Oxygen Diffusion Research Articles

The influence of hydrogen and oxygen vacancy concentrations on diffusion coefficients of oxide and hydride ions in reduced barium titanate oxyhydride using molecular dynamics simulation

A molecular dynamics method with a reax force field has been employed to investigate the effect of hydrogen and oxygen vacancy concentrations on the diffusion of oxygen and hydrogen atoms in BaTiO3−xHy□(x-y). The result shows that by using this force field, the BaTiO3−xHy□(x-y) samples are stable under the condition of x < 0.18. Therefore, the samples have been simulated under conditions of (x-y) <0.15, y < 0.18 and x < 0.18. The results reveal that the dominant diffusion dynamics of hydrogen atoms is the motion between next-nearest neighboring oxygen vacancies in the form of hydride. The diffusion coefficients and activation energies are evaluated using mean square displacements and Arrhenius plots. The results show that the activation energies of oxide and hydride ions are close together and are in the range of 0.03–0.9 eV and they both decrease by increasing y. The results also show that the pre-exponential factors of hydrogen and oxygen diffusion are in the range of 10−6 to 0.0045 cm2s-1 and 1.7710−6 to 0.0017 respectively.

Oxidation behavior of Cr–Mn–Si alloyed steel by mold flux melt in high temperatures

The oxidation behavior of a medium carbon Cr–Mn–Si alloyed steel was investigated under a mold flux melt environment exposed to different high temperatures of 1175–1425 °C, and holding time of 5–85 min. The results showed that the thicknesses of oxide layers contained Cr–Mn–Si oxide particles significantly increased from 10 to 183 μm with the increasing of oxidation temperature and holding time. The selective oxidation of Cr, Mn and Si elements in the grain boundaries is caused by the diffusion of free oxygen (O2−) migrating from mold flux to steel matrix, which leads to the growth of oxide layer thicknesses. Moreover, the oxidation rate constant (kp) of the Cr–Mn–Si alloyed steel was revealed under the mold flux environment at the temperatures of 1175–1375 °C. In addition, it was found that the growth kinetics of oxide particles in the oxide layer consists of a rapid growth stage and a slow-steady growth stage, and the growth of oxide particles is co-controlled by the diffusion of O2− within the steel matrix and the competing oxidation reactions involving Fe, Cr, Mn, and Si elements.

Systematic investigations on the oxidation mechanism of Cr coated Zr-4 alloy under different high-temperature steam conditions

Chromium (Cr) coating is a potential candidate material for improving the oxidation resistance and extending rail service life of zirconium (Zr) alloys used in nuclear fuel cladding materials. This study investigates the effect of temperature on the effectiveness of Cr coating on Zr-4 alloy deposited using arc ion plating, revealing the microstructure evolution mechanism of Cr coating in high temperature steam environments. The research results indicate that the oxidation of the Cr coating is slow at 900-1000 °C and that the surface oxide layer, to some extent, hinders the diffusion of oxygen from the outside to the inside. However, at higher temperatures, the oxidation rate of the Cr coating is accelerated, and large bubbles and voids are formed at the interface between the Cr2O3 layer and the residual Cr layer, resulting in the fracture of the oxide layer. At this time, the protective performance of the Cr coating is completely lost. Note that the simultaneous inward diffusion of oxygen and outward diffusion of Zr trigger the occurrence of redox reactions, generating a ZrO2 network. Changes in steam temperature significantly affect the oxidation behavior of Cr coating. As a driving force, temperature accelerates the diffusion of oxygen to the substrate. Conversely, the formed zirconia network also promotes the failure of the Cr coating.

Enhanced ignition and combustion performance of boron-based energetic materials through surface modification and titanium dioxides coating

The present study focuses on the removal of ineffective hydroxyl surface (B–OH) of the shell of pristine boron (B) particles, followed by its modification using a low-cost, eco-friendly, and non-hazardous ethylene glycol (EG). Subsequently, very small-sized titanium dioxide (TiO2) particles are coated onto the boron surface by adding titanium tetraisopropoxide (TTIP) precursors at room temperature. Characterization techniques were employed to investigate the structure and morphology of these materials. FTIR, XPS, and TEM analysis reveal that EG effectively removes ineffective boron hydroxyl surfaces and modifies the surface through passivation by its surface functionalities. Furthermore, EG assists in the coating very small-sized TiO2 particles on the boron surface. Thermal stability tests show that the modified boron surface and TiO2-coated boron surface exhibit earlier oxidation of the core boron compared to pristine boron. This enhanced capability for earlier oxidation of core boron was further investigated in the shock tube and bomb calorimeter for measurement of ignition delay time and heat of combustion. The findings demonstrate that room temperature synthesized TiO2-coated B particles (ignition delay time of ∼181 μs and heat of combustion of ∼17.3 kJ/g) outperform pristine B particles (ignition delay time of ∼284 μs and heat of combustion of ∼13.2 kJ/g). This improvement is attributed to the removal of ineffective boron hydroxyl surfaces, surface modification, uniform coating with very small TiO2 particles, the catalytic effect of TiO2 on oxygen diffusion, and effective oxidation of core boron. This study suggests that efficient energetic material can be achieved at room temperature with no potential harm to the environment.

Pre-Fermentative Cryogenic Treatments: The Effect on Aroma Compounds and Sensory Properties of Sauvignon Blanc and Chenin Blanc Wine—A Review

Low-temperature treatments preceding alcoholic fermentation are becoming increasingly popular and have been used in winemaking as a tool to improve wine colour, aroma, and quality. Additionally, the pre-fermentative treatment of grapes with cryogenic agents protects the grape juice (must) from oxidation by reducing the diffusion of atmospheric oxygen into the liquid phase during the winemaking process. Resultant wines were reported to have enhanced varietal aromas, increased complexity, and higher thiol levels. Indications are that increased contact time between skin and juice improves the extraction of the compounds and/or precursors. Recently, there has been considerable interest in the production of wines with enhanced varietal aromas and improved quality by applying innovative winemaking technologies. This review aims to provide an overview of the aroma and organoleptic quality of Sauvignon blanc and Chenin blanc wines produced from grapes that were subjected to pre-fermentative cryogenic treatments including the impact aroma compounds, i.e., volatile thiols and methoxypyrazines.

Fe-Doped Ceria-Based Ceramic Cathode for High-Efficiency CO2 Electrolysis in Solid Oxide Electrolysis Cell.

In the quest for sustainable energy solutions, solid oxide electrolysis cell (SOEC) emerges as a key technology for converting CO2 into fuels and valuable chemicals. This work focuses on pure ceramic FexSm0.2Ce0.8O2- δ (xFe-SDC) as the fuel electrodes, and Sr-free ceria-based ceramic electrodes can be successfully constructed for x ≤ 0.05. The incorporation of Fe into the ceria lattice increases the oxygen vacancy concentration and promotes the formation of catalytic sites crucial for the CO2 reduction reaction (CO2RR). Density functional theory calculations indicate that Fe enhances electrochemical performance by decreasing the CO2RR energy barrier and facilitating oxygen ion diffusion. At 800°C and 1.5V, single cells with 0.05Fe-SDC cathodes manifest attractive performance, attaining current densities of -1.98 and -2.26 A cm-2 under 50% CO2/CO and pure CO2 atmospheres, respectively. These results suggest the great potential of xFe-SDC electrodes as promising avenues for high-performance fuel electrodes in SOEC.

Boosting Bulk Oxygen Transport with Accessible Electrode Nanostructure in Low Pt Loading PEMFCs.

Despite the high potential for reducing carbon emissions and contributing to the future of energy utilization, polymer electrolyte membrane fuel cells (PEMFCs) face challenges such as high costs and sluggish oxygen transport in cathode catalyst layers (CCLs). In this study, the impact of pore size distribution on bulk oxygen transport behavior is exploredby introducing nano calcium carbonate of varying particle sizes for pore-forming. Physicochemical characterizationsfor are employed to examine the electrode structure, while in situ electrochemical measurements are used to scrutinize bulk oxygen transport resistance, effective oxygen diffusivity ( ) and fuel cell performance. Additionally, the CCLs are constructed with aid of Lattice Boltzmann method (LBM) simulations and for CCLs with different pore size distribution are calculated. The findings reveal that initially increases and then decreases as the most probable pore size increases. A "sphere-pipe" model is proposed to describe practical bulk oxygen transport in CCLs, highlighting the significant role of not only the pore size of secondary pores but also the number of primary pores in bulk oxygen transport.

Mathematical model of oxygen, nutrient, and drug transport in tuberculosis granulomas.

Physiological abnormalities in pulmonary granulomas-pathological hallmarks of tuberculosis (TB)-compromise the transport of oxygen, nutrients, and drugs. In prior studies, we demonstrated mathematically and experimentally that hypoxia and necrosis emerge in the granuloma microenvironment (GME) as a direct result of limited oxygen availability. Building on our initial model of avascular oxygen diffusion, here we explore additional aspects of oxygen transport, including the roles of granuloma vasculature, transcapillary transport, plasma dilution, and interstitial convection, followed by cellular metabolism. Approximate analytical solutions are provided for oxygen and glucose concentration, interstitial fluid velocity, interstitial fluid pressure, and the thickness of the convective zone. These predictions are in agreement with prior experimental results from rabbit TB granulomas and from rat carcinoma models, which share similar transport limitations. Additional drug delivery predictions for anti-TB-agents (rifampicin and clofazimine) strikingly match recent spatially-resolved experimental results from a mouse model of TB. Finally, an approach to improve molecular transport in granulomas by modulating interstitial hydraulic conductivity is tested in silico.

Mechanical properties and microstructure evolution of KD‐SA SiCf/BN/SiC CMCs oxidized at different temperatures

AbstractSilicon carbide fiber‐reinforced SiC ceramic matrix composites (SiCf/SiC CMCs) based on a domestic KD‐SA SiC fiber were exposed to a wet oxygen atmosphere for 135 h at 800, 1100, and 1300°C. The evolution of the microstructure and mechanical properties of SiCf/SiC CMCs have been systematically investigated following oxidation. For weight change, CMC‐1300 showed the greatest gain (0.394%), followed by CMC‐1100 (0.356%) and CMC‐800 (0.149%). The volatilization of boron oxide (B2O3) combined with the slight oxidation of the SiC matrix at 800°C caused crack deflection and fiber pull‐out. The complete dissipation of the interphase could be found when the oxidation temperature increases to 1100°C, generated a fracture surface with brittle fracture characteristics. At 1300°C, crystalline SiO2 hindered oxygen diffusion, with evidence of fiber pull‐out. Based on thermodynamic calculations and microscopic observations, we propose a mechanism to explain the thermal degradation of SiCf/SiC CMCs. This work offers valuable guidance for the fabrication of SiCf/SiC CMCs that are suitable for high‐temperature applications.

Machine Learning Design of Perovskite Catalytic Properties

AbstractDiscovering new materials that efficiently catalyze the oxygen reduction and evolution reactions is critical for facilitating the widespread adoption of solid oxide fuel cell and electrolyzer (SOFC/SOEC) technologies. Here, machine learning (ML) models are developed to predict perovskite catalytic properties critical for SOFC/SOEC applications, including oxygen surface exchange, oxygen diffusivity, and area specific resistance (ASR). The models are based on trivial‐to‐calculate elemental features and are more accurate and dramatically faster than the best models based on ab initio‐derived features, potentially eliminating the need for ab initio calculations in descriptor‐based screening. The model of ASR enables temperature‐dependent predictions, has well calibrated uncertainty estimates and online accessibility. Use of temporal cross‐validation reveals the model to be effective at discovering new promising materials prior to their initial discovery, demonstrating the model can make meaningful predictions. Using the SHapley Additive ExPlanations (SHAP) approach, detailed discussion of different approaches of model featurization is provided for ML property prediction. Finally, the model is used to screen more than 19 million perovskites to develop a list of promising cheap, earth‐abundant, stable, and high performing materials, and find some top materials contain mixtures of less‐explored elements (e.g., K, Bi, Y, Ni, Cu) worth exploring in more detail.

Effects of exposition to glycol ethers on heart rate recovery, parasympathetic modulation and oxygen diffusion at rest and during exercise

Introduction Daily exposition to ether glycols is common. Caretakers using cleaning products are critically exposed by combining physical activity with exposition to highly concentrated products. Previous animal studies showed hemato-, respiratory and autonomic nervous system toxicity amongst others. Yet, no controlled study explored the combination of an exposition to glycol ethers with physical activity in humans. Methods 30 young healthy participants were exposed a control condition (ambient air) and to one of three vaporized glycol ethers: propylene glycol n-propyl ether (PGPE, 25 ppm, n = 10) or propylene glycol ethyl ether (PGEE, 35 ppm, n = 10) or propylene glycol monomethyl ether (PGME, 35 ppm, n = 10) in a single-blind cross-over design. They performed an orthostatic test (5-min supine, 5-min standing) and a 6-min steady-state exercise at 1.5 W/kg followed by 10-min recovery in PGPE/PGEE conditions. In addition, an incremental exercise to exhaustion followed in PGME condition. Heart rate variability (HRV) was measured throughout the protocol, Heart rate recovery (HRR) was assessed during the 10-min recovery post steady-state exercise. Root-mean-square of the successive differences (RMSSD), power spectrum of the low- (LF) and high-frequency (HF) bands, tau, amplitude and T30 were computed for HRR. Near Infrared spectroscopy (NIRS) and cardiac output (using thoracic impedance) were measured for PGME exposition. PO2, PCO2 and pH were measured regularly via arterialized and venous blood sampling. Results Resting values of supine LF (1,180 ± 851 vs. 2,993 ± 2,259 ms2) and standing RMSSD (32 ± 17 vs. 41 ± 17 ms) increased under PGEE. Supine and standing HR decreased under PGPE (65.5 ± 4.8 vs. 61.3 ± 6.9 and 83.8 ± 7.0 vs. 76.1 ± 10.0 bpm) whereas standing RMSSD (26.6 ± 10.0 vs. 37.0 ± 14.9 ms) and LF (825 ± 474 vs. 2,028 ± 1,471 ms2) increased. Parasympathetic reactivation (e.g., RMSSD, LF and HF) was increased post-exercise under exposition to all three glycol ethers. In addition, amplitude significantly increased when exposed to PGEE. However, unexpectedly, HRR was neither slowed nor speeded. Finally, no differences were observed in any NIRS variables or cardiac output. Accordingly, the modelled muscle oxygen diffusion coefficient was not modified between any solvent conditions. Arterialized blood pH (7.35 ± .06 vs. 7.39 ± .04) and PaCO2 (34.1 ± 5.0 vs. 35.7 ± 4.3 mmHg) increased whilst PaO2 (81.8 ± 9.7 vs. 77.9 ± 10.6 mmHg) decreased. Discussion/Conclusion: The decrease in supine/standing HR associated with a general increase in HRV during recovery likely indicate an increase in parasympathetic modulation, which is compatible with the sedative effects of glycol ethers previously described in animal models. However, HR recovery was not altered. Despite no change in the O2 diffusion coefficient, there was an increase in PaCO2, a decrease in PaO2 and an increase in blood pH, all indicative of potential impaired blood oxygenation during exercise, to be further investigated. To conclude, exposition to different glycol ethers induced an enhanced parasympathetic activation without any changes in HR recovery or O2 diffusion.

Optimization for diffusion-type oxygen supply nearby working face of railway tunnel in plateau

During the construction of railway tunnels in plateau environment regions, ensuring adequate oxygen supply is crucial for both worker health and safety, and tunnelling progress. Existing diffusion-type oxygen supply enrichments for plateau regions lack quantitative conclusions and have not been implemented systematically in actual engineering. To refine the design parameters of the required method, this study utilized computational fluid dynamics (CFD) to examine the optimal design parameters for oxygen supply equipment in a typical engineering project. The optimal scheme consisted of three rows of oxygen diffusion apparatuses with 0.07 m inlet diameter, 0.4 m lateral spacing and 60° tilt that maintain a constant oxygen supply rate. This configuration maximized oxygen concentration enrichment in workers’ breathing zones, with oxygen partial pressure in most target zones remaining below 3000 m altitude, except for the ventilation side where it was 3360 m. This study elucidated the effects of various design parameters on oxygen distribution and proposed the optimal combination for a typical tunnel engineering project. The findings provide a guidance for implementing diffusion-type oxygen enrichment in high-altitude tunnel construction, aiding both worker safety and project efficiency.

In situ observation of a macrourid fish at 7259 m in the Japan Trench: swimbladder buoyancy at extreme depth.

A macrourid, Coryphaenoides yaquinae sp. inc., was observed to be attracted to bait and exhibiting normal foraging behaviour during a period of 80 min within view of a baited video camera on the sea floor at 7259 m - the deepest ever observation of a fish species with a swim bladder. The buoyancy provided by an oxygen-filled swim bladder at 74.4 MPa pressure was estimated to be 0.164N, at a theoretical energy cost of 20 kJ, 200 times less than the cost of equivalent lipid buoyancy. During normal metabolism, 192 days would be required to fill the swimbladder. At these depths, oxygen is very incompressible, so changes in volume during ascent or descent are small. However, swimbladder function is crucially dependent on a very low rate of diffusion of oxygen across the swimbladder wall. The oxygen in the swimbladder could theoretically sustain aerobic metabolism for over 1year but is unlikely to be used as a reserve.

Oscillatory dynamics of discrete reaction-zones for hydrogen–oxygen diffusion flames within a narrow channel

A diffusion flame in the fuel-oxidizer mixing layer within a narrow channel can be split into several stationary, discrete flame segments at some particular conditions. This unique flame structure has deeply been analyzed in previous literature. In this paper, by performing numerical simulations using a transient, low-Mach number, reacting flow solver in OpenFOAM, unsteady dynamics of separated reaction zones for low Lewis number, hydrogen–oxygen diffusion flames in a 30 × 5 × 0.75 mm3 microchannel are newly discovered. For a variety of inflow rates (H2/O2 flow rate of 300/150, 200/100, and 100/50 sccm) and wall temperatures (Tw = 900, 800, 700, 600, and 500 K) investigated, stable and continuous flame sheets can only be witnessed at large Reynolds numbers or high wall temperatures. Flames at other conditions are found in a discrete form, presenting an unstable and repetitive feature. Specifically, in the wake of the leading, anchored diffusion flame, edge flames with tribrachial structures are consecutively established and then propagate downstream, while eventually end by moving out of the channel, or being extinguished halfway, or behaving in a mixed mode (the two events occur alternately for two successively generated edge flames). Effects of Lewis numbers on flame behaviors are also studied via helium addition to both the fuel and oxidizer stream. Isolated reaction zones at a steady state can be witnessed for a relatively large Lewis number under a high level of addition.

Extended defects-enhanced oxygen diffusion in ThO[formula omitted]

Oxygen self-diffusion is key to understanding stoichiometry and defect structures in oxide nuclear fuels. Experimentally, low activation-barrier oxygen migration was found in ThO2, a candidate nuclear fuel, possibly due to short-circuit diffusion mechanisms. Here, we perform extensive molecular dynamics simulations to show that various types of extended defects can enhance oxygen self-diffusion with a much-reduced activation barrier in ThO2. In this work, we consider extended defects including 1D (dislocation), 2D (grain boundary), and 3D (void) defects. Due to the distinct characteristics of each type of extended defect, the modulation of oxygen diffusion varies. These results provide a quantitative description of oxygen transport, which is significantly enhanced within a close distance (nanometer scale) from the extended defects. Among all these considered defects, grain boundary, particularly the low-energy Σ3 twin boundary, exhibits the strongest effect on increasing oxygen transport.

Thermal and Mechanical Investigations of (Bi, Pb)-2212 Superconductor Added with Different Oxide Nanoparticles

Abstract The current study reports the synthesis of nano-(CdO)x/Bi1.6Pb0.4Sr1.9Ca1.1Cu2.1Oy, nano-(Cd0.95Mn0.05O)x/Bi1.6Pb0.4Sr1.9Ca1.1Cu2.1Oy, and nano-(Cd0.95Fe0.05O)x/Bi1.6Pb0.4Sr1.9Ca1.1Cu2.1Oy composites, with x = 0.00, 0.01, 0.02, 0.05, and 0.10 wt. %, respectively, using the classical solid-state reaction technique. X-ray powder diffraction (XRD) confirmed the formation of an orthorhombic structure of the (Bi, Pb)-2212 as the major phase. Thermogravimetric analysis was utilized to evaluate the thermal stability of the pure sample throughout the different stages of phase formation and the effect of nanoparticle addition. The weight loss/gain from the three additions is related to the excess of oxygen, as confirmed via iodometric titration analysis and from the findings of oxygen diffusion energy. Room temperature Vickers microhardness (HV) measurements were conducted at various applied loads (0.49–9.8 N). Based on the Vickers microhardness (HV) measurements, the optimum addition of nanoparticles for increasing the microhardness of the (Bi, Pb)-2212 phase was at x = 0.05 wt. % for all superconducting composites. Iron doped Cadmium Oxide (CdFeO) nanoparticles have the greatest enhancement on the Vicker hardness values (HV) at the plateau region. Furthermore, various mechanical parameters for potential applications, such as elastic modulus (E), yield strength (Y), and fracture toughness (K) of the samples under study, were consequently extracted from HV as a function of nanoparticle addition. Moreover, CdFeO addition outperformed CdO and Manganese doped Cadmium Oxide (CdMnO) addition in improving the parameters of E, Y, K, and B, which display better ductility and an enhanced capacity to resist indentation fractures and facilitate (Bi-2212) manufactured in the form of round wires that can be used in high magnetic field magnets, nuclear magnetic resonance instruments, and large hadron colliders. Different models were theoretically used to analyze the measured HV data in the plateau limit regions. The indentation-induced cracking model offered the most accurate theoretical model at the plateau limit region based on Vickers microhardness (HV) observations.

Oxygen diffusion into unsaturated seawater and sea sand concrete and its effect on non-uniform corrosion of steel bars

Oxygen diffusion in reinforced concrete (RC) is a crucial factor affecting the corrosion of steel bars under a high chloride environment, while it is also controlled strongly with the saturation degree of the concrete. Therefore, the objective of this work is to elucidate the diffusion of oxygen in unsaturated concrete and its effect on the corrosion of steel bars. In this work, a self-made device is developed to study the oxygen diffusion in seawater and sea sand concrete (SSC) and the wire beam electrode (WBE) technique is innovatively used to investigate the effect of oxygen on the corrosion of steel bars. The oxygen diffusion coefficient of SSC was decreased maximum by 97.3 % with the internal relative humidity (RH) of concrete increasing from 12 % to 88 %, it was increased by 96.5 % when the water-binder ratio increased from 0.18 to 0.48. A multi-factor coupling model considering the relative humidity and strength of concrete was developed to estimate the oxygen diffusion coefficient of concrete. The corrosion process of steel bars was tracked by the WBE technique and it presented as the formation and propagation of the local anode zone. However, the electrodes were still in a passivation state after corrosion for 120 d when the water-binder ratio was lower than 0.28 or the oxygen concentration was lower than 21 % even in SSC. Therefore, the pitting anode zone will be shrunk and the corroded steel bars were re-passivated with insufficient oxygen supply during the late service process.

Corrosion mechanism and performance of Cr-coated Zr-4 alloy in 360 °C water and 1300 °C steam

A dense and uniform Cr coating is prepared on the Zr-4 alloy using multi-arc ion plating technology, with the aim of serving as an accident-tolerant fuel cladding for light water reactors. The corrosion performance of Cr-coated Zr-4 alloy is investigated after exposure to 360 °C and 18.6 MPa corrosion conditions for up to 5040 h, and its corrosion mechanism is discussed. Furthermore, the oxidation behavior of the Cr-coated Zr-4 alloy in steam at 1300 °C is mainly examined. It is observed that the ZrO2 channel within the Cr coating acts as an oxygen diffusion path during steam oxidation and facilitates the reduction of Cr2O3 by providing Zr. When the ZrO2 channel diffuses to the Cr2O3/Cr interface, Cr2O3 is reduced to form ZrO2 and Cr. When the thickness of the Cr2O3 layer is minimized, the Cr coating fails. The in-situ oxidation of the Cr2Zr layer results in the formation of ZrO2 and Cr2O3, while the substrate beneath the Cr coating is oxidized to form a ZrO2 layer. The whole oxidation process of the Cr-coated Zr-4 alloy up to 1300 °C is presented in detail.

Investigation on failure mechanism and interfacial diffusion behavior of NiCoCrAlYTa coating at high temperature

The isothermal oxidation behavior of NiCoCrAlYTa coating deposited by arc ion plating (AIP) technology on DZ22B substrate was systematically investigated at 1050 ℃ and 1100 ℃ for 200 h. The results revealed a transition in oxide scale composition, which of undulation degree was also increased. The growth process of oxide scale involved additional control mechanisms except internal diffusion of oxygen. Interdiffusion at coating/substrate interface transformed γ into γ' phase in substrate, precipitating MC carbides. MC carbide underwent progressive disintegration, transforming into M6C carbide. The results could provide experimental data and theoretical support for the design of long-life protective coatings at ultra-high temperatures.

Molecular dynamics simulation and experimental verification of influence of crosslinking reaction process parameters on oxygen permeability of PDMS membranes

Sufficient oxygen permeability of the substrate is the key to ensuring the reliability of the Continuous Liquid Interface Production process. Polydimethylsiloxane (PDMS), as a cost-effective material with good gas permeability, holds potential for applications as oxygen-permeable windows in constrained substrates. Therefore, it is of great significance to investigate how to enhance the oxygen permeability of PDMS. In this study, the program code for the crosslinking reaction between the prepolymer and curing agent was developed. Molecular dynamics simulations were employed to investigate the effects of the process parameters on the diffusion coefficient of oxygen. Validation experiments were conducted by measuring the oxygen permeability of the substrate. The research findings reveal that process parameters, including crosslinking time, crosslinking temperature, and the mass ratio of prepolymers to curing agents, influence the diffusion coefficient of oxygen in PDMS membranes. Increasing the crosslinking time leads to an increase in the number of crosslinking points, hindering polymer chain mobility and limiting the increase in free volume, thereby decreasing the oxygen diffusion coefficient. An optimal crosslinking temperature of 348 K enhances the probability of jump channel formation between cavities, resulting in the maximum oxygen diffusion coefficient. The oxygen diffusion coefficient of PDMS membranes increases with rising mass ratio.