Influence Of Oxygen Partial Pressure Research Articles

Influence of oxygen partial pressure on the passivation and depassivation of super 13Cr stainless steel in high temperature and CO2 rich environment.

The passivation and depassivation characteristics of Super 13Cr stainless steel were examined under a range of oxygen partial pressures within a high-temperature (120 ℃) and high-pressure (3MPa) CO2 atmosphere. We performed comprehensive electrochemical assessments, encompassing open-circuit potential monitoring, electrochemical impedance spectroscopy, and linear polarization resistance analysis, to evaluate the corrosion resistance and passive film stability. The results demonstrate that the addition of low O2 partial pressures enhanced the stability of the passive film, while higher O2 levels led to the loss of the passivation properties of Super 13Cr stainless steel. The study elucidates the pivotal role of oxygen in the corrosion mechanisms affecting Super 13Cr stainless steel, presenting valuable data to enhance for integrity management in severe environmental conditions.

The influence of oxygen partial pressure on the properties of sputtered vertical NiO/β-Ga2O3 heterojunction diodes

In this work we present studies on the influence of oxygen partial pressure on the properties of sputtered vertical NiO/β-Ga2O3 heterojunction diodes. Obtained results shows substantial effect of oxygen partial pressure on the electrical properties of NiO/β-Ga2O3 heterojunction diodes. The diodes with NiO layers deposited in pure Ar shows Schottky-like I-V characteristics with low ideality factor of 1.05 and barrier height of 1.27 eV as well as low turn-on voltage close to 1V. On the other hand, diodes with NiO layer deposited in oxygen containing atmosphere shows typical p-n diode characteristics. The best electrical characteristics i.e. low on-state resistance of 2.85 mΩcm2, lack of defects and low ideality factor down to 1.07 at RT along with high breakdown voltage close to 900V without any junction termination, were obtained for diodes with NiO layers deposited at 50 % oxygen content. We have demonstrated that by optimization of oxygen partial pressure, the properties of NiO/β-Ga2O3 heterojunction diodes can be tuned and excellent electrical performance in terms of low-on state resistance, high breakdown voltage, low-leakage current and low ideality factor, can be obtained.

Influence of oxygen partial pressure on homoacetogenesis and promotion of acetic acid accumulation through low pH regulation under microaerobic conditions.

Homoacetogenesis is an important pathway for bio-utilization of CO2; however, oxygen is a key environmental influencing factor. This study explored the impact of different initial oxygen partial pressures (OPPs) on homoacetogenesis, while implementing low pH regulation enhanced acetic acid (HAc) accumulation under microaerobic conditions. Results indicated that cumulative HAc production increased by 18.2% in 5% OPP group, whereas decreases of 31.3% and 56.0% were observed in 10% and 20% OPP groups, respectively, compared to the control group. However, hydrogenotrophic methanogens adapted to microaerobic environment and competed with homoacetogens for CO2, thus limiting homoacetogenesis. Controlling influent pH 5.0 per cycle increased cumulative HAc production by 18.3% and 18.2% in 5% and 10% OPP groups, respectively, compared with the control group. Consequently, regulating low pH effectively inhibited methanogenic activity under microaerobic conditions, thus increasing HAc production. This study was expected to expand the practical application of homoacetogenesis in bio-utilization of CO2.

Influences of oxygen partial pressure on the phase composition of the (Bi, Pb)-2212 precursor powder

Bi-2223 tapes, synthesized through the two-powder method, exhibit distinctive features such as high current density and a controllable secondary phase. Traditionally, the two-powder method involves the separate preparation of Bi-2212 and CaCuO powders followed by their mixing. However, during this process, it is necessary to dope the Bi-2212 powder with an appropriate Pb content to achieve a stable lattice structure in the Bi-2223 phase. The alteration of ion valences between Pb2+ and Pb4+ influences the oxygen content, thereby affecting the phase formation of (Bi, Pb)-2212 and, consequently, the final properties of Bi-2223 tapes. Surprisingly, limited research has explored the impact of the heat treatment process on (Bi, Pb)-2212. Consequently, this study investigates the phase composition and microstructure of (Bi, Pb)-2212 under various oxygen partial pressures to deepen our understanding of the effect of Pb on the composition of (Bi, Pb)-2212. Simultaneously, the behavior of Pb in the lattice of Bi-2212 is analyzed. Ultimately, the findings reveal that low oxygen conditions are advantageous for fabricating (Bi, Pb)-2212 powder with a high main phase content and a reduced secondary phase, thereby demonstrating excellent current-carrying performance in Bi-2223 tapes.

Micron-sized iron particles as energy carrier: Cycling experiments in a fixed-bed reactor

Iron is a promising energy carrier with the potential to store substantial amounts of energy over extended time periods with minimal losses. For instance, the energy from green hydrogen sources can be used to reduce iron oxides, be stored or transported, and thus be regained by exothermic oxidation of the iron. This work explores the influence of oxygen partial pressure and temperature on the oxidation process in a fixed-bed reactor. Furthermore, the analysis extends to the reduction of oxidized iron particles at varying temperatures. The experimental findings highlight that both oxidation and reduction progress through the fixed-bed reactor as distinct reaction fronts. In the oxidation process, the speed of the reaction front increases with rising oxygen content and temperature, resulting in a higher reaction rate and a correspondingly increased heat release. Conversely, the reaction rate for reduction experiences a notable decrease for 600°C and 700°C. The reprocessability of the iron powder was validated for up to 16 cycles under the optimal reaction conditions established. Furthermore, it was demonstrated that the performance improves with an increasing number of cycles. This improvement is attributed to the formation of pores due to density changes and the subsequent creation of a larger surface area, mitigating the negative effects of sintering and agglomeration.

Influence of oxygen partial pressure on the structural, optical and electrochromic properties of NiO thin films grown by magnetron sputtering

Influence of oxygen partial pressure on the structural, optical and electrochromic properties of NiO thin films grown by magnetron sputtering

Influence of oxygen partial pressure on the performance of MoO3-based ultraviolet photodetectors

To save our motherland from the harmful ultraviolet (UV) ray, the essentiality of UV photodetectors is increasing gradually. Herein, the MoO3-x thin films are deposited onto the SiO2/Si substrates through a sputtering technique by varying the oxygen partial pressure (pO2) at a substrate temperature of 200°C to examine the UV photodetector performance. It is observed that the thickness of the thin film is decreased with an increase in the pO2 due to the less ejection of atoms from the oxidized target surface. Structural study confirms the improved crystalline nature of the thin film deposited at 5.0% of pO2 and results in better electrical properties. The photodetector performance under UV illumination is studied as a function of pO2. The linear behavior of the current-voltage (I-V) characteristics attests to the ohmic contact nature between the photoactive layer (MoO3-x) and the metal (Ag) electrode interface. The fabricated photodetector test-device achieves a high photocurrent of 11.22 µA, a fast response time of 100 ms, and a superior responsivity of 1.537 A/W even at a lower optical power density of 0.0292 mW/cm2. Finally, these enhanced figures of merit of the MoO3-based photodetector could show a significant path toward the development of fast UV photodetector and optoelectronic devices.

The influence of oxygen partial pressure on the base oxide of chromia forming steels: The story prior to breakaway oxidation

The influence of pO2 on the base oxide formed on 304 L stainless steel has been investigated at 600 °C. The alloy was exposed in 5%O2-95%N2 and 10%H2-20%H2O-Ar atmospheres and the initial stages of oxidation were analysed by TEM and EDX. In both environments, the thin scale consists of a Cr-rich oxide overlaid by a FeCrMn oxide. However, the subscale formed in H2-H2O is richer in Cr compared to the 5%O2-95%N2 case (∼90 cation% and ∼70 cation% respectively). The findings are in good agreement with thermodynamic calculations and can explain breakaway oxidation of marginal chromia forming steels in H2-H2O.

Influence of oxygen partial pressure on the strain behaviour of reactively co-sputtered Ga doped ZnO thin films

Gallium doped ZnO films (GZO) were deposited by reactive co-sputtering of Zn and GaAs at different partial pressures of oxygen in Ar-O2 mixture. The GZO films were deposited at 375 °C, with GaAs area coverage of 0 - 3 % and 4 - 10 % O2 in sputtering atmosphere. The composition of GZO films was studied by X-ray photoelectron spectroscopy, which showed that the films deposited at 4 % and 5 % O2 display Ga/Zn ratio of ∼ 0.1 and contain oxygen vacancies, while those deposited at 6 % and 7 % O2 display Ga/Zn ratio of ∼ 0.01 and contain chemisorbed/interstitial oxygen. X-ray diffraction measurements supported by Raman studies revealed that undoped ZnO films are strongly c-axis oriented and display decrease of crystallite size along c-axis, along with substantial increase of hydrostatic tensile strain with increase of O2 percentage, which are attributed to the presence of interstitial oxygen. In sharp contrast, GZO films deposited at 4 % and 5 % O2 under limited oxygen availability, display smaller and mis-oriented crystallites along c-axis and large compressive strain, which is also hydrostatic, owing to the incorporation of Ga. The GZO films deposited at 6 % and 7 % O2 display improved crystallinity and decrease of compressive strain, which are attributed to reduced Ga content of the films and sufficient availability of oxygen during deposition. This study reveals the critical influence of the partial pressure of oxygen on the stoichiometry, doping concentration, crystallinity and the nature of strain in reactively sputtered GZO films.

Amorphous InGaZnO Thin-Film Transistors with Double-Stacked Channel Layers for Ultraviolet Light Detection.

Amorphous InGaZnO thin film transistors (a-IGZO TFTs) with double-stacked channel layers (DSCL) were quite fit for ultraviolet (UV) light detection, where the best DSCL was prepared by the depositions of oxygen-rich (OR) IGZO followed by the oxygen-deficient (OD) IGZO films. We investigated the influences of oxygen partial pressure (PO) for DSCL-TFTs on their sensing abilities by experiments as well as Technology Computer Aided Design (TCAD) simulations. With the increase in PO values for the DSCL depositions, the sensing parameters, including photogenerated current (Iphoto), sensitivity (S), responsivity (R), and detectivity (D*) of the corresponding TFTs, apparently degraded. Compared with PO variations for the OR-IGZO films, those for the OD-IGZO depositions more strongly influenced the sensing performances of the DSCL-TFT UV light detectors. The TCAD simulations showed that the variations of the electron concentrations (or oxygen vacancy (VO) density) with PO values under UV light illuminations might account for these experimental results. Finally, some design guidelines for DSCL-TFT UV light detectors were proposed, which might benefit the potential applications of these novel semiconductor devices.

Investigation of amorphous (Ir,Ru)-Si and (Ir,Ru)-Si-O Schottky contacts to (001) [formula omitted]-Ga[formula omitted]O[formula omitted

In this work we propose a new scheme for Schottky contacts to β-Ga2O3, namely — Ru-Si-O and Ir-Si-O conductive layers, fabricated by means of reactive magnetron sputtering of ruthenium or iridium silicide (Ru-Si, Ir-Si) targets in oxygen containing atmosphere. The influence of oxygen partial pressure during deposition on the microstructure and electrical parameters of layers was investigated. The properties of Ir-Si-O and Ru-Si-O as well as Ir-Si and Ru-Si Schottky contacts to β-Ga2O3 were compared. Work function of Ir-Si-O layers was in range of 4.97–5.08 eV as compared to 5.6–5.65 eV for Ru-Si-O layers. The investigated Schottky contacts show strong positive correlation between homogeneous barrier height and contact work function, roughly following Schottky–Mott relation. Our findings opens new possibilities to produce Schottky contacts to β-Ga2O3 with tailored properties using the M-Si-O (where M is transition metal) material system.

Sugar acid production on gold nanoparticles in slurry reactor: Kinetics, solubility and modelling

Sugar acids obtained by oxidation of sugars are very valuable molecules which are used as chelating agents, binders as well as ingredients in pharmaceuticals. Arabinonic acid was prepared by oxidation of arabinose on gold nanoparticles deposited on an aluminium oxide carrier. A systematic reaction kinetic study was conducted to reveal the influence of oxygen partial pressure and pH on reaction rate and product selectivity. Experiments were carried out in a laboratory-scale semi-batch reactor which was operated at 70 °C and oxygen partial pressures 0.125–1.0 atm. The pH of the aqueous sugar solution was 6–8. Oxygen was continuously flowing through the semibatch slurry reactor and the pH was kept constant by adding NaOH during the experiments. The oxygen solubility in the reaction mixture was determined in separate experiments. A reaction mechanism was proposed for the formation of arabinonic acid (main product) and arabinolactone (intermediate by-product). The surface reaction of competitively adsorbed arabinose and oxygen was assumed to be rate determining for the arabinose consumption. For the formation of arabinonic acid from arabinolactone, the rate determining step was presumed to be the reaction between arabinolactone and sodium hydroxide. The reactor was described with the perfect backmixing model and the component mass balances were solved numerically during the estimation of kinetic parameters by nonlinear regression analysis. The kinetic model gives new insights in the reaction mechanism and described the experimental data very well. The model has potential for application in the oxidation of other monomeric sugars, too.

Round-Robin Measurement of Surface Tension for Liquid Titanium by Electromagnetic Levitation (EML) and Electrostatic Levitation (ESL)

To accurately measure the surface tension of liquid titanium free of contamination from chemical reaction with the supporting materials and dissolution of atmospheric oxygen, the measurement was performed by using electromagnetic levitation (EML) and electrostatic levitation (ESL) in consideration of the influence of oxygen partial pressure of the measurement atmosphere, PO2. When liquid titanium was maintained at 2000 K under Ar–He gas with PO2 of 10 Pa flowing at 2 L·min−1 using EML, the surface tension decreased with time due to the dissolution of atmospheric oxygen into the sample. When the PO2 of the gas was decreased to 10−2 Pa, the oxygen content and the surface tension were confirmed to not vary, even after 120 min. Even though PO2 further decreased to 10−11 Pa under Ar–He–H2 gas, the surface tension slightly increased with time due to gas phase equilibrium between H2 and H2O that allowed for a continuous dissolution of atmospheric oxygen into the liquid titanium. The surface tension of liquid titanium measured by ESL, which prevents contamination of the sample from supporting materials and the high 10−5 Pa vacuum inhibits the dissolution of oxygen, showed almost the same value as that measured under Ar–He gas at PO2 of 10−2 Pa by EML. From the measurement results of EML and ESL, the surface tension of the 99.98 mass % pure liquid titanium, free from any contaminations from chemical reactions, with the supporting material and dissolved oxygen was expressed as σ99.98%=1613−0.2049T−1941 (10−3 N·m−1).

Distribution of noble metals between slag and matte phases during smelting of copper-sulphide and copper-nickel concentrates

In this work, we analyse and structure the information on the distribution of noble metals during pyrometallurgical processing of copper-sulphide and copper-nickel concentrates, available in domestic and foreign scientific sources. The data on the influence of oxygen partial pressure in the system and, consequently, the matte composition, process temperature, and the phase composition of slag on the distribution of platinum group metals, gold, and silver between the smelting products were analysed. Broad-ranging information on the distribution of the examined metals between matte and slag in the processing of copper-sulphide and copper-nickel concentrates was studied. It was established that the distribution of noble metals between the products of smelting using modern analytical methods is still in its early stages. Contradictory information on the behaviour of gold, silver, and platinum group metals during the pyrometallurgical processing of copper-sulphide and copper-nickel concentrates is presented in literature due to the variations in the experimental procedures, preparation, and analysis of test samples, and, as a result, further interpretation of the obtained results. Furthermore, no data on the influence of such technological parameters as magnetite content in the slag phase, the relationship between copper and nickel in the initial furnace charge and obtained mattes on the distribution of gold, silver, and platinum group metals between the products of smelting are available. In addition, no information on the distribution of noble metals during the pyrometallurgical slags depletion obtained in oxidative smelting of copper-nickel production has been published. Thus, it was decided to perform further research on establishing optimal technological conditions for oxidising smelting of copper-sulphide and copper-nickel concentrates, as well as pyrometallurgical depletion of slags, allowing for the highest extraction rates of noble metals into the target product.

Sputter deposited tungsten oxide thin films and nanopillars: Electrochromic perspective

Tungsten oxide (WO3) thin films and nano pillars were grown on FTO and corning substrates by using DC magnetron sputtering. Structural properties, surface morphology, optical properties, and electrochromic properties were systematically characterized by using SEM, XRD, UV–Vis Spectrometer, and Electrochemical Analyser respectively. Increased oxygen partial pressure resulted a rise in the optical transmittance from 72% to 89% at a wavelength of 600 nm. Moreover, coloration efficiency was also found to vary with partial pressures for both planar and glad from 30.48 cm2C-1 to 78.36 cm2C-1. We observe that glad deposited nano pillars showing higher coloration efficiency as compared to the planar thin film. The coloration efficiency found for the planar thin film and nano pillars at optimized partial pressure are 37.04 cm2C-1 and 78.36 cm2C-1 respectively. A strong influence of oxygen partial pressure and surface to volume ratio has been observed on the coloration efficiency, which can play a major role in the electrochromic application.

Nano-LaCoO3 infiltrated BaZr0.8Y0.2O3− electrodes for steam splitting in protonic ceramic electrolysis cells

Protonic ceramic electrolysis cell (PCEC) is a promising technology for production of pure dry hydrogen due to the low operating temperature and high efficiency. One of the obstacles for commercialization of PCEC technology is the poor performance and insufficient long-term durability of the oxygen electrode. In this study, we address the above challenge by designing a LaCoO3 (LC) catalyst infiltrated porous BaZr0.8Y0.2O3−δ (BZY20) backbone electrode (LC-BZY20). The performance and durability of the LC-BZY20 electrode are investigated on symmetrical cells using electrochemical impedance spectroscopy (EIS). The total electrode polarization resistance (RP) values of the electrode are 0.56, 1.24, 2.18, and 2.90 Ω cm2 in 3 ​vol% humidified synthetic air at 600, 550, 500, and 450 ​°C, respectively, indicating good electrochemical performance of the LC-BZY20 electrode. Furthermore, the LC-BZY20 electrode displays good stability, without significant performance degradation when tested at 600 ​°C in 10 ​vol% humidified air for 900 ​h. We further study the influence of oxygen partial pressure (Po2) and steam partial pressure (PH2O) on the response of the EIS data, and propose a set of chemical and electrochemical processes involved in the steam splitting reaction in the LC-BZY20 electrode.

Influence of oxygen partial pressure and annealing temperature on the physical properties of nanostructured ZnO thin films prepared by RF magnetron sputtering

Influence of oxygen partial pressure and annealing temperature on the physical properties of nanostructured ZnO thin films prepared by RF magnetron sputtering

Influence of oxygen partial pressure on the structural, optical and electrical properties of magnetron sputtered Zr0.7Nb0.3O2 films

Influence of oxygen partial pressure on the structural, optical and electrical properties of magnetron sputtered Zr0.7Nb0.3O2 films

Influence of Oxygen Partial Pressure on Cathodic Polarization of LaNiO3/GDC Composite Cathode

LaNiO3/GDC composite is one of the potential cathodic materials for intermediate temperature SOFCs. In order to evaluate its electrochemical performance, influence of oxygen partial pressure on cathodic polarization is examined with an electrolyte supported symmetric cell and a frequency response analyzer. An electrolyte disk made of GDC is used for the electrochemical symmetric cell. The operating temperature was controlled from 773K to 1073K, and the partial pressure was controlled between −4 < log(pO2) atm < 0 in this study.Polarization resistance increased with decreasing oxygen partial pressure at any temperature. In addition, the characteristic frequency (the summit frequency) of the impedance arc decreased with decreasing oxygen partial pressure. In order to search for the reaction mechanism, the rate-determining step approximation is applied to the experimental results. As a result, a rate-determining step is not dissociative adsorption of oxygen, but apparent oxygen reduction (charge transfer) reaction at temperature in the range from 773K to 973K. However, activation energy of the interfacial conductivity which is a reciprocal of polarization resistance is lower than 100 kJ/mol. Therefore, the rate-determining step is presumably a surface diffusion step, which is a migration step of dissociative oxygen from active point on the LaNiO3 surface to double phase boundary. At 1073K and higher oxygen partial pressure condition, the rate-determination step is still apparent oxygen reduction (charge transfer) reaction. Whereas at 1073K and lower oxygen partial pressure condition, the rate-determining step may be dissociative adsorption of oxygen.

Influence of Oxygen Partial Pressure on Cathodic Polarization of LaNiO3/GDC Composite Cathode

LaNiO3/GDC composite is one of the potential cathodic materials for intermediate temperature SOFCs. In order to assess its electrochemical performance, influence of oxygen partial pressure on cathodic polarization is examined with a LaNiO3/10GDC|10GDC|LaNiO3/10GDC symmetric cell by electrochemical impedance spectroscopy. The operating temperature was controlled from 773K to 1073K, and the partial pressure was controlled between −4 ≤ log(pO2/atm) ≤ 0 in this study. Polarization resistance increased with decreasing oxygen partial pressure at any temperature. In addition, the characteristic frequency (the summit frequency) of the impedance arc decreased with decreasing oxygen partial pressure. This implies that the rate determining step is changed by oxygen partial pressure. In practical operating condition: -1 ≤ log (pO2/atm), rate determining step is charge transfer reaction at 773 K and 873 K in this case.