This work introduces a highly efficient biosensor based on a two-dimensional rod-in-air photonic crystal (PhC) structure arranged in a triangular lattice configuration. The photonic band structure is evaluated using the plane-wave expansion (PWE) method, while sensor performance is analyzed through finite-difference time-domain (FDTD) simulations. The proposed design exhibits a wide photonic bandgap (PBG) and strong optical confinement within the sensing region, enabling highly precise detection of refractive-index variations. A systematic investigation is conducted by varying the rod radius within the sensing region at a constant lattice parameter, followed by an analysis of lattice constant variations while maintaining the optimized rod radius. Both two-dimensional and three-dimensional configurations are explored to validate the robustness of the design. The sensor exhibits strong performance characteristics. For the fixed lattice constant configuration, it achieves a sensitivity of 478.57 nm RIU−1, a high quality factor of 1.6230 × 107, a low detection limit of 1.91922 × 10−8 RIU, and a figure of merit of 5.21043 × 106 RIU−1. In comparison, the variable lattice constant design provides a higher sensitivity of 965 nm RIU−1, along with a quality factor of 9.5621 × 105, a detection limit of 2.13245 × 10−7 RIU, and a figure of merit of 4.68944 × 105 RIU−1. Additionally, considering the practical challenges associated with photonic crystal fabrication, the impact of structural imperfections on sensor performance is comprehensively analyzed. Due to its compact footprint of 82.84 μm2 and excellent sensing capabilities, the proposed biosensor is a promising candidate for integration into advanced on-chip photonic systems.
The advancement of precious-metal-free electrocatalysts for the oxygen reduction reaction is essential for developing proton exchange membrane fuel cells. In the present study, a cobalt-based electrocatalyst embedded within a nitrogen-doped carbon matrix is synthesized via carbonization of a MOF-808 precursor co-functionalized with ethylenediaminetetraacetic acid and cobalt nitrate. The material exhibits a porous structure with homogeneously distributed cobalt-containing species. Structural and morphological characterization (X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, and nitrogen adsorption-desorption isotherms) confirms successful functionalization, cobalt stabilization, and formation of a nitrogen-doped carbon framework. Electrochemical measurements demonstrate effective oxygen reduction reaction activity in acidic electrolytes, possessing an onset potential of 0.87 V vs. RHE, current density of 7 mA/cm2, and electrochemically active surface area of 25 cm2. The catalyst also exhibits stable current retention during chronoamperometry test. The results confirm the potential of Co/C-MOF as a promising platinum-free electrocatalyst for oxygen reduction reaction in acidic media.
When metallic bismuth (Bi) is adopted directly as anode materials for sodium-ion batteries (SIBs), severe volumetric variation emerges during the repeated alloying/dealloying redox reactions. Such structural evolution ultimately triggers electrode structural pulverization and rapid capacity fading of the batteries. Herein, Bi-based metal-organic framework (Bi-MOF) precursors were fabricated via a facile solvothermal strategy. Porous Bi@C composites with tunable morphologies were further synthesized by regulating solvent volume ratios and thermal treatment temperatures. On the one hand, MOF-derived nanoporous carbon frameworks construct abundant conductive pathways for ion and electron migration, thereby boosting the comprehensive electrochemical properties of the as-prepared composites. On the other hand, the electrochemically active Bi species are spatially confined and stabilized within the carbon matrix. This confinement effect efficiently alleviates the inherent volumetric expansion of Bi, and accordingly improves the long-term cycling stability of electrode materials. Among all samples, the optimized Bi@C-100:30-800 electrode delivers superior electrochemical performance. It retains a high reversible specific capacity of 443.6 mAh g-1 after 500 long-term cycles at a current density of 500 mA g-1. Notably, a reversible specific capacity of 416.5 mAh g-1 can still be achieved after 1000 cycles at 1 A g-1, accompanied by a coulombic efficiency of 99.9
Microstructural heterogeneity arising from Mn segregation critically influences the service reliability of ultra-high strength martensitic steels; yet, how such heterogeneity develops and governs the mechanical response remains inadequately understood. This study investigates two ultra-high strength martensitic steels with different C-Mn compositional designs by integrating experimental characterization with multiscale computational approaches, with particular emphasis on Mn segregation behavior, microstructural heterogeneity, and the associated mechanical response. The experimental results reveal distinctly different Mn segregation characteristics in the two steels: the LCHM steel is dominated by dendritic segregation, whereas the HCLM steel exhibits more pronounced centerline segregation. CALPHAD calculations further demonstrate that the C content markedly affects the equilibrium partitioning behavior of Mn as well as the evolution of the liquid fraction during solidification. The resulting Mn segregation gives rise to spatially heterogeneous local microstructures and mechanical responses. Under quasi-static tensile loading, segregation-induced soft and hard regions exhibit pronounced strain partitioning and deformation heterogeneity. In contrast, under dynamic impact loading, continuous segregation bands can serve as preferential crack-propagation paths, thereby leading to significant anisotropy in impact toughness. This work provides new guidance for compositional design and microstructural homogenization control in high-performance automotive steels.
The inhomogeneous hydrogen distribution and difficulty in hydrogenation are critical bottlenecks restricting the application of thermo-hydrogen processing (THP) in TiAl alloys. To address these challenges, this work proposes a novel fabrication route for TiAl alloys via in situ hydrogenation combined with hot isostatic pressing (HIP). Using TiH2 as the hydrogen source, target hydrogen content is designed through proportioning of Ti, TiAl3 and TiH2 powders. HIP densification after sheath sealing and vacuum degassing realizes in situ uniform retention and precise control of hydrogen in the TiAl matrix. Results show this method achieves higher control accuracy and distribution uniformity of hydrogen. Rising hydrogen content induces a significant increase in ( α_2 + γ ) lamellar colony volume fraction than conventional methods, without altering matrix lattice parameters or inducing distinct lattice distortion. Meanwhile, hydrogen optimizes grain size distribution, inhibits abnormal grain growth, and markedly reduces the alloy’s peak stress, providing a reliable route for high-precision and high-uniformity hydrogenation of TiAl.
