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The electrochemical performance of solid oxide cells (SOCs) is investigated under both fuel cell and electrolyzer operations to understand their asymmetric behavior between the two operation modes. The current–voltage and electrochemical impedance characteristics of a hydrogen-electrode-supported cell are experimentally analyzed. Also, a numerical model is developed to reproduce the cell performance and to understand the internal resistances of the cell. Partial pressures of supplied gas and load current are varied to evaluate their effects on the cell performance. The gas partial pressures of hydrogen and steam supplied to the hydrogen electrode are kept equivalent so that the cell performance can be fairly compared between the two operation modes when the same current is applied. It is found that the origin of the asymmetry is mostly from the hydrogen electrode; both activation and concentration overpotentials show asymmetric behavior particularly at high current densities. A numerical experiment is also conducted by deliberately changing parameters in the model. Asymmetry in the activation overpotential is found to be originated from the non-identical charge-transfer coefficients in the Butler–Volmer equation and also from the non-uniform gas concentration formed in the hydrogen electrode under current-biased conditions. On the other hand, asymmetry in the concentration overpotential is associated with the non-equimolar counter diffusion of hydrogen and steam caused by the effect of Knudsen diffusion. Therefore, enhancing gas transport in the hydrogen electrode and reducing the contribution of Knudsen diffusion are effective approaches to reduce asymmetry not only in the concentration overpotential but also in the activation overpotential.

Lithium-rich manganese-based oxides (LRMOs) have been considered as one of the most promising cathode materials owing to their superior specific capacity and high operating voltage. However, their large-scale commercial applications are limited due to problems such as structural instability, voltage decay, and poor cycle stability. Herein, pre-generated oxygen vacancies and oxygen-deficient phase were introduced to Li1.2Mn0.6Ni0.2O2 (LMNO) using a facile urea-assisted mixed gas treatment (UMGT) method for facilitating electronic and ionic conductivity, reducing the surface oxygen partial pressure, and suppressing the release of lattice oxygen. Compared with the pristine LMNO material, the UMGT sample modified at 200 °C exhibited enhanced discharge capacity, capacity retention, and rate capability. In addition, the Li+ diffusion coefficient significantly improved by 50% than that of the reference LMNO. More importantly, the voltage decay was effectively suppressed, with average potential decreasing from 0.53 V (LMNO) to 0.39 V (UMGT-200) after 200 cycles at 1 C. The proposed UMGT method provides an effective strategy to alleviate the phase transition and improve the electrochemical performance for lithium-rich materials, and identifies a promising research direction to inhibit the voltage decay of layered anion redox cathode materials.

Molybdenum silicides (Mo–Si) have attracted great interest owing to their good electrical conductivity, ultra-high melting point and well oxidation resistance. In this work, the controllable syntheses of Mo5Si3 and Mo3Si powders by silicothermic reduction of MoS2 in the presence of lime are studied for the first time. The internal mixture composed of MoS2 and Si is wrapped by sufficient CaO. After the reaction is finished, the synthesized molybdenum silicides can be easily separated from the desulfurization layer by peeling off the desulfurization product. The results show that Mo3Si and Mo5Si3 can be prepared at 1500 °C for the samples with the MoS2:Si molar ratio of 1:1.7 and 1:2.33, respectively. In addition, the results show that both SiS2 and SiS can be formed during the heating process. The thermodynamic analysis about the disproportionation reaction of SiS indicates that the existence of SiS2 depends on the partial pressure of SiS (PSiS) and temperature. Moreover, it is demonstrated that SiS2 is preferentially formed under low temperature conditions. As the temperature rises, it is much easier for SiS2 to react with Si to form SiS. Additionally, this work experimentally proves for the first time that SiS gas can directly reduce MoS2 to form MoSi2 and SiS2. Subsequently, the recovery of S in the desulfurization product was studied. S in MoS2 was first captured by CaO in the form of CaS (accompanied by Ca2SiO4 and Si). In order to solve this CaS containing desulfurization product which is detrimental to the environment, CaS in the desulfurization product is react with Fe2O3 and C to form FeS. This work provides new insights into the closed-loop capture and recovery of S in the process of extracting metals or metal compounds from sulfide ores.

Single-oriented pure phase CuGaO2 and CuGa2O4 films have been successfully grown on β-Ga2O3 ( 2 ¯ 01) substrate by reactive deposition epitaxy at different oxygen partial pressures. Oxygen partial pressure-controlled mass-transport of Cu atoms is the dominant controlling parameter for CuGaO2 and CuGa2O4 growth. As the oxygen partial pressure increases, the amount of Cu atoms diffused in to the substrate surface under the control of mass-transport increases gradually and the Cu/Ga atomic ratio involved in the reaction progressively decreases, resulting in the product changing from CuO and CuGaO2 to CuGa2O4. After Chemical-mechanical Polishing (CMP) treatment, the CuGaO2 and CuGa2O4 films show pure phase with narrow full-width half-maximum (FWHM) according to high-resolution X-ray diffraction (HR-XRD). In addition, the transmission electron microscopy (TEM) results indicated better interface quality and epitaxial relationship between Cu-Ga-O films and β-Ga2O3 substrate. The smooth surface of Cu-Ga-O films can be obtained after CMP treatment which is confirmed by atomic force microscopy (AFM) results. It presents a feasible route to prepare β-Ga2O3-based heterojunction via reactive deposition epitaxy to expand the application of β-Ga2O3 in ultraviolet detection and power devices.

Cubic perovskite BaxSr1-xCoyFe1-yO3-δ (BSCF), with x = 0.5 and y = 0.8, is one of the oxygen permeable mixed ionic-electronic conducting (MIEC) membrane materials having the highest oxygen permeation flux reported. The material has potential for high-temperature electrochemical applications such as oxygen separation membrane and cathode for Solid Oxide Fuel Cells (SOFCs). The material has been highly studied, focusing on the oxygen transport properties, thermochemical expansion, mechanical properties, high temperature creep behavior, chemical sealing, etc. Therefore, a review article that consolidates the existing knowledge is necessary. The available review articles have focused on mechanical properties and applications as cathode for intermediate temperature (IT) SOFCs. Hence, this review article has covered additional information about crystal structure and oxygen non-stoichiometry of BSCF, material synthesis, membrane fabrication, thermomechanical stability, phase stability with respect to temperature and oxygen partial pressure, mechanical properties as well as the performance analysis in terms of oxygen permeation flux and failure analysis. It also emphasizes the potential of BSCF as MIEC membrane material. The content is equally helpful for researchers who are newcomers to the field and have the intention to provide a basic understanding of MIEC membrane materials.

The reaction between chamotte and active carbon at high temperature and low oxygen partial pressure conditions has been investigated. Both components react at temperatures above 1400 °C where cristobalite is reduced by the carbon while increases the mullite content. At 1600 °C mullite tends to disappear due to the reduction reaction leading to the formation of alumina. The reaction between chamotte and active carbon in these conditions produces the reduction of silica and mullite. This process increases with the reaction time although not all the active carbon is consumed. The graphite nanodomain size of the active carbon tends to decrease with respect to the original size with both the temperature and the reaction time. The microstructures of the obtained materials present a glassy phase due to the inherent presence of impurities in chamotte, and where small particles, pores and mullite needles are also observed. The presence of this glassy phase becomes more pronounced with the treating temperature while solid particles and pores tend to disappear, moreover, the formation of the glassy phase occurs in a less extent due to the higher concentration of active carbon. The presence of the liquid glassy phase also favours the formation of the long-needle like mullite crystals.

In order to solve the oxidation problem of the Ni-based solid oxide electrolysis cells (SOECs), SOECs with symmetrical electrode Sm0.5Sr0.5FeO3-δ- Gd0.1Ce0.9O2-δ (SSF-GDC) were systematically investigated, including the steam partial pressure, the working temperature, the electrolysis voltage. The reversible symmetrical cells with SSF-GDC electrode under humidified hydrogen presented good reversibility, and the maximum electrolysis current density was 1025 mA cm−2 at 800 °C with the applied voltage of 2V. In the case of direct N2 with 20% steam partial pressure as fuel, the symmetrical cells generated the maximum electrolysis current density increased from 267 to 1560 mA cm−2 at 650–800 °C. The influence of the steam partial pressure on the steam electrolysis showed that the maximum electrolysis current densities increased with the increase of the steam partial pressure from 3% to 20%, and the steam electrolysis with 3% steam partial pressure showed obvious concentration polarization due to insufficient steam partial pressure at high electrolysis current density. Finally, the short-term stability at different electrolysis voltages and long-term stability at the electrolysis voltage of 1.5V showed that there was no attenuation after 25 h operation, indicating that SSF-based symmetrical electrodes cab be an alternative to Ni-based fuel electrode materials for high-temperature steam electrolysis.

Oxy-fuel combustion with low NOx emission has been received more attention in recent years. In this work, a series of oxygen-staged experimental investigations of Shenmu bituminous coal with the preheated combustion technology was carried out under O2/CO2 atmosphere to obtain the effect of oxygen-staged on combustion and NOx emission. The results showed that the increase of excess oxygen coefficient of the primary air(λPr) decreased the temperature difference at each measuring point in the circulating fluidized bed, promoted the production of coal gas, facilitated the release of elements, and improved the mass conversion ratio of volatile matter up to 92.3%. Besides, the increase of λPr inhibited the conversion process of N-5 to N-6. At the same time, the release of nitrogen-containing volatile matter during the partial gasification process was also reduced. As the λPr increases, reducing the excess oxygen coefficient of the secondary air(λSe) or increasing the oxygen partial pressure of primary air were beneficial to reduce the emissions of NOx to a certain extent.

The influence of slag composition of FeO/TiO2 (=F/T) ratio, Al2O3/(SiO2+Al2O3) (=A/(S+A)) ratio and oxygen partial pressure ( p O 2 = 10 − 10 t o 10 − 9 a t m ) on the thermodynamic behavior of vanadium oxide in molten ilmenite smelting slag, i.e., FetO-TiO2-MgO-Al2O3-SiO2 system, was investigated at 1550 °C. The distribution ratio of vanadium (= L V ) between molten iron and FetO-TiO2-MgO-Al2O3-SiO2 slag increases with increasing F/T ratio, while it decreases with increasing A/(S+A) ratio. In addition, l o g L V generally increases with increasing theoretical optical basicity of the slag (= Λ s l a g ). Vanadium oxide (VOx) is expected to behave as an acidic component in the present system. Vanadium in ilmenite smelting slags primarily consist of V3+, V4+, and V5+ ions, as determined by Gaussian deconvolution of X-ray photoelectron spectra. A linear relationship between l o g ( w t % V 4 + / w t % V 3 + ) and l o g p O 2 is confirmed. Both (wt% V3+) and (wt% V5+) ions increase with increasing F/T ratio, whereas (wt% V4+) ions show the opposite behavior with increasing F/T ratio, irrespective of A/(S+A) ratio. Meanwhile, (wt% V3+) increase while (wt% V4+) and (wt% V5+) decrease with increasing A/(S+A) ratio. The linear relationship between l o g ( w t % V 3 + / w t % V 5 + ) and l o g ( w t % V 4 + ) has a slope of 1.8, which is good agreement with the theoretical slope of 2.0, which indicates that multi-valent vanadium ion species, i.e., V3+, V4+, and V5+, are thermodynamically balanced based on redox equilibria.

This study is designed to determine the H 2 S origin in the Ordovician Ma5 Member of Daniudi gas field and study the corrosion behavior of N80, P110 and N80S tubing and casings in medium-sulfur content HE16, micro-sulfur HE3 and low-sulfur HE1 gas wells. Therefore, method of weight loss of coupon on site were used to determine the corrosion rate. Similarly, SEM, XRD and EDS analyses were employed to know the corrosion products while establishing the relationship with H 2 S formation conditions. Results of this study show that, as the production time increases, there was initial increase in the volume of H 2 S before it finally decreases. Among the different sulfur gas wells, the corrosion rate of the HE16 is the largest, followed by the low-sulfur HE3 and the micro-sulfur HE1 (smallest). Within a gas well there exist a proportional relationship where higher partial pressure of H 2 S leads to higher corrosion rate. Generally, there is a trend of initial increase followed by decrease in the corrosion temperature of the gas wells in order of decreasing sulfur content (HE16, HE3 and HE1 well). Thus, the average corrosion temperature changing-rate of N80, P110, N80S pipe in the medium sulfur content well area, low sulfur content and micro-sulfur wells are 15.13%, 31.01% and 49.45% respectively. Although, the wells have some coupon corrosion products in common, there is still some basic differences in the composition of the HE1 wells (FeCO 3 and CaCO 3), HE3 wells (FeCO 3, FeS and CaCO 3) and HE16 wells (FeCO 3, FeS 0.9 , FeS and CaCO 3). These corrosion products are clearly stratified in the HE16 and HE3 wells, while no stratification occur in the HE1 wells. The densely structured FeCO 3 is well-distributed within just as the loose and poorly-converted sulfides are distributed on the surface. Both uniform and local corrosion exist simultaneously in the study area. The galvanic corrosion between the product substrate as well as the pitting caused by the inorganic salt result in local corrosion. In the micro-sulfur gas well, only uniform corrosion occur to form FeCO 3 as the corrosion product. For future development of the M5 member of Daniudi gas field, N80 tubing and casing is recommended for the micro-sulfur gas well, P110 or N80S material tubing and casing for the low sulfur gas well and N80S oil jacket for the sulfur gas well. It is good to note that special attention should be paid to the influence of temperature changes on the corrosion rate of the tubing and casing in the low-sulfur and medium-sulfur well zones.

The heating of high-Ni cathode materials under low O2 partial pressures has generally been considered undesirable. Contrary to this general understanding, this study reports the postheating of LiNi...

Rice (Oryza sativa) plants have porous or hollow organs consisting of aerenchyma, which is presumed to function as a low-resistance diffusion pathway for air to travel from the foliage above the water to submerged organs. However, gas movement in rice plants has yet to be visualized in real time. In this study involving partially submerged rice plants, the leaves emerging from the water were fed nitrogen-13-labeled nitrogen ([13 N]N2 ) tracer gas, and the gas movement downward along the leaf blade, leaf sheath, and internode over time was monitored. The [13 N]N2 gas arrived at the bottom of the plant within 10 min, which was 20 min earlier than carbon-11 photoassimilates. The [13 N]N2 gas movement was presumably mediated by diffusion along the aerenchyma network from the leaf blade to the root via nodes functioning as junctions, which were detected by X-ray computed tomography. These findings imply the diffusion of gas along the aerenchyma, which does not consume energy, has enabled plants to adapt to aquatic environments. Additionally, there were no major differences in [13 N]N2 gas movement between paddy rice and deepwater rice plants, indicative of a common aeration mechanism in the two varieties, despite the difference in their response to flooding.

This study examines the insulation coating technology of Fe–Si–Cr powder via selective oxidation annealing, which oxidizes elements selectively by controlling the oxidation potential. The study calculated the oxidation driving force of Fe, Si, and Cr, and conducted a thermodynamic analysis of oxidation and reduction conditions according to temperature and oxidation potential. Based on the results, a selective oxidation annealing was performed in an atmosphere in which Fe is reduced and only Si and Cr are selectively oxidized. The oxidation potential was controlled through the partial pressure ratio of hydrogen and water vapor. The XPS analysis results confirmed that a Si and Cr complex oxide layer formed on the powder surface after the selective oxidation annealing. Afterward, withstanding voltages were analyzed to evaluate the insulation property. Then, the withstanding voltage of the powder applying the selective oxidation annealing increased significantly compared to that of the initial powder. Further analysis showed that the powder annealed in an air atmosphere had a significantly lower saturation magnetic flux density than the initial powder, while the powder applying the selective oxidation annealing had only a slightly reduced saturation magnetic flux density.

To achieve high oxygen blocking structure of the ZrB2-MoSi2 coating applied on carbon structural material, ZrB2-MoSi2 coating was prepared by spark plasma sintering (SPS) method utilizing ZrB2-MoSi2 composite powders synthesized by self-propagating high-temperature synthesis (SHS) technique as raw materials. The oxygen blocking mechanism of the ZrB2-MoSi2 coatings at 1973 K was investigated. Compared with commercial powders, the coatings prepared by SHS powders exhibited superior density and inferior oxidation activity, which significantly heightened the structural oxygen blocking ability of the coatings in the active oxidation stage, thus characterizing higher oxidation protection efficiency. The rise of MoSi2 content facilitated the dispersion of transition metal oxide nanocrystals (5–20 nm) in the SiO2 glass layer and conduced to the increasing viscosity, thus strengthening the inerting impact of the compound glass layer in the inert oxidation stage. Nevertheless, the ZrB2-40 vol%MoSi2 coating sample prepared by SHS powders presented the lowest oxygen permeability of 0.3% and carbon loss rate of 0.29×10−6 g·cm−2·s−1. Owing to the gradient oxygen partial pressure inside the coatings, the Si-depleted layer was developed under the compound glass layer, which brought about acute oxygen erosion.

Radiative heat transfer strongly influences pollutant emission prediction in combustion systems. In this work, the weighted sum of gray gas (WSGG) models have been developed for calculating radiative heat transfer in hydrogen and hydrogen-mixture flames. The total pressure effect on cut-off width of the Lorentz line profile is analyzed and properly considered in the line by line (LBL) calculations. Based on the LBL benchmark results, two sets of WSGG model correlations have been proposed for H2O and its mixture with CO2 at a molar ratio (Mr) of 3, representing the typical combustion products of the hydrogen and a hydrogen-rich mixture (e.g., 50% hydrogen and 50% methane). The WSGG models are applicable and accurate with a total pressure ranging from 1 to 60 atm. Partial pressure is explicitly applied as an independent variable in the model coefficients to account for its nonlinear effect on gas emissivity, which is particularly important for a participating gas medium with a large amount of H2O at a total pressure below 5 atm. Detailed studies are carried out to solve radiative heat transfer in non-isothermal and non-homogeneous gas media at different conditions. Results show improvement over the existing WSGG models at the atmospheric pressure and have good agreement with LBL solutions under various conditions.

The change in longitudinal relaxation rate (R1 ) produced by oxygen has been used as a means of inferring oxygenation levels in magnetic resonance imaging in numerous applications. The relationship between oxygen partial pressure (pO2 ) and R1 is linear and reproducible, and the slope represents the relaxivity of oxygen (r1Ox ) in that material. However, there is considerable variability in the values of r1Ox reported, and they have been shown to vary by field strength and temperature. Therefore, we have compiled 28 reported empirical values of the relaxivity of oxygen as a resource for researchers. Furthermore, we provide an empirical model for estimating the relaxivity of oxygen in water, saline, plasma, and vitreous fluids, accounting for magnetic field strength and temperature. The model agrees well (R2 = 0.93) with the data gathered from the literature for fields ranging from 0.011 to 8.45 T and temperatures of 21-40 °C. This provides a useful resource for researchers seeking to quantify pO2 in simple fluids in their studies, such as water and saline phantoms, or bodily fluids such as vitreous fluids, cerebrospinal fluids, and amniotic fluids.

Solid oxide fuel cells (SOFCs) are promising energy conversion devices because of their high electrical efficiency, even for small power systems. However, when the anode is exposed to reduction and oxidation (redox) cycles, the Ni phase causes a large microstructural change as a result of its chemical expansion and contraction. This negatively affects the electrochemical performance. However, most studies have focused on the redox cycling behaviors of SOFCs at high operation temperatures (≥ 800 °C). Therefore, in this study, we investigate the degradation behavior of the SOFC anode during redox cycles at 500 °C. To identify the individual steps of the electrochemical processes of the anode, in-situ monitored impedance spectra were analyzed using the distribution of relaxation time method at various oxygen and hydrogen partial pressures. Consequently, the electrode polarization process was deconvoluted into five sub-processes. During the redox cycles, three major peaks were altered: gas phase diffusion in the anode substrate (10–1–101 Hz), gas diffusion coupled with charge transfer reaction and ionic transport (102–103 Hz) and charged species across the Ni–yttria stabilized zirconia interface at the anode (103–104 Hz). The major degradation of the electrode performance at 500 °C was attributed to the increase in gas phase diffusion resistance due to Ni phase aggregation and the decrease in porosity in the anode during the redox cycles. This was confirmed by microstructural analysis. By contrast, the other two processes (102–103 and 103–104 Hz) compensated each other, thus having negligible effect on performance degradation.

The effects of sintering atmospheres (air, O2, and N2) and defect chemistry role of Mn in the structure, electrical properties, and conduction mechanism of Ca0.6Sr0.4TiO3 (CST) ceramics were extensively investigated in this study. O2 atmosphere sintering resulted in a decrease in the concentration of oxygen vacancies, as revealed by the expanded unit cell and increased Ti ions' valence state. The reverse was the case for samples sintered in N2. Interestingly, sintering in both of O2 and N2 resulted in deteriorated bulk resistivity, due to the transition of the conduction mechanism (n-type electronic→ionic→p-type electronic conduction) with increasing oxygen partial pressure (PO2). This was verified by subjecting the samples to annealing treatment in different atmospheres and measuring their high-temperature equilibrium conductivities. Additionally, Mn-doped CST ceramics demonstrated higher resistivity than that of the pure CST ceramics, regardless of the sintering atmospheres, which could be attributed to the self-changing of Mn ions’ valence state in different PO2.

In this work, to develop better OCM catalysts, especially with improved ethylene selectivity, the promotional effects of BaBr2 on defect BaSnO3 has been investigated by changing the BaBr2/BaSnO3 molar ratio. XRD and Raman have substantiated that BaBr2 and BaSnO3 co-exists in all the BaBr2-modified catalysts. Compared with pure defect BaSnO3, all the modified catalysts exhibit significantly improved OCM performance, particularly with extremely high ethylene selectivity. Electrical conductivity measurement have proven that defect BaSnO3 is a p-type semi-conductor favouring OCM reaction, whose surface possesses abundant vacancies. O2-TPD, CO2-TPD and electrical conductivity dependence on O2 partial pressure results have indicated that BaBr2 addition can enhance the surface oxygen vacancy concentration of BaSnO3, which facilitates the conversion of surface lattice O2− into OCM reactive oxygen sites, such as O22− and O2- anions. At the same time, a larger amount of moderate strength basic sites have been formed. EPR, in situ Raman and XPS results have demonstrated that the quantities of these active oxygen sites can be evidently improved by BaBr2 addition. More importantly, a type of new O2δ- (0

The safe widespread application of hydrogen-based fuels requires sensors that are long-term stable, inexpensive, hydrogen-specific, and have a short response time. In this regard, optical sensing based on nanostructured Pd alloys has shown great potential, but challenges remain, including understanding and controlling the surface composition under operation conditions. While the latter is crucial for long-term functionality and stability, it is experimentally very challenging to obtain accurate atomic-scale information. Here, we therefore scrutinize the behavior of two particularly relevant surface alloys, {111} AuPd and {111} CuPd, in H environments ranging from vacuum to fully covered surfaces. To this end, we employ a combination of alloy cluster expansions trained using density functional theory calculations, Monte Carlo simulations, and thermodynamic analysis to obtain the H coverage as well as the layer-by-layer composition of the near-surface region as a function of H partial pressure, temperature, and bulk composition. To overcome the symmetry reduction implicit to surface systems, we exploit local symmetries, which enables us to achieve accurate and reliable models at a low computational cost. In the case of AuPd, Au segregates to the surface in vacuum while Pd segregates to the surface at 100% H coverage, and the transition between these regimes occurs over a narrow H pressure interval. In the case of CuPd, on the other hand, the H coverage varies much more gradually with H pressure and is coupled to a nonmonotonic variation of the Cu concentration in the topmost surface layer. While there is a pronounced Cu depletion both at 0 and 100% H coverage, Cu enrichment is observed at 50% coverage at Cu bulk concentrations up to at least 10%, providing a nontrivial explanation for an apparent discrepancy between experiment and calculations that was observed previously. At the same time, layer 2 continuously shifts from Cu enrichment to Cu depletion with increasing H coverage. The results demonstrate the rich behavior that can result from the coupling of metal-metal and metal-hydrogen interactions at surfaces, even in apparently simple but concentrated systems. Moreover, they underline the advantages of simulations that account for temperature and pressure effects as well as models that can accurately capture the interactions over a wide composition range.

Samples of Ni-30Cr alloy were oxidized at different temperatures from 500 to 900 °C in a nominal oxygen partial pressure of 5 × 10−6 atm. The parabolic rate constants for growth of the oxide scales, which were confirmed to be chromia, were in agreement with the literature following an Arrhenius law. The semiconductor character of the chromia scale was investigated in order to reveal the nature of the dominant point defects responsible for the diffusion process during oxidation. An n-type semiconductor was found at low temperature (500 °C), and p-type semiconductor at high temperature (900 °C). Our results suggest that oxygen vacancies and chromium vacancies are dominant in grown chromia of n- and p-type, respectively.

This work focuses on PuCO-type phase formation at the surface of δ-Pu at temperatures above 300 °C under low oxygen partial pressure. Its growth was characterised by XRD and XPS and was found to follow parabolic kinetics law. This oxycarbide formation was thermodynamically supported by CALPHAD calculations. XPS investigations of PuCO phase reveal a singular plutonium oxidation state never observed in plutonium oxides (i.e. PuO2 or Pu2O3). Furthermore, the oxycarbide presence on the sample surface strongly impacts the oxidation rate in oxygen atmosphere, reducing drastically the other oxide growth.

For efficient energy conversion and energy storage, developing highly efficient hydrogen permeable membranes is a crucial issue. Ceramic hydrogen permeable membranes, i.e., protonic electronic mixed conductors, work on bipolar transport of protons and electrons. Ceramic composite membranes meet this requirement with chemical and thermal stability, and they can be used not only as hydrogen permeable membranes but also as electrolytes in protonic ceramic fuel cells (PCFCs). Although improvement in protonic conductivity at heterointerfaces between constituting materials and/or space-charge relaxation around the resistive grain boundaries can be possible origins of the enhanced hydrogen permeability in the composite electrolyte membranes, its detailed mechanisms have not been clarified yet and the strategy of material design for composite membranes has not been established. In this study, the transport properties of composite electrolyte membranes consisting of protonic conductors and electronic conductors are investigated to realize highly efficient PCFC operating at low temperatures and to clarify the principles of carrier transport in the composite membranes. For the protonic conductor and the electronic conductor, we selected La2Ce2O7 (LDC) with a fluorite structure and La0.3Sr0.6TiO3 (LST) with a perovskite structure, respectively. The composite membrane composed of LDC and LST (LDC/LST) with various LDC to LST ratios was prepared by a solid-state reaction. Phase stability of LDC and LST were investigated by X-ray diffraction (XRD) measurements. Transport properties of hydrogen permeation cells using the LDC-LST composite membranes with Pt electrodes were assessed by electrochemical impedance spectroscopy (EIS) measurements and hydrogen permeation measurements. Hydrogen fluxes were measured by gas chromatography. The EIS measurements revealed that the grain-boundary resistance was reduced for the LDC/LST composite membrane in comparison with an LDC membrane. In particular, LDC/LST (weight ratio 1:2) showed the smallest grain-boundary resistance of 26 Ω cm at 600°C under 1%H2/Ar among the measured samples. Besides, the hydrogen permeation measurement showed that LDC/LST exhibited higher hydrogen permeability than the LDC membrane. In addition, the hydrogen flux of LDC/LST (1:2) was almost twice as high as that of LDC at 600°C. The low grain-boundary resistance and the high hydrogen permeability of LDC/LST composite membrane suggests that the introduction of LST accelerates the proton conduction in the membrane.

The performance of cobalt supported on mesoporous alumina (MA) under the influence of reaction temperature (923 K–1073 K) and reactant partial pressure (10 kPa–40 kPa) for CO2–CH4 reforming was executed by using a tubular fixed-bed reactor. 10%Co/MA exhibited great catalytic performance ( X C H 4 = 70.9 % , X C O 2 = 71.7 % and D a = 1.3 % ), credited to the well dispersion of Co within pore MA, strong metal-support interaction, and MA confinement ability. Based on Langmuir-Hinshelwood kinetic analysis, the dissociative adsorption of both reactants on a single Co active site was selected for this study. The lower value of activation energy (28.9 kJ mol−1) suggested that Co particles were finely scattered on the MA surface. Regardless of carbon types, the amount of coke accumulated on the spent 10%Co/MA within 8 h of CO2–CH4 reforming was inhibited due to fine Co distribution inside MA structure, as well as lessened with the raise of reforming temperature from 923 to 1073 K due to improvement in reverse Boudouard reaction.

The role of porosity on the equilibration kinetics in electrical conductivity relaxation (ECR) experiments is highlighted. Both porous and dense conductivity bars are used to determine the chemical oxygen surface exchange coefficient (kchem) of neodymium nickelate Nd2NiO4+δ (NNO) from 600 to 800 °C. Using porous bars allows for quicker ECR experiments during which the conductivity transient is rate limited only by oxygen surface exchange which enables the use of a simple transient model. Additionally, porous bars have similar microstructures to porous electrodes which means they are critical for determining the oxygen exchange kinetics of realistic electrodes. ECR results on dense bars with porous coatings are also presented. The conductivity transients of dense and porous bars both show similar trends with oxygen partial pressure. Additionally, both porous and dense bars show a difference between oxidation and reduction transients with oxidation transients being faster than reduction transients.

As a promising solid electrolyte for thin-film lithium batteries, the amorphous Li0.33La0.56TiO3 (LLTO) thin film has gained great interest. However, enhancing ionic conductivity remains challenging in the field. Here, a systematical study was performed to improve the ionic conductivity of sputter-deposited LLTO thin films via the optimization of processing atmosphere and temperature. By combining the optimized oxygen partial pressure (30%), annealing temperature (300 °C), and annealing atmosphere (air), an amorphous LLTO thin film with an ionic conductivity of 5.32 × 10−5 S·cm−1 at room temperature and activation energy of 0.26 eV was achieved. The results showed that, first, the oxygen partial pressure should be high enough to compensate for the oxygen loss, but low enough to avoid the abusive oxygen scattering effect on lithium precursors that results in a lithium-poor composition. The oxygen partial pressure needs to achieve a balance between lithium loss and oxygen defects to improve the ionic conductivity. Second, a proper annealing temperature reduces the oxygen defects of LLTO thin films while maintaining its amorphous state, which improves the ionic conductivity. Third, the highest ionic conductivity for the LLTO thin films that were annealed in air (a static space without a gas stream) occurs because of the decreased lithium loss and oxygen defects during annealing. These findings show that the lithium-ion concentration and oxygen defects affect the ionic conductivity for amorphous LLTO thin films, which provides insight into the optimization of LLTO thin-film solid electrolytes, and generates new opportunities for their application in thin-film lithium batteries.

Despite the growing importance of oxygen-delivery devices worldwide, there are only a few reports of physiological data on various oxygen masks in children. The possibility of carbon dioxide (CO2) rebreathing has been a prevalent concern with the use of oxygen-delivery devices. OxyMask KidTM (Southmedic Inc. Canada; hereafter OxyMask) is expected to reduce CO2 rebreathing even at low oxygen flow rates because of its structural features. Biological data using OxyMask in children have not been well investigated. Measured respiratory parameters of OxyMask with those of a simple oxygen mask in healthy children were compared. Ten subjects were enrolled, with a median age of 5.4 years. All subjects used both OxyMask and a simple oxygen mask. The fraction of inspiratory oxygen (FIO2), partial pressure of inspiratory CO2 (PICO2), and partial pressure of end-tidal CO2 were measured using a sidestream gas-sampling monitor in all subjects. The oxygen flow rate was set at 1, 3, 5, and 10 L/min. FIO2 levels were higher with OxyMask than those with the simple oxygen mask at 3 L/min of oxygen. PICO2 levels were significantly lower with OxyMask than those with the simple oxygen mask (1.5 mmHg vs. 3.7 mmHg at 1 L/min, P = 0.005; 1.0 mmHg vs. 2.7 mmHg at 3 L/min, P = 0.005, respectively), whereas PICO2 levels were higher at low oxygen flow rates with both masks.Conclusion: Our results showed that higher FIO2 and less CO2 rebreathing were achieved with OxyMask than those with a simple oxygen mask at low flow rates of oxygen in healthy children. What is Known: • OxyMask is expected to reduce carbon dioxide rebreathing even at low oxygen flow rates because of its structural features. • Efficacy has been demonstrated in experimental models and adult data, but clinical data on the use of the OxyMask in children are limited. What is New: • Higher fraction of inspiratory oxygen and lesser carbon dioxide rebreathing were achieved with OxyMask than with a simple oxygen mask at low flow rates of oxygen in healthy children.

Impedance measurements on Mg-doped alumina ceramics, over the temperature range 400−910 °C, showed a combination of oxide ion conductivity and p-type electronic conductivity, depending on temperature and oxygen partial pressure. The oxide ion conductivity is attributed to oxygen vacancies, introduced as charge compensation for the Mg dopant. The p-type conductivity is attributed to hole creation on under-bonded oxide ions and is the dominant conductivity for measurements in air at high temperatures. In samples co-doped with Mg and Si, impedance measurements showed a reduction in oxide ion conductivity and therefore, number of oxide ion vacancies because the self-compensation mechanism of co-doping lead to direct replacement of Al3+by Mg2+ and Si4+; the level of p-type conductivity was also reduced.

The oxygen surface kinetics and mechanism of oxygen interaction between oxygen from the gas phase and yttria-stabilised zirconia nano-sized powder have been studied by pulse 18O/16O isotope exchange (PIE) in dry (O2) and humid (mixture O2 + H2O with pH2O = 2.6 kPa at T = 22 °C) oxygen atmospheres in comparison with micro-sized powder. Dependences of the heterogeneous oxygen exchange rate (rH) in the temperature range from 550 to 900 °C, and oxygen partial pressure range in the carrier gas and pulses of 5–19% have been obtained. It has been established that the presence of water causes a decrease in the heterogeneous oxygen exchange rate due to the presence of strongly bound hydroxyl groups in the nanopores of the sample. Differences between the mechanisms of isotopic exchange for dry and humid atmospheres have been found in this temperature range (550–700 °C). The observed differences are associated with the interaction of the gas phase and hydroxyls in the adsorbed layer of the oxide. An original method for the separation of the contributions of three types of oxygen exchange for dry and humid atmospheres has been proposed.

Transcutaneous monitoring is a noninvasive method to continuously measure the partial pressures of oxygen and carbon dioxide that diffuse through the skin and correlate closely with changes in blood gases. However, the contemporary commercially available electrochemical-based technology requires a heating mechanism and a bulky, corded, and expensive sensing unit. This study aims to demonstrate a prototype noninvasive, miniaturized monitor that uses luminescence-based technology to measure the partial pressure of transcutaneous oxygen, a surrogate of the partial pressure of arterial oxygen. To be able to build a robust measurement system, we conducted experiments to understand the temperature and humidity dependence of oxygen-sensitive platinum-porphyrin films. We performed a detailed analysis of both intensity and lifetime measurement techniques. To verify the performance, we tested the prototype in a small ex-vivo experiment involving three healthy human volunteers. We measured variations in the partial pressure of transcutaneous oxygen values due to pressure-induced arterial and venous occlusions on the volunteers' fingertips. The system resolves changes in the partial pressure of oxygen from 0 to 418 mmHg in the lab bench-top testing, covering the medically relevant range of 50-150 mmHg. Under fixed humidity, temperature, and the partial pressure of oxygen conditions, the sensor shows a 2% drift over 60 hours. The prototype consumes 9 mW of power from a 2.2 V external DC power supply.

The paper deals with the synthesis of coating based on molybdenum and molybdenum nitrides using cathodic arc deposition without the plasma assistance. The properties, composition and structure of the obtained coating are studied in detail. It is found that the nitrogen partial pressure in the gas mixture affects the nitrogen concentration in the coatings and the properties of the latter. The structure and phase composition of the coatings synthesized at a low partial pressure, are investigated by using the X-ray diffraction analysis and scanning electron microscopy.

To understand oxygen diffusion mechanisms in non-stoichiometric oxides, the possibility to explore structural changes as a function of the oxygen partial pressure with temperature and related oxygen bulk stoichiometry is mandatory. This article reports on the realization of a high-temperature furnace, suitable for single-crystal neutron diffraction, working continuously at temperatures of up to 1000°C at different and adjustable partial gas pressures of up to 2 bar (1 bar = 100 kPa). This allows exploration of the phase diagrams of non-stoichiometric oxides under in situ conditions and controlled oxygen partial pressure. As a pilot study, the structural changes of Pr2NiO4+δ were explored at room temperature (δ ≃ 0.24) and at 900°C under 1 bar P(O2) (δ ≃ 0.13) as well as under secondary vacuum (approximately 10−5 mbar) conditions yielding a δ close to zero. The strong anharmonic displacements of the apical oxygen atoms along the [110] shallow diffusion pathway, which were previously observed at room temperature and 400°C, become more isotropic at 900°C. The study shows that the anisotropic oxygen displacements, here related to lattice instabilities, play a major role in understanding oxygen diffusion pathways and related activation energies at moderate temperatures. This also shows the importance of the availability of reaction cells for single-crystal neutron diffraction to explore the phase diagram and associated structural changes of non-stoichiometric oxygen ion conductors and respective diffusion mechanisms.

The contact, and thus the hole collection between Cu2ZnSnSe4 (CZTSe) and Mo, is a crucial issue to improve the performance of CZTSe solar cells. In this work, a method to improve the back contact is explored by spraying Na3PO4 on the surface of the Mo back contact. With the O provided from Na3PO4, extra MoO2 and MoO3 are formed at the surface of the back contact, and partial MoO2 is transformed into MoSe2 under high Se2 partial pressure during the selenization process. The formation of MoSe2 progresses from dispersed spots to a continuous layer but not from the reaction between CZTSe and Mo. Although a thick MoSe2 layer is formed, the CZTSe device performance increases from 7.2% to 8.3% on average. This study affords new insight into the formation of MoSe2, thus deeply strengthening the understanding of the back contact of kesterite solar cells and of two-dimensional chalcogenide devices.

The rates of chemical expansion for 20 at % yttrium-doped barium zirconate upon hydration at 100–900 °C under water partial pressures of 0.008 and 0.023 atm have been studied using combined thermog...

Experimental measurements have been undertaken of the gas-matte-spinel and gas-slag-matte-spinel equilibria in the Cu–Fe–O–S–Si system at 1200°C and pSO2 of 0.1 and 0.6 bar. The technique involved ...

Arterial blood gas (ABG) measurements at both maximum depth and at resurfacing prior to breathing have not previously been measured during free dives conducted to extreme depth in cold open-water conditions. An elite free diver was instrumented with a left radial arterial cannula connected to two sampling syringes through a low-volume splitting device. He performed two open-water dives to a depth of 60 m (197′, 7 atmospheres absolute pressure) in the constant weight with fins competition format. ABG samples were drawn at 60 m (by a mixed-gas scuba diver) and again on resurfacing before breathing. An immersed surface static apnea, of identical length to the dives and with ABG sampling at identical times, was also performed. Both dives lasted approximately 2 min. Arterial partial pressure of oxygen ([Formula: see text]) increased during descent from an indicative baseline of 15.8 kPa (after hyperventilation and glossopharyngeal insufflation) to 42.8 and 33.3 kPa (dives 1 and 2) and decreased precipitously (to 8.2 and 8.6 kPa) during ascent. Arterial partial pressure of carbon dioxide ([Formula: see text]) also increased from a low indicative baseline of 2.8 kPa to 6.3 and 5.1 kPa on dives 1 and 2; an increase not explained by metabolic production of CO(2) alone since [Formula: see text] actually decreased during ascent (to 5.2 and 4.5 kPa). Surface static apnea caused a steady decrease in [Formula: see text] and increase in [Formula: see text] without the inflections provoked by depth changes. Lung compression and expansion provoke significant changes in both [Formula: see text] and [Formula: see text] during rapid descent and ascent on a deep free dive. These changes generally support predictive hypotheses and previous findings in less extreme settings. NEW & NOTEWORTHY Arterial blood gas measurements at both maximum depth and the surface before breathing on the same dive have not previously been obtained during deep breath-hold dives in cold open-water conditions and competition dive format. Such measurements were obtained in two dives to 60 m (197′) of 2 min duration. Changes in arterial oxygen and carbon dioxide (an increase during descent, and a decrease during ascent) support previous observations in less extreme dives and environments.

This study examined the effects of the oxygen partial pressure on the properties of heavily indium-doped tin-oxide (In-SnOx) thin films grown at room temperature by reactive direct-current pulse sputtering from a mixed metallic target containing Sn (70 atomic %)-In (30 atomic %). X-ray photoelectron spectroscopy (XPS), dynamic secondary-ion mass spectrometry, X-ray diffraction (XRD), and Hall Effect measurements showed that the In-SnOx samples prepared with oxygen pressures of 10–20% had metallic properties. This was attributed to the notable Sn0 area ranges of 5.6–17.3%, low resistivity ranges of 5.5×10−3–2×10−4 Ωcm, and the high carrier concentration ranges of 3.5×1021–5.1×1022/cm3. On the other hand, the Sn4+ area and the resistivity increased significantly to 73.3% and 9.4 Ωcm. In comparison, the Sn2+ area and the electron concentration decreased dramatically to 23.6% and 6.5×1016/cm3, respectively, with increasing oxygen partial pressure up to 30%. The samples prepared with oxygen pressures higher than 20% exhibited nonmetallic properties with the dominant n-type SnO2 phase. This steep increase in the Sn4+ area was attributed to an increase in the oxygen contents in the samples, resulting in a decrease in the number of oxygen vacancy donors in the samples prepared with oxygen pressures higher than 20%. The decrease in the Sn2+ area was related to a decrease in the indium (In) contents in the samples, which also decreased the number of metal acceptors in the samples. XRD also showed that the metallic indium stannide (In0.2Sn0.8) and In–Sn–O(ITO) peaks coexisted for samples prepared with an oxygen pressure of 0–10%. In contrast, the samples prepared with oxygen pressures higher than 20% had an amorphous structure with SnO2 and SnO phases, supporting the XPS and Hall Effect measurement results.

We report that oxygen vacancies have a profound impact on phase separation and thermoelectric properties of ITO films grown at room temperature. Oxygen vacancies in non-stoichiometric In1.8Sn0.2O2.5 films aided the formation of In-rich metallic clusters. It yields a high electrical conductivity σ = 1540 Scm−1 and Seebeck coefficient |α| = 27.2 μVK−1, which resulted in the highest power factor (α2σ = 113.8 μW m−1K−2) but low optical transmission (Top ∼ 25%). An increase in oxygen partial pressure resulted in stochiometric In1.8Sn0.2O3 films which improved the optical transparency by 300% (Top ∼75.4%), but power factor was reduced by ∼85% due to a decrease in α and σ. A decrease in α was due to the lack of energy filtering of charge carriers in the stoichiometric ITO film which did not have In-rich metallic clusters. XPS results showed that the valence band energy shifts with a change in oxygen partial pressure due to a decrease in carrier density, which implied a change in Fermi energy due to the reverse Moss-Burstein effect. Our results showed that phase separation can be obtained in nanocomposite ITO films by tuning their stoichiometry simply by varying the oxygen partial pressure during deposition of thermoelectric materials at low temperatures.

Liquid Li–Pb alloy is served as neutron multiplier, tritium breeder, and coolant in Dual Coolant Lithium–Lead (DCLL) breeding blankets. In order to monitor the tritium transport continuously and measure the tritium production rate accurately, the concentration of hydrogen isotopes in liquid breeder is an essential factor for tritium measurement. The hydrogen isotopes permeation-based capsule seems to be the most reliable sensor and is simple from the fabrication point of view. To verify the stability and repeatability of hydrogen isotopes concentration measured by permeation capsule in Li–Pb, a system based on a Nb-capsule and a quadrupole mass spectrometry was devised. The sensor would be applied to determine the variation rate of total pressure while a quadrupole mass spectrometry to measure partial pressure values of different hydrogen isotopes. The response time of the sensor is less than 100 s in liquid Li–Pb alloy and the growth rate of pressure has good repeatability in dynamic mode. Besides, calculations based on numerical simulation of the hydrogen isotopes sensor are presented.

The experimental results on etching of diamond crystals with octahedral and cubooctahedral habits at a temperature of 1000°С in wet argon are presented. It is found that at a low partial pressure, Н2О can act as an initiator (catalyst) of the surface graphitization of diamonds at the Р–Т-parameters of thermodynamic stability of graphite. The limiting stage of the diamond etching process in the presence of graphite on diamonds is the stage of graphite coating oxidation. Since the outer graphite coating is oxidized, there is no dependence of the etching (oxidation) rate on the morphology of diamond crystals.

Perovskite-like complex oxide La0.5Ca0.5Mn0.5Co0.5O3±δ synthesized by the Pechini method is characterized by X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. Structural transformations of this compound in the media with different partial pressures of oxygen and in the medium with hydrogen are studied in situ for the first time. The solid solution in the medium with low partial pressure of oxygen is shown to be unstable. The structural state of the sample is affected not only by the presence/absence of oxygen in the medium but also by the rate of sample cooling. X-ray diffraction and thermal analysis reveal that perovskite undergoes polymorphic transition from orthorhombic to cubic symmetry at 600 °C due to oxygen loss. Reducing the sample by hydrogen leads to the formation of two perovskite-like phases with pseudo-cubic and orthorhombic symmetries, possibly, due to the inhomogeneous formation of vacancies in the solid solution and changes in the oxidation states of cobalt and manganese cations. It is shown that the initial structure can be partially regenerated from the complex oxide reduced in H2.

The element partitioning in a Pb−Bi concentrate oxygen-rich bath smelting process was studied using thermodynamic equilibrium simulation method. Effects of oxygen to feed ratio (OFR) and sulfur dioxide partial pressure (pSO2) on the partitionings of Bi, Pb, As, Sb, Cu and Ag were analyzed and compared with industrial data. The results suggested that the optimal OFR was between 6.3 and 6.8 kmol/t to maximize Bi, Pb, Cu and Ag partitioning in the metal phase. Further increase of OFR led to the drop of metal partitioning and increase of slag liquidus temperature. High pSO2 led to high deportment of Bi and Pb in the gas phase mainly in the form of sulfides, suggesting that a low pSO2 was conducive for reducing the dust ratio.

The mixed conductive perovskite La1−xCaxFeO3−δ (LCF) exhibits high oxygen permeability. For further improvement of the oxygen permeability as well as the chemical stability, this study investigates the impact of the doping elements on the perovskite B-site. The cobalt (Co) doping of the LCF improved both the oxygen diffusion and the oxygen surface exchange. However, the oxygen semi-permeation flux of the Co-doped LCF sample was not stable at high temperatures under the high oxygen partial pressure difference (air/argon). The magnesium (Mg) doping in the B-site significantly improved the chemical stability of the LCF membranes, with the oxygen semi-permeation performances close to those obtained with the Co-doped LCF membranes. Thus, the Mg-doped LCF presented the best compromise between chemical stability and oxygen semi-permeation performance, which is applicable to the oxygen transport membranes or the cathodes in solid oxide fuel cells.

In this paper, the incorporation of auxiliary grids/electrodes into the design of the sputtering method is scrutinized by studying the impact of factors such as grid size, grid position, grid bias voltage, electrode sheath design, substrate bias voltage, reactive gas partial pressure, and magnetic trap configuration on the discharge condition and thin-film growth. In this regard, utilizing the updated Berg model for reactive sputtering, the authors obtained a formulation for the reactive grid-assisted sputtering. By the newly-developed formulation, the sputtering rate and the reactive gas partial pressure were simulated as a function of the reactive gas flow rate for various grid-to-target distances, argon partial pressures (0.67, 1.6, and 3.6 Pa), and discharge current densities (0.01, 0.015, and 0.02 A/cm2). According to the computation results, with a grid being utilized, the width of the hysteresis loops can be modified in a broader range by changing either the grid-to-target distance, the argon partial pressure, or the discharge current, resulting in better control over the deposition process. Moreover, the novel configuration of anode-spot-assisted sputtering was proposed to significantly ionize sputtered/neutral atoms near the substrate and to simultaneously deposit sputtered species and products produced as the direct result of introducing dust into the dense plasma. Finally, diverse configurations of the grid-assisted co-sputtering method were introduced for two prime purposes: deposition of composite films in any desired ratios of constituents without significantly changing the other co-sputtering parameters, and favorable alternation of a hysteresis loop for one of the guns at shared gas flow rates.

We report a set of compression test experiments carried out on sintered uranium dioxide at 1500 ° C, at constant strain rates and under controlled oxygen partial pressures. The macroscopic data indicate an initial strain hardening stage followed by a quasi steady-state period during which changes in the stress level are sluggish. The data are further interpreted in a continuum mechanics, finite strain framework, in both one and two-dimensional geometries, whence stress and oxygen partial pressure exponents of the creep law are estimated. The stress exponent is indicative of power-law creep. The oxygen partial pressure exponent is consistent with a strain-rate limited by vacancy mediated self-diffusion of the slowest moving ion, suggesting a climb-controlled recovery process. Some samples are further characterized using SEM/EBSD which reveals signs of plastic deformation typical of recovery creep. The effect of oxygen pressure upon microstructure is discussed.

A combination of high-temperature experiments and thermodynamic modeling in the CaO–Cu2O–FeO–Fe2O3–SiO2 system provides the fundamental information necessary to design and improve processes such as WEEE recycling through black copper route, continuous converting of copper matte, copper dross smelting, slag cleaning, and valorization of copper slag. In the experiments, samples were equilibrated on a primary phase substrate or Fe metal foil, then rapidly quenched and studied using the Electron Probe X-ray Microanalysis. The FactSage software was used for calculations, combined with custom developed thermodynamic database. A systematic analysis is provided to select the fluxing strategy and increase the copper recovery in industrial processes. Slag liquidus and concentration of copper in slag were assessed as functions of oxygen partial pressure, temperature, Fe/SiO2 in slag, and wt% CaO in slag.

Previously, we found that the inward diffusion of oxygen from the atmosphere to the interior of vanadium slag (V-slag) has a significant influence on the roasting reaction and may possibly be the dominant mechanism of this reaction. However, the existing reaction mechanism does not reflect the role of oxygen in calcification roasting. In view of this, the proposed study aims to verify the influence of oxygen using the diffusion couple technology, and propose the reaction equations involving oxygen describing the calcium vanadate formation from the surface to the interior of V-slag. The V-slag/CaO diffusion couples were prepared by vacuum hot-pressing, and diffusion experiments were performed under different oxygen partial pressures at a temperature of 1083 K. First, the surfaces in contact with the atmosphere (S(xz)) during roasting were analyzed by electron probe microanalysis (EPMA), Fourier transform-infrared (FT-IR) spectroscopy, and X-ray diffraction (XRD). Then, the diffusion couple was cut along a direction perpendicular to the V-slag/CaO interface and S(xz). The interior surface (S(xy)) was also analyzed by EPMA, FT-IR, and XRD. At S(xz), new phases were clearly observed in the vicinity of V-slag/CaO interface and characterized mainly as CaV2O6, Ca2V2O7, and Ca3V2O8. Moreover, the diffusion thickness of those new phases increased with the oxygen partial pressure. At S(xy), although relatively weak diffraction peaks and absorption bands of CaV2O6, Ca2V2O7, and Ca3V2O8 were detected, no distinct new phases were observed near the V-slag/CaO interface. Considering that the diffusion capacities of Ca and V at S(xz) and S(xy) cannot be evaluated based on the diffusion thickness, the use of interdiffusion coefficient was proposed to quantify the difference among the diffusion capacities. The average interdiffusion coefficients of Ca and V at S(xz) calculated as 1.02 × 10−8 and 0.91 × 10−8 cm2 s−1, respectively, were practically a hundred times these at S(xy). Following the conclusion that the calcium vanadate formation was governed by the inward oxygen diffusion, new reaction equations for describing the formation mechanism of calcium vanadate in calcification roasting were proposed. These equations, derived from the vacancy mechanism, express that the hoses and calcium vanadate are generated by Ca2+, V2O5, and O2.

Oxygen permeability and oxidative coupling of methane (OCM) characteristics of a 30 vol.% NiFe2O4-70 vol.% Gd0.1Ce0.9O2-δ (NFO-GDC) composite membrane were systematically investigated by varying operational conditions for oxygen permeation and OCM experiments. The NFO-GDC membrane showed the maximum oxygen permeation flux of 2.24 mL∙cm−2∙min−1 under an Air/He gradient at 900 °C, and flux increased with increasing oxygen partial pressure gradient in the order He < CH4 < H2. The maximum OCM yield and C2H4/C2H6 ratio were observed at 900 °C and for CH4 flowing at 12.5 mL∙min-1, respectively, and the yield and ratio both increased with increasing temperature in the range 700–900 °C. The overall coupling yield was notably enhanced by applying a Mn/Na2WO4/SiO2 catalyst to the permeate side of the composite membrane. The NFO-GDC membrane with the Mn/Na2WO4/SiO2 catalyst exhibited the maximum yield and a C2H4/C2H6 ratio of 8.6% and 3.21, respectively.