on nickel foam by widely used methods of hydrothermal synthesis or electrodeposition.

To obtain Mo–S–C thin-film coatings on steel substrates with varying structural and chemical states, pulsed laser codeposition method was used at room temperature, including the first ever use of reactive codeposition of Mo and C in H2S. The conditions are determined for obtaining sufficiently smooth layers with optimal local packing of atoms in amorphous MoSx and diamond-like carbon nanophases, which yielded relatively high wear resistance and a low sliding friction coefficient (~0.1) in air without a long running-in phase.

We present the results of a comparative investigation of the friction and wear characteristics of MoSx and MoSex coatings in an oxidizing medium (argon–air mixture) at a temperature of –100°C. Thin films of these solid lubricants were manufactured by pulsed laser deposition using MoS2, MoSe2, and Mo targets in vacuum and H2S. It was established that S-containing coatings ensured a friction coefficient of ~0.09 and were much superior to S-containing coatings in respect of wear. The properties of MoSx coatings depended on the concentration of S that determined the local atomic packing in the amorphous structure of the film. The friction coefficient of MoS3 coating after running-in was half as small as that of MoS2 and amounted to 0.08.

We studied the possibility of using pulsed laser deposition (PLD) for the formation of a MoSx/WSe2 heterostructure on a dielectric substrate. The heterostructure can be employed for effective solar water splitting to produce hydrogen. The sapphire substrate with the conducting C(B) film (rear contact) helped increase the formation temperature of the WSe2 film to obtain the film consisting of 2H-WSe2 near-perfect nanocrystals. The WSe2 film was obtained by off-axis PLD in Ar gas. The laser plume from a WSe2 target was directed along the substrate surface. The preferential scattering of selenium on Ar molecules contributed to the effective saturation of the WSe2 film with chalcogen. Nano-structural WSe2 film were coated by reactive PLD with a nanofilm of catalytically active amorphous MoSx~4. It was established that the mutual arrangement of energy bands in the WSe2 and MoSx~4 films facilitated the separation of electrons and holes at the interface and electrons moved to the catalytically active MoSx~4. The current density during light-assisted hydrogen evolution was above ~3 mA/cm2 (at zero potential), whilst the onset potential reached 400 mV under irradiation with an intensity of 100 mW/cm2 in an acidic solution. Factors that may affect the HER performance of MoSx~4/WSe2/C(В) structure are discussed.

This work studies the factors that affect the efficiency of the photoelectrochemical hydrogen evolution reaction (HER) using MoSx/WO3 nano-heterostructures obtained by reactive pulsed laser deposition (RPLD) on glass substrates covered with fluorinated tin oxide (FTO). Another focus of the research is the potential of MoSx nanofilms as a precursor for MoOz(S) nanofilms, which enhance the efficiency of the photo-activated oxygen evolution reaction (OER) using the MoOz(S)/WO3/FTO heterostructures. The nanocrystalline WO3 film was created by laser ablation of a W target in dry air at a substrate temperature of 420 &deg, C. Amorphous MoSx nanofilms (2 &le, x &le, 12) were obtained by laser ablation of an Mo target in H2S gas of varied pressure at room temperature of the substrate. Studies of the energy band structures showed that for all MoSx/WO3/FTO samples, photo-activated HER in an acid solution proceeded through the Z-scheme. The highest photoelectrochemical HER efficiency (a photocurrent density ~1 mA/cm2 at a potential of ~0 V under Xe lamp illumination (~100 mW/cm2)) was found for porous MoS4.5 films containing the highest concentration of catalytically active sites attributed to S ligands. During the anodic posttreatment of porous MoSx nanofilms, MoOz(S) films with a narrow energy band gap were formed. The highest OER efficiency (a photocurrent density ~5.3 mA/cm2 at 1.6 V) was detected for MoOz(S)/WO3/FTO photoanodes that were prepared by posttreatment of the MoSx~3.2 precursor. The MoOz(S) film contributed to the effective photogeneration of electron&ndash, hole pairs that was followed by the transport of photoelectrons from MoOz(S) into the WO3 film and the effective participation of holes possessing strong oxidation ability in the OER on the surface of the MoOz(S) film.

We studied the tribological properties of amorphous molybdenum sulfide (MoSx) thin-film coatings during sliding friction in an oxidizing environment at a low temperature (&minus, 100 &deg, C). To obtain films with different sulfur contents (x ~ 2, 3, and 4), we used reactive pulsed laser deposition, where laser ablation of the Mo target was performed in H2S at various pressures. The lowest coefficient of friction (0.08) was observed during tribo-testing of the MoS3 coating. This coating had good ductility and low wear, the wear of a steel counterbody was minimal. The MoS2 coating had the best wear resistance, due to the tribo-film adhering well to the coating in the wear track. Tribo-modification of the MoS2 coating, however, caused a higher coefficient of friction (0.16) and the most intensive wear of the counterbody. The MoS4 coating had inferior tribological properties. This study explored the mechanisms of possible tribo-chemical changes and structural rearrangements in MoSx coatings upon contact with a counterbody when exposed to oxygen and water. The properties of the tribo-film and the efficiency of its transfer onto the coating and/or the counterbody largely depended on local atomic packing of the nanoclusters that formed the structure of the amorphous MoSx films.

The ability to increase the efficiency of electrochemical H2 and O2 evolution reactions in an alkaline solution using nickel-foam-based electrodes has been studied. To improve the catalytic properties of the foam, it was subjected to complex modification via sulfurizing in sulfur-containing gaseous media and the additional formation of amorphous or crystalline MoSx nanolayers. The foam was sulfidized in hydrogen sulfide or sulfur vapor at a temperature of 400°C. Amorphous MoSx films were produced via pulsed laser deposition from a MoS2 target in an H2S atmosphere. To obtain nanocrystalline catalytic MoSx layers, thin-film Mo precursors were preliminarily applied to the foam pre-sulfurized in sulfur vapor at 400°C. The deposition of precursors was carried out in vacuum at 22°C. After deposition, the foam with precursors was oxidized in air at 600°C. The modified samples were probed via scanning electron microscopy involving microanalysis and Raman spectroscopy. The effect of the precursor layer thickness on the sulfurizing efficiency and phase composition of the modified layers was established. The amorphous layer deposition was found to have a strong impact on only the O2 evolution. The crystalline layers obtained via sulfidizing of Mo-containing precursors exerted influence on both the cathodic and anodic reactions. The hydrogen overvoltage at a current density of 10 mA/cm2 was −160 mV, and the oxygen overvoltage was below 150 mV, which corresponded to the best electrocatalysts on the nickel foam after the volume modification via conventional chemical treatment (hydro- and solvothermal synthesis).

The amorphous rapidly quenched quasi-binary TiNi–TiCu alloys containing 30–38 at.% Cu were crystallized by isothermal annealing at 500 °C for 300 s and by exposing to short electric pulse with a duration of 10 ms to study the effect of the annealing rate on their properties. The results obtained showed that electropulse crystallization fundamentally changed the microstructure of the alloys due to almost completely hindering the formation of brittle Ti-Cu phases. This leads to a significant increase in the enthalpy of the martensitic transformation and a considerable shift of the transformation range towards higher temperatures. It was found that reducing the crystallization time dramatically increases the plasticity and shape memory effect of the alloys.

Hydrogen sensors were fabricated with a well-known structure, formed by depositing WOx films (with or without an additional Pt overlayer) onto SiC substrates. These sensors differed in terms of the morphology and nanostructure of the WOx films, which were pulsed laser deposited (PLD) under varying conditions. The sensory characteristics of WOx/SiC and Pt/WOx/SiC samples were analyzed using conventional current–voltage measurements. In addition, the possibility of detecting an electrical signal in these structures without applying an external voltage (EMF-powered mode) was investigated. The sensor response strongly depended on the qualities of the metal oxide film, including its strength, uniformity, continuity, and adhesion to the SiC substrate. Optimization of the PLD allowed the formation of triclinic WOx 27 times. The highest voltage detected for an external load of 1 kΩ was ~400 μV. The Pt film deposition markedly worsened the sensory properties of Pt/WOx/SiC structures measured by the EMF-powered mode. Possible mechanisms of the appearance of the EMF in the prepared structures are considered.

Pulsed laser ablation of MoS2 and WO3 targets at appropriate pressures of background gas (Ar, air) were used for the preparation of new hybrid nanostructured catalytic films for hydrogen production in an acid solution. The films consisted of a nanostructured WO3&minus, y underlayer that was covered with composite MoS3/np-Mo nanocatalyst. The use of dry air with pressures of 40 and 80 Pa allowed the formation of porous WO3&minus, y films with cauliflower- and web-like morphology, respectively. The ablation of the MoS2 target in Ar gas at a pressure of 16 Pa resulted in the formation of amorphous MoS3 films and spherical Mo nanoparticles. The hybrid MoS3/np-Mo//WO3&minus, y films deposited on transparent conducting substrates possessed the enhanced (photo)electrocatalytic performance in comparison with that of any pristine one (MoS3/np-Mo or WO3&minus, y films) with the same loading. Modeling by the kinetic Monte Carlo method indicated that the change in morphology of the deposited WO3&minus, y films could be caused by the transition of ballistic deposition to diffusion limited aggregation of structural units (atoms/clusters) under background gas pressure growth. The factors and mechanisms contributing to the enhancement of the electrocatalytic activity of hybrid nanostructured films and facilitating the effective photo-activation of hydrogen evolution in these films are considered.

Structural features of CBx films obtained by pulsed laser ablation of targets made of pressed diamond powder with boron-powder additions at B/C atomic ratio of x = 0.33 have been studied. The films were deposited on heated substrates, so that diffusion processes involving C and B atoms on the surface and in the volume of films were possible. Selected conditions of film deposition ensured their effective doping with boron (0.4 ≤ x ≤ 0.6). The incorporation of B atoms was accompanied by the formation of B–C chemical bonds, whereas the formation of sp2 graphite bonds and their ordering in clusters with laminar packing was suppressed. The films possessed very low resistivity (~1.4 mΩ cm) at room temperature and exhibited metallic type of conductance on decreasing the temperature to 77 K.

Pulsed laser ablation of a MoS2 target causes enhanced splashing of the material. So, for MoSx films obtained by pulsed laser deposition (PLD) in the conventional normal incidence (NI) configuration, their typical morphology is characterized by an underlying granular structure with an overlayer of widely dispersed spherical Mo and MoSx particles possessing micro-, sub-micro- and nanometer sizes. We investigated the possibility of using high surface roughness, which occurs due to particle deposition, as a support with a large exposed surface area for thin MoSx catalytic layers for the hydrogen evolution reaction (HER). For comparison, the HER performance of MoSx layers formed by grazing incidence (GI) PLD was studied. During GI-PLD, a substrate was placed along the direction of laser plume transport and few large particles loaded the substrate. The local structure and composition of thin MoSx layers formed by the deposition of the vapor component of the laser plume were varied by changing the pressure of the buffer gas (argon, Ar). In the case of NI-PLD, an increase in Ar pressure caused the formation of quasi-amorphous MoSx (x ≥ 2) films that possessed highly active catalytic sites on the edges of the layered MoS2 nanophase. At the same time, a decrease in the deposition rate of the MoSx film appeared due to the scattering of the vapor flux by Ar molecules during flux transport from the target to the substrate. This effect prevented uniform deposition of the MoSx catalytic film on the surface of most particles, whose deposition rate was independent of Ar pressure. The scattered vapor flux containing Mo and S atoms was a dominant source for MoSx film growth during GI-PLD. The thickness and composition distribution of the MoSx film on the substrate depended on both the pressure of the buffer gas and the distance from the target. For 1.0–2.5 cm from the target, the deposition rate was quite sufficient to form S-enriched quasi-amorphous MoSx (2.5

To fabricate an electrocatalyst containing nanostructured layers of WOy and MoS x , a sequential formation of tungsten oxide and molybdenum sulfide thin films is performed by means of the pulsed laser deposition of W and Mo in low-pressure air and hydrogen sulfide media, respectively. The reactive medium pressure and the substrate (glassy carbon) temperature are varied during and after the deposition. WOy thin films of various morphologies and structures determining certain differences in their catalytic properties in the reaction of hydrogen evolution in acidic solutions are obtained. However, the catalytic efficiency of the obtained WO y nanoelements (spheres, needles, and sheets) with amorphous and crystalline structures appears to be insufficient. Additional deposition of MoS x with an amorphous structure results in a significant improvement of the catalytic properties. Sulfur atoms in the MoSx amorphous matrix cause the formation of catalytically active sites, while the developed surface of the WO y stimulates an increase in the catalyst total active area. Penetration of hydrogen effectively formed on MoS x into the bulk of thin films of WO y provides a crucial electrocatalysis condition—low current resistance in the support layer with a large exposed surface area.

The peculiarities of pulsed laser ablation of MoSe2 targets which caused the formation of a complex plume containing atoms (Mo and Se) and Mo nanoparticles (Mo-NPs) have been studied. Investigations of the composition, structure, and catalytic activity toward the hydrogen evolution reaction (HER) for MoSex/Mo-NPs films prepared by pulsed laser deposition (PLD) in a vacuum and in a buffer He gas were carried out. For He pressure of 30 Pa, a shock wave could be the dominant mechanism of material transport, resulting in the deposition of an Se-enriched flux of chemically active atoms and leading to the growth of amorphous films with an increased Se content. Mo nanoparticles allowed for a larger surface area of the MoSex∼3.1/Mo-NPs catalyst deposited 5 cm from the target. However, for deposition in He at 10 cm, the amount of Mo NPs in the film appreciably decreased. Factors that could impact on the transport of nanoparticles through a buffer gas were considered. The amorphous MoSex∼3.1/Mo-NPs films prepared by PLD in He gas exhibited excellent HER performance. Quasicrystal MoSex

This paper presents experimental results on the synthesis of boron rich diamond-like carbon phases (BCx) obtained by high pressure sintering (s-BCx) and pulsed laser deposition (PLD-BCx). It has been shown that sintering of a mixture of a powder of micro-diamonds with a powder of boron in the toroid type high pressure device leads to the creation of s-BCx phase with a low resistivity, and high elastic moduli. The PLD-BCx film found to be rigid with the resistivity as low as that of best conductive boron–doped diamond films. It indicates that the presence of B atoms in a laser plasma leads to the formation of sp3 bonds in the material in the process of chemical sputtering. The combination of unique characteristics can be achieved by changing the ratio B/C.

Laser-initiated modification of the structure and morphology of the MoS2 and MoSe2 targets used to obtain antifriction thin-film coatings by pulsed laser deposition were studied. Significant differences were revealed in the ablation mechanism of these materials that caused important differences in the structure formation of MoS x /Mo and MoSe x /Mo coatings containing submicro- and nano-scaled Mo particles. Results of the study of structure, morphology and tribological properties of these coatings (coefficient of friction, wear resistance) when testing by the technique of sliding the ball over the covered disk under different air humidity and temperatures are presented. Comparative studies have revealed the superiority of the MoSe x /Mo coatings over the MoS x /Mo coatings during sliding friction under varying conditions of applications in frictional unites.

We report the preparation of MoS x thin films with reactive pulsed laser deposition (RPLD), an original technique that allows us to investigate the correlation between key MoS x properties, such as the composition, morphology, and local structure, and the catalytic performance in the hydrogen evolution reaction (HER). The use of two geometries of normal angle (NA) and sliding angle (SA) for the deposition by laser plume from a Mo target on a glassy carbon substrate made it possible to regulate the characteristics of MoS x films (1.5 ≤ x ≤ 10) by varying the H 2 S pressure and thus to circumvent the limitations inherent in traditional pulsed laser deposition. Amorphous MoS x , quasi-crystalline layered MoS 2 , disordered as well as rather perfect Mo 3 –S clusters, and sulfur clusters were formed. The films containing locally ordered clusters with a higher content of bridging S 2 2 − and apical S 2 − ligands could be prepared by SA RPLD. This film was demonstrated to be the most efficient electrocatalyst, possessing a lower overpotential of − 130 mV at a current density of − 1 mA/cm 2 , a Tafel slope of 44 mV/dec, and a quite high exchange current density of ~ 1.2 μA/cm 2 . The preparation of a low-resistance MoS x underlayer by NA RPLD made it possible to increase the catalytic performance of a bilayer coating by 10%.

Systematic and in-depth studies of the structure, composition, and efficiency of hydrogen evolution reactions (HERs) in MoSx films, obtained by means of on- and off-axis pulsed laser deposition (PLD) from a MoS2 target, have been performed. The use of on-axis PLD (a standard configuration of PLD) in a buffer of Ar gas, with an optimal pressure, has allowed for the formation of porous hybrid films that consist of Mo particles which support a thin MoSx~2+δ (δ of ~0.7) film. The HER performance of MoSx~2+δ/Mo films increases with increased loading and reaches the highest value at a loading of ~240 μg/cm2. For off-axis PLD, the substrate was located along the axis of expansion of the laser plume and the film was formed via the deposition of the atomic component of the plume, which was scattered in Ar molecules. This made it possible to obtain homogeneous MoSx~3+δ (δ~0.8–1.1) films. The HER performances of these films reached saturation at a loading value of ~163 μg/cm2. The MoSx~3+δ films possessed higher catalytic activities in terms of the turnover frequency of their HERs. However, to achieve the current density of 10 mA/cm2, the lowest over voltages were −162 mV and −150 mV for the films obtained by off- and on-axis PLD, respectively. Measurements of electrochemical characteristics indicated that the differences in the achievable HER performances of these films could be caused by their unique morphological properties.

The influence of pulsed laser deposition conditions in the geometry “off-axis” on the catalytic properties of MoS x films in the hydrogen evolution reaction is investigated. For the deposition of MoS x films from MoS2 target, pulsed laser radiation from the IR and UV wavelength ranges was used. The angle of incidence of the laser-induced plume on the surface of the substrate in a buffer gas was varied to check the influence of large in-size Mo-enriched particles. The efficiency of the catalyst was estimated from the results of the turnover frequency (TOF) measurement, which made it possible to minimize the influence of the “loading” of the catalyst on its characteristics. The effects of the chemical composition, local structure, and properties of the catalyst–substrate interface on the efficiency of the hydrogen evolution reaction are analysed. The regime of pulsed laser deposition of more effective thin-film MoS x catalysts is determined.

The results of structural and electrochemical studies of thin Mo-S-P films obtained by pulsed laser deposition at various conditions from a target made of mixture of MoS2 and P powders are presented. For variation of S/P ratio and modification structure of the catalytic films, the deposition of the laser plume was conducted in vacuum, in Ar and H2S gas. The highest electrocatalytic properties for activating the hydrogen evolution reaction in an acid solution were found for composite amorphous/nanocrystalline MoS6P/nc-Mo films. In the chemical stateof S 2p, the high binding energy dominated. The doping of the films with phosphorus increased the efficiency of the reaction compared with that of MoS x /nc-Mo films. The analysis of the synergistic effect of phosphorus on the performance of amorphous MoS x P y films in H2 evolution was carried out using the density functional theory.

The paper deals with the development of a structural composite material exhibiting two-way shape memory effect. A Ti-Ni-Cu alloy was produced by the melt spinning technique at different cooling rates in the form of a ribbon with a thickness of approximately 40 μm. Layered amorphous-crystalline structure of the ribbon was obtained by varying the alloy composition and the cooling rate and by modification of the alloy structure with the external extreme action (pulsed laser emission and periodical discharge in the liquid flow). The relation between thicknesses of the amorphous and crystalline layers was changed by the variation of parameters of the melt spinning and the external actions as well as with the aid of electrochemical polishing. The samples were characterized by means of inverted metallographic and scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, energy dispersive X-ray analysis and microhardness measurements. It has been shown that the layered amorphous-crystalline composite material demonstrates clearly defined two-way shape memory behavior without any additional thermomechanical treatments and can be used to create micromechanical devices with a higher level of functional properties.

Thin films of tungsten selenides (WSex) were obtained by using a method of shadow-masked pulsed laser deposition. The deposition at room temperature of substrates caused the formation of Se-enriched amorphous films (Se/W∼5) with pronounced surface roughness because of an effective nanoparticle growth. Heating or DC biasing the substrate during the deposition modified the film composition (Se/W∼1.7 – 4) and resulted in the smoothing of the film surface. Annealing the films, deposited at room temperature, as well as heating the substrate during the deposition caused crystallization of the films. Catalytic activity of WSex thin films in hydrogen evolution reaction (HER) was studied in 0.5M H2SO4 aqueous solution at room temperature. The structural state and the chemical composition of WSex films had an expressed impact on the catalytic activity. A significant improvement in HER activity was observed in the case of Se-enriched films deposition followed by annealing at 500°C.

The work deals with the research of the effect of pulsed laser radiation (λ=248nm) on the structure and the manifestation of the shape memory effects (SMEs) in the Ti50Ni25Cu25 alloy, produced by melt spinning technique. It has been revealed that the proposed method of laser treatment leads to the formation of structural amorphous-crystalline composite demonstrating the pronounced two-way SME. A dependence of the two-way SME on the number of laser radiation pulses was determined.

Thin-film precursors of BC x were formed by pulsed laser codeposition of boron and carbon. Targets made of pressed boron and carbon powders with an equal element content (B/C = 1/1) and an increased carbon content (B/C = 1/3) were used. The films were deposited on sapphire substrates at elevated temperature (700°C) which determined the initial properties of the precursor BC x films. Irradiation of the films was carried out by laser pulses of nanosecond duration with varying intensity. The films obtained by laser annealing of BC x (Q-BC x ) were studied by scanning electron microscopy and micro-Raman spectroscopy. Irradiation under optimal conditions made allowed to realize pulsed melting of the films and partial preservation of their continuity on the substrate. The local structure of Q-BC x films and the nature of the changes in their electrophysical properties depended on the composition of the precursor films and the laser irradiation regimes.

A comparative analysis of the abilities of several novel methods to produce ultrathin molybdenum disulphide (MoS2) films containing from 1 to 10 molecular layers was carried out. To deposit MoSxfilms and MoOxprecursor films, the atomic flux was formed by laser ablation of Mo, MoS2, and MoO3targets. Saturation with sulphur of the deposited layers was performed using a reactive gas (hydrogen sulphide) or by thermally activated treatment of thin-film precursors in a sulphur vapor. It has been established that the use of hydrogen sulphide makes it possible to obtain ultrathin MoS2films at relatively low temperatures ∼ 350 °C. However, these films contained local defects which were absent in the films prepared by the treatment of thin film MoOxprecursors in sulphur vapours at higher temperatures (≥ 650°C).

The films of tungsten oxides were prepared by pulsed laser ablation of W target in a reactive gas atmosphere (air of laboratory humidity). Optical analysis and ion signal measurements for the laser plume allowed to recognise a threshold gas pressure that suppresses the deposition of non-scattered atomic flux from the plume. When the pressure exceeds about 40 Pa, the films grow due to the deposition of species that could be formed in collisions of W atoms with reactive molecules (e.g., O2). Kinetic Monte Carlo method was used for modelling film growth. Comparison of the model structures with the experimentally prepared films has shown that the growth mechanism of ballistic deposition at a pressure of 40 Pa could be changed on the diffusion limited aggregation at a pressure of ~100 Pa. Thus, a cauliflower structure of the film transformed to a web-like structure. For good correlation of experimental and model structures of WO x , a dimension of structural elements in the model should coincide with W-O cluster size.

Nanocomposite a-C(Mo/MoSe x ) thin films containing amorphous carbon matrix a-C, nano-Mo and MoSe x ≥2 clusters were obtained by pulsed laser co-deposition of carbon and MoSe2. The deposition was carried out at room temperature onto a graphite substrate. Atomic content of the MoSe x≥2 phase did not exceed 25%. The use of a buffer gas at a pressure of 10 Pa allowed to obtain the maximum Se/Mo ratio in the films and to increase the concentration of sp2-hybridized C atoms for high conductivity realization. The formation of MoSe x≥2 cluster inclusions was the essential factor for activation of hydrogen evolution reaction (HER) in 0.5 M H2SO4 aqueous solution. These clusters also promoted cathodic deposition of Pt nanoparticles on the surface of a-C(Mo/MoSe x ) in a H2SO4/KCl solution when a Pt anode was used as a source of Pt. Hybrid Pt/a-C(Mo/MoSe x ) thin-film coatings with a low Pt loading (~6 μg/cm2) exhibit excellent HER property, which noticeably exceeds that of relatively thick Pt coating prepared on a graphite substrate by pulsed laser deposition.

Nanostructured WO x

Thin-film structures based on gas-sensitive tungsten oxide and catalytic platinum are fabricated by room-temperature deposition on a silicon carbide wafer using pulsed laser and ion-plasma methods. Oxide layer annealing in air to 600°C caused the formation of microstructured and nanostructured crystalline states depending on the deposition conditions. Structural differences affect the electrical parameters and the stability of characteristics. The maximum response to hydrogen is detected in the structure fabricated by depositing a low-energy laser-induced flow of tungsten atoms in oxygen. The voltage shift of the currentvoltage curves for 2% H2 in air at 350°C was 4.6 V at a current of ∼10 μA. The grown structures’ metastability caused a significant decrease in the shift after long-term cyclic testing. The most stable shifts of ∼2 V at positive bias on the Pt contact were detected for oxide films deposited by ion-plasma sputtering.

We synthesized star-shaped pentagonal microcrystals of boron carbide with an extremely low carbon content (~5%), from m-carborane under high pressure (7 GPa) and high temperature (1370&ndash, 1670 K). These crystals have five-fold symmetry and grow in the shape of stars. A 5-fold symmetry in large micron-sized crystals is extremely rare making this a striking observation.

The potential of pulsed laser deposition in an applied uniform electrostatic field was investigated. A flat, positively charged, fine-celled-grid counter electrode was used to provide bias voltage of up to +50 kV with respect to the substrate. This enabled control of the atomic mixing and made it possible to initiate chemical bond formation at the interfaces of the films formed by deposition from the laser-induced plume. As an example, the results of multilayer 56Fe/MoSx/57Fe film deposition are presented. At first, a bilayer MoSx/57Fe film was grown in the absence of the electric field. This was followed by 56Fe film deposition in an applied field. A relatively sharp interface between the MoSx and 57Fe films was observed. In contrast, after 56Fe deposition, effective atom mixing was observed and new chemical bonds between Fe, S and Mo were detected. By penetrating through the interface, accelerated 56Fe ions gave rise to the growth of an amorphous layer of up to 50 nm in thickness. It consisted of rather evenly distributed Fe, S and Mo atoms (at total ion dose of 2.5×1016 cm−2). The ion flux destroyed MoS chemical bonds, and the S atoms released preferably bound Fe atoms, thus forming a FeS2-type phase. The Mo atoms, as a lower-oxidation-state species (apparently together with S atoms), were localized in the vicinity of Fe atoms and affected the hyperfine magnetic fields. The technique developed has made it possible to study the ion-induced processes occurring at the interfaces of multilayer films. It can also be applied to improve the tribological functionality of thin films.

Irradiation of MoSe2 target with intensive laser pulses caused the formation of micro- and nanoparticles. The particles were observed on the target surface and in MoSex films prepared by deposition of the laser-induced plume. Content of nanoparticles on the film surface was markedly larger than that of microparticles. Transport of the plume in vacuum and in a buffer helium (He) gas was studied. The He pressure was high enough to provide effective atom scattering and plume deceleration. For a medium target-substrate distance, the structure of MoSex film was formed due to intensive deposition of atomic flux scattered in the buffer gas. Impact of nanoparticles on the structure was negligible. For a large distance, deposition of the nanoparticles from the plume was assisted by co-deposition of drifting atomic flux. Such deposition resulted in the formation of relatively smooth film containing nanoparticles transferred with plume, as well as the growth of spherical Se particles on the substrate.

Amorphous WOx films were prepared on the SiC crystal by using two different methods, namely, reactive pulsed laser deposition (RPLD) and reactive deposition by ion sputtering (RDIS). After deposition, the WOx films were annealed in an air. The RISD film possessed a m-WO3 structure and consisted of closely packed microcrystals. Localized swelling of the films and micro-hills growth did not destroy dense crystal packing. RPLD film had layered β-WO3 structure with relatively smooth surface. Smoothness of the films were destroyed by localized swelling and the micro-openings formation was observed. Comparative study of m-WO3/SiC, Pt/m-WO3/SiC, and P-WO3/SiC samples shows that structural characteristics of the WO3 films strongly influence on the voltage/current response as well as on the rate of current growth during H2 detection at elevated temperatures.

Novel nanostructured thin-film coatings containing WSe2 and WO3 nanosheets were prepared through a simple and highly reproducible method. Pulsed laser pre-deposition of W- Se-O films on a microcrystalline graphite substrate by ablation of WSe2 target in a mixture of Ar and O2 gases was followed by thermal post-treatment. The influence of pre-deposition and post-treatment conditions on the structure, morphology and chemical composition of the W-Se- O films was studied. Thermal annealing at appropriate conditions of pre-deposited amorphous W-Se-O films resulted in the formation of crystalline structure consisted of nanocrystals of WSe2 and WO3 phases. Such structural modification significantly altered the electrochemical properties of the thin-film coatings with consequences, in particular, on their catalytic activity toward hydrogen evolution reaction in an acid solution.

MoSe x coatings were obtained by pulsed laser deposition in vacuum and inert Ar gas atmosphere at the pressure from 1 to 10 Pa. The deposition temperature was 200°C. The films were studied by means of X-ray diffraction, scanning and transmission electron spectroscopy, X-ray photoelectron spectroscopy, Rutherford backscattering spectroscopy of helium ions. The tribological properties of thin film coatings were investigated by pin-on-disk testing in air with 50% relative humidity. Chemical composition, structure, and tribological properties of the coatings were found to be sensitive to the presence of the inert gas. Thus, increasing the gas pressure from 1 to 10 Pa changes the chemical composition, so that the value of x increases from 1.5 to 2.4 in the principal deposition zone. At the optimal gas pressure (~ 2 Pa), the composition of the coating was close to the stoichiometric one, and the layer adjacent to the substrate consisted of MoSe x nano-crystals with the basal planes parallel to the substrate surface or oriented at small angles to the surface. The tribological properties of MoSex coatings deposited on steel substrates depend on the gas pressure. The friction coefficient in air decreases from 0.08 for deposition in vacuum to 0.04 for deposition at the optimal pressure.