Sensors

This study develops a readily implementable surface modification technique for Al alloys by combining electroplating alloy films with depositing stearic acid to make a durable superhydrophobic coating. Selecting Al as anode for electroplating innovatively, the introduction of Al element improves the adherence and roughness of the coating through a principle identical to the reactive element (RE) effect. Al can be preferentially combined with oxygen to reduce the partial pressure of oxygen, inhibiting outward diffusion and oxidation of the electroplated alloy components, reducing the defects formed by the outward diffusion of the metal elements and the accompanying porosity and cracks. Besides, the dense and stable nature of the oxide film formed by RE effect can better protect the Al alloy substrates from oxidation. It is shown that the crystallinity and oxidation resistance of the alloy is significantly enhanced by the RE effect. Notably, the champion water contact angle has reached 162° ± 0.7°, and a significant reduction in surface porosity is observed. This research has the potential to provide a simplified fabrication process of Ni–Cr–W alloy and pave the way for the development of durability of superhydrophobic film.

Subwavelength structures on MgAl2O4 hold significant technological importance in mid‐infrared (mid‐IR) optics, particularly for windows used in military mid‐IR devices that must operate under harsh conditions. Herein, a novel and efficient strategy utilizing spatially shaped femtosecond laser pulse delay for fabricating antireflective surfaces on hard, difficult‐to‐machine spinel with stable and broadband transmittance in mid‐IR waves is reported. With this method, a new micro–nanohybrid structure composed of a parabolic microhole associated with nanopores (MHNP) is achieved by optimizing Bessel femtosecond pulse delay since the subsequent pulse can irradiate at different stages of materials plasma diffusion, thermal expansion, and phase transformation. The mechanism for more stable transmittance enhancement of MHNP in broadband is explored by the finite‐difference time‐domain simulation, indicating that such localized field selective enhancement in structures is caused by the competition between interface equivalent refractive index effect and the light interference for the parabolic MHNP. As the height of the parabolic microhole and nanopore nears 1 μm and 400 nm, respectively, the resulting transmittance of MHNP with three different periods increases by 3.5–5.5% for 2.85–5.5 μm wavelength, and the maximum transmittance reaches a value of 94.4%.

Herein, spatial tailoring of microstructure, magnetic, and mechanical properties in high‐frequency Ni–Zn ferrite toroidal core over cm‐length scales via an efficient microwave (MW) processing technique is successfully achieved. Depending on gradient processing conditions, one region in a sample (R1) is more efficiently being heated than the other region (R2) due to the spatial variation in losses. The controlled variation of grain sizes (D), saturation magnetization (MS), and microhardness traverses from 0.42 to 2.25 μm, 28 to 76 emu g−1, and 84 to 162 HV, respectively from the R2 to R1. Moreover, the experimentally observed spatially gradient ferrite processing in a single‐mode electric (E)‐field MW cavity is validated with simulation results using finite element modeling. This concept of functionally graded material properties can be an interesting and feasible pathway toward improving performances of a wide range of functional ceramics and related devices, including soft magnetic ferrite materials in power magnetic devices such as transformers and inductors.

Additive manufacturing of magnesium alloys shows great potential for producing patient‐specific resorbable implants or lightweight parts. However, due to the reactive behavior, especially in the laser‐based powder bed fusion (PBF‐LB) fabrication process, the processing window to manufacture almost pore‐free parts is narrow compared to other materials such as titanium or steel. This article investigates optimal processing conditions for the PBF‐LB/M of WE43. To reduce the reactivity of the magnesium melt by limiting the interaction with remaining oxygen, a 3 vol% hydrogen admixture to the argon inert gas is investigated. Furthermore, long‐duration heat treatments are investigated in the range of 250–350 °C for 48 h. This study evaluates the impact of both methods on mechanical properties and microstructure. Although hydrogen seems to have no significant influence on the relative density, the microstructure, and the phase composition, it can slightly increase the tensile strength and elongation at break in the as‐built state. A heat treatment of 250 °C can increase the elongation at the break without impeding the tensile strength.

While the functionality of textured surface is largely affected by the texturing quality, how to precisely fabricate honeycomb microstructures with high material utilization and structural stability is crucial for their application potential. In the present work, a strategy of preprogramming‐based in situ tailoring laser power in different pulses is proposed for improving the processing quality of honeycomb microstructures by nanosecond laser micromachining. Firstly, a finite element (FE) model of tailoring laser power based on the thermodynamic diffusion equation of nanosecond laser ablation is established. Secondly, the effects of different laser parameters on the processing quality of honeycomb microstructures are investigated by FE simulations and experiments, which derive the rational range of laser processing parameters for the highest surface quality. Thirdly, the effectiveness of in situ tailoring laser power is demonstrated through FE simulation and experiment. Finally, nanosecond laser micromachining experiments with the proposed scheme of in situ tailoring laser power are carried out, with which a significant 40% improvement in the processing quality of honeycomb microstructures is obtained. Current work provides a feasible solution for enhancing processing quality of complex microstructures by laser micromachining.

The present study reports for the first time, development of a novel technique to fabricate compositionally graded monolithic NiTi shape memory alloy (SMA) laminated hybrid composites by joining two compositionally different equi‐atomic Ni50Ti50 and Ni‐rich Ni51Ti49 SMAs. A two‐step fabrication methodology involving a combination of spark plasma sintering (SPS)/diffusion bonding at 1050 °C followed by hot roll bonding (HRB) at 900 °C is adopted to produce three‐layer SMA laminated composites in four different architectures, which can be utilized for manufacturing passive damping devices. Microstructural characterization clearly shows that HRB is capable of producing a joining interface free from any oxides/voids having excellent metallurgical bonding. The measurement of martensitic transformation characterized through differential scanning calorimetry of these NiTi SMA composites reveals that in spite of forming a monolithic SMA composite material after HRB, the individual NiTi SMA layers still preserve their individual transformation characteristics. Tensile tests carried out on HRB NiTi SMA composites at ambient temperature demonstrate that laminated NiTi SMA hybrid composite comprising top and bottom layers of Ni51Ti49 SMA and middle layer of Ni50Ti50 SMA (in equal thickness proportion) exhibits the best pseudoelastic strain recovery, which can be further improved by aging treatment at 425 °C for 15 min.

A detailed evaluation of various parameters that influence the lithium (Li)‐ion conductivity in Li7La3Zr2O12 is undertaken based on data from the literature. In particular, the importance of the dopant on the Li site, the ionic radius of the dopant, and the relative density of the compound are evident. The relative density can only be obtained from experimental measurements, which restrict the evaluation of unexplored dopants and their associated stoichiometry. The element embedding is utilized to generate 200D element representations that can obviate the need for hard‐to‐obtain descriptors. Different machine learning methods are evaluated for the prediction of superionicity of the compound for unknown dopants on the Li site and the F1 score of 0.81 using the K‐nearest neighbor classifier. Based on this analysis, new dopants and associated stoichiometry are suggested.

Excellent high‐temperature oxidation resistance for traditional high‐entropy alloys/medium‐entropy alloys (MEAs) is still a huge challenge. Herein, a novel Co51.3Ni19.5Cr19Al6.4Ti3.4Nb0.4 MEA with superior high‐temperature oxidation resistance is designed. The specific high‐temperature oxidation behaviors of the studied MEA are systematically investigated at 800, 900, and 1000 °C for 200 h. Specifically, the studied MEA remains a single face‐centered cubic (FCC) phase after solution treatment under vacuum at 1200 °C for 15 h, while high‐density L12 nanoprecipitates form inside the FCC matrix after aging treatment under vacuum at 750 °C for 12 h, revealing the consistency between the experimental results and the theoretical prediction. The results of oxidation tests indicate that the studied MEA with FCC matrix and L12 nanoprecipitates exhibits a superior oxidation resistance. The oxidation kinetics of the oxide layer follow a parabolic law at oxidation temperature of 800, 900, and 1000 °C and the corresponding oxidation rate constants (kp) are 0.001, 0.011, and 0.047 mg2 cm−4 h−1, respectively. The diffusion activation energy of the studied MEA is determined to be 258 kJ mol−1 and the oxidation process is controlled by outward diffusion of metallic elements and inward diffusion of oxygen. The research results provide guidance for the development of superalloys.

Herein, the impregnation dynamics of the space between rectangular, polymer‐coated copper hairpins in electric motors, using polyester‐based and epoxy‐based liquid resins, are described both experimentally and theoretically. The rectangular capillary is formed along its sides by two copper hairpins coated with a polymer, with paper along its bottom and air along its top. The following properties of the two test liquid resins are measured from 25 to 80 °C: their contact angles on the hairpin and on the paper, their dynamic viscosities, densities, and surface tension. Dynamic viscosity is modeled by the Vogel–Fulcher–Tammann model, while surface tension is modeled by the Eötvös model, used also to estimate the molar masses of the resins. Penetration times of the test liquids are measured into the capillaries for ten penetration lengths. A model is derived for the penetration length as a function of time for a liquid penetrating into horizontal, rectangular, and thin capillaries. The resulting model is similar to that of the Lucas–Washburn but the geometrical parameters differ. The temperature dependence of the penetration rate is modeled by the extended Vogel–Fulcher–Tamman model.

Magnesium (Mg) is an ideal choice in gastrointestinal anastomosis staples due to its well‐known biodegradability and biocompatibility. However, the low strength and poor formability of pure Mg pose challenges in the preparation of wire materials suitable for surgical staples, thereby limiting its application as staples in gastrointestinal surgeries. This study investigates the microstructural, mechanical, corrosion, biocompatibility, and antibacterial properties of Mg‐2Zn‐xCu alloys (x = 0.1, 0.6, 1.2 wt%) with emphasis on the possible application of Mg‐2Zn‐0.1Cu alloy wire as a biodegradable surgical staple. Mg‐2Zn‐0.1Cu alloy exhibits good mechanical properties (UTS of 234 MPa, EL of 17.7%) and low corrosion rate of 5.21 mm year−1 with good biosafety and antibacterial capability. Therefore, this alloy is chosen to prepare Φ0.25 mm wire with an excellent balance between tensile strength (274 MPa) and corrosion resistance. The wire bent at 30° maintains excellent structural integrity after immersion for 14 days. The B‐shape staple derived from this wire exhibits a strength of 0.8 N, underscoring the suitability of Mg‐2Zn‐0.1Cu as an outstanding material for surgical staples.

Mechanical metamaterials represent a promising class of materials characterized by unconventional mechanical properties derived from their engineered architectures. In the realm of bioengineering, these materials offer unique opportunities for applications spanning in vitro models, wearable devices, and implantable biomedical technologies. This review discusses recent advancements and applications of mechanical metamaterials in bioengineering contexts. Mechanical metamaterials, tailored to mimic specific mechanical properties of biological tissues, enhance the fidelity and relevance of in vitro models for disease modeling and therapy testing. Integration of these materials into wearable devices enables the creation of comfortable and adaptive interfaces with the human body. Utilization of mechanical metamaterials in implantable devices promotes tissue regeneration, supports biomechanical functions, and minimizes host immune responses. Key design strategies and material selection criteria critical for optimizing the performance and biocompatibility of these metamaterials are elucidated. Representative case studies demonstrating recent applications in benchtop phantoms and scaffolds (in vitro platforms); footwear, architectured fabrics, and epidermal sensors (wearables); and implantable cardiovascular, gastrointestinal, and orthopedic devices, and multifunctional patches are highlighted. Finally, the challenges and future directions in the field are discussed, emphasizing the potential for mechanical metamaterials to transform bioengineering research by enabling novel functionalities and improving outcomes across diverse use cases.

The purpose of this study is to investigate and analyze the preparation and application reliability of large‐size TA10/6061 explosive welding composite pipes. The results demonstrate that the AUTODYN numerical simulation of the composite pipe accurately reflects the actual explosive welding interface morphology, with both exhibiting waveform interfaces, indicating the favorable bonding morphology. The titanium elements at the composite pipe interface diffused into the aluminum side without forming intermetallic compounds. A substantial number of fine grains are generated in the titanium structure at the interface, enhancing the bonding strength. The microscopic analysis confirms the high bonding quality of the composite pipe. The composite pipe demonstrated high tensile and shear strength, which are 481.62 and 165.08 MPa, respectively, which are about 62.40% and 60.96% higher than that of single 6061 aluminum alloy, which exhibits high strength, significantly improved the ductility, and the ductile fracture failure modes. The titanium side, aluminum side, and interface demonstrated excellent bending resistance, with the highest hardness value observed at the interface and an increase in hardness on both the titanium side and interface in the direction of detonation.

To address the issue of high‐temperature corrosion of coal‐fired boiler water‐cooled walls, an Al–Si–Cr coating with rare earth element is developed using heat‐curing ceramic coating technology in this study. The corrosion resistance of both Al–Si–Cr and Ni–Cr coatings is investigated under laboratory and actual boiler conditions using X‐ray diffraction, scanning electron microscopy, and energy‐dispersive X‐ray spectroscopy. Results indicate significant coatings’ mass increase over time under laboratory conditions, with corrosion mass gain following a power function of time. The dense structure of the Al–Si–Cr coating and the rare earth elements effectively prevent the diffusion of corrosive gases, providing superior gaseous corrosion resistance. However, the dissolution of Al2O3 in high‐temperature molten salt causes cracks, reducing its resistance in such environments. Ni–Cr coating oxides react with corrosive gases, diminishing its resistance to gaseous corrosion. Nevertheless, Cr inhibits the sulfidation of Ni in molten sulfate and stabilizes NiO, enhancing its corrosion resistance in molten salt. The Al–Si–Cr coating demonstrates outstanding anti‐coking and corrosion resistance in the boiler. This study provides a promising new solution for enhancing the corrosion protection of water‐cooled walls in coal‐fired boilers.

The emerging metal‐fused deposition modeling (FDM) technologies offer economical and safe options for manufacturing metal structures with a high degree of flexibility. Great challenges still exist in fabricating metal structures using metal FDM without complicated debinding processes. This study shows that thin‐walled metal structures are fabricated by the combination of metal FDM and thermal debinding. The wall thickness needs to be less than 0.45 mm to avoid cracks and bloating deformation during thermal debinding with a heating rate of 1 °C min−1 in either vacuum environment or Ar gas environment. The stainless steel fabricated by the metal FDM without using debinding chemical reagents exhibits a yield strength of 189 MPa and an ultimate tensile strength of 407 MPa, which is comparable to the stainless steel fabricated by the metal FDM methods using debinding chemical reagents. In addition, the thin‐walled metal structure fabricated by the metal FDM possesses higher energy absorption capabilities than the metal structure fabricated by the laser powder bed fusion. These results are valuable for the further exploration of thin‐walled metal structures fabricated by the metal FDM without using debinding chemical reagents.

Three generations of advanced high strength steels (AHSS) have attracted considerable attention due to their excellent mechanical properties and relatively low cost. While there has been extensive research on the basic mechanical properties of AHSS, the impact energy absorption capacity, a critical property for ensuring passenger safety, has not been systematically investigated. In addition, the absence of standardized impact testing protocols for materials or structures hinders the comparison of results across different studies. The present review aims to provide a comparative analysis of the impact performance of thin‐walled structures and sheet specimens made from the three generations of AHSS. First, an introduction to the background of AHSS is presented. Widely used experimental techniques and specimen geometries are then reviewed. This is followed by a detailed review of recent relevant studies on the first, second, and third generations of AHSS. Emphasis is placed on investigating the influence of microstructure on impact performance and the underlying mechanisms governing high‐strain‐rate plastic deformation under impact loading. Various strategies to improve the impact performance of AHSS are also discussed.