The effect of ammonium structure on partially fluorinated anion exchange membranes was investigated for alkaline fuel cell applications. Precursor copolymers tethered with bromopropyl side chains ...(PAF-C3-Br) were successfully synthesized and quaternized quantitatively with amines to obtain a series of QPAF-C3-XY membranes containing various ammonium head groups. The head groups (XY) included dimethylbutyl (DMB), dimethylhexyl (DMH), dibutylmethyl (DB), and heterocyclic N-methylpiperidinium (Pip). All of the membranes exhibited well-developed phase-separated morphology regardless of the size of the head groups as confirmed by TEM images. DFT calculations suggested that the hydrophilic domain sizes (determined from TEM images) were dependent on the polar surface area (PSA) rather than the molecular volume of the head groups. Among the membranes, QPAF-C3-Pip possessed the most balanced properties of high conductivity, low water absorbability, reasonable mechanical strength, and alkaline stability. QPAF-C3-Pip membrane (IEC = 1.26 meq/g) achieved 232 mW/m2 of the maximum power density in alkaline fuel cell, which was slightly higher than that of our previous QPAF-C3-TMA with typical trimethyl ammonium head groups (224 mW/cm2). In the durability test for 240 h, the voltage decreased from 0.74 V to 0.43 V with average decay of 1.29 mV/h. The post-durability NMR analysis revealed that the majority of the voltage loss was related to the catalyst layers.
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•Piperidinium head groups provide anion exchange membrane with the most balanced properties.•The anion exchange membranes survive in 4 M KOH at 80 °C for 736 h maintaining 85% of the conductivity.•In H2/O2 fuel cell, the anion exchange membrane achieved reasonable performance and durability.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Three novel series of pyridine derivatives, namely Schiff’s bases, 4-thiazolidinones and azetidin-2-ones bearing pyrazolo3,4-bpyridine moiety, have been synthesized. The chemical structures of the ...synthesized compounds were characterized. The compounds were tested for their antimicrobial activity using the agar well diffusion and broth macrodilution methods. The compounds were also evaluated for their antiproliferative activity using the sulforhodamine B (SRB) assay. The majority of the tested compounds exhibited slight to high antimicrobial activity against the test microorganisms with minimum inhibitory concentrations (MICs) of 0.12–62.5 µg/mL when compared to that of 3 standard antimicrobial agents (Ampicillin, 0.007–0.03 µg/mL; Gentamicin; 0.015–0.24 µg/mL; and Amphotericin B, 0.03–0.98 µg/mL). Compound (7b) was found to be nearly as active as the standard antimicrobial drug Amphotericin B against Fusarium oxysporum fungal strain with MIC of 0.98 µg/mL. Some of the test compounds showed remarkable cytotoxic activities against Hep G2 (hepatocellular carcinoma) cells (IC50=0.0158–71.3 µM) in comparison to the standard anticancer drug doxorubicin (IC50=0.008 µM). Among the compounds tested, (5), (6a), (6b), (7b), and (10) exhibited antiproliferative potency (IC50=0.0001–0.0211 µM) that was found to be better than that of doxorubicin (IC50=0.099 µM) against MCF7 (breast adenocarcinoma) cells. In particular, (7b) displayed the highest significant antiproliferative efficacy against both Hep G2 and MCF7 cell lines showing IC50 values of 0.0158 µM and 0.0001 µM, respectively. Our findings suggest that the synthesized compounds may be promising candidates as novel antimicrobial and antiproliferative agents.
For robust anion exchange membranes, we have investigated the effect of aliphatic side chains on the properties of partially fluorinated aromatic copolymers (QPAFs) with ammonium groups. A new series ...of QPAF membranes with various interstitial aliphatic side chain lengths (QPAF-C x ) where x = 2–6 were successfully synthesized. QPAF-C3 with a propylene side chain and ion exchange capacity (IEC = 1.24 meq. g −1 ) showed balanced properties with the highest hydroxide ion conductivity (99 mS cm −1 at 80 °C in water) and relatively low water uptake, based on a well-developed phase separated morphology. Moreover, the QPAF-C3 membrane exhibited excellent alkaline stability to maintain high ion conductivity (98% remaining) and high mechanical properties after 1000 h in 1 M KOH at 80 °C. The QPAF-C3 membrane also revealed reasonable stability even in 4 M and 8 M KOH at 80 °C. In fuel cell operation, the QPAF-C3 membrane exhibited a higher power density (224 mW cm −2 ) than those of our previous QPAF-C1 (138 mW cm −2 ), QPAF-C1B (167 mW cm −2 ), and Tokuyama A-201 (122 mW cm −2 ) membranes. In the durability test for 62 h, QPAF-C3 maintained 69% of its initial voltage with minor structural degradation.
The use of the friction stir welding (FSW) process as a relatively new solid-state welding technology in the aerospace industry has pushed forward several developments in different related aspects of ...this strategic industry. In terms of the FSW process itself, due to the geometric limitations involved in the conventional FSW process, many variants have been required over time to suit the different types of geometries and structures, which has resulted in the development of numerous variants such as refill friction stir spot welding (RFSSW), stationary shoulder friction stir welding (SSFSW), and bobbin tool friction stir welding (BTFSW). In terms of FSW machines, significant development has occurred in the new design and adaptation of the existing machining equipment through the use of their structures or the new and specially designed FSW heads. In terms of the most used materials in the aerospace industry, there has been development of new high strength-to-weight ratios such as the 3rd generation aluminum-lithium alloys that have become successfully weldable by FSW with fewer welding defects and a significant improvement in the weld quality and geometric accuracy. The purpose of this article is to summarize the state of knowledge regarding the application of the FSW process to join materials used in the aerospace industry and to identify gaps in the state of the art. This work describes the fundamental techniques and tools necessary to make soundly welded joints. Typical applications of FSW processes are surveyed, including friction stir spot welding, RFSSW, SSFSW, BTFSW, and underwater FSW. Conclusions and suggestions for future development are proposed.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The probably designed heterojunction is promising issue for destruction of organic pollutants in wastewater under sunlight energy. Herein, a novel AgIO
4
/TiO
2
heterojunctions containing (5 wt%, 10 ...wt%, 15 wt%, and 20 wt%) AgIO
4
were emerged for exceptional photocatalytic degradation of rhodamine B dye in short contact time adopting direct Z-scheme mechanism. Titania single phase was synthesized by sol-gel using Triton X-100; however, novel AgIO
4
nanoparticles were incorporated on titania surface through sonochemical route. The as-synthesized nanocomposites were systematically characterized by x-ray powder diffraction, N
2
adsorption-desorption isotherm, x-ray photoelectron spectroscopy, diffuse reflectance spectroscopy, photoluminescence (PL), energy-dispersive x-ray spectroscopy, mapping, and high-resolution transmission electron microscopy. Mass ratio of AgIO
4
plays a pivotal role in light-harvesting absorption and enhancing the photocatalytic efficiency. Surprisingly, remarkable shifts in AgIO
4
diffraction peaks, distortion in the nanostructure, and reduction in PL intensity of titania reveal the successful construction of AgIO
4
/TiO
2
heterojunctions. The as-achieved AgIO
4
/TiO
2
nanoparticles exhibit an excellent photoreactivity and stability toward degradation of RhB with optimal concentration 10 wt% AgIO
4
for removal 98% of RhB dye on 0.3 g/L photocatalyst compared with 62% removal on bare TiO
2
under the same reaction conditions. The exceptional reactivity of the heterojunction was ascribed to extending the light-harvesting and novel direct Z-scheme mechanism which not only improves the quantum power of charge carrier separation, but also enhances the oxidative and reductive efficiency of the photogenerated holes and electrons.
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BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
A series of anion exchange membranes (QPE-bl-9) based on a partially fluorinated hydrophobic segment and oligophenylene as scaffolds for ammonium cations were synthesized to evaluate the effect of ...the various ammonium groups derived from trimethyl amine (TMA), dimethyl hexyl amine (DMHA), methyl imidazole (MIm), dimethyl imidazole (DMIm), tributyl amine (TBA), and dicyclohexyl methyl amine (DCHMA) on the membrane properties. QPE-bl-9 membranes were well characterized by 1 H NMR spectroscopy, in which all the peaks were assigned to the supposed structure. The TEM images of QPE-bl-9–TMA, –MIm, –DMIm and –DMHA membranes showed small hydrophilic/hydrophobic phase separated morphology (hydrophilic domains 1–3 nm). QPE-bl-9–TMA (1.6 mequiv. g −1 ) exhibited the highest hydroxide ion conductivity (101 mS cm −1 at 80 °C) among the tested membranes, followed by QPE-bl-9–DMHA (62 mS cm −1 ) and QPE-bl-9–DMIm (62 mS cm −1 ). The alkaline stability of the membranes was tested in 1 M KOH at 60 °C for 1000 h. QPE-bl-9–TMA exhibited the highest retention of the conductivity (58%), which was higher than that of the Tokuyama A201 anion exchange membrane (29%). The post stability test IR analyses suggested that the major degradation mechanism of the QPE-bl-9 membranes in alkaline solution involved the decomposition of the ammonium groups. The QPE-bl-9 membranes retained their mechanical stability after the stability test, as proved by DMA analyses.
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IJS, KILJ, NUK, UL, UM, UPUK
Water management in alkaline fuel cells through the dew point optimization for a series of imidazolium-based graft-type anion exchange membranes (AEMs) consisting of an ethylene-tetrafuluoroethylene ...copolymer (ETFE) as a base film having three vinylimidazolium type and a styrylimidazolium type (StIm) anion-conducting units is compared with the standard vinylbenzyltrimethylammonium (BTMA)-based AEM. In the H2/O2 fuel cell tests at 60 °C, by optimizing dew points, the sterically hindered imidazolium containing StIm-based AEMs exhibited the highest power density (710 mW/cm2), which is one of the highest performances of imidazolium-type AEMs to date. Furthermore, it exhibited long-term durability in H2/O2 fuel cell at 60 °C, maintaining 0.52 V (56%) of initial voltage after 670 h of life time test, which is better than that of the standard BTMA-based AEM. The chemical characterization in post-durability characterization revealed that negligible degradation of conducting imidazolium groups in the 2MVIm-, 4VIm-, and StIm-based AEMs was observed. For the first time, the hydration level and DFT-based molecular calculations (LUMO energy) showed an acceptable correlation with the experimental in-situ durability results.
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•Effect of water management and graft-chain structure in alklaine fuel cell was investigated.•The optimized AEM (St-Im-based AEM) exhibited reasonable durability for 670 h and high power density of 710 mW/cm2 at 1389 mA/cm2.•Post-durability St-Im-based AEM revealed chemical stability.•Unprecedently, the in-situ durability results of AEMs were well-correlated with their hydration levels and DFT calculations (LUMO energy).
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The emergence of microgrids arises from the growing integration of Renewable Energy Resources (RES) and Energy Storage Systems (ESSs) into Distribution Networks (DNs). Effective integration, ...coordination, and control of Multiple Microgrids (MMGs) whereas navigating the complexities of energy transition within this context poses a significant challenge. The dynamic operation of MMGs is a challenge faced by the traditional distributed hierarchical control techniques. The application of Artificial Intelligence (AI) techniques is a promising way to improve the control and dynamic operation of MMGs in future smart DNs. In this paper, an innovative hybrid optimization technique that originates from Cheetah Optimization (CHO) and Particle Swarm Optimization (PSO) techniques is proposed, known as HYCHOPSO. Extensive benchmark testing validates HYCHOPSO's superiority over CHO and PSO in terms of convergence performance. The objective for this hybridization stems from the complementary strengths of CHO and PSO. CHO demonstrates rapid convergence in local search spaces, while PSO excels in global exploration. By combining these techniques, the aim is to leverage their respective advantages and enhance the algorithm's overall performance in addressing complex optimization problems. The contribution of this paper offering a unique approach to addressing optimization challenges in microgrid systems. Through a comprehensive comparative study, HYCHOPSO is evaluated against various metaheuristic optimization approaches, demonstrating superior performance, particularly in optimizing the design parameters of Proportional-Integral (PI) controllers for hierarchical control systems within microgrids. This contribution expands the repertoire of available optimization methodologies and offers practical solutions to critical challenges in microgrid optimization, enhancing the efficiency, reliability, and sustainability of microgrid operations. HYCHOPSO achieves its optimal score within fewer than 50 iterations, unlike CHO, GWO, PSO, Hybrid-GWO-PSO, and SSIA-PSO, which stabilize after around 200 iterations. Across various benchmark functions, HYCHOPSO consistently demonstrates the lowest mean values, attains scores closer to the optimal values of the benchmark functions, underscoring its robust convergence capabilities.the proposed HYCHOPSO algorithm, paired with a PI controller for distributed hierarchical control, minimizes errors and enhances system reliability during dynamic MMG operations. Using HYCHOPSO framework, an accurate power sharing, voltage/frequency stability, seamless grid-to-island transition, and smooth resynchronization are achieved. This enhances the real application's reliability, flexibility, scalability and robustness.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Water scarcity is a big challenge especially for developing countries and desert areas like Saudi Arabia. Using solar energy for freshwater production is the way forward for future development of the ...water industry. The present study developed a new composite sensible heat storage tubes (CSHSTs) to improve the freshwater productivity of a tubular solar still activated by a parabolic concentrator solar tracking system. 12-CSHSTs were inserted inside the trough of the tubular solar still forming heterogeneous cavities for the saline water. Each CSHST consists of three main solid components (black painted aluminum tube, copper wire and silica sand). The experimental work was conducted under the climatic conditions of Ha'il city in Saudi Arabia. Results showed enhancements by 24.05% and 20.06% in the freshwater yield and thermal daily efficiency, respectively. The developed device produced 4.9 L/m2day with 13% lower freshwater production cost of $0.0087 per liter. Inserting the 12-CSHSTs inside the trough with the heterogeneous cavities increased the contact area with the saline water. This novel configuration enhanced significantly the heat transfer mechanism. The developed device showed higher performance compared to the previous studies in the literature.
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•Novel composite sensible heat storage tubes are proposed for tubular solar stills.•Proposed device enhances freshwater productivity and efficiency by 24.1% and 20.1%.•Proposed device was able to produce 4.9 L/m2day of freshwater with $0.0087 CPL.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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