Journal of Materials Science & Technology最新文献

The concept of grain boundary engineering (GBE) has been successfully applied to L1₂-strengthened (CoCrNi)₉₄Al₃Ti₃ medium entropy alloy, with the aim of improving the oxidation resistance by increasing the ratio of special boundaries and suppressing discontinuous precipitation. Surprisingly, our results reveal that GBE treatment not only slows down the oxidation kinetics and but also alters the oxide scale from TiO₂ and multi-defect Cr₂O₃ to continuous and protective Cr₂O₃ and Al₂O₃, thereby contributing to an enhanced oxidation and anti-spalling resistance. The GBE treatment reduces the oxidation weight gain of the current alloy from 1.950 mg cm^–2 to 1.211 mg cm^–2 after 100 h of cyclic oxidation at 800 °C. The findings show that the extensive outward diffusion of Ti accelerates ion transport and promotes microporosity, thus leading to more defects being formed in the oxide film. The GBE treatment suppresses the discontinuous precipitation of the Ti-bearing L1₂ phase and breaks the random large angular grain boundaries network, inhibiting the diffusion of Ti and ultimately enhancing the oxidation properties of the alloy. The current work provides an idea of oxidation resistance enhancement for Ti-bearing L1₂-strengthened alloys without changing the alloy composition.

The rise of smart wearable devices has driven the demand for flexible, high-performance optoelectronic devices with low power and easy high-density integration. Emerging Two-dimensional (2D) materials offer promising solutions. However, the use of 3D metal in traditional 2D devices often leads to Fermi-level pinning, compromising device performance. 2D metallic materials, such as graphene and 2H-phase NbSe₂, present a new avenue for addressing this issue and constructing high-performance, low-power photodetectors. In this work, we designed an all-2D asymmetric contacts photodetector using Gr and NbSe₂ as electrodes for the 2D semiconductor WSe₂. The asymmetric Schottky barriers and built-in electric fields facilitated by this architecture resulted in outstanding photovoltaic characteristics and self-powered photodetection. Under zero bias, the device exhibited a responsivity of 287 mA/W, a specific detectivity of 5.3 × 10¹¹ Jones, and an external quantum efficiency of 88%. It also demonstrated an ultra-high light on/off ratio (1.8 × 10⁵), ultra-fast photoresponse speeds (80/72 μs), broad-spectrum responsiveness (405–980 nm), and exceptional cycling stability. The applications of the Gr/WSe₂/NbSe₂ heterojunction in imaging and infrared optical communication have been explored, underscoring its significant potential. This work offers an idea to construct all-2D ultrathin optoelectronic devices.

In the present study, a single parameter governing the substructure and the strengthening for martensitic transformation was tentatively explored by detailing the microstructure and the strengthening of a Fe-15 wt.%Cr binary alloy subjected to thermal cycle under high pressure (cooled at 10°C s^–1 from 1050°C under hydrostatic pressure of 1.0–4.0 GPa). Experimental results show that high pressure makes martensitic transformation occur in a Fe-15Cr alloy that traditionally has no high-temperature austenite under atmospheric pressure. The phase transformation begins with the pairing of twinned variants, and the strengthening is solely dependent upon the density of dislocations and variants. The austenite strength at the transformation temperature governs the substructure and the induced strengthening by influencing: (1) The critical size below which twinned variants are solely allowed; (2) the orientation spreading of the pioneer twinned variants toward Bain pairs; (3) the variant thickness and in turn the strengthening extent. The present study sheds light on tuning the substructure and hardening during martensitic transformation via the austenite strength, showing potential scientific and technological importance.

A new nanostructured ZrB₂-ZrC composite coating with ZrB₂-ZrC nanoscale eutectic and ZrB₂+Amorphous microstructure was synthesized in situ by plasma spraying Zr-B₄C-Al composite powder. The thermal analysis, quenching experiments and microstructure characterization were investigated and the formation mechanism of the bimodal in-situ microstructure was revealed. Al contributed to the liquid phase separation of molten droplets, which is the key to forming ZrB₂+Amorphous microstructure. The formation of coating followed reaction-melting-liquid separation-deposition and solidification mechanism. The nanostructured ZrB₂-ZrC composite coating with Al-O intergranular amorphous phase has excellent mechanical properties. The uniform nano-grains improved the hardness and the toughness of the ZrB₂-ZrC eutectic. The ZrB₂+Al-O amorphous microstructure obtained high toughness and the toughening mechanism was the crack deflection and crack branching caused by intergranular Al-O amorphous phase.

Multicomponent composites are considered conducive to electromagnetic wave (EMW) absorption, as multiple loss synergistic effect from each component, enhance the attenuation ability of EMW and optimize impedance matching. In this study, carbon material was modified by both semi-conductive and magnetic matters to improve their absorbing performance. The carbon-based fibrous composites of CeO₂ and Co were prepared by electrospinning and subsequent carbonization. At a filling rate of 35 wt.%, the CeCoC nanocomposite fibers exhibit a minimum RL value of -61.4 dB at 2.2 mm, and an effective absorption bandwidth (EAB) of up to 7.6 GHz. The excellent absorbing performance is derived from the improved dielectric loss and optimized impedance matching. The introduction of rare earth oxide CeO₂ not only helps to maintain the fibrous structure, but also promotes conduction loss. Especially, oxygen vacancy defects introduced by CeO₂ greatly improved the dielectric loss capacity. The introduction of Co particles optimizes the impedance matching to reduce the matching thickness and strengthen magnetic loss. This study demonstrates the potential of rare earth oxides in improving EMW absorption performance, and opens up new opportunities for the development of advanced materials for high-performance EMW absorption applications.

Treating severe burn wounds poses significant challenges, including considerable cell loss, excessive inflammation, and a high susceptibility to bacterial infections. Ideal burn dressings should exhibit excellent antibacterial properties, anti-inflammatory effects, and promote cell proliferation. Additionally, they need facilitate painless dressing changes and be user-friendly. Herein, we synthesized a thermosensitive hydrogel by crosslinking poly (N-isopropylacrylamide-co-allyloxybenzaldehyde) (PNA) and amino-terminated Pluronic F127 (APF) through a Schiff base reaction. It exhibited reversible gel-sol transition and spreadability. By incorporating piezoelectric gold nanoparticle-modified barium titanate (Au@BaTiO₃) and cascade antioxidant MOF-818, a nanocomposite hydrogel dressing with diverse bioactive functionalities was developed. Results demonstrated that the nanocomposite hydrogel possessed gel-sol transition properties, maintained a stable gel state within a broad temperature range, and desirable self-healing property. Au@BaTiO₃ exhibited good piezoelectric properties and ROS generation upon ultrasound stimulation, while MOF-818 displayed highly efficient cascade nanozyme activity. The combination of Au@BaTiO₃ and MOF-818 promoted fibroblast proliferation and migration, reduced intracellular ROS levels, and induced anti-inflammatory polarization of macrophages under ultrasound stimulation. In vitro and in vivo antibacterial results disclosed that the nanocomposite hydrogel had excellent antibacterial activity under high-intensity ultrasound stimulation. When applied to infected burn wounds, the nanocomposite hydrogel can rapidly sterilize the wound upon initial high-intensity ultrasound, and then reduce inflammation and promote M2 macrophage polarization by the following low-intensity ultrasound stimulation, and thus accelerating the healing by improving granulation tissue formation, angiogenesis, and collagen deposition.

A heterogeneous CoNiCr₂ eutectic medium-entropy alloy (EMEA), comprising soft face-centered cubic (FCC) and hard body-centered cubic (BCC) lamellae, associated with minor acicular hexagonal close-packed (HCP) phase precipitated in BCC phase, was synthesized towards excellent tensile strength and ductility synergy. The tensile mechanical properties demonstrated that this alloy was temperature-dependent, i.e., when the testing temperature reduced from room temperature (RT) to liquid nitrogen temperature (LNT), the yield strength, ultimate strength, and uniform elongation were enhanced from 449 MPa, 821 MPa, and 5.0% to 702 MPa, 1174 MPa, and 8.4%, respectively. The prominent elevation of yield strength at LNT mainly resulted from the dramatically enhanced lattice friction stress (σ₀) and the FCC-BCC interfacial strengthening, while the improved ductility was attributed to the superior crack-arrest capability of FCC matrix stemmed from the accumulation of stacking faults (SFs) and enhanced σ₀ at LNT. Additionally, although the deformation mechanisms were dominated by planar dislocation glides and SFs at both temperatures, the initiation of premature cracks in the BCC phase due to the inferior deformation capability at LNT constrained the better strength-ductility trade-off. The cracks in the BCC phase tended to propagate along the BCC-HCP interfaces because of the strain incompatibility. Furthermore, the sub-nanoscale L1₂ particles in the FCC matrix could not only strengthen this alloy but also improve the stacking fault energy leading to no deformation twinning even at LNT. This work may provide a guide for the design of remarkable strength and ductility synergy EMEAs combined with outstanding castability for applications at cryogenic temperatures.