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[Display omitted] • A novel ZnCoAl-LDH/Ti-Fe 2 O 3 photoanode is designed and constructed. • The ZnCoAl-LDH/Ti–Fe 2 O 3 photoanode achieved a photocurrent density of 3.51 mA/cm2 at 1.23 V vs. RHE. • The separation and transport behavior of photogenerated charges was investigated. • The synergistic effects among the three metals were revealed. The efficiency of photoelectrochemical (PEC) water splitting is hindered by the slow kinetics of the oxygen evolution reaction (OER). This study developed a composite photoanode for water oxidation by incorporating ternary LDHs (ZnCoAl-LDH) onto Ti-Fe 2 O 3 as a cocatalyst. The ZnCoAl-LDH/Ti–Fe 2 O 3 photoanode achieved a photocurrent density of 3.51 mA/cm2 at 1.23 V vs. RHE, which is 9.8 times higher than that of bare Ti-Fe 2 O 3. Through a series of characterizations, the synergistic effects among the three metals were revealed. Furthermore, the addition of Zn can induce the formation of more high-valent Co, increasing the conductivity of CoAl-LDH and significantly reducing the surface charge transfer resistance. These advantages significantly enhance the injection efficiency of ZnCoAl-LDH/Ti-Fe 2 O 3 (82 %), thereby accelerating the OER kinetics of Ti-Fe 2 O 3. Our work introduces new approaches for selecting photoelectrochemical cocatalysts and designing high-performance photoanodes for water splitting. [ABSTRACT FROM AUTHOR]

A Solar Corrosion Fenton reactor (SCFr) was developed by packing an iron-carbon steel filament inside the reactor to enable the in situ release of Fe2+. A Box–Behnken experimental design was used to optimize the effect of HRT (20, 30, and 40 min), the mass ratios of the packed filament inside the reactor with respect to volume (0.1, 0.2, 0.3 w/v), and the peroxide dosage added (500, 1000, and 1500 mg/L), the response variables were the percentage removal of COD, color, and turbidity. The optimum conditions for SCFr were an HRT of 24.5 min, a ratio of 0.16 (0.0032 m2/L), and a peroxide dose of 1006.9 mg/L. The removal was 91.8%, 98.4%, and 87.3% COD, color, and turbidity, respectively. Without solar radiation, the percentage removal was reduced by 16.3%, 47.9%, and 34.0% in terms of COD, color, and turbidity, respectively. The concentration of Fe2+ released was 25.4 mg/L of Fe2+. Prolonged HRT increases Fe2+ concentration and turbidity, which increase COD. The oxidation kinetics were fitted to a Behnajady–Modirshahla–Ghanbery (BMG) model, which indicated a high oxidation rate that is reflective of low treatment times. The w/v ratio was the most significant factor; the release of Fe2+ was stimulated by UV radiation and the chloride concentration of wastewater, which prevents the formation of an oxide layer, thus allowing its continuous release, taking advantage of solar radiation and the pH and chloride concentration of the raw sample. [ABSTRACT FROM AUTHOR]

Oxidation resistance is crucial to the potential applications of high‐entropy carbides (HECs) at elevated temperatures. Here, we realize the exploration of (Hf, Ta, Zr, Cr)C high‐entropy carbides (HEC‐TM, TM = Hf, Zr, Ta, and Cr) with good oxidation resistance by optimizing their compositions. To be specific, 21 kinds of HEC‐xTM (x = 0–25 mol%) samples are fabricated by a high‐throughput ultrafast high‐temperature sintering technique, followed by oxidation testing at 1673 K for 30 min. Among all the HEC samples, the as‐fabricated HEC‐0Zr samples are proved to possess the best oxidation resistance with an oxidation depth of only 53 µm. Further study on isothermal oxidation kinetics demonstrates that the as‐fabricated HEC‐0Zr samples follow a linear oxidation law. The good oxidation resistance of the as‐fabricated HEC‐0Zr samples is believed to result from the (Ta, Me)2O5 phase with a low melting point, which can promote the densification of the oxide layer. This research opens up a new way for efficiently discovering new HECs for extreme applications. [ABSTRACT FROM AUTHOR]

High‐activity TiB2 submicron powders were synthesized via microwave‐assisted carbothermal reduction, and their oxidation behavior at 550°C–1000°C for 0.5–1.5 h in air atmosphere was carried out by the isothermal oxidation test. The phase composition and microstructure evolution of the oxidation products were performed by X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). It was established that TiB2 submicron powders had been significantly oxidized at 550°C, and the oxidation products were TiO2 and B2O3. Hexagonal plate‐like TiB2 grains had been completely disappeared, and fragmented into uniform nano‐scale spherical TiO2 particles after being oxidized at 1000°C for 1 h, accompanied by the violent evaporation of B2O3 products at temperatures above 1000°C. In addition, the corresponding oxidation kinetics was investigated by using a non‐isothermal thermogravimetric (TG)–differential scanning calorimetry (DSC) technique. The results showed that the Mample power law (n = 1) was the most probable mechanism function, and the oxidation activation energy E of TiB2 submicron powders was 640.58 kJ/mol. [ABSTRACT FROM AUTHOR]

Iron–nickel-based superalloy is an ideal substitute for the expensive Inconel 625 and Inconel 751 alloys. To elucidate the evolution of the microstructure and properties of Ni30 alloy under different thermal treatment conditions, a systematic study was conducted on the microstructural transformation of the alloy's strengthening γ′ phase following solution treatment and aging, as well prolonged exposure at 750 °C, and the oxidation behavior of the Ni30 alloy was examined. During prolonged thermal exposure, grain growth occurs mainly in the initial stage, and after 200 h, the prolonged exposure time leads to a significant coarsening of γ′ precipitates, whose area fraction increases by more than 10 times compared to their unaged state. After 100 h of aging, the alloy reaches a peak tensile strength of 1270 MPa and a yield strength of 820 MPa; after 2000 h, the alloy maintains a relatively high strength with a slight decrease in ductility. The oxidation kinetic curve of Ni30 alloy follows the quasi-parabolic oxidation law at 750 °C, and its oxidation rate is consistently lower than 0.1 g·m−2·h−1 throughout the whole oxidation process, which indicates that it has excellent oxidation resistance. The external oxide layer of Ni30 alloy shows a bilayered structure, and no obvious surface porosity or flaking of oxidation products were observed throughout the high-temperature oxidation test. This study not only contributes to the improvement of material properties, but also promotes innovation and development in the field of high-temperature engineering applications that will help to meet the increasingly stringent requirements of high-temperature working environments. [ABSTRACT FROM AUTHOR]

Highlights: This review provides a comprehensive overview of the current research progress on metal–carbon dioxide (M-CO2) batteries across a broad temperature range (from room temperature to low/high temperatures). The challenges encountered by M-CO2 batteries under extreme low- and high-temperature conditions thoroughly discussed, along with strategies to address these challenges. The potential application scenarios and future directions of M-CO2 batteries across a broad temperature range are highlighted. The metal–carbon dioxide batteries, emerging as high-energy–density energy storage devices, enable direct CO2 utilization, offering promising prospects for CO2 capture and utilization, energy conversion, and storage. However, the electrochemical performance of M-CO2 batteries faces significant challenges, particularly at extreme temperatures. Issues such as high overpotential, poor charge reversibility, and cycling capacity decay arise from complex reaction interfaces, sluggish oxidation kinetics, inefficient catalysts, dendrite growth, and unstable electrolytes. Despite significant advancements at room temperature, limited research has focused on the performance of M-CO2 batteries across a wide-temperature range. This review examines the effects of low and high temperatures on M-CO2 battery components and their reaction mechanism, as well as the advancements made in extending operational ranges from room temperature to extremely low and high temperatures. It discusses strategies to enhance electrochemical performance at extreme temperatures and outlines opportunities, challenges, and future directions for the development of M-CO2 batteries. [ABSTRACT FROM AUTHOR]

In coal mining areas, the ambient atmospheric and aqueous oxidation of pyrite minerals (FeS2) associated with coal as well as the other accompanying strata is significant in understanding the extent of acid mine drainage (AMD), the cause of severe environmental pollution. Therefore, in this paper, the oxidation kinetics of the coal-associated pyrite (CAPy) present in a coal sample (TpHM1) has been studied via aqueous leaching depyritization experiments at variety of temperatures and time intervals without the incorporation of any oxidizer. The outcomes obtained are juxtaposed with the standard pyrite mineral (SPM) oxidation at the same experimental conditions. Also, the coal and SPM slurry residues and filtrates obtained after aqueous leaching at 25 °C and 90 °C for 0 h and 24 h, respectively, were extensively analyzed through high-resolution transmission electron microscopy (HR-TEM), Powder X-ray diffraction (P-XRD), and X-ray-photoelectron spectroscopy (XPS) for evaluation of the mineralogical composition and proportions of iron and sulfur components during progression of the oxidation reaction. Both the reactions obey pseudo first-order kinetics during pyrite (FeS2) oxidation but a significant difference in the experimentally found activation energies (Ea) and rate constants (k) values of oxidation kinetics of both CAPy and SPM may be attributed to the varied geochemical compositions of the coal associated pyrite (CAPy). The rate constant for CAPy is much greater than that of SPM implying a higher Ea around 10.838 kJ/mol for SPM as compared to 1.941 kJ/mol for CAPy. The CAPy in coal (TpHM1) is more susceptible to atmospheric oxidation than that of SPM, leading to the formation of acid mine drainage with lower pH. In this paper, the pH values on the basis of stoichiometric pyrite oxidation reaction were calculated and compared with the pH values obtained after aqueous leaching of CAPy to interpret the extent of acid formation and pyrite dissolution. Hence, with the assistance of the current study, further studies on the effects of mineral impurities, whereabouts of pyrite minerals in coal seams, the significance of compositional differences in the CAPy, the effect of metal oxides, and the role of alkalinity producing neutralizing agents of coal in the oxidative dissolution process of pyrite can be investigated. [ABSTRACT FROM AUTHOR]

The effects of varied aging treatments are investigated on microstructure and properties in a ZL702A/SUS304 steel bimetal. Si and Al2Cu precipitates are detected in aluminum matrix after peak aging at 80 °C, 120 °C, and 160 °C, all of which yield close hardness within 77 ~ 79 HV. Notably, 80 °C peak aging produces finer, denser, and more uniform precipitates, stemming from the better thermodynamic and kinetic precipitation conditions. A thin oxidation layer is generated at AlFe(Si) transition layer/steel matrix interface after solid solution treatment. The layer remains in thinness (< 1 μm) under 80 °C peak aging but seriously thickens under 120 °C (avg. 16.2 μm) and 160 °C (avg. 12.9 μm), ascribed to the varied diffusion and oxidation kinetics. This generates higher average shear strength of 38.2 MPa in former than that of 28.5 MPa in latter. Fractography indicate fracture under shear loading propagates at thin oxidation layer and occasionally to steel side in 80 °C low temperature bimetal, relieving the devastating fracturing completely through thick fragile oxidation layer in 120 °C and 160 °C peak-aged ones. This work highlights low temperature aging strategy for fine precipitation hardening in aluminum and meantime maintaining a good interfacial bonding of aluminum/steel bimetal. [ABSTRACT FROM AUTHOR]

The redox state of the plastoquinone (PQ) pool in thylakoids plays an important role in the regulation of chloroplast metabolism. In the light, the PQ pool is mostly reduced, followed by oxidation after light cessation. It has been believed for a long time that dark oxidation depends on oxygen, although the precise mechanisms of the process are still unknown and debated. In this work, we analyzed PQ pool oxidation kinetics in isolated pea (Pisum sativum) thylakoids by tracking the changes in the area above the OJIP fluorescence curve (Afl) over time intervals from 0.1 s to 10 min in the dark following illumination. Afl served as an indirect measure of the redox state of the PQ pool that enabled quantification of the rate of PQ pool oxidation. The results showed a two-phase increase in Afl. The "fast" phase appeared to be linked to electron flow from the PQ pool to downstream acceptors of the photosynthetic electron transport chain. The "slow" phase involved oxidation of PQH2 through oxygen-dependent mechanisms. Adding octyl gallate, an inhibitor of plastid terminal oxidase (PTOX), to isolated thylakoid suspensions decreased the rate of the "slow" phase of PQ pool oxidation in the dark after illumination. The addition of either H2O2 or catalase, an enzyme that decomposes H2O2, revealed that H2O2 accelerates oxidation of the PQ pool. This indicates that under conditions that favor H2O2 accumulation, H2O2 can contribute substantially to PQ pool oxidation in the dark after illumination. The contribution of PTOX and H2O2 to the modulation of the PQ pool redox state in plants in the dark after illumination is discussed. [ABSTRACT FROM AUTHOR]

The sluggish kinetics of methanol oxidation reaction (MOR) required high‐performing catalysts in the development of direct methanol fuel cells. Herein, a phosphorus‐doped MoO2 nanorods‐supported Pt catalyst was proposed which exhibited remarkably enhanced catalytic performance toward MOR in comparison with Pt/MoO2 and commercial Pt/C. Specifically, the Pt/MoO2‐P possessed the highest peak current density of 62.63 mA cm−2, about 1.38 and 2.21 times higher than that of Pt/MoO2 (45.24 mA cm−2) and Pt/C (28.40 mA cm−2), respectively. Meanwhile, the Pt/MoO2‐P possessed high intrinsic activity expressed by specific activity and mass activity, and largely improved catalytic kinetics. Moreover, the chronoamperometry and CO‐stripping testing successfully revealed the superior stability and CO‐poisoning resistance of Pt/MoO2‐P, rendering Pt/MoO2‐P a promising catalyst for MOR. The theoretical calculation revealed the electron redistribution and strong metal‐support interaction among Pt/MoO2‐P catalysts. The greatly enhanced catalytic performance could be attributed to the heteroatom doping engineering, greatly enhancing the conductivity, and inducing electron redistribution, thereby leading to the strong metal‐support interaction and high CO‐anti poisoning ability. [ABSTRACT FROM AUTHOR]

Electromagnetic wave (EMW) absorbing materials play an increasingly crucial role in mitigating electromagnetic pollution. In this study, the laser‐induced self‐propagating synthesis (LSS) method was employed to successfully produce Al3BC3 powders with a purity of up to 98.8 wt.% using aluminum powder, boron carbide powder, and carbon powder as raw materials. The preparation efficiency was increased by approximately 20–360 times compared to conventional heating methods. Additionally, the as‐synthesized Al3BC3 powder exhibited remarkable oxidation resistance, with an apparent oxidation activation energy (E) of 213.04 kJ/mol and a preexponential factor of 5.38. Moreover, the powder demonstrated superior EMW absorption performance at 973 K, with a reflection loss below –10 dB within the frequency range of 6.74–7.97 GHz and a minimum reflection loss reaching –45.86 dB at a thickness of 2.9 mm. These results suggest that the as‐synthesized Al3BC3 powder is a promising candidates for high‐temperature EMW absorption applications. [ABSTRACT FROM AUTHOR]

A pulsed electrodeposition was performed on mild steel surfaces to prepare Ni-W-based composite coatings consisting of TiO2 and ZrO2 oxide nanoparticles. To evaluate the oxidative properties of coatings, isothermal oxidation studies were performed on the coatings at 873, 973, and 1073 K in the air for 30 h. The coatings' phase evolution, morphology, and chemistry were investigated by x-ray diffraction, field emission scanning electron microscopy, and energy-dispersive spectroscopy, respectively. As a result of examining the microstructure changes after the oxidation test, it was found that the oxide formation increased according to the oxidation temperature. To determine the oxidation kinetics of the respective coatings, Arrhenius plots were drawn and activation energies were calculated. The final results confirmed that the oxidation resistance of the Ni-W-TiO2-ZrO2 nanocomposite coatings (NiWNC) increased with the addition of ZrO2 (0 − 15 g/L). In this study, better oxidation resistance was observed for the Ni-W-5 g/L TiO2-15 g/L ZrO2 nanocomposites compared to the rest of the coatings. These findings highlight the potential of producing highly oxidation-resistant coatings using a cost-effective method on commercially available metal surfaces such as mild steels. [ABSTRACT FROM AUTHOR]

The macroscopic and microscopic surface morphology, products, kinetics, and reaction mechanism of one typical aero-engine material 0Cr18Ni9 in the cases of high-temperature oxidation and hot corrosion by a novel superhydrophobic and oleophobic ultrafine dry powder extinguishing agent (SHOU DPEA) are studied in a simulated aircraft engine compartment working environment. The results demonstrate that the oxidation and corrosion products both contain FeCr2O4, Fe2O3, and Fe3O4. However, the presence of SHOU DPEA accelerates the corrosion within the alloy. The 0Cr18Ni9 substrate shows a L-shaped segregation phenomenon and a chromium-poor layer. Furthermore, the oxidation and corrosion kinetic curves of 0Cr18Ni9 are both parabolic. In particular, the high-temperature oxidation behavior of 0Cr18Ni9 can be divided into two stages: a rapid oxidation stage (0-96 hours) and an oxidation equilibrium stage (96-192 hours), and the hot corrosion process can be divided into two stages: an initial slow incubation stage from 0 to 48 hours, and an accelerated corrosion stage from 48 to 192 hours. Additionally, the chemical reaction mechanisms for oxidation/corrosion are illustrated. [ABSTRACT FROM AUTHOR]

The oxidation behavior and oxidation mechanism of Ti 3 SiC 2 /Cu composites were investigated using constant temperature oxidation method. The Ti 3 SiC 2 /Cu composites were prepared at different sintering temperatures. Results showed that the relationship between the oxidation reaction rate of Ti 3 SiC 2 /Cu composites in air at 700 °C–900 °C and the oxidation temperature was in accordance with the parabolic law of oxidation kinetics. The oxidation weight gain and oxide layer thickness of Ti 3 SiC 2 /Cu composites at 700 °C and 800 °C were insignificant, with oxidation reaction rates of 3.0692 × 10−9 kg2m−4h−1 and 6.9856 × 10−9 kg2m−4h−1, respectively, and the oxidation rate of Ti 3 SiC 2 /Cu composites at 900 °C was enhanced to 1.00907 × 10−8 kg2m−4h−1. Ti 3 SiC 2 /Cu composites oxidized at 900 °C formed a protective oxide layer, which was mainly a multilayer structure composed of different kinds of oxides: the outer layer was mainly composed of TiO 2 ; the intermediate layer mainly consisted of CuO; the inner layer mainly made up of TiO 2 and SiO 2. [ABSTRACT FROM AUTHOR]

The thermal washing of oily sludge using sodium persulfate (SD) assisted by sodium lignosulfonate surfactant has been demonstrated to be an effective method for oily sludge remediation. To further explore the underlying mechanisms of this process, a systematic study was conducted by simulating oily sludge systems consisting of saturated hydrocarbons (SaH), aromatics hydrocarbons (ArH), resins (Res), and asphaltenes (Asp). The effects of reaction conditions, such as pH, sodium lignosulfonate alkyl (LSA) concentration, SD concentration, and washing temperature, were analyzed. Furthermore, the oxidative kinetic mechanism during the reaction process was investigated. The results demonstrated that neither petroleum hydrocarbons nor SD underwent significant chemical transformations when exposed to LSA, while SD exhibited a marked oxidative degradation effect on all four types of hydrocarbons. Oxidation kinetics indicated that sodium hydroxide played a catalytic role, with SD being the main oxidant and particularly efficient in degrading Asp and Res. Meanwhile, LSA contributed to the removal of hydrocarbons by reducing the surface tension of the solution, enhancing solubilization. This study not only elucidates the central role of SD in the thermal washing process but also provides a solid theoretical foundation for the practical application of this technology in oily sludge treatment. [ABSTRACT FROM AUTHOR]

Thermo-mechanically stabilized nanocrystalline (NC) alloys are increasingly valued for their enhanced mechanical strength and high-temperature stability, achieved through thermodynamic and kinetic stabilization methods. However, their fine-grained structure also increases susceptibility to internal oxidation due to higher atomic diffusivity associated with a greater volume fraction of grain boundaries (GBs). By incorporating solutes that form protective oxides, or the so-called thermally growing oxides (TGO), this vulnerability can be mitigated. The TGO scale acts as a diffusion barrier for oxygen that slows down the oxidation kinetics and prevents internal oxidation that impairs the structural integrity of the metal. This review examines advancements in oxidation-resistant NC alloys, focusing on the interplay between grain size and alloy chemistry. We explore how grain refinement influences diffusion coefficients, particularly the enhanced GB diffusion of Ni and Cr in Ni-Cr-based alloys, which improves oxidation resistance in NC variants like Ni-Cr and Cu-Cr compared to coarse-grained counterparts. We also analyze the role of third elements as oxygen scavengers and the impact of reactive elements such as Hf, Zr, and Y in NiAl alloys, which can slow down diffusion through early establishment of protective TGO layers and enhance oxidation resistance. The concomitant effect of grain size refinement, modifications in alloy stoichiometry, and enhanced atomic diffusion is shown to manifest via drastic reductions in oxidative mass gain, and visualization of the stable, protective oxide scales is delivered through characterization techniques such as TEM, SEM, and EDS. A brief overview is provided regarding stress effects and the role of induced stress in driving oxide scale spallation, which can negatively impact oxidation kinetics. Lastly, we propose future research directions aimed at developing micro-structurally stable NC alloys through multi-solute strategies and surface modification techniques, targeting robust materials for high-stress applications with improved oxidation resistance. [ABSTRACT FROM AUTHOR]

Conveyance tube manufacturing via a hot-finished, welded route is an energy-intensive process which promotes rapid surface oxidation. During normalisation at approximately 950 °C to homogenise the post-weld microstructure, an oxide mill scale layer grows on tube outer surfaces. Following further thermomechanical processing, there is significant yield loss of up to 3% of total feedstock due to scale products, and surface degradation due to inconsistent scale delamination. Delaminated scale is also liable to contaminate and damage plant tooling. The computational thermochemistry software, Thermo-Calc 2023b, with its diffusion module, DICTRA, was explored for its potential to investigate oxidation kinetics on curved geometries representative of those in conveyance tube applications. A suitable model was developed using the Stefan problem, bespoke thermochemical databases, and a numerical solution to the diffusion equation. Oxide thickness predictions for representative curved surfaces revealed the significance of the radial term in the diffusion equation for tubes of less than a 200 mm inner radius. This critical value places the conveyance tubes' dimensions well within the range where the effects of a cylindrical coordinate system on oxidation, owing to continuous surface area changes and superimposed diffusion pathways, cannot be neglected if oxidation on curved surfaces is to be fully understood. [ABSTRACT FROM AUTHOR]

This study addresses the global issue of recycling used vehicle tires, typically burned out or trimmed to be reused in playground floors or road banks. In this study, we explore a novel environmentally responsive approach to decomposing and recovering the carbon black particles contained in tires (25–30 wt.%) by vacuum pyrolysis. Given that carbon black is well known for its UV protection in plastics, the objective of this research is to provide an ecological alternative to commercial carbon black of fossil origin by recycling the carbon black (rCB) from used tires. In our research, we create a composite material using rCB and high-density polyethylene (HDPE). In this article, we present the environmental aging studies carried out on this composite material. The topographic evolution of the samples with aging and the oxidation kinetics of the surface and through the thickness were studied. The Beer–Lambert law is used to relate the oxidative index to the characteristic depth of the samples. The UV photons are observed to penetrate up to 54% less with the addition of 6 wt.% of rCB compared to virgin HDPE. In this work, the addition of rCB as filler for HDPE used for outdoor applications has demonstrated to be an antioxidant for UV protection and a good substitute for commercial carbon black for industrial goods. [ABSTRACT FROM AUTHOR]

Tristructural isotropic (TRISO) fuel particles, developed for use in high‐temperature gas‐cooled nuclear reactors, can be subjected to oxidizing environments in off‐normal accident scenarios. In this study, surrogate TRISO fuel particles were oxidized at 1000–1350°C for 4 h in 20 kPa water vapor atmosphere balanced with ultrahigh‐purity helium gas. The oxide scale morphology and thickness were studied via scanning electron microscopy, focused ion beam, and transmission electron microscopy. The oxide thickness increased as the oxidation temperature was increased. Although the oxide scale at 1000°C was completely amorphous, pockets of crystalline oxide were observed on particles oxidized at 1200 and 1300°C. Kinetic analysis was performed to deduce the oxidation mechanism by determining the apparent activation energy using linear regression analysis. The oxidation mechanism was consistent for temperatures from 1000 to 1200°C with an activation energy of 412.4 ± 8.8 kJ/mol. The activation energy then dropped to approximately 201 ± 7.1 kJ/mol for temperatures 1200–1350°C. Therefore, there is a change in oxidation mechanism at ∼1200°C. This change is attributed to the existence of a network of significant bubbles in the oxide layer at higher temperatures, which serve as rapid diffusion pathways for the transport of oxidants from the surface to the SiC/SiO2 interface, instead of relying on the bulk diffusion through the SiO2 layer at lower temperatures where only small bubbles are present along the SiC/SiO2 interface. [ABSTRACT FROM AUTHOR]

The study investigates ignition and oxidation behavior of Mg-3Nd-3Gd-0.2Zr-0.2Zn (wt.%) (EV33 alloy) in air and varying pressure. EV33 exhibits easy ignition in air but not under specific pressure conditions. Surface microstructure evolution and detailed discussion of ignition mechanisms using oxidation mechanism and residual stress of oxide film are presented. Findings suggest a correlation between alloy ignition and oxide film rupture. Surface oxidation film rupture is the direct cause of ignition in magnesium alloys, and this phenomenon has been observed and documented for the first time. The residual stresses calculated under atmospheric conditions and at pressures of 0.05 MPa, 0.1 MPa, and 0.15 MPa (with air as the pressure medium) are as follows: 0.282 GPa, 0.561 GPa, 2.271 GPa, and 5.242 GPa.

The effect of different heat treatment temperatures on the isothermal oxidation of Ni-based Fe-40Ni-24Cr alloy was studied. The alloy underwent a heat treatment process at 1000°C and 1200°C for 3 hours of soaking time, followed by water quenching. These samples are labeled as N10 and N12. The heat-treated samples were characterized in terms of grain size using an optical microscope and hardness testing using a Rockwell hardness. As a result, increasing the heat treatment temperature increases the average grain size of the alloy and lowers the hardness value. Heat-treated N10 and N12 samples were subjected to an isothermal oxidation test at 950°C for an exposure time of 150 h. Oxidized heat-treated samples were characterized in terms of oxidation kinetics calculated based on weight change per surface area as a function of time. In addition, phase analysis and oxide surface morphology were measured using x-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. As a result, the oxidation kinetics of both samples showed a pattern of weight gain with N10 recording the lowest weight gain. Both samples obey a parabolic rate law, indicating a controlled oxide growth rate. N10 recorded the lowest parabolic rate constant of 2.5×10–8 mg2cm–4s–1, indicating a low oxidation rate, thus having good oxidation resistance. Phase analysis using XRD shows that several oxide phases have been formed consisting of Cr-containing oxides Cr2O3 and MnCr2O4. In addition, SEM analysis displayed a uniform oxide layer formed on the N10 sample, indicating good oxide adhesion. This finding shows an important contribution to the oxidation protection mechanism that records the fine grain obtained from the heat treatment process can increase good oxidation resistance.

Boron nitride nanotubes (BNNTs) are gaining interest for high temperature applications due to their thermal stability at elevated temperatures. Although BNNT temperature limits are well studied, there remains a gap in quantifying the high temperature failure mechanisms and oxidation kinetics. This study characterizes the oxidation mechanisms and kinetics of BNNTs and Al 2 O 3 -coated BNNTs, via atomic layer deposition (ALD), at temperatures between 850 and 1000 °C. ALD Al 2 O 3 surface coatings improved BNNT oxidation resistance by over an order of magnitude for coating thicknesses between 7 and 56 nm. However, the improved oxidation resistance of Al 2 O 3 -coated BNNTs decayed after prolonged exposure to oxygen at elevated temperatures, gradually reaching the same extent of oxidation as uncoated BNNTs after approximately 200 min at 900 °C. This behavior is attributed to the crystallization of as-deposited amorphous Al 2 O 3 coatings at elevated temperatures leading to densification, cracking, and exposure of BNNTs to the oxidizing environment. While Al 2 O 3 coatings did not completely prevent oxidation, a significant improvement in oxidation resistance was observed, extending the thermal stability of BNNTs. [ABSTRACT FROM AUTHOR]

Persistent phosphors possess unique afterglow optical properties. In this paper, a class of ultra-violet (UV) persistent luminescence nanoparticles were developed for catalytic photodegradation applications. UV persistent luminescence nanoparticles of SiO 2 -Zn 2 SiO 4 :Ga and SiO 2 -Zn 2 SiO 4 :Ga,Pb were successfully synthesized by using a mesoporous template method. The UV persistent luminescence intensity of SiO 2 -Zn 2 SiO 4 :Ga at 405 nm was enhanced up to ca. 3.5 times by co-doping with Pb2+ (396 nm), along with longer persistent luminescence duration. The photodegradation results indicate that it is useful to introduce UV persistent luminescence property into SiO 2 -Zn 2 SiO 4 :Ga,Pb to obtain enhanced catalytic activity of SiO 2 -Zn 2 SiO 4 with a bigger catalytic oxidation reaction kinetic constant (up to ∼4 times). This kind of UV persistent catalysis strategy may become a potential feasible method for better catalytic photodegradation activity. The UV persistent photocatalyst has potential applications in the photooxidation of organic molecules in high chroma and/or turbidity aqueous systems. [ABSTRACT FROM AUTHOR]

Utilization of clean and low‐cost water as the reductant to enable hydrogenation of alkenes is highly attractive in green chemistry. However, this research subject is considerably challenging due to the sluggish kinetics of the water oxidation half‐reaction. It is also very difficult to avoid the undesired oxidation of alkenes because that this oxidation is far easier to occur than the desired oxidation of water from thermodynamic standpoint. Herein, this challenge is overcome by applying a cooperative catalysis where HCl is used as the cocatalyst to accelerate Pt/g‐C3N4‐catalyzed water oxidation and suppress the undesired oxidation of the alkene. This provides an example for using water as the reductant and the proton source to enable the photocatalytic hydrogenation of alkenes. The present method exhibits broad substrate applicability, and allows various arylethenes and aliphatic alkenes to undergo the hydrogenation smoothly. [ABSTRACT FROM AUTHOR]

The difference of work functions induces the build-in electric field in NiS/MoS 2 heterointerface, leading to electron density increase of interfacial Ni atoms, which enhances the adsorption of LiO 2 with one-electron oxygen reduction/oxidation processes. [Display omitted] Electrocatalysts with appropriate electron coupling toward LiO 2 intermediates can exhibit superior oxygen reduction/evolution reaction kinetics in Li-O 2 batteries (LOBs). In this work, a charge redistribution strategy has been developed by constructing NiS/MoS 2 heterostructure nanosheet self-assembled hollow microspheres with an internal electric field to regulate the interaction with LiO 2 and then improve the electrochemical performance of LOBs. Density functional theory calculations and physicochemical characterizations reveal that the difference of work functions between NiS and MoS 2 promotes the electron redistribution in heterointerface via built-in electrical field, leading to increased electron density of interfacial Ni atom, thereby enhancing its electron coupling toward LiO 2 intermediates and promoting one-electron oxygen reduction/oxidation reaction kinetics. As a result, the NiS/MoS 2 -based LOBs exhibit evidently higher discharge capacity and much better cycling performance than the batteries using NiS and MoS 2. This work provides a reliable charge redistribution strategy induced by build-in electric field to design efficient catalysts for LOBs. [ABSTRACT FROM AUTHOR]

The pairs of Cu2O/CuO and CoO/Co3O4 as the carriers of transferring oxygen and storing heat are essential for the recently emerged high-temperature thermochemical energy storage (TCES) system. Reported research results of Cu2O and CoO oxidation kinetics show that the reaction rate near equilibrium decreases with the temperature, which leads to the negative activation energy obtained using the Arrhenius equation and apparent kinetics models. This study develops a first-principle-based theoretical model to analyze the Cu2O and CoO oxidation kinetics. In this model, the density functional theory (DFT) is adopted to determine the reaction pathways and to obtain the energy barriers of elementary reactions; then, the DFT results are introduced into the transition state theory (TST) to calculate the reaction rate constants; finally, a rate equation is developed to describe both the surface elemental reactions and the lattice oxygen concentration in a grain. The reaction mechanism obtained from DFT and kinetic rate constants obtained from TST are directly implemented into the rate equation to predict the oxidation kinetics of Cu2O without fitting experimental data. The accuracy of the developed theory is validated by experimental data obtained from the thermogravimetric analyzer (TGA). Comparing the developed theory with the traditional apparent models, the reasons why the latter cannot appropriately predict the true oxidation characteristics are explained. The reaction rate is jointly controlled by thermodynamics (reaction driving force) and kinetics (reaction rate constant). Without considering the effect of the reaction driving force, the negative apparent activation energy of Cu2O oxidation is obtained. However, for CoO oxidation, the negative apparent activation energy is still obtained although the effect of the reaction driving force is considered. According to the DFT results, the activation energy of the overall CoO oxidation reaction is negative, but the energy barriers of the elementary reactions are positive. Moreover, according to the first-principle-based rate equation theory, the pre-exponential factor in the kinetic model is dependent on the partition function ratio and decreases with the temperature for the Cu2O and CoO oxidation near equilibrium, which results in the apparent activation energy being slightly lower than the actual value. [ABSTRACT FROM AUTHOR]

Pyrite is one of the most abundant metal sulfide tailings and is susceptible to oxidation, yielding acidic mine drainage (AMD) that poses significant environmental risks. Consequently, the exploration of pyrite surface oxidation and the kinetic influencing factors remains a pivotal research area. Despite the oxidation of pyrite producing a significant amount of sulfate (SO42−), a comprehensive investigation into its influence on the oxidation process is lacking. Leveraging pyrite's semiconducting nature and the electrochemical intricacies of its surface oxidation, this study employs electrochemical techniques—cyclic voltammetry (CV), Tafel polarization, and electrochemical impedance spectroscopy (EIS)—to assess the effect of SO42⁻ on pyrite surface oxidation. The CV curve shows that SO42− does not change the fundamental surface oxidation mechanism of pyrite, but its redox peak current density decreases with the increase in SO42−, and the surface oxidation rate of pyrite decreases. The possible reason is attributed to SO42− adsorption onto pyrite surfaces, blocking active sites and impeding the oxidation process. Furthermore, Tafel polarization curves indicate an augmentation in polarization resistance with elevated SO42− concentrations, signifying heightened difficulty in pyrite surface reactions. EIS analysis underscores an increase in Weber diffusion resistance with increasing SO42⁻, indicating that the diffusion of Fe3+ to the pyrite surface and the diffusion of oxidized products to the solution becomes more difficult. These findings will improve our understanding of the influence of SO42− on pyrite oxidation and have important implications for deepening the understanding of surface oxidation of pyrite in the natural environment. [ABSTRACT FROM AUTHOR]

In this research work, the catalytic performances of two manganese-based catalysts, manganese (III) acetylacetonate (Mn(acac)3) and manganese tallate (Mn-TO), were studied during the process of Ashalcha heavy oil oxidation under in situ combustion conditions. DSC analysis shows distinct thermal behavior of both ligated catalysts during low- and high-temperature oxidation phases (LTO and HTO); for example, the shifting in peak temperature (Tp) in the HTO at a heating rate of 10 °C/min was reduced by approximately 5.3% for Mn-TO and 2.24% for Mn(acac)3 when compared with uncatalyzed heavy oil. Combined isothermal kinetic analyses using the Friedman and Kissinger–Akahira–Sunose analytic methods have provided insights about activation energies and frequency factors over the whole conversion range, where the catalytic performance of Mn-TO showed low activation energies in both LTO and HTO (Eα of Mn-TO was approximately 13.33% (LTO) and 7.68% (HTO) less than with the heavy oil alone). In addition, calculations of the effective rate constant confirmed the increased oxidation rate trend of both catalysts, with Mn-TO exhibiting the highest values. The findings highlight the potential of these manganese-based catalysts, the Mn-TO catalyst in particular, in optimizing heavy oil oxidation processes. The overall results further contribute to developing more efficient ligand catalyst complexes for sustainable heavy oil recovery while continuously improving their efficient application during in situ combustion in the petroleum industry. [ABSTRACT FROM AUTHOR]

Understanding the oxidation behavior of hafnium carbide is crucial to its application in extreme environments. In this work, the transition in high‐temperature oxidation kinetics regimes in hafnium carbide is explained based on phase equilibria considerations supported by observed changes in oxide scale microstructure evolution associated with different transformation pathways. Below, a composition‐dependent critical temperature and oxygen pressure, hafnium carbide first transforms to an amorphous material with nominal composition HfO2C followed by phase separation into carbon and hafnia domains. Subsequently, gaseous transport through a nanometric pore network formed by oxidative removal of phase‐separated carbon becomes rate‐limiting. Above this critical point, the oxidation sequence involves a direct transformation from hafnium carbide to hafnia and gaseous products, leading to dissimilar scale morphologies responsible for the reported transition from gaseous to solid‐state diffusion‐limited oxidation regimes at ultra‐high temperatures. [ABSTRACT FROM AUTHOR]

The current study focuses on the role of composition in the oxidation behavior of three commercial SiC fibers (Hi‐Nicalon Type S (HNS), Tyranno ZMI, and Tyranno SA) in a steam‐containing environment at 1000°C. Oxide scales that form on each of the three fiber types differ in morphology, microstructure, and composition. Differences are attributed to O and C contents, crystallinity, and minor alloying elements. Oxidation kinetics of the HNS fibers follow linear/parabolic (Deal–Grove) predictions over the entire range of exposure times (to 96 h). In the other fibers, deviations from the initial linear/parabolic trend occur when either the scale crystallizes in situ during oxidation (as on the ZMI fibers) or when structural changes internal to the fiber alter the chemical environment at the scale/fiber interface (on the SA fibers). Adaptations of the linear/parabolic oxidation model are used to rationalize the growth kinetics in the latter two cases. Collectively, the data and analyses indicate a two‐fold difference in permeabilities of crystalline and amorphous silica scales. Inferred interface reaction rates further suggest faster oxidation for fibers with greater amounts of amorphous Si–O–C. Moreover, crystalline scales are more prone to cracking, because of their higher viscosity at elevated temperatures and a deleterious phase transformation upon cooling. [ABSTRACT FROM AUTHOR]

This paper examines the effect of oxygen concentration on the oxidation process and properties of aluminum particles, providing valuable insights for production and storage. Micron-grade aluminum powders were tested at heating rates of 5, 7.5, 10, and 15 K/min under oxygen concentrations of 7, 11, 15, 21, and 30 vol%. Results indicate a two-step mass gain oxidation process, with less pronounced mass gain at lower oxygen concentrations. SEM and XRD characterized the morphological and crystalline changes during oxidation. Lowering oxygen concentration from 30 vol% to 7 vol% increased the onset oxidation temperature by 17.1 °C. Increasing the proportion of inert gas in the atmosphere increases the ignition temperature of aluminum powder. The mathematical modeling approach of AKTS was used to decouple and analyze the thermal effects of simultaneous melting and oxidation, using the Friedman method to show that the apparent activation energy is about 350 kJ/mol in low-oxygen atmospheres (7 vol% and 11 vol%). The kinetics of aluminum oxidation were found to be closely related to the oxygen concentration, and based on the kinetics parameter, it is possible to predict a minimum limiting oxygen concentration. [ABSTRACT FROM AUTHOR]

The high-temperature shaping of steels is accompanied by the formation of surface scales composed of oxide layers. However, the oxidation kinetics and morphology of these scales remain poorly understood. This study analyses the formation of oxide layers on AISI 4140 steel at varying oxidation times (20, 40 and 60 min) at 1000 °C. The analysis revealed the presence of hematite, magnetite, and transformed wustite in the oxide layers, along with clusters of alloying element oxides, predominantly chromium and iron oxide (FeCr2O4). There was a direct correlation between the duration of the oxidation process and the thickness of the scale and the number of defects observed in the material. The coating layer of alloying element oxides demonstrated insufficient adhesion to the steel substrate. Similarly, the oxides of alloying elements within this layer exhibited low cohesion among themselves. The alloying elements are present in all oxide layers, but in greater quantity in the layer in contact with the steel substrate, where a reduction in their concentrations was observed over time. This indicates that the alloying elements tend to disperse as the thickness of the alloying element oxide layer increases over time. [ABSTRACT FROM AUTHOR]

The delayed failure of SiC fibers is commonly described by a power law relating the growth rate to the stress intensity factor KI, itself following the classical fracture mechanics law with a constant geometrical factor. For low stress levels, relevant for ceramic matrix composite (CMC) applications, this model predicts crack lengths exceeding the specimen size and unrealistic times to failure. Indeed, discrepancies between this model prediction and experiments have been reported. This paper proposes a model improvement with a simple and accessible analytical solution to work around this shortcoming. First, a more accurate description of fracture mechanics is introduced which yields physically reasonable estimates of the crack size at failure. Then, the contribution of silica scale formation to oxidation embrittlement (OE) is evaluated. If the corrected slow crack growth (SCG) model and the OE model are irrelevant when taken separately, their simultaneous presence accurately depicts the observations: OE prevails under low stresses, resulting in a finite lifetime below 150 MPa, whereas SCG takes over above 800 MPa. This result brings new insight for the design of CMC and may as well apply to other types of materials, prone to environment-assisted and stress-accelerated degradation. [ABSTRACT FROM AUTHOR]

Photoelectrochemical (PEC) water splitting is regarded as a potential technique for converting solar energy. However, the fast charge recombination and slow water oxidation kinetics significantly have hindered its practical application. It is found that an elevation in operation temperature can activate the charge transport in the photoanodes. Here, a strategy was performed that carbon nanoparticles were employed to TiO2 nanorods, acting as electron reservoirs as well as photothermal materials. More specifically, a record photocurrent density of 1.62 mA cm−2 at 1.23 V vs. RHE has been achieved, accompanied by a high charge separation efficiency of 96% and a long-term durability for 8 h. The detailed experimental results reveal that under NIR light irradiation, the synergistic effect between electron storage and temperature rise leads to accelerated charge transport in the bulk and water oxidation kinetics on the surface. This research offers a new perspective on how to boost the PEC performance of photoelectrodes. [ABSTRACT FROM AUTHOR]

The controlled synthesis of recyclable hematite in the leaching solution of secondary zinc oxide powder is an urgent problem in the chemical industry and metallurgy fields. In this paper, the effects of the temperature, agitation speed, and seed addition on the contents of iron, sulfur, potassium, sodium, and zinc in the iron removal residues, as well as the iron concentration in the supernatant after iron removal were systematically studied. In addition to the temperature control already reported, we found that the agitation speed can also control the transformation between jarosite and hematite phases. The content of jarosite in the residues can be effectively controlled by adjusting the agitation speed, thereby significantly improving the quality of hematite product, as indicated by SEM-EDS and XRD results. Under temperature of 185 °C, an agitation speed of 500 rpm, and a seed addition of 15 g/L, the iron, sulfur and zinc contents in the filter residues and the iron concentration in the supernatant were 59%, 3.22%, 0.92%, and 4.182 g/L, respectively. Kinetic studies show that the rapid oxidation kinetics is not conducive to the formation of high-quality hematite products. These results can directly guide the process of transformation of harmful jarosite into recyclable hematite from the leaching solution of secondary zinc oxide powder, which is of great practical significance for the controlled and waste-free removal of iron from aqueous solutions in the chemical industry and metallurgy fields. [ABSTRACT FROM AUTHOR]

In the study, a BN f /SiBN composite was fabricated through precursor infiltration and pyrolysis (PIP) method. The oxidation resistance of the composite was investigated at different oxidation temperatures, focusing on the micro-structure evolution, the phase composition and oxidation kinetics of bare fibers versus fibers protected by the matrix under various oxidation states. The result indicates that the BN f /SiBN composite remains stable at 1100 °C in air atmosphere, while the fibers protected by matrix maintain their complete structure even at 1500 °C. Furthermore, we elucidated the oxidation mechanism of SiBN matrix: SiBN matrix undergoes a prior oxidation stage and transforms into amorphous SiO 2 and B 2 O 3 at high temperatures to impede the oxygen attachment to fibers while preserving the integrity of internal structure. The emergence of ultra-high temperature resistant BN f /SiBN composite and along with the exploration of oxidation behavior has opened up new approach for advancing radome material development. [ABSTRACT FROM AUTHOR]

Exposure of cell membranes to reactive oxygen species can cause oxidation of membrane lipids. Oxidized lipids undergo drastic conformational changes, compromising the mechanical integrity of the membrane and causing cell death. For giant unilamellar vesicles, a classic cell mimetic system, a range of mechanical responses under oxidative assault has been observed including formation of nanopores, transient micron‐sized pores, and total sudden catastrophic collapse (i.e., explosion). However, the physical mechanism regarding how lipid oxidation causes vesicles to explode remains elusive. Here, with light‐induced asymmetric oxidation experiments, the role of spontaneous curvature on vesicle instability and its link to the conformational changes of oxidized lipid products is systematically investigated. A comprehensive membrane model is proposed for pore‐opening dynamics incorporating spontaneous curvature and membrane curling, which captures the experimental observations well. The kinetics of lipid oxidation are further characterized and how light‐induced asymmetric oxidation generates spontaneous curvature in a non‐monotonic temporal manner is rationalized. Using the framework, a phase diagram with an analytical criterion to predict transient pore formation or catastrophic vesicle collapse is provided. The work can shed light on understanding biomembrane stability under oxidative assault and strategizing release dynamics of vesicle‐based drug delivery systems. [ABSTRACT FROM AUTHOR]

Ag-based electrical contact materials are essential in low-voltage devices such as relays, switches, circuit breakers, and contactors. Historically, Ag-CdO composites have been preferred due to their superior electrical and thermal conductivities, resistance to arcing, and mechanical strength. However, the toxicity of Cd has led to increased restrictions on its use. With the aim of contributing to the development of a new environment-friendly, Ag-Zn2SnO4-based electrical contact material, the kinetics of the hot mechanochemical oxidation of a Ag-Sn-Zn solid solution obtained by mechanical alloying were investigated. The results indicated that the proposed synthesis route produces Ag-based composites with a homogeneous distribution of nanoscale Zn2SnO4 precipitates, which is unattainable through conventional material processing methods. This kinetic study established that the mechanochemical oxidation of the Ag-Sn-Zn solid solution follows the Johnson–Mehl–Avrami–Kolmogorov model. An analysis of the microstructure and the relationship between the activation energy "Ea" and the Avrami exponent "n" from experimental data fitting suggests that the primary mechanism for the oxidation of the Ag-Sn-Zn solid solution during the hot mechanochemical process is related to the three-dimensional oxide growth being limited by oxygen diffusion after its immediate initial nucleation. [ABSTRACT FROM AUTHOR]

Lakes are important sentinels of climate change and may contribute over 30% of natural methane (CH4) emissions; however, no earth system model (ESM) has represented lake CH4 dynamics. To fill this gap, we refined a process‐based lake biogeochemical model to simulate global lake CH4 emissions, including representation of lake bathymetry, oxic methane production (OMP), the effect of water level on ebullition, new non‐linear CH4 oxidation kinetics, and the coupling of sediment carbon pools with in‐lake primary production and terrigenous carbon loadings. We compiled a lake CH4 data set for model validation. The model shows promising performance in capturing the seasonal and inter‐annual variabilities of CH4 emissions at 10 representative lakes for different lake types and the variations in mean annual CH4 emissions among 106 lakes across the globe. The model reproduces the variations of the observed surface CH4 diffusion and ebullition along the gradients of lake latitude, depth, and surface area. The results suggest that OMP could play an important role in surface CH4 diffusion, and its relative importance is higher in less productive and/or deeper lakes. The model performance is improved for capturing CH4 outgassing events in non‐floodplain lakes and the seasonal variability of CH4 ebullition in floodplain lakes by representing the effect of water level on ebullition. The model can be integrated into ESMs to constrain global lake CH4 emissions and climate‐CH4 feedback. Plain Language Summary: Lakes are highly sensitive to climate change and can produce over 30% of natural methane (CH4) emissions. However, these emissions are not well understood or included in global CH4 assessments. Current lake CH4 models either miss key processes or haven't been tested with observations from different environments. To address this, we improved the Advanced Lake Biogeochemistry Model (ALBM) to better simulate CH4 production, oxidation, and transport. We also created a new data set of CH4 emissions from 106 lakes worldwide to validate the model. Our improved model shows promising performance in simulating observed emissions. Our findings highlight the importance of including CH4 production in oxygen‐rich water, the impact of water level change on CH4 bubble release, and a new method for CH4 oxidation in lake CH4 models. The improved ALBM can now be used in Earth system models to better predict global lake CH4 emissions and their impact on climate change. Key Points: We enhanced and validated the Advanced Lake Biogeochemistry Model for lake CH4 emissions using a new global data setThe model captures lake CH4 emissions across diverse environments and accounts for seasonal and inter‐annual variationsLake CH4 models should include oxic CH4 production, water level impact on ebullition, and a new method for CH4 oxidation [ABSTRACT FROM AUTHOR]

The oxidation of phenoxyacetic acid, along with certain para- and meta-substituted phenoxyacetic acid derivatives, which reacts with 3,5-dimethyl pyrazolium chlorochromate within a 50% (v/v) aqueous acetic acid solution at 308 K. The observed reaction exhibits a unit order with respect to both the 3,5-dimethyl pyrazolium chlorochromate and the substrates involved. This phenomenon demonstrates fractional-order kinetics in the case of perchloric acid and oxalic acid. The computation of ∆H#, ∆S#, ∆G#, and Ea values from Eying’s equation, according to the results of the experiment. In all the cases of substituents, the product identified is consistently the corresponding p-benzoquinone. The rate is hastened by electron-releasing substituents, whereas electron-withdrawing substituents slow down the rate. The formulation of a plausible mechanism and rate law has been derived. [ABSTRACT FROM AUTHOR]

Direct Metal Laser Sintered Haynes 282 specimens as well as wrought ones were subjected to high-temperature exposure at 1000 °C for 100h in air to compare their oxidation behaviour. The specimens were removed from the furnace after 1h, 5h, 25h, 50h and 100h to reveal and study oxidation mechanisms through morphological and cross-sectional examination by using scanning electron microscopy with energy dispersive spectroscopy attachment and X-ray diffraction. Microstructural studies revealed that the oxidation kinetics, determined by changes in thickness scale and depth of aluminium diffusion zone, were mainly driven by the formation of Cr2O3 for the wrought material, and TiO2 for DMLS one. The wrought material was characterized by the oxidation rate equal to 0.96 and followed the logarithmic law. On the other hand, DMLS-manufactured Haynes 282 exhibited oxidation rate of 0.90 and follows the linear law for the thickness scale considerations. However, when the depth of aluminium diffusion was investigated, it had an oxidation rate of 0.87 and followed cubic law. [ABSTRACT FROM AUTHOR]

Controllable hydrocarbon fuel combustion and combustion path adjustment are effective but difficult approaches to achieve reliable ignition under extreme conditions. However, the effective mechanism to control the combustion characteristics of hydrocarbon fuels is still unclear. In this study, the fuel (Fuel 6) based on free radical relay combustion (FRRC) significantly expands the ambient temperature-based ignition limits of pure fuel and shows a weak temperature correlation with ignition delay time. In addition, Fuel 6 still has a 100 % ignition probability at 50 kPa (the corresponding ignition limit flight altitude increased from 0.9 km above sea level to 5.4 km). Gaussian simulations show the thermodynamic feasibility of FRRC and prove the relay effect. According to kinetic analysis, the combustion reactions can be adjusted based on FRRC and exhibit three types of oxidation reactions, of which the reaction activation energies are all lower than those of the oxidation reactions of pure fuel. Furthermore, the results of in-situ Fourier transform infrared spectroscopy are consistent with the kinetic analysis based on thermogravimetric and differential thermogravimetric studies. The investigation of the combustion control mechanism under extreme conditions helps to broaden the ignition limit of the aviation engine combustor and to significantly improve the accurate control level of ignition under extreme conditions, providing theoretical support for solving the ignition problems of advanced aviation engines under extreme conditions. [Display omitted] • Modified fuel based on free radical relay combustion (FRRC) strategy significantly expands its ignition limits. • Gaussian simulation shows the thermodynamic feasibility of free radical relay combustion. • The combustion reactions based on FRRC exhibit three types of oxidation reactions by kinetic analysis. • Reaction path can be adjusted by adding additives to control the FRRC. [ABSTRACT FROM AUTHOR]

• The network-like LPSO phase in a Mg-11Y-1Al alloy decomposed into needle-like LPSO phase and polygonal Mg 24 Y 5 phase. • The in-situ oxidation of the needle-like LPSO phase facilitated the formation of a thicker and continuous Y 2 O 3 oxide scale. • The accelerated oxidation along the needle-like LPSO phase is attributed to divert the parabolic growth kinetics to a slower oxidation rate. In this study, we investigated the oxidation of the Mg-11Y-1Al alloy at 500 °C in an Ar-20%O 2 environment. Multiscale analysis showed the network-like long-period stacking ordered (LPSO) phase transformed into needle-like LPSO and polygonal Mg 24 Y 5 phases, leading to the formation of a high-dense network of needle-like oxides at the oxidation front. These oxides grew laterally along the oxide/matrix interfaces, forming a thicker, continuous scale that effectively blocked elemental diffusion. Hence, the preferential oxidation along the needle-like LPSO is believed to accelerate the formation of a thicker and continuous oxide scale, further improving the oxidation resistance of the Mg-11Y-1Al alloy. [Display omitted] [ABSTRACT FROM AUTHOR]