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Determination of the oxidation depths of ground granulated blast furnace slag containing cement pastes using Mn K edge X ray absorption near edge structure spectroscopy
No full textThe redox potential of the pore solution of hardened cements containing ground granulated blast furnace slag GGBFS affects reinforcement corrosion and immobilization of radioactive waste. Here, Mn K edge X ray absorption near edge structure XANES spectroscopy was applied to determine the depth profile of the oxidation state of manganese in hardened GGBFS containing cement pastes. Manganese was oxidized in the outer regions of some of the pastes, but the depth to which this occurred was not identical with the blue green white color change front , usually interpreted as indicating oxidation of sulfur species. For CEM III B, the color change of the material was gradual and thus unsuitable for a precise determination of the oxidation depth, while for the alkali activated slag, a distinct color change front was found, but full oxidation of manganese and sulfur had not occurred in the brighter region. Mn K edge XANES spectroscopy is thus a more reliable method than the determination of the visual color change front to follow the ingress of the oxidation fron
Pyrene Based Self Assembled Monolayer with Improved Surface Coverage and Energy Level Alignment for Perovskite Solar Cells
No full textRecently, the efficiency of p i n perovskite solar cells drastically increased, a pivotal factor being the incorporation of self assembled monolayers SAMs as a hole transporting layer HTL . SAMs offer many advantages over conventional HTLs, including minimal material requirements, low cost, and facile processing. Current research is mainly focused on the development of carbazole derived SAMs. However, the versatility of organic chemistry allows for the design of SAMs with alternative organic cores that may possess specific benefits. In this study, three novel SAMs are incorporated in p i n perovskite solar cells, each based on an aromatic core commonly used in organic semiconductors. The novel SAMs vary in their energy level alignment with the perovskite active layer. Optimal alignment is achieved with a pyrene based SAM 4PAPyr , resulting in solar cells that outperform the commercially available 2PACz. Moreover, due to improved surface coverage, the use of 4PAPyr leads to a significantly higher number of working solar cell devices when compared to 2PACz, which is of particular interest with regard to upscaling. After device optimization, a power conversion efficiency of 22.2 is achieved with 4PAPyr. This research underlines the importance of diversifying SAMs to unlock further advancements in perovskite solar cell efficiency and scalabilit
Dynamic magnetic ground state in the dimer based compound Yb2Te5O13
No full textWe report the discovery of a dynamic magnetic ground state in the Yb3 dimer based compound Yb2 amp; 8290;Te5 amp; 8290;O13 through various characterization techniques down to sub Kelvin temperatures. Magnetization measurements reveal the absence of long range magnetic ordering down to 0.4 K and the onset of magnetic correlations below 1 K. Heat capacity data, measured down to 0.37 K, indicate a small finite energy gap in zero field, amp; 916; amp; 8289; 0 amp; 8764; 0.55 K, and validate the presence of magnetic correlations with a Kramers doublet ground state amp; 119869;eff 1 2 . Further insight is provided by zero field muon spin relaxation amp; 120583; amp; 8290;SR measurements, which show a gradual slowdown of Yb3 spin fluctuations below 30 K, indicating a dynamic state down to 44 mK. The temperature dependence of the relaxation rate, amp; 120582;, confirms the presence of the Orbach process, which is mediated through various crystal electric field levels, complementing the amp; 119869;eff 1 2 ground state. Furthermore, longitudinal field amp; 120583; amp; 8290;SR measurements performed at 70 mK demonstrate that the Yb3 spins remain dynamic even under an external field of 3200 Oe, with fluctuations becoming stronger with increasing magnetic field. Theoretical investigations further support the dynamic state, revealing competition between intra and interdimer exchange interactions as the underlying cause. By integrating macroscopic and microscopic measurements with theoretical insights, we propose Yb2 amp; 8290;Te5 amp; 8290;O13 as a quantum spin liquid candidate, opening avenues for research in quantum magnetis
Nanosized Li2S Loaded Polar Porous Carbon Nanofibers as Self Supporting Electrodes in Anode Free Lithium Sulfur Batteries
No full textAnode free lithium sulfur Li S batteries with Li2 S as the cathode o amp; 64256;er a promising alternative to improve practical energy density but su amp; 64256;er from sluggish redox kinetics on the cathode side and chaotic Li plating stripping process on the copper current collectors. In this work, phosphorus doped porous carbon nano amp; 64257;bers P CNFs are served both as self standing hosts for Li 2 S cathode and 3D current collectors for Li deposition. In the cathode, nanoscale Li 2 S particles less than 10 nm in size are in situ synthesized via carbon thermal reduction of lithium sulfate which is con amp; 64257;ned within the brush layer of anionic spherical polyelectrolyte brushes. The incorporation of Li2 S nanoparticles within the void of P CNFs Li 2 S P CNFs imparts unimpeded electron ion transport at the polar carbon matrix interface, thus enhancing the Li 2 S conversion reaction kinetics and mitigating the shuttling e amp; 64256;ect of polysul amp; 64257;des during cycling. Moreover, the lithiophilic P CNFs skeleton with interconnected macropores e amp; 64256;ectively homogenizes Li plating behavior, resulting in smooth and compact deposition morphology. As a result, the Li 2 S P CNFs P CNFs full cell delivers a low capacity decay of 0.051 cycle amp; 8722;1 for 1000 cycles at 1 C. This work gives a unique strategy for the practicalization of anode free Li S batteries, with the potential to extend to other battery system
Enhancing CoFe Catalysts with V2CTX MXene Derived Materials for Anion Exchange Membrane Electrolyzers
No full textHerein, the synthesis and characterization of Co0.66Fe0.34 layered double hydroxides LDH derived from pure and vacancy engineered V2CTx MXenes and their use as electrocatalysts for the oxygen evolution reaction OER is reported. Two distinct MXene materials are investigated pristine V2CTx and V1.8CTx containing 10 vanadium vacancies. Through systematic variation of the MXene content 17 75 wt. , it demonstrates that the utilization of MXenes significantly enhances OER activity compared to pure Co0.66Fe0.34. The vacancy engineered composite Co0.66Fe0.34 V1.8CTx achieved superior performance with an overpotential of 304 mV at 10 mA cm 2 CFVv75 , compared to 317 mV for the best performing V2CTx MXene composite CFV33 . In situ X Ray absorption spectroscopy revealed the formation of highly oxidized Co i.e., Co III and Co IV species during OER, while also indicating irreversible oxidation of vanadium to V V . Despite partial vanadium leaching, both materials demonstrated excellent stability over 12 h of operation at 100 mA cm 2. Notably, CFVv75 showed superior initial performance under practical anion exchange membrane electrolyzer conditions, operating at cell voltages of 100 mV lower than the pure Co0.66Fe0.34. This work demonstrates the potential of vacancy engineering and materials discovery using MXene materials for enhancing electrocatalytic performance and provides insights into the dynamic evolution of these materials under operating condition
Highly Active IrRuOx MnOx Electrocatalysts with Ultralow Anode PGM Demand in Proton Exchange Membrane Electrolyzers
No full textThrifting the rare iridium in proton exchange membrane water electrolyzer PEMWE anodes is an effective means to preempt undesired future iridium supply shortages aiding wider deployment of PEMWEs in coming years. This work explores a new family of MnOx supported IrOx and IrRuOx electrocatalysts for the acidic oxygen evolution reaction OER . Comprehensive ex situ and in situ characterization uncovers synthesis structure activity relationships of the OER materials with insight into the origin of their exceptional activity The MnOx support provides beneficial dispersion while the introduction of Ru into IrOx MnOx leads to a modulation of the chemical state of Ir coupled with a strong surface reconstruction. In half cell tests, IrRuOx MnOx reveals an Ir mass activity of 964.7 A gIr amp; 8722;1 at 1.53 VRHE, which is 36 times higher than that of the commercial IrO2 C IrO2 . It is also demonstrated that this promising catalytic OER activity translates into a realistic PEMWE performance. IrRuOx MnOx and IrOx MnOx thin catalyst layers are developed in low Ir loaded membrane electrode assemblies MEAs and an outstanding PEMWE cell performance is reported with cell voltages of 1.66 V at 2 A cm amp; 8722;2. This translates into a favorable Ir Ru platium group metal PGM demand of lt;0.05 gPGM kW amp; 8722;1 at 70 voltage efficiency, meeting a 2035 technical demand targe
Structural and functional characterization of the newly identified Photorhabdus laumondii tumor necrosis factor like lectin
No full textPhotorhabdus bacteria live in mutualistic relationships with Heterorhabditis nematodes, and together, they act as effective insect pathogens. These bacteria produce a diverse array of lectins, sugar binding proteins that are believed to play crucial roles in the complex tripartite interaction among Photorhabdus, nematodes, and their insect hosts. One such lectin, Photorhabdus laumondii tumor necrosis factor TNF like lectin PLTL , identified in Photorhabdus laumondii subsp. laumondii TTO1, exhibits notable sequence similarity to the N terminal domain of the BC2L C lectin BC2L CN , a TNF like lectin recognized for its specificity toward fucosylated glycans associated with human embryonic stem cells and certain cancers. Through glycan array analysis and surface plasmon resonance, we identified PLTL s binding preference for branched histo blood group oligosaccharides. The crystallographic structure of PLTL in complex with the BLeb pentasaccharide reveals a network of direct and water mediated hydrogen bonds simultaneously stabilizing the Fuc amp; 945;1 2 and Gal amp; 945;1 3 moieties, which define its narrow glycan specificity. A combination of mass spectrometry, protein crystallography, and analytical ultracentrifugation showed a unique hexameric PLTL architecture stabilized by intermolecular disulfide bridges. Our data suggest that PLTL may contribute to the mutualistic relationship between Photorhabdus and its nematode symbiont, Heterorhabditis bacteriophora, rather than playing a role in the interaction with the insect host. This study provides a structural and functional characterization of PLTL, a newly identified member of the TNF like lectin family. Comparative analysis with BC2L CN highlights both conserved and distinct structural features, suggesting potential applications in glycan recognition based diagnostics or biotechnological tools beyond its biological role. Our findings underscore its complex glycan specificity and offer insights into its potential role in Photorhabdus nematode symbiosi
Detection of polycyclic aromatic hydrocarbons, microplastic presence and characterization of microbial communities in the soil of touristic zones at Alqueva s edges Alentejo, Portugal
No full textEnvironmental pollution is a growing concern. Here, we assessed the occurrence of two groups of persistent organic pollutants POPs polycyclic aromatic hydrocarbons PAHs and microplastics MPs and bacterial populations in the topsoil of three tourist spots located at the Alqueva s edges during 1 year, once per season. Soil chemical analysis revealed low content of total organic carbon, pH close to neutrality, and nitrogen and phosphorus levels consistent with acquisition of these nutrients only by atmospheric deposition. PAH s concentrations were in the range of ng kg, being significantly below the reference values for contaminated soils. Nevertheless, potentially carcinogenic PAHs, detected at all locations, raise ecotoxicological concerns. Polyamide, polyester, polystyrene, and styrene acrylonitrile resin MPs were found. Six bacterial phyla constitute the core microbiome in the three locations and include genera of bacteria reported as plastic degraders, such as Bacillus, Exiguobacterium, Paenibacillus, and Pseudomonas. The presence of POPs, even at low levels, in the soil at the edges of a water reservoir should be monitored. The identification of bacteria reported as plastic degraders in the soil, and previously in the water, is promising, and their ability to spontaneously ensure the detoxification of the ecosystem should be further investigate
The role of terminal functional groups in molecular passivation of the perovskite hole selective layer interface
No full textThe objective of this study is to investigate how terminal functional groups in passivating agents influence the optoelectronic properties and photovoltaic performance of perovskite solar cells. Engineering the perovskite hole selective layer interface is critical for effective defect passivation, reduced interfacial recombination, improved charge extraction, optimized energy level alignment, and overall enhancement of device performance. While various molecular strategies have been proposed, the role of specific functional groups in passivating interfacial defects remains poorly understood. Here, a comparative investigation is conducted on three molecules with identical five carbon backbones but distinct functionalities ammonium n pentylammonium iodide , carboxylic acid valeric acid , and a bifunctional ammonium carboxylic acid 5 ammonium valeric acid iodide as passivating agents in perovskite hole selective layer interface. Optoelectronic characterization studies including photoluminescence, surface photovoltage, and conductive atomic force microscopy reveal distinct functional group dependent variations in trap passivation, carrier dynamics, and interfacial conductivity. Devices based on surfacetreated perovskites with single functional group agents exhibit improved open circuit voltage VOC and fill factor FF , confirming efficient trap suppression and charge extraction. In contrast, the bifunctional molecule, despite effective trap passivation, limits the hole extraction. This work highlights the critical role of molecular functionality in determining interfacial interactions and charge transfer, offering a strategic pathway for interface engineering in perovskite photovoltaic
Influence of contour parameters on the surface roughness of fine channels produced by powder bed fusion laser beam
Full text linkSurface roughness strongly influences the performance of fine internal channels in additively manufactured components. This study investigates how contour process parameters affect the surface finish of 1 mm diameter channels produced by powder bed fusion laser beam PBF LB . Five contour parameter sets with progressively increasing laser energy density LED were applied, while keeping infill parameters constant. Surface roughness was evaluated using surface profilometry, X ray computed tomography XCT , and optical microscopy OM . Profilometry and OM provided localized measurements, whereas XCT captured full channel roughness along the build direction. Results show that increasing LED initially reduces surface roughness due to improved melting and removal of partially fused particles, reaching optimal smoothness at an intermediate LED. Further LED increase causes roughness to rise again, attributed to balling and dross formation. Optical cross sections depicted these trends, and XCT measurements closely matched profilometry data. The findings in this study highlight a trade off between surface quality and dimensional accuracy, as higher LEDs improve smoothness but reduce channel diameter. This work establishes an optimal contour LED range for minimizing as built surface roughness in fine internal channels, which can enhance the functional performance of PBF LB components in aerospace, medical, and energy application