Oxygen Diffusion Research Articles

Ab Initio Investigation of Oxygen Ion Diffusion in the Layered Perovskite System YSr2Cu2FeO7+δ (0 < δ < 1)

Extensive research on transition metal perovskite oxides as electrodes in solid oxide cells (SOC) has highlighted the potential ability of Fe-based perovskite oxides to catalyze oxygen reduction/evolution reactions (ORR/OER). The layered perovskite-type system YSr2Cu2FeO7+δ has been reported to possess attractive electrocatalytic properties. This work applies density functional theory (DFT) calculations to investigate oxygen ion diffusion in the YSr2Cu2FeO7+δ system. For δ = 0.5, it is found that in the most stable configuration, the oxygen vacancies in the FeO1+δ plane are arranged to form Fe ions in tetrahedral, square pyramid, and octahedral coordination. Ab initio molecular dynamics (AIMD) simulations for YSr2Cu2FeO7.5 (δ = 0.5) yield an oxygen ion diffusion coefficient of 1.28 × 10−7 cm2/s at 500 °C (Ea = 0.37 eV). Complementary results for YSr2Cu2FeO7.2 (δ = 0.2) and YSr2Cu2FeO7.75 (δ = 0.75) indicate that the oxygen diffusion occurs in the FeO1+δ plane, and depends on the oxygen vacancies distribution around the Fe centers.

High-temperature oxidation and ablation behavior of (Zr1/3Hf1/3Ti1/3)C ceramic

With the increasing requirements on thermal protection systems of aerospace aircraft, multi-component ultra-high temperature ceramics (MC-UHTCs) are emerging and considered to be candidate materials. In this work, (Zr1/3Hf1/3Ti1/3)C ceramics were prepared by hot pressed sintering, and the behaviors from oxidation to ablation of the ceramics over a wide temperature range was systematically investigated for the first time. The oxidation rate is controlled by oxygen diffusion at initial stage with high activation energy and is slower at lower oxygen partial pressure. The intermediate layer (Zr,Hf,Ti)CxOy, along with the dense oxide layer formed through preferential oxidation, plays a crucial role in hindering oxygen diffusion. Diffusion of Zr, Hf, and Ti elements during oxidation results in Ti enrichment on the ablation surface, enhancing ablation protection. However, high temperatures and prolonged ablation times cause Ti-rich oxides dissipation and significant evaporation of TiO, resulting a porous surface, compromising ablation protection efficacy.

Two-dimensional oxygen-diffusion modelling for FLASH proton therapy with pencil beam scanning—Impact of diffusive tissue properties, dose, dose rate and scan patterns

Objective. Oxygen depletion is generally believed to play an important role in the FLASH effect—a differential reduction of the radiosensitivity of healthy tissues, relative to that of the tumour under ultra-high dose-rate (UHDR) irradiation conditions. In proton therapy (PT) with pencil-beam scanning (PBS), the deposition of dose, and, hence, the degree of (radiolytic) oxygen depletion varies both spatially and temporally. Therefore, the resulting oxygen concentration and the healthy-tissue sparing effect through radiation-induced hypoxia varies both spatially and temporally as well. Approach. We propose and numerically solve a physical oxygen diffusion model to study these effects and their dependence on tissue parameters and the scan pattern in pencil-beam delivery. Since current clinical FLASH PT (FLASH-PT) is based on 250 MeV shoot-through (transmission) beams, for which dose and dose rate (DR) hardly vary with depth compared to the variation transverse to the beam axis, we focus on the two-dimensional case. We numerically integrate the model to obtain the oxygen concentration in each voxel as a function of time and extract voxel-based and spatially and temporarily integrated metrics for oxygen (FLASH) enhanced dose. Furthermore, we evaluate the impact on oxygen enhancement of standard pencil-beam delivery patterns and patterns that were optimised on dose-rate. Our model can contribute to the identification of tissue properties and pencil-beam delivery parameters that are critical for FLASH-PT and it may be used for the optimisation of FLASH-PT treatment plans and their delivery. Main results. (i) the diffusive properties of oxygen are critical for the steady state concentration and therefore the FLASH effect, even more so in two dimensions when compared to one dimension. (ii) The FLASH effect through oxygen depletion depends primarily on dose and less on other parameters. (iii) At a fixed fraction dose there is a slight dependence on DR. (iv) Scan patterns optimised on DR slightly increase the oxygen induced FLASH effect. Significance. To our best knowledge, this is the first study assessing the impact of scan-pattern optimization (SPO) in FLASH-PT with PBS on a biological FLASH model. While the observed impact of SPO is relatively small, a larger effect is expected for larger target volumes. A better understanding of the FLASH effect and the role of oxygen (depletion) therein is essential for the further development of FLASH-PT with PBS, and SPO.

Unique myoglobin adaptation to endothermy and flight since the origin of birds.

Myoglobin (Mb) mediates oxygen diffusion and storage in muscle tissue and thus is important for the energy utilization and activity of animals. Birds generally have a high body temperature, and most species also possess the capability of powered flight. Both of these require high levels of aerobic metabolism. Within endothermic mammals, bats also independently evolved flight. Although the functional evolution of myoglobins in deep-diving amniote vertebrates has been well-studied, the functional evolution of myoglobin since the origins of both birds and bats is unclear. Here, with Mb-coding sequences from >200 extant amniote species, we reconstructed ancestral sequences to estimate the functional properties of myoglobin through amniote evolution. A dramatic change in net surface charge on myoglobin occurred during the origin of Aves, which might have been driven by positively selected amino acid substitutions that occurred on the lineage leading to all birds. However, in bats, no change in net surface charge occurred and instead, the Mb genes show evidence of strong purifying selection. The increased net surface charge on bird myoglobins implies an adaptation to flight-related endothermic and higher body temperatures, possibly by reducing harmful protein aggregations. Different from the findings of net surface charge, myoglobins of extant birds show lower stability compared with other amniotes, which probably accelerates the rate of oxygen utilization in muscles. In bats and other mammals, higher stability of Mb may be an alternative pathway for adaptation to endothermy, indicating divergent evolution of myoglobin in birds and bats.

Solution-plasma treatment for synthesizing Ketjenblack-supported Pt (1 1 1) nanocatalysts with ultra-low overpotential for Li-O2 batteries

Reducing the loading of noble metals to achieve high catalytic activity is key to enhancing the performance and reducing the cost of lithium-oxygen (Li-O2) batteries. In this study, a highly dispersed platinum (111) catalyst supported on Ketjenblack (p-Pt/KBs) is synthesized using a novel approach that involves the interaction between solution and nonthermal plasma (SNP). The influence of different glow discharge voltages on morphology and performance of catalytic materials is investigated. The results show that the electrocatalyst prepared at 400 V has uniform Pt (111) nanocrystals embedded on Ketjenblack, achieved through plasma-induced decomposition of H2PtCl6 followed by nucleation and growth. The designed catalyst, when used as the cathode catalyst in Li-O2 batteries, demonstrates lower polarization losses with an overall overpotential of only 0.24 V compared to commercial platinum on carbon (Pt/C). The plasma effect results in significantly increased defects and grafted oxygen-containing functional groups on the support surface, providing abundant active sites conducive to anchoring of Pt nanoparticles (NPs) onto the scaffold and promoting their electronic coupling. Moreover, dominant mesopores offer ample triple-phase active zones that facilitates lithium-ion transport and rapid oxygen diffusion, further lowering energy barrier for Li2O2 decomposition and reducing the charge overpotential.

Oxidation behavior and corrosion resistance of CoCrFeNi high entropy alloy compared with FeCoNi medium entropy alloy

The entropy-based alloy with excellent oxidation and corrosion resistance is of great significance for practical applications in high-temperature environments. Thus, the difference in anti-oxidation property and corrosion behavior of FeCoNi MEA and CoCrFeNi HEA in a simulated marine environment was studied via a series of measurements. The results reveal that the HEA possesses superior oxidation and corrosion resistance in comparison with the MEA, which can be demonstrated by comparing the oxidation rate and thickness of oxide layer, corrosion current density (icorr) as well as corrosion morphology after polarization. The microstructure and composition of the oxide layer are the primary reasons resulting in the difference of oxidation and corrosion behaviors of the two alloys. The oxide layer with a compact, even and intact structure is produced on the HEA surface, which hinders the diffusion of detrimental ions and oxygen, whereas the loose, porous and cracked oxide layer consisting of inner Fe3O4 and outer CoO exhibits poor protection against corrosion and oxidation of the MEA. For the HEA, the preferential combination of Cr and O elements forms the protective oxide of Cr2O3, effectively enhancing corrosion resistance and inhibiting oxidation. However, the low protective CoO and relatively active Fe3O4 grow on the MEA surface, which cannot provide a good barrier to restrain oxidation and corrosion.

Bimodal Trending in Corrosion Loss of Magnesium Alloys

Data for the mass loss of a variety of magnesium alloys as a function of an exposure period show that corrosion loss follows bimodal trending with time for different exposure environments, with both laboratory and field supporting these findings. For datasets sufficient to discriminate bimodal behavior, the instantaneous rate of corrosion at the commencement of the second mode is (close to) four times the instantaneous rate of corrosion at the end of the first mode (i.e., through the transition period). This observation is consistent with the theoretical relative diffusivities of oxygen and hydrogen through the corrosion product layer as it exists during the transition period. These findings support the notion that the bimodal model has corrosion in mode 1 rate-controlled by the cathodic oxygen reduction reaction and the inward diffusion of oxygen while in mode 2 corrosion is rate-controlled by the cathodic hydrogen evolution reaction and the outward diffusion of hydrogen. Similar findings have been made previously for various ferrous and other alloys and thus throws new light on the development of corrosion of magnesium alloys. It also provides reasons for measurements of hydrogen evolution and electrochemical techniques underestimating magnesium corrosion rates. A new procedure for combining these is proposed.

Encapsulated Pd clusters in S-1 promote the reactivity of chemical looping via synergistic effect of catalysis and oxygen storage

Chemical looping reforming of CH4 coupled with CO2 reduction technology offers a compelling way for effective CO2 emission with the production of syngas and CO. However, the reaction temperature in chemical looping is relatively higher (>800 °C). To solve this problem, it is critical to explore efficient oxygen carriers. In this work, 3DOM LF0.85N0.15/Pd@S-1 oxygen carrier with hierarchical pore structure obtained high reactivity. 3DOM LF0.85N0.15/Pd@S-1 contained three major components, playing different roles. The 3DOM LF0.85N0.15 with ordered macroporous structure possessed excellent oxygen storage capacity and diffusion property. Pd clusters as active sites promoted CH4 activation and strengthen Lewis acid sites. Silicalite-1 zeolite, with larger surface area and well-defined microporous structure, exhibited superior adsorption properties and used as an ideal support to encapsulate Pd clusters. The well-dispersed Pd clusters further strengthened the reducibility at low temperature. Among all samples, 3DOM LF0.85N0.15/Pd@S-1 exhibited highest reactivity and stability during the successive chemical looping.

Prevention of morphological change for (Ba,Sr)(Co,Fe)O3 cathodes by incorporating (Ce,Gd)O2 for intermediate-temperature solid oxide fuel cells

Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) generally exhibits superior cathode activity compared to La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) for intermediate-temperature solid oxide fuel cells (IT-SOFCs). However, the chemical stability of BSCF is inferior to that of LSCF. When BSCF cathodes are sintered at a high temperature of 1050 °C, performance was compromised due to the formation of (Ba,Sr)ZrO3 between the scandia-stabilized zirconia (ScSZ) electrolyte and gadolinia-doped ceria (GDC) interlayer. The oxide ionic conductivity of (Ba,Sr)ZrO3 was low, decreasing the cathode performance. Furthermore, the BSCF grains enlarged, and cobalt oxide formed due to BSCF decomposition, decreasing the active specific surface area. However, by incorporating GDC into the BSCF cathode, the morphology remained unchanged and cobalt oxide formation was prevented, despite (Ba,Sr)ZrO3 still forming. The performance of the cell with the BSCF-GDC composite cathode surpassed that with the BSCF cathode due to decreased polarization resistance attributed to the oxygen surface exchange and diffusion processes in the cathode.

Unveiling microplastic's role in nitrogen cycling: Metagenomic insights from estuarine sediment microcosms

Marine microplastics (MPs) pollution, with rivers as a major source, leads to MPs accumulation in estuarine sediments, which are also nitrogen cycling hotspots. However, the impact of MPs on nitrogen cycling in estuarine sediments has rarely been documented. In this study, we conducted microcosm experiment to investigate the effects of commonly encountered polyethylene (PE) and polystyrene (PS) MPs, with two MPs concentrations (0.3% and 3% wet sediment weight) based on environmental concentration considerations and dose-response effects, on sediment dissolved oxygen (DO) diffusion capacity and microbial communities using microelectrode system and metagenomic analysis respectively. The results indicated that high concentrations of PE-MPs inhibited DO diffusion during the mid-phase of the experiment, an effect that dissipated in the later stages. Metagenomic analysis revealed that MP treatments reduced the relative abundance of dominant microbial colonies in the sediments. The PCoA results demonstrated that MPs altered the microbial community structure, particularly evident under high concentration PE-MPs treatments. Functional analysis related to the nitrogen cycle suggested that PS-MPs promoted the nitrification, denitrification, and DNRA processes, but inhibited the ANRA process, while PE-MPs had an inhibitory effect on the nitrate reduction process and the ANRA process. Additionally, the high concentration of PE-MPs treatment significantly stimulated the abundance of genus (Bacillus) by 34.1% and genes (lip, pnbA) by 100–187.5% associated with plastic degradation, respectively. Overall, in terms of microbial community structure and the abundance of nitrogen cycling functional genes, PE- and PS- MPs exhibit both similarities and differences in their impact on nitrogen cycling. Our findings highlight the complexity of MP effects on nitrogen cycling in estuarine sediments and high concentrations of PE-MP stimulated plastic-degrading genus and genes.

Selective atomic sieving across metal/oxide interface for super-oxidation resistance

Surface passivation, a desirable natural consequence during initial oxidation of alloys, is the foundation for functioning of corrosion and oxidation resistant alloys ranging from industrial stainless steel to kitchen utensils. This initial oxidation has been long perceived to vary with crystal facet, however, the underlying mechanism remains elusive. Here, using in situ environmental transmission electron microscopy, we gain atomic details on crystal facet dependent initial oxidation behavior in a model Ni-5Cr alloy. We find the (001) surface shows higher initial oxidation resistance as compared to the (111) surface. We reveal the crystal facet dependent oxidation is related to an interfacial atomic sieving effect, wherein the oxide/metal interface selectively promotes diffusion of certain atomic species. Density functional theory calculations rationalize the oxygen diffusion across Ni(111)/NiO(111) interface, as contrasted with Ni(001)/NiO(111), is enhanced. We unveil that crystal facet with initial fast oxidation rate could conversely switch to a slow steady state oxidation.

Low-cycle fatigue behavior of coated and uncoated single crystal Ni-based superalloy at various temperatures

Within this work, the effect of different oxidation-resistant coatings on the low-cycle fatigue (LCF) behavior and damage mechanisms of third-generation single crystal (SC) Ni-based superalloy was investigated. Stress-controlled LCF tests of bare alloy, MCrAlY-coated and PtAl-coated thin-walled specimens were carried out at 760 °C, 850 °C and 980 °C. A unique clamping system was meticulously designed to overcome the clamping challenge in high-temperature furnaces. The cracking behaviors and failure modes were determined by advanced microstructure characterization. The results show that the coatings are detrimental to the LCF lifetime of thin-walled specimens, especially at low-medium temperatures of 760 °C and 850 °C. For bare alloy, the tip cracks nucleate from the surface oxide layer, whereas cracks in the coating-substrate system nucleate prematurely from the coating surface and propagate to the substrate. The oxygen diffusion and the frontward propagation of cracks are synergistically enhanced in the SC substrate, resulting in oxidation-assisted crack propagation and ultimate failure. Finally, A fatigue life prediction model is proposed by introducing coating-induced crack initiation and oxidation effects, where the predictive results fit well with experimental results. This study provides a comprehensive insight into the damage mechanisms and coating-induced LCF life degradation of the coating-substrate system.

Quantitative Volumetric Analysis of Retinal Ischemia with an Oxygen Diffusion Model and OCT Angiography

PurposeRetinal ischemia is a major feature of diabetic retinopathy (DR). Traditional nonperfused areas measured by optical coherence tomography angiography (OCTA) measure blood supply but not ischemia. We propose a novel 3-dimensional (3D) quantitative method to derive ischemia measurements from OCTA data. DesignCross-sectional study. ParticipantsWe acquired 223 macular OCTA volumes from 33 healthy eyes, 33 diabetic eyes without retinopathy, 7 eyes with non-referable DR, 17 eyes with referable but non-vision-threatening DR, and 133 eyes with vision-threatening DR. MethodsEach eye was scanned using a spectral-domain OCTA system (Avanti RTVue-XR, Visionix/Optovue, Inc) with 1.6 mm scan depth in a 3 × 3-mm region (640 × 304 × 304 voxels) centered on the fovea. For each scanned OCTA volume, a custom algorithm removed flow projection artifacts. We then enhanced, binarized, and skeletonized the vasculature in each OCTA volume and generated a 3D oxygen tension map using a zero-order kinetics oxygen diffusion model. Each volume was scaled to the average retina thickness in healthy controls after foveal registration and flattening of the Bruch membrane. Finally, we extracted 3D ischemia maps by comparison with a reference map established from scans of healthy eyes using the same processing. To assess the ability of the ischemia maps to grade DR severity, we constructed receiver-operating characteristic (ROC) curves for diagnosing diabetes, referable DR, and vision-threatening DR. Main outcome measuresSpearman correlation coefficient and area under ROC curve (AUC) were used to quantify the ability of the ischemia maps to DR. ResultsThe ischemia maps showed that the ischemic tissues were at or near pathologically non-perfused areas, but not the normally non-vascular tissue, such as the foveal avascular zone. We found multiple novel metrics, including inferred 3D-oxygen tension, ischemia index, and ischemic volume ratio, were strongly correlated with DR severity. The AUCs of ischemia index measured were 0.95 for diabetes, 0.89 for DR, 0.88 for referable DR, and 0.85 for vision threatening DR. ConclusionsA quantitative method to infer 3D oxygen tension and ischemia using OCTA in diabetic eyes can identify ischemic tissue that are more specific to pathologic changes in DR.

Temporal Evolution of Defects and Related Electric Properties in He-Irradiated YBa2Cu3O7-δ Thin Films.

Thin films of the superconductor YBa2Cu3O7-δ (YBCO) were modified by low-energy light-ion irradiation employing collimated or focused He+ beams, and the long-term stability of irradiation-induced defects was investigated. For films irradiated with collimated beams, the resistance was measured in situ during and after irradiation and analyzed using a phenomenological model. The formation and stability of irradiation-induced defects are highly influenced by temperature. Thermal annealing experiments conducted in an Ar atmosphere at various temperatures demonstrated a decrease in resistivity and allowed us to determine diffusion coefficients and the activation energy ΔE=(0.31±0.03) eV for diffusive oxygen rearrangement within the YBCO unit cell basal plane. Additionally, thin YBCO films, nanostructured by focused He+-beam irradiation into vortex pinning arrays, displayed significant commensurability effects in magnetic fields. Despite the strong modulation of defect densities in these pinning arrays, oxygen diffusion during room-temperature annealing over almost six years did not compromise the signatures of vortex matching, which remained precisely at their magnetic fields predicted by the pattern geometry. Moreover, the critical current increased substantially within the entire magnetic field range after long-term storage in dry air. These findings underscore the potential of ion irradiation in tailoring the superconducting properties of thin YBCO films.

High‐temperature oxidation and TGO growth behavior of Sr.9(Zr.9Yb.05Y.05)O2.85 thermal barrier coatings

AbstractHigh‐temperature oxidation (1050°C) of Sr.9(Zr.9Yb.05Y.05)O2.85 (SZYY) thermal barrier coatings (TBCs) by suspension plasma spraying (SPS) and growth behavior of thermally grown oxide (TGO) were investigated. When the TBCs were exposed to high temperature for a period of time (∼5 h), the BC oxidized and TGO inevitably formed between the bond coating (BC) and the ceramic top coating (TC). The high‐temperature oxidation behavior of the BC is generally manifested as the growth of TGO, which has four specific stages as follows: (1) formative oxidation stage (0‒10 h), (2) rapid oxidation stage (10‒50 h), (3) stable oxidation stage (50‒100 h), and (4) complex oxidation stage (100‒200 h). The main component of early TGO is α‐Al2O3. It has a very low oxygen ion diffusivity and provides an excellent diffusion barrier, which has a positive effect on preventing further BC oxidation. However, as the heat treatment time increased, the Al consumption and the formation of a CNS layer (NiO, Co3O4, and spinel) in the BC eventually led to coating failure. The working life of TBCs can be improved by improving the ceramic TC structure and the Al content of BC. SZYY‐TBCs have certain potential application value.

Influence of Oxygen Vacancies Introduced via Acceptor (Gadolinium) Doping to the Pseudocapacitive Properties of Nano-Sized Cerium Oxide.

The voluntary introduction of defects can be considered an effective strategy for enhancing the electrochemical properties of metal oxide electrodes. In this study, the enhanced pseudocapacitive properties of an acceptor (Gd) doped cerium oxide nanoparticle-a sustainable metal oxide with low environmental and human toxicity-are investigated in depth using ex situ X-ray photoemission spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). Interestingly, with 15at% Gd doping (15GDC), the specific capacitance of the nanoparticles measured at 1Ag-1 enhanced to 547.8Fg-1, which is fivefold higher than undoped CeO2 (98.7Fg-1 at 1Ag-1). The rate-dependent capacitance is also improved for 15GDC, which showed a 31.0% decrease in the specific capacitance upon a tenfold increase in the current density, while CeO2 showed a 49.9% decrease. The enhanced electrochemical properties are studied in depth via ex situ XPS and EIS analysis, which revealed that the oxygen vacancies at the surface of the nanoparticles played important roles in enhancing both the specific capacitance and the high-rate performance of 15GDC by acting as the active site for pseudocapacitive redox reaction and allowing fast diffusion of oxygen ions at the surface of 15GDC nanoparticles.

Microencapsulation of tomato oleoresin using tomato waste fibre and its application for orange juice fortification

SummaryFood waste by‐products contain many bioactive compounds, such as proteins, carbohydrates, polyphenols and carotenoids. The purposes of this study was to extract oleoresin from tomato waste, apply tomato pomace powder (TPP) as a new shell material for encapsulation of oleoresin and to fortify orange juice using the developed microcapsules. Microencapsulation was carried out based on different TPP (2% and 3%) and oleoresin (20% and 30%) concentrations by spray drying at two temperatures (130 and 140 °C). Different features of microcapsules such as the encapsulation load, encapsulation efficiency, moisture content, hygroscopicity, bulk and tapped densities and the Hausner ratio were analysed. Based on properties of microcapsules, samples containing 3% TPP and 30% oleoresin dried at 130 °C were selected as the best treatment and their characteristics such as morphology, chemical structure and thermal behaviour were investigated. Scanning electron microscopy indicated that spherical micron‐size particles were formed and their crack‐free fine surface showed their potential for encapsulation of anti‐oxidants to reduce oxygen diffusion. Microencapsulated oleoresin was then added to the orange juice and the samples' pH, acidity, total soluble solids and colour were evaluated and compared with pure orange juice. Free radical scavenging method was used to investigate the anti‐oxidant properties of orange juice during storage. The results indicated that at the end of the 30 days of storage the fortified orange juice had anti‐oxidant activity equal to pure fresh orange juice on day one. Sensory evaluation results showed no significant differences between appearance, colour, thickness and overall acceptance of fresh and the fortified juices (P < 0.05). The results of this study showed the potential application of food and agricultural waste in production of value‐added ingredients to be used as natural additives in food industries.

Tailoring oxidation resistance of Cantor alloy by addition of Ta and Al

High-entropy alloys are widely investigated for applications in the nuclear engineering field, the aerospace sector, and various other high-temperature applications. High-temperature oxidation behaviour is a typical issue in such applications. In the current work, an effort is made to tailor the oxidation behaviour of Cantor alloy (CoCrFeMnNi) in the air at 1000 °C with the addition of Ta and Al. Both CoCrFeMnNiTa as well as CoCrFeMnNiAl alloys exhibit considerable resistance to oxide scale spallation as well as develop multi-layered complex oxide scales. CoCrFeMnNiTa primarily forms rutile-type CrTaO4 oxide, which drastically reduces the inward diffusion of oxygen and nitrogen and suppresses the escape of other alloying elements. Nonetheless, the better result is obtained through the Al addition, as evidenced by the comparatively lower oxidation rate constant of CoCrFeMnNiAl in comparison to CoCrFeMnNiTa alloy. This is attributed to the superior oxidation resistance for CoCrFeMnNiAl could be related to the emergence of distinctive Cr2O3 and Al2O3 scales. Additionally, the oxide scale of CoCrFeMnNiTa was not completely smooth and showed some spallation whereas the oxide scales of CoCrFeMnNiAl remained smooth, continuous, and had stronger oxide-substrate interface adhesion.

Triphasic Oxygen Storage in Wet Nanoparticulate Polymer of Intrinsic Microporosity (PIM-1) on Platinum: An Electrochemical Investigation.

The triphasic interaction of gases with electrode surfaces immersed in aqueous electrolyte is crucial in electrochemical technologies (fuel cells, batteries, sensors). Some microporous materials modify this interaction locally via triphasic storage capacity for gases in aqueous environments linked to changes in apparent oxygen concentration and diffusivity (as well as activity and reactivity). Here, a nanoparticulate polymer of intrinsic microporosity (PIM-1) in aqueous electrolyte is shown to store oxygen gas and thereby enhance electrochemical signals for oxygen reduction in aqueous media. Oxygen reduction current transient data at platinum disk electrodes suggest that the reactivity of ambient oxygen in aqueous electrolyte (typically Doxygen = 2.8 × 10-9 m2 s-1; coxygen = 0.3 mM) is substantially modified (to approximately Dapp,oxygen = 1.6 (±0.3) × 10-12 m2 s-1; capp,oxygen = 50 (±5) mM) with important implications for triphasic electrode processes. The considerable apparent concentration of oxygen even for ambient oxygen levels is important. Potential applications in oxygen sensing, oxygen storage, oxygen catalysis, or applications associated with other types of gases are discussed.

Two-Dimensional Metal-Organic Frameworks/Epoxy Composite Coatings with Superior O2/H2O Resistance for Anticorrosion Applications.

Corrosion protection technology plays a crucial role in preserving infrastructure, ensuring safety and reliability, and promoting long-term sustainability. In this study, we combined experiments and various analyses to investigate the mechanism of corrosion occurring on the epoxy-based anticorrosive coating containing the additive of two-dimensional (2D) and water-stable zirconium-based metal-organic frameworks (Zr-MOFs). By using benzoic acid as the modulator for the growth of the MOF, a 2D MOF constructed from hexazirconium clusters and BTB linkers (BTB = 1,3,5-tri(4-carboxyphenyl)benzene) with coordinated benzoate (BA-ZrBTB) can be synthesized. By coating the BA-ZrBTB/epoxy composite film (BA-ZrBTB/EP) on the surface of cold-rolled steel (CRS), we found the lowest coating roughness (RMS) of BA-ZrBTB/EP is 2.83 nm with the highest water contact angle as 99.8°, which represents the hydrophobic coating surface. Notably, the corrosion rate of the BA-ZrBTB/EP coating is 2.28 × 10-3 mpy, which is 4 orders of magnitude lower than that of the CRS substrate. Moreover, the energy barrier for oxygen diffusion through BA-ZrBTB/EP coating is larger than that for epoxy coating (EP), indicating improved oxygen resistance for adding 2D Zr-MOFs as the additive. These results underscore the high efficiency and potential of BA-ZrBTB as a highly promising agent for corrosion prevention in various commercial applications. Furthermore, this study represents the first instance of applying 2D Zr-MOF materials in anticorrosion applications, opening up new possibilities for advanced corrosion-resistant coatings.