Oxygen Gas Pressure Research Articles

The effect of oxidation on tribology behavior of nickel-graphite coated stainless steel SS420

The main solution to the challenge of maintaining maximum sealing in the compressor section of each gas turbine is the use of abradable coatings. These coatings have a double duty, including (a) maintaining the lagging and (b) protecting the tips of the rotor blades. Choosing the type of abradable coating primarily depends on the service temperature of the coating. Nickel-graphite (Ni-G) coating is a good choice for use up to 480 °C and, or steel/sub-alloy rotor blades. In this research, the Ni-G coating was applied by the flame spraying method of Ni-G powder with a thickness of about 250 μm on an SS420 stainless steel substrate. The effect of the composition of the bonding layer was also investigated using two compositions, Ni-5Al and NiCrAlY. Obtaining the knowledge of applying Ni-G coating by flame spraying, identifying the structural and compositional characteristics of the coating (through optical and electron metallography), and the effect that oxidation can have on the tribological behavior of the coating were among the goals of this project. The best conditions for spraying the Ni-G coating were achieved an oxygen gas pressure of 6 bar, oxygen flow rate of 18 L min−1, acetylene pressure of 1.5 bar, acetylene flow rate of 24 L min−1, and the distance between the gun head and the sample surface was 22 cm. The results showed that placing the coating in oxidizing conditions increases its coefficient of friction. The increase in the coefficient of friction was attributed to the formation of oxide shells on the surface of the coating after 500 h of exposure to oxidation conditions. Corresponding to the higher coefficient of friction, the oxidized coating showed a decrease in wear resistance as a result of oxidation. This result can show the decrease in abradable of this coating with increasing service time.

Corrosion Initiation on Reinforcing Steel with Mill Scale in Mortar

Corrosion of reinforcing steel rebar is the main cause of loss of the long-term reliability of concrete structures. When the rebar is corroded, the rust induces cracks and detachment of the cover concrete. The mill scale, a thick oxide film, is formed on the rebars when the rebar is hot rolled. The role of mill scale on the corrosion resistance of rebars in concrete has not been clarified, yet. This study studied the corrosion behavior of rebars with mill scale in mortar.The samples are commercial rebars with 19 mm diameter, which have a mill scale of several tens of micrometers in thickness. The rebars without mill scale prepared by the electrolytic polishing were used as the comparison samples. A Hyperbaric-oxygen accelerated corrosion test (HOACT) [1] was carried out using the rebars embedded in the mortar with a 5.5 mm cover thickness. To prompt the breakdown of passive film on the rebars, 2.1 M NaCl solution was mixed with the mortar. In the HOACT, pressurized oxygen gas is supplied to the sample, and the oxygen reduction reaction on the steel surface is enhanced, leading to the steel's corrosion acceleration. The oxygen pressure was 0.6 MPa and the test period was 14 days. The corrosion of the rebar with a mill scale was more significant than that without a mill scale. This result shows that the mill scale reduces the corrosion resistance of the steel rebar in concrete [2].To investigate the effect of the mill scale on the corrosion resistance of the rebar, anodic polarization measurements of the rebars with and without the mill scale were carried out in a saturated Ca(OH)2 solution containing Cl-. The pitting potential of the rebar with mill scale was more noble than that of the sample without mill scale. However, when the mill scale was scratched, the pitting potential was significantly shifted to the less noble direction, and it was below that of the rebar without the mill scale. These results show that the mill scale improves the corrosion resistance of the rebar in concrete, in contrast, the corrosion resistance of the rebar with a defective mill scale becomes even worse than that of the rebar without the mill scale [2].[1] K. Doi, S. Hiromoto, H. Katayama, E. Akiyama, J. Electrochem. Soc., 165(9), C582-C589 (2018).[2] K. Doi, S. Hiromoto, T. Shinohara, K. Tsuchiya, H. Katayama, E. Akiyama, Corrosion Science, 177, 108995 (2020).

Enhanced cation ordering, electron-spin-phonon interactions and Fano resonance in half-metallic Sr2FeMoO6 thin films

We report the presence of electron-spin-phonon interactions in half-metallic ferromagnetic Sr2FeMoO6 (SFMO) double perovskite thin films using temperature-dependent Raman spectroscopy. A series of SFMO thin films have been prepared on LaAlO3 (001) single-crystal substrate using the Pulsed Laser Deposition technique. These depositions have been made in different gas-conditions such as in vacuum, and under nitrogen and oxygen gas pressures. At room temperature, Raman spectra manifest a Fano feature which indicates the presence of electron-phonon coupling in the films. The electron-phonon coupling strength further changes with a change in deposition conditions. Magnetization results show that the SFMO film grown in vacuum has the highest saturation magnetization which suggests better cation ordering as compared to the other films. For enhanced understanding, Raman spectra were recorded at varied temperatures and the data were analyzed by theoretical model fittings. A parameter quantifying temperature-dependent anharmonic nature of phonons has been derived using Balkanski model fits. This parameter shows a drastic deviation in the vicinity of Curie temperatures, manifesting a spin-phonon coupling in SFMO films. We further show that the spin-phonon coupling strengthens with improved Fe–Mo ordering. Any experimental observation of spin-phonon coupling has not been reported for SFMO systems till date. The magnetization data corroborate well with these observations made by Raman measurements. Our results of Raman spectroscopy, magnetization and resistivity collectively suggest that the SFMO films exhibit electron-spin-phonon interactions, which are influenced by the cation ordering. We also devised out the method of relating the anharmonic nature of Raman modes with the degree of Fe–Mo ordering and spin-phonon coupling in double-perovskite materials.

Corrosion behavior of Ti–Pt-coated stainless steel for bipolar plates in polymer electrolyte membranes under water electrolysis conditions

In this study, the corrosion behavior and degradation mechanism of Ti–Pt-coated stainless steel bipolar plates were investigated through electrochemical tests and surface analysis in a polymer electrolyte membrane water electrolysis (PEMWE) operating environment. The coated bipolar plate has a corrosion current density of only 1.68 × 10−8 A/cm2, which is an order of magnitude lower than that of the bare SS316L substrate (1.94 × 10−7 A/cm2), indicating that its corrosion resistance is superior to that of bare SS316L substrate. However, in the PEMWE operating environment, the protection efficiency of the coating and the corrosion resistance of the coated bipolar plate decreased. The degradation of the coated bipolar plate can be attributed to electrolyte penetration into the blistering areas of the coating layer with micro voids. Defects in the coating layer occur because of the pressure of oxygen gas generated within the coating layer under high-potential conditions, thereby exposing the substrate to the electrolyte and corrosion.

Influences of preheating parameters on the quality of weld by thermite rail welding

The major goal of this study is to enhance the mechanical and metallurgical characteristics of rail steel grade R260 joined by thermite welding under various preheating conditions, including preheating time and gas pressure. Mainly two conditions, referred to as the Normal Condition and Improved Condition, are carried out for experiments. Prior to welding, the Normal Condition was preheated using liquefied petroleum gas (LPG) and oxygen gas pressures of 1 bar and 4.5 bar for 3 min, and the Improved Condition was preheated using liquefied petroleum gas and oxygen gas pressures of 1.2 bar and 4.5 bar for 6 min and 30 s. To investigate the mechanical and physical properties, micro-Vickers hardness tests, tensile tests and slow bending tests were also carried out. Welded metal in Normal Condition has many defects, including gas holes and shrinkage cavities. When comparing the Normal Condition to the Improved Condition, the Improved Condition demonstrates significantly more bending load and deflection. Specifically, the thermite welded rail sample of Improved Condition demonstrated a remarkable ability to endure bending loads of 108 tonnes and a deflection of 16 mm, and this sample remained unbroken until it exceeded 50% of the standardized deflection limit (10 mm). In addition, the average hardness values for the Improved Condition of the weld metal zone and the heat-affected zone were 331 HV and 289 HV, respectively. The Normal Condition produced an unsatisfactory fracture surface after slow bending test. This was caused by weld defects at the thermite weld due to inappropriate preheating.

Evaluation of Boron Combustion for Ducted Rocket Applications Using Condensed Product Analysis

Boron, a metalloid, produces high energy upon combustion. It is recommended as an ingredient for fuel or propellant in rocket propulsion, despite the challenge of extracting its full thermal energy. So far no one has claimed the complete energy conversion of boron upon combustion. On the other hand, the current propulsion system of the Meteor missile uses boron-loaded propellant. The boron-loaded propellant provides an approximately three-fold increase in specific impulse compared to conventional propellants. The present study focuses on boron-HTPB-based solid fuels impregnated with early ignited particles as additives, aiming to assess the combustion performance of boron particles. These additives are magnesium (Mg), titanium (Ti), and activated charcoal (C), and their effects are evaluated based on the residual active boron content in the condensed combustion products (burned residues). An economical tool commonly called stagnation flow or opposed flow burner (OFB) is used to deflagrate the fuel sample by means of pressurized oxygen gas. The condensed combustion products are examined using a field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential thermal analysis (DTA). Among the fuel combinations investigated here, magnesium has been found to be a good burning enhancer of boron, leaving the lowest active boron content (30%) in the burned-out residue. The current research aims to develop an efficient boron-containing solid fuel for hybrid propellant ducted rocket engine applications.

Switching of n- and p-type doping with partial pressure of oxygen gas on few layers MoS2-field effect transistor

We examined the oxygen adsorption effect on the electric property of the field-effect transistor with an atomic layer MoS2 channel, whose experiment was executed in well-defined ultra-high vacuum conditions and with surface treatment. The threshold voltage change of the Id-Vg curve with the oxygen partial pressure shows n-type doping in the low-pressure range and p-type doping in the high-pressure range. In this report, the Vth vs. oxygen partial pressure uptake curve is well modeled with the Langmuir type adsorption/desorption. The deduced adsorption energy indicates that the adsorbed species are oxygen atoms on the pristine MoS2, suggesting a catalytic behavior of MoS2 for the oxygen reduction reaction. The oxygen adsorption at the S vacant site induces the initial n-type doping. DFT calculation illustrates that, despite the electron transfer from the substrate to the oxygen molecule, the electronic structure change causes the n-type doping.

The effect of O2 pressure on phase formation and superconductivity properties of Tl-based HTS

Thallium-based high-temperature superconductors exhibit excellent superconductivity performance (Tc, Jc). Formation of the Tl-based superconducting materials critically depends on the used precursor and synthesis conditions. In the present investigation, we used the in situ polymerization method for synthesizing high-purity and reaction-ability precursors. We find the critical dependence of Tl-based superconductor phase formation on the quantity of applied oxygen pressure. The experimental results showed that the Tl-1223 phase formed at an oxygen gas pressure at 1 to 2 atm, Tl-2223 phase at 3 atm, and Tl-2212 phase at 4 to 8 atm.

Performance assessment of oxygenated CdS films-based photodetector

CdS films were grown by thermal evaporation on glass substrates. After growth process, samples were oxygenated at 400 °C at various gas pressures for 5 mins employing rapid thermal process. The produced CdS films were used as photodetectors in blue light. X-ray diffraction results revealed that as-deposited CdS films had a wurtzite crystal structure with a satrong preferred orientation along (002) plane. The intensity of (002) peak increased by rising oxygen gas pressure to 2 atm and then decreased with further increase of oxygen gas pressure to 4 atm. Scanning electron microscopy analysis indicated that even though as-deposited CdS thin films included some aligned rod-like grains on an underlaying layer, oxygenation at various gas pressures changed the surface morphology of CdS films. CdS films oxygenated at a gas pressure of 2 atm exhibited the best transmittance value of 80% in the range of 600–1000 nm. It was calculated that band gap increased from 2.42 eV to 2.45 eV as CdS films were oxygenated at a gas pressure of 2 atm. Photoluminescence spectrum of as-deposited CdS films indicated two fundamental peaks located at 530 nm and an interval of 550–700 nm, corresponding to green and deep level emissions, respectively. Consequently, it was attained that CdS films oxygenated at a pressure of 2 atm had the optimized structural, morphological and optical results and therefore, this sample was further employed for photodetecting applications. From photocurrent-time curves, the best photodetecting performance was reached for CdS films-based device oxygenated at a gas pressure of 2 atm including rise time and fall time values of 22 ms and 25 ms, respectively. In addition, the maximum responsivity, detectivity and external quantum efficiency were found to be 23.7 mA/W, 4.75 × 108 Jones and 6.6 for the same photodetector, respectively.

Use of hydroxyapatite powder derived from green mussel shell wastes for coating on AISI 316L

This study aimed to determine the effect of preheating AISI 316L metal substrate on the adhesion strength of the hydroxyapatite (HA) layer derived from green mussel shell waste deposit by the flame spray method. The deposition experiment was carried out in a spray gun with a distance of 10 mm with preheat of 200°C, 400°C, and 600°C. A sample without preheating was also a comparison. An optical microscope was for assessing the thickness and uniformity of the HA surface layer. The adhesion strength of the coatings followed the ASTM D4541 Standard. As a result, the adhesion strength of the HA coating increases with increasing preheat temperature. However, using Image-J software, at an initial heating temperature of 600 °C, the adhesion strength of the coating changed from adhesion- to adhesion-cohesive strength, leading to an increase in coating strength noted. The result can add knowledge to understanding the flame spray method for the HA-coated from green mussel shell waste on AISI 316L. The results obtained can increase knowledge to understand the method of flame spraying on HA-coated green mussel shell waste on AISI 316L. Preheat temperature, spray gun shooting distance, HA powder release, oxygen gas pressure, and LPG gas pressure can be used as references.

Large area planar UV–Visible photodetectors using wide bandgap WO3−δ films

A simple synthesis technique of semiconducting monoclinic phase tungsten oxide (WO3−δ) films is demonstrated. In this article, we report the effect of oxidation temperature on oxygen vacancy gradient of WO3 films and their photo sensing properties. The WO3−δ films were grown on Si/SiO2 substrates by argon ion-beam sputtering of a high purity W (tungsten) target followed by thermal oxidization in the tubular furnace at three different oxidation temperatures at 500, 600 and 700 °C with controlled oxygen gas pressure. Detailed crystal structure, microscopic and spectroscopic characterizations reveal that the oxidation at temperature 700 °C produces reasonably good crystalline quality of the film exhibiting UV–Visible photo sensing properties. The effect of oxidation temperature towards an enhancement in crystallinity which in turn gives rise to sharp Raman peak is discussed. The fabricated device exhibits a very low dark current of 7.5 × 10 −8 A at ±0.5 V bias for WO3−δ films oxidized at 700 °C. The photodetection measurements show linear current-voltage (I–V) behaviour with light-to-dark current (ILight/IDark) ratio ∼102 at 365 nm illumination (∼0.82 mW cm−2) at 2 V applied bias. The responsivity (Rλ), specific detectivity (D*) and external quantum efficiency (EQE) were found to be ∼0.12 AW−1, ∼2.1 × 1010 Jones (cm Hz1/2 W−1) and 40%, respectively, at 365 nm illumination (∼0.82 mW cm−2) with an applied bias of 2 V for the films oxidized at 700 °C. While upon visible light illuminations, the Rλ, D* and EQE were calculated to be ∼0.78 AW−1, ∼1.4 × 1011 Jones and 174%, respectively, upon 555 nm illumination (∼0.21 mW cm−2), with 2 V applied bias. A faster photocurrent relaxation time was observed from the films oxidized at 700 °C. The ultraviolet photoelectron spectroscopy study shows a surface band gap of 3.7 eV with absolutely no density of states in the near Fermi-level, validating fully stoichiometric surface. The effects of oxidation temperatures causing the large bandgap are discussed in terms of the device performances.

Photoelctrochemically Manufactured HgO/Cu2O Monolayer with Ameliorate Photovoltaic Features

This writing report acquaint the chances for promoting efficiency betterment of p-Cu2O electrode for PECs likewise in production of hydrogen gas, using HgO/Cu2O hetero-structure. The arrangement was accomplished by both bracing the surface of p-Cu2O plate embattled through thermal oxidization of copper sheet and also acquiring low cost, effortless and low impairment engineering deposition for utilizing HgO as absorber layer. The altitudinous efficiency of 4.80% and open circuit voltage of 185MV were incurred in an HgO/Cu2O hetero-structure PEC solar cell commence with copper foil thickness (0.1mm) substrate for preparing the Cu2O thin film under oxygen gas pressure at 950℃ by thermal oxidizing techniques. It is requisite to augmented the interface at the hetero-structure junction to accomplished a soaring efficiency in HgO/Cu2O/HgO semiconductor beside multiplicative the parallel resistance and remittent the series resistance.Keywords: thermal oxidation, cuprous oxide, hetero-structure, J-V characteristic, photoelectrochemical, annealing, etching.

The Effect of Oxygen and Air Flow on the Characteristic of Zinc Oxide ZnO Nanorods

In this study, ZnO nanorods are synthesized by the means of chemical bath deposition (CBD). Further objectives, to study the effect of new parameters (oxygen and air flow) on ZnO nanorods on morphology and length of alignment of the nanorods. It was observed that 0.100M for both zinc nitrate hexahydrate and hexamethylenetetramine give a best result. Here, we added an oxygen gas pressure as others idea in chemical bath deposition method and a p-type silicon substrate to investigate the length of ZnO nanorods through their cross-section. It was found that the biggest grain sizes obtain from sample 14, which is 58.87nm produces a high crystal quality, among others. Sample 14 also has a long nanorods (1.434μm-1.451μm) compared to other samples. The hexagonal structure was observed by Field Emission Scanning Electron Microscope, FESEM and well aligned, compact and perpendicular ZnO nanorods grew on the surface of glass substrate. XRD data shows that it has a larger grain size with low lattice strain. The cross-sectional view of the samples demonstrates long nanorods with a range 2.763μm-2.844μm. Finally, the growth of ultra-long ZnO nanorods by using a modified chemical bath setup was successfully observed and recorded.Keywords: ZnO nanorods, CBD, Growth duration, FESEM images, pressure flow.

Aerobic and Anaerobic Sea Water Biodegradation Evaluation by Modified Oxygen (O2) Consumption and Gas Pressure Measurement Technique for Synthetic Gas to Liquid (Gtl), Low Aromatic Synthetic Fluids [Lasf] and Synthetic Ethyl Esters of Plants Oils (Seep Mixture) Drilling Fluids in Deep Water Offshore Environment: Process Variables and Optimization

Aerobic and Anaerobic Sea Water Biodegradation Evaluation by Modified Oxygen (O2) Consumption and Gas Pressure Measurement Technique for Synthetic Gas to Liquid (Gtl), Low Aromatic Synthetic Fluids [Lasf] and Synthetic Ethyl Esters of Plants Oils (Seep Mixture) Drilling Fluids in Deep Water Offshore Environment: Process Variables and Optimization

Aerobic and Anaerobic Sea Water Biodegradation Evaluation by Modified Oxygen (O2) Consumption and Gas Pressure Measurement Technique for Synthetic Gas to Liquid (Gtl), Low Aromatic Synthetic Fluids [Lasf] and Synthetic Ethyl Esters of Plants Oils (Seep Mixture) Drilling Fluids in Deep Water Offshore Environment: Process Variables and Optimization

Aerobic and Anaerobic Sea Water Biodegradation Evaluation by Modified Oxygen (O2) Consumption and Gas Pressure Measurement Technique for Synthetic Gas to Liquid (Gtl), Low Aromatic Synthetic Fluids [Lasf] and Synthetic Ethyl Esters of Plants Oils (Seep Mixture) Drilling Fluids in Deep Water Offshore Environment: Process Variables and Optimization

Switching of N- and P-Type Doping with Partial Pressure of Oxygen Gas on Few Layers Mos2-Field Effect Transistor

Switching of N- and P-Type Doping with Partial Pressure of Oxygen Gas on Few Layers Mos2-Field Effect Transistor

Lattice-strain engineered KxNa1-xNbO3 thin films near the morphotropic phase boundary for enhanced electrical properties

Tailoring of lattice strain by controlling background oxygen gas pressure in PLD deposited K0.5Na0.5NbO3 thin film has been critically investigated. Oxygen gas pressure induced lattice strain significantly influences the structure, morphology, and electrical properties of K0.5Na0.5NbO3 thin films. The in-plane compressive stress and dense micro structured morphology favors superior electrical and ferroelectric properties in the K0.5Na0.5NbO3 film. The film deposited at optimum gas pressure (200 mTorr) exhibited uniformly distributed dense microstructures, low leakage current (6.73 x 10−7 A/cm2 at 150 kV/cm), high saturated and remanent polarization (Ps = 71 μC/cm2 and Pr = 24 μC/cm2, respectively). Besides, a high Curie temperature (Tc = 410 °C), high dielectric constant with low dielectric loss (ε= 1218 and tanδ = 0.18, respectively), and ac conductivity (1 x 10−5 Sm−1) at 1 kHz were obtained for the optimized K0.5Na0.5NbO3 thin film at room temperature.

Explicit formulations of adhesive wear extension in fretting interfaces applying the contact oxygenation concept

Adhesive wear extension in metal fretting contacts was previously related to the partial pressure of oxygen gas in a porous third body layer. Below a threshold value, the surface oxidation is no more possible and adhesive wear prevails in the inner part of the interface. The contact oxygenation concept (COC) allowing the prediction of the dioxygen partial pressure profile was recently simulated for a 2D surface analysis (i.e. 3D contact) using a numerical Advection-Dispersion-Reaction (ADR) approach. In this study, a simple explicit formulation is derived to capture COC response using a 1D surface analysis (i.e. 2D contact hypothesis).

A hierarchical high-throughput first principles investigation on the adhesion work, interfacial energy and tensile strength of NiTi2 (100)/α-Al2O3 (0001) interfaces

By performing a high-throughput first principles calculations on works of adhesion of total 468 different NiTi2/Al2O3 interfaces, eight interfacial configurations (Ni1–O, Ni2–O, Ti1–O, Ti2–O, Ni1–Al2, Ni2–Al1, Ni2–Al2 and Ti2–Al2) belonging to metal–metal and metal–oxygen interfaces are obtained due to their high adhesive strengths. The predicted work of adhesion of metal–oxygen interfaces is higher than 8.80 J/m2, and that value of metal–metal interfaces varies in the range from 2.39 J/m2 to 3.59 J/m2. The interfacial energies of the eight interfaces are obtained at different temperatures (298 K and 1000 K) by varying the chemical potential of oxygen atom. At room temperature, the metal–oxygen interfaces possess the lower interfacial energies and thus the higher thermodynamic stability than those of metal–metal interfaces regardless of the partial pressure of oxygen gas. At high temperature, metal–oxygen interfaces are still favored under O-rich condition, but the metal–metal interfaces are greatly stabilized in case of low oxygen partial pressure. The predicted tensile strengths of metal–oxygen interfaces are all above 10 GPa, and those of for metal–metal interfaces are below this value. For all investigated metal–metal and metal–oxygen NiTi2/Al2O3 interfaces, the mechanical failure is always initiated in the NiTi2 phase proximity to the interface resulted from the breaking of Ni–Ti/Ti–Ti bonds in the first principles tensile test.

Optimization of The Oxy-Acetyline Gas Cutting Process on Aisi 1045 Steel Material to Produce Minimum Width Kerf

This research is intended to determine the optimum combination of parameters and how much the contribution of the parameters of cutting speed, oxygen gas pressure, and nozzle distance to the width of the cutting kerf. This research was conducted with a method, namely Taguchi Design of Experiments (DoEs) by varying the process factors used in the AISI 1045 steel material cutting process. The control factors in this study consisted of three factors, namely cutting speed, gas pressure, and tip distance. The cutting speed and cutting gas pressure are significant factors in the optimization of the AISI 1045 steel cutting process for minimum kerf width with a contribution of 95.6%, while the tip / nozzle height factor is not significant in the optimization of the AISI 1045 steel cutting process for the kerf width minimum. The optimum parameter values to obtain the minimum kerf width in AISI 1045 steel are cutting speed of 250 mm/min, gas pressure of 3 kgf/cm2, and tip height of 4 mm. Furthermore, the results of the verification tests carried out indicated that the optimal process parameter formula obtained is feasible to use, indicated by the S / N ratio and confidence interval (CI) of prediction and verification that coincide with one another. The optimal process parameter formula can be used as a reference for industrial production activities with a 95% success rate.