Search Results (873)

Electrocatalytic glycerol oxidation to formic acid (FA) offers a sustainable route for biomass valorization, yet non-noble metal catalysts generally suffer from sluggish C-C bond cleavage and poor product selectivity. Here we report an amorphous nickel–cobalt oxyhydroxide bearing both metal and oxygen vacancies (D-NiCoO_xH_y-V_Cr,O), grown on nickel foam via one-step electrodeposition followed by electrochemical activation with Cr doping. The coexistence of the dual vacancies is experimentally confirmed by X-ray photoelectron spectroscopy (XPS), which reveals elevated Ni³⁺/Co³⁺ ratios and reduced lattice oxygen, and by electron paramagnetic resonance (EPR), which shows a markedly enhanced signal at g = 2.003. Building on prior Cr-leaching approaches in single-metal nickel oxides, this work extends dual-vacancy engineering to an amorphous bimetallic NiCo oxyhydroxide and correlates the defect structure with glycerol-induced interfacial responses, charge-transfer behavior, and product selectivity. The catalyst delivers 200 mA cm⁻² at 1.31 V vs. RHE and achieves 100% Faradaic efficiency for formate at 1.32 V vs. RHE. In situ electrochemical impedance spectroscopy further reveals a significantly reduced charge-transfer resistance. These results establish Cr-assisted dual-vacancy engineering in amorphous bimetallic oxyhydroxides as a promising strategy for selective biomass electrooxidation. Full article

Two-dimensional transition metal dichalcogenides (TMDCs) require highly controllable and scalable synthesis methods for successful integration into next-generation optoelectronic technologies. This study presents a modified two-step thermally assisted conversion approach for synthesizing 2D tungsten diselenide (WSe₂) by introducing an intermediate UV–ozone treatment. Magnetron-sputtered tungsten films are exposed to UV–ozone, converting the precursor into a uniform, dense layer of amorphous tungsten trioxide (WO₃) prior to the selenization process via chemical vapor deposition. X-ray photoelectron spectroscopy and Raman spectroscopy confirm the complete phase transition from the oxidized precursor to the 2H-WSe₂ crystal lattice. Morphological evaluations utilizing transmission electron microscopy and atomic force microscopy demonstrate that the ozonated precursors yield highly uniform, triangular flakes exceeding 5 µm in lateral size, effectively eliminating the unreacted WO₃ phases observed in untreated samples. Furthermore, the intermediate oxidation step finetunes the electronic band structure; the resulting WSe₂ exhibits an enhanced p-type character with a valence band maximum shift to 0.35 eV, a tuning attributed to residual oxygen doping. Optical characterizations reveal significantly improved transmittance in the visible spectrum, accompanied by excitonic absorption shifts indicative of reduced layer dimensionality. This intermediate ozonation strategy provides a highly effective pathway for producing high-quality WSe₂ nanosheets with tailored structural and optoelectronic properties. Full article

The Ising model provides a fundamental setting for investigating the emergence of phase transitions from simple interacting degrees of freedom. The current characterization study serves to investigate central requirements for phase transitions in terms of connectivity, i.e., the degree of coupled interactions between interaction sites. The impact of increasing connectivity between 1D-Ising chains mapped onto 2D-lattices with free boundary conditions were studied systematically, using exact free energy calculations. Starting from a reference system of non-interacting 1D-chains, interaction bonds between chains are introduced successively until the fully connected $N\times N$-lattice is obtained. Two distinct construction schemes are analyzed, which differ in the connectivity of the intermediate partially coupled systems. The resulting free energies of the graphs along these paths are evaluated and compared with respect to their convergence behavior as a function of system size. We find that, despite topological differences between the schemes, strikingly, they converge to the same limiting straight line for increasing N when analyzed in terms of residual free energy differences. These findings provide insight into the relationship between interaction structure and thermodynamic behavior and suggest that appropriately chosen construction paths may serve as a basis for efficient extrapolation strategies toward the thermodynamic limit. Full article

We introduce TriHex-Cluster, a hierarchical overlapping clustering framework built on the self-similar geometry of the triangular lattice (6-regular planar graph). The primary algorithm is regime C (greedy 2-packing followed by Voronoi completion), a practical hierarchical clustering method producing disjoint clusters with the Voronoi-contact graph $G_{\mathrm{Vor}}^{(k+1)}$ as the next-level graph and aggregation complexity $O(nlogn)$ (embedding cost excluded). On regular triangular domains with near-perfect packings, regime C achieves $n^{(k+1)}\le n^{\left(k\right)}/7+O\left(\sqrt{n^{\left(k\right)}}\right)$ per level; the measured depth on finite data is $K^{\ast }=\lceil {log}_{7}n\rceil \pm 1$. Two variants complete the framework: regime A (full-overlap edge-induced, ${\mathcal{C}}^{\left(k\right)}=V^{\left(k\right)}$) adds native overlap semantics by preserving the EI meta-graph 6-regularity without reducing the vertex count; regime B (deterministic index-7 sublattice, ${\mathcal{C}}^{\left(k\right)}={\mathsf{\Lambda }}_k$ with $\mathbf{a}=2-\omega$) is a theoretical construction establishing an exact sublattice density ratio of 7 per level on the infinite lattice $\mathbb{T}$, and exact termination in $K={log}_{7}n$ levels on finite periodic domains with $n=7^K$. Unconditional results: EI 6-regularity in regime A; perfect star-tiling and exact index-7 structure in regime B; strict hierarchy via Voronoi-completed clusters in regime C; tile-shape alternation proven at levels 1–2 (hexagonal, then triangular-like) and conjectured, with numerical verification, beyond; $h_{\mathrm{Ward}}$ (as an unnormalised SSE) strictly admissible and $h_{max}$ weakly admissible. Aggregation complexity, embedding excluded: $O(nlogn)$ in regime C, $O\left(n\right)$ in regime B, $O(n·K_{max})$ in regime A. We provide a fully reproducible reference implementation (trihex2, MIT-licensed) with extensive parameter sweeps on UCI benchmarks, synthetic Gaussians, non-convex shapes, and overlapping distributions. The genuine contributions of the framework are the multi-scale hierarchical structure with provable geometric guarantees and, in regime A, native overlap semantics that no hard-clustering baseline can provide. A central empirical finding concerns the embedding: an ablation isolating the 2D-lattice projection shows it to be the main bottleneck, and a lattice-free variant that runs the same combinatorial core directly on a k-nearest-neighbour graph in the original feature space—with no embedding and no quantisation—removes the projection entirely and improves accuracy on six of seven pilot datasets. With a frozen, fully unsupervised meta-selection rule (graph-geodesic arbitration between a convex-consensus and a graph-min-cut candidate, no per-dataset tuning), this variant reaches ARI $0.871$ on moons and $1.000$ on circles, where k-means, HAC, and GMM all collapse to $\le 0.43$ and $\le 0.00$, respectively. On a 73-dataset benchmark (23 real UCI, 50 synthetic, all loaded with validated class labels), TriHex is the most frequently best method on the synthetic panel ($46\%$ win rate) and close behind GMM overall ($34\%$ versus $36\%$), while having the lowest mean ARI—the signature of a specialist: it dominates on non-convex structure (rings, spirals, manifolds) and is outperformed on convex tabular data, where we make no claim of superiority. We also report a genuine robustness limitation: with the default configuration, TriHex fails on Cancer (ARI $0.042$, essentially uncorrelated with the ground truth) because the default lattice over-fragments a two-class problem; competitive performance requires a dataset-appropriate configuration, and we report this explicitly rather than only the best configurations. On overlapping Gaussians, regime A detects the boundary points that the data-generating process itself classifies as ambiguous with precision $1.00$ at heavy overlap ($\delta =0.5$); the detector over-flags as the clusters separate (precision falls to $0.43$ at $\delta =3.0$), so its usefulness is confined to the strong-overlap regime. Within that regime, it provides a measurable capability unavailable to hard-clustering baselines. Full article

Additive manufacturing [AM; three-dimensional (3D) printing] is reshaping heterogeneous photocatalysis by enabling architected materials and devices that span from centimeter-scale monoliths to micro- and lab-on-chip reactors. Heterogeneous photocatalysts have traditionally been deployed as powders or simple coatings, which offer high activity but suffer from mass-transfer limitations, poor light utilization and difficult recovery. Three-dimensional (3D) printing now allows precise control over macroscopic geometry, internal channel networks and micro-/nano-scale surface texturing, creating structured photocatalysts and microreactors that can be tailored for specific photon and flow fields. In contrast to recent reviews that primarily survey materials development or additive-manufacturing routes, this work focuses on photocatalytic microreactors and lab-on-chip devices as multi-scale reactors in which catalyst composition, architected geometry, photon management and hydrodynamics are co-designed across length scales. We summarize three-dimensional 3D-printed photocatalytic systems based on polymer–oxide composites, ceramic scaffolds such as zinc oxide (ZnO)/titanium dioxide (TiO₂) clay monoliths, and laser-written titanium dioxide (TiO₂) nano-architectures, with particular emphasis on microfluidic and lab-on-chip implementations fabricated by fused deposition modeling (FDM), direct ink writing (DIW), stereolithography (SLA), digital light processing (DLP) and laser direct writing (LDW). Based on the literature data and representative case studies, we examine how architected lattices, sponges and microreactor chips affect key performance metrics—apparent rate constants, apparent quantum yield (AQY) and space–time yield (STY)—for the degradation of dyes, antibiotics, detergents and other emerging contaminants in realistic matrices, and we compile reported values to illustrate emerging performance trends and limitations. Representative case studies highlight 3D-printed manganese-doped zinc oxide (Mn:ZnO)-decorated sponges used as modular cartridges for greywater and detergent treatment, as well as laser-written titanium dioxide (TiO₂) nano-photocatalysts integrated into microchannels to couple structured light fields with controlled residence times. Finally, we outline materials and process challenges—including ultraviolet (UV) aging of polymer supports, the energy intensity of ceramic sintering and the lack of standardized testing protocols—and identify future research directions formulti-scalee modeling and techno-economic evaluation of three-dimensional (3D)-printed photocatalytic microreactors and devices. Full article

In the present paper, a scalable and continuous process with maximum treatment temperatures of 2000 °C for making cellulose-based carbon fibers (CFs) having Young’s moduli of up to 230 $\mathrm{G}$$\mathrm{Pa}$ is presented. This unexpected high modulus was realized by using a boric acid (BA)-doped viscose precursor yarn. Such a precursor shows significantly improved orientability during carbonization, resulting in highly oriented CFs. For clarifying the underlying effect, a BA-doped and an undoped precursor (reference) were carbonized at different stretch levels, and the resulting CFs were systematically analyzed in terms of structural parameters characterizing the crystalline phase, i.e., crystallite dimensions ($L_a$, $L_c$), lattice plane spacing ($d_{002}$), and crystallite orientation ($⟨{cos}^2\varphi ⟩$). Moreover, electrical resistivity and mechanical properties were determined. It was found that BA promotes the formation of graphite-like structures and their alignment with the fiber axis. Finally, both effects result in significantly improved CF properties, particularly electrical conductivity and Young’s modulus, which are nearly three times and two times higher, respectively, than those of the reference. To explain the effectiveness of BA during thermal conversion, a microstructural mechanism is proposed based on results from a uniform stress model. Full article

Powder X-ray diffraction was used to validate the crystal structure of iron metal powder and to demonstrate a transparent workflow for extracting crystallographic and microstructural information from a simple laboratory dataset. The diffraction profile collected over the angular range of approximately 36° to 95° contains three dominant reflections located at 2θ = 44.850°, 65.218°, and 82.540°. Conversion of the peak positions into d-spacings using Bragg’s law gives values of approximately 2.020 Å, 1.430 Å, and 1.170 Å. The squared-sine ratios, when referenced to the first reflection, follow the sequence of 1:2:3, which is characteristic of the allowed reflections of a body-centered cubic lattice when multiplied by the first allowed value of N = h² + k² + l² = 2. Therefore, the peaks are assigned to the (110), (200), and (211) reflections of α-Fe. The extracted lattice constants are 2.853, 2.860, and 2.865 Å, yielding an average value of 2.859 Å, which is close to the accepted room-temperature value of approximately 2.866 Å for α-Fe. Peak-width calculations based on the observed, instrument-uncorrected FWHM values are included only as illustrative apparent line-broadening indicators. Because an external instrumental standard was not measured under identical conditions, no quantitative coherent-domain size or microstrain is claimed. The Williamson–Hall treatment is therefore used only to demonstrate the sensitivity of size-strain interpretation to peak breadth, profile selection, and the limited number of available reflections. The intensity hierarchy was analyzed using the body-centered cubic-structure factor, reflection multiplicity, Fe atomic form factor, and Lorentz polarization correction. The comparison between calculated and experimental intensities shows stronger disagreement than the lattice-parameter analysis, illustrating the greater sensitivity of intensity analysis to preferred orientation, specimen preparation, peak-profile selection, and background treatment. The work provides a publication-style reconstruction of an iron powder XRD experiment, connecting peak fitting, indexing, lattice-parameter determination, crystallite size estimation, size-strain analysis, and intensity interpretation in a single critical framework. Full article

The electrocatalytic performance of transition metal dichalcogenides (TMDs) is often hindered by their basal planes. Although defect engineering and heteroatom doping are employed, improving the electrocatalytic activity of the basal plane without disrupting the in-plane lattice structure remains a challenge. The interlayer twist serves as an effective strategy to preserve the in-plane lattice integrity of TMDs and tune their electrocatalytic performance. In this work, high-quality twisted bilayer MoS₂ (TBL-MoS₂) was fabricated through polydimethylsiloxane (PDMS)-assisted mechanical exfoliation and dry transfer stacking. On-chip electrochemical nanodevices were subsequently constructed to investigate hydrogen evolution reaction (HER) performance at different twist angles. This demonstrates that bilayer MoS₂ with a twist angle of 15° (TBL-15°) exhibits superior hydrogen evolution reaction performance with a Tafel slope of 63 mV/dec, significantly lower than the value of 202 mV/dec of the pristine bilayer. This work paves the way for twist angle engineering in designing high-performance 2D electrocatalysts. Full article

Hydrogen-rich compounds under high pressure are promising for high-temperature superconductivity, but many high-$T_{\mathrm{c}}$ hydrides rely on rare-earth or alkaline-earth elements and remain difficult to tune chemically. Transition-metal hydrides offer an alternative platform because partially filled d states can modify the electronic density of states, metal–hydrogen hybridization, and electron–phonon coupling. Here, ${\mathrm{VH}}_3$ is used as a parent high-pressure transition-metal hydride framework, and Ti substitution is introduced as a chemically compatible way to tune the d-derived states near the Fermi level. Two ternary hydrides, ${\mathrm{Ti}}_3{\mathrm{VH}}_{12}$ and ${\mathrm{TiV}}_3{\mathrm{H}}_{12}$, are therefore constructed from the ${\mathrm{VH}}_3$ lattice and investigated by first-principles calculations at 200 GPa. Both compounds are thermodynamically and dynamically stable under this pressure condition, as indicated by formation energies, the Ti–V–H convex hull, and phonon spectra. Within the same ultrasoft-pseudopotential computational framework, ${\mathrm{Ti}}_3{\mathrm{VH}}_{12}$ and ${\mathrm{TiV}}_3{\mathrm{H}}_{12}$ yield Allen–Dynes $T_{\mathrm{c}}$ values of 42.1 K and 36.8 K, respectively, higher than the corresponding ${\mathrm{VH}}_3$ value. A norm-conserving cross-check for ${\mathrm{VH}}_3$ gives a different absolute value, indicating that the $T_{\mathrm{c}}$ estimates are method-dependent. Electronic structure analysis indicates that Ti incorporation shifts pronounced van Hove singularities close to the Fermi level, enhances the density of states, and changes the Fermi surface topology. These results suggest that Ti–V–H hydrides are a useful model system for examining how transition-metal substitution can couple structural stability with electronic tuning in compressed hydride superconductors. Full article

The particle size refinement of hercynite (FeAl₂O₄) powders during wet high-energy mechanical milling was investigated through an integrated experimental and kinetic modeling approach. Hercynite powders were milled for different durations, and their microstructural, chemical, and particle size evolution was characterized using scanning electron microscopy, X-ray diffraction, semi-quantitative X-ray fluorescence analysis, and SEM–ImageJ-based particle size reconstruction. Particle size distributions were reconstructed from large particle populations, and the characteristic descriptors $D_{10}$, $D_{50}$, and $D_{90}$ were determined from empirical cumulative distributions. The results revealed a pronounced reduction in median particle size from approximately 83.1 $\mathrm{\mu }$m in the as-received powder to 0.422 $\mathrm{\mu }$m after 8 h of milling. X-ray diffraction analysis showed progressive peak broadening and intensity reduction with increasing milling time, suggesting milling-induced structural disorder and possible crystallite refinement and/or lattice strain accumulation, while no additional crystalline phases associated with milling-induced decomposition were detected within the detection limit of XRD. Semi-quantitative chemical analysis indicated limited metallic transfer from the stainless-steel milling media under the applied wet milling conditions. The evolution of $D_{50}$ with milling time exhibited a non-linear behavior characterized by rapid particle fragmentation at early stages, followed by a gradual transition toward a refinement-limited regime. This behavior was described using a first-order kinetic model with saturation behavior, yielding an asymptotic particle size of 0.443 $\mathrm{\mu }$m and an effective milling rate constant of 1.539 h⁻¹. Overall, the proposed kinetic framework provides a descriptive and condition-specific quantitative basis for interpreting the competing fracture and agglomeration mechanisms governing particle size evolution during wet mechanical milling of refractory spinel powders. Full article

Catalytic oxidation is one of the most effective technologies for controlling atmospheric pollutants like carbon monoxide (CO), volatile organic compounds (VOCs), and diesel soot. Catalyst performance is governed by the interplay between reaction mechanisms, physicochemical properties, and catalyst architecture. This review provides a comprehensive overview of the fundamental oxidation pathways, including Langmuir–Hinshelwood, Eley–Rideal, and Mars–van Krevelen mechanisms, highlighting their relationship with oxygen mobility, oxygen vacancies, redox behavior, and metal–support interactions. The catalytic roles of noble metals and transition metal oxides are comparatively discussed, with emphasis on the contribution of lattice oxygen and defect chemistry to oxidation activity. The review also examines recent advances in structured catalysts designed to improve heat and mass transfer, catalyst accessibility, and practical reactor performance. Particular attention is given to biomorphic fibers, electrospun nanofibers, catalytic ceramic papers, conventional monoliths, and additively manufactured (3D-printed) monolithic structures as emerging platforms for environmental catalysis. Unlike previous reviews focused primarily on catalyst composition or individual oxidation reactions, this review integrates oxidation mechanisms, catalyst chemistry, and emerging structured catalyst architectures to provide a unified perspective on the design of efficient, durable, and scalable catalytic systems for environmental oxidation applications, while identifying key challenges and future research directions. Full article

Developing lead-free organic-inorganic hybrid metal halides with strong light-harvesting capabilities and superior stability, while precisely tuning their crystalline phases and electronic structures, remains a key challenge in optoelectronics. Herein, we report a neutral iodine-induced structural transition from a 1D chain-like (C₆H₁₁NH₃)₂SbI₅ architecture to a 0D dimeric (C₆H₁₁NH₃)₃[Sb₂I₉]·I₂ supramolecular host-guest complex. This transformation is achieved via a controlled solution-cooling crystallization process, yielding high-quality bulk single crystals. Crystallographic analysis reveals that N–H···I hydrogen-bonding networks stabilize the organic cations, while halogen bonding interactions anchor the I₂ guests within the lattice cavities of the [Sb₂I₉]³⁻ dimeric host. Experimental characterizations, including XRD, TGA, and XPS, confirm the high phase purity and thermal stability of the (C₆H₁₁NH₃)₃[Sb₂I₉]·I₂ hybrid and determine its electronic band structure. To further elucidate the underlying mechanisms, theoretical calculations were performed, revealing that strong sp-orbital hybridization yields a high absorption coefficient. The associated dimensional transition narrows the direct optical bandgap to 1.46 eV, approaching the Shockley-Queisser limit and demonstrating strong potential for visible-light harvesting. This work elucidates the role of supramolecular host-guest interactions in modulating the lattice evolution of lead-free antimony-based materials, presenting halogen guest engineering as an effective approach for optoelectronic material design. Full article

In this paper, a simple and compact 1 × 2 decoder based on a two-dimensional photonic crystal structure is proposed, whose operation relies on total internal reflection and photonic band gaps. The designed structure employs a square-lattice configuration of silicon dielectric rods embedded in air. The decoder consists of two input ports, one acting as a Bias port and the other as a logical input port. Numerical modeling and simulations are performed using the plane-wave expansion (PWE) method and the finite-difference time-domain (FDTD) technique. The proposed coupling-resonator structure increases the coupling efficiency at resonant frequencies. The structure has a relatively small footprint, comprising an 18 × 18 array of dielectric rods with a total area of approximately 147 µm². A minimum contrast ratio of about 8.4 dB between logical “1” and “0” states is achieved. The decoder operates at 1.55 µm, making it suitable for photonic and optical communication applications. Due to its compact size, simple architecture, and use of a minimal number of ring resonators, the proposed decoder is well suited for high-speed photonic integrated circuits and future all-optical computing systems. The bit rate of the proposed decoder is estimated to be 2 Tb/s. Full article

The lubrication performance of high-speed transmission systems directly affects mechanical power consumption and operational reliability. During high-speed oil-stirring lubrication, strong gas–liquid interfacial shear, liquid-film deformation, droplet splashing, and oil-mist transport generate an unsteady multiphase turbulent flow field. Conventional continuum-based numerical methods often face difficulties in resolving interface breakup and transient turbulent dissipation under high-speed rotational excitation. To address this problem, this study develops a coupled Lattice Boltzmann–Large Eddy Simulation (LBM–LES) method for oil–air two-phase flow in a high-speed oil-stirring lubrication system. The D3Q27 discrete velocity model, cumulant collision operator, WALE subgrid-scale model, free-surface tracking, and local grid refinement are integrated to analyze free-surface deformation, oil-mist evolution, and power-loss characteristics. Taking a notched toothless oil-stirring disk as the reference configuration, the effects of oil immersion depth and disk topology on gas–liquid phase distribution, oil-mist coverage, power consumption, and vortex-induced energy dissipation are investigated. The results indicate that oil immersion depth has a nonlinear influence on lubrication performance and power loss. Among the investigated cases, an immersion depth of 20 mm provides a favorable balance between upper-region oil-mist coverage and lower-region oil-pool stability. At this depth, the notched disk exhibits directional oil delivery and relatively low power consumption, whereas the double-rhombus structure expands the oil-mist coverage but increases the average power consumption to approximately 175 W. These findings provide numerical support for balancing oil-mist coverage, mechanical power consumption, and disk topology design in high-speed transmission lubrication systems. Full article

We propose a lattice structure and space group symmetry, Pmmm (No. 47), for the QCD condensate ground state, whose Wyckoff positions are occupied by the four light quarks and antiquarks $u$, $d$, $\tilde{u}$, $\tilde{d}$. These serve as the fundamental building blocks of both the condensate lattice ground state and the baryonic and leptonic particle excitations embedded within it as topological defects of the nominal Wyckoff occupation, offering a more structured alternative to the QCD instanton liquid picture. Building on Bloch quark wave solutions of a tight-binding Hamiltonian defined on this lattice, we propose a generalization of Einstein’s Equivalence Principle: composite particles embedded in the lattice and propagating by tunnelling cannot distinguish acceleration by gravity, the strong, weak, or electromagnetic forces, or curvature of the lattice itself, arising from local variation in unit cell shape. We derive an eight-by-eight tight-binding Hamiltonian that decouples into two four-by-four blocks separating the quark and antiquark sectors. Electrons, positrons, protons, neutrons, deuterons, and α-particles are embedded in the lattice as defect-induced deviations from the nominal Wyckoff occupation, with their spin and helicity emerging structurally from this picture. We further propose that the lattice’s unit cells carry a small nonzero rest mass, whose collective gravitational effect across a galactic halo may account for the discrepancy between visible mass and rotation curves, identifying the Pmmm condensate as a dark matter candidate. Finally, we outline a mechanism near black hole horizons by which local melting of the condensate lattice followed by quark reactions that conserve the number and flavor of the quarks could yield a new route to baryon asymmetry. We propose a framework that goes several steps beyond the Standard Model by introducing a Pmmm space group unit cell for the QCD condensate ground state, built from the four light quarks and antiquarks $u$, $d$, $\tilde{u}$, $\tilde{d}$. We further propose that topological defects of the Pmmm condensate lattice are the geometric origin of particle excitations. Full article