Showing papers on "Argon published in 2023"

The importance of laser wavelength for driving inertial confinement fusion targets. II. Target design

Abstract: We describe details of radiation-hydrodynamics simulations of directly driven targets for inertial confinement fusion using laser drivers with different laser wavelengths. Of particular interest here are comparisons of frequency-tripled glass (laser wavelength 351 nm) lasers with the argon fluoride (193 nm) and krypton fluoride (248 nm) excimer lasers and the effects that these laser wavelengths have on the target designs. We explore the effect these drivers have on the compromise involved between lowering laser plasma instabilities (LPIs) or hydrodynamic instabilities while providing high gains and seek to quantify this trade-off. Short-wavelength drivers have significant advantages, primarily in using less power and energy to drive targets. Additionally, they expand the allowed operating regime that is constrained by LPI avoidance and the production of higher pressures needed for more hydrodynamically stable targets. Potential disadvantages to shorter drive wavelengths, such as increased imprint, are examined and found to be unimportant.

Annealing in Argon Universally Upgrades the Na-Storage Performance of Mn-Based Layered Oxide Cathodes by Creating Bulk Oxygen Vacancies.

Abstract: Manganese-rich layered oxide cathodes of sodium-ion batteries (SIBs) are extremely promising for large-scale energy storage owing to their high capacities and cost effectiveness, while the Jahn-Teller (J-T) distortion and low operating potential of Mn redox largely hinder their practical applications. Herein, we reveal that annealing in argon rather than conventional air is a universal strategy to comprehensively upgrade the Na-storage performance of Mn-based oxide cathodes. Bulk oxygen vacancies are introduced via this method, leading to reduced Mn valence, lowered Mn 3d-orbital energy level, and formation of the new-concept Mn domains. As a result, the energy density of the model P2-Na0.75Mg0.25Mn0.75O2 cathode increases by ~50% benefiting from the improved specific capacity and operating potential of Mn redox. The Mn domains can disrupt the cooperative J-T distortion, greatly promoting the cycling stability. This exciting finding opens a new avenue towards high-performance Mn-based oxide cathodes for SIBs.

Characterization of the tribologically relevant cover layers formed on copper in oxygen and oxygen-free conditions

Abstract: Abstract Engineering in vacuum or under a protective atmosphere permits the production of materials, wherever the absence of oxygen is an essential demand for a successful processing. However, very few studies have provided quantitative evidence of the effect of oxidized surfaces to tribological properties. In the current study on 99.99% pure copper, it is revealed that tribo-oxidation and the resulting increased abrasive wear can be suppressed by processing in an extreme high vacuum (XHV) adequate environment. The XHV adequate atmosphere was realized by using a silane-doped shielding gas (1.5 vol% SiH 4 in argon). To analyse the influence of the ambient atmosphere on the tribological and mechanical properties, a ball—disk tribometer and a nanoindenter were used in air, argon, and silane-doped argon atmosphere for temperatures up to 800 °C. Resistance measurements of the resulting coatings were carried out. To characterize the microstructures and the chemical compositions of the samples, the scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) were used. The investigations have revealed a formation of η-Cu 3 Si in silane-doped atmosphere at 300 °C, as well as various intermediate stages of copper silicides. At temperatures above 300 °C, the formation of γ-Cu 5 Si were detected. The formation was linked to an increase in hardness from 1.95 to 5.44 GPa, while the Young’s modulus increased by 46% to 178 GPa, with the significant reduction of the wear volume by a factor of 4.5 and the suppression of further oxidation and susceptibility of chemical wear. In addition, the relevant diffusion processes were identified using molecular dynamics (MD) simulations.

Under-threshold RABBITT in argon

Abstract: The process of reconstruction of attosecond bursts by beating of two-photon transitions (RABBITT) can involve a transition from under the ionization threshold. Such an under-threshold RABBITT (or uRABBITT) was demonstrated experimentally and analyzed theoretically in He and Ne. In the present work, we explore an analogous process in the argon atom. The uRABBITT in Ar reveals the familiar physical effects: a phase transition across the threshold and the symmetry modification of the photoelectron momentum distribution. It can also be used for mapping the electronic structure of the target atom bound states.

Effect of post-annealing on thermal shock and steam corrosion of LaMgAl11O19/Yb2Si2O7 thermal/environmental barrier coatings

Abstract: LaMgAl11O19/Yb2Si2O7 (LMA/YbDS) thermal/environmental barrier coatings (T/EBCs) on SiCf/SiC composites were annealed at 1200 °C for 5 h in air or Ar atmosphere. The effect of post-annealing in different atmospheres on the microstructure, thermal shock and steam corrosion of the LMA/YbDS T/EBCs was investigated. Results indicated heat treatment in air and argon eliminated the amorphous in the coatings, avoiding the aging stress associated with the crystallization. And the argon-annealed layers (LMA and YbDS) exhibited the less elastic moduli than the air-annealed ones, resulting in the lower thermal mismatch stress in the argon-annealed T/EBCs upon subsequent thermal cycling. Thus, the argon-annealed T/EBCs exhibited an improved thermal cycling lifetime than the as-sprayed and the air-annealed ones. In addition, the unbroadened vertical cracks in the argon-annealed LMA-TBC layer limited the reactant (water-vapor) access to the silica-TGO, leading to the greater resistance of the argon-annealed T/EBCs against steam corrosion than the other two systems.

Knock Inhibition in Hydrogen Fueled Argon Power Cycle Engine with a Higher Compression Ratio by Water Direct Injection at Late Exhaust Stroke

Abstract: Hydrogen-fueled Argon Power Cycle engine is a novel concept for high efficiency and zero emissions, which replaces air with argon/oxygen mixtures as working fluid. However, one major challenge is severe knock caused by elevated in-cylinder temperature resulting from high specific heat ratio of Argon. A typical knock-limited compression ratio is around 5.5:1, which limits the thermal efficiency of Argon Power Cycle engines. In this article, preliminary experimental research on the effect of water direct injection at late exhaust stroke is presented at 1000 r/min with IMEP ranging from 0.3~0.6 MPa. Results show that, with temperature-reducing effect of water evaporation, knock is greatly inhibited and the engine can run normally at a higher compression ratio of 9.6:1. Water injected at the exhaust stroke minimizes its reducing effect on the specific heat ratio of the working fluid during the compression and expansion strokes. Thus, the maximum net indicated thermal efficiency reaches 50.32% when Ar/O2 molar ratio is 90:10 and equivalence ratio is 0.38. Besides, the anti-knock capability is most effective with a water injection timing later than 250°CA ATDC. The highest net indicated thermal efficiencies are obtained with water injection timing from 260 to 280°CA ATDC. Additionally, the water produced through combustion and the water needed for injection are in the same order of magnitude, namely tens of milligrams each cycle. Therefore, only a small tank will be needed as a buffer, if water can be separated and collected from the exhaust gas. This paper suggests that water injection is a feasible method for knock inhibition in the Argon Power Cycle engine.

Fabrication of Plasmonic Indium Tin Oxide Nanoparticles by Means of a Gas Aggregation Cluster Source

Abstract: In this work, we demonstrate, for the first time, the possibility to fabricate indium tin oxide nanoparticles (ITO NPs) using a gas aggregation cluster source. A stable and reproducible deposition rate of ITO NPs has been achieved using magnetron sputtering of an In2O3/SnO2 target (90/10 wt %) at an elevated pressure of argon. Remarkably, most of the generated NPs possess a crystalline structure identical to the original target material, which, in combination with their average size of 17 nm, resulted in a localized surface plasmon resonance peak at 1580 nm in the near-infrared region.

Microwave induced plasmas for the analysis of molecular components in incinerator gases

Abstract: The behavior of mols. in different microwave-induced plasmas (MIPs) has been studied by means of optical emission spectroscopy (OES) in order to study if MIP-OES can be used for the anal. of mol. components in incinerator gases. Various mol. species (i.e., N2, CO2, SF6, H2O, and SO2) have been introduced into argon or purely mol. plasmas at both atm. and reduced pressure. Emission from the introduced mols. is only obsd. in the case of nitrogen (emission bands from the first and second pos. system). With other mol. gases, only dissocn. and assocn. products are obsd. (i.e., at. species, CN, C2, CO, OH, NH). The intensities produced by these products has been studied as a function of the pressure, the concn. of introduced mols., and the position in the plasma. Because mainly assocn. products are obsd., anal. of mol. components in incinerator gases with MIP-OES is not a straightforward matter. Moreover, emission from N2, the dominant mol. in incinerator gases, is very intense and extends from 290 to 1000 nm, covering almost this entire spectral range with bands. [on SciFinder (R)]

Effects of post-deposition annealing temperatures in argon ambient on structural, optical, and electrical characteristics of RF magnetron sputtered gallium oxide films

Abstract: Different post-deposition annealing temperatures were carried out in argon ambient to investigate the corresponding effects onto structural, morphological, optical, and electrical characteristics of RF magnetron sputtered gallium oxide (Ga2O3) films. Cubic phase of γ-Ga2O3 was transformed to mixed phases of cubic and monoclinic phases of β-Ga2O3 as the temperature was increased from 400 to 800 °C before became fully β-Ga2O3 phases at 1000 °C. Oxygen vacancies and oxygen interstitials were formed, generating deep energy levels in band gap of the Ga2O3 films. Findings revealed the acquisition of the highest current density in the Ga2O3 film annealed at 400 °C as a consequence of the highest density (J) of dislocation and oxygen vacancies in the film. Nonetheless, the formation of a thicker interfacial layer and location of oxygen vacancies in the film annealed at 1000 °C have caused minute increase in the J surpassing that of 800 °C at a gate voltage greater than 15 V.

Effects of modified argon glow plasma source on PET polymeric surface properties

Abstract: A home-made plasma source with a Langmuir electrical probe was built for this work in order to create a plasma beam that could be utilized successfully in a range of uses. By modifying the operational parameters, including the discharging voltage, cathode-anode spacing, as well as argon (Ar) pressure, a steady discharging media was achieved. Additionally, a locally design electrical probe is introduced into the discharging plasma to monitor the current-voltage (I-V) characteristics curve in order to assign plasma properties. The probe is moved to any intended destination in the plasma volume and has the following dimensions: 1 mm in length, 0.5 mm in diameter. The gas pressure as well as probe-cathode separation are modified to record the plasma characteristics including electron density and electron temperature. As the pressure rises from 0.15 up to 0.3 Torr, it was found that the electron temperature Te varies 4.66*104 to 2.91*104 eV. By subjecting PET polymeric film to Ar plasma beams, its surface wettability is altered. By increasing the plasma period from 0 to 8 minutes, the overall surfaces free energy is raised from 32.2 to 67.7 mJ/m2. Additionally, the developed plasma source is highly efficient and tailored to satisfy the needs of applications like polymeric-surface modifications.

Effect of Argon on CO2 Decomposition in Micro-Slit Sustained Glow Discharge Reactor

Abstract: The microdischarge [Formula: see text] decomposition devices have the advantages of a simple structure and low energy consumption and thus have a very promising future in in-situ resource utilization technology for Mars missions. It was found that the addition of Ar increased the conversion rate of [Formula: see text] in a micro-slit sustained glow discharge reactor. The experimental results showed that the breakdown voltage of Ar was significantly lower than that of [Formula: see text] in the micro-slit discharge, which indicated that the discharge breakdown channel was more likely to be generated. Thus, the addition of Ar to [Formula: see text] resulted in a lower breakdown voltage, and the discharge energy could be more distributed for [Formula: see text] decomposition. Spectral intensity analyses showed that, for [Formula: see text] mixture discharges, the presence of high-energy Ar excited states was clearly observed. With increasing discharge voltage, an increase in the light intensity of active components such as [Formula: see text], O, and CO was observed. Combined with the discharge parameters and spectral characterization, it can be concluded that the metastable species of Ar exist and accumulate during the discharge, which contributes to the conversion of [Formula: see text].

Optical Radiation during Sputtering of Lithium into a Noble Gas Using a Nanosecond Electron Beam

Abstract: The optical radiation in a gaseous medium upon the irradiation of a lithium layer with a fast electron beam of a 5 ns duration has been studied. The irradiation chamber was filled with argon, krypton, or xenon at a pressure of 10 kPa up to 60 kPa. The lines of lithium atoms appear in the emission spectrum at a lithium layer temperature of 650–680 K, and the intensity of these lines sharply increases with the increasing temperature of the lithium layer. The optical radiation arises from both the transitions of noble gas atoms and the transition of the lithium atom in a time of about 20–30 ns. The duration of the radiation pulses at half maximum at temperatures above 800 K was 60–100 ns at a wavelength of 610.4 nm and 140–220 ns at 670.8 nm in krypton and argon. The various mechanisms for the population of lithium levels during the radiation pulse are discussed.

Investigation using Monte-Carlo codes simulations for the impact of temperatures and high pressures on thin films quality

Abstract: The quality of thin films represents the key to any improvement made in the device components manufacturing, and the way to obtain this quality based on deposition parameters takes the attention of our group. In this work, using the sputtering technique in the context of the Monte-Carlo approximation, an investigation of the effect of temperature and elevated pressure on the number of ejected particles and hence their deposition and the creation of finest thin films are applied. A vacuum chamber with 30x30x50 cm in dimension holding a magnetron which has a 2 cm in radius circular target was created. Inside this chamber, 105 particles of Argon (Ar) followed by the same number of xenon (Xe) gas are injected. This target moves away by 15cm from the substrate (with 7 cm in radius), containing three materials (Silicon (Si), germanium (Ge), and copper (Cu)) widely used in advanced technologies as in electronics and photovoltaic cells panels. Evident and satisfactory results were obtained, demonstrating that increasing pressure (0.5, 2, and 5 Pa) for both gases drops off in a spectacular way the total number (with different values) of the material particles reaching the substrate and disrupting the morphology of the thin films. moreover, and contrary to pressure, it has also been proved that mounting gas temperatures of 100, 300, and 600 K, representing three different states in kelvin degrees, where 100 K-173°C for the low (cold), 300 K27°C for the regular (atmospheric) and 600 K327°C for the high (warm) instances, supply a large number of materials atoms in substrate-level which conduct to the finest quality of the thin films. In addition, germanium gives the best results compared to silicon and copper.

Determination of 915-MHz Atmospheric Pressure Air Microwave Plasma Torch (MPT) Parameters

Abstract: The gas temperature, electron temperature, and electron density are critical parameters that affect microwave plasma chemistry processes in industrial applications. Using optical emission spectroscopy (OES), the gas temperature and electron density of a 915-MHz atmospheric pressure air microwave plasma torch (MPT) were investigated at various absorbed power levels and radial positions. In addition, the variation in the electron temperatures of 915-MHz atmospheric pressure argon microwave plasma filaments was analyzed as a function of the absorbed power. The experimental results showed that: 1) the absorbed power had little effect on the radial gas temperature or electron density; 2) the skin effect was present in the 915-MHz atmospheric pressure air MPT, where it causing caused hollowing in the center of the radial gas temperature distribution; 3) the electron density reached approximately $2\times10$ 13 cm−3 and was almost insensitive to variations in the absorbed power in the center of the 915-MHz atmospheric pressure air MPT; and 4) the upper limit of the 915-MHz atmospheric pressure microwave plasma filament electron temperature increased from approximately 1 to approximately 3 eV as the absorbed power increased from 2.0 to 6.3 kW.

Understanding the effect of ambient gas pressure on the nanoparticle formation in electrically exploding wires

Abstract: In this paper, a computational model characterizing the preparation of metallic nanoparticles by electrically exploding wires from the onset of current flowing through the wire to the final moment of nanoparticle formation in a gaseous environment is constructed. The computational model consists of a 1D magnetohydrodynamic model, a simplified magnetohydrodynamic model with two-temperature approximation, and a set of general dynamic equations based on the nodal approach, corresponding to the phase transition stage, plasma evolution stage, and nanoparticle growth stage, respectively. The numerical investigation on the formation of nanoparticles is performed with “cold-start” conditions. The computational predictions for the dependence of nanoparticle size on proportion under argon gas pressure of 10 kPa demonstrate that the nanoparticles of 21 nm in diameter account for the maximum proportion of 4.3%. It coincides with the experimental measurements for nanoparticles of 19 nm in diameter with the maximum proportion of 3.5%. The computational model is employed to reveal the influence of ambient gas pressures on the process of nanoparticle formation. The variation trends for parameters of exploding products, cooling rate, and nanoparticle diameter with the largest proportion on ambient gas pressures are discussed. The size distribution of nanoparticles under different argon gas pressures matches relatively well with relevant experimental data. This computational model bridges the gap between the electrically exploding wires and the growth of nanoparticles, providing theoretical support for the regulation and control technology in nanoparticle synthesization by electrically exploding wires.

Thin films sputter-deposited from EUROFER97 in argon and deuterium atmosphere: Material properties and deuterium retention

Abstract: Sputter-deposited thin films (33–1160 nm) from EUROFER97 were obtained on different substrates (C, Si, W, MgO) in argon and a mix of argon and deuterium atmosphere. The composition, microstructure, and mechanical properties of the films were analyzed and compared to those of the bulk material. The films feature lower density (-10%), higher hardness (+79%), and smaller crystallites in comparison to the bulk. Despite such differences, the elemental atomic composition of the films and the bulk was very similar, as determined by ion beam analysis. Deposition in deuterium-containing atmosphere resulted in a low deuterium incorporation (0.28% of atomic content), indicating low retention of hydrogen-isotopes in the deposited material.

Measurement of isotopic separation of argon with the prototype of the cryogenic distillation plant Aria for dark matter searches

Abstract: The Aria cryogenic distillation plant, located in Sardinia, Italy, is a key component of the DarkSide-20k experimental program for WIMP dark matter searches at the INFN Laboratori Nazionali del Gran Sasso, Italy. Aria is designed to purify the argon, extracted from underground wells in Colorado, USA, and used as the DarkSide-20k tar-get material, to detector-grade quality. In this paper, we report the first measurement of argon isotopic separation by distillation with the 26 m tall Aria prototype. We discuss the measurement of the operating parameters of the column and the observation of the simultane-ous separation of the three stable argon isotopes: 36 Ar, 38 Ar, and 40 Ar. We also provide a detailed comparison of the experimental results with commercial process simulation software. This measurement of isotopic separation of argon is a significant achievement for the project, building on the suc-cess of the initial demonstration of isotopic separation of nitrogen using the same equipment in 2019.