Search Results (1,380)

Ammonia is a cornerstone chemical for global food security and an emerging carbon-free energy carrier, yet its industrial synthesis via the Haber–Bosch process remains energy-intensive and carbon-emitting. Non-thermal plasma catalysis offers a promising decentralized alternative for nitrogen fixation under milder conditions, though the long-term structural stability of supported metal catalysts under harsh plasma environments remains a key open challenge. Plasma-assisted NH₃ synthesis was investigated using exsolution-derived Co-La₂O₃/Al₂O₃ and Ni-La₂O₃/Al₂O₃ catalysts in a pulsed (1 kHz at 50% duty cycle) microwave reactor operating at sub-atmospheric pressure (2–6 Torr) and 2.45 GHz. The catalysts were prepared by reductive H₂ treatment of LaCoO₃ and LaNiO₃ perovskite precursors, deposited onto Al₂O₃ pellets, triggering metal exsolution and generating metallic Co⁰ and Ni⁰ nanoparticles embedded within a La₂O₃/Al₂O₃ matrix. Catalytic performance was evaluated across a range of H₂/N₂ flow rates (200–400 cm³/min each) and microwave power inputs (0.6–0.7 kW average), using bare Al₂O₃ as a reference. Co-La₂O₃/Al₂O₃ outperformed both Ni-La₂O₃/Al₂O₃ and the Al₂O₃ reference under all tested conditions, reaching a maximum H₂ conversion of 2.39% and a peak productivity of 20.6 μmol/g_cata.h, attributed to the finer metal dispersion and smaller nanoparticle size achieved during Co exsolution from the LaCoO₃ lattice. Post-reaction characterization by TEM, XRD and N₂ physisorption confirmed the structural integrity of both spent catalysts. No bulk phase transformations were detected by XRD, while specific surface areas were retained above 93% of the initial one. Metals’ particle size slightly increased after plasma exposure, confirming the structural durability of catalysts. These results demonstrate that the exsolution mechanism confers meaningful sintering resistance under microwave plasma conditions, establishing exsolution-derived perovskite catalysts as a promising and durable platform for plasma-assisted nitrogen fixation. Full article

Owing to its favorable physical and chemical characteristics, zinc oxide (ZnO) has become one of the most extensively investigated metal oxide semiconductors. Pulsed laser irradiation in liquids provides a post-synthesis route for modifying ZnO nanostructures. However, correlating laser parameters with the systematic evolution of particle morphology, size distribution, and surface chemistry remains challenging. In this work, a facile and additive-free pulsed laser irradiation approach was employed to engineer the morphology and surface chemical composition of ZnO nanoparticles. As-prepared hydrothermally synthesized ZnO nanorods dispersed in deionized water were irradiated with a Q-switched Nd:YAG laser for 30 and 90 min and compared against the untreated powder. TEM and SEM analyses revealed a progressive morphological transformation in which the strongly agglomerated, faceted nanorods partially reshape into a mixed rod and particle morphology after 30 min and evolve into well-dispersed, nearly spherical nanoparticles with diameters of approximately 12–48 nm after 90 min. XRD confirmed that the hexagonal wurtzite structure is retained throughout the treatment with no secondary or impurity phases, while the mean crystallite size increases from 15.14 nm for the powder to 18.80 nm after 90 min of irradiation as a result of photothermal fusion. XPS demonstrated that zinc preserves its +2 oxidation state during laser processing, whereas the surface O/Zn ratio and the relative fractions of lattice oxygen and hydroxyl species evolve systematically with irradiation time, revealing a concurrent modification of the surface chemistry. These results establish the laser post-irradiation duration as a simple and effective control parameter for tailoring both the morphology and surface chemical state of ZnO nanostructures. Full article

This work presents a conditional deep convolutional generative adversarial network (CDCGAN) for the inverse design of high-absorptance periodic metasurfaces (MSs) with different geometries. The conditioning mechanism encodes geometric and spectral parameters. A key innovation is the inclusion of unit cells with different periods to produce fine-tuned responses within the W-band. The period is embedded in the fringe pixels before training and recovered from generated high-resolution images to reconstruct the unit cell. This joint topology–period representation allows both the metallic geometry and lattice scale to be recovered from a single generative output without requiring a separate period-optimization stage. The resulting spectra closely matched the targets when tested at three angles of incidence, thereby demonstrating the method’s effectiveness for high-performance MS design. Full article

For supported catalysts, the interaction between metal active components and the support plays a crucial role in modifying catalyst properties, such as active sites and oxygen vacancies. Herein, a series of CoMnO_x/SBA-15 (Santa Barbara Amorphous-15) catalysts were prepared for catalytic oxidation of toluene, in which the support properties were tailored by varying the hydrothermal crystallization time. The results revealed that subtle changes in support properties could lead to modifications of the supported active component. CM-48 (crystallization time of 48 h) exhibited the optimal low-temperature activity with T₉₀ of 234 °C and good stability for the catalytic oxidation of toluene. The improved performance was attributed to the enhancement of redox properties, abundant oxygen vacancies, and high mobility of lattice oxygen species resulting from the strong interaction between the active components and the support. Furthermore, the reaction mechanism was explored via in situ DRIFTS (Diffuse Reflectance Infrared Fourier Transform Spectroscopy), confirming that both surface-adsorbed oxygen and lattice oxygen served as active oxygen species participating in toluene oxidation, with surface-adsorbed oxygen being particularly favorable for the consumption of key intermediates. This work will guide the design of supported catalysts in practical applications for eliminating VOCs. Full article

We review recent calculations and numerical simulations showing the formation of coherent states of protons in hydrogen-loaded metals with a cubic crystal lattice. The characteristic frequencies discussed here are the local proton frequency, the plasma frequency, and the resonant confined electromagnetic frequency; depending on the adopted parameters, they are of order ${10}^{13}$–${10}^{14}\mathrm{Hz}$. They are far from the much higher frequency corresponding to the full electron-capture energy transfer. In these states protons oscillate coherently and in a fixed phase relation with a strong high-frequency electric field which is trapped in the material, especially if the material is made of micro-powders. The energy gap of the coherent ground state is estimated to be well above thermal energies, of the order of a fraction of an eV per particle, and therefore large enough to make the state robust against thermal fluctuations. The analytical calculations address the realistic case of a large number of protons, in the rotating-wave approximation. The numerical calculations are presently limited to a small number of protons but go beyond the rotating-wave approximation and allow one to take into account a dissipation term associated with the strong oscillating electric field. The next task of this theoretical model is to compute the excited states of the coherent system. A simplified interacting-qubit model gives evidence of collective transition energies larger than the single-oscillator spacing. It does not yet establish whether a realistic external pump can populate such collective excited states with appreciable probability, nor the overall pump-to-capture conversion efficiency in a realistic proton lattice. If suitable states can be populated, their de-excitation could make some electron-capture processes energetically possible, with generation of slow neutrons. This dynamical mechanism offers an alternative to the Widom–Larsen hypothesis of “heavy electrons”, and is closer to current models in mainstream physics. The consequences, in terms of nuclear transmutations, of neutron generation via electron capture would be similar to those already known in the literature. Full article

Fabricating nanoscale metal–organic frameworks (MOFs) with hierarchical pores is an effective strategy to engineer high-performance adsorbents. Herein, hierarchically porous NH₂-MIL-53(Al) nanorods were synthesized through a straightforward one-pot solvothermal approach, featuring inherently interconnected micro-/mesoporous with an average pore width of 19.51 nm and abundant amino-functionalized active sites. Toward the anionic Direct Scarlet dye, the material delivers a Langmuir maximum adsorption capacity of 694.99 mg·g⁻¹, with its adsorption kinetics and isotherms well described by the pseudo-second-order kinetics and Langmuir isotherm model. Combined spectroscopic, thermodynamic, and diffusion analyses suggest monolayer electrostatic chemisorption between protonated –NH₃⁺ and dye sulfonate groups. The material exhibits favorable reusability, retaining over 85% of its original dye removal efficiency after five adsorption–desorption cycles, and PXRD and SEM results verify well-preserved morphology and crystalline lattice. This work clarifies the intrinsic correlation between structure and adsorption performance of NH₂-MIL-53(Al), offering a facile nanoscale pore-tuning strategy for the design and fabrication of high-performance MOF adsorbents. Full article

Helium accumulation is a major contributor to swelling, gas release, and mechanical degradation in oxide nuclear fuels under irradiation. This study employs first-principles density functional theory (DFT) to investigate helium behavior in thorium-based mixed oxide (MOX) fuels. A series of (Th_1−xPu_x)O₂ and (Th_1−xU_x)O₂ solid solutions (x = 0, 0.25, 0.5, 0.75, and 1) was constructed, and the corresponding ground-state configurations were determined through total-energy minimization. The effects of 4.167 at.% helium incorporation on structural stability, electronic structure, elastic response, and thermal expansion were evaluated. Helium migration in ThO₂, PuO₂, and UO₂ was further investigated at octahedral interstitial, metal-vacancy, and oxygen-vacancy sites. Positive helium incorporation energies indicated that helium incorporation is energetically unfavorable for all compositions. Vegard-like behavior was preserved for lattice constants and metal–oxygen bond lengths. The 2.06 eV band gap of UO₂ disappeared after helium incorporation, whereas band-gap variations in most MOX compositions remained below 0.7 eV. Helium reduced the bulk moduli of (Th_0.75U_0.25)O₂ and UO₂ by 3.75% and 7.94%, respectively. Thermal expansion coefficients followed the order α_L-UO2 > α_L-PuO2 > α_L-ThO2, with α_L of UO₂ nearly doubling. Metal vacancies acted as helium traps, whereas adjacent oxygen vacancies provided the lowest migration barrier of 0.42 eV. These results indicate that increasing ThO₂ content improves the resistance of MOX fuels to helium-induced degradation. Full article

Lattice strain engineering, rooted in symmetry-breaking lattice distortion, is an effective strategy for modulating the electronic structure and catalytic performance of electrocatalysts. Herein, non-noble metal CuCoNiCrMo_x high-entropy carbides with tunable Mo content (HEC_Mo-x) were rapidly synthesized within seconds via a high-temperature shock method. By leveraging composition-dependent lattice distortion engineering to deliberately break local translational symmetry, these catalysts were developed to optimize the alkaline hydrogen evolution reaction (HER). Density functional theory calculations reveal that lattice distortion optimizes the d-band center and regulates the electronic configuration. Concurrently, kinetic isotope effect tests and variable-potential electrochemical impedance spectroscopy measurements verify that this modulation balances the reaction kinetics of water dissociation and hydrogen adsorption, thereby accelerating the alkaline HER process. Consequently, the optimized HEC_Mo-15% electrocatalyst exhibits outstanding activity, requiring an overpotential of only 34 mV at 10 mA cm⁻². Furthermore, it exposes abundant active sites and maintains long-term operational stability with negligible attenuation over 23 h. This work provides a feasible design strategy and a practical paradigm for developing non-noble metal high-entropy carbides as highly efficient electrocatalysts for energy conversion applications. Full article

For hydrogen refueling stations, metal hydride compressors offer a safe and efficient alternative to mechanical systems. This work systematically investigates Ti_0.94Zr_0.08Cr_1.0Mn_0.6−xFe_0.4+x (x = 0, 0.1, 0.2, 0.3, 0.4) alloys for primary hydrogen compression targeting 25 MPa. All alloys crystallize as a single C14 Laves phase, with Fe substitution causing negligible lattice changes but leading to linearly increased particle size due to solid-solution strengthening. In the testing temperature range of −80 to −50 °C, the hydrogen storage capacity decreases with increasing Fe, whereas the effective desorption capacity improves. Pressure–composition isotherms exhibit single plateaus with elevated plateau pressures at higher Fe/Mn ratios. In the range of x = 0–0.4, the enthalpy of desorption decreases in magnitude with Fe content. Using Van’t Hoff extrapolations to 30 °C absorption and 80 °C desorption, the compression factor shows a non-monotonic trend, reaching a maximum of 1.99 at x = 0.2. This composition provides nearly a two-fold pressure boost, demonstrating promise for low-grade heat driven hydrogen compression in refueling infrastructure. Full article

The electrocatalytic nitrogen reduction reaction (NRR) is a key approach for synthesizing green ammonia under mild conditions. However, the high bond energy of the N≡N triple bond makes N₂ difficult to activate, limiting the Faradaic efficiency. MoS₂ offers advantages such as low cost and abundant reserves as a non-precious-metal NRR electrocatalyst. Nevertheless, pure MoS₂ suffers from insufficient conductivity and a limited number of active sites, resulting in suboptimal catalytic performance. Herein, we develop a solvent-regulated one-step hydrothermal strategy using ethylene glycol as the sole reaction medium to fabricate an oxygen-substituted amorphous MoS₂ (O-MoS₂) electrocatalyst. XRD, SEM, and HRTEM characterization revealed that, as the ethylene glycol ratio increased, the product gradually transformed from a layered crystalline structure to a completely amorphous structure. XPS confirmed that oxygen atoms were uniformly incorporated into the MoS₂ lattice via substitution doping. Electrochemical testing showed that O-MoS₂ achieved an ammonia yield of 97.16 μg h⁻¹ mg⁻¹ and a Faradaic efficiency of 46.44% in a 0.1 M Na₂SO₄ electrolyte at −0.70 V vs. RHE, significantly outperforming undoped MoS₂ and semi-doped S-MoS₂. DFT calculations indicate that O doping reduces the N₂ adsorption energy, thereby synergistically promoting N₂ adsorption and activation. This dual-modification strategy provides a facile and universal guidance for electronic structure regulation of MoS₂-based catalysts and sheds new light on the design of high-efficiency ambient nitrogen fixation electrocatalysts toward practical green ammonia synthesis. Full article

Increasing power densities in electronic systems require efficient passive thermal-management solutions. This study numerically compares five DMLS-compatible AlSi10Mg heat-sink architectures: perforated planar-fin, curved radial-fin, Schwarz P, BCC diamond and gyroid designs. Conjugate heat-transfer simulations incorporating conduction, natural convection and surface radiation were performed under an identical 18 W thermal load. Performance was evaluated using surface temperature, thermal resistance, temperature uniformity and convective–radiative heat dissipation. The gyroid achieved the lowest average surface temperature (82.02 °C) and combined thermal resistance (3.30 °C W⁻¹), whereas the BCC diamond provided the greatest temperature uniformity (UI = 0.035). Radiation contributed 46–73% of total heat dissipation and was highest for the gyroid architecture. The results demonstrate that increased surface area alone does not ensure improved passive cooling; thermal performance depends on the coupled effects of topology, airflow accessibility and radiative heat exchange. Gyroid TPMS architectures therefore provide a promising DMLS-compatible approach for passive thermal management. Full article

Assembling aromatic icosahedral superatoms into 2D lattices offers a promising route to function-oriented boron-based materials. Using first-principles calculations, we embed ${{\mathrm{B}}_{12}\mathrm{H}}_{12}^{2-}$ and its isoelectronic carbon-substituted analog B₁₀C₂H₁₂ into a checkerboard framework, yielding two novel monolayers, o-B₁₂H₈ and o-B₁₀C₂H₆. Both exhibit excellent kinetic, thermal, and mechanical stability, along with pronounced mechanical anisotropy and near-zero Poisson’s ratio. Electronic structure calculations reveal wide bandgaps of 4.75 and 4.63 eV, respectively. Remarkably, o-B₁₀C₂H₆ achieves high carrier mobilities—up to 8440 cm²V⁻¹s⁻¹ for electrons and 8590 cm²V⁻¹s⁻¹ for holes—with strong anisotropy. Moreover, both materials show low migration barriers for alkali metal ions, highlighting their potential as ion conductors or electrode interfaces. This work establishes a novel design paradigm that constructs 2D checkerboard lattices from B₁₂ and B₁₀C₂ superatom building blocks, laying a robust theoretical groundwork for subsequent investigations in this field. Full article

To investigate the effect of femtosecond laser scanning path on the surface integrity of 7075 aluminum alloy after paint removal, parallel, Z-shape, and loop-shape scanning were compared in terms of surface morphology, microstructure, chemical composition, roughness, wettability, and corrosion resistance. Parallel scanning effectively removed the paint while maintaining a surface roughness of 0.27 μm, close to that of the original substrate. The resulting regular unidirectional laser-induced periodic surface structures (LIPSS) yielded a water contact angle of 85°, consistent with the Wenzel wetting model. X-ray photoelectron spectroscopy (XPS) showed the lowest C 1s and O 1s peak intensities, the lowest lattice-oxygen fraction in Al₂O₃, the strongest metallic Al⁰ signal, and limited thermal oxidation. Electrochemical measurements showed the most positive corrosion potential (−0.974 V), the highest film resistance and charge-transfer resistance, and the best corrosion resistance for parallel scanning. By contrast, energy accumulation at the ends during Z-shape scanning and thermal accumulation at the corners and center during loop-shape scanning increased pit and recast-defect densities, oxidation, and corrosion degradation. Loop-shape scanning produced a surface roughness of 3.60 μm and a contact angle of 140.7°, indicating superhydrophobicity, but also the highest corrosion current density and the poorest corrosion resistance, showing that superhydrophobicity does not necessarily correspond to high corrosion resistance. The results show that scanning path affects LIPSS evolution, oxide-film integrity, and corrosion resistance through the spatial distribution of laser energy and thermal accumulation. Among the three paths, parallel scanning provided the best combination of paint removal, low substrate damage, and corrosion resistance, supporting its use in femtosecond-laser paint removal from aircraft aluminum alloy skins. Full article

The oxygen reduction reaction (ORR) remains a major kinetic bottleneck in fuel cells, metal-air batteries, and related electrochemical devices. Perovskite oxides are attractive ORR catalysts due to the ABO₃ lattice, which permits systematic control of transition-metal electronic structure, metal–oxygen covalency, and defect chemistry. This review compares low-temperature electrocatalytic ORR, including the 2e⁻ and 4e⁻ pathways, with high-temperature cathodic ORR in mixed ionic–electronic conductors, where oxygen adsorption, charge transfer, O=O bond cleavage, oxygen incorporation, and bulk transport are interlinked. The main optimization strategies, including A-site and B-site doping, defect engineering, nanostructuring, heterostructure/composite formation, and mechanisms, are discussed. Particular attention is given to the distinct requirements of fuel cells and metal-air batteries. Across these systems, perovskite ORR performance is governed by the joint evolution of surface chemistry, defect structure, and electrode architecture under operating conditions. Full article

Fe^II-doped zinc ferrite nanocrystals (Fe^II_xZn_1-xFe^III₂O₄) were prepared via a sol–gel approach in the presence of polyvinyl alcohol as a stabilizer and assessed for their capability to eliminate crystal violet (CV) dye from water-based solutions. The structural and surface characteristics of the prepared materials were examined by XRD, HRTEM, FESEM, ATR–FTIR, XPS, UV–visible spectrophotometer and BET analyses. XRD patterns confirmed the formation of a cubic spinel ferrite structure (Fd-3m), indicating successful incorporation of Fe^II into the ZnFe₂O₄ lattice. ATR–FTIR spectra showed characteristic metal–oxygen vibrations at the tetrahedral and octahedral sites. XPS analysis confirmed the coexistence of Fe^II and Fe^III species, which may promote interfacial charge transfer and redox reactions. HRTEM and FESEM images showed particle agglomeration and grain growth after calcination at 700 °C. Fe^II_0.2Zn_0.8Fe^III₂O₄ exhibited the highest photocatalytic performance, achieving 97.2% degradation of CV under optimized conditions. The effects of contact time, catalyst dosage, initial dye concentration, and pH were systematically studied. The maximum removal efficiency was obtained at pH 10 using 0.075 g catalyst for 20 mg L⁻¹ CV solution within 40 min. Freundlich isotherm models exhibited the strongest correlation (R² = 0.918), pointing to multilayer adsorption occurring across a non-uniform nanoparticle surface. The Dubinin–Radushkevich analysis returned an adsorption energy of 3.01 kJ mol⁻¹, implying that physical forces predominantly control the adsorption mechanism. Kinetic investigations revealed a two-stage CV uptake pathway: fast initial binding at exterior surface sites, succeeded by a slower migration of dye molecules into the internal pores of the adsorbent. Full article