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Although MXenes have been synthesized by liquid phase and molten salt etching approaches, it still suffers from sluggish reaction kinetics of removing A species from MAX phases associated with an overlong production time (5–48 h). Here, a minute‐level production approach is developed to produce MXenes (Ti2CClx) by selectively etching MAX phases (Ti2AlC) under metal chloride (ZnCl2) vapor. In this synthetic protocol, metal chloride vapor possesses a very high chemical activity to the interlaminar A metal layers of MAX phases owing to negative Gibbs free energies, accompanied with the fast removal of gaseous A‐containing chlorides in the reaction system. Moreover, some M species can be controllably etched off from the lattice of MX slabs to generate metal vacancies, which have a high reducing ability to implant single‐atom Zn from ZnCl2 vapor. Finally, vacancy‐enriched MXenes are produced after the volatilization of Zn. In this manner, the etching time is less than one‐sixtieth those of liquid phase and molten salt etching approaches. The resultant MXenes can be employed as an efficient platform for implanting single‐atom Pt, showing a low overpotential of 41 mV at a current density of 10 mA cm−2 and a good long‐term stability up to 5000 cycles. [ABSTRACT FROM AUTHOR]

Thermal laser epitaxy (TLE) is a novel film growth technique capable of fabricating ultrapure films of many material systems. For growing oxide films with TLE, the impact of source oxidation on the evaporation rate is a central issue, which, however, has not yet been explored systematically. Here, we report a systematic, experimental study of the role of source oxidation on source evaporation at various oxygen pressures and source temperatures in TLE. The volatility of the oxidized metal sources affects the source evaporation rate. When the oxidized metal source is more volatile than the metal, the source evaporation rate increases with the oxygen supply. In a strongly oxidizing environment, stable oxides with lower volatility tend to form and decrease the evaporation rate of the source. Increasing the laser power—and thereby the source temperature—tends to prevent the formation of stable oxides. At even higher source temperatures, the metal vapor pressure can dominate the oxide vapor pressure even in a high oxygen pressure atmosphere. A power-law relation between deposition rate and oxidizing gas pressure is found in case the formation and evaporation of volatile oxides of the elemental source material dominates the total evaporation process. The exponent of this law is a measure of the relevance of source oxidation for the evaporation of the source. [ABSTRACT FROM AUTHOR]

[Display omitted] Single-atom photocatalysts can modulate the utilization of photons and facilitate the migration of photogenerated carriers. However, the preparation of single-atom uniformly doped photocatalysts is still a challenging topic. Herein, we propose the preparation of Ni single-atom doped g-C 3 N 4 photocatalysts by metal vapor exfoliation. The Ni vapor produced by calcining nickel foam at high temperature accumulates in between g-C 3 N 4 layers and poses a certain vapor pressure to destroy the interlayer van der Waals forces of g-C 3 N 4. Individual metal atoms are doped into the structure while exfoliating g-C 3 N 4 into nanosheets by metal vapor. Upon optimization of Ni content, the Ni single atom doped g-C 3 N 4 nanosheets with 2.81 wt% Ni exhibits the highest CO 2 reduction performance in the absence of sacrificial agents. The generation rates of CO and CH 4 are 19.85 and 1.73 μmol g−1h−1, respectively. The improved photocatalytic performance is attributed to the anchoring Ni of single atoms on g-C 3 N 4 nanosheets, which increases both carrier separation efficiency and reaction sites. This work provides insight into the design of photocatalysts with highly dispersed single-atom. [ABSTRACT FROM AUTHOR]

Shielding gas, metal vapors, and gases trapped inside powders during atomization can result in gas porosity, which is known to degrade the fatigue strength and tensile properties of components made by laser powder bed fusion additive manufacturing. Post-processing and trial-and-error adjustment of processing conditions to reduce porosity are time-consuming and expensive. Here, we combined mechanistic modeling and experimental data analysis and proposed an easy-to-use, verifiable, dimensionless gas porosity index to mitigate pore formation. The results from the mechanistic model were rigorously tested against independent experimental data. It was found that the index can accurately predict the occurrence of porosity for commonly used alloys, including stainless steel 316, Ti-6Al-4V, Inconel 718, and AlSi10Mg, with an accuracy of 92%. In addition, experimental data showed that the amount of pores increased at a higher value of the index. Among the four alloys, AlSi10Mg was found to be the most susceptible to gas porosity, for which the value of the gas porosity index can be 5 to 10 times higher than those for the other alloys. Based on the results, a gas porosity map was constructed that can be used in practice for selecting appropriate sets of process variables to mitigate gas porosity without the need for empirical testing. [ABSTRACT FROM AUTHOR]

The HelixJet atmospheric plasma‐assisted synthesis can be a new toolbox to realize dedicated nanoparticle architectures such as Janus‐type morphologies. Silicon nanoparticles produced by the decomposition of Silane molecules are directed into an in‐flight annealing stage. The applied high‐temperature supplies a metal vapor rich atmosphere containing Manganese, Chromium, Iron, and Tin outgassing from the used steel tube. The metal atoms alloy into the Silicon nanoparticles and form a self‐assembled 'Si/MnxSiy‐alloy' Janus nanosphere architecture. The Janus particles nanochemistry is thoroughly examined in detail by the analytic capabilities of transmission electron microscopy. The combined approach of electron diffraction, EDS, and EELS identifies the Janus particle composition consisting of a pure Si hemisphere interfaced to an alloyed Mn4Si7 hemisphere covered by a thin (MnaFebCrc)Siy surface shell. [ABSTRACT FROM AUTHOR]

In this work, the binding energy of three alkali metal molecules, namely, lithium-7 (7Li2), sodium-23 (23Na2), and potassium-39 (39K2), is calculated in both free space and the vapor phase. In free space, the Lippmann–Schwinger equation is solved for negative-definite eigenenergies using a highly effective matrix-inversion method with a symmetrized kernel. In the vapor, two medium effects are taken into account: the effective atomic mass, which is somewhat larger than the "bare" mass and therefore enhances the binding; and the effective binary interaction, with less overall attraction than the "bare" interaction. In free space, the binding energies of the respective molecules are, in units of (103 K), 5.304, 2.936, and 2.522. The corresponding experimental results are 6.150 × 103, 4.275 ×103, and 4.275 × 103 K. The results in the vapor phase are by and large somewhat lower than those in free space. [ABSTRACT FROM AUTHOR]

This note presents a vapor-based seeding apparatus, named the external alkali seeding instrument (EASI), which is designed to introduce alkali metal vapors into experimental facilities without using precursors or large auxiliary equipment. The device vaporizes small amounts of alkali metals, potassium in this work, which are then carried away by an inert gas. In a benchtop flow cell, carrier gas flow rate (6– 200 cm 3 / s ) and device temperature (150– 250 ∘ C ) most strongly affected potassium-vapor concentrations. Higher values of either quantity lead to increased potassium-vapor concentrations. When using the EASI to seed a shock tube experiment, vapor-phase potassium was detected immediately after the incident and reflected shockwaves using a laser absorption diagnostic. Mole fraction time histories stay within a factor of 2 over the test time as compared with those from a precursor-based seeding approach, which may span multiple orders of magnitude. This suggests potassium is nearly homogeneously distributed throughout the test gas. This design can be extended to other low-vapor-pressure elements, such as other alkalis or sulfur, with minimal modifications. The EASI simplifies seeding for laboratory experiments targeting potassium and other alkali metals—enabling advances in fundamental spectroscopy, diagnostic development, and chemical kinetics. [ABSTRACT FROM AUTHOR]

A hydrocarbon‐soluble barium anthracene complex was prepared by means of metal vapour synthesis. Reaction of 9,10‐bis(trimethylsilyl)anthracene (Anth′′) with barium vapour gave deep purple Ba(Anth′′) which after extraction with diethyl ether crystallised as the cyclic octamer [Ba(Anth′′)⋅Et2O]8. Dissolution in benzene or toluene led to replacement of the Et2O ligand with a softer arene ligand and isolation of Ba(Anth′′)⋅arene. Diffusion ordered spectroscopy (DOSY NMR) measurements in benzene‐d6 indicate solution species with a molecular weight that equals a trimeric constitution. Natural population analysis (NPA) assigned charges of +1.70 and −1.70 to Ba and Anth′′, respectively, relating to highly ionic Ba2+/Anth′′2− bonding. Preliminary reactivity studies with air, Ph2C=NPh, or H2 show that the complex reacts as a Ba0 synthon by release of neutral Anth′′. This soluble molecular Ba0/BaII redox synthon provides new routes for the syntheses of barium complexes under mild conditions. [ABSTRACT FROM AUTHOR]

A hydrocarbon‐soluble barium anthracene complex was prepared by means of metal vapour synthesis. Reaction of 9,10‐bis(trimethylsilyl)anthracene (Anth′′) with barium vapour gave deep purple Ba(Anth′′) which after extraction with diethyl ether crystallised as the cyclic octamer [Ba(Anth′′)⋅Et2O]8. Dissolution in benzene or toluene led to replacement of the Et2O ligand with a softer arene ligand and isolation of Ba(Anth′′)⋅arene. Diffusion ordered spectroscopy (DOSY NMR) measurements in benzene‐d6 indicate solution species with a molecular weight that equals a trimeric constitution. Natural population analysis (NPA) assigned charges of +1.70 and −1.70 to Ba and Anth′′, respectively, relating to highly ionic Ba2+/Anth′′2− bonding. Preliminary reactivity studies with air, Ph2C=NPh, or H2 show that the complex reacts as a Ba0 synthon by release of neutral Anth′′. This soluble molecular Ba0/BaII redox synthon provides new routes for the syntheses of barium complexes under mild conditions. [ABSTRACT FROM AUTHOR]

Gold nanoparticles were prepared by metal vapor synthesis using isopropyl alcohol, acetone, and toluene as dispersion media. The electronic states of the metal and the nature of the adsorbed layer on the nanoparticle surface were investigated. Analysis of the photoelectron spectra of the obtained nanoparticles showed that regardless of the synthesis conditions, gold occurs in the Au0, Au+, and Au3+ states in all samples, and a carbon-containing shell is present on all types of metal particles. A study of the anticancer activity of nanoparticles in vitro using human cell lines revealed a dependence of the biological activity on the exposure time for samples obtained in a toluene dispersion medium. The metabolic activity of cancer cells treated with gold nanoparticles formed in isopropyl alcohol or acetone dropped in the very beginning of testing. [ABSTRACT FROM AUTHOR]

For the first time, an innovative scheme of high-power high-voltage pulsed laser excitation featuring bipolar electric power supply units was applied to energize CuBr vapor lasers. This innovative excitation scheme (capable to deliver up to 8.1 kW of average electric power) resulted in 151 W of average laser output from a single large-volume 10 liter CuBr laser. This is a record-high average output power for CuBr lasers on atomic self-terminating lines λ510.6 nm and λ578.2 nm so far. For the first time, we made and demonstrated the reliable work of a robust compact all-solid-state bipolar pulsed power supply of 1.8 kW average electric power with two symmetrical arms of 0.9 kW each. [ABSTRACT FROM AUTHOR]

The paper presents the development and investigation of a semiconductor power supply for metal atoms' active media excitation with a pulse repetition rate of up to 200 kHz in pulse-periodic mode. High voltage excitation pulses are formed by a source based on the LTD-generator concept (linear transformer driver) with a single-turn step-up transformer. The calculation and justification for the selection of power supply elements, based on typical excitation modes of the active medium in copper bromide vapor, are presented. The mean radiation power was equal to 650 mW under excitation condition: PRF was to 150 kHz and specific pulse energy input was 160 µJ/cm3. [ABSTRACT FROM AUTHOR]

The vacuum arc discharge makes transition to a footpoint mode, anode spot type 1 (type 1) mode and anode spot type 2 (type 2) mode under high current conditions. The mode dependence of the electron and metal vapor densities were experimentally quantified using dichroic Shack–Hartmann type laser wavefront sensors. In the type 1 mode, the electron and metal vapor densities were about 2.5 times higher than the footpoint mode. The electron density of the type 2 mode was three times higher than that of the type 1 mode, while significant difference was not found in the metal vapor density. Such higher electron density for the type 2 mode than the type 1 mode was coherent with a previous result obtained by Stark broadening. The present electron and metal vapor density measurement demonstrated that the amount of the electrode erosion was in the following order: footpoint mode < type 1 mode < type 2 mode, which agreed with a previous study. [ABSTRACT FROM AUTHOR]

The cathode sheath (CS) formation of the direct current air circuit breaker is simulated by a fluid model, and the influence of metal vapor concentration between the contacts after liquid metal bridge rupture is considered. The CS conductivity increases with the increasing concentration of copper vapor. The copper vapor concentration increases from 5% to 95%, and the thickness of the positive space charge layer and ionization layer increases from 22.3 and 49.1 μ m to 51.8 and 81.7 μ m , respectively. Increasing the CS conductivity is beneficial for the motion of arc roots in a certain range. [ABSTRACT FROM AUTHOR]

A three-dimensional model based on molecular dynamics has been developed to describe the formation of a single cathode spot in vacuum arcs. The formation of the cathode spot is assumed to be controlled by the plasma ions, the effect of which is simulated in LAMMPS through the process of ion bombardment. The cathode is represented by structured copper atoms, while the ions are continuously injected into the domain with a certain velocity towards the cathode surface. Ion bombardment leads to the appearance of a crater, which is caused by the accumulation of pressure effect against the relaxation of substrate temperature. The size of the crater is found to be determined by the spatial distribution of the injected ions. The formation of the cathode spot is also scrutinised by electron emission from the cathode surface with variable surface temperature during the cathode spot development process. In addition, the evaporated atoms forming the metal vapour are observed. This study provides a description of the formation of the cathode spot at microscale, which shall be helpful to further studies of the arc rooting and arc contact (electrode) erosion in vacuum environment. [ABSTRACT FROM AUTHOR]

Matching the pumping generator (power supply) with the load (laser tube) is the determining criterion for efficient pumping of metal vapor lasers (MVLs). The challenge of achieving the energy potential of the MVL emerges when thyratrons are used as switches, which have a limited stable zone of operation with a maximum limit for most thyratrons ~ 6 kV. Matching the pumping generator with the load under these conditions is carried out providing an aperiodic discharge process of the peaking capacitor C0. Therefore, the pumping processes in the active medium significantly depend on the electrode locations in the gas discharge tube (GDT). In this work is shown, in the structure of GDT, where electrodes are located in the active medium (hot zone of the discharge channel), the pumping is occurred in the discharge process of the storage capacitor C, where C0 is a matching element. While the pumping is executed in the discharge process of C0 and the capacitance component of the GDT (CGDT) in GDT with electrodes located out of active medium where buffer gas (cold buffer zones). In this structure of GDT, the efficient pumping is realized using controlled switch, which prevents energy input going into GDT from C after charging C0 and the CGDT. [ABSTRACT FROM AUTHOR]

The absorption of a light wave interacting with optical transitions in the D1 line of an alkali metal atom subjected to microwave radiation that is in resonance with magnetic dipole transitions between hyperfine ground-state components, has been investigated. It is known that when scanning a longitudinal magnetic field (B || k, where k is the wavevector), one may observe a magneto-optical resonance due to the ground-state Hanle effect. In addition, the effect of double radio-optical resonance takes place because of the presence of the resonance microwave field. The joint influence of these effects on the formation of a narrow magneto-optical resonance in light wave absorption has been studied theoretically and experimentally. It has been shown analytically that the effects compete with each other and destructively act on the resonance formation. As a result, the amplitude of the resonance is small and its shape is complicated. However, in the presence of a buffer gas the pressure of which is such that the hyperfine splitting of the ground state remains spectrally unresolved, it becomes possible to observe a magneto-optical resonance with a relatively large amplitude. Experiments have been carried out with the use of a miniature glass cell (V ~ 0.1 cm3) filled with 87Rb vapor and a buffer gas argon (a pressure of about 95 Torr). In particular, the theoretically predicted resonance narrowing with increasing light field intensity has been experimentally observed. A configuration for magneto-optical resonance excitation suggested here may be applied in quantum magnetometry to measure weak permanent magnetic fields and resonance microwave fields using cells filled with alkali metal vapor. [ABSTRACT FROM AUTHOR]

The paper is devoted to development of atypical excitation approaches of bistatic laser monitor active elements for the imaging of high-speed processes at a powerful background radiation. The practical significance is increasing the temporal resolution of the bistatic laser monitor, as well as improving the imaging parameters by minimizing the jitter of radiation pulses. To achieve this goal, semiconductor excitation sources of active media based on copper bromide vapor were developed, and their synchronization was performed in a pulse-repetition mode. The developed pump sources are set of identical commutation cells. Each cell contains storage capacitor, commutator and transformer. Powerful HGTG27N120BN insulated-gate bipolar transistors (IGBT) were chosen as commutators. Their switching storage capacitors are discharged through the primary winding of the transformer and as result the voltage pulse is induced in the secondary winding. The transformer load was the gas discharge tube (GDT) of the small-size brightness amplifier with the specified geometric parameters (l = 40 cm, d = 2.5 cm, V = 196 cm3). The simultaneous switching of 10 identical cells provided GDT breakdown. The radiation power of the active element in oscillator mode was 665 mW. The developed brightness amplifier with semiconductor pump source was used in the bistatic scheme of the laser monitor for the imaging of the test object. The pumping of the second active element, the illumination source (l = 90 cm, d = 5 cm, V = 1767 cm3), was performed by means of thyratron TGI1-1000-25. The pulse repetition frequency of the illumination source and the brightness amplifier was 10.5 and 21 kHz respectively. As result each second image was formed with increased brightness and contrast. The maximal jitter of radiation pulses in this case was 16 ns. The average jitter was 6 ns. Two identical semiconductor pump sources were tested simultaneously. The resulting array of waveforms (GDT current and GDT voltage) show that in most cases the jitter was completely absent, and when it appeared, it did not exceed 4 ns. The imaging at this configuration of the pump sources was not performed due to semiconductor source power (465 W) turned out to be insufficient for the excitation of the illumination source, and therefore options for increasing it were proposed. [ABSTRACT FROM AUTHOR]

Supersonic jets of metal vapors with carrier gas are promising for producing nanostructured metal films at relatively low source temperatures and high deposition rates. However, the effects of the carrier gas on the jet composition and expansion dynamics, as well as on film properties, remain virtually unexplored. In this work, the free-jet expansion of a mixture of silver vapor with helium in a rarefied regime at an initial temperature of 1373 K is investigated through mass spectrometry and direct-simulation Monte Carlo methods. Introducing the carrier gas into the source is found to result in a transition from a collisionless to a collision-dominated expansion regime and dramatic changes in the Ag jet, which becomes denser, faster, and more forward-directed. The changes are shown to be favorable for the formation of small Ag clusters and film deposition. At a fairly high helium flow, silver Ag2 dimers are observed in the jet, both in the experiment and the simulations, with a mole fraction reaching 0.1%. The terminal velocities of silver atoms and dimers are nearly identical, indicating that the clusters are likely formed due to the condensation of silver vapor in the expanding jet. A high potential of supersonic Ag-He jets for the deposition of nanostructured silver films is demonstrated. The deposited jet Ag2 dimers appear to serve as nucleation centers and, thus, allow for controlling the size of the produced surface nanostructures. [ABSTRACT FROM AUTHOR]

Metal vapor vacuum arcs (VAs) are widely used in various fields of industry, such as circuit breakers, ion sources, electrical thrusters, and deposition systems. VAs usually originate from metal vapors eroding from the surface of a cathode, where they burn as tiny bright points, hence their name "cathode spots" (CS). Due to their high plasma density, short life span, and micrometer scale, the in situ and non-intrusive diagnostics of CS are a challenge. Numerical simulation is one method used to study CS with the aid of high-performance computing. The well-established particle-in-cell method provides solutions for the spatial-temporal electromagnetic field and the microscopic distribution functions of plasma species in phase space from which the macroscopic parameters of the plasma can be calculated. This Perspective reviews the progress in particle modeling of VAs with an emphasis on the non-stationary and non-local physical processes that are not reproduced by fluid models. Furthermore, a personal outlook on future challenges is provided: the physical modeling of plasma–electrode interactions, the collection and evaluation of collision cross sections, the trade-off between heavy computation cost and predictive ability, and the verification and validation of the simulation code. [ABSTRACT FROM AUTHOR]

This study aimed to clarify the effect of wire structure and alkaline elements in wire composition on metal transfer behavior in metal-cored arc welding (MCAW). A comparison of metal transfer in pure argon gas was carried out using a solid wire (wire 1), a metal-cored wire without an alkaline element (wire 2), and another metal-cored wire with 0.084 mass% of sodium (wire 3). The experiments were conducted under 280 and 320 A welding currents, observed by high-speed imaging techniques equipped with laser assistance and bandpass filters. At 280 A, wire 1 showed a streaming transfer mode, while the others showed a projected one. When the current was 320 A, the metal transfer of wire 2 changed to streaming, while wire 3 remained projected. As sodium has a lower ionization energy than iron, the mixing of sodium vapor into the iron plasma increases its electrical conductivity, raising the proportion of current flowing through metal vapor plasma. As a result, the current flows to the upper region of the molten metal on the wire tip, with the resulting electromagnetic force causing droplet detachment. Consequently, the metal transfer mode in wire 3 remained projected. Furthermore, weld bead formation is the best for wire 3. [ABSTRACT FROM AUTHOR]

Nonlinear resonances in alkali metal vapor, which are detected by the magneto-optical rotation of the linear polarization of light, are actively used in quantum magnetometry to fabricate atomic magnetometers. The magneto-optical rotation in most such sensors is due to magnetic birefringence, and rotation angles usually do not exceed tens of milliradians. In this work, an experiment where magneto-optical resonances of linear polarization rotation of a probe wave are due to strong dichroism induced in a medium by a counterpropagating pump wave has been proposed. Both waves are in resonance with the Fg = 2 → Fe = 1 optical transition in the 87Rb D1 line (λ ≈ 795 nm). Experiments have been carried out with a 2-cm-long cylindrical cell filled with a buffer gas, and the maximum rotation angle is ≈390 mrad (22°) at a width of resonance of about 300 nT. The results show that the configuration proposed for the observation of magneto-optical rotation is promising for the fabrication of compact high-sensitivity atomic magnetometers. [ABSTRACT FROM AUTHOR]

The temperature-dependent composition and phase formation during the physical vapor deposition (PVD) of Mg-Ca thin films is modeled using a CALPHAD-based approach. Considering the Mg and Ca sublimation fluxes calculated based on the vapor pressure obtained by employing thermochemical equilibrium calculations, the experimentally observed synthesis-temperature trends in the thin-film composition and phase formation were reproduced. The model is a significant step towards understanding how synthesis parameters control composition and, therefore, phase formation in the PVD of metals with high vapor pressures. [ABSTRACT FROM AUTHOR]

Herein, we report the design and scalable synthesis of three new Co(III) complexes, which have an unusual hydrocarbon η¹ -alkyl-η³ -allyl-η5 -cyclopentadienyl ligation structure, from the reactions of readily available cobalt(II) compound CoCl2 (PPh3)2 and biomass material β-pinene via C-C bond activation. These Co(III) complexes are air-stable, fairly volatile, and thermally stable, so they are excellent candidates as the metal precursors for the vapor deposition of cobalt-containing thin films. As a demonstration, we show that the Co(III) complex of [(3'-5'-η,1-σ)-methylene(2,2,4-trimethyl-4-cyclohexene-1,3-diyl)](η5 -methylcyclopentadienyl)Co (i. e. (seco-pinene)(MeCp)Co) is well suited for the atomic layer deposition (ALD) of Co3 O4 and CoS2 thin films, and the deposited Co3 O4 and CoS2 films are able to conformally cover trench structures with a fairly high aspect ratio of 10: 1. [ABSTRACT FROM AUTHOR]

The presence of metal vapor influences arc stability in both arc and hybrid welding. It is assumed that the composition of the metal vapor, and therefore the substrate material composition, plays an important role due to the different ionization energies of the material elements. In this study, a special setup is used to investigate the influence of metal vapor on the behavior of a vertically oriented arc generated between two equal electrodes by a separate laser-induced vapor generation using a transversally oriented laser beam welding process with additional support materials beside the process zone of the arc. Several aluminum alloys, steel materials, and titanium alloys are used as vapor-producing support materials. The experiments show that the arc voltage increased under the presence of metal vapor, which implies a decrease in arc stability, leading partially to an extinction of the arc. The influence of the ionization energy is evaluated by calculating the average ionization energy for each material composition. In the case of inducing metal vapor into the arc zone, a smaller ionization energy and a lower amount of alloying elements of the support material result in a lower arc voltage increase and, therefore, higher arc stability. A higher effect on the arc stability when using elements with a smaller ionization energy for the second electron than the first argon electron is not measurable. [ABSTRACT FROM AUTHOR]

In this paper, AlN thin films are fabricated by green and efficient metal nitride vapor phase epitaxy (MNVPE). First, AlN films are grown on c‐plane sapphire substrates at different molar flow ratios (V/III ratios) of the source material, and the effects of V/III on the crystal quality and surface morphology of the films are investigated. The growth conditions are kept constant (growth temperature of 1550 °C, growth pressure of 10 kPa, V/III ratio of 4420), and the AlN thin films are prepared by heterogeneous epitaxial growth on c‐plane sapphire, silicon (111), and GaN substrates. The crystal quality, residual stress, and luminescence properties of epitaxial AlN thin films on the three substrates are investigated using X‐ray diffraction, scanning electron microscopy, Raman spectroscopy, photoluminescence, and UV spectrophotometer. Among them, the FWHM value of the sample AlN/GaN (002) plane can reach 338 arcsec. The residual stress in samples AlN/Sapphire, AlN/GaN and AlN/Si are 1027, −81, and −541 MPa, respectively, and the sample AlN/GaN has fewer point defects. At the same time, a 50‐nanometer‐thick void layer appears in the AlN thin film samples prepared on GaN substrates, which provides a new technical idea for realizing large‐scale and high‐quality self‐supporting AlN thin films. [ABSTRACT FROM AUTHOR]

A high-energy metal vapor vacuum arc (MEVVA) ion source was used to implant aluminum (Al) ions into the WE43 alloy (Al-WE43) at a dose of 1 × 1016 ions·cm−2, and the structural composition, mechanical properties, corrosion resistance, and biocompatibility of the alloy before and after implantation were systematically studied. The results showed that an Al 2 O 3 /Al thin film was formed on the surface of the WE43 alloy after Al ion implantation, and the dense film caused the corrosion current density (I corr) of the alloy to decrease from 140.2 ± 9.3 to 17.9 ± 6.1 μA⋅cm−2. Nanoindentation experiments revealed that the elastic model (EIT) and nano-hardness (HIT) of the Al-WE43 alloy were significantly improved due to the surface lattice distortion caused by Al ion implantation. A diluted extract of the Al-WE43 alloy showed higher cell activity, anti-hemolysis and anti-coagulation properties than that of the WE43 alloy. In general, the Al-WE43 alloy can be considered as a promising biodegradable metallic material for cardiovascular stent applications. [ABSTRACT FROM AUTHOR]

Compared with strongly acidic molecular sieve catalysts, metal oxide catalysts are less prone to deactivation by coking due to their mild acid-base properties. Several metal oxides (Al2O3, MgO, CaO, CuO, Fe2O3, NiO, ZnO, ZrO2, TiO2 and CeO2) were selected for mild catalytic pyrolysis of lignin and compared with molecular sieve catalysts (MCM-41, HZSM-5, ZSM-5). Among the metal oxide catalysts studied, CuO, Fe2O3 and TiO2 inhibited the formation of acids/alcohols (1–2%) and promoted the production of hydrocarbons (15.31%, 20.17% and 28.83%, respectively). Especially when TiO2 catalyst was added, the proportion of hydrocarbons reached the highest (28.83%), but it inhibited the production of phenols (3.3%). The presence of CuO promoted the production of phenols (9.70%), showing a good deoxidation performance. Compared with the oxide catalysts, the addition of molecular sieve catalysts only resulted in 2 ~ 3% phenols. Compared with strongly acidic molecular sieve catalysts, metal oxide catalysts showed certain catalytic activity in deoxidation and cracking, and showed some advantages in the formation of phenols. [ABSTRACT FROM AUTHOR]

A novel approach to stabilize the laser's discharge plasma impedance by trigger modulation is presented. The discharge plasma impedance of laser drops due to increased charge carriers during laser operation. The absence of intermittent high voltage discharge pulses provides enhanced time for recombining charge carriers, thus restricting the fall in the laser impedance. It has been observed that by missing 0.1% of discharge pulse, the drop in the laser voltage is improved from 4.3 to 2.3%, and an increase in the laser head current is limited to 3% from 3.6% in 6 h of laser operation. The drop in the optical output power is reduced by 10% at the end of 6 h. Further, the controlled intermittent discharge missing ceases the thermal loading at the cathode fall and lowers the probability of thermal instability in discharge plasma. This will improve the discharge stability and reduces the jitter in the metal vapor laser. We believe this approach of manipulating trigger to attain stable impedance and prevent instability, can be applied to other applications requiring high current large volume stable discharges. [ABSTRACT FROM AUTHOR]

This paper addresses the results of experimental and model studies of a copper bromide vapor brightness amplifier at high pump pulse repetition rates. The features of the operating mode that are associated with the use of a reduced energy input into the discharge to obtain superradiance and amplification at frequencies above 100 kHz are noted. For the first time, for active media on metal vapors, the superradiance obtained at a pump pulse repetition rate of up to 300 kHz in a CuBr-vapor medium. A prototype model of a high-speed brightness amplifier has been developed. [ABSTRACT FROM AUTHOR]

A multifunctional research complex is presented, designed to obtain fundamental knowledge in the field of physics of discharge on the dielectric surface and in vacuum and gas gaps and to study the plasma properties of vacuum arcs in metal vapors and the properties of laser plasma using various techniques. [ABSTRACT FROM AUTHOR]

Laser powder bed fusion (LPBF) can produce high‐value metallic components for many industries; however, its adoption for safety‐critical applications is hampered by the presence of imperfections. The interdependency between imperfections and processing parameters remains unclear. Here, the evolution of porosity and humps during LPBF using X‐ray and electron imaging, and a high‐fidelity multiphase process simulation, is quantified. The pore and keyhole formation mechanisms are driven by the mixing of high temperatures and high metal vapor concentrations in the keyhole is revealed. The irregular pores are formed via keyhole collapse, pore coalescence, and then pore entrapment by the solidification front. The mixing of the fast‐moving vapor plume and molten pool induces a Kelvin–Helmholtz instability at the melt track surface, forming humps. X‐ray imaging and a high‐fidelity model are used to quantify the pore evolution kinetics, pore size distribution, waviness, surface roughness, and melt volume under single layer conditions. This work provides insights on key criteria that govern the formation of imperfections in LPBF and suggest ways to improve process reliability. [ABSTRACT FROM AUTHOR]

The effects of thermal and cold ionization in the near-critical region of metal vapors are taken into account jointly. The comparison with the results of the experiment and numerical simulation can serve as confirmation of the hypothesis put forward about the existence of electron jellium in the gas-plasma region and its coexistence with thermally ionized electrons. It is concluded that saturated metal vapors are most probably a gaseous metal with a sufficiently high conductivity. [ABSTRACT FROM AUTHOR]

A reliable and repeatable triggering technology for a megavolt gap switch with a low working coefficient η is an urgent need and a research focus. In this study, a novel method of hybrid plasma injection (HPI) driven by pulsed discharge inside a capillary was first proposed. The HPI actuator adopted a metal–polytetrafluoroethylene (PTFE)-stacked capillary, in which severe ablation could generate a hybrid plasma containing gas and metal vapor ionized component ejected outward from the nozzle. The HPI actuator could perform repeatedly with an extremely strong plasma injection and triggering ability and, thus, provided a solution for megavolt ultrafast bypass switches (UFBPSs). The evolution and the trigger properties of the HPI actuator were investigated, and the influence of the stacked material (Al, Zn, and Sn) and its proportion (3/15, 7/15, and 10/15) was studied, followed by the performance degradation in multi-shot. It was found that stacking chemically active and low-ionization-energy aluminum in a proportion of 7/15 strongly enhanced the HPI, with an initial velocity of 1200 m/s and a maximum height of 7.5 cm in 0.5 MPa SF6. In repeated operations, the HPI actuator performance degraded obviously due to capillary expansion and deformation, and the lifetime was tens of magnitude. Finally, the optimized HPI actuator was used to trigger a 7 cm–0.5 MPa SF6 gap, with a breakdown voltage of ∼1.5 MV. When a 100 kV DC voltage was applied (η < 7%), the gap was successfully and continuously triggered for 27 shots with the trigger delay ranging from 301 to 670 µs, indicating that the HPI actuator could effectively and repeatedly trigger megavolt-magnitude SF6 gaps at a very low η and was a good solution for megavolt UFBPSs. [ABSTRACT FROM AUTHOR]

The metal and molecular vapor separation analysis (MMVSA) of solid samples with an atomic absorption detector (AA) was investigated for the direct determination of manganese and copper in biological materials. An open column made with a molybdenum tube (i.d. 1.22 mm) with three-ring supporters was developed. Pure argon as a carrier gas flowed at a flow rate of 4.0 mL min−1. An ultrasonic agitation method was used for suspending NIST standard reference material powders in water. Manganese and copper in the biological powders were completely separated from Al, Ca, Fe, K, Mg, Na, and Zn elements by MMVSA under optimal experimental conditions. Several NIST biological samples were directly analyzed with satisfactory results. It was found that manganese and copper in biological materials without interferences from matrix elements could be directly determined after only an ultrasonic agitation of the biological powders. The advantages of the slurry sampling of MMVSA are simplicity, low cost, a high speed of analysis, and rapid calibration. [ABSTRACT FROM AUTHOR]

Powder particle spattering induced by the metal vapor jetting and vortex flow near the melt pool significantly influences the porosity of final product. In this work, a high-fidelity multiphysics model is developed at powder-scale that unidirectionally couples the powder spattering and laser welding simulation to study the spattering and porosity formation mechanism in laser powder bed fusion process. Vapor pressure from single-track laser welding simulation is applied as a moving boundary condition in a discrete element model to simulate particle spattering. Then, coupling simulation between the mass particles and laser welding is performed to study the interaction between melt pool and spattering particles. Two porosity formation mechanisms are observed in experiments and simulation. The first one is the spattering particles falling into melt pool directly and leaving un-melted or partially melted pores to the final product. The second mechanism is the particles near the melt track that are dragged to the melt pool bead and partially melted due to heat conduction. These partially melted particles can be observed as well in the bead region of depositions. [ABSTRACT FROM AUTHOR]

The article presents a physical model of the processes occurring in a nonequilibrium plasma of the working body of metal vapor lasers excited by an inductive pulsed-periodic high-freaquency discharge. The model is based on differential equations of population kinetics, electron energy balance, electric circuit, development of stimulated emission, etc. All equations are adapted to the features of induction discharge and the special geometry of the discharge chamber. A description of the model is presented for a variant of a copper vapor laser with a neon buffer gas. Peculiarities of the dynamics of the parameters of plasma and laser radiation under high-freaquency discharge conditions are noted. [ABSTRACT FROM AUTHOR]

Tetrakis(dithiocarboxylato)molybdenum(IV) complexes of the type Mo(S2CR)4 (R = Me, Et, iPr, Ph) were synthesized, characterized, and prescreened as precursors for aerosol assisted chemical vapor deposition (AACVD) of MoS2 thin films. The thermal behavior of the complexes as determined by TGA and GC-MS was appropriate for AACVD, although the complexes were not sufficiently volatile for conventional CVD bubbler systems. Thin films of MoS2 were grown by AACVD at 500 °C from solutions of Mo(S2CMe)4 in toluene. The films were characterized by GIXRD diffraction patterns which correspond to a 2H-MoS2 structure in the deposited film. Mo–S bonding in 2H-MoS2 was further confirmed by XPS and EDS. The film morphology, vertically oriented structure, and thickness (2.54 μm) were evaluated by FE-SEM. The Raman E12g and A1g vibrational modes of crystalline 2H-MoS2 were observed. These results demonstrate the use of dithiocarboxylato ligands for the chemical vapor deposition of metal sulfides. [ABSTRACT FROM AUTHOR]

We studied the effect of 5% v/v of water vapor during the Selective Catalytic Reduction of NO with NH3 (NH3-SCR-NO) using natural chabazite exchanged with Cu (1.3, 2.8 and 6.5-Cu/CHA) as the catalyst. The conversion of NO decreases slightly during light-off in the presence of water, but it reaches higher values in the range of temperature required for normal engine operation (280–420 °C). The maximum conversion at 350 °C increased with the Cu content, from 50% for 1.3-Cu/CHA to 90 and 95% with 2.8-Cu/CHA and 6.5-Cu/CHA, respectively. The initial Cu2+/Cu ratio was determined by H2-TPR, and the activity correlates with the fraction of Cu2+ species, which appears to be responsible for the NO reduction activity. During a test of the 2.8-Cu/CHA catalyst for 24 h we observed and modelled a small decay in activity observed during the first 3 h on-stream. The conversion remained stable thereafter, with or without 5% water in the feedstream. [ABSTRACT FROM AUTHOR]

Liquid column was a common problem in ultra-high power fiber laser-arc hybrid welding (UHLAHW) process, which has an adverse effect on the welding stability and weld formation. Hence, the influence of welding parameters on the behavior of liquid column was investigated systematically, including laser arc recombination process, laser power, and welding speed. As a result, the violent rising liquid column under laser was suppressed markedly after arc addition. However, it was hard to restrain liquid column upturn when laser power was extremely high, because the huge recoil pressure and shear force between metal vapor/plasma and molten pool could increase the upward momentum of melt. Besides, the height of liquid column and volume of spatters were directly influenced by welding speed, due to the welding line energy could significantly influence the flow of melt on the front of keyhole. By optimizing the welding process, the liquid column could be controlled, thereby significantly improving the welding process stability. Finally, a sound weld bead with qualified weld formation and 15.82-mm penetration was produced when the laser power was 21 kW and welding speed was 1.2 m/min under UHLAHW process. This work provides technical guidance for achieving stable welding process and qualified weld formation for thick plates. [ABSTRACT FROM AUTHOR]

Nonlocal versions of the reaction-diffusion type population equations can describe the evolution of spatiotemporal structures (patterns) depending on the equation parameter domain. Under conditions of weak diffusion, numerical methods have been used to compare the processes of spatiotemporal pattern formation in a nonlocal population model described by a one-dimensional generalized Fisher–Kolmogorov–Petrovsky–Piskunov equation with nonlocal competitive losses and in a two-dimensional nonlocal version of the kinetic model of quasi-neutral plasma of metal vapor active media described by the kinetic equation with nonlocal cubic nonlinearity. The effect of relaxation on the pattern formation is studied. [ABSTRACT FROM AUTHOR]

Samples of 241Am alloys with gold were synthesized for the first time. The alloys were obtained by the condensation of americium metal vapor on a flat gold substrate. The results of X-ray analysis of the phase composition of the obtained alloys are presented. Previously unknown intermetallic compounds of Am with Au were discovered: AmAu6 (tetragonal lattice, space group P42/ncm), AmAu (orthorhombic lattice, space group Pnma), AmAu (face-centered cubic lattice). The parameters of these crystal lattices were calculated. The effect of 241Am α-decay on the crystal structures of intermetallic compounds was studied. [ABSTRACT FROM AUTHOR]

The Lead (Pb) - Antimony (Sb) alloy derived from Jamesonite (Pb 4 FeSb 6 S 14) using the "Roasting - Reduction Smelting" method is typically isolated through a separation method known as "High Temperature Ash Blowing - Low Temperature Ash Blowing - Electrolytic Refining". However, the "Low Temperature Ash Blowing" separation method encounters several challenges, including elevated production pressure of refined Pb, significant emissions of smoke and dust, and suboptimal separation efficiency. This study utilizes the "Vacuum Gasification - Fractional Condensation" method as an alternative to the "Low Temperature Ash Blowing" method. The experimental findings demonstrate that by implementing specific optimal experimental conditions, such as a condensation temperature range of 904–1054K, a vacuum degree of 5Pa, a gasification temperature of 1173K, a holding time of 7h, and a height-diameter ratio of 0.27, condensates with Sb content exceeding 99.5 wt% can be procured, resulting in a direct Sb yield of 33 %. The remaining residues, with an Sb content ranging from 14 to 15 wt%, serves as a valuable input for the "Electrolytic Refining" process. This utilization significantly alleviates the burden on refined Pb production during the "Electrolytic Refining" process. The treatment procedure does not require the utilization of chemical reagents, and it generates no wastewater or exhaust gas. • A new method of "Vacuum Gasification - Fractional Condensation" for the separation of Pb-Sb alloy is proposed. • The migration patterns of Pb and Sb metal vapors were explored through the calculation of condensation rates. • The Sb's purity is greater than 99.5 wt%, and both intermediate products and residues can be effectively recovered. [ABSTRACT FROM AUTHOR]

Nanoparticle aggregate structures allow for efficient photon capture, and thus exhibit excellent optical absorption properties. In this study, a model of randomly distributed nanochain aggregates on silicon substrates is developed and analyzed. The Gaussian, uniform, and Cauchy spatial distribution functions are used to characterize the aggregate forms of the nanochains and their morphologies are realistically reconstructed. The relationships between the structural parameters (thickness and filling factor), equivalent physical parameters (density, heat capacity, and thermal conductivity), and visible absorptivity of the structures are established and analyzed. All the above-mentioned parameters exhibit extreme values, which maximize the visible-range absorption; these values are determined by the material properties and nanochain aggregate structure. Finally, Al nanochain aggregate samples are fabricated on Si substrates by reducing the kinetic energy of the metal vapor during deposition. The spectral reflection characteristics of the samples are studied experimentally. The Spearman correlation coefficients for the calculated spectral absorption curves and those measured experimentally are higher than 0.82, thus confirming that the model is accurate. The relative errors between the calculated visible-range absorptivities and the measured data are less than 0.3%, further confirming the accuracy of the model. [ABSTRACT FROM AUTHOR]

The magnetic characteristics of iron oxide nanopowder (Fe3O4 base phase) produced by electroerosion dispersion and consolidated at high pressures (2 GPa) and high temperatures (900, 1000, 1100, 1200, and 1300°C) for 0.07 h in contact with hexagonal boron nitride were studied. The nanopowder was produced by dispersing iron granules or shavings in plasma induced at contact points between the granules when electric pulses of high current and voltage were passed through them. The metal granules being dispersed are in a constantly circulating liquid (water) atmosphere, creating a pseudo-boiling layer from the granules. The liquid (water in this case) cools the granules to prevent them from being welded and oxidizes the metal vapors that emerge in plasma, forming nanosized iron oxide grains carried by the liquid flow into sedimentation tanks (powders with different grain sizes sediment in different tanks). Room-temperature studies of the magnetic characteristics of samples consolidated from iron oxide powders showed that the materials sintered at 1200 and 1300°C were soft magnetics with virtually zero hysteresis. Their specific magnetic moments at 5000 Oe were 128.4 and 126.4 emu/g and the coercive force was negligibly small: 5.1 and 4.5 Oe. The materials sintered at 1100°C were characterized by a specific magnetic moment of 90.4 emu/g and a relatively low coercive force of 9.1 Oe. The specific magnetic moments of the samples sintered at 900 and 1000°C were significantly lower and the coercive force higher: 40.2 and 42.1 emu/g and 37.9 and 32.4 Oe, respectively. X-ray diffraction with Rietveld refinement revealed that the materials consolidated at 900 and 1000°C contained 75–80 wt.% FeO and 25–20 wt.% Fe, while the materials sintered at 1100°C contained, along with 32 wt.% FeO and 2 wt.% Fe, a significant amount of Fe3N (66 wt.%). The materials consolidated at 1200–1300°C contained 100% Fe3N phase. Hence, under high pressures and increasing sintering temperatures, iron oxides are reduced and then iron is nitrided with nitrogen released from boron nitride, which improves the soft magnetic characteristics of the sintered materials. [ABSTRACT FROM AUTHOR]

Superparamagnetic iron oxide nanoparticles (SPIONs) coated with glucose (Glc-SPIONs) were prepared by a new approach called Metal Vapor Synthesis (MVS) and their morphological/structural features were investigated by transmission electron microscopy (TEM) and dynamic light scattering. TEM analysis revealed the presence of small roundish crystalline iron oxide nanoparticles in the organic amorphous phase of glucose, The particles were distributed in a narrow range (1.5 nm—3.5 nm) with a mean diameter of 2.7 nm. The hydrodynamic mean diameter of the Glc-SPIONs, was 15.5 nm. From 4 mg/mL onwards, there was a constant level of positive contrast in a T1-weighted sequence. In vitro experiments were performed in three cell lines: pancreatic cancer (PSN-1), human thyroid cancer (BCPAP), and human embryonic kidney non-tumor cells. We evaluated GLUT1 expression in each cell line and demonstrated that the exposure time and concentration of the Glc-SPIONs we used did not affect cell viability. PSN-1 cells were the most effective at internalizing Glc-SPIONs. Although significantly higher than the control cells, a lower Fe content was detected BCPAP cells treated with Glc-SPIONs. To confirm the involvement of GLUT1 in Glc-SPIONs internalization, cellular uptake experiments were also conducted by pre-treating cancer cells with specific GLUT1 inhibitors, All the inhibitors reduced the cancer cell uptake of Glc-SPIONs In vivo tests were performed on mice inoculated with Lewis lung carcinoma. Mice were treated with a single i.v. injection of Glc-SPION and our results showed a great bioavailability to the malignant tissue by the i.v. administration of Glc-SPIONs. Glc-SPIONs were efficiently eliminated by the kidney. To the best of our knowledge, our study demonstrates for the first time that Glc-SPIONs prepared with MVS can be electively internalized by tumor cells both in vitro and in vivo by exploiting one of the most universal metabolic anomalies of cancer. [ABSTRACT FROM AUTHOR]

The building of practical parts involves the application of metal-based powder bed fusion using a laser beam (PBF-LB/M), owing to its high-precision manufacturing. However, the quality of built parts obtained via the PBF-LB/M process varies with the building conditions, and a thorough understanding of the building mechanism has not been achieved owing to the complex and interrelated process parameters involved. The incident angle of the laser beam, which changes on the platform during the laser beam scan owing to the designed three-dimensional data, is among the principle parameters that affect the building aspects. In this study, the melt pool in the single-track formation during the PBF-LB/M process was visualised using a high-speed camera, and the influence of the laser incident angle on the ejection characteristics of spatter particles formed around the laser-irradiated area was investigated. Consequently, the spatter particles and metal vapour jets behaviour varied with the laser incident angle. There was a reduction in number of spatter particles owing to the origin of the incident direction being from behind the laser irradiation area. Additionally, the laser incident angle affected the melt pool morphology because of the depression in the melting. Furthermore, the burial depth of the pores varied with the laser incident angle, and was related to the depth of the depression during the melt pool formation. [ABSTRACT FROM AUTHOR]

In electrical discharge machining (EDM), gap control is the key to stable processing; the discharge gap plays a significant role in EDM. To determine the influence of the discharge gap on material removal and melt pool movement, which are two fundamental issues in EDM, high-speed photography and molecular dynamics (MD) simulations were used to study the discharge process. Research results demonstrate that the discharge gap has a significant influence on material removal during the discharge process. A smaller gap width produces more and larger removed materials. The influence mechanism of the gap width on material removal is explained as follows. A smaller gap width produces discharge plasma with a smaller diameter and greater heat flux. Discharge with a greater heat flux generates more material removed during the discharge process. In addition, a smaller gap width and greater heat flux produce a stronger interaction of metal vapor jets, generating a stronger shear force acting on the melt pool. The discharge gap also influences the movement of the melt pool and the final topography of the discharge crater through external pressure acting on the melt pool. Smaller gap width produces greater external pressure acting on the melt pool, generating a bowl-shaped melt pool and a discharge crater with a depression in the center and a bulge around the edge. A larger gap width produces less external pressure acting on the melt pool, generating a flat melt pool and a discharge crater with swelling in the center and a depression around the edge. [ABSTRACT FROM AUTHOR]

The dynamic behavior of the backside of a molten pool was observed by high-speed imaging during the full-penetration laser welding (FPLW) of the Inconel 617 superalloy, and the influence of the welding parameters on the dynamic behavior was studied. Furthermore, the relationship between the keyhole penetration status and the formation of defects, such as spatter and porosity, was investigated. The results showed that during FPLW, the backside of the molten pool was unstable and fluctuated periodically due to the dynamic pressure balance acting on the keyhole wall. The liquid metal under the keyhole was pushed out by the metal vapor in the keyhole to form a bulge protruding from the molten pool surface. The size and height of the bulge were not stable. The keyhole periodically penetrated through the bulge and sprayed spatter outward. Sometimes a sharp increase in the metal vapor recoil pressure in the local area under the keyhole would cause the liquid metal droplet to be pushed away from the molten pool. The proportion of the keyhole penetration time should be controlled within a moderate range (process window) to inhibit processing defects formation during the FPLW process. When the proportion exceeded this range, excessive spatter would lead to weld underfill. When the proportion was below this range, the keyhole-induced porosity in the weld would be generated. Increasing the welding speed helped to improve the stability of the keyhole. Compared with thick plate welding, the process window of thin plate welding was wider. [ABSTRACT FROM AUTHOR]