Argon Ratio Research Articles

Influence of oxygen and argon ratio on electrical and physical characteristics of ZrxHf1–xO2- based MOS devices

Influence of oxygen and argon ratio on electrical and physical characteristics of ZrxHf1–xO2- based MOS devices

Controllable Wetting Modification of Polypropylene Fibrous Mats

In this study, polypropylene (PP) fibrous mats are modified by plasma treatment, following by chemical grafting. Initially, the as-prepared PP fibrous mats are treated by plasma at different oxygen (O2) and argon (Ar) ratios. Then, the PP fibrous mats are modified by grafting dopamine onto polar groups for in situ polymerizations, resulting in a polydopamine (PDA) coating on the substrate's surface. Time-sensitive wettability is thereby converted into permanent wettability in PP fibers. The morphology, chemical performance, and relative wettability of the modified PP fibers are then characterized. The experimental results show, using an O2/Ar ratio of 3:7 during plasma treatment, that the water contact angle was decreased from 114.2° to 0°, and the maximum grafting degree was 0.79%.

Structure and properties of TiN–Pb composite coatings deposited on VT6 alloy by DC magnetron sputtering

DC reactive magnetron sputtering of two separate single-element Ti and Pb targets was used to deposit a TiN–Pb composite coating onto a substrate made of the VT6 titanium alloy. The studies were carried out at Pb cathode currents of 0.2 and 0.1 A and two fixed argon flow rate values of 6.0 or 8.5 cm3/min, and the flow rate of nitrogen supplied to the chamber varying from experiment to experiment. The composition of coatings was determined by energy dispersive analysis. It was shown that the amount of lead in the coatings ranged from 0.5 to 16 wt.% depending on the Pb cathode current and reactive nitrogen consumption. Coating microhardness and wear were determined for each deposition mode. It was found that coating thicknesses varied from 1.9 to 5.2 μm depending on the ratio of argon and nitrogen fluxes. The effect of TiN–Pb magnetron coating deposition parameters on the structure and phase composition was investigated by X-ray diffraction method. It was shown that the coating consists of Pb and PbO at the Pb cathode current of 0.2 A, and of TiN, Pb, and PbO at the current of 0.1 A, while an increase in the ratio of argon and nitrogen fluxes leads to an increase in the fraction of TiN, the intensity of titanium substrate surface saturation with nitrogen, as well as microhardness and wear resistance. Under all deposition conditions the TiN coating features by a typical texture (111), the intensity of which varies nonmonotonically.

Effects of the Ethyne Flow Ratio on Structures and Mechanical Properties of Reactive High Power Impulse Magnetron Sputtering Deposited Chromium-Carbon Films

Chromium-carbon films were deposited by utilizing reactive high-power impulse magnetron sputtering with different mixture ratios of ethyne and argon with a constant deposition total pressure while the deposition temperature, pulse frequency, duty cycle and average power of the chromium cathode remain the same. The microstructure and chemical bonding of the obtained films within different composition were compared. The results show that with the increasing ethyne ratio, the carbon content in films increases linearly with two slopes. Moreover, the microstructure of the deposited film changes from a dense glassy structure into a columnar structure, even a clusters structure. The sp2-C bonding in films decreases but the Cr–C bonding increases with decreasing the ethyne ratio. This reveals the main phase of films changes from a hydrogenated amorphous carbon phase into a glassy amorphous chromium carbide phase. Such changes of the microstructure and phase cause a large difference on the film hardness and elasticity.

A study on autoignition characteristics of H2-O2 mixtures with diluents of Ar/N2 in rapid compression machine for argon power cycle engines

The autoignition features of H2-O2 are crucial for Argon Power Cycle (APC) engines to understand the abnormal combustion in spark-ignition mode and to realize stable ignition in compression-ignition mode. A well-validated H2-O2 mechanism is a cornerstone to all hydrocarbon reaction kinetics emphasizing its importance in fundamental research. Here measurements of the ignition delay times of H2-O2 mixtures have been conducted in a rapid compression machine at 1.0, 3.0, and 5.0 MPa, 903 ~ 1042 K, with excess oxygen ratio of 1.0, 2.0, and 4.0, dilution ratio of 70%, 80%, and 90%, with argon ratio in the diluent of 50%, 60%, 70%, and 75%. 394 data points and 85 data sets were consequently obtained. A comprehensive comparison between 17 selected literature mechanisms was then performed. Results show that the ignition delay time of H2 is very sensitive to the temperature, especially near the ignition limit. The argon ratio in the diluent has a remarkable effect on the ignition delay. High pressure accelerates the autoignition, while both a high dilution ratio and a high excess oxygen ratio inhibit the autoignition. This research work suggests that a combination of highly diluted and ultra-lean combustion may inhibit knock in APC engines. H + O2 (+M) = HO2 (+M) and H + O2 = O + OH are the most sensitive reactions at 1.0 MPa over 950 K, while 2OH (+M) = H2O2 (+M) and H + H2O2 = H2 + HO2 are the most sensitive reactions at both 3.0 and 5.0 MPa.

Application of surface acoustic wave to enhance the photocatalytic degradation efficiency of methylene blue

The TiO2 thin film was grown on a [Formula: see text] Y-axis cut, X-axis propagation lithium niobate substrate by radio frequency magnetron sputtering to fabricate a surface acoustic wave device. The sputtering ratios of argon to oxygen at 20% and post-annealing temperature at [Formula: see text]C for 3 h were controlled to improve the photocatalytic activity of TiO2 thin film. The effects of work frequency and input voltage of the surface acoustic wave device on the methylene blue photocatalytic degradation efficiency of the TiO2 thin film were investigated. The TiO2 thin film was vibrated at radio frequency by surface acoustic wave device to increase the scattering and reactive frequency for methylene blue in liquid. The surface acoustic wave device operated at 28.65 MHz work frequency and 0.95 V input voltage revealed the highest photocatalytic degradation efficiency of methylene blue. Compared to the TiO2 thin film combined with and without surface acoustic wave device, the surface acoustic wave device enhanced the TiO2 thin film photocatalytic degradation efficiency to 46%.

Ion dynamics in capacitively coupled argon–xenon discharges

An argon–xenon (Ar/Xe) plasma is used as a model system for complex plasmas. Based on this system, symmetric low-pressure capacitively coupled radiofrequency discharges are examined utilizing particle-in-cell/Monte Carlo collisions simulations. In addition to the simulation, an analytical energy balance model fed with the simulation data is applied to analyze the findings further. This work focuses on investigating the ion dynamics in a plasma with two ion species and a gas mixture as background. By varying the gas composition and driving voltage of the single-frequency discharge, fundamental mechanics of the discharge, such as the evolution of the plasma density and the energy dispersion, are discussed. Thereby, close attention is paid to these measures’ influence on the ion energy distribution functions at the electrode surfaces. The results show that both the gas composition and the driving voltage can significantly impact the ion dynamics. The mixing ratio of argon to xenon allows for shifting the distribution function for one ion species from collisionless to collision dominated. The mixing ratio serves as a control parameter for the ion flux and the impingement energy of ions at the surfaces. Additionally, a synergy effect between the ionization of argon and the ionization of xenon is found and discussed.

Growth of aluminum nitride on a silicon nitride substrate for hybrid photonic circuits

Aluminum nitride (AlN) is an emerging material for integrated quantum photonics with its excellent linear and nonlinear optical properties. In particular, its second-order nonlinear susceptibility χ (2) allows single-photon generation. We have grown AlN thin films on silicon nitride (Si3N4) via reactive DC magnetron sputtering. The thin films have been characterized using x-ray diffraction (XRD), optical reflectometry, atomic force microscopy (AFM), and scanning electron microscopy. The crystalline properties of the thin films have been improved by optimizing the nitrogen to argon ratio and the magnetron DC power of the deposition process. XRD measurements confirm the fabrication of high-quality c-axis oriented AlN films with a full width at half maximum of the rocking curves of 3.9° for 300 nm-thick films. AFM measurements reveal a root mean square surface roughness below 1 nm. The AlN deposition on SiN allows us to fabricate hybrid photonic circuits with a new approach that avoids the challenging patterning of AlN.

Physico-chemical bases and mathematical modeling of degassing processes in out-of-furnace steel processing

The object of research is the processes of vacuum treatment of liquid steel after its release from the steelmaking unit. The purpose of the work is to study the processes of degassing of liquid steel under vacuum and optimize the conditions for reducing the gas saturation of the metal. The research method is the use of a dynamic mathematical model, developed taking into account the provisions of process limitation by diffusion links of the metal - gas phase boundary transfer. Mathematical models of degassing of metal in ladles with argon purge have been developed, taking into account the distribution of gases from metal according to three articles - in CO bubbles, in argon bubbles and through the open surface of the metal. In all variants of change of technological parameters blocking of a considerable part of a surface of a section of a metal - gas phase by a stream of oxygen is observed. This is because oxygen flows are about an order of magnitude higher than hydrogen flows. At change of technological parameters there is a process of self-regulation of redistribution of streams of hydrogen and oxygen. This is primarily due to the large deviation of the reaction of CO formation from equilibrium. When replacing argon in the purge gas with nitrogen, the behavior of CO and hydrogen in the bubbles during vacuum treatment of the metal remains almost the same. The basis of the products of the decarburization reaction is CO. As oxygen is removed from the metal, the CO content in the purge gas bubbles decreases, and due to this, the hydrogen and nitrogen content increases. The content of CO and hydrogen in the bubbles of the purge gas does not depend on the ratio of argon and nitrogen in the vacuum treatment. The optimal ratio of the purge mixture can be changed depending on the grade of steel being smelted. Comparison of calculated and experimental data indicates a fairly high adequacy of the model in kind

Discharge dynamics of a nanosecond pulsed helium/argon nanosecond atmospheric pressure glow discharge

A nanosecond pulsed atmospheric pressure dielectric barrier glow discharge in helium with 1% of argon was studied. The effects of the electric field, frequency, and gas mixture ratio on the temporal behavior of the plasma discharge were captured with an ICCD camera. Special interest was given to the timing and scale of the secondary or return stroke. It was found that the external electric field can control the occurrence of the return stroke in a dielectric barrier discharge. If the electric field is high enough, the return stroke occurs earlier than previously observed in other works. Increasing frequency leads to faster discharge initiation times for both the primary and secondary discharges. Increasing the argon ratio of the mixture leads to an increased intensity of the primary discharge, a decrease in the intensity of the secondary discharge, and a delay in the timing of the primary discharge.

Minimizing film residual stress with in situ OES big data using principal component analysis of deposited AlN films by pulsed DC reactive sputtering

In this study, aluminum nitride (AlN) thin films were deposited on Si (100) and investigated on the minimum film residual stress with varying two critical deposition conditions in N2 gas flow and power. The pulsed DC reactive sputtering of aluminum targets was carried out in gas ratio of nitrogen (N2) and argon (Ar) plasma with N2:Ar ratios from 15:15 to 60:15 and power from 400 to 1000 W. According to the large-scale data of in situ optical emission spectroscopy (OES) study in connection with film microstructure information by analyzing X-ray diffraction (XRD) patterns, scanning electron microscope (SEM) micrographs, transmission electron microscope (TEM) analyses, Fourier-transform infrared spectroscopy (FTIR) spectra, and alpha-step profilers, the deposited film stress states can be highly affected by the critical processing parameters of N2 flow rate and power. In addition, the proposed value of residual stress (VRS) can be calculated by PC1-DEV (the standard deviation in the first principal component direction) method for accurate prediction of the stress states of deposited films, i.e., compressive stress or tensile stress, which will provide valuable information on residual stress characterization as the in situ monitoring tool for the AlN thin film deposition process. In summary, a methodology based on large data of OES by which principal component analysis (PCA) was utilized to reduce its dimension can be used to determine residual stress characterization from a simple measurement in situ plasma monitoring tool is suggested.

High efficiency perovskite solar cells using DC sputtered compact TiO2 electron transport layer

High conductivity and transparency of the electron-transporting layer (ETL) is essential to achieve high efficiency perovskite solar cells (PvSCs). Generally, titanium dioxide (TiO2) has been extensively utilized as an ETL in PvSCs. Both surface roughness and uniformity of the compact-TiO2 (C-TiO2) can influence the efficiency of the PvSC. This work investigates the optimization of the direct current (DC) sputtering power and the ratio of argon (Ar) to oxygen (O2) plasma to achieve high quality ETL films. The effect of changing the DC sputtering power on the C-TiO2 films and subsequently on the overall efficiency was studied. The electrical and optical properties of the C-TiO2 layer were characterized for various DC powers and different ratios of Ar to O2 plasma. It was found that the optimum preparation conditions for the C-TiO2 films were obtained when the DC power was set at 200 W and a flow rate of 6 sccm Ar and 12 sccm O2. A power conversion efficiency (PCE) of 15.3% in forward sweep and 16.7% in reverse sweep were achieved under sunlight simulator of 100 mW/cm2. These results indicate that significant improvement in the efficiency can be achieved, by optimizing the C-TiO2 layer.

Effect of oxygen to argon ratio on the electrical performance of Ta<sub>2</sub>O<sub>5</sub> gate dielectric thin film transistor

Effect of oxygen to argon ratio on the electrical performance of Ta<sub>2</sub>O<sub>5</sub> gate dielectric thin film transistor

Assessing simultaneous effect of Ar/O2 ratio and process pressure on ammonia sensing properties of reactive DC magnetron sputtered SnO2 thin films

Tin Oxide (SnO2) has established itself as excellent receptor in chemiresistive detection of ammonia gas in last two decades. There have been several routes developed to obtain a pristine SnO2 film over this time however, physical vapor deposition remains an attractive route for the same due to the control it provides for the growth and its scalability for industry scale production. In this work, we report on the effect of oxygen and argon ratio at different pressure in sputtering unit on the sensitivity of tin oxide. In particular, our investigation revealed that the device based on SnO2 thin film obtained at an sputtering pressure of 10 mTorr and Ar/O2 ratio of 50/50 possess highest response (~27.97% for 30 ppm of ammonia) at optimal temperature of 220 ℃.

Effect of the Ni2+/Ni3+ Concentration on the Optoelectronical Properties of Lithium-Doped Nickel Oxide Films

Lithium-doped nickel oxide (LNiO) films were prepared through radio-frequency magnetron sputtering. The optoelectronic and structural properties of the LNiO films were investigated with respect to varying ratios of argon–oxygen (Ar/O2) and argon–hydrogen (Ar/H2) reaction gases. The resulting LNiO films were polycrystalline, displaying a NaCl-type structure with a grain orientation in the (111) and (200) directions. An increase in the Ni3+ electron bonding states led to a decrease in the resistivity of the LNiO films under the Ar/O2 reaction gas. Nevertheless, the Ni3+ ions in LNiO films induced brown or black coloration and a decrease in transmittance. The high-transmittance LNiO films were deposited with varying ratios of Ar/H2 as the reaction gas. However, the generation of OH bonds promoted the adsorption of water molecules. The electrons provided by the adsorbed water molecules on the LNiO film reduced the number of Ni3+ ions, and this reaction reduced the carrier concentration and resistivity of the film. Therefore, the LNiO/Ag/LNiO multilayer structure with top and bottom LNiO films deposited with the Ar/H2 reaction gas exhibited impressive resistivity and transmittance.

Numerical and experimental study of an Ar/CO2 plasma in a point-to-plane reactor at atmospheric pressure

The applicability of high voltage electrical discharge to reform Carbon Dioxide (CO2) as an environmental pollutant is a technique extensively proved. By this motive, the study of plasma with pure CO2 or its mixtures with other gases is the current interest.In this work, the physical and technical characteristics of a positive direct-current plasma discharge of an Ar/CO2 mixture in a point-to-plane reactor is experimentally and numerically analyzed, and its dependence on Ar fraction studied.Through the optical emission spectroscopy method, the experiments are performed to analyze the emitted spectra from the plasma discharge of the Ar/CO2 mixture. The rotation, vibration, and excitation temperatures and the electron density are also obtained. It was found that all the temperatures decrease as the argon ratio in the Ar/CO2 mixtures increases.Besides, using a 2D PIC-MCC method, the density of three charged species and excitation temperatures are spatially and temporally computed. At the study conditions, a relatively good experimental/modeling agreement is observed for the density and temperature of electrons. Also, the spatial and temporal variations of electric potential and total current density in the discharge medium are numerically calculated by this model, allow us to know the electric characteristic of the discharge.

The Combined Effect of Squid Pen Chitooligosaccharide and High Voltage Cold Atmospheric Plasma on the Quality of Asian Sea Bass Slices Inoculated with Pseudomonas aeruginosa

The effects of chitooligosaccharide (COS) at different concentrations (0.05, 0.1 and 0.2%, w/w) without and with the application of high voltage cold atmospheric plasma (HVCAP) at different ratios of argon (Ar) and oxygen (O2), 90%Ar/10%O2 and 80%Ar/20%O2 on the growth of Pseudomonas aeruginosa inoculated (6 log CFU/mL) on Asian sea bass slices were monitored for 0 and 24 h incubation at 4ºC. Impact of COS on the changes in lipid and protein oxidation caused by HVCAP was also determined. All the HVCAP treated slices showed reduction in Pseudomonas count (PC) as compared to control (without any treatment) at both 0 and 24 h of incubation (p<0.05). However, decrease in PC was enhanced when HVCAP treated slices were combined with COS, particularly with higher O2 ratio (20%). COS inhibited lipid and protein oxidation of the slices treated with HVCAP as indicated by lower peroxide value, thiobarbituric acid reactive substances (TBARS) and total carbonyl content. For all treated slices, total volatile base nitrogen (TVB-N) was decreased at both incubation times, compared to the control. Micrograph analysis showed perforated, deformed and distorted cells of Pseudomonas after treatment alone or in combination. Therefore, COS could lower microbial load when combined with HVCAP and simultaneously could reduce the adverse impact of both protein and lipid oxidation, in slices treated with HVCAP.

Estimates of net community production from multiple approaches surrounding the spring ice-edge bloom in Baffin Bay

Measurements of net community production (NCP) provide an upper constraint on the strength of the oceanic biological pump, the dominant mechanism for removing CO2 from the ocean surface and sequestering it at depth. In this investigation, our objectives were to describe the spatial and temporal variability of NCP associated with the spring ice-edge bloom in Baffin Bay and to identify the key environmental drivers controlling its variability. Using data collected between June 9 and July 10, 2016, we estimated NCP based on (1) underway measurements of surface water oxygen to argon ratios (O2:Ar), (2) underway measurements of the partial pressure of CO2, and (3) seasonal nitrate drawdown from discrete samples. These multiple approaches displayed high NCP (up to 5.7 mol C m–2) in eastern Baffin Bay, associated with modified Atlantic waters, and low NCP (<1 mol C m–2) in the presence of Arctic outflow waters in western Baffin Bay. Arctic outflow waters were characterized by low surface salinities and nitrate concentrations, suggesting that high freshwater content may have limited the nutrient availability of these waters. Different integration depths and timescales associated with each NCP approach were exploited to understand the temporal progression and succession of the bloom, revealing that the bloom was initiated under ice up to 15 days prior to ice retreat and that a large portion of NCP in eastern Baffin Bay (potentially up to 70%) was driven by primary production occurring below the surface-mixed layer.

Optical and Structural Properties of Titanium Dioxide Papered by DC Magneto-Sputtering as a NO2 Gas Sensor

In this work, a reactive DC magnetron sputtering technique was used to prepare TiO2 thin films. The variation in argon and oxygen gases mixing ratios (4:1, 2:1, 1:1, 1:2, 1:4) was used to achieve optimal properties for gas sensing. In addition, an analysis of the optical XRD properties of TiO2 thin films is presented. High-quality and uniform nanocrystalline films were obtained at a working gas pressure of 0.25 mbar and 1:4 (Ar/O2) gas mixture. The optical properties showed a transparent thin film with uniform adherence to the substrate. The average transmission of the TiO2 films deposited on the glass substrates was higher than 95% over the range of 400 to 800 nm. The optical band gap varied from 3.84 eV to 3.93 eV as a function of oxygen/argon ratios. The XRD pattern showed that the films have an amorphous structure, which is shifted to polycrystalline with increasing oxygen to argon ratio. The sensitivity, response time, and recovery time were measured for TiO2 thin films using NO2 oxidizing gas.

Transient response of an axially-grooved aluminum-ammonia heat pipe with the presence of non-condensable gas

The lifetime of axially-grooved ammonia heat pipes (HP), which are widely used in satellites for temperature homogenization in structural panels can be affected by the generation of non-condensable gas (NCG), causing the gradual deterioration of the HP’s performance. In order to better understand the influence of different quantities of NCG on steady-state and transient HP behavior, a mathematical model was developed and thoroughly explored to simulate the performance of heat pipes with and without the presence of NCG. The model was validated and correlated with experimental results from two identical axially-grooved aluminum-ammonia heat pipes, one without NCG, and the other with 0.014% mass ratio of argon as the NCG. Experiments were conducted under 75 W heat load and with condensation provided by a combination of natural and forced convection cooling. The behavior of the HPs was analyzed numerically and experimentally during start-up and shutdown phases. The results revealed how the presence of NCG distorted the pipe’s temperature profile and how the NCG density distribution behaved at start-up. The proposed method of NCG detection, based on the analysis of temperature change rate, provided a more sensitive detection of small NCG amounts than usual methods of steady-state temperature profile analysis.