Increasing Oxygen Content Research Articles

Pt/Pd dual-modified porphyrin metal-organic frameworks for NIR-II photothermal-enhanced photodynamic/catalytic therapy

Photodynamic therapy (PDT) and catalytic therapy were promising treatment modes, but tumor hypoxia and poor catalytic activity severely limited their efficacies. Herein, using a porphyrin metal–organic framework (PCN-224) as nanocarrier, a platinum/palladium (Pt/Pd) dual-modified PCN-224 nanoprobe (PCN-224-Pt@Pd) with strong peroxidase (POD)/catalase (CAT)-like activities was developed, achieving photothermal-promoted PDT/catalytic therapy. Compared with single ultrasmall Pt modifying, CAT-like activity of Pt/Pd dual-modifying increased oxygen concentration from 6.24 to 9.35 mg/L, which improved singlet oxygen (1O2) yield from 63.8 % to 82.9 %. Moreover, POD-like activity of Pt/Pd dual-modifying significantly accelerated hydroxyl radicals (·OH) generation. Importantly, PCN-224-Pt@Pd possessed near-infrared II (NIR-II) photothermal effect with a high efficiency (55.6 %), which further promoted ·OH production. Under combined therapy of PCN-224-Pt@Pd, the cell survival rate greatly reduced to 5.8 %, and the tumors were cured, suggesting NIR-II photothermal-enhanced PDT/catalytic therapy.

Influence of La3+ ions on the structural, elastic, optical, and radiation shielding properties of Cr2O3-Doped heavy metal glasses

This study investigates the effect of La³⁺ rare earth ions on the structural, elastic, optical, and radiation shielding features of heavy metal borate glass (B₂O₃-PbO) doped with Cr₂O₃. Density measurements and FT-IR spectra analysis revealed the role of La3+ ions as a network modifier, where successive additions of La2O3 content led to a gradual increase in the density and an increase in the non-bridging oxygen content resulting from the structural transformation between the BO4 and BO3 units. The significant improvement in the elastic modulus and microhardness factor moduli was confirmed by calculating the change in ultrasonic velocities through the glassy system. The structural modifications induced by La³⁺ ions narrowed the band gap and increased the Urbach energy, indicating higher disorder within the glass network. The linear refractive indices increased due to increased optical basicity and electronic polarization. Optical absorption results showed that Cr⁶⁺/Cr³⁺ ions occupy octahedral/tetrahedral sites, with the tendency for Cr³⁺ cations to occupy more octahedral sites with increasing La₂O₃ content. The produced samples showed a greenish-yellow color caused by the absorption band centered at ∼415 nm associated with the electronic transition ⁴A₂g(F)→2Eg(G). The ligand field effect highlighted the significance of La³⁺ cations in increasing the crystalline field intensity surrounding Cr³⁺ cations and reducing the nephelauxetic ratio, signifying enhanced covalent character between Cr³⁺ cations and neighboring ions. Moreover, the radiation shielding capabilities of the glassy system were analyzed and compared with standard shielding materials, confirming superior shielding performance in samples with the highest La₂O₃ content.

Cooling radiative forcing effect enhancement of atmospheric amines and mineral particles caused by heterogeneous uptake and oxidation

Abstract. The warming radiative forcing effect (RFE) derived from atmospheric amines attracts a lot of attention because of their contribution to brown carbon. Herein, the enhanced influence of amines (methyl-, dimethyl-, and trimethylamine) on cooling RFE of mineral particles is first confirmed at visible wavelengths. Present results state heterogeneous uptake and oxidation reactions of atmospheric amines are feasible on mineral particles under clean and polluted conditions, which are proven by related thermodynamics and kinetics data obtained using combined classical molecular dynamics and density function theory methods. Based on mineral particles, simple forcing efficiency (SFE) results explain that amine uptake induces at least 11.8 %–29.5 % enhancement on cooling RFE of amine–mineral particles at visible wavelengths. After amine heterogeneous oxidation, oxidized amine–mineral particle cooling RFEs are furthermore enhanced due to increased oxygen contents. Moreover, oxidized amine–mineral particles under clean conditions show 27.1 %–47.1 % SFE increments at 400–600 nm, which is at least 11.3 % higher than that of itself under polluted conditions, due to high-oxygen-content product formation through amine autoxidation. Our results suggest cooling RFE derived from atmospheric amines can be equally important to their warming RFE on the atmosphere. It is necessary to update the heterogeneous oxidation mechanism and kinetics data of amines in atmospheric models in order to accurately evaluate the whole RFE caused by amines on the atmosphere.

THE EFFECT OF TREATING HEAVY OIL WITH ISOPROPYL ALCOHOL ON THE COMPOSITION AND STRUCTURE OF RESINS

The effect of heavy oil treatment with isopropyl alcohol (IPA) for 8 h at a temperature of 25-100 °C on the composition and structure of resins is investigated. The objects of investigation were heavy oil from the Zyuzeevskoye field (the Republic of Tatarstan) and resins isolated from this oil. It is established that the resin content increases by almost 3 wt% as a result of heavy oil treatment with IPA at 100 °C. It is shown than an increase in the temperature of oil - IPA (20 wt%) mixture treatment from 25 to 100 °C causes an increase in sulphur and oxygen content in resins by 0.5 and 0.8 wt%, respectively, and a decrease in the Н/С atomic ratio from 1.40 to 1.38. The aromaticity factor of resins increases by 0.17 %, while the fraction of aliphatic carbon decreases. It is concluded that oil treatment with isopropyl alcohol, aimed at a decrease in the content of resinous and asphaltenic substances, is unreasonable because it causes unfavourable formation of the additional amount of resins.

Functional co-delivery nanoliposomes based on improving hypoxia for increasing photoimmunotherapy efficacy of cold tumors

Cold tumors lack T cells infiltration and have low immunogenicity, resulting insufficient immunotherapy response. Therefore, how to realize the transformation from cold tumor to hot tumor is an urgent problem to be solved. Photodynamic therapy can induce immunogenic death of tumor cells (ICD) and activate T lymphocytes to produce tumor immune response. However, hypoxia in the cold tumor microenvironment limits the effectiveness of photodynamic therapy. So in this article, MET-HMME/CAT-HMME@Nlip as a functional co-delivery nanoliposomes was constructed based on overcoming the above problems. Firstly, the oxygen-deficient state could be improved by the following two ways, one is catalase loaded in CAT-HMME@Nlip can decompose high concentration hydrogen peroxide to produce oxygen, and the other is metformin loaded in MET-HMME@Nlip can decrease oxygen consumption by inhibiting of mitochondrial respiration. And then with the increase of substrate oxygen concentration, the sensitivity of photodynamic therapy can be greatly improved and the anti-tumor immune response by PDT-induced ICD can also be enhanced obviously. In addition, metformin could act as a small molecule immune checkpoint inhibitor to reduce the expression of PD-L1 on the surface of tumor cells, thereby effectively improving the specific killing ability of cytotoxic T cells to tumor cells which could not only erasing the primary tumor, but also inhibiting the growth of simulated distant tumors through the immune memory function. This study provides a new idea for improving the clinical treatment effect of hypoxic cold tumors, especially for tumors that could not benefit from immunotherapy due to low or no expression of PD-L1 protein on the surface of tumor cells.

Temperature evolution of laser-ignited micrometric iron particles: A comprehensive experimental data set and numerical assessment of laser heating impact

This study examines the effects of laser heating on the ignition and critical combustion characteristics, such as temperature and burn time, of individual iron particles. It provides time-dependent temperature profiles of laser-ignited particles across a broad spectrum of particle size distributions and oxygen concentrations obtained from experiments, which are a useful database for further development and validation of iron particle combustion models. The herein reported datasets significantly complement those existing in the literature. In the current study, the raw data are thoroughly re-evaluated using refined approaches. For the experimental canonical configuration of single iron particle combustion, an ignition system based on laser heating provides several advantages in overcoming temperature field uncertainties and facilitating controlled environments for optical diagnostics. Despite the inherent uncertainties in laser heating, associated with non-uniform intensity profiles and particle size variations, this study addresses the critical question of how these uncertainties affect in situ measurements of particle temperature and time to reach peak temperature. This study, conducted using a numerical model, reveals a dependence of the particle temperature after laser heating on particle size. However, this dependence does not significantly impact the key parameters of iron-particle combustion, such as the maximum temperature and burn time of the laser-ignited iron particle. The study also presents a comparison between the simulated particle temperature histories and those derived from two-color pyrometry measurements for a wide range of particle size distributions and oxygen concentrations. Notably, by implementing a laser-heating sub-model into an iron particle combustion model, assuming external-diffusion-limited oxidation only up to stoichiometric FeO, the temperature evolution up to the maximum temperature is reasonably captured for a wide range of particle sizes (20–53μm) and oxygen volumetric fractions (14–21vol% O2 mixed with N2). However, with increasing oxygen concentration, the external-diffusion limited model significantly overestimates the heating rate and subsequently the maximum particle temperature.

Towards the Direct Observation of the Local and Electronic Structure Evolution of Positive Electrode Materials by X-Ray Raman Scattering and X-Ray Emission Spectroscopy

The emergence of high brilliance synchrotron sources and the availability of more sophisticated infrastructure have opened doors to advanced material characterization, enabling a profound understanding of new processes and mechanisms in battery research. [1] More specifically, non-resonant Valence-to-Core X-ray emission spectroscopy (VtC-XES) and X-ray Raman scattering (XRS) stand out as complementary photon-in/photon-out X-ray spectroscopy techniques. The unique capability of these techniques lies in their access to soft X-ray edges using a hard X-ray beam, providing comprehensive information on both the electronic and local structure, due to their high sensitivity to local structure and coordination. [2,3] In this work, two different families of materials with different compositions and crystal structures are studied using XES and XRS.The first part focuses on the detailed study of oxygen substituted KVPO4F1-xOx (x = 0, 0.25, 0.5, 0.75, 1) using VtC-XES combined to ab initio theoretical calculations. The average working potential increases with increasing oxygen content by activating the V3+/4+ and V4+/5+ redox couples and replacing the VO4F2 “ionic” entity by {V=O}O5 unit with a highly “covalent” vanadyl-type bond. [4] VtC-XES allowed us to distinguish the contributions of V-F, V-O, and V=O bonds in the local environment, with spectral intensities highly correlated to the F- and O2- anionic composition. In addition, specific spectral evolutions are also associated to the presence of highly covalent V=O bonds, strongly influencing the electrode potential of the material.The second part examines a series of electrochemically obtained LiyNiO2 layered oxide materials (y = 0.02, 0.25, 0.33, 0.5, 0.67, 1.0). VtC-XES performed at the Ni Kβ emission line allows to study the local structure evolution around Ni, whereas XRS spectroscopy at both the O K-edge and Ni L2,3 L-edges gives an access to the interplay between Ni and O through the hybridized states of Ni 3d and O 2p. [5] This work provides a survey on both the cationic and anionic redox processes, and unveils the underlying phenomena related to the charge compensation processes occurring in this material.Overall, we present a comprehensive study of different polyanionic and layered oxide positive electrode materials using complementary X-ray spectroscopic techniques to probe both the local and electronic structures. We demonstrate that they allow to follow and understand evolution and changes in the local structure in materials of intricate crystal structures.AcknowledgementThis work was supported by the DESTINY Marie Skłodowska-Curie Actions COFUND PhD Programme (Grant Agreement #945357) co-funded by the European Union's Horizon2020 research and innovation program and the Synchrotron SOLEIL. ANR is also acknowledged for funding the RS2E network through the STORE-EX Labex Project ANR-10-LABX-76-01. Alistore-ERI network is also acknowledged.

LiNO3-Based Deep Eutectic Mixtures Comprising Organic Additives As Promising Electrolytes for Stable Li-Metal Batteries

Deep eutectic electrolytes have emerged as a novel energy storage solution, presenting distinct advantages over traditional ionic liquid electrolytes. These advantages include a high ion concentration, cost-effective, wide electrochemical window, and inherent safety.In this study LiNO3, which is valuable additive but difficult to melt in carbonate electrolytes, was used as the lithium salt for a deep eutectic solvent (DES) electrolyte. LiNO3 demonstrated its capability to form deep eutectic solutions with N-methyl acetamide (N-MAc) and Methyl carbamate (MCB) in a 1:4 molar ratio. An suitable additives was introduced to study the effect on electrochemical behaviors.Li//Cu asymmetric cells was utilized to evaluate the coulombic efficiency (CE) of lithium plating/stripping with various electrolytes. The lithium plating/stripping stability is investigated by evaluating the cycle life of Li//Li symmetric cells. The electrochemical window is determined by the Li//Pt asymmetric cells underwent linear sweep voltammetry (LSV). A commercial LiMn2O4 (LMO) is used as cathode to assemble the Li//LMO lithium-metal cells to evaluate cycle stability, rate capabilities, and AC impedance. The physical properties of the electrolytes underwent systematic analysis using Fourier Transform Infrared Spectroscopy (FT-IR), Raman spectroscopy, Differential Scanning Calorimetry (DSC), conductivity, and viscosity measurements. Post-analysis of Li//Cu asymmetric cells revealed additive-induced differences. SEM and EDS analyses unveiled elemental variations on copper foil, and X-ray Photoelectron Spectroscopy (XPS) provided surface insights.For the first system, the LiNO3 and N-MAc electrolyte exhibited an extended plating/stripping cycle life of reaching 450 hours with the addition of 10 wt% VC in Li//Li symmetrical cell. Addition VC as additive significantly improved conductivity and viscosity. Surprisingly, in Li//Cu asymmetrical cells, 5 wt% VC demonstrated better stability. The Li//Pt asymmetrical cells shows the electrolyte decomposition is occurs at 5V, which is high compared to organic electrolyte. In Li//LMO lithium-metal cells, an impressive 2000 cycles were achieved, with a remarkable 80% capacity retention in rate capabilities testing at high current density and sustained cycling up to 1000 cycles at lower current density. Raman and FT-IR analysis revealed blue shifts in characteristic peaks of C=O and N-H, indicating lithium ions from LiNO3 indeed interact with N-MAc. SEM and EDS testing confirmed that the presence or absence of VC influenced lithium-ion deposition. In the presence of VC, there was a notable increase in oxygen, nitrogen, and carbon content, imply that the enhanced lithium-ion deposition and dissolution capabilities.For the second system, the LiNO3 and MCB electrolyte system, 8 wt% FEC addition in Li//Li symmetrical cells resulted in a cycle life of only 60 hours. Li//Cu asymmetrical cells showed improved lithium-ion deposition and dissolution with FEC for 12 cycled. Li//Pt asymmetrical cells displayed a decomposition at 4.6V. Li//LMO lithium-metal cells with 5 wt% FEC exhibited stability, cycling up to 120 cycles. Raman and FT-IR analysis indicated blue shifts in the characteristic peaks of C=O and N-H stretching vibrations, signifying deep eutectic interactions between LiNO3 and MCB. Red shifts were observed in N-H bending vibrations. FEC addition improved conductivity and viscosity. SEM and EDS testing demonstrated that the presence or absence of FEC affected lithium-ion deposition. In the presence of FEC, components such as oxygen, nitrogen, carbon, and fluorine were detected, with fluorine constituting a significant 26.70%, indicating improved lithium-ion deposition and dissolution capabilities. XPS peaks corresponding to Li 1s, F 1s, and N 1s, affirming the efficacy of FEC in promoting lithium-ion deposition.In conclusion, the deep eutectic electrolyte formed by LiNO3 and N-MAc in a 1:4 molar ratio demonstrated superior stability. Additives proved effective in improving electrolyte properties without compromising coordination. Both electrolytes exhibited comparable cycle life, emphasizing their suitability for positive electrode materials like LMO. Moreover, sustained high current density in rate capabilities testing further highlighted their potential for practical applications. Figure 1

Oxygen-doping induced tunable optoelectronic properties of two-dimensional (2D) 1T-MgF2 monolayer: A first-principles study

Here, we studied the physical properties of atomic oxygen-doped two-dimensional (2D) MgF2 monolayer using density functional theory. The undoped MgF2 exhibits an insulating behavior. However, it shows a small amount of incident light absorption in the visible region when an F-atom is substitutional doped with an oxygen (O) atom. Further, the increasing oxygen concentration shows an enhanced optical absorption of light in the visible spectrum. Hence, it can be used as an absorption band pass/stop filter. The absorption spectrum is consistent with the calculated extinction coefficient. The increased absorption shows the improved conductivity of doped MgF2. Moreover, the dielectric constant and refractive index increase with increasing O-doping concentration. Its refractive index enhances more than that of silicon (3.9). The increased O-doping also enhances the reflection of light in the microwave to the infrared region, which is justified by the transmission spectrum. The energy losses also increase with increasing O-concentration. These losses show the existence of plasma resonances. The dielectric and optical responses show that it behaves like a high-k dielectric material for large O-doping concentrations. The discussion above indicates that the O-doped 2D MgF2 monolayer is an excellent electronic and dielectric material for electronic, optical, and optoelectronic applications.

Biomedical application of microalgal-biomaterials hybrid system.

Microalgae are a group of microorganisms containing chlorophyll A, which are highly photosynthetic and rich in nutrients. And they can produce multiple bioactive substances (peptides, proteins, polysaccharides, and fatty acids) for biomedical applications. Despite the unique advantages of microalgae-based biotherapy, the insufficient treatment efficiency limits its further application. With the development of nanotechnology, the combination of microalgae and biomaterials can improve therapeutic efficacies, which has attracted increasing attention. In this microalgal-biomaterials hybrid system, biomaterials with excellent optical and magnetic properties play an important role in biological therapy. Microalgae, as a natural vehicle, can increase oxygen content and alleviate hypoxia in diseased areas, further enhancing therapeutic effects. In this review, the synergistic therapeutic effects of microalgal-biomaterials hybrid system in different diseases (cancer, myocardial infarction, ischemia stroke, chronic infection, and intestinal diseases) are comprehensively summarized.

Wettability tuning on stainless steel LIPSS by laser oxidation and its implication on cavitation bubble dynamics

The modification of surface wettability of stainless steel is essential for many biological applications and industrial implementations. Having a hydrophobic or hydrophilic surface is ideal depending on its application. In this study, the wettability tuning of stainless steel was carried out by producing LIPSS at different laser peak energies. Results showed non-significant changes in the periodicity of the ripples, however hydrophilicity increased with greater laser energies. Raman spectroscopy and SED analysis demonstrated the presence of iron oxide peaks and increased oxygen concentration, demonstrating a chemical surface modification governed by oxidation. Transitions from hydrophilic to hydrophobic surfaces were accomplished by ethanolic triethoxyoctylsilane coated LIPSS. Hydrophobicity enhancement was achieved by the adsorption of organic species promoted by the oxide layer at the ripples. The dynamics of cavitation bubbles close to the coated LIPPS were analyzed. A reduction of the main bubble lifetime with hydrophobicity, whereas a delay of collapse time and deformation of the rebound bubble were found. This led to an experiment for erosion testing producing multiple cavitation events. An increment of surface damage area with increased hydrophobicity was observed. This was attributed to longer collapse times of the rebound bubble which led to stronger shockwaves at the samples surface. This work demonstrates a simple method to tune the surface wettability of stainless steel by laser oxidation, which is a crucial factor for applications related to cavitation phenomena.

Increased oxygen content in biochar lowered bioavailability of polycyclic aromatic hydrocarbons–related toxicity to various organisms

Agricultural or environmental application of biochar (BC) is connected with the introduction of biochar-derived components among which polycyclic aromatic hydrocarbons (PAHs) and heavy metals are the most toxic. Their presence and bioavailability are crucial considering biochar toxicity. The effect of feedstock and pyrolysis temperature on the physicochemical properties of produced biochar and contaminant content was established and combined with toxicity to a broad range of living organisms. The obtained data revealed that predicting the bioavailability of PAHs using the total content is misleading. The toxicity was influenced by factors in the following way: the bioavailable PAHs > ash > total PAHs content in BC stressing the role of BC physicochemical characteristics. Among tested BC properties, surface functionalization, e.g. presence of oxygen-containing functional groups was crucial in revealing the toxicity. The data clearly indicate that additional research is required to determine BC’s impact on various organisms and performing one ecotoxicity test is not sufficient.

Marine redox and nutrient dynamics linked to the Cambrian radiation of animals

Abstract The early Cambrian witnessed an increase in metazoan ecosystem complexity, likely linked to enhanced oxygen and nutrient availability. However, while improved stratigraphic and geochemical records suggest that the Cambrian explosion occurred under highly dynamic redox conditions, mechanistic links to nutrient availability and early Cambrian evolutionary innovations are poorly constrained. Here, we report paleoredox and nutrient data for two drill cores documenting late Cambrian Stage 2 to Stage 3 (ca. 522–514 Ma) strata from the Yangtze block, South China. The development of water-column euxinia during Cambrian Stage 2 led to extensive recycling of P, fueling elevated primary production and hence an increase in atmospheric and shallow-marine oxygen concentrations. The resulting expansion of oxygenated shelf area promoted sedimentary P retention and, in combination with a diminished supply of P from upwelling, drove a transition to oligotrophic shallow-marine conditions during Cambrian Stage 3. Reduced primary production and limited water-column oxygen consumption allowed for the stabilization of oxygenated continental shelf habitats that supported a burgeoning biotic complexity.

Temperatures and hypolimnetic oxygen in German lakes: Observations, future trends and adaptation potential.

We investigated trends in temperature, stratification, and hypolimnetic oxygen concentration of German lakes under climate change using observational data and hydrodynamic modelling. Observations from 46 lakes revealed that annually averaged surface temperatures increased by + 0.5°C between 1990 and 2020 while bottom temperatures remained almost constant. Modelling of 12 lakes predicted further increases in surface temperatures by 0.3°C/decade until the year 2099 in the most pessimistic emission scenario RCP 8.5 (RCP 4.5: + 0.18°C/decade; RCP 2.6: + 0.04°C/decade). Again, bottom temperatures increased much less while summer stratification extended by up to 38days. Using a simplified oxygen model, we showed that hypolimnetic oxygen concentrations decreased by 0.7-1.9mgL-1 in response to the extended stratification period. However, model runs assuming lower productivity (e. g. through nutrient reduction) resulted in increased oxygen concentrations even in the most pessimistic emission scenario. Our results suggest that the negative effects of climate change on the oxygen budget of lakes can be efficiently mitigated by nutrient control.

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.

Analysis of nitrogen adsorption capability at various activation temperatures of Klaten natural zeolite

The Pressure Swing Adsorption (PSA) method operates by passing air through an adsorbent to produce concentrated oxygen gas. Zeolites are commonly utilized as adsorbents due to their ability to adsorb nitrogen from the surrounding air. Two types of zeolites commonly employed are natural and synthetic zeolites. While the utilization of natural zeolites as adsorbents in oxygen purification remains limited, their potential as an alternative adsorbent is worth exploring in this field. This study focused on developing physically activated Klaten natural zeolite as an adsorbent to enhance oxygen purity. Physical activation involved heating for 1.5 hours using an electric oven at four temperature variations (250ºC, 300ºC, 350ºC, and 400ºC). Additionally, four distinct flow rates were tested: 0.1; 0.5; 1.0; and 1.5 lpm. Oxygen purification testing revealed that higher activation temperatures led to greater increases in oxygen concentration. The highest increase of 2.45% was achieved at an activation temperature of 400ºC, while the lowest increase of 1.75% was observed at 250ºC with a flow rate of 0.1 lpm. With a 10-minute holding period, oxygen content during the adsorption process ranged from 1.35% to 2.45%, compared to 0.60%-0.75% without holding. Physical activation of zeolite from Klaten enhanced its nitrogen absorption capacity, indicating the potential of natural zeolite from Klaten for oxygen purification through optimized activation processes, possibly via chemical activation

Effect of oxygen on the microstructure, tensile properties and deformation behaviours of a biocompatible Ti40Zr25Nb25Ta10 high entropy alloy

The effect of oxygen on the microstructure, mechanical properties and deformation behaviours of as-cast biocompatible Ti40Zr25Nb25Ta10Ox (x = 0.5, 1.0 and 2.0 at.%) high entropy alloys (HEAs) was investigated. All three oxygen-doped HEAs solidified as a single body-centred cubic (BCC) phase grain structure with predominantly high-angle grain boundaries following the Mackenzie prediction. Increasing oxygen content significantly increased tensile strength at a rate of about 180 MPa/1.0 at.%, but decreased tensile ductility. However, at the addition level of 0.5 at.% O, the as-cast Ti40Zr25Nb25Ta10O0.5 HEA can achieve a yield strength (σ0.2) of 947 ± 44 MPa and an elongation at break (εf) of 9.5 % ± 1.8 %. These properties make this HEA comparable to medical grade Ti-6Al-4V (wt.%) alloy (ASTM Grade 23 titanium) (σ0.2 ≥ 759 MPa; εf ≥ 10 %) in its ability to absorb energy in plastic deformation, while offering greater resistance to permanent shape changes. Due to the possible strong interaction between oxygen atoms and dislocations through pinning and de-pinning, all oxygen-doped HEAs exhibited discontinuous yielding, whereas the low oxygen base HEA underwent normal yielding. No oxygen clusters were detected through atom probe tomography (APT) analysis. The deformation mechanism depends on oxygen content. The plastic deformation of the Ti40Zr25Nb25Ta10O0.5 HEA occurred through the formation of primary and secondary shear bands. In contrast, planar slip bands and a limited number of primary shear bands (without secondary shear bands) were observed in the Ti40Zr25Nb25Ta10O2.0 HEA. To ensure sufficient ductility, the oxygen content should be limited to 0.5 at.%. Furthermore, at this oxygen content, the corrosion resistance of the Ti40Zr25Nb25Ta10O0.5 HEA in Hank's solution is comparable to that of Ti-6Al-4V.

Experimental and numerical investigations of soot formation in propane laminar coflow flames in O2/N2 and O2/CO2 atmospheres

Oxygen-rich combustion is a new type of clean combustion technology with important application prospects. At present, there are few detailed analyses on the mechanism changes of soot formation under oxygen enrichment of propane. In this paper, the effects of oxygen-rich (O2/N2, O2/CO2) combustion on soot formation in the propane laminar flow coaxial jet diffusion flame were investigated by using the experiment and numerical simulation. The flame image was taken by a color (CCD) camera in the visible band, and the two-dimensional distribution of temperature and soot volume fraction in the flame was reconstructed. In numerical simulation, the soot production model considers a detailed description of nucleation via collisions among heavy polycyclic aromatic hydrocarbons, particle aggregation, polycyclic aromatic hydrocarbons condensation, surface growth and oxidation through the hydrogen abstraction acetylene addition mechanism. The results show that the experimental results were compared with the numerical simulation results, and the numerical simulation results predict the temperature and soot change of oxygen-rich flame well. With the increase in oxygen concentration, the peaks of soot and temperature in the two oxygen-rich atmospheres gradually increased. With the increase in oxygen concentration, the peaks of soot and temperature in the two oxygen-rich atmospheres gradually increased. Comparing the combustion mechanism changes of the two oxygen-rich combustion systems, it was found that the hydrogen abstraction acetylene addition mechanism was the main cause of soot generation. The OH oxidation is dominated near the fuel nozzle side, and O2 oxidation is dominant downstream. With the substitution of CO2 for N2, the chemical effect of CO2 reduces the flame temperature and inhibits the formation mechanism and oxidation mechanism of soot to some extent. This in turn leaded to a reduction in the amount of soot produced.

Research on shock wave driving technology of methane explosion

In order to improve the driving ability of the explosion wave simulation equipment, reduce the erosion effect of condensed explosives on the explosion wave simulation equipment, improve the safety of the test process, and make better use of the meteorological detonation driving method, it is necessary to optimize the source of the shock wave load in the driving section. Based on the finite volume method of FLACS, a methane detonation driving model corresponding to the test is established to explore the feasibility of using methane as an explosion source to test the structure against explosion shock wave. A methane detonation drive test was carried out to verify the accuracy of the numerical model. Finally, an engineering model for attenuation of shock wave overpressure peak value in pipeline is established by dimensional analysis, and the model coefficient is determined by numerical simulation and test data. The results show that the blast pressure is the highest when the methane volume ratio reaches 9.5 vol% in the methane-air mixture. Simply increasing oxygen content has little effect on the peak overpressure and positive pressure duration of shock wave. In the pure oxygen environment, the detonation effect can be achieved when the volume ratio of methane to oxygen is 1:2, and the incident pressure of the shock wave is proportional to the volume of the gas cloud. When the gas cloud volume is constant, a reasonable selection of methane-oxygen mixture ratio can achieve a better detonation effect, which can effectively increase the peak overpressure of the shock wave in the test section. The research results can provide technical reference for the development of new explosion wave simulation equipment.

System simulation and parametric analysis of low-concentration coal mine gas fed SOFC-CHP with deoxygenation and enrichment pretreatment

Solid oxide fuel cell (SOFC) combined heat and power (CHP) can efficiently convert low-concentration coal mine gas (LC-CMG) into clean energy, avoiding the greenhouse effect of LC-CMG. Deoxygenation and methane enrichment pretreatment of LC-CMG can prevent explosion and anode oxidation risk. Herein, a chemical process model of LC-CMG fed SOFC-CHP system with the pretreatment was established to predict the performances under different operating conditions. Performance evaluation and exergy analysis were performed considering the use of oxygen-rich gas from the pretreatment at SOFC cathode. The effects of key operation parameters on system performances were investigated in terms of residual oxygen concentration, inlet methane concentration, fuel flow and fuel utilization. The results indicated that net electrical efficiency and heat supply efficiency can respectively reach 49.13 % and 23.90 % using LC-CMG of 15 % CH4 with enhancing effect of oxygen-rich gas at cathode. The decrease of methane concentration and the increase of residual oxygen concentration and flow rate caused the decreased electrical efficiency but the increased heat supply efficiency due to the enlargement of concentration polarization and heat supply. The optimal operation parameters were recognized by comprehensively considering diverse performance indicators. This work can guide system integration and operation optimization of LC-CMG fed SOFC-CHP.