Search

A fundamental equation of state in terms of the Helmholtz energy is presented for mixtures of nitrogen, oxygen, and argon at any composition. It is expressed in terms of the residual Helmholtz energy and can be used to calculate all thermodynamic equilibrium properties including vapor–liquid equilibria. The parameters of the equations for the pure-fluid and mixture contributions are fitted exclusively to molecular simulation data so that the model has a predictive character. The description of the mixture-specific reducing parameters is realized via generalized correlations of the critical parameters of the pure fluids so that an extension of the model to additional components can be implemented straightforwardly. Extensive comparisons to experimental data and the GERG-2008 reference equation of state show that the prediction of thermodynamic properties is satisfactory. [ABSTRACT FROM AUTHOR]

For many years, the recombination of excited ions of argon, Ar + ( P 1 / 2 2 ) , has been assumed negligible under ambient conditions as compared to the recombination of ground-state ions, Ar + ( P 3 / 2 2 ). This opinion was confronted with detailed experimental results that seem to clearly support it. Here, we propose a new interpretation in light of our recent calculations, which shows that the recombination efficiency is comparable for both fine-structure states. Noteworthily, in our model leading to a picture consistent with the experiment, residual dimer ions emerge from A r + ( P 1 / 2 2 ) due to non-adiabatic dynamics effects and interplay in measured data. [ABSTRACT FROM AUTHOR]

Laser diode absorption spectroscopy is used to experimentally measure Ar(1s5) metastable density and translational gas temperature within a 94 GHz microplasma. A square two-dimensional photonic crystal (PhC) at this resonance frequency serves to ignite and sustain the plasma from 20 to 200 Torr (2.7 × 103–2.7 × 104 Pa) by using millimeter wave power from 300 to 1000 mW. Metastable density within the plasma is estimated from the absorption line shape of the laser traversing the PhC. The metastable density reaches an order of 1019 m−3 at lower pressure and decreases as pressure increases. From the Lorentzian line shape of the absorption profile at 811.53 nm, the gas temperature is extracted and found to increase from 500 K at 20 Torr to 1300 K at 200 Torr. These data are analyzed and compared with a zero-dimensional plasma model and with previous experimental plasma results at 43 GHz. [ABSTRACT FROM AUTHOR]

This work studied the rovibrational absorption spectral line-shape parameters of the P(1)–P(10) and R(0)–R(9) lines for Hydrogen fluoride perturbed by argon in the 0–0, 1–0, and 2–0 vibrational bands at 20–1000 K. A dataset of beyond-Voigt line-shape parameters (pressure broadening and shifting parameters, their speed dependencies, and the complex Dicke parameters) has been theoretically determined for the first time from generalized spectroscopic cross-section calculated by the full quantum scattering calculations. Then these parameters were employed to predict the line shape and asymmetry based on the partially-correlated speed-dependent hard-collision and the partially-correlated quadratic-speed-dependent hard-collision profiles. The effect of each parameter on the line shape and line asymmetry was further studied, which revealed that the beyond-Voigt effects were indispensable to accurately describe the line shape contour. Our results are in good agreement with the available experimental observations and provide a comprehensive set of theoretical references for further experimental measurements. [ABSTRACT FROM AUTHOR]

Diode-pumped rare gas lasers (DPRGLs) have the potential for high-energy laser output with high beam quality. The metastable concentration >1014 cm−3 and pump intensity >10 kW/cm2 are required in developing high-power and efficient DPRGLs. However, the kinetics of 1s and 2p levels (Paschen notation) under these conditions is unclear yet, particularly regarding the adverse effects of interference energy levels (e.g., 1s4 and 2p1–2p8). This study addresses this gap by measuring the number densities of 1s and 2p levels in a diode-pumped plasma jet metastable argon laser. The experiment was conducted with a much higher number density of 1014 cm−3 and a higher pump intensity of 12 kW/cm2 than our previous works. The results indicate that the adverse effect of 1s4 accumulation could be partially compensated, and the relative population distribution of 2p energy levels remained unchanged. However, the high gas temperature (>1000 K) caused a significant negative impact of high 2p levels (2p1–2p8), and the air environment weakened the effect of He collision relaxation. [ABSTRACT FROM AUTHOR]

The work carried out numerical calculations to study the dynamics of plasma-chemical processes in a glow discharge in argon with small admixtures of methane CH4 at low pressures. The dynamics of changes in the main conversion products and various types of ions in the process of establishing a discharge are presented. It is shown that the time it takes for the conversion products to reach a stationary regime is about t = 8 s. The main products of methane conversion in steady state are atomic hydrogen, as well as atomic and molecular carbon. [ABSTRACT FROM AUTHOR]

This paper is devoted to the experimental study of the characteristics of a continuous optical discharge (COD) sustained by high power continuous wave laser radiation at a wavelength λ = 1.08 μ m in high pressure argon. New data on the COD threshold laser power dependence of argon pressure in the range 20–50 bar is obtained. The COD threshold laser power is shown to be in good agreement with the data obtained by other authors and theoretical evaluations provided the contribution of plasma energy loss due to thermal radiation is taken into account properly. The maximum plasma temperature was estimated to be 20–21 kk or higher, favorable to obtain high UV spectral radiance. A study of the convective plume oscillations around COD in argon has been carried out. It is found that in the pressure range 25–35 bars the growth of the laser radiation power leads to a decrease in convection oscillation frequency from 33 to 29 Hz, while the radius of the convective plume grows accordingly. The oscillation frequency ν and characteristic radius of the convective plume r 0 were found to obey the similarity relation ν = 0.5 g / 2 r 0 previously established in experiments with COD in xenon. These results are promising for using COD in argon as a high brightness broadband UV radiation source. [ABSTRACT FROM AUTHOR]

The thermodynamic constraints of steel deoxidation are discussed based on calculated [%Me]–[%O] diagrams for different deoxidizing elements in pure Fe and five examples of steel grades, highlighting the influence of alloying on the equilibria. The role of deoxidation product oxides is considered with special emphasis on the activity of SiO2 and the possibility of utilizing slags with a very low aSiO2 to amplify the deoxidizing power of silicon. This effect was verified for SiCr spring steel and 18Cr8Ni stainless steel. The results indicate a strong reduction in equilibrium oxygen content. Different means for industrial implementation of this principle are discussed. The conventional steel/slag equilibration via gas stirring is tested in practice. As potentially more efficient methods, slag powder injection (argon, lance) and cored wire injection combined with argon bubbling are studied. In such treatments, specific tailored slag additives can be used for divergent steel grades to optimize steel cleanliness and inclusion engineering. [ABSTRACT FROM AUTHOR]

Abstract\nKEY POINTSFor muscovite in ancient Proterozoic and Archean terranes, quantitative modelling of age spectrum morphology shows that a significant plateau segment does not form in an age spectrum unless there was rapid cooling that either began before and continued through, or which initiated at, the time given by the plateau age. Further, the modelling shows that a well-developed plateau is not preserved unless such rapid cooling continues until ambient temperatures are reached that are <∼220–200 °C. It thus follows that the age of a well-developed plateau segment in a muscovite age spectrum is an accurate constraint on when the rock was first exhumed to (and/or last cooled at) shallow crustal levels. In a sample held at a higher ambient temperature, argon continues to be lost from the lattice at a significant rate, well past the time of so-called ‘isotopic closure’ predicted by application of Dodson’s formula. Parametric modelling shows that monotonic cooling paths do have a well-defined point, at which isotopic closure takes place, but to form an age plateau: (1) the rate of cooling must be rapid; and (2) cooling must continue at the same or similar rates, until temperatures are reached that are low enough to inhibit significant further loss of argon to the environment. Quantitative modelling shows how Dodson’s formula begins to fail once ambient temperatures rise above these numerically computed values for isotopic closure. Yet these numerically computed closure temperatures are far below the nominal closure temperature for muscovite, typically quoted as ∼ 350–400 °C. Therefore, these results have significant implications for models that utilise closure temperatures based on estimates using Dodson’s formula, when attempting to invert thermochronological datasets to obtain constraints on the temperature–time path.Quantitative modelling of age spectrum morphology can constrain possible temperature–time (T–t) paths because the shape of the age spectrum itself provides considerable information.Well-formed age plateaux developed in argon spectra from muscovite imply very rapid cooling towards ambient temperatures of ∼ 220–200 °C, which are well below the nominal closure temperatures for this mineral, typically quoted as 150–200 °C higher.There are multitudinous circumstances in which Dodson’s formula fail badly, when used to produce an estimate of closure temperature. Successful applications of this formula requires fast cooling to have continued to relatively low ambient temperatures.T–t paths should not be constructed by joining the dots provided by age estimates linked to closure temperatures inferred using Dodson’s formula since such T–t paths may be counter to the mathematics underlying the concept of isotopic closure. [ABSTRACT FROM AUTHOR]

Chemiluminescence of OH∗ is commonly employed as an optical indicator for the combustion process. It is widely recognized that the generation of OH∗ in hydrogen flames is primarily governed by the reaction H + O + M=>OH∗+M. In this study, the time histories of OH∗ chemiluminescence from the A→X band around 308 nm were recorded behind reflected shock waves for stoichiometric and lean H 2 /O 2 mixtures highly diluted in argon over the temperature range of 1130–3150 K and at the pressure of approximately 0.9 atm. Based on the time histories of OH∗ chemiluminescence, the best-fit reaction rate coefficient for the reaction H + O + M=>OH∗+M was determined as k = 3.17 × 1027exp(-121968 cal mol−1/RT) + 2.25 × 1017exp(-4246 cal mol−1/RT) cm6 mol−2 s−1 over the temperature range studied. Furthermore, by using the current rate coefficient in mechanism predictions, the predicted time histories and relative peak intensities of OH∗ chemiluminescence are in good agreement with experimental results reported in literature. • The time histories of OH∗ chemiluminescence up to 3150K are recorded. • The rate coefficient for H + O + M=>OH∗+M is determined. • The OH∗ sub-mechanism with the fitted rate coefficient has been verified. [ABSTRACT FROM AUTHOR]

Wood–plastic composites (WPCs) combine the properties of plastics and lignocellulosic fillers. A particular limitation in their use is usually a hydrophobic, poorly wettable surface. The surface properties of materials can be modified using ion implantation. The research involved using composites based on polyethylene (PE) filled with sawdust or bark (40%, 50%, and 60%). Their surfaces were modified by argon ion implantation in three fluencies (1 × 1015, 1 × 1016, and 1 × 1017 cm−2) at an accelerating voltage of 60 kV. Changes in the wettability, surface energy, and surface colour of the WPCs were analysed. It was shown that argon ion implantation affects the distinct colour change in the WPC surface. The nature of the colour changes depends on the filler used. Implantation also affects the colour balance between the individual variants. Implantation of the WPC surface with argon ions resulted in a decrease in the wetting angle. In most of the variants tested, the most significant effect on the wetting angle changes was the ion fluence of 1 × 1017 cm−2. Implantation of the WPC surface also increased the surface free energy of the composites. The highest surface free energy values were also recorded for the argon ion fluence of 1 × 1017 cm−2. [ABSTRACT FROM AUTHOR]

The study aims to comprehend the behavior of nitrogen in the argon oxygen decarburization (AOD) process during the production of nitrogen‐alloyed stainless steels, where the precise adjustment of nitrogen content plays a crucial role in enhancing productivity. Furthermore, the objective is to investigate the rate of change in nitrogen content when blowing a mixture of nitrogen and argon, instead of using pure nitrogen or argon alone. Hence, both nitrogenation and denitrogenation cases are examined, and kinetic models are developed. While solution thermodynamics can predict the final nitrogen content, the kinetics are influenced by the gas flow rate, steel temperature and composition, and levels of the surface active elements in the steel. By integrating a previously developed thermodynamic equilibrium equation with the kinetic models, nitrogen contents in the range of 0.150–0.400% can be reliably predicted. Consequently, the equations can be applied to predict nitrogen content during both the nitrogenation and denitrogenation stages in the reduction and desulfurization phases of the AOD process. [ABSTRACT FROM AUTHOR]

Plasma-catalysis has attracted significant interest in recent years as an alternative for the direct upgrading of methane into higher-value products. Plasma-catalysis systems can enable the electrification of chemical processes; however, they are highly complex with many previous studies even reporting negative impacts on methane conversion. The present work focuses on the non-oxidative plasma-catalysis of pure methane in a Dielectric Barrier Discharge (DBD) reactor at atmospheric pressure and with no external heating. A range of transition and noble metals (Ni, Fe, Rh, Pt, Pd) supported on γ-Al2O3 are studied, complemented by plasma-only and support-only experiments. All reactor packings are investigated either with pure methane or co-feeding of helium or argon to assess the role of noble gases in enhancing methane activation via energy transfer mechanisms. Electrical diagnostics and charge characteristics from Lissajous plots, and electron temperature and collision rates calculations via BOLSIG+ are used to support the findings with the aim of elucidating the impact of both active metal and noble gas on the reaction pathways and activity. The optimal combination of Pd catalyst and Ar co-feeding achieves a substantial improvement over non-catalytic pure methane results, with C2+ yield rising from 30% to almost 45% at a concurrent reduction of energy cost from 2.4 to 1.7 and from 9 to 4.7 . Pd, along with Pt, further displayed the lowest coke deposition rates among all packings with overall stable product composition during testing. [ABSTRACT FROM AUTHOR]

The effect of the initial atoms distribution on the molecular dynamics (MD) simulation of a model atomic fluid (argon) is investigated for the case of the isochoric phase transition to the supercritical state. In particular, the case of uniformly distributed atoms in the simulation domain is compared with the case of separated liquid and vapor atoms. The sensitivity of simulations to asymmetric nanoscale perturbations in the boundary is also studied. Despite its high computational cost, the MD approach has the potential to successfully address long‐standing problems in computational fluid dynamics (CFD), especially those associated with mathematical singularities, such as contact angles, vortices, phase transitions and so forth. Unlike conventional CFD simulations, where the initial condition is the pressure or velocity distribution in the simulation domain, MD simulations also require the initial position of each molecule. Thus, it is important to understand whether a judicious choice of the initial distribution of molecules can reduce the overall computation time of the simulation. The evolution of the model fluid system during the phase transition was simulated using a Lennard‐Jones interatomic potential, corrected with the Lorentz–Berthelot mixing rule for the interactions with the solid walls. The system was allowed to relax until equilibrium, and then a Heaviside temperature step was applied to the wall to bring the system to supercritical conditions. Results show the initial choice of the atoms distribution can significantly affect the computational time, while the effect of asymmetric perturbations on the boundary is negligible. [ABSTRACT FROM AUTHOR]

Featured Application: Development of ultrapure materials technology. We demonstrate measurements of the absorption coefficient α ≈ 2.5 × 10−7 cm−1 in synthetic crystalline quartz at a wavelength of 1071 nm with a signal-to-noise ratio of 10/1 using the Time-resolved photothermal common-path interferometry (TPCI) scheme. It utilized cells filled with flowing argon and eliminated the influence of ambient air absorption. The scheme elements limiting the sensitivity of measurements at the level of ≈7.8 × 10−8 cm−1 were revealed. When these elements are replaced by better ones in terms of their thermal influence, the sensitivity of absorption coefficient measurements in crystalline quartz is ~10−8 cm−1. The calculation of the correction due to these optical elements of the values of the measured absorption coefficients is also described, which makes it possible to achieve the same sensitivity without replacing the elements. The improved scheme confirms the presence of the spatial inhomogeneity of absorption with a minimum coefficient of 2.5 × 10−7 cm−1 in synthetic crystalline quartz. The discrepancy of the absorption coefficient values in different regions of the crystal in the presented series of experiments was 2.5 × 10−7 cm−1 to 4 × 10−6 cm−1. Taking into account the ratio of thermo-optical parameters and the heat diffusion effect, the calculation shows that for quartz glasses the corresponding sensitivity of the absorption coefficient measurements equals ≈1.5 × 10−9 cm−1. [ABSTRACT FROM AUTHOR]

In this paper, the dissolution behavior of crystal-originated particle (COP) in 300 mm Czochralski silicon under argon annealing was investigated. The latex sphere equivalent size distributions of defects along the depth direction in silicon wafers annealed under different conditions were quantified utilizing chemical–mechanical polishing and localized light scattering inspection. The interstitial oxygen concentration profiles were quantified by secondary ion mass spectrometry, and the distributions of oxygen precipitation within annealed wafers were obtained based on peak analysis. Furthermore, the classical theoretical model was employed to elucidate the depth-dependent dissolution of COP. Based on the initial COP sizes and oxygen concentrations, the relationship between COP sizes and depth after annealing was calculated. The depth distributions of defects obtained by combining the dissolution of COP from calculation with the changes of oxygen precipitation were found to be highly consistent with the measurement results. These findings could enhance the understanding of the mechanism of COP dissolution, which contributes to the production of defect-free silicon wafers for nanometre-scale integrated circuits. [ABSTRACT FROM AUTHOR]

Narrowly divergent high-energy electron beam is experimentally demonstrated during the interaction of terawatt Ti:Sa laser radiation with a nitrogen gas-cluster jet at gas pressure corresponding to the boundary of the condensation region. A collimated electron beam with an energy of up to 10 MeV and a divergence of 10 mrad at a plasma concentration of ~1019 cm–3 is obtained. The use of nitrogen instead of argon or krypton significantly improves the spatial (divergence) and energy (charge and spectrum shape) properties of the generated electron beam. The formation of clusters in a supersonic jet is observed and their composition is thermodynamically analyzed. [ABSTRACT FROM AUTHOR]

Effects of the propellant, propellant mass-flow rate, and discharge voltage on the characteristics of the plume of small Hall thrusters are studied using a particle-in-cell Monte Carlo collisions program. It is shown that with the same discharge voltage and mass flow, the divergence angle of the xenon plume is smaller than that of argon and is not linearly dependent on the propellant mass flow rate. Moreover, the effect of the discharge voltage on the plume divergence angle can be significant. As the discharge voltage increases from 100 to 300 V, the plume divergence angle decreases, but in the range 300–400 V, it increases with the discharge voltage. The obtained data can be useful for the design and improving the efficiency of Hall thrusters. [ABSTRACT FROM AUTHOR]

The Panel on Food Additives and Flavourings (FAF) provides a scientific opinion re‐evaluating the safety of the two food additives argon (E 938) and helium (E 939). Argon (Ar) and helium (He) are two noble gases, highly stable single atoms. Their chemical inertness is well known. Their physicochemical properties have served as a basis for their previous evaluations by SCF and JECFA, which have considered the use of these food additives safe even in the absence of a toxicological evaluation. No business operator or other interested party provided information in response to the call for data published by EFSA to support the re‐evaluation of these two food additives with respect to their identity and specifications, manufacturing process (including the identification and quantification of potential impurities) and how they are applied to food to exert their technological function. One business operator replied to the call for data issued by EFSA reporting use levels of E 938 as a packaging gas in one food category. Based on their physicochemical properties, both gases are considered by the Panel to be of low toxicological concern when used as food additives. No information was available on the potential presence of impurities of toxicological concern resulting from the manufacturing process(es) applied to the production of the food additives E 938 and E 939. The Panel however noted that a minimum purity of 99.0% is required to comply with existing specifications. The Panel concluded that the use of argon (E 938) and helium (E 939) as food additives does not raise a safety concern. The Panel recommended an amendment of the existing EU specifications to introduce the respective CAS numbers. [ABSTRACT FROM AUTHOR]

We interpret the recent MicroBooNE data on neutral-current single π 0 production on argon with the hypothesis that this process occurs via Delta excitation. We calculate the flux-integrated total cross section with our RPA-based model which allows for a simultaneous description of Delta-mediated resonant and coherent pion production. We also discuss the ratio between the two exclusive measurements with one proton and zero protons in the final state. [ABSTRACT FROM AUTHOR]

The results of experiments with a model of an optically pumped rare-gas laser are presented. Laser generation was produced simultaneously at three wavelengths (912.3, 893.1, and 877.7 nm) using a gas mixture consisting of 98% He (buffer gas), 1.5% Ar, and 0.5% Kr. Dependence of generation power and of the ratio of the intensities of individual lines in total generation on consumption of the gas mixture, on cuvette pressure, and on the discharge pulse repetition rate has been studied experimentally. The maximum laser power (the sum of all the wavelengths) was ~8 mW. [ABSTRACT FROM AUTHOR]

Inert gas argon has important applications in the fields of daily life, industrial manufacture and nuclear environmental monitoring. The key to its application is to selectively and efficiently separate and purify Ar from complex gas components. However, the separation of O2 and Ar at normal temperature is full of challenge due to their similar molecular sizes and adsorption properties as well as their close boiling point. In industry, high purity Ar is mainly produced by low temperature rectification, which is mature technology, but the equipment is large, high-energy consumption and explosive. Adsorption separation is a common method of gas separation. Molecular sieves are the most widely used material due to their huge specific surface area, aboudant pore structure and excellent adsorption properties. The silica tetrahedron in molecular sieve is electrically neutral, while the aluminum tetrahedron is electronegative, which makes it necessary to use H+ or Na+ outside the molecular sieve skeleton to maintain electrical neutrality. In actual application, the interaction between adsorbent and adsorbent can be enhanced by ion-exchange modification of molecular sieve material, so as to effectively improve the O2/Ar separation capacity of molecular sieve. In this paper, the application of ion-exchange modified molecular sieve materials in the field of O2/Ar adsorption separation was systematically summarized and reviewed. The results show that the O2/Ar separation coefficients of molecular sieves modified by alkaline earth metal ions like Ca2+, Sr2+ and Ba2+ can reach about 2.0, while that of Ce3+-exchanged X-type molecular sieve is as high as 5.9, it is an ideal adsorption material for O2/Ar separation. However, the high separation coefficient is limited to the range of low partial pressure, and the O2/Ar separation coefficient under normal pressure is below 2.0. The Ag+-exchanged molecular sieves, namely silver-loaded molecular sieves, have excellent Ar adsorption selectivity. At present, the O2/Ar separation coefficients of silver-loaded molecular sieve materials at atmospheric pressure are around 2.0, but the preparation cost of silver-loaded molecular sieves is high, and it is more suitable for small-scale separation applications, it means that the efficient separation of O2 and Ar at normal temperature and pressure is still challenging. The development of novel ion-exchange modified molecular sieve materials with high adsorption capacity and high adsorption selectivity for the separation of O2 and Ar is still one of the focuses and trends of future research projects.

The importance of microwave device reliability and performance for microscale devices motivates a more fundamental understanding of breakdown mechanisms in this regime. Microwave breakdown theories predict breakdown when electron production balances electron loss. Electron production depends strongly on the ionization rate ν i ; however, previous studies either used the measured ν i in macroscale gaps or the empirical formula for DC voltage, inaccurately predicting ν i in microscale gaps. Alternatively, this work characterizes ν i in microwave microplasmas by using particle-in-cell simulations. We calculated ν i in argon gas at atmospheric pressure for 2–10 μm gaps under AC fields ranging from 1 to 1000 GHz. The behavior of ν i may be separated into two regimes by defining a critical frequency f c r that depends on the amplitude of the applied voltage, gap distance, and pressure. For frequency f < f c r , the electrodes collect the electrons during each cycle and the electron number oscillates with the electric field, causing ν i / f to roughly scale with the reduced effective field E e f f / p. For f > --> f c r , the phase-space plots indicate that the electrons are confined inside the gap, causing the electron number to grow exponentially and v i / p to become a function of E e f f / p. These results elucidate the ionization mechanism for AC fields at microscale gap distances and may be incorporated into field emission-driven microwave breakdown theories to improve their predictive capability. [ABSTRACT FROM AUTHOR]

In this work, the Yb2Si2O7 interphase was prepared on SiC fibers using the sol–gel method. The influence of sol concentration on the morphology of the interphase was discussed. After heat treatment in argon at 1200°C for 1 h, the Yb2Si2O7 was grown in situ on the fiber surface, forming an interphase layer. Then, SiCf/Yb2Si2O7/SiC minicomposites were prepared by chemical vapor infiltration (CVI). The Yb2Si2O7 interphase exhibited no changes throughout the high‐temperature preparation process and maintained stability and compatibility with the fiber and matrix. The tensile strength of SiCf/Yb2Si2O7/SiC minicomposites with Yb2Si2O7 interphase was significantly higher than SiCf/SiC minicomposites without interphase. The crack deflection, interfacial debonding, and fiber pullout were observed in the tensile fracture of the SiCf/Yb2Si2O7/SiC minicomposites. [ABSTRACT FROM AUTHOR]

High-temperature annealing (HTA) is one of the most promising techniques to produce high-quality, cost-efficient AlN templates for further epitaxial growth of AlGaN devices. Unfortunately, the yield of this process seems to be limited due to the restricting face-to-face configuration that is typically used, in which contaminations of the template surface can occur easily. A high yield is crucial for process transfer into industry. Indeed, templates that are annealed in open-face configuration suffer from surface degradation due to excessive AlN evaporation during the course of the annealing process. To highlight the physics that are restricting the open-face approach of the process, sublimation behavior of AlN at temperatures and atmospheres typically used in HTA processes has to be examined. In this study, we use the Knudsen effusion mass spectrometry technique to confirm the previously published results on equilibrium partial pressures of species above AlN. Based on the experimentally determined data and further AlN sublimation experiments, the apparent sublimation coefficient of AlN in N2 and Ar atmospheres at HTA process conditions can be derived. Despite N2 having a stabilizing effect on AlN during HTA, the still high decomposition rates of several hundred nanometers per hour can explain the excessive damage that is typically observed if AlN/sapphire templates are annealed in an open-face configuration. Finally, based on theoretical considerations, a strategy to reduce the sublimation of AlN during HTA in open-face configuration is suggested. [ABSTRACT FROM AUTHOR]

The paper presents the results of the study of the processes of self-propagating high-temperature synthesis of Zr-1%B alloy and its refining by electron beam melting. Experiments on the influence of boron’s amorphous and crystalline modifications on the safety parameters of the synthesis process of Zr-1%B alloy necessitated the conversion of amorphous boron into crystalline form by electron beam melting, with an increase in its purity from 94% to 99.9%. High efficiency of vacuum induction and electron beam equipment was demonstrated, which provided a high purity of the Zr-1%B alloy of at least 99.9%. The alloy ingots had a uniform distribution of the alloying element (boron) all over the volume. The obtained alloy is suitable for the production of materials with thermal neutron capture cross-sections of up to 40 barns for neutron protection.

In order to produce cold plasma at atmospheric pressure, a multi-channel RF, of (1, 2, 3, and 4 MHz) frequencies, plasma jet system is developed using argon as the working gas. This system consists of two parts, a multi-channel power supply (of a power of 100 W) and a plasma jet. A strong electric field is created that ionizes and excites argon ions. The I-V characteristics of the system and the electron temperature and density for different powers (20, 50, 70, and 80 W), gas flow rates (10, 20, 30, and 40 sccm) (standard centimeter cubic per minute) at different frequencies (1, 2, 3, and 4 MHz) are studied, using the optical emission spectroscopy method. This system can be used in medical applications and material treatment with high efficiency. [ABSTRACT FROM AUTHOR]

Matrix isolation infrared spectroscopy was used to characterize a 1:1 complex of methanol (CH3OH) and benzene (C6H6). Co-deposition experiments with CH3OH and C6H6 were performed at 17–20 K using nitrogen and argon as the matrix gases. Several new infrared peaks in the co-deposition spectra were observed near the fundamental absorptions of the CH3OH and C6H6 parent molecules and these new peaks have been attributed to CH3OH–C6H6 complexe. Experiments were also performed with isotopic CD3OD and C6D6 and the corresponding infrared peaks of the isotopologue complexes have also been observed. Theoretical calculations were performed for the CH3OH–C6H6 complex using the M06-2X, ωB97X-D, MP2, and CCSD(T) methods with the aug-cc-pVDZ and aug-cc-pVTZ basis sets. Full geometry optimizations followed by vibrational frequency calculations were performed for several initial starting geometries and three stable minima were found for the CH3OH–C6H6 complex. The first has the CH3OH above the C6H6 ring with the OH hydrogen interacting with the π cloud of the ring (H–π complex), the second has the CH3OH above the C6H6 ring with the OH oxygen interacting with one or two of the C–H bonds of the ring (CH–O 1 complex), and the third has the CH3OH towards the side of the C6H6 ring with the OH oxygen interacting with two of the C–H bonds of the ring (CH–O 2 complex). The H–π complex structure is predicted to be the lower energy structure by ∼8 kJ/mol compared to the two CH–O structures. Comparing the theoretically predicted infrared spectra for the optimized CH3OH–C6H6 complex structures to the experimentally observed infrared peaks in argon and nitrogen matrices, it is concluded that in the argon matrices only the H–π complex structure is being observed, whereas in the nitrogen matrices the H–π complex and CH–O 1 complex structures are being observed. [ABSTRACT FROM AUTHOR]

Isotopic (2H and 15N) labelling and IR absorption spectroscopy have been used to study UV-induced transformations of cyanoacetylene in cryogenic noble gas matrices. The results obtained indicate that all observed isomerization processes involve single, isolated molecules of the precursor. No photoproducts have been found that would imply the recombination of fragments originating from different molecules. [ABSTRACT FROM AUTHOR]

The Module-0 Demonstrator is a single-phase 600 kg liquid argon time projection chamber operated as a prototype for the DUNE liquid argon near detector. Based on the ArgonCube design concept, Module-0 features a novel 80k-channel pixelated charge readout and advanced high-coverage photon detection system. In this paper, we present an analysis of an eight-day data set consisting of 25 million cosmic ray events collected in the spring of 2021. We use this sample to demonstrate the imaging performance of the charge and light readout systems as well as the signal correlations between the two. We also report argon purity and detector uniformity measurements and provide comparisons to detector simulations. [ABSTRACT FROM AUTHOR]

The paper presents the results of the study of the processes of self-propagating high-temperature synthesis of Zr-1%B alloy and its refining by electron beam melting. Experiments on the influence of boron's amorphous and crystalline modifications on the safety parameters of the synthesis process of Zr-1%B alloy necessitated the conversion of amorphous boron into crystalline form by electron beam melting, with an increase in its purity from 94% to 99.9%. High efficiency of vacuum induction and electron beam equipment was demonstrated, which provided a high purity of the Zr-1%B alloy of at least 99.9%. The alloy ingots had a uniform distribution of the alloying element (boron) all over the volume. The obtained alloy is suitable for the production of materials with thermal neutron capture cross-sections of up to 40 barns for neutron protection. [ABSTRACT FROM AUTHOR]

Herein, the graphene nanoplatelets (GNPs) anode is prepared using a facile, chemical‐free, and scalable approach that combines probe sonication and microwave treatment in an argon condition. The resulting GNPs exhibit a significant number of structural defects (ID/IG: 0.262), which provide abundant active sites to store lithium ions and offer sufficient pathways for the quick transfer of lithium ions and electrons. In lithium‐ion batteries (LIBs), the GNPs anode exhibits an outstanding electrochemical performance, achieving a high reversible 414 mAh g−1 capacity at the high current density of 1 A g−1 after 350 cycles. The anode maintains desirable capacities of 167 and 150 mAh g−1 even at elevated current densities of 4 and 5 A g−1, respectively. Importantly, it exhibits remarkable cycling performance with more than 100% of the initial reversible capacity retention after 350 cycles. The outcomes show noticeably enhanced performance characteristics, suggesting the potential for developing microwave‐treated graphene anode for long‐lasting and high‐performance LIBs. [ABSTRACT FROM AUTHOR]

Utilizing alternative propellants has been recognized as a strategy to reduce the total cost of propellants in electric propulsion-based missions. The aim of this study is to quantify the Hall effect thruster (HET) performance and operating characteristics using a Kr–Ar mixture to enable mission designers to evaluate the impact on mission and spacecraft design. We present the performance and plume plasma properties of the P5 5 kW-class HET operated with a Kr–Ar mixture with Ar volumetric flow rate fractions from 0 to 100%. The thruster is characterized at discharge power levels of 2.6 kW and 4.1 kW at constant discharge current and voltage over the range of Ar fractions. Despite higher ionization energy and lower mass of Ar, the thruster exhibited a similar level of thrust within 2% when comparing the pure Kr and 26%-Ar mixture cases. The derived ion energy distribution functions and analytical modeling suggest that the characteristic length for the ionization region is extended as the Ar fraction increases. The increased residence time of Kr at the extended ionization region and background energetic electrons from the ionized Ar neutrals are considered to cause this enhanced ionization of the injected Kr neutrals. This leads to a 6% higher Kr ion density at the 26%-Ar case even at the 16% less injected Kr neutral density than in the pure Kr case. The enhanced Kr ionization and generated Ar ions in the 26%-Ar case consequently led to a comparable thrust with that of the pure Kr case. The study indicates that mixing Ar with approximately 26% volumetrically with Kr can provide a similar or even higher thrust performance at the same discharge power. This will be particularly advantageous for various space missions that require high impulses by reducing the total cost of the propellant. [ABSTRACT FROM AUTHOR]

Weld surfacing is the process of applying a layer of metal to the surface of metal objects by simultaneously melting the substrate. As a result of this process, the metal content of the padding weld can be as high as several tens of percents. It is a method used to regenerate machine parts and improve the properties of the surface layer, increasing its resistance to abrasion, corrosion, erosion, and cavitation. It also supports the repair and creation of permanent protective coatings in the engineering, automotive, energy, and aerospace industries. This makes it possible to repair damaged parts instead of completely replacing them, saving time and production costs. Plasma surfacing technology is used for components that require high hardness and corrosion resistance under various environmental conditions. Plasma wire surfacing is not sufficiently presented and described in the current literature, which creates problems in determining the appropriate process parameters. The influence of variable plasma surfacing parameters on steel C45 significantly affects surfacing weld geometry, the dilution factor, and microhardness. Higher currents can increase the dilution factor, integrating more base metal into the weld pool, which may alter the chemical composition and mechanical properties of the weld. Variations in surfacing speed and heat input also affect the microhardness of the surfaced joint, with higher heat inputs potentially leading to softer welds due to slower cooling rates. Optimizing these parameters is essential to achieving desired surfacing weld characteristics and ensuring the structural integrity of C45 steel joints. This paper presents the influence of varying plasma surfacing parameters on the surfacing geometry, the dilution factor, and microhardness. The tests were carried out on a Panasonic TM-1400 GIII automated surfacing machine with CastoMag 45554S solid wire as the filler material. Flat bars of C45 steel were prepared, and then the variable parameters of the surfacing process were developed. Tests were carried out to determine the dilution factor, followed by microhardness measurements. The results showed a significant dependence of the effect of the parameters on the surfacing geometry and the dilution factor. [ABSTRACT FROM AUTHOR]

The problems associated with the formation of an external cluster flow that we previously discovered, which is formed in the external field of a traditional supersonic jet and called the cluster wake, are discussed. The reasons for the long-term anomalous glow of the cluster wake are studied. The results of a spectral study of the induced radiation of a supersonic clustered argon flow in the region of particle excitation (on an electron beam) and beyond are presented. The anomalies in the glow of a traditional spindle-shaped jet and a flow of heavy clusters are discussed. The possible causes of the observed anomalous phenomena are presented based on the above comparisons of the results obtained. The role of the energy exchange between clusters and the background gas in the afterglow of a cluster wake is established. The wavelengths and corresponding transitions in ArI and ArII that are responsible for the anomalous emission are determined. The lifetimes of particles in the excited state in the central part and on the periphery of the clustered flow are determined. [ABSTRACT FROM AUTHOR]

Efficient handling of high heat flux on the plasma‐facing components, particularly the divertor targets, poses a significant challenge for the Chinese Fusion Engineering Testing Reactor (CFETR) with fusion power of Gigawatt. This work investigates the divertor plasma detachment of CFETR with a standard ITER‐like divertor geometry by neon (Ne) or argon (Ar) impurity seeding using UEDGE code. The cross‐field drifts terms are switched off, and fluid neutral models and a "fixed‐fraction" impurity model are applied to enable efficient simulations for the study of CFETR detachment. In order to reduce the heat load on the divertor targets below the acceptable level (<10 MW/m2), the impurity fraction (f), pumping speed (S), and upstream density are varied to identify the suitable operations window during Ne seeding. The effects of Ne and Ar impurities on the plasma detachment are compared. It is found that with the power across the core‐edge interface PSOL = 200 MW and separatrix density of 2.8 ×$$ \times $$ 1019m−3$$ {\mathrm{m}}^{-3} $$, Ne impurity fraction ≥1.7%, and Ar impurity fraction ≥0.24% can achieve the partial detachment. Achieving similar total radiation power (˜148 MW), the Ne fraction is 2.3% and the Ar fraction is 0.24%. Moreover, the simulation results indicate that Ar exhibits better power radiation efficiency and core compatibility compared with Ne. [ABSTRACT FROM AUTHOR]

A linear plasma device (LPD) module has been developed under the BOUT++ framework to simulate plasma transport in the MPS‐LD. However, previously, the LPD module used a simplistic neutral particle model that only includes particle density and velocity, which prevents the full understanding of the plasma‐neutrals interactions. In this work, we further optimize the neutral model by using a more complete neutral fluid model containing the continuity equation, momentum equation, and energy equation. The reactions such as charge exchange, excitation, and radiation collisions are included. Since the neutral particle source is mainly provided by particle recycling from the target, a particle recycling model is employed, which includes both fast reflection and slow thermal release. The upgraded LPD module is applied to simulate the argon (Ar) discharge experiment of MPS‐LD, and the benchmark against experiment measurement and SOLPS‐ITER simulation results are presented. Good agreements are obtained, showing the validation of the upgraded module. After that, the impact of particle recycling on Ar plasma is investigated. It is found that a higher recycling coefficient (R) promotes the achievement of high‐density plasma at the target. The recycled Ar atoms change target plasma pressure as well as plasma‐neutral collisions, which both contribute to plasma momentum loss, thus promoting the rollover of ion flux to the target. [ABSTRACT FROM AUTHOR]

Melt pool dynamics in metal additive manufacturing (AM) is critical to process stability, microstructure formation, and final properties of the printed materials. Physics-based simulation, including computational fluid dynamics (CFD), is the dominant approach to predict melt pool dynamics. However, the physics-based simulation approaches suffer from the inherent issue of very high computational cost. This paper provides a physics-informed machine learning method by integrating the conventional neural networks with the governing physical laws to predict the melt pool dynamics, such as temperature, velocity, and pressure, without using any training data on velocity and pressure. This approach avoids solving the nonlinear Navier-Stokes equation numerically, which significantly reduces the computational cost (if including the cost of velocity data generation). The difficult-to-determine parameters' values of the governing equations can also be inferred through data-driven discovery. In addition, the physics-informed neural network (PINN) architecture has been optimized for efficient model training. The data-efficient PINN model is attributed to the extra penalty by incorporating governing PDEs, initial conditions, and boundary conditions in the PINN model. [ABSTRACT FROM AUTHOR]

Based on the Hagena scaling law, the cluster size in a gas jet is dependent on the equivalent diameter of a conical nozzle. In this work, the effect of the equivalent diameter deq of a conical nozzle on cluster size is separated into the individual effects of the throat diameter d and the half-opening angle α by comparing the Rayleigh scattering signals from gas jets. Nine types of conical nozzles with three different throat diameters (0.3, 0.5, and 0.7 mm) and three different half-opening angles (8.5°, 14.0°, and 24.2°) are used to produce argon gas jets at gas backing pressures from 10 up to 80 bar. The experimental results show that the effect of the throat diameter d is almost the same as that expected by the scaling law. However, the scaling law overestimates the effect of the half-opening angle α. The result is helpful for the precise characterization of cluster size and further understanding the interaction between intense laser and gas clusters. [ABSTRACT FROM AUTHOR]

An efficient and facile strategy has been developed for the synthesis of symmetrical pyridines in good to excellent yields from ketoxime acetates and DMFDMA in the presence of FeCl3 at 120 °C for 6 h under argon atmosphere. In this protocol, DMFDMA acts as an effective C1 synthon. The use of inexpensive catalysts, no need for additional ligands and additives, and excellent functional group tolerance are the perks of this protocol. [ABSTRACT FROM AUTHOR]

As a typical liquid-like thermoelectric material, Cu2 Se not only has good electrical transport performance, but also has low lattice thermal conductivity. Nanoengineering is an effective method to achieve high thermoelectric properties for thermoelectrics. However, nanoscale Cu2 Se particles are extremely easy to be oxidized in the process of synthesizing, thus affecting its thermoelectric performance. In order to study the effect of powder reduction on the thermoelectric performance of Cu2 Se, nano-sized Cu2 Se powders were synthesized by hydrothermal method. Hydrogen argon mixed gas ( hydrogen volume fraction of 5%) and pure argon were used to purge the powders, respectively. Cu2 Se bulk materials with density above 95% were prepared by spark plasma sintering. The results show that the oxygen content of Cu2 Se bulk is significantly reduced after powder reduction, and there is a 41% decrease in thermal conductivity at 800 K, with a 16% increase in ZT value. [ABSTRACT FROM AUTHOR]

Copyright of Industrial Water Treatment is the property of CNOOC Tianjin Chemical Research & Design Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

An 1/4 ladle water model is build, a differential flow bottom blowing method with different flow ratios is proposed, and an Eulerian multiphase flow model which coupling of the Eulerian model and the Volume of Fluid (VOF) interface tracking method was established to study the flow field, mixing time, slag eyes area and its fluctuation in ladle water model. The result shows that the mixing time increases first and then decreases with the increase of bottom blowing ratio. The mixing time is longest in single nozzle and reaches its shortest at ratio of 2:1. Compared to equal flow and single nozzle, using differential flow can reduce the slag eyes area. The calculated results of mixing time and slag eyes area agree well with the experimental results. Compared to the traditional equal flow bottom blowing method and single nozzle, using the differential flow with a flow ratio of 2:1 can reduce the stirring consumption caused by the collision between two streams, and the range of low-speed eddy current is reduced. The volume average values of turbulent kinetic energy and viscosity under equal flow and 2:1 differential flow are relatively close; after 2:1, they will significantly decrease with increasing bottom blowing ratio, reaching the minimum value during single nozzle. The model has a good capture effect on the sharp interface between water and oil. [ABSTRACT FROM AUTHOR]

Established a 1/4 water model experimental system to study the mixing phenomenon and slag eye during ladle refining process. On the basis of traditional equal flow bottom blowing method, differential flow bottom blowing methods with different flow ratios were proposed, the optimal bottom blowing ratio that minimizes mixing time and slag eyes area was founded, and the optimization effect of differential flow bottom blowing method on mixing time and slag eyes area at various angles and eccentricities was verified. The results indicate that the mixing time is the shortest in most cases when using the bottom blowing method with a differential flow ratio of 2:1 when the angle is within 135 deg, after 2:1, the mixing time increases with the increase of bottom blowing ratio, and the mixing time in single nozzle is the longest in almost all cases. The influence of nozzle angle on slag eyes area is greater than that of eccentricity. The differential flow bottom blowing method can significantly reduce the slag eyes area, and the bottom blowing ratio that minimizes the slag eyes area is 4:1. However, the fluctuation degree of slag eyes area will increase with the increase of bottom blowing ratio. [ABSTRACT FROM AUTHOR]

Examining the kinetics involved in the Argon Oxygen Decarburization (AOD) process, especially in the hotspot and emulsion zones within distinct reactors, can offer a deeper understanding of the refining mechanism in stainless-steelmaking. A predictive dynamic model has been formulated to estimate the effects of different refining processes, encompassing decarburization, desiliconization, demanganization, and chromium removal. The model includes a sub-model for heat loss calculation. The FactSage™ software, along with its macro programming capability, was utilized to incorporate thermochemical and kinetic information into the model. The model forecasts that the predominant chromium removal occurs within the hotspot zone, while carbon, silicon, and manganese removals occur in both the hotspot and emulsion zones. The predictions regarding the transient compositions of steel and slag, as well as the temperature of the steel bath, align with the plant data (Average of five heats), showcasing consistency. [ABSTRACT FROM AUTHOR]

The self-ignition of a propylene–oxygen–argon stoichiometric mixture with a volumetric argon content of 95% is studied. The experiments are performed on a shock tube, which is part of the Shock Tube Experimental Complex of the Institute of Mechanics of Moscow State University, in conditions behind the reflected shock wave. The time dependencies of signals from a piezoelectric pressure sensor, a thermoelectric detector, and an optical section configured to record the radiation of electronically excited radicals OH• (λ = 302 nm), CH• (λ = 427 nm, and molecular carbon (λ = 553 nm) are analyzed. The ignition delay times τign are measured in the temperature range T = 1200–2460 K and pressures p = 4.5–25 atm. The data obtained are compared with the results of other authors. [ABSTRACT FROM AUTHOR]

A new method of efficiently transforming water vapor into hydrogen was investigated by dielectric barrier discharge (DBD) loaded with bamboo carbon bed structured by fibrous material in an argon medium. Hydrogen productivity was measured in three different reactors: a non-loaded DBD (N-DBD), a bamboo carbon (BC) bed DBD (BC-DBD), and a quartz wool (QW)-loaded BC DBD (QC-DBD). The effects of the quality ratio of BC to QW and relative humidity on hydrogen productivity were also investigated in QC-DBD at various flow rates. The reaction process and mechanism were analyzed by scanning electron microscopy, X-ray photoelectron spectroscopy, N2 physisorption experiments, infrared spectroscopy, and optical emission spectroscopy. A new reaction pathway was developed by loading BC into the fibrous structured material to activate the reaction molecules and capture the O-containing groups in the DBD reactor. A hydrogen productivity of 17.3 g/kWh was achieved at an applied voltage of 5 kV, flow rate of 4 L/min, and 100% relative humidity (RH) in the QC-DBD with a quality ratio of BC to QW of 3.0. [ABSTRACT FROM AUTHOR]

To improve the phenomenon of serious power consumption of a ladle furnace, the impact of argon flow rate on power consumption in the refining process is investigated through theoretical calculations based on the principle of alternating current measurement using Rogowski coil and integrator circuit. The study divides the power supply phase into four distinct flow rate regions in a single furnace of DH36 steel, a low‐alloy, high‐strength ship plate steel commonly used in shipbuilding and offshore platforms. The analysis of active power, current, and voltage trends, along with average power consumption per second at each flow rate region, reveals a potential for efficient reduction in power consumption. Additionally, experiments with different argon flow rates (300, 400, and 500 NL min−1) during the power supply stages of multifurnace argon tests of AB/A steel show improvements in desulfurization rate, heating rate, processing time, and power consumption per ton of steel heated by 1 °C and power consumption per ton of steel per second. [ABSTRACT FROM AUTHOR]