Shaolei Song

Tailoring polymeric carbon nitride (CN) to simultaneously broaden its light absorption range and improve charge carrier mobility remains a key challenge for photocatalytic H ₂ O ₂ production. The molecular junction strategy has been proven to be an effective approach to address the aforementioned challenges. In this work, we developed a molecular junction through controlled thermal ring‐opening isomerization of benzoguanamine, thereby creating a well‐defined C‐C‐bridged benzene‐heptazine molecular junction. Experimental and theoretical studies reveal that: (1) Benzene functionalization extends the π‐conjugation, enabling n→π* transitions for broad‐spectrum absorption; (2) The donor‐acceptor structure enhances self‐polarization effects, strengthening the built‐in electric field for efficient charge separation; (3) The unique molecular architecture overcomes traditional kinetic limitations, enabling a dual‐channel H ₂ O ₂ synthesis mechanism. The optimized catalyst achieves remarkable production rates of 5222 µmol∙g ^{− 1} ∙h ^{− 1} in isopropanol/water and 1587 µmol∙g ⁻¹ ∙h ⁻¹ in pure water, representing 13.1‐fold and 32.4‐fold improvements over pristine CN, respectively. This work advances molecular‐scale design of photocatalysts and offers new strategies for artificial photosynthesis.

Ultrasonic inspection of welded steel components remains challenging due to weld-scale material gradients, local anisotropy, attenuation, and aperture limitations. These factors severely distort both the first-arrival wavefield and the late-arriving scattered wavefield. To address this, this study presents a numerical proof of concept for three-dimensional cross-weld virtual-array coda-wave tomography (VACWT). The “virtual array” utilizes a synthetic aperture created by re-indexing sequential source–receiver records from two opposing line scans into midpoint–angle–depth coordinates. This approach enables line-based data acquisition to achieve multi-angle volumetric coverage without requiring a two-dimensional matrix array. A parameterized welded-solid benchmark model was developed, incorporating effective longitudinal and shear wave velocities, attenuation, and out-of-plane tilt fields. Four defect scenarios were evaluated: a cylindrical void, a lack-of-fusion ribbon, a porosity cluster, and an interference case. For each source–receiver path, four observables were extracted from the synthetic records: first-arrival travel time perturbations, coda wave stretching, coda decorrelation, and late-window energy ratios. These observables were then coupled into a volumetric inverse problem to separate smooth slowness variations, distributed scattering strength, and compact defect occupancy. Under the current simulation conditions, VACWT achieved smaller recovered support volumes and higher volumetric overlap compared to the delay-and-sum total focusing method (DAS-TFM), background-corrected TFM, and reverse time migration (RTM). In the interference case, applying a fixed defect-free calibration threshold yielded a centroid error of 0.48 mm, a volumetric intersection over union (IoU) of 0.856, and a false-positive volume fraction of 0.0%. While these findings serve as benchmark results rather than generalized experimental validation, the study demonstrates that late scattered wave observables provide valuable constraints for volumetric support recovery in a controlled welded-solid model. Future experimental verification on welded steel specimens with known defects remains necessary.

Two-dimensional nanomaterials exhibit excellent physical barrier properties, which can effectively enhance the corrosion resistance of waterborne epoxy coatings. Herein, we report a facile strategy for preparing a multi-component synergistic anti-corrosion coating, where two-dimensional graphitic carbon nitride (g-C₃N₄) and high-entropy layered double hydroxides (HE-LDHs) are integrated into a waterborne epoxy matrix via magnetic-ultrasonic synergistic dispersion. The resulting HE-LDHs/g-C₃N₄-epoxy coating exhibits exceptional corrosion resistance for Q235 steel. Electrochemical impedance spectroscopy (EIS) and polarization curves showed that when the mass ratio of g-C₃N₄ to HE-LDHs was 1:1, the resulting coating (PCN-LDH-1.0) maintained a coating resistance of 5.48 × 10⁵ Ω·m² after 28 days of immersion in 3.5% NaCl solution, which was five orders of magnitude higher than that of pure waterborne epoxy coating. Meanwhile, the corrosion current density was reduced by four orders of magnitude, from 5.83 × 10⁻¹ A·m⁻² to 1.68 × 10⁻⁵ A·m⁻². After 30 days of salt spray testing, no rust, blistering or adhesion loss was observed on the coating surface. These enhanced performances by addition of g-C₃N₄ and HE-LDHs were attributed to the combined effects of the tortuous diffusion pathways. Additionally, the PCN-LDH-1.0 coating retained excellent mechanical properties, including a pencil hardness of 3H and the highest adhesion grade. This study provides a facile method for preparing high-performance waterborne anti-corrosion coatings.

(Zr,Ti)B₂ ceramics with enhanced hardness and fracture toughness were prepared by spark plasma sintering using platelet TiB₂ and irregular ZrB₂ as starting powders. The effects of sintering temperature (1700–1900 °C) and platelet TiB₂ content (0–30 wt.%) on the sinterability, phase composition, microstructure, and mechanical properties of the (Zr,Ti)B₂ ceramics were investigated. With increasing sintering temperature, the relative density of the solid solution increased from 89.9 ± 0.5% at 1700 °C to 97.7 ± 0.4% at 1800 °C, followed by no significant change upon further temperature elevation; however, the relative density showed an initial increase and subsequent decrease with increasing TiB₂ content. Under optimized parameters (1800 °C, 3 min, 50 MPa, with a TiB₂ content of 30 wt.%), (Zr,Ti)B₂ ceramics achieve a maximum hardness of 24.9 ± 1.0 GPa, a fracture toughness of 5.0 ± 0.3 MPa·m^1/2, and a relative density of 96.5 ± 0.5%. The high content of platelet TiB₂ refined the (Zr,Ti)B₂ grain size, reducing the D50 by 25.8% to 1.70 μm compared to the 20 wt.% content. This study provides a novel perspective for the design and preparation of high-performance ceramics.

Titanium diboride (TiB2) materials have garnered significant attention due to their remarkable comprehensive properties. They offer potential applications in high-temperature structural materials, cutting tools, armor, electrodes for metal smelting, and wear-resistant parts. However, due to the low self-diffusion coefficient, the TiB2 exhibits poor sinterability, excessive grain growth at elevated temperatures, and inadequate oxidation resistance, limiting its wide application. Therefore, many research works are devoted to processing TiB2 at a lower sintering temperature and improving the properties through various sintering additives and more advanced techniques. This article comprehensively reviews the multiple synthesis methods and sintering technologies of TiB2, and at the same time, critically discusses the impacts of sintering additives and reinforcing agents on densification, microstructure, and various properties, including those at high temperatures, and finally predicts the future development of TiB2 composite materials.

Concrete cover cracking induced by reinforcement corrosion is an important indication of the durability limit state for reinforced concrete (RC) structures and can be used to determine the structural service life. The process of rebar corrosion from the beginning of rusting to the occurrence of cover cracking due to corrosion expansion can be divided into two phases: the phase of the free expansion of the corrosion product and the phase of cover cracking. Based on the assumption of the uniform corrosion of the reinforcement, one model for predicting the reinforcement corrosion depth from corrosion initiation to cover cracking was established according to the cylindrical cavity expansion theory. The main factors affecting the reinforcement corrosion depth were analyzed. The main factors affecting the corrosion depth of reinforcement were analyzed. The quantitative sensitivity analysis of the factors influencing the calculation formula shows that the depth of reinforcement corrosion and the thickness of the concrete protective layer are approximately linearly increasing, with a growth rate of 0.2366 μm/mm; the diameter of the reinforcement is approximately linearly decreasing, with a decrease rate of 0.2122 μm/mm; the volume expansion rate of rust is approximately power function decreasing; the overall influence range of the yield criterion selection parameter is 0.15 μm; for the concrete strength grade, the overall influence range is 0.1 μm. The coefficient of determination R2 is 0.87, and the overall accuracy of the calculated formula is high, which can be used to predict the service life of reinforced concrete structures and guide the durability design in combination with the research results on the corrosion rate of reinforcement under different environments.