Long-term Tests Research Articles

Syngas Production via Oxidative Reforming of Propane Using a CO2- and O2-Permeating Membrane

Recently, ceramic–carbonate membrane reactors have been proposed to selectively separate CO2 at elevated temperatures and to valorize this pollutant gas by coupling a catalyzed reaction. This work explores using a membrane reactor to perform the oxidative reforming of propane by taking advantage of the CO2- and O2-permeating properties of a LiAlO2/Ag–carbonate membrane. The fabricated membrane showed excellent permeation properties, such as CO2/N2 and O2/N2 selectivity, when operating in the 725–850 °C temperature range. The membrane exhibited remarkable stability during the long-term permeation test under operating conditions, exhibiting minor microstructural and permeation changes. Then, by packing a Ni/CeO2 catalyst, the membrane reactor arrangement showed efficient syngas production, especially at temperatures above 800 °C. A hydrogen-rich syngas mixture was obtained by the contributions of the oxidative reforming and cracking reactions. Specific issues observed regarding the membrane reactor’s performance are attributed to the catalyst that was used, which experienced significant poisoning by carbon deposition during the reaction, affecting syngas production during the long-term test. Thermodynamic calculations were performed to support the experimental results.

Unique High-Resolution Temperature Mapping of Stage 1 Turbine Vane in a Long-Term Engine Test

Abstract In this study, surface temperature maps resulting from a long-term engine test were evaluated on a stage 1 turbine vane using thermal history coatings (THCs). THCs are ceramic-type sensor coatings doped with a lanthanide ion, giving the coating photoluminescent properties. The THC's structure permanently changes when exposed to high temperatures, which in turn alters its photoluminescent properties. Therefore, historic maximum temperature maps are evaluated by optically probing the THC point-by-point across the vane's surface. The vane was exposed to a non-dedicated (multi-cycle, multi temperature-level) engine test lasting over 8 months. Two passes of THC measurements were taken, termed low resolution (LR) and high resolution (HR), each, respectively, with point pitches of 5 mm and 1 mm. The latter provided a unique insight into the historic maximum temperature profile of the vane, particularly around high-temperature gradient regions, such as those close to effusion cooling holes. The THC temperatures were compared to the engine manufacturer's (Doosan Enerbility) heat transfer code (Doosan Integrated Thermal Analysis for Cooling System (DiTACS)) for validation. The THC temperature mapping was successful with good coverage across the vane. The leading edge and pressure side trailing edge regions were typically the hottest. The HR measurements clearly show sharp thermal gradients around the effusion cooling holes on the vane's airfoil and platforms. Critically, the THC measurements were compared very well to the DiTACS measurements, validating THCs as a credible temperature measurement technique for long-term, non-dedicated engine tests for components operating in some of the most extreme environments of an engine.

Numerical study of the influence of temperature data error on the determination of frictional heat generation

Subject of research: determination of the friction torque and functions of the specific intensity of heat generation in system of sliding bearings. The purpose of the study: To develop a method for determining the friction torque in sliding bearings using temperature data. Based on computational experiments, study the influence of errors in temperature data on the solution of the inverse problem. Methods and object of research: A system of sliding bearings made of a polymer composite material on which a rotating shaft rests is considered. A mathematical model of the thermal process in the considered system of friction units is presented, taking into account the spatial distribution of temperature and its change over time. The temperature is measured at several points in each bearing. Frictional heat generation is determined by solving the inverse heat conduction problem from the condition that the measured and calculated temperatures are close. To ensure continuous data processing and determine the friction torque during long-term tests, the inverse problem of determining the friction torque from temperature data is solved at successive short time intervals. Then the resulting solutions are «glued together». The main results of the study: With such a restoration, the discrepancy between the specified and restored functions of the specific intensity of heat generation is 10–15 % with an error level in temperature data of 10 %. The developed algorithm for solving the inverse problem of thermal conductivity can be used to determine the friction torques in real systems of self-lubricating sliding bearings.

Study of the effect of N, N-diethyl hydroxyl amine/multi-layered graphene oxide hybrid on reducing cathodic delamination and increasing corrosion resistance of epoxy coating on steel substrate

In this study, a hybrid of multi-layered graphene oxide (MLGO) and oxygen absorbent corrosion inhibitor N, N-diethyl hydroxylamine (DEHA) was investigated. The nano hybrid was prepared in order to reduce the amount of cathodic delamination and increase the corrosion resistance of the epoxy coating. Epoxy coatings were prepared using the optimal percentage of 0.75 wt. % of the nano hybrid with different ratios between MLGO and DEHA like (1:2), (1:1) and (2:1). Mapping energy-dispersive X-ray spectroscopy, thermo gravimetry analysis and Fourier transform infrared (FT-IR) analysis indicated the uniform distribution of the inhibitor throughout the MLGO structure and the hydrogen bond interactions between them. The results of FT-IR spectroscopy: attenuated total reflectance test after six months confirmed the presence and stability of the inhibitor in the coating. Also, the results of 800 h of salt spray test and the long-term electrochemical impedance test after 7 months showed that the epoxy coating, containing MLGO-DEHA (1:2) had the highest corrosion resistance (2.54 × 107 Ω cm2) and the lowest cathodic delamination (15.9%). The results were also confirmed by cathodic delamination and pull-off adhesion tests.

The Effects of Model Insoluble Copper Compounds in a Sedimentary Environment on Denitrifying Anaerobic Methane Oxidation (DAMO) Enrichment

The contribution of denitrifying anaerobic methane oxidation (DAMO) as a methane sink across different habitats, especially those affected by anthropogenic activities, remains unclear. Mining and industrial and domestic use of metals/metal-containing compounds can all cause metal contamination in freshwater ecosystems. Precipitation of metal ions often limits their toxicity to local microorganisms, yet microbial activity may also cause the redissolution of various precipitates. In contrast to most other studies that apply soluble metal compounds, this study investigated the responses of enriched DAMO culture to model insoluble copper compounds, malachite and covellite, in simulated sedimentary environments. Copper ≤ 0.22 µm from covellite appeared to cause immediate inhibition in 10 h. Long-term tests (54 days) showed that apparent methane consumption was less impacted by various levels of malachite and covellite than soluble copper. However, the medium-/high-level malachite and covellite caused a 46.6–77.4% decline in denitrification and also induced significant death of the representative DAMO microorganisms. Some enriched species, such as Methylobacter tundripaludum, may have conducted DAMO or they may have oxidized methane aerobically using oxygen released by DAMO bacteria. Quantitative polymerase chain reaction analysis suggests that Candidatus Methanoperedens spp. were less affected by covellite as compared to malachite while Candidatus Methylomirabilis spp. responded similarly to the two compounds. Under the stress induced by copper, DAMO archaea, Planctomycetes spp. or Phenylobacterium spp. synthesized PHA/PHB-like compounds, rendering incomplete methane oxidation. Overall, the findings suggest that while DAMO activity may persist in ecosystems previously exposed to copper pollution, long-term methane abatement capability may be impaired due to a shift of the microbial community or the inhibition of representative DAMO microorganisms.

Control of membrane biofouling in MBR for wastewater treatment by biohybrid membrane with superhydrophilic self-QQ function

Quorum quenching (QQ) is an effective method for controlling MBR (membrane bioreactor) membrane biofouling by regulating the release of autoinducer during the quorum sensing (QS) process. However, the addition of QQ bacteria solution or QQ carriers inevitably leads to unpredictable effects on MBR microbial systems and operational efficiency (for example, reduced stability of nitrification and denitrification processes, reduced biodegradation efficiency and unbalanced biofilm formation etc.). Here, we present a biohybrid membrane called ES-BM (electrospinning-biohybrid membrane), which features a unique pore size structure consisting of electrospun superhydrophilic nanofiber sheaths, a self-QQ layer (active QQ bacteria are immobilized within the interlayer structure of this biohybrid membrane to inhibit the QS process of biofilm-forming associated bacteria at the source surface where membrane biofouling occurs), and a basement filter layer, which maintain the activity of QQ bacteria for an extended period. The ES-BM extends operational cycles up to 21 days at a constant flux of 24 L/m²/h, which is three times longer than conventional MBR systems. The membrane exhibits exceptional hydrophilicity (water contact angle of approximately 0° within 2 seconds) and high tensile strength (Young’s modulus of 135 MPa). Long-term bioactivity tests confirm the stability and recyclability of the ES-BM. Additionally, microbial community analysis suggests that the biohybrid membrane suppresses the growth of biofilm-related bacteria without significantly affecting the indigenous microbial population, further enhancing system performance. This work demonstrates the potential of ES-BM for improving MBR biofouling resistance and presents insights into scalable electrospinning fabrication techniques.

ENHANCING SURFACE CHARACTERISTICS OF AA2024-T3 AIRCRAFT ALLOY THROUGH SYNERGISTIC ANODIZATION AND CERIUM CONVERSION COATING. PART I: PERFORMANCE IN MODEL CORROSIVE MEDIUM

The present study is devoted to the monitoring of the performance of AA2024-T3 specimens, after the formation of Anodic Aluminum Oxide (AAO) layer and/or deposition of a Ceruim Conversion Coating (CeCC), obtained at 20°C and 50°C, respectively. Although both methods are well described in the literature, there is no sufficient information regarding the effect of their combination on their behaviour in corrosive media. The performance of the respective specimens was elucidated after 24 h of exposure to 3.5 % NaCl model corrosive medium (MCM) by means of Electrochemical Impedance Spectroscopy (EIS) and acquisition of Potentiodynamic Scanning (PDS) curves. Since the combined AAO/CeCC coating primers revealed superior barrier properties, the respective specimens weresubjected to long-term corrosion tests of up to 672 h of exposure to the MCM to evaluate their durability. The results revealed the synergistic effect of the combination of the surface treatment procedures on effective corrosion mitigation.

Oxygen Vacancy-Electron Polarons Featured InSnRuO2 Oxides: Orderly and Concerted In-Ov-Ru-O-Sn Substructures for Acidic Water Oxidation.

Polymetallic oxides with extraordinary electrons/geometry structure ensembles, trimmed electron bands, and way-out coordination environments, built by an isomorphic substitution strategy, may create unique contributing to concertedly catalyze water oxidation, which is of great significance for proton exchange membrane water electrolysis (PEMWE). Herein, well-defined rutile InSnRuO2 oxides with density-controllable oxygen vacancy (Ov)-free electron polarons are firstly fabricated by in situ isomorphic substitution, using trivalent In species as Ov generators and the adjacent metal ions as electron donors to form orderly and concerted In-Ov-Ru-O-Sn substructures in the tetravalent oxides. For acidic water oxidation, the obtained InSnRuO2 displays an ultralow overpotential of 183 mV (versus RHE) and a mass activity (MA) of 103.02 A mgRu -1, respectively. For a long-term stability test of PEMWE, it can run at a low and unchangeable cell potential (1.56 V) for 200 h at 50 mA cm-2, far exceeding current IrO2||Pt/C assembly in 0.5 m H2SO4. Accelerated degradation testing results of PEMWE with pure water as the electrolyte show no significant increase in voltage even when the voltage is gradually increased from 1 to 5 A cm-2. The remarkably improved performance is associated with the concerted In-Ov-Ru-O-Sn substructures stabilized by the dense Ov-electron polarons, which synergistically activates band structure of oxygen species and adjacent Ru sites and then boosting the oxygen evolution kinetics. More importantly, the self-trapped Ov-electron polaron induces a decrease in the entropy and enthalpy, and efficiently hinder Ru atoms leaching by increasing the lattice atom diffusion energy barrier, achieves long-term stability of the oxide. This work may open a door to design next-generation Ru-based catalysts with polarons to create orderly and asymmetric substructures as active sites for efficient electrocatalysis in PEMWE application.

Electrospun Sulfonated Poly(ether ether ketone) and Chitosan/Poly(vinyl alcohol) Bifunctional Nanofibers to Accelerate Proton Conduction at Subzero Temperature.

Multilayered microstructures can accelerate the proton conduction process in proton exchange membranes (PEMs). Herein, we design and construct PEMs with microstructures based on bifunctional nanofibers and sulfonated poly(ether ether ketone) (SPEEK) nanofibers. Specifically, the bifunctional nanofibers composed of poly(vinyl alcohol) and chitosan are prepared and then combined with the electrospun SPEEK nanofibers. The stable microstructure is derived from the compatible interfacial property of nanofibers and the formed hydrogen bonds. The multilayered microstructure consisting of nanofibers accelerates the proton conduction even at subzero temperature because of regulating the proton conduction pathways. Specifically, the (SKNF/CPNF/SKNF)/PA membrane exhibits the proton conductivities of (0.951 ± 0.138) × 10-2 S/cm at -30 °C and (7.32 ± 0.37) × 10-2 S/cm at 160 °C. Additionally, the fine proton conductivity stability is demonstrated by the proton conductivity in the long-term test and the cooling/heating cycle test, such as 1.67 × 10-2 S/cm at -30 °C (after 1000 h), 4.52 × 10-2 S/cm at 30 °C (after 810 h), 1.12 × 10-2 S/cm at -30 °C, and 1.01 × 10-1 S/cm at 30 °C in the cooling/heating process (5 cycles). The single fuel cell possesses an open-circuit voltage of 0.886 V and a peak power density of 0.508 W/cm2 at 130 °C.

Cuboidal molybdenum sulfur clusters as a platform to construct novel catalysts for propane dehydrogenation

Growing demand for short chain olefins such as propylene for plastic production drives the development of high performing catalysts for propane dehydrogenation (PDH). Here, a confinement strategy originating from metal-sulfur clusters was employed to fabricate defective MoPtSx phase via anchoring by coordinatively unsaturated Al sites present on alumina, followed by reduction under H2 flow at high temperature. This catalyst with a low Pt content exhibits great ability for C–H activation with high intrinsic activity and facile propylene desorption in PDH reaction. More importantly, the catalyst shows excellent stability during long-term tests with both stable conversion and selectivity. Through combined X-ray absorption spectroscopy, electron microscopy and electron paramagnetic resonance measurements it could be affirmed that interaction between isolated and electron-enriched Pt sites as well as their proximity to adjacent sulfur vacancies is vital for the first and second C–H bond activation, while suppressing C–C cleavage which otherwise lead to coking.

Discerning the effect of various irradiation modes on the corrosion of Zircaloy-4

Using proton irradiation, this study investigates the individual influence of several factors on the corrosion kinetics of Zircaloy-4 in a hydrogenated water environment simulating a Pressurized Water Reactor (PWR). Using both simultaneous irradiation-corrosion and autoclave corrosion, we separately examine (i) the effect of pre-irradiation on modifying the structure of the material, (ii) the impact of irradiation on creating defects in the growing oxide layer during corrosion, and (iii) the influence of irradiation on increasing the corrosion potential through radiolysis during corrosion. To replicate the neutron-irradiated microstructure, two proton pre-irradiation schedules were employed: Schedule 1 (isothermal irradiation at 350°C to 5 dpa) to simulate high-temperature PWR conditions, and Schedule 2 (two-step process: irradiation to 2.5 dpa at -10°C followed by 2.5 dpa at 350°C) to simulate lower temperature PWR and Boiling Water Reactor (BWR) conditions. Long-term autoclave corrosion testing for 360 days at 320°C revealed no significant difference between unirradiated samples and those pre-irradiated according to either schedule, with all samples exhibiting sub-cubic kinetics within the pre-transition regime. Pre-irradiated samples underwent Simultaneous Irradiation Corrosion (SIC) tests, corroding in 320°C water while being irradiated with protons. Corrosion was found to accelerate in all SIC-tested samples relative to autoclave conditions, with the greatest increase observed in non-pre-irradiated regions of the samples. Pre-irradiation with either schedule resulted in a slower corrosion rate compared to non-pre-irradiated regions under SIC conditions. The degree of radiolysis observed in the SIC tests surpassed typical PWR conditions, approaching levels found in BWRs. Radiolysis products were identified as a primary contributors to accelerated corrosion, corroborated by radiolysis bar tests. These findings underscore the intricate interactions between irradiation, corrosion, and water chemistry in determining Zircaloy-4 corrosion kinetics within nuclear reactor environments.

Synthesis of Novel Graphene Oxide-chitosan-silicon Dioxide Nanocomposite Embedded in Polysulfone Membrane for Oily Water Treatment

Oil and gas exploration activities result in generation of large quantities of produced water. Globally, for each barrel of oil, three barrels of produced water is generated. The oil content in produced water can vary between 3 and 20% depending on the location and age of the hydrocarbon well. Due to their hydrophobic nature, conventional hydrophobic polymeric membranes struggle to effectively separate oil from produced water. In this work, an innovative strategy is suggested by employing a hydrophilic/super-oleophobic nanocomposite to develop novel polymeric membranes able to effectively separate oil content from produced water without negatively affecting the other membrane properties such as the total flux and fouling. Graphene oxide-chitosan-silicone oxide (GO-CH-SiO2) nanocomposite was synthesized by functionalizing graphene oxide (GO) with chitosan (CH) and silicon dioxide (SiO2). To improve the membrane flux, anti-fouling propensity, and oil rejection, the synthesized nanocomposites were doped in the polysulfone membranes matrix. The effect of GO-CH-SiO2 concentration, GO:CH ratio, and GO-CH:SiO2 ratio on the performances of developed membranes was experimentally assessed, and morphology of the synthesized membrane was investigated using appropriate characterization techniques. The experimental results showed that the membrane with GO:CH of 1:2 and GO-CH: SiO2 ratio of 1:6.5 showed the highest pure water permeation flux of 28.35 LMH/bar with a comparable flux recovery rate of 76% and oil rejection efficiency of 98.5%. The study’s findings underscore the potential of GO-CH-SiO2 nanocomposite membranes for oil–water separation research, presenting a promising solution for treating produced water in the oil and gas industry. Further research is needed to scale up this technology and improve membrane performance by optimizing the nanocomposite composition and conducting long-term performance tests.

Karakteristik Breakdown Voltage Pada Dielektrik Minyak Mineral dan Minyak Ester Natural

The increasing demand for electrical energy, driven by population growth and industrial development, necessitates efficient and sustainable power distribution systems. Transformers, essential components of these systems, typically use mineral oil for insulation and cooling, despite its environmental drawbacks, such as high carbon emissions and non-biodegradability. In response, natural ester oils have emerged as eco-friendly alternatives. This study aimed to compare the dielectric breakdown voltage characteristics of mineral oil (Diala B) and natural ester oil (FR3) in transformer applications. The testing followed the IEC 60156 standard, focusing on transformers operating at 20 kV, with a minimum breakdown voltage threshold of 30 kV/2.5mm. Both treated and untreated samples were examined.The results indicated that FR3 ester oil exhibited superior dielectric properties, including higher breakdown voltage, flashpoint, and firepoint, as well as lower carbon emissions compared to mineral oil. These findings suggest that natural ester oil has significant potential as a sustainable replacement for mineral oil, particularly in applications where environmental and safety concerns are prioritized.The study recommends further long-term testing under operational conditions to confirm the performance and stability of ester oil in real-world transformer applications. These findings contribute to the growing body of research supporting the transition to more environmentally friendly transformer insulation materials, which could have broad implications for the power industry’s sustainability efforts

Metabolomic alterations in the plasma of patients with various clinical manifestations of COVID-19

BackgroundThe metabolomic profiles of individuals with different clinical manifestations of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection have not been clearly characterized.MethodsWe performed metabolomics analysis of 166 individuals, including 62 healthy controls, 16 individuals with asymptomatic SARS-CoV-2 infection, and 88 patients with moderate (n = 42) and severe (n = 46) symptomatic 2019 coronavirus disease (COVID-19; 17 with short-term and 34 with long-term nucleic-acid test positivity). By examining differential expression, we identified candidate metabolites associated with different SARS-CoV-2 infection presentations. Functional and machine learning analyses were performed to explore the metabolites’ functions and verify their candidacy as biomarkers.ResultsA total of 417 metabolites were detected. We discovered 70 differentially expressed metabolites that may help differentiate asymptomatic infections from healthy controls and COVID-19 patients with different disease severity. Cyclamic acid and N-Acetylneuraminic Acid were identified to distinguish symptomatic infected patients and asymptomatic infected patients. Shikimic Acid, Glycyrrhetinic acid and 3-Hydroxybutyrate can supply significant insights for distinguishing short-term and long-term nucleic-acid test positivity.ConclusionMetabolomic profiling may highlight novel biomarkers for the identification of individuals with asymptomatic SARS-CoV-2 infection and further our understanding of the molecular pathogenesis of COVID-19.

Enhancing Performance of Composite-Based Triboelectric Nanogenerators Through Laser Surface Patterning and Graphite Coating for Sustainable Energy Solutions

The performance of composite-based triboelectric nanogenerators (C–TENGs) was significantly enhanced through laser surface patterning and graphite coating. The laser etching process produced accurate and consistent patterns, increasing surface area and improving charge accumulation. SEM imagery confirmed the structural differences and enhanced surface properties of the laser-etched C–TENGs. Graphite fibers further augmented the contact surface area, enhancing charge accumulation and diffusion. Experimental results demonstrated that the optimized C–TENGs, especially those with line patterns and graphite coating, achieved a maximal 98.87 V open-circuit voltage (VOC) and a 0.10 µA/cm2 short-circuit current density (JSC) under a 20 N external force. Environmental tests revealed a slight decrease in performance with increased humidity, while long-term stability tests indicated consistent performance over three weeks. Practical application tests showed the potential of C–TENGs integrated into wearable devices, generating sufficient energy for low-power applications, thereby highlighting the promise of these devices for sustainable energy solutions.

A web-based safety management platform to enhance safety for Chinese migrant construction workers

Over the past decade, existing research has investigated various solutions to enhance safety management on construction sites. Among the many solutions, developing a web-based safety platform has increasingly become a key element in safety improvement strategies. International research shows that safety management platforms improve migrant workers’ safety, but evidence for such interventions in New Zealand, especially for Chinese migrant construction workers, remains limited. This study built a web prototype catering to Chinese migrant construction workers in New Zealand. The data collection method was semi-structured interviews, and the effectiveness of the novel web prototype was validated based on respondents’ feedback. Results show that this safety web prototype can effectively improve the safety knowledge and safety awareness of Chinese migrant construction workers by providing local safety policies and conducting multi-frequency long-term safety training tests. The incentive function in this web prototype can motivate Chinese migrant construction workers to use this application and enhance their safety compliance. The limitations of this research include geographical restrictions and a small sample size to evaluate the effectiveness of the prototype. Future research should incorporate a larger, cross-sectional sample to assess the effectiveness of web-based safety awareness solutions, enabling more generalizable conclusions for construction workers of diverse nationalities and regions.

Iron and Nitrogen-Doped Wheat Straw Hierarchical Porous Carbon Materials for Supercapacitors.

In this paper, we prepared a new type of iron and nitrogen co-doped porous carbon material (WSC-Fe/N) using a carbonization-activation process with wheat straw as a precursor and FeCl3 and NH4Cl as co-doping agents and analyzed the electrochemical properties of the resulting electrode material. Through precise control of the doping elements and carbonization temperature (900 °C), the resulting WSC-Fe/N-900 material exhibits abundant micropores, uniform mesopores, a significant specific surface area (2576.6 m2 g-1), an optimal level of iron doping (1.7 wt.%), and excellent graphitization. These characteristics were confirmed through X-ray diffraction and Raman spectroscopy. Additionally, the WSC-Fe/N-900 electrode demonstrated a specific capacitance of 400.5 F g-1 at a current density of 0.5 A g-1, maintaining a high capacitance of 308 F g-1 even at 10 A g-1. The solid-state symmetric supercapacitor in an aqueous electrolyte achieved an energy density of 9.2 Wh kg-1 at a power density of 250 W kg-1 and maintained an energy density of 6.5 Wh kg-1 at a power density of 5000 W kg-1, demonstrating remarkable synergistic energy-power output characteristics. In terms of structural properties, the porous characteristics of WSC-Fe/N-900 not only enhance the specific surface area of the electrode but also improve the diffusion capability of electrolyte ions within the electrode, thereby enhancing capacitance performance. The reliability of the electrode material demonstrated good performance in long-term cycling tests, maintaining a capacitance retention rate of 93% after 10,000 charge-discharge cycles, indicating excellent electrochemical stability. Furthermore, over time, the aging effect of the WSC-Fe/N-900 electrode material is minimal, maintaining high electrochemical performance even after prolonged use, suggesting that this material is suitable for long-term energy storage applications. This study introduces a novel strategy for producing porous carbon materials for supercapacitors, advancing the development of economically efficient and environmentally friendly energy storage solutions.

Visible-light-activated Fe2O3–TiO2 nanoparticles enhance biofouling resistance of polyethersulfone ultrafiltration membranes against marine algae Chlorella vulgaris

This study investigated the modification of polyethersulfone (PES) ultrafiltration membranes with TiO2 and Fe2O3–TiO2 nanoparticles to enhance their hydrophilicity and biofouling resistance against the marine microalgae Chlorella vulgaris. It is a common freshwater and marine microalga that readily forms biofilms on membrane surfaces, leading to significant flux decline and increased operational costs in ultrafiltration processes. The microalgae cells and their extracellular polymeric substances (EPS) adhere to the membrane surface, creating a dense fouling layer that impedes water permeation. The modified membranes were characterized using contact angle measurements, scanning electron microscopy, and pure water flux/resistance tests. Short-term ultrafiltration experiments evaluated the membranes’ antifouling performance by measuring flux decline, flux recovery ratio, and relative flux reduction during C. vulgaris filtration. The TiO2 membrane showed improved hydrophilicity and antifouling over the pristine PES membrane, while the Fe2O3–TiO2 nanocomposite membrane exhibited the best performance. It reduced the water contact angle and showed only a 5% relative flux reduction compared to 60% for the pristine membrane. SEM images confirmed reduced microalgal deposition on the nanocomposite surface. Long-term tests with microalgal cells under dark and visible light conditions in saline water further assessed the membranes’ biofouling resistance. The Fe2O3–TiO2 membrane maintained 59 L/m2 h water flux under visible light after immersion in the microalgal solution, outperforming the pristine (38 L/m2 h) and TiO2 (52 L/m2 h) membranes. This superior antifouling was attributed to photocatalytic generation of reactive oxygen species inhibiting microalgal adhesion. This study demonstrates a promising strategy for mitigating biofouling in membrane-based water treatment and desalination processes.

Innovative thermal crosslinked polyimide gas separation membrane with highly selective and resistance to physical aging base on phenyl ethynyl

In this study, a high performance phenyl ethynyl thermal crosslinked 6FDA-based polyimide (CR-4ETA-x) was developed, which has high gas permeability and selectivity, resistance to physical aging. By introducing 4,4′-(Acetylene-1,2-diyl) diphthalic anhydride (4ETA) monomer into the polyimide structure, the thermal crosslinking precursor membrane was formed. The precursor membrane was heat treated at 440℃ to obtain CR-4ETA-x. After heat treatment, we detected the olefin radical in the crosslinked membrane by electron paramagnetic resonance, which proved that the polyimide network was formed. This allows the crosslinked membrane to have greater d-spacing, higher rigidity, and BET surface area. The CO2 permeability of CR-4ETA-5% is 4114 barrer and the CO2/CH4 selectivity is 19.22. Compared to 6FDA-DAM, the CO2 permeability increased by 477% while the selectivity decreased by only 17%. CR-4ETA-20% shows the CO2 permeability of 3560 Barrer and CO2/CH4 selectivity of 21.1 in CO2/CH4 mixed-gas. After 60 days of aging the permeability maintenance of CR-4ETA-20% were 88%, 84%, 83% and 91% for O2, N2, CO2 and CH4. In addition, in the long-term stability test of more than 100 h, the separation performance of CR-4ETA-20% did not decrease significantly. However, CR-4ETA-x also has limitations, such as poor stability in alkaline environments and lower gas permeability than some advanced carbon molecular sieve membranes. In general, the method of phenyl ethynyl thermal crosslinking provides an effective way for the development of CO2 separation membranes with possible applications.

Saline based microfluidic soft pressure sensor utilizing a three-dimensional focused electric field for motion and healthcare monitoring

This paper introduces the ‘Spatially Focused Saline-based Pressure Sensor (SF-SaPS)', a novel soft microfluidic pressure sensor featuring a distinctive three-dimensional focusing structure. By critically reducing the cross-sectional area of the microchannel at the focused structure, the SF-SaPS achieves excellent sensitivity to pressure within the sensing region. With the spatially focused region, the SF-SaPS could detect a wide range of pressure from gentle touches to human weight, which is typically unachievable with low-conductivity sensing media such as saline, a medium inherently safe for human use. Beyond its sensitivity, the SF-SaPS exhibits sensing performance and stability comparable with conventional liquid metal-based pressure sensors. Our sensor demonstrated minimal signal drift, a rapid response time of 70 ms under cyclic loading, and 20-day long-term stability tests immersed in water. Additionally, the sensor possesses a transparency advantage unattainable by liquid metal sensors as we utilized transparent polymers and saline. A unique advantage of the SF-SaPS lies in its selective spatial and mechanical sensitivity; as the electrical resistance is highly dependent on changes in the cross-sectional area of the microchannels, the sensor has superior pressure sensitivity compared to bending and strain. Finally, various application examples highlight the SF-SaPS's advantages. By configuring the sensor in a two-axis array, the SF-SaPS facilitates pressure mapping across a plane. Additionally, it proves effective in healthcare monitoring, from radial pulse to finger movements. In conclusion, the SF-SaPS's combination of performance, stability, biocompatibility, and transparency positions this sensor as a versatile tool for applications extending beyond healthcare, as demonstrated in this study.