Gas Mixture Research Articles

Effect of interval hypoxytherapy on the immune status of hypertensive patients

In recent years, the role of sluggish nonspecific inflammation in the pathogenesis of hypertension has been proven. Oxidative stress that develops in hypertension leads to damage of endothelial glycocalyx with impaired barrier and adaptive functions of endothelium. Activation of transcription factor NF-kB leads to increased synthesis of free oxygen radicals, adhesion molecules (VCAM-1, ICAM-1, P-selectin, E-selectin) and proinflammatory cytokines (TNFα, IL-1, IL-6), triggering the inflammatory process in the endothelium. Modern antihypertensive drugs, affecting various pathogenetic mechanisms of arterial hypertension development, do not fully affect the immune component of arterial hypertension. Therefore, the search for various methods affecting the immunologic reactivity of hypertensive patients remains relevant in our time. The aim of the study was to reveal the effect of interval hypoxytherapy on the state of immunologic reactivity of patients with hypertension stage I. One hundred seventy male patients of 30-45 years old (mean age 38.36±1.64 years) with hypertension stage I (n = 170) who underwent combined treatment including drug therapy and normobaric interval hypoxic therapy in hypoxia-normoxia mode (oxygen content in hypoxic gas mixture was 20.9%) were examined. Indices of redox status and immunologic reactivity before and after interval hypoxytherapy were studied. Having a significant antioxidant effect, interval hypoxytherapy led to the subsidence of oxidative stress, which was indicated by an increase in the activity of superoxide dismutase and glutathione peroxidase in blood erythrocytes and a decrease in the content of malonic dialdehyde in blood as a result of a decrease in the generation of free oxygen radicals and suppression of lipid peroxidation processes. Interval hypoxytherapy resulted in a statistically significant increase in the initially decreased content of CD3+T lymphocytes (p 0.05), CD3+CD4+T lymphocytes (p 0.02), CD3+CD8+T lymphocytes (p 0.02). Initially increased number of B-lymphocytes CD19+, CD16+ lymphocytes, CD95+ lymphocytes significantly decreased. An important result of interval hypoxytherapy was a pronounced anti-inflammatory effect: statistically significant decrease in the content of pro-inflammatory interleukins IL-1β (p 0.02), IL-6 (p 0.01) and increase in the content of anti-inflammatory cytokines IL-4 (p 0.005) and IL-10 (p 0.005), which led to the subsidence of sluggish nonspecific inflammation. Suppression of oxidative stress and normalization of immunological reactivity of hypertensive patients after interval hypoxytherapy led to the subsidence of sluggish nonspecific inflammation, reduction of endothelial dysfunction and restoration of the structure and tone of the vascular wall with a decrease in blood pressure and improvement of the clinical course of hypertension.

Development of Photonic In-Sensor Computing Based on a Mid-Infrared Silicon Waveguide Platform.

Neuromorphic in-sensor computing has provided an energy-efficient solution to smart sensor design and on-chip data processing. In recent years, various free-space-configured optoelectronic chips have been demonstrated for on-chip neuromorphic vision processing. However, on-chip waveguide-based in-sensor computing with different data modalities is still lacking. Here, by integrating a responsivity-tunable graphene photodetector onto the silicon waveguide, an on-chip waveguide-based in-sensor processing unit is realized in the mid-infrared wavelength range. The weighting operation is achieved by dynamically tuning the bias of the photodetector, which could reach 4 bit weighting precision. Three different neural network tasks are performed to demonstrate the capabilities of our device. First, image preprocessing is performed for handwritten digits and fashion product classification as a general task. Next, resistive-type glove sensor signals are reversed and applied to the photodetector as an input for gesture recognition. Finally, spectroscopic data processing for binary gas mixture classification is demonstrated by utilizing the broadband performance of the device from 3.65 to 3.8 μm. By extending the wavelength from near-infrared to mid-infrared, our work shows the capability of a waveguide-integrated tunable graphene photodetector as a viable weighting solution for photonic in-sensor computing. Furthermore, such a solution could be used for large-scale neuromorphic in-sensor computing in photonic integrated circuits at the edge.

Crab shell-based hierarchical micro/meso-porous carbon as an efficient nano-adsorbent for CO2/CH4 separation: experiments and DFT modeling

In this study, we prepared a range of nanoporous carbon nano-adsorbents from crab shells (CSs) using KOH activation and evaluated their suitability for selective adsorption of CO2/CH4 gas mixtures. We employed various characterization techniques, including XRD, FT-IR, SEM, Raman, TGA, and BET analysis, to assess the properties of these nano-adsorbents. Our investigation includes the systematic study of various parameters, such as activation time, activation temperature, and the KOH to CS activating agent ratio. The nanoporous carbons were evaluated for their CO2 adsorption capabilities at 1–10 bar and 25 ℃ condition. The results demonstrated that the CS-2-2-900 sample, activated for 1 h at 900 ℃ with a 2:1 ratio of KOH to CS, exhibited the highest gas adsorption capacity, reaching 7.217 mmol/g at a pressure of 10 bar under room temperature conditions. Additionally, the synthesized CS-2-2-900 sample displayed excellent surface area (914.85 m2/g), a pore volume of 1.1 cm3/g, and an average pore diameter of 4.82 nm. Furthermore, we functionalized the CSs to enhance their selectivity for ammonia adsorption. Using the Myers and Pravnitz theory, we calculated that the FCS-2-2-900 sample exhibited the highest selectivity, reaching 18.99 at 25 ℃ under pressures of up to 10 bar. To gain a more comprehensive understanding of the interactions between the adsorbents and the adsorbed molecules, as well as to identify the active sites involved in the adsorption process, we employed density functional theory (DFT). Our DFT calculations revealed that pyrrolic nitrogen and carboxylic sites played a significant role in enhancing the separation of CO2 in binary mixtures. In summary, nanoporous carbons derived from crab shells outperformed those derived from other waste materials. These functionalized porous nanocarbons represent promising adsorbents for the selective adsorption of CO2 gas in CO2/CH4 mixtures due to their nitrogen content, high porosity, stability, and economic efficiency.

Etch Characteristics of Cobalt Thin Films in High Density Plasma of Cl2/O2/Ar Gas Mixture

Inductively coupled plasma reaction ion etching (ICP-RIE) of cobalt thin films patterned with SiO2 hard masks was performed using Cl2/O2/Ar gas mixture. The etch characteristics of cobalt films in Cl2/Ar gas were examined to determine the roles of Cl2 and O2, respectively. The etch rates and etch profiles of cobalt films were investigated by varying the O2 concentration in Cl2/O2/Ar gas mixture.In the optimized Cl2/Ar gas mixture, systematic etching of cobalt films was performed by changing the etch parameters including ICP RF power, DC-bias voltage, and process pressure. As the DC-bias voltage and process pressure was increased, the etch rate increased and the etch profile improved. Through the etching parameters variation experiment, the etching properties were investigated by adding O2 to Cl2/Ar under optimized conditions. X-ray photoelectron spectroscopy and optical emission spectroscopy were used to investigate the etch mechanism in the Cl2/O2/Ar gas mixture. In addition, scanning probe microscope was used to observe roughness on the etched cobalt surface. Finally, the etching of cobalt films patterned with nanometer-scale in the optimized Cl2/O2/Ar gas mixture was successfully achieved with good etch profile.AcknowledgmentThis research was supported by the Ministry of Trade, Industry & Energy (MOTIE) (20019504) and Korea Semiconductor Research Consortium (KSRC) support program for the development of future semiconductor devices. This work was supported by Korea Institute for Advancement of Technology (KIAT) grant funded by the Korea Government (MOTIE) (P0008458, HRD Program for Industrial Innovation).

Electrical and Optical Characterization of Atmospheric Pressure Plasmas for the Treatment of OPV Materials

In the last years, non-equilibrium cold plasma at atmospheric pressure have led to numerous opportunities for material treatment. Depending on the gas mixtures, the electrodes configurations, the electrical waveform used to generate the discharge, or the material, a wide range of surface properties can be created. Among the plethora of applications, the organic photovoltaic (OPV) community has recently explored the use of plasma [1]. Thanks to the versatility of the cold atmospheric pressure plasmas (CAPP), all the layers used in the OPV cells could be potentially treated and modified. The use of dry atmospheric pressure processes also opens the doors to fast treatments at reduced cost compared to low pressure [2].Possible CAPP configurations for the OPV include plasma jets and dielectric barrier discharges (DBD) in volume or surface [3]. Among the different use of plasma in OPV, surface cleaning has been largely studied. For example, the removal of organic contaminants from indium tin oxide (ITO) layer have successfully been achieved with all the aforementioned configurations as well as different gas mixtures such as N2, O2, or He [4–6]. Other interesting mechanisms, such as the passivation of the electron transport layer [7], the modification of the work function [8], or for the encapsulation of the whole OPV cells [9] have been also explored.Still, whatever the material, either the metallic electrodes, the semiconductive active layer, or the dielectric substrates, a fine control of the plasma properties is necessary to ensure the good reproducibility and the stability of the process. It is hence necessary to characterize the physical regime and clarify the chemical reactions suitable to assess the good operation of the process during the material treatment.This work focuses on the use of electrical measurements and optical emission spectroscopy (OES) to retrieve key parameters from the process, like the discharge regime (Townsend vs filamentary), the capacitances of the system, or the power dissipated during the treatment [10]. In this context, this work aims at characterizing different discharge regimes for the surface treatment of thin characteristic layers employed in OPV (i.e., ITO, fluorine doped tin oxide (FTO) and zinc oxide). The influence of different electrical signals (low frequency sinusoidal voltage vs nanopulse), as well as different configurations and dielectric materials are compared. In order to link and allow to use such measurement as monitoring tools for the treatment process of materials used in OPV cells, the treated surfaces are also analyzed by SEM and contact angle. The extracted quantities from the plasma diagnostics could hence be used as a predictive tool to forecast the final properties of the treated materials and improve the processes of material treatment in OPV.[1] Mariotti et al. https://doi.org/10.1002/ppap.201500187[2] Vida et al. https://doi.org/10.37904/nanocon.2019.8646[3] Homola et al. https://doi.org/10.1016/B978-0-323-89930-7.00001-7[4] Chiang et al. https://doi.org/10.1007/s11090-010-9237-4[5] Yi et al. https://doi.org/10.1016/j.surfcoat.2003.08.011[6] Hvojnik et al. https://doi.org/10.1016/j.mssp.2021.105850[7] Polydorou et al. https://doi.org/10.1039/C6TA03594A[8] Chaney et al. https://doi.org/10.1016/S0169-4332(01)00347-6[9] Juillard et al. https://doi.org/10.1002/admi.202000293[10] Pipa et al. https://doi.org/10.3390/atoms7010014

Selective Isotropic Dry Etching of SiO2 Using F/H-Based Pulsed Remote Plasma and a Vapor Phase Solvent

Isotropic etching generally employs liquid-based wet etching techniques. However, due to the high integration of devices, conformal etching is challenging in patterns with a high aspect ratio because liquid chemicals struggle to penetrate inside the pattern. Additionally, during the drying process after chemical treatment, pattern collapse is observed due to surface tension. Therefore, there is a need for dry isotropic etching techniques to replace wet etching techniques in next-generation device manufacturing processes.Typically, when high selectivity SiO2 isotropic dry etching is required, F-base/H-based gas mixtures are utilized to form HF, which serves as an etchant for SiO2. SiO2 can be dry etched through two different mechanisms. First, HF reacts directly with H2O or alcohol, etching SiO2. The other way is to produce (NH4)2SiF6 salt from the reaction of NH3, which can be formed in a plasma containing NH3 and NF3. This (NH4)2SiF6 salt is sublimated and removed by a following heating process at a temperature over 100ºC.The process above has some disadvantages, such as lowering the etch selectivity of SiO2 over Si and Si3N4 because Si and Si3N4 can be etched by F radicals remaining in the plasma. This study aimed to overcome these disadvantages by controlling the F radical through pulsing the remote plasma during the discharging of F-based/H-based gas mixtures for the formation of HF. By pulsing the remote plasma, SiO2 could be selectively etched at a higher etch rate relative to those of Si and Si3N4. Additionally, various types of H/F-based gas mixtures that do not contain nitrogen while producing HF were investigated to prevent the formation of ammonium powders, which can be a source of contamination in the chamber. Futhermore, the etching mechanisms were identified through gas phase anlysis and surface analysis. Also, any possible surface damage during the etching process was investigated.

Investigating the Impact of Air Pollutants on Fuel Cell Performance and Durability: Experimental and Modeling Approaches

Fuel cells hold immense promise as efficient and sustainable power sources for transportation and stationary applications. However, their operation can be severely impacted by air pollutants, particularly sulfur dioxide (SO2) and nitrogen oxides (NOx). These pollutants can adsorb onto the platinum catalyst, leading to a decrease in fuel cell performance and durability.In this study, we investigate the impact of SO2 and NO2 on PEM fuel cell performance and durability. The contamination tests were carried out at a constant current density of 0.5 A.cm−2, and they consisted of four steps: a pre-poisoning step to evaluate initial performance (15-16 h), poisoning step (50 h), self-recovery in a pure air stream (20-21 h) and a driven CV-induced recovery. Electrochemical characterizations were carried out at the end of each step (Polarization curve, Electrochemical Impedance Spectroscopy, Cyclic Voltammetry and H2 Crossover). Our initial investigation involved contaminating a single fuel cell with a low concentration of 0.1 ppm of sulfur dioxide (SO2). Remarkably, this resulted in a 1.1% decrease in cell voltage. Building on this foundation, our ongoing research aims to delve deeper into the impact of individual pollutant concentrations (SO2 and NO2) and their combined effects, considering varying temperatures and current densities to simulate real-world conditions.Simultaneously, a comprehensive model is being developed using Simscape in Matlab. The model accounts for the pollutants either as single-component gases or as a mixture. For single-component gas adsorption, the Langmuir Isotherm model is employed. To capture the competitive adsorption of SO2 and NO2 on platinum in gas mixtures, we are testing the Modified Competitive Langmuir Isotherm Model. The model will further be calibrated and validated using the experimental results.This combined experimental and modeling approach will provide a comprehensive understanding of the impact of air pollutants on fuel cell performance and durability. The insights gained from this study can inform the development of mitigation strategies and enhance the robustness of fuel cells in real-world applications as well as the sizing of a filter. Figure 1

Amino-Functionalized Metal-Organic Frameworks Featuring Ultra-Strong Ethane Nano-Traps for Efficient C2H6/C2H4 Separation.

Developing high-performance porous materials to separate ethane from ethylene is an important but challenging task in the chemical industry, given their similar sizes and physicochemical properties. Herein, a new type of ultra-strong C2H6 nano-trap, CuIn(3-ain)4 is presented, which utilizes multiple guest-host interactions to efficiently capture C2H6 molecules and separate mixtures of C2H6 and C2H4. The ultra-strong C2H6 nano-trap exhibits the high C2H6 (2.38mmolg-1) uptake at 6.25kPa and 298K and demonstrates a remarkable selectivity of 3.42 for C2H6/C2H4 (10:90). Additionally, equimolar C2H6/C2H4 exhibited a superior high separation potential ∆Q (2286mmolL-1) at 298K. Kinetic adsorption tests demonstrated that CuIn(3-ain)4 has a high adsorption rate for C2H6, establishing it as a new benchmark material for the capture of C2H6 and the separation of C2H6/C2H4. Notably, this exceptional performance is maintained even at a higher temperature of 333K, a phenomenon not observed before. Theoretical simulations and single-crystal X-ray diffraction provide critical insights into how selective adsorption properties can be tuned by manipulating pore dimensions and geometry. The excellent separation performance of CuIn(3-ain)4 has been confirmed through breakthrough experiments for C2H6/C2H4 gas mixtures.

Utilization of coal for hydrogen generation

ABSTRACT The utilization of coal for hydrogen generation presents a multifaceted approach employing processes like coal gasification, pyrolysis, or high-temperature steam reforming. These methodologies entail reacting coal with steam or oxygen under elevated temperatures, yielding a gas mixture comprising hydrogen, carbon monoxide, and various byproducts. This paper delves into the exploration of hydrogen generation from coal, highlighting techniques such as gasification, pyrolysis, and other emerging methods. Notably, hydrogen discoveries within coal basins have garnered significant attention due to their implications for energy production and environmental sustainability. Certain coal basins harbor deposits rich in hydrogen, surpassing conventional coal reserves in their hydrogen content. These hydrogen-rich coals, including select sub-bituminous and lignite varieties, offer promising avenues for hydrogen production and utilization. However, the utilization of coal for hydrogen generation is not without its challenges. Technical hurdles, such as process efficiency and environmental concerns, demand rigorous investigation and innovative solutions. This paper addresses the challenges faced in coal-based hydrogen generation while elucidating the potential future prospects. It explores avenues for enhancing process efficiency, mitigating environmental impacts, and integrating coal-based hydrogen generation into broader energy strategies. Moreover, it underscores the importance of interdisciplinary research and collaboration in unlocking the full potential of coal for sustainable hydrogen production.

Kinetic Gas Hydrate Inhibition by Alternating Dipeptoids with Optimal Size and Shape N-Substituents.

Current commercial kinetic hydrate inhibitors (KHIs) are all based on water-soluble polymers with amphiphilic alkylamide or lactam groups. The size and shape of the hydrophobic moiety are known to be critical for optimum KHI performance. Proteins and peptides represent an environmentally friendly alternative, especially as bioengineering could be used to manufacture a product predetermined to have optimum KHI performance. Here, we explore a new series of polymers that are alternating dipeptoids where one of the peptide links originates from glycine. The dipeptoids contain n-propyl groups on the nitrogen atom and varying size and shape alkyl side chains on the neighboring carbon atom. Experiments were carried out in high-pressure steel rocking cells using the slow constant cooling (SCC) test method (1 °C/h) and a synthetic natural gas mixture. All the dipeptoids showed good KHI performance with the best result being for that with a glycine-N-propylleucine repeating unit (Poly iC4-Pr), which has pendant iso-butyl groups on the carbon atom. It exhibited the same KHI performance as poly(N-vinyl caprolactam). Dipeptoids with smaller or longer alkyl groups than iso-butyl gave worse performance. It is conjectured that the iso-butyl group is the optimal carbon length for this polymer class. In addition, the end-branching maximizes the van der Waals interaction with open cavities on growing hydrate particles, which must occur without loss of hydrogen-bonding from the neighboring peptide linkage for optimum KHI performance. Thus, the study provides further evidence for the premise that good KHI molecules must contain multiple amphiphilic groups (often as polymers) with optimal size and shape hydrophobic groups adjacent to strong hydrogen bonding groups. The solvent, n-butyl glycol ether, was shown to be a synergist for Poly iC4-Pr, lowering the onset temperature of hydrate formation in SSC tests relative to the polymer alone.

Effect of Thickness and Sidewall Slope of Photoresist Mask on Etch Profile of Copper Interconnect

We performed high density plasma reactive ion etching of copper thin films using organic gas mixture to define fine patterns less than 10 μm for the application of display devices. However, since redeposition in dry etching of copper thin films frequently occurs due to extremely low reactivity, the etch variables which affect the formation of redeposition were investigated. In this study, the photoresist (PR) masks were employed to etch copper thin films. The effects of the thickness of PR and the sidewall slope of PR on etch profile and redeposition were examined.The thickness of PR mask were in the range of 3 μm ~ 1 μm and the sidewall slopes of the PR mask were in the range of 90° ~ 45°. The etch profile and etch mechanism of dry etching using different masks were evaluated using field emission scanning electron microscopy and X-ray photoelectron spectroscopy. Finally, an etching method to reduce and/or avoid the redeposition in dry etching of copper thin films will be proposed.Acknowledgement : This research was supported by the MOTIE(Ministry of Trade, Industry & Energy (20019504) and KSRC(Korea Semiconductor Research Consortium) support program for the development of the future semiconductor device.

Effect of Membrane Thickness and Operating Conditions on PEMFC Limiting Current Analysis

Hydrogen powered proton exchange membrane fuel cells (PEMFC) have great potentials to replace the traditional internal combustion engines due to its inherent advantages of zero greenhouse gas emissions, better fuel efficiency, quick startup, silent operation, less required maintenance, etc. In a PEMFC, oxygen transport is a critical performance limiting factor because of the sluggish oxygen reduction reaction kinetics. Limiting current method is a well-established in-situ diagnostic tool to measure the oxygen transport resistance in a PEMFC. To obtain accurate oxygen transport resistances, a few key assumptions need to be made including: (1) the effect of temperature gradient in the diffusion media is negligible, (2) no convective flow in the porous media, (3) oxygen is diluted in a gas mixture of nitrogen and water vapor, (4) the total oxygen transport resistance combines gas diffusion layer, microporous layer, and catalyst layer, (5) the effect of membrane thickness has negligible effect, and (6) the anode side does not affect the measurement results due to fast hydrogen oxidation reaction. In this study, we perform a systematic study of the effect of membrane thickness and operating conditions on obtaining robust and reliable limiting current measurement. Standard Nafion membranes of three different thicknesses (25, 50, and 85 µm) are tested with Toray 060 and Freudenberg H23C8 diffusion media. In addition, we further study the interaction between membrane thickness and asymmetric pressure and relative humidity and their effects on limiting current results. Our results show that membrane thickness and relative humidity are critical factors in obtaining reliable oxygen transport resistance due to their effect on overall water balance in the cell. Lastly, the experimental data are compared with the simulation results to establish fundamental understanding. Detailed experimental and analytical results will be presented at the conference.

(Invited) Multi-Modal Solid-State Gas Sensors-Based Breath Analysis System with Convolutional Neural Network (CNN) for Early Detection of Lung Cancer

Currently, digital healthcare technologies based on Internet of Things (IOT) are emerging, and the market for digital healthcare was estimated to be 151.5 billion dollars by 2020. Among the digital healthcare technologies, disease diagnosis is attracting maximum attention. Traditional diagnostic methods, such as radiology and human biological material analysis, have limitations of long study time, high cost, radiation exposure, and pain. Therefore, non-invasive diagnostics methods, for early diagnosis of specific diseases and personal healthcare management, have attracted attention.Breath sensors are one of the promising candidates for the realization of non-invasive diagnosis owing to their ease of use, safety, and cost effectiveness. The exhaled breath analysis technique holds great promise as a non-invasive method for diagnosing lung cancer. In the breath of lung cancer patients, various volatile organic compounds (VOCs) markers are generated during metabolic processes. Analyzing these VOCs markers presents a compelling avenue for early and non-invasive lung cancer diagnosis. Solid state gas sensors capable of measuring specific VOCs are currently being researched and utilized as commercial gas sensors for this purpose. However, the concentration of lung cancer VOCs markers in exhaled breath is commonly very low, and individual commercial gas sensors often lack the necessary sensitivity and selectivity to accurately diagnose lung cancer. In this study, we propose a multimodal solid state electronic biosensor system designed to differentiate lung cancer VOCs characteristics among multiple VOCs, enabling exhalation-based lung cancer diagnosis. Initially, we developed multimodal biosensors using more than 20 gas sensors, consisting of metal oxide semiconductor sensors, electrochemical sensors, photoionized detectors, metalorganic frame sensors and so on. And each exhibiting varying sensitivity profiles for complex gas mixtures. Additionally, we designed a classification algorithm based on convolutional neural networks (CNN) and multi-layered perceptron (MLP) to distinguish between lung cancer patients and healthy individuals using the output from these diverse multimodal gas sensors. To evaluate the system's performance, we collected exhaled air samples from 74 lung cancer patients and 107 normal subjects, conducting clinical trials with our developed system. We did model evaluation with confusion matrix and ROC curve. The results of these tests confirmed that our system achieved a high predictive accuracy of over 95% in classifying lung cancer patients. The simplicity of the sensor configuration in our developed system makes it suitable for large-scale screening tests to identify potential candidates for precise lung cancer diagnosis. This technology has the potential to contribute to reduced national welfare costs and improved patient survival rates through early diagnosis.

Effectiveness of Gas Recombination Catalyst Layers in Mitigating H2 Crossover in PEM Water Electrolyzers Operating at High Differential Pressure

Gigawatt-scale deployment of proton exchange membrane water electrolyzers (PEMWE) to produce green hydrogen at $1/kg of H2, the US department of energy’s (DOE) ultimate cost target, requires the use of thinner membranes to reduce ohmic losses at high current densities as well as differential pressure operation to improve the overall system efficiency.1 High differential pressure operation results in significant hydrogen crossover through PEMs leading to safety concerns due to the formation of a flammable gas mixtures at anode (> 4% H2 in O2).2 Therefore, the successful deployment of PEMWEs at scale relies on successful implementation strategies to reduce the hydrogen concentration at anode to enable safe operation at high efficiency. These strategies include incorporating gas recombination catalyst (GRC) in the membrane, PTL or downstream in the anode gas outlet. However, the impact of GRC layers on PEMWE performance and hydrogen crossover rates at high differential pressure is not well understood.In this work, we employ in-operando gas chromatography coupled with thermal conductivity detector along with PEMWEs operating at differential pressures (up to 30 bar) to quantify hydrogen crossover rates through PEM at differential pressure. Using this setup, we evaluate the effectiveness of gas recombination layers incorporated in PEMWE membrane electrode assemblies (MEA) in mitigating the risk of formation of the flammable gas mixture. Further, we will also discuss implications of high differential pressure operation on PEMWE performance, durability, and operational safety.

Engineering Insights into Tailored Metal-Organic Frameworks for CO2 Capture in Industrial Processes.

Despite the known impacts on climate change of carbon dioxide emissions, the continued use of fossil fuels for energy generation leading to the emission of carbon dioxide (CO2) into the atmosphere is evident. Therefore, innovation to address and reduce CO2 emissions from industrial operations remains an urgent and crucial priority. A viable strategy in the area is postcombustion capture mainly through absorption by aqueous alkanolamines, which focuses on the separation of CO2 from flue gas, despite its limitations. Within this context, porous materials, particularly metal-organic frameworks (MOFs), have arisen as favorable alternatives owing to their significant adsorption capacity, selectivity, and reduced regeneration energy demands. This research evaluates the engineering insights into tailored MOFs for enhanced CO2 capture, focusing on three series of MOFs (ZIF, UiO-66, and BTC) to investigate the effects of organic ligands, functional groups, and metal ions. The evaluation encompassed a range of aspects including adsorption isotherms of pure gases [CO2 and nitrogen (N2)] and mixed gas mixture (CO2 and N2 with 15:85% ratio), along with utilization of the ideal adsorbed solution theory (IAST) to simulate multicomponent gas adsorption isotherms. Moreover, the reliability of IAST for mixed gas adsorption prediction has been investigated in detail. The research offers valuable insights into the correlation between the characteristics of MOFs and their effectiveness in gas separation and how these characteristics contribute to the differences between IAST predictions and experimental results. The findings enhance the understanding of how to enhance MOF characteristics in order to reduce CO2 emissions and also highlight the need for advanced models that consider thermodynamic nonidealities to accurately predict the behavior of mixed gas adsorption in MOFs. As a result, the incorporation of MOFs with enhanced predictability and reliability into CO2 capture industrial processes is facilitated.

A Novel Fast Wavenumber Selection Scheme for Line-by-Line Monte Carlo Simulations of High Temperature Gases

Abstract Implementing line-by-line absorption spectra in the Monte Carlo method provides a benchmark solution for radiative heat transfer in participating media. It is, however, a computationally demanding calculation, and therefore its application is limited to small and medium-scale cases. In gas mixtures, one of the most time-consuming parts is the wavenumber selection for each emission bundle (aka photon). Due to interdependency of spectral emission of individual species, trial-and-error is needed to obtain the emission wavenumber of species. Doing trial-and-error with tight convergence threshold through large set of data increases the simulation time. This paper presents a novel scheme to select the wavenumber by adding a new dataset which circumvents the need for trial-and-error. The performance of the new scheme is exhibited in three different test cases containing CO2, H2O, and CO. An excellent agreement was observed between the results of the new and old schemes. Compared to the previously published hybrid selection scheme, the wavenumber selection is around seven times faster using the current scheme.

Characterization and electrochemical performance of plasma-nitrided titanium alloy for bipolar plates

Ti-N layer with a thickness about 1 ∼ 2.2 μm was formed on titanium alloys through plasma nitriding at 750 °C in NH3 and a mixture of NH3 and N2 (1:2) for 4 h. SEM and XRD were employed to characterize the microstructure and phase composition of nitrided layer. Electrochemical tests evaluated the anti-corrosion properties of the samples before and after nitrided in a simulated proton exchange membrane fuel cells (PEMFC) environment. Interface contact resistance (ICR) was also measured. Results indicated that the corrosion potential in cathodic conditions was increased from −415 mV for untreated titanium to 148 mV for that nitrided in mixture gas. While, the corrosion current density was reduced from 6.64 μA to 0.86 μA. Under a pressure of 140 N cm−2, the interfacial contact resistance of the untreated sample increased from 22.1 mΩ cm2 before corrosion testing to 40.5 mΩ cm2 after corrosion at cathodic conditions. The nitrided sample, on the other hand, saw its contact resistance rise from 4.5 mΩ cm2 before corrosion to 7.3 mΩ cm2 after corrosion. The Ti-N compound layer effectively diminished the corrosion current density and sustained an exceptionally low ICR under the simulated operating conditions of a bipolar plate.

Molecular simulation of the competitive adsorption of methane and carbon dioxide in the matrix and slit model of shale kerogen and the influence of water

Carbon dioxide enhanced shale gas recovery (CO2-EGR) technology is of great significance for shale gas extraction and carbon dioxide storage in subsurface, which involves the competitive adsorption in shale nanopores. Adsorption comparisons between the kerogen matrix and slit and between the pure gas and gas mixture are conducted in this study. Kerogen matrix and slit models are built with the type II-A kerogen macromolecules and adsorptions of CH4 and CO2 are modelled. It is seen: 1) The gas absolute adsorption increases with its molar fraction while decreases with temperature. The Langmuir pressure for CO2 decreases while that for CH4 increases with their molar fractions. The adsorption selectivity of CO2 over CH4 decreases with the increase in pressure and the CO2 fraction, while it is higher in the matrix than that in the slit. Water significantly reduces the gas adsorption especially for matrix. 2) CO2 has high affinity to the Sulfur and Nitrogen functional groups, while CH4 molecules mainly adsorb on the Sulfur, Nitrogen and Carbon functional groups, While water are strongly bound to the Oxygen functional groups with water cluster formed at high contents. 3) Lower interaction energies are shown in the matrix compared with the slit due to the adsorption superposition, which results in gases preferentially adsorbed in the matrix then on the slit surface in the kerogen slit model. The water interaction energy is lowest due to the hydrogen bond, while the interaction energy of CO2 is much smaller than that of CH4 indicating its adsorption advantage.

Revisiting the IR Spectra of H2S in an Argon Matrix: Identification of (H2S)n (n ≤ 4) Clusters via the Spectral Assignment of νS-H Transitions.

Small-molecular clusters of H2S up to tetramer have been experimentally identified in a cold and solid argon matrix by the spectral assignment of νS-H fundamental transitions for different H2S:argon mixing ratios. Normal-mode frequency calculations at the MP2-CP/aug-cc-pV(Q + d)Z level have been used to support the spectral assignments. In addition, modulations in relative populations of different clusters due to the annealing of the deposited matrix and the preheating of the H2S-argon gas mixture before deposition reinforced the spectral assignments. Variations in mixing ratio, annealing of the matrix, and preheating of the gas mixture have also been used, in a combined manner, to unambiguously identify the ν1 and ν3 bands of the H2S monomer, which has been a matter of dispute for a long period. The two bands have been identified at 2634.4 and 2648.0 cm-1, respectively, while three bands at 2581.5, 2568.4, and 2547.6 cm-1 have been assigned to H-bonded dimers, cyclic trimers, and cyclic tetramers, respectively. Multiple bands within 2550-2580 cm-1 have been assigned to caged tetramers. The cooperative strengthening of S-H···S H bonds in cyclic H2S clusters was evident from the linear increment in νS-H spectral shifts with cluster size.

Disc novae: thermodynamics of gas-assisted binary black hole formation in AGN discs

ABSTRACT We investigate the thermodynamics of close encounters between stellar mass black holes (BHs) in the gaseous discs of active galactic nuclei (AGNs), during which binary black holes (BBHs) may form. We consider a suite of 2D viscous hydrodynamical simulations within a shearing box prescription using the Eulerian grid code athena++. We study formation scenarios where the fluid is either an isothermal gas or an adiabatic mixture of gas and radiation in local thermal equilibrium. We include the effects of viscous and shock heating, as well as optically thick cooling. We co-evolve the embedded BHs with the gas, keeping track of the energetic dissipation and torquing of the BBH by gas and inertial forces. We find that compared to the isothermal case, the minidiscs formed around each BH are significantly hotter and more diffuse, though BBH formation is still efficient. We observe massive blast waves arising from collisions between the radiative minidiscs during both the initial close encounter and subsequent periapsis periods for successfully bound BBHs. These ‘disc novae’ have a profound effect, depleting the BBH Hill sphere of gas and injecting energy into the surrounding medium. In analysing the thermal emission from these events, we observe periodic peaks in local luminosity associated with close encounters/periapses, with emission peaking in the optical/near-infrared (IR). In the AGN outskirts, these outbursts can reach 4 per cent of the AGN luminosity in the IR band, with flares rising over 0.5–1 yr. Collisions in different disc regions, or when treated in 3D with magnetism, may produce more prominent flares.