Sujuan Wu

Thermal expansion is an intrinsic property of metals and alloys, posing a critical challenge for achieving dimensional stability in lightweight systems where low atomic mass enhances lattice vibrations. Here, we present a strain recovery compensation strategy that achieves three orders of magnitude reduction in thermally induced volume change, enabling zero thermal expansion (ZTE) in a rare-earth magnesium alloy containing 1.2 vol.% Al-stabilized MnCoGe particles. The coefficient of thermal expansion is reduced from 28 × 10⁻⁶ °C⁻¹ to 0.02 × 10⁻⁶ °C⁻¹ over 25-150 °C-the highest thermal stability reported for any alloy. This alloy also retains high compressive strength (424 MPa), ductility (12%), and ultralow density (1.93 g/cm³). The ZTE behavior arises from sustained compressive strain, maintained by reversible martensitic transformation of the embedded particles. Beyond realizing a dimensional stable lightweight alloy, this work establishes a generalizable principle for achieving thermal dimensional stability in metals via recoverable strain.

Alloys with low thermal expansion, high strength, and superior plasticity are crucial for critical applications in industries such as aerospace. Although the in-situ formation of low or negative thermal expansion particles presents a promising strategy, these materials generally suffer from limited ductility. Here, we demonstrate that the construction of nanoscale gradient ordered architectures can effectively addresses this limitation. By facilitating the diffusion and reaction of aluminum (Al) atoms into boronized manganese (Mn-B), we induce a gradient ordering architecture between rare-earthed magnesium (Mg) alloys and MnB phase, achieving a near-zero thermal expansion coefficient of 0.8 × 10^-6·°C^-1 within the temperature range of 280–320 °C. As fully transitioning from Mn-B to a multi-gradient ordered Mn-Al-B configuration results in a stabilized thermal expansion coefficient of 23 ×10^-6·°C^-1 across a broad temperature range (25–400 °C). This nanoscale architecture not only mitigates brittle interfacial fractures by maintaining the mechanical integrity but also enables the Mg alloy to reach an ultrahigh compressive strength of 507 MPa, with a 23.8% compressive strain. Our findings highlight the potential of designing gradient ordered architectures as a strategic approach to enhance the mechanical properties of lightweight alloys.

The introduction of subnanometer clusters as active sites on the surface of photocatalysts for efficiently tuning the selectivity and activity of the photocatalyts is still a challenge. Herein, the subnanometer Ag/AgCl clusters were incorporated on atomically thin defective Bi₁₂O₁₇Cl₂ nanosheets via rebinding with unsaturated Cl atoms. Benefiting from the surficial Bi vacancies (V_Bi) and Bi–O vacancies (V_Bi–O) in this atomically thin architecture, the local atomic arrangement was tuned so that the subnanometer Ag/AgCl clusters were successfully incorporated. An enhancement of photocatalytic activity for NO removal was achieved in which the activity is 3 times higher than that of Bi₁₂O₁₇Cl₂ and 1.8 times higher than that of defective Bi₁₂O₁₇Cl₂. The substitution of the active sites from surficial V_Bi and V_Bi–O to be subnanometer Ag/AgCl clusters enables a tunable redox potential and different reaction mechanisms in NO removal. Moreover, the selectivity of the photoinduced redox reaction on NO oxidation and CO₂ reduction was achieved via introducing an extra energy level.

Two-dimensional (2D) structured photocatalysts with atomically thin layers, not only have the potential to enhance hydrogen generation efficiency, but also allow more direct investigations of the effects of surface terminations on photocatalytic activity. Taking 2D Bi2WO6 nanosheets as a model system, we found that the configuration of bilayer Bi2O2 sandwiched by alternating WO4 layers enabled the thermodynamic driving potential for efficient electron injection and provided the possibility of hydrogen production by water splitting. Without Pt deposition, the H2 generation efficiency can reach to 56.9 μmol/g/h by 2D Bi2WO6 as compared with no activity of Bi2WO6 nanocrystals under simulated solar light. This configuration is easily functionalized by adsorption of Cl-/Br- to form Bi-Cl/ Bi-Br bonds, result in the decrease of the recombination rate of photogenerated electron-hole pairs and narrower bandgap. This work highlights an effective way to design photocatalysts with efficient hydrogen generation from water splitting by tuning the surface terminations.

The oxyhalides have attracted growing interest because of their excellent photocatalytic performance. However, their structural instability hampers further development toward practical applications, a major challenge of current concerns. It is appealing to figure out the origin of structural instability and guide the design of advanced oxyhalide crystals for efficient photocatalysis. In this study, the decomposition of BiOCl crystals, a typical oxyhalide, is triggered by electron beam irradiation and investigated in situ by transmission electron microscopy. The results indicate that the instability originates from the unique layered structure of BiOCl crystals; the interlayer van der Waals bonds are easily broken under electron beam irradiation via the assistance of hydroxyl groups. This facilitates the formation of O/Cl-deficient BiO_1–xCl_1–y species, Bi metal nanoparticles, and nanobubbles (gaseous substance) that are confined between the adjacent layers. Surface reconstruction would be an effective way to stabilize the oxyhalide crystals.