Variation Of Oxygen Content Research Articles

Experimental and molecular dynamics study on combustion characteristics of non-stick coal

To investigate the combustion characteristics of non-stick coal and the formation patterns of main combustion products and radicals, this study initially conducted a TG-DSC experiment of non-stick coal. Subsequently, non-stick coal was characterized and analyzed using XPS and 13C NMR experiments, and a molecular model with the formula C208H199O23N3S was constructed. Subsequently, the ReaxFF MD method was employed to simulate the combustion molecular dynamics of the non-stick coal periodic mixing model under varying oxygen content and temperature conditions. The analysis focused on elucidating the formation patterns of free and primary products during combustion. Experimental findings indicate that the combustion of non-stick coal progresses through stages, including water evaporation and desorption (30–145.65 °C), dynamic equilibrium (145.65–181.76 °C), oxygen weight gain (181.76–263.56 °C), thermal decomposition (263.56–379.14 °C), combustion (379.14–562.04 °C) and burnout (562.04–800 °C). The ignition temperature of non-stick coal was determined to be 379.14 °C. The simulation results indicate that an increase in temperature and oxygen content further enhances the relatively stable peak production of CO2. The peak increase of CO production is weaker than that of CO2. The rise in temperature also promotes the formation of H2O, while the increase in oxygen content initially enhances and subsequently inhibits the peak production of H2O. H radicals, O radicals, and OH radicals are primarily generated through the decomposition reactions of small molecular compounds or other free radicals. Free radical polymerization and the decomposition of small molecular compounds represent the primary pathways for the formation of CO, CO2, and H2O.

Design and Preparation of Lifetime-Based Dual Fluorescent/Phosphorescent Sensor of pH and Oxygen and its Exploration in Model Physiological Solutions and Cells.

In the present report, a novel dual pH-O2 sensor based on covalent conjugate of rhodamine 6G and cyclometalated iridium complex with poly(vinylpyrrolidone-block-vinyltetrazole) copolymer is reported. In model physiological solutions the sensor chromophores display independent phosphorescent and fluorescent lifetime responses onto variations in oxygen concentration and pH, respectively. Colocalization studies on Chinese hamster ovary cells demonstrate the preferential localization in endosomes and lysosomes. The fluorescent lifetime imaging microscopy-phosphorescent lifetime imaging microscopy (FLIM-PLIM) experiments show that the phosphorescent O2 sensor provides unambiguous information onto hypoxia versus normoxia cell status as well as semi-quantitative data on the oxygen concentration in cells in between these two states. However, the results of FLIM measurements indicate that dynamic lifetime interval of the sensor (≈0.5ns between pH values 5.0 and 8.0) is insufficient even for qualitative estimation of pH in living cells because half-width of lifetime distribution in the studied samples is higher than the sensor dynamic interval. Nevertheless, the variations in rhodamine emission intensity are much higher and allow rough discrimination of acidic and neutral cell conditions. Thus, the results of this study indicate that the suggested approach to the design of dual pH-O2 sensors makes possible to prepare the biocompatible and water-soluble conjugate with fast cellular uptake.

Fermentation dynamics of bile salt hydrolase production in Heyndrickxia coagulans ATCC 7050 and Lactiplantibacillus plantarum ATCC 10012: Addressing ninhydrin assay limitations with a novel HPTLC–MS method

Bile salt hydrolase (BSH), a pivotal enzyme in cholesterol management, holds significant promise in both human and animal subjects. This study investigated the effect of fermentation dynamics in Heyndrickxia coagulans ATCC 7050 and Lactiplantibacillus plantarum ATCC 10012 to enhance BSH production. Cultivation of cultures in MRS and M17 media revealed that MRS medium enhanced BSH production by 235.98 % in H. coagulans ATCC 7050 and 147.37 % in L. plantarum ATCC 10012, compared to M 17 medium. Additionally, varying oxygen concentration levels indicated that H. coagulans ATCC 7050 exhibited its minimum doubling time of 79.8 ± 0.64 min in anaerobic conditions, whereas L.plantarum ATCC 10012 demonstrated its minimum doubling time of 85.5 ± 1.2 min under microaerophilic conditions. However, their highest BSH activity was observed during the stationary phase under anaerobic conditions, yielding 17.14 ± 0.78 U/mL by H. coagulans ATCC 7050 and 19.04 ± 0.81 U/mL by L.plantarum ATCC 10012. Furthermore, it was observed that both organisms did not retain BSH within their cells. BSH activity was assessed using ninhydrin assay that detected free taurine liberated from sodium taurocholate. However, ninhydrin can yield false–positive results owing to its interaction with other free amino acids. To subjugate this limitation, the study introduced a novel and sensitive HPTLC–MS method capable of accurately detecting taurine. By comprehending fermentation dynamics and selecting appropriate conditions, BSH production increased 2.1–fold in both organisms. These findings illuminate critical insights, offering a pathway for novel strategies to enhance the BSH–producing capabilities of these LAB strains.

Insight into the effect of oxygen content on the corrosion behavior of X70 pipeline steel in a typical simulated soil solution by dissolution-diffusion-deposition model

In this work, traditional experimental methods were employed to investigate the effect of dissolved oxygen (DO) on the corrosion behavior of X70 pipeline steel in a low-temperature acidic-bentonite simulation soil solution. A novel model was utilized to describe the complex dissolution-diffusion-deposition process at the metal/solution interface. This model aims to enhance comprehension of the dynamics of the corrosion product layer of X70 pipeline steel under varying oxygen concentrations, as well as the effects of alloying elements (Fe, Cr and Cu) on the corrosion resistance. By integrating traditional experimental methods with calculation models, the results reveal a positive correlation between DO levels and the corrosion rate X70 pipeline steel. This relationship is attributed to the distinct characteristics of the corrosion product layers formed under different DO conditions. At low DO levels, the nucleation and growth rates of oxide/hydroxide are slower, leading to the formation of a denser, more protective corrosion product layer. Conversely, at high DO levels, the accelerated nucleation and growth rates produce larger oxide/hydroxide particles, resulting in a porous and less protective corrosion product layer. Furthermore, the variation in the protective qualities of the corrosion product layers under different DO conditions causes differences in corrosion morphology: X70 pipeline steel exhibits localized corrosion in low DO environments and more uniform corrosion under high DO conditions.

Composition changes and micro explosion characteristics of burning droplets formed by combustion of micrometer iron wires

To analyze the composition changes during the combustion process of iron droplets using the energy balance equation, iron wires with diameters of tens of micrometers were burned to form temperature-stable iron droplets with diameters of hundreds of micrometers. High-speed two-color imaging pyrometry was employed to measure the spatially resolved surface temperature and volume changes of the droplets under varying oxygen concentrations. Experimental results showed that the droplet's temperature stabilized between the melting points of wüstite and iron. Quantitative analysis revealed the presence of bubbles within the droplets, primarily sourced from the oxidation of carbon in the iron to carbon dioxide. Simulation results of the droplet combustion process revealed that at the experimental combustion temperatures, the transport of oxygen in molten iron oxides was the rate-limiting step. The gas responsible for micro-explosions originates from the release of dissolved excess oxygen before the solidification of molten iron oxides, with rough estimates indicating that the mass of the released gas is only 0.02% to 0.03% of the droplet mass. The impact of reaction kinetics parameters on the simulation results, as well as the role of the micro-explosion mechanism in the self-sustained combustion of iron wires, were also discussed.

Effect of furnace temperature and oxygen concentration on combustion and CO/NO emission characteristics of sewage sludge

Addressing the growing energy crisis, the development and utilization of solid waste have become a critical research areas. Sewage sludge, rich in organic matter, can serve as an alternative fuel to coal. This study employs a thermogravimetric analyzer to investigate the combustion characteristics of sewage sludge at heating rates of 10, 20, and 40 °C/min. Additionally, a horizontal tube furnace is utilized to analyze the CO and NO emission characteristics during sewage sludge combustion at varying oxygen concentrations and temperatures. Results indicate that at a constant gas velocity, the primary factor influencing combustion characteristics and CO/NO emissions is the composition difference. Higher furnace temperatures lead to lower CO generation and increased combustion efficiency. The conversion of coke-N to NO rises with increasing temperature. Moreover, higher furnace temperatures decrease the conversion of fuel-N to NO. Increasing oxygen concentration reduces the ignition concentration limit of sewage sludge. The lowest NOx emissions were recorded at an oxygen concentration of 21 vol%. This study provides essential data for reducing coal consumption and enhancing the safe and efficient treatment of sewage sludge.

An Analytical Model for an Anode-Supported Solid Oxide Fuel Cell

This study presents a one-dimensional, non-isothermal, steady-state model to analyze performance of an anode-supported solid oxide fuel cell (SOFC). The modeling domain encompasses components including a NiO-YSZ support and functional layer forming the anode, a YSZ electrolyte, a GDC interlayer, as well as LSCF+GDC and LSCF constituting the cathode. The model distinguishes different types of electrode polarization resistances using experimental impedance data at various temperatures under open circuit voltage (OCV), employing a detailed equivalent circuit model to determine the temperature and partial pressure dependencies of electrode exchange current densities. Moreover, this approach serves as an efficient method for estimating the conductivity of both the anode and cathode. As a result, activation energies and ohmic overpotentials are derived, considering microstructural and geometrical aspects, which allows for accurate quantification of the ohmic resistance associated with ionic conduction.The model incorporates coupled multi-physics elements, such as mass and charge transport, electrochemical reactions, and heat transfer. A notable feature of the model is its consideration of reaction zone layers near the electrolyte, where electrochemical reactions generate electrons, oxide ions, and water vapor. Enhancing prediction accuracy, the model applies multilayer discretization within the electrode and electrolyte to reflect actual material properties and localized conditions more accurately. The model predicts the performance of a single-cell SOFC using pure hydrogen at the anode and varying oxygen concentrations (100%, 50%, 20%, and 10%) at different operating temperatures (700°C, 660°C, 620°C, and 580°C) and design conditions. Simulated results are compared with experimental data, and the impact of various operating and design parameters on SOFC performance is examined. Findings indicate that kinetic and concentration overpotentials in an anode-supported SOFC are lower than ohmic overpotentials, even at higher current densities. Furthermore, ohmic overpotential is identified as the primary contributor to total cell potential loss, highlighting the need for its minimization to improve cell performance.

Effects of Oxygen Concentration on Soot Formation in Ethylene and Ethane Fuel Laminar Diffusion Flames

In studying the effects of oxygen concentration and molecular structure on the morphologies of the soot particles produced by hydrocarbon fuels, ethylene and ethane were chosen as experimental fuels. With a Gülde laminar coaxial diffusion flame device, a soot particle device was used to sample soot particles at different oxygen concentrations (21%, 24%, 26%, 28%, and 31%) and at different heights above a burner (HABs = 10 mm, 20 mm, 30 mm, 40 mm, and 50 mm). High-resolution transmission electron microscopy (HRTEM) was used to scrutinize and analyze the soot particles at varying oxygen concentrations. The findings suggest that at the same oxygen concentration, ethylene produces brighter and taller flames. With an increase in the oxygen concentration, ethylene flames and ethane flames gradually decrease in height and become brighter. With an increase in the HAB, the average primary soot particle diameter (Dp) increases initially and then decreases, the fractal dimension (Df) increases, and the aggregates transition from strips and chains to clusters. At the same flame height (HAB = 30 mm), the Dp decreases, the Df increases, the carbon layer torsion resistance (Tf) and the carbon layer spacing (Ds) increase, and the carbon layer changes from a parallel arrangement to a curved arrangement to form denser network aggregations.

Templating-induced graphitization of novolac using graphene oxide additives

Increasing graphite demand for energy storage applications creates the need to make graphite using precursors and processes that are affordable and friendly to the environment. Non-graphitizing precursors such as biomass or polymers are known for their low cost and sustainability; therefore, graphitizing them will be an accomplishment. In this work, a process of converting a non-graphitizing precursor, phenolic resin novolac (N), into a graphitic carbon is presented. This was achieved by the addition of five additives categorized as graphene oxide (GO) and its derivatives with varied oxygen concentrations. The hypothesis is that the additives act as templates that promote matrix aromatic alignment to their basal planes during carbonization (physical templating) in addition to forming radical sites that bond to the decomposing matrix (chemical templating). Results showed that the addition of reduced graphene oxide (RGO) additives of approximately 15.4 at.(%) oxygen content to the novolac matrix (RGO-N) show the best graphitic quality. In contrast, the addition of GO additive of twice or more oxygen content ≥ 30.8 at.(%) to the novolac matrix (GO-N) led to poor graphitic quality. This suggests that there is an optimum amount of oxygen content in GO additives needed to induce graphitization of the novolac matrix.

Oxygen regulation of microbial communities and chemical compounds in cigar tobacco curing.

Curing is a critical process that determines the sensory quality of cigars. The impact of oxygen on cigar curing and the mechanisms by which it regulates microbial changes affecting cigar quality are not well understood. In this study, we selected handmade cigars from the same batch and conducted curing experiments in environments with varying oxygen concentrations (equivalent to 0.1%, 6-12, and 15% of atmospheric oxygen concentration). We collected samples over 60 days and analyzed the distribution of microbial communities using high-throughput sequencing. Combined with the analysis of total sugars, proteins, flavor substances, and other chemical compounds, we elucidated how different oxygen concentrations affect the cigar curing process, influence microbial community succession, and ultimately impact cigar quality. Our results revealed significant differences in bacterial community composition under different oxygen conditions. Under aerobic conditions, Cyanobacteria were the dominant bacteria, while under oxygen-limited conditions, Staphylococcus and Corynebacterium predominated. As oxygen concentration decreased, so did the richness and diversity of the bacterial community. Conversely, oxygen concentration had a lesser impact on fungi; Aspergillus was the dominant genus in all samples. We also found that Enterococcus showed a positive correlation with aspartic acid, alanine, and 4-aminobutyric acid and a negative correlation with cysteine. Cigars cured at 15% oxygen concentration for 60 days exhibited optimal quality, particularly in terms of flavor richness and sweetness. These findings suggest that oxygen concentration can alter cigar quality by regulating aerobic and anaerobic microbial community succession. The relationship between specific microbial communities and flavor compounds also provides a theoretical reference for developing artificial control technologies in the cigar curing process.

Study on Variation Law of Hazardous Areas in Goaf Based on Coal Oxidation Kinetics Theory

ABSTRACT Regarding various problems on safety production in coal mines, residual coal in goaf’s spontaneous combustion is extensive, determining its hazardous areas is critical to extinguish or prevent fires in goaf. Taking production practices at the 010803-working face of Wang Wa Coal Mine as background, a combined approach involving on-site experiments, laboratory tests, and numerical simulations is adopted to investigate “three-zone” spontaneous combustion as well as the distribution patterns of temperature fields in shallowly buried coal seams. The mathematical and physical models of spontaneous combustion in goaf are constructed. Upon oxidation of coal at low temperatures, experimental data about the intensity of release of heat and the rate of consumption of oxygen inform the construction of a kinetic model for coal oxidation in goaf. Utilizing field-measured data on air leakage, a distribution model for permeability within the working face’s goaf is constructed. To study combustion “three-zone” and temperature field distribution patterns in goaf under various air supply volumes, as well as to quantitatively analyze the relationship between the width and area of oxidation zones, the area of high-temperature areas, and the distribution of high-temperature sites in the goaf, with relation to the working face’s supply volumes of air. The results show that the maximum simulated air leakage in the goaf of the working face is 148.03 m3/min, with a relative error of just 1.4% compared to the measured value. Furthermore, validation confirms that the simulated oxygen concentration variation pattern closely aligns with the measured oxygen concentration. As the airflow rate at the working face increases, the oxidation zone width at the intake side gradually grows. While on the return side, it gradually decreases, resulting in a maximum width difference of 22.6 m. The goaf area’s concentration of oxygen exhibits an “S” shape distribution pattern. The overall temperature change range within the high-temperature zone of the goaf is 4.5 K, gradually migrating toward the deeper areas. As the air supply rate rises, oxidation zone area gradually decreases, exhibiting an overall sinusoidal distribution. Concurrently, the high-temperature zone area progressively expands, conforming to a Boltzmann function distribution. When the Air supply rate is 800 m3/min to 1120 m3/min, the areas of the two are linearly correlated with the air supply volumes. Under varying air supply volumes, the position of the high-temperature point within the goaf changes in both strike and dip directions, and the relative distance with the intake air corner follows an exponential function in both strike and dip directions. Through comprehensive analysis, it is concluded that the actual air supply volume on-site should ideally range between 800 m3/min and 1120 m3/min. This range effectively prevents and controls the hazardous area of spontaneous combustion in the goaf and optimizes the ventilation scheme.

Long term relationships of electron density with solar activity

Greenhouse gases such as carbon dioxide and methane that are causing climate change may cause long term trends in the thermosphere and ionosphere. The paper aims to contribute to explore long term effects in the ionosphere focusing on the impact of solar activity changes. Peak electron density data derived from vertical sounding measurements covering 65 years at the ionosonde stations Juliusruh (JR055), Boulder (BC840) and Kokubunji (TO536), have been utilized to estimate the long-term behavior of daytime ionospheric F2 layer ionization in relation to the solar 10.7 cm radio flux index F10.7. In parallel, Global Navigation Satellite System (GNSS) based vertical total electron content (TEC) data over the ionosonde stations in combination with the peak electron density data have been used to derive the equivalent slab thickness τ for estimating long-term behavior in the time period 1996-2022. A new approach has been developed for deriving production and loss term proxies for studying long-term ionization effects from F2 layer peak electron density and TEC data. The derived coefficients allow estimating the long-term variation of atomic oxygen and molecular nitrogen concentrations including their ratio during winter months. The noon-time slab thickness values over Juliusruh correlate well with the decrease of F10.7 and the F2 layer peak height and enable estimating the neutral gas temperature. The equivalent slab thickness decreases by about 20 km per decade in the period 1996-2022, indicating a thermospheric cooling by about 100 K per decade for Juliusruh. Whereas the oxygen concentration decreases, the loss term, considered as a proxy for molecular components of the neutral gas, in particular N2, increases with the long-term solar activity variation. Considering 11 years averages of the production and loss terms under wintertime conditions, the long-term study reveals for the O/N2 ratio a percentage decrease of 5% per decade and for F10.7 about 3.1% per decade in a linear approach referred to the year 1970. Linear models of 11 years averaged NmF2 and foF2 from corresponding F10.7 show a very close correlation with the temporal variation of F10.7 until about 1990. The root mean square errors are in the order of 1.0 -1.3 ‧1010m-3 for NmF2 and 0.03-0.05 MHz for foF2. After 1990 the linear models clearly deviate from F10.7 at all selected ionosonde stations indicating a non-local effect.

Oxygen concentration – A governing parameter for microstructural tailoring of duplex AlCrSiON coatings for superior mechanical, tribological, and anti-corrosion performance

This study investigates the impact of increasing oxygen levels on structure, and mechanical properties and tribological performance of duplex AlCrSiON coatings. AISI H13 steel and tungsten carbide substrates are coated using arc ion plating with increasing oxygen flow rate up to 200 sccm with varying oxygen concentration. High-resolution transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and three-dimensional profilometer are used to study morphological and structural evolution. Correspondingly, the coatings are assessed for hardness, adhesion strength, friction coefficient, and resistance against corrosion and wear. A 50–100 sccm oxygen flow rate is considered as an optimal range to receive lower surface roughness. Generally, the addition of oxygen has compromised hardness and friction coefficient but improve adhesion strength, wear and corrosion resistance with increasing oxygen concentration. The immersion tests have identified pitting corrosion as a dominating failure mechanism for AlCrSiON coatings when exposed to molten A380 aluminium alloy. This corrosion resistance stems from their dense microstructure, excellent thermal stability, and the presence of fcc-(Al, Cr)2O3 phase structure. This study demonstrates that controlled oxygen concentration is a crucial parameter for tuning the microstructure of AlCrSiON coatings to achieve superior mechanical, tribological, and anti-corrosion performance, particularly for high-pressure die-casting applications.

Co-pyrolysis characterization of pre-oxidized lignite and corn stover

In this paper, low-rank lignite and corn stover were pre-oxidized at 200 °C with varying oxygen concentrations (0 %, 6 %, 21 %). The study investigated the effects of pre-oxidation on the physical and chemical properties of lignite and stover, including composition, functional group structure, etc. Subsequently, co-pyrolysis experiments were conducted on the pre-oxidized lignite and stover at 700 °C. The study examined the characteristics of the co-pyrolysis of lignite and corn stover under different oxygen concentrations. The results showed that pre-oxidation could effectively increase the content of fixed carbon in the raw materials, elevate the content of carbonyl and carboxyl groups in the raw materials, and reduce the number of aliphatic hydrocarbon side chains as well as hydroxyl groups. The degree of aromatization of the co-pyrolysis char produced from pre-oxidized lignite and corn stover was enhanced. The 6 % O2 pre-oxidation promoted the pyrolysis degree of the raw materials and intensified the progression of the reaction. The CO2 content of the co-pyrolysis tar was at a minimum of 23.028 % with 0 % O2, and the gas had a maximum calorific value of 11.651 MJ∙Nm−3 at this point. Pre-oxidation had an inhibitory effect on the production of co-pyrolysis tar, and the inhibitory effect became more pronounced with higher concentrations of O2. The higher the oxygen concentration, the more pronounced the inhibition. The addition of oxygen promotes the generation of phenols and ketones in the tar, reducing the content of acids and aldehydes. This improves the quality of the tar but also results in a reduction of aromatic hydrocarbons to some extent.

An experimental and modeling study on extinction strain rate in C2HX flames with varied oxygen content

The extinction strain rates (ESR) is an important physical-chemical properties of fuels. Therefore, an experiment study on ESR is crucial for studying emission reduction techniques. In this work, the ESR and laminar burning velocity (LBV) of C2HX fuels under a wide range of conditions are determined experimentally. Moreover, a series of the reduced mechanisms for predicting ESR and LBV of C2 hydrocarbons (C2H2, C2H4, C2H6) is provided, because the research of mechanism reduction seldom pay attention to ESR and LBV. The contribution of this work is therefore the improvement of understanding of the oxidation characteristics of light C2 hydrocarbons and to provide reduced skeletal mechanisms for those fuels with different levels of accuracy for their interaction with reduced oxygen content. For these gas mixtures, the extinction strain rates (ESR) and the laminar burning velocity (LBV), two important physical-chemical properties, were investigated in a counterflow and a heat flux burner setup under atmospheric conditions (1 bar and 298 K). The LBV of the premixed flames, as well as the ESR of the non-premixed C2Hx/O2/N2 flames, are determined experimentally and compared to the numerical predictions of a detailed mechanism (USC II) and the seven corresponding reduced skeletal mechanisms. The present study highlights the non-linear influence on the ESR of C2 hydrocarbons that were found with decreasing fuel content and decreasing oxygen content in either case. Since C2H2 has a significantly higher reactivity than C2H4 and C2H6, this is manifested in lower ESR and higher LBV for the same conditions. The recently developed species-targeted global sensitivity analysis (STGSA) is used to develop reduced mechanisms, showing that they can reproduce the ESR trends and are within the determined measurement uncertainty in a wide range of operating conditions. In addition, these developed significantly reduced mechanisms remain good at predicting the laminar burning velocity. The research generated a unique experimental dataset of the ESR and LBV of C2Hx which was also used to develop reduced mechanisms. Sensitivity analysis for the ESR and LBV gives insight into the difference between ESR and LBV calculations.

3D oxygen vacancy distribution and defect-property relations in an oxide heterostructure

Oxide heterostructures exhibit a vast variety of unique physical properties. Examples are unconventional superconductivity in layered nickelates and topological polar order in (PbTiO3)n/(SrTiO3)n superlattices. Although it is clear that variations in oxygen content are crucial for the electronic correlation phenomena in oxides, it remains a major challenge to quantify their impact. Here, we measure the chemical composition in multiferroic (LuFeO3)9/(LuFe2O4)1 superlattices, mapping correlations between the distribution of oxygen vacancies and the electric and magnetic properties. Using atom probe tomography, we observe oxygen vacancies arranging in a layered three-dimensional structure with a local density on the order of 1014 cm−2, congruent with the formula-unit-thick ferrimagnetic LuFe2O4 layers. The vacancy order is promoted by the locally reduced formation energy and plays a key role in stabilizing the ferroelectric domains and ferrimagnetism in the LuFeO3 and LuFe2O4 layers, respectively. The results demonstrate pronounced interactions between oxygen vacancies and the multiferroic order in this system and establish an approach for quantifying the oxygen defects with atomic-scale precision in 3D, giving new opportunities for deterministic defect-enabled property control in oxide heterostructures.

Effects of oxygen concentration on the corrosion behavior of high entropy alloy AlCoCrFeNi in simulated deep sea

In light of the low dissolved oxygen concentration in the deep sea, the corrosion mechanisms of the high entropy alloy (HEA) AlCoCrFeNi in artificial seawater with varying oxygen concentrations (2.0, 4.0, 7.0 mg/L) were studied. As the oxygen concentration decreases, the alloy's free corrosion potential decreases, and at 2.0 mg/L, the corrosion rate is 421 times higher than that at 7.0 mg/L. The corrosion form transforms from pitting to uniform corrosion. The primary reasons for this are the passivation film is thin under low oxygen concentration conditions, as well as the preferential dissolution of the alloy elements Al and Ni due to their high activity and “local acidizing” properties, respectively. In designing a super corrosion-resistant high entropy alloy for use in the deep sea, it is advisable to avoid the use of element Al and to add Ni with caution.

VOF based model of numerical simulation for single aluminum droplet evaporation and combustion

ABSTRACT This study investigates the combustion of a single aluminum droplet in a high-temperature convective setting, focusing on the interplay between the environment and droplet evaporation combustion. Using the VOF numerical method, a two-dimensional multiphase flow combustion model for micron-sized aluminum droplets is developed. Experimental validation compares predicted droplet diameter with experimental data. The combustion behavior of aluminum droplets in high-temperature convective environments is analyzed, emphasizing gas-phase combustion during stable stages. Parametric variations in flow velocity and oxygen concentration reveal the formation of vortices around the droplet, influencing aluminum vapor accumulation and evaporation rates. Combustion primarily occurs at the droplet’s windward side, with reaction rates decreasing downstream. Increasing gas velocity from 1.5 m/s to 3 m/s thins the aluminum vapor concentration boundary layer, boosting combustion rates by 35%. Elevating oxygen concentration from 20% to 50% brings the flame closer to the droplet, accelerating combustion rates by 2.7 times, suggesting oxygen concentration’s role in reaction acceleration and combustion duration reduction. This research offers insights for simulating aluminum droplets in propellant applications.

Investigation of optoelectronic properties of tin-doped indium oxide thin films and contact resistivity with silver film: Role of oxygen concentration variation during sputter deposition

We have investigated the optoelectronic properties like carrier concentration (NITO), mobility (µITO), work function (ϕITO), optical transmission and constants, and sheet resistance (Rsh) of tin-doped indium oxide (ITO) films with the variations in the oxygen flow rate during reactive sputter deposition with the Ar:O2 plasma. Initially, we also analyzed the generated Ar:O2 plasma parameters (ion energy and density, electron temperature, and energy distribution) using the Langmuir probe. The ITO films' optoelectronic properties were investigated systematically in as-deposited and annealed (150 to 200 °C) conditions with varying O2 flow rates. By varying the O2 flow rate, we observed the carrier mobility (µITO) of the ITO films in the range of 31-47 cm²/V-s, carrier concentration (NITO) in the range of 2.16 × 1019 - 5.22 × 1020 cm−3, and resistivity in the range of 3.57 × 10−4 - 8.95 × 10−4 Ω-cm. We were able to separate the roles of grain boundary and ionized impurity scatterings in modifying µITO as a function of NITO in the ITO films. Finally, using the transfer length method, we observed a contact resistivity of ∼3 mΩ-cm² from the ITO/Ag interface at the NITO of ∼4.08 × 1020 cm−3.

NIR‐II Ratiometric Fluorescent Nanoplatform for Real‐Time Monitoring and Evaluating Cancer Sonodynamic Therapy Efficacy

AbstractReal‐time monitoring the therapeutic process of sonodynamic therapy (SDT) is essential to optimize the treatment course in time and eventually improve the efficacy. The generation of singlet oxygen (1O2) is a quintessential characteristic of SDT, which permits non‐invasive monitoring of SDT by real‐time imaging of 1O2 inside the tumor. Nonetheless, the majority of probes are unable to measure 1O2 in real time because of its short half‐life and strong oxidative capacity. Here, the study constructs a ratiometric nanoplatform (DTPI) utilizing two fluorescent probes and the sonosensitizer TiO2. The poisonous 1O2 generated by DTPI following ultrasonic (US) radiation efficiently destroys tumor cells. The structural disruption of fluorescent dye IR‐1061 by 1O2 leads to a reduction in the DTPI fluorescence signal at 1100 nm, while US radiation has no impact on the fluorescence signal at 1550 nm. Thus, DTPI provides a precise and consistent reflection of the treatment efficacy at the tumor site, leveraging the ratiometric fluorescence signal and variations in oxygen content throughout the treatment process. This ratiometric‐fluorescence‐based reflection strategy establishes an effective and dependable platform for the real‐time monitoring and assessment of the cancer therapeutic effect through ratiometric probes.