Presence Of Argon Research Articles

Effect of substrate temperature and position on properties of Cu3N thin films deposited by reactive radio frequency magnetron sputtering

Copper nitride (Cu3N) thin films were deposited on soda lime glass (SLG) substrates by reactive radio frequency (RF) magnetron sputtering using a pure Cu target in the presence of argon and nitrogen. The structural, optical, and electrical properties of the Cu3N films were investigated systematically on substrate temperature and position, demonstrating that both parameters strongly influence the properties of Cu3N thin films. XRD patterns revealed the formation of the Cu3N phase at all substrate temperatures and positions. The transmittance of the Cu3N thin films was over 80 % in the transparent region and the band gap for Cu3N was determined to 1.7–1.9 eV with a very high absorption coefficient above 104 cm−1. The n-type conductivity was observed in every Cu3N film but the resistivity varied considerably with both substrate temperature and position. The promising physical properties of Cu3N thin films suggest their potential application in optoelectronic devices such as thin film solar cells.

Influence of design and annealing parameters on measurements of AC properties of NiFe-SiO2 multilayer structures

In this article, due to the exceptionally interesting electrical and magnetic properties of nanocomposites, which include ferromagnetic materials in a dielectric matrix, multilayer NiFe-SiO2 nanocomposites were obtained. The entire sequence of technological processes using magnetron sputtering equipment in the presence of argon was presented, the aim of which was to create structures with different numbers and thicknesses of layers, as well as in two measurement configurations. Measurements of AC electrical properties were carried out in a variable temperature range, i.e. from room temperature to 373 K, using the 4-point method. The obtained measurement results were compared in terms of design parameters, such as thickness and number of layers, as well as technological parameters, such as heating duration. Structural analysis was performed using scanning electron microscopy (SEM) to investigate the effect of oxidation on the multilayer structures and to confirm the granular structure of the nanocomposite. Additionally, the chemical composition of the obtained multilayers was examined using Energy-dispersive X-ray spectroscopy (EDX). Resistive parameters were tested in the range of magnetic field induction from 0 T to 0.3 T. Based on the conductivity relationships, it was proven that a hopping mechanism of current conduction occurs in the tested samples. Using the frequency dependencies of the phase shift angle, it is possible to adjust the equivalent RC electronic circuit, thereby determining the potential application of the tested materials.

Numerical analysis of sodium-argon two-phase flow in narrow channels under severe accident conditions in pool type SFR

A two-phase flow model for sodium-argon mixture flow through the reactor vessel head penetrations under the energetic core disruptive accident in a sodium fast reactor (SFR) is presented. The model evaluates the total sodium mass in sodium-argon mixture released to the reactor containment building (RCB) through penetrations. The driving pressure at the penetration entrance is given as input. The two-phase frictional and local pressure drops, inertial and piezo-metric heads are accounted for in the model. Depending on the argon volume fraction, either a homogenous or separated flow approach is adopted to evaluate the mixture flow. Reactor-scale analysis show that the presence of argon in vessel head penetrations can significantly mitigate the total sodium release mass during the slug impact phase. Also, the two-phase frictional pressure drop plays a mitigating role and needs to be included in the model formulation to avoid overestimation of the sodium release mass. Fluid-structure interaction effects such as vessel head bending and hold-down bolt elongation have negligible influence on sodium release mass as long as the deformations are within the elastic limit. The model is conceived to be part of an integrated code system to evaluate the sodium fire and the maximum RCB pressure under severe accident conditions in a pool-type SFR.

Charge-Transfer Spectroscopy of Ag+(Benzene) and Ag+(Toluene).

Gas-phase ion-molecule complexes of silver cation with benzene or toluene are produced via laser vaporization in a pulsed supersonic expansion. These ions are mass-selected and photodissociated with tunable UV-visible lasers. In both cases, photodissociation produces the organic cation as the only fragment via a metal-to-ligand charge-transfer process. The wavelength dependence of the photodissociation produces electronic spectra of the charge-transfer process. Broad structureless spectra result from excitation to the repulsive wall of the charge-transfer excited states. Additional transitions are detected correlating to the forbidden 1S → 1D silver cation-based atomic resonance and to the HOMO-LUMO excitation on the benzene or toluene ligand. Transitions to these states produce the same molecular cation photofragments produced in the charge-transfer transitions, indicating an unanticipated excited-state curve-crossing mechanism. Spectra measured for these ions are compared to those for ions tagged with argon atoms. The presence of argon causes a significant shift on the energetic positions of these electronic transitions for both Ag+(benzene) and Ag+(toluene).

X-ray photoelectron spectroscopy (XPS) study of surface oxidation of UO2 doped with Gd2O3 at different temperatures and atmospheres

In this work, the influence of GdIII doping on the surface oxidation of UO2 has been investigated in situ by XPS. The samples were put in contact with either hydrogen, argon or synthetic air streams saturated with water and were heated at different temperatures (60, 200 and 350 °C). The results indicated that, in absence of porosity, doping UO2 with Gd2O3 completely inhibited the oxidation of UO2. Such behaviour could be explained by the matrix stabilization effect of gadolinia (Gd2O3). However, for porous samples, the oxidation of UO2 in presence of Gd2O3 depends strongly on the surrounding gas atmosphere. In presence of hydrogen, the oxidation was significantly supressed, particularly above 200 °C, due to the hydrogen reducing effect. At 350 °C and in the presence of argon, the reactivity of the samples increased slightly when comparing to H2, whereas in contact with synthetic air, the complete oxidation of the samples could not be prevented by Gd2O3. These results could be explained by assuming that the porosity might favour the oxidation of the samples. Therefore, the presence of porosity in the samples is an important parameter to consider when studying the surface oxidation of UO2 doped with Gd2O3.

Homogeneous water nucleation in argon, nitrogen, and nitrous oxide as carrier gases.

Experimental results for homogeneous nucleation of water droplets in the presence of argon, nitrogen, and, for the first time, nitrous oxide as carrier gases are reported. The main objective of the study was to investigate the effects of different carrier gases on the nucleation rate. These gases differ in the number of atoms comprising the molecule, which affects the expansion ratio required to reach the target nucleation temperature. The experiments cover nucleation temperatures from 220 to 260K, nucleation pressures from 40 to 73kPa, supersaturations of 6.5-20, and nucleation rates ranging from about 4 × 105 to 4 × 109cm-3s-1. The new data obtained with a modernized expansion chamber utilizing the nucleation pulse method show good agreement with the available literature data. Another important point of our work is the application of real gas corrections to calculate the nucleation temperature and supersaturation. The results show that the influence of carrier gases on nucleation rate in the investigated pressure range is modest (less than a factor of 7), while without the real gas correction, the apparent effect of carrier gas is significant, with differences as high as a factor of 90.

The wet preparation and dehydration of terbium fluoride salt for terbium metal processing

Terbium fluoride hydrate (TbF3.nH2O) was prepared from the terbium chloride (TbCl3) solution using ammonium bicarbonate (NH4HCO3) and hydrofluoric acid (HF) as precipitate reagents. The dehydration of TbF3.nH2O was carried out in a tube furnace in the presence of argon. The influential factors on the production process have been studied. Thermal analysis techniques were applied to determine the temperature range for dehydration. The obtained TbF3 products were assessed by X-ray diffraction, Scanning electron microscopy, and Energy dispersive X-ray spectroscopy methods. The results showed that anhydrous TbF3 with a particle size of 200-700 nm can be used as a material to prepare terbium metal.

Design of new process for stabilization of LaxGd1-xB6 nanorods and their Field Emission properties

Among all the rare earth metal hexaboride, GdB6 shows the lowest work function of 1.5 eV, which makes GdB6 a promising field emitting material. In the present work, synthesis of LaxGd1-xB6 (x = 0.1, 0.2, 0.3, 0.4 and 0.5) was attempted via borothermal reaction of LaxGd1-x(OH)3 nanorods and sodium borohydride at 1000 °C. The synthesis of ultrafine nanorods of LaxGd1-x(OH)3 (x = 0.1, 0.2, 0.3, 0.4 and 0.5) has been attempted via the hydrothermal route. The LaxGd1-x(OH)3 is annealed with NaBH4 in presence of argon, which leads to the formation of LaxGd1-xB6. TEM study of LaxGd1-xB6 indicates the nanorods formation of diameter 30–40 nm and length 130 nm. Further, as-synthesised LaxGd1-xB6 sample has been spin-coated over the silicon substrate and deposited LaxGd1-xB6 film was used for the field emission study. The field emission study shows the lowest turn-on field for LaxGd1-xB6 (x = 0.5) which is 5.01 V/μm with the highest field enhancement factor (β = 1568).

Development of deposition technology and AC measurement of copper ultrathin layers

In this paper, the transport properties of discontinuous 4 nm copper layers obtained by dual-source non-reactive magnetron sputtering in the presence of argon are presented. The value of resistance and capacitance of the current parallel to the plane of these layers can be adjusted independently by changing the nominal thickness of the metallization. The influence of frequency on the conductivity of the obtained structures in the range from 4 Hz to 8 MHz was studied. Additionally, in order to compare the non-oxidized and oxidized layers, some of them were heated at 500 °C. Based on the results obtained, the mechanism of electric charge transfer was determined, the knowledge of which is essential for planning further experiments based on this sputtering method and potential selection of future application of the structures. Statistical measurements at room temperature will serve as a reference for the conductivity and resistivity values obtained by mathematical calculations from measurements of resistance, capacitance, phase shift angle, and dielectric loss tangent as a function of temperature from 20 K to 375 K, which are expected in further studies on the obtained structures. The work is an introduction to the technology of obtaining multi-layer metal-dielectric structures.

Effect of low‐pressure cold plasma on the properties of edible film based on alginate enriched with Dunaliella salina powder

AbstractEdible films based on sodium alginate enriched with different percentages of Dunaliella salina powder were prepared and treated by cold plasma for diverse durations in the presence of oxygen and argon. The results demonstrated that plasma treatment, especially in the presence of argon, improves film tensile strength and Young's modulus but reduces its flexibility. Surface morphologies and topography clearly show that cold plasma's physical and chemical etching affected the microstructure of films and increased surface roughness and contact angle. Also, water vapor permeability decreased due to the reduced pores of the film and surface hydrophilicity after treatment. The results of total phenolic content and antioxidant activity of treated films containing D. salina were interestingly increased by both O2 and Ar plasma. The colorimetric findings indicated that plasma increased the intensity of redness in samples containing D. salina, with the color of these samples being more vivid.

Optical and magnetic properties of cobalt doped TiN thin films grown by RF/DC magnetron sputtering

Here we report the study of cobalt doped titanium nitride thin films grown by reactive co-sputtering of cobalt and titanium targets in the presence of argon and nitrogen gases. Thin films were grown with different cobalt concentrations and analyzed by atomic force microscopy, spectrophotometry, X-ray photoelectron spectroscopy, X-ray reflectometry and vibrating sample magnetometry. We have found that the films readily oxidize after exposure to the atmosphere and form a cobalt doped titanium oxynitride. The variable cobalt concentration in the films affects the optical, chemical and magnetic properties. The bandgap of the films generally becomes narrower at higher cobalt concentrations. Cobalt is found to be in a mixture of the high spin + 2 and low spin + 3 oxidation states. At the lower cobalt concentrations, the magnetization is low and it is temperature-independent. Whereas at higher cobalt concentrations, the magnetic response becomes temperature-dependent with a mix of paramagnetism and superparamagnetism at 3–5 K.

Influence of sugarcane bagasse addition in co-pyrolysis with sewage sludge on the thermogravimetric characteristics and study of kinetic

To evaluate the influence of sugarcane bagasse in co-pyrolysis with sewage sludge, thermogravimetric analysis (TGA) in the presence of argon was studied. Pyrolysis experiments were carried out for sewage sludge (SS), sugarcane bagasse (SCB), and SS/SCB mixtures (1:1 mass ratio) in the temperature range of 30–800 °C at a heating rate of 10 °C per minute. Kinetic analysis was determined by using the Arrhenius equation and showed a change in activation energy, i.e., 27–52 kJ/mol, 29–46 kJ/mol, and 20–32 kJ/mol in the three stages of temperature ranges for SS, SCB and those for SS/SCB mixtures, respectively. The behavior of material degradation is attributed to this variation of activation energy. In contrast to pyrolysis of only-SS, co-pyrolysis mixtures (SS/SCB) offer improvement in the highest rate of degradation by 55%, the shift of peak temperature to lower value by 2–13%, reduced quantity of residue left behind by 56%, and alteration in activation energy by −60 to +36% suggest a synergism upon addition of SCB in SS.

Detailed dynamics of direct three-body recombination of singly charged ions.

We consider the main aspects of detailed dynamics of the reactions of direct three-body ion-ion recombination Cs+ + X- + R → CsX + R (X- = F-, I- and R = Ar, Xe) for non-central encounters of the ions. The reactions are simulated by the quasiclassical trajectory method using diabatic semiempirical potential energy surfaces proposed previously. The recombination mechanisms are studied via visualization of randomly selected trajectories for each of the four systems. Comparison of trajectories for different systems with identical sets of initial conditions is carried out. For most of the presented trajectories, the ion encounter energy and the third body energy are equal to 1 eV. The characteristic function of recombination is defined, this function depends on 13 arguments including eight kinematic parameters. It is shown that the transfer of excess energy from the ion pair to the neutral atom can occur, in particular, via an encounter of the R atom with the Cs+ ion, via an encounter of the R atom with the X- ion, or via successive encounters of the R atom with both the ions, as well as via an "insertion" of the R atom between the ions.

Properties of Ti-oxide thin films grown in reactive magnetron sputtering with self-heating target

Titanium dioxide thin films have been synthetized by magnetron sputtering in two configurations: using a classical cooled target (cold configuration) or allowing the target temperature to rise under ion bombardment (hot target configuration). In hot configuration, the heated target emits radiations (especially infrared ones) which affect the thin film growth. The target is pure titanium sputtered in presence of argon and dioxygen gases. The crystalline quality, morphology and structure of thin films have been studied on two substrates: thermally grown SiO2 (500 nm)/Si and c-cut sapphire. X-ray diffraction analyses revealed that anatase phase is mainly obtained in both configurations. Texture factors evidenced different main orientations: in cold target the anatase (004) peak tends to be preferred, whereas when a hot target is used, the (112) family plane is furthered. Microscopy analyses showed that the morphology changed depending on the configuration, which could be attributed to an increase of the adatom mobility at the substrate when the target is hot. Optical transmission measurements performed on titanium dioxide thin films deposited onto sapphire substrates showed that optical band gaps may be tuned depending on the configuration used during deposition.

Measurement of Donor-Acceptor Interchange Tunnelling in Ar(H2O)2 using Rotational Spectroscopy and a Re-look at Its Structure and Bonding

In this work, we have measured the donor-acceptor interchange tunnelling splitting in the ground vibrational state of Ar(H2O)2. In the previous investigations, the donor-acceptor tunnelling splitting in fully deuterated species, Ar(D2O)2, was measured to be about 106 MHz. It could not be measured for Ar(H2O)2, as the splitting was expected to be several GHz. Besides, for (D2O)2, both A1 and B1 states have non-zero statistical weight appearing on both sides of the E1 state, having a semi-rigid rotor type spectrum making their observation easier, compared to that of (H2O)2, which has zero statistical weight for the B1 state. With the help of a fourfold periodic potential, we have accurately predicted the fingerprints of b-dipole A1+↔A1- transitions and observed them using a pulsed nozzle Fourier transform microwave spectrometer. Measurement of these transitions enabled us to determine the donor-acceptor tunnelling splitting of 4257.41(4) MHz in Ar(H2O)2. More detailed structural parameters of Ar(H2O)2 have been evaluated in this work and critically compared with (H2O)2. Atoms in Molecules (AIM), non-covalent interactions (NCI) index and natural bond orbital (NBO) analysis have also been carried out for both (H2O)2 and Ar(H2O)2, and these calculations confirm that the presence of argon (Ar) does not affect the structure and bonding in (H2O)2.

A direct dc arc emission spectrometry determination of chlorine impurities in nuclear grade graphite

In the present study, the direct current arc atomic emission spectrometry (dc arc AES) method was proposed for direct determination of chlorine impurities in nuclear-grade graphites and graphite foils in the range of 1‐–100 ppm in order to meet nuclear power industry requirements. The procedure is based on near-infrared (NIR) AES approach for determination of non-metal impurities, contrary to the most common vacuum ultraviolet AES approach. Carbon dc arc in argon atmosphere was used as radiation source. This radiation source employs standard extra high purity 6 mm diameter standard shaped graphite electrodes and standard vertical spectroanalytic stand, but employs several improvements as well: special protective fused quartz tube, and specially built fiber optic refocuser. Registration of spectra was performed via a novel compact tunable spectrometer with linear complementary metal oxide semiconductor array (CMOS) detector. As the work in near-infrared spectral range is hampered by spectral interference factors, measures were taken to counter them. Due to specifics of the radiation source, the excitability of chlorine was studied both in air and argon in presence of carbon, as well as in its absence. Artificial standards for calibration of the spectrometer were prepared by mixing extra high purity NaCl and graphite powder and evaluated by two independent approaches: indirectly by dc arc AES determination of Na, and directly by water extraction and photometrical determination of Cl. The characteristics of evaporation and excitation in dc arc of chlorine from both standards and real nuclear graphite samples were studied due to the differences in the nature of chlorine source in them. The detection limit of was determined 0.8 μg/g. The whole cycle of measurement, including sample preparation is about 10 min.

Plasma-Induced Catalytic Conversion of Nitrogen and Hydrogen to Ammonia over Zeolitic Imidazolate Frameworks ZIF-8 and ZIF-67.

Microporous crystals have emerged as highly appealing catalytic materials for the plasma catalytic synthesis of ammonia. Herein, we demonstrate that zeolitic imidazolate frameworks (ZIFs) can be employed as efficient catalysts for the cold plasma ammonia synthesis using an atmospheric dielectric barrier discharge reactor. We studied two prototypical ZIFs denoted as ZIF-8 and ZIF-67, with a uniform window pore aperture of 3.4 Å. The resultant ZIFs displayed ammonia synthesis rates as high as 42.16 μmol NH3/min gcat. ZIF-8 displayed remarkable stability upon recycling. The dipole-dipole interactions between the polar ammonia molecules and the polar walls of the studied ZIFs led to relatively low ammonia uptakes, low storage capacity, and high observed ammonia synthesis rates. Both ZIFs outperform other microporous crystals including zeolites and conventional oxides in terms of ammonia production. Furthermore, we demonstrate that the addition of argon to the reactor chamber can be an effective strategy to improve the plasma environment. Specifically, the presence of argon helped to improve the plasma uniformity, making the reaction system more energy efficient by operating at a low specific energy input range allowing abundant formation of nitrogen vibrational species.

Effect of thermal annealing on the optoelectronic properties of Cu-Fe-O thin films deposited by reactive magnetron co-sputtering

In this work, the influences of the temperature and the air residual pressure during post-annealing treatment on the structural, optical and electrical properties of copper iron oxide thin films were investigated. The films were co-sputtered from metallic Cu and Fe targets in the presence of argon and oxygen gas mixture. The powers dissipated on the metallic targets were adjusted to fix the Cu/Fe metallic ratio close to 1 in the films. The as-deposited thin films were initially amorphous, and they were annealed under different oxidizing conditions as a function of the temperatures (380, 450 and 550°C) and of the air residual pressures (secondary vacuum, primary vacuum, and air atmosphere corresponding to the air residual pressures of 10−4, 10−1 and 105 Pa respectively). Spinel CuFe2O4 were clearly detected by X-ray diffraction analysis after air-annealing. With the diminishing of the air residual pressure, the films are reduced. It was shown that the delafossite CuFeO2 phase growth is possible in a limited range of temperature and pressure and is accompanied by the crystallization of phase mixture in which the nature of secondary phases depends on the air residual pressure. The optical and electrical properties of Cu-Fe-O thin films were then detailed and discussed according to the structural evolution with the treatment conditions.

Optimized cerium addition for microstructure and mechanical properties of SAC305

PurposeThis paper aims to analyze the effect of cerium addition on the microstructure and the mechanical properties of Tin-Silver-Copper (SAC) alloy. The mechanical properties and refined microstructure of a solder joint are vital for the reliability and performance of electronics. SAC305 alloys are potential choices to use as lead-free solders because of their good properties as compared to the conventional Tin-Lead solder alloys. However, the presence of bulk intermetallic compounds (IMCs) in the microstructure of SAC305 alloys affects their overall performance. Therefore, addition of cerium restrains the growth of IMCs and refines the microstructure, hence improving the mechanical performance.Design/methodology/approachSAC305 alloy is doped with various composition of xCerium (x = 0.15, 0.35, 0.55, 0.75, 0.95) % by weight. Pure elements in powdered form were melted in the presence of argon with periodic stirring to ensure a uniform melted alloy. The molten alloy is then poured into a pre-heated die to obtain a tensile specimen. The yield strength and universal tensile strength were determined using a fixed strain rate of 10 mm per minute or 0.1667 mm s^(−1). The IMCs are identified using X-ray diffraction, whereas the elemental phase composition and microstructure evolution are, respectively, examined by using electron dispersive spectroscopy and scanning electron microscopy.FindingsImprovement in the microstructure and mechanical properties is observed with 0.15% of cerium additions. The tensile test also showed that SAC305-0.15% cerium exhibits more stress-bearing capacity than other compositions. The 0.75% cerium doped alloy indicated some improvement because of a decrease in fracture dislocation regions, but microstructure refinement and the arrangement of IMCs are not those of 0.15% Ce. Different phases of Cu_6 Sn_5, Ag_3 Sn and CeSn_3 and ß-Sn are identified. Therefore, the addition of cerium in lower concentrations and presence of Ce-Sn IMCs improved the grain boundary structure and resulted refinement in the microstructure of the alloy, as well as an enhancement in the mechanical properties.Originality/valueCharacterization of microstructure and evaluation of mechanical properties are carried out to investigate the different composition of SAC305-xCerium alloys. Finally, an optimized cerium composition is selected for solder joint in electronics.

Hydrogen Reduction of MoF6 and Molybdenum Carbide Formation in RF Inductively Coupled Low-Pressure Discharge: Experiment and Equilibrium Thermodynamics Consideration

The physical plasma parameters, temperature and electron number density, are studied in the RF-IC (RF inductively coupled) discharge at a reduced pressure of 3 Torr in mixtures of MoF6 with Ar, H2 and CH4. The emission spectra of mixtures are investigated. It is shown that in the presence of argon, the concentration of free electrons in plasma and dissociation rate of MoF6 increase. A main role of molecular hydrogen is the generation of atomic hydrogen that binds atomic fluorine and leads to the formation of gaseous and solid products. Exhaust gas mixtures exiting the reactor are analyzed by mass spectrometry. It is shown that for all cases, the conversion of MoF6 into reaction products is close to 100%. A thermodynamic analysis of the equilibrium composition of MoF6 systems with Ar, H2 and CH4 was carried out and the obtained results are in good agreement with experimentally observed composition of the solid and gas phases. Analysis of solid deposits from mixture MoF6/H2/Ar revealed the presence of molybdenum powder and large amount of amorphous MoFx. The deposit obtained from mixtures with methane, MoF6/H2/Ar/CH4, contained crystalline molybdenum carbide, Mo3C2.