Advanced Engineering Materials最新文献

Silicone hydrogels are pivotal materials used in contact lenses, biomedicine, and electronic devices, where oxygen permeability and equilibrium water content (EWC) are essential attributes. Generally, an increase in silicone content boosts oxygen permeability but diminishes EWC, presenting a notable trade-off challenge. In this study, a solvent incorporation method that significantly elevates oxygen permeability without markedly affecting EWC is introduced. Among various solvents, isopropanol incorporation notably enhances oxygen permeability (101 barrer) while maintaining an EWC of 56.0%. This improvement is attributed to enhanced connectivity within the silicone network. Additionally, it is discovered that incorporating siloxane nanoparticles (SNPs) further increases the connectivity of the silicone network, offering a more pronounced improvement in oxygen permeability than solvent alone. However, excessive SNP addition can lead to large phase separation, resulting in decreased transmittance, lower EWC, and increased mechanical strength. Optimizing a transmittance of over 99%, SNP addition achieves a silicone hydrogel with an oxygen permeability of 125 barrer and an EWC of 49.5%, surpassing many advancements reported in the literature.

Hydrogen Detection

During the second industrial revolution, William H. Johnson investigated a mystery that affected the British metallurgy industry. He observed that cleaning rust from iron and steel wires with acidulated water reduced their original toughness via an embrittlement effect. Gas bubbles emerging from the wires’ cracks revealed the culprit: hydrogen. In article number 2400776, Matheus A. Tunes, Peter J. Uggowitzer, and co-workers discuss how detecting hydrogen in materials remains a challenge 150 years later.

Innovation and Excellence in Material Science

The cover photograph shows a collection of tools and samples that were essential during the career of Reinhard Pippan, involving differently sized HPT anvils, various fracture and fatigue specimens, an early dedicated in-situ testing device, and a broken ski pole of the jubilee ready for applied fracture research. More details can be found in the Guest Editorial by Daniel Kiener and Anton Hohenwarter (2401772).

Crevice corrosion for dissimilar metal contacts is a key problem in engineering applications. This work has attempted to prevent the ingress of corrosive media into the crevice between aluminum alloy and copper by controlling the roughness (machining accuracy) of the contact surfaces. Both electrochemical and alternating dry/wet immersion tests were used to investigate the corrosion resistance of aluminum alloy–copper contacts with different contact surface roughness. Considering the relationship between the contact surface roughness and the liquid–solid contact angle and the crevice width, a finite element model based on fluid dynamics theory is established to analyze the effect of the contact surface roughness on the seawater infiltration depth in the contact crevice. The distribution of corrosion products on the aluminum alloy and copper surfaces is observed by optical microscope and scanning electron microscope. The phase composition of the corrosion products is analyzed by X-ray diffraction technique. The results show that the corrosion resistance of the contact improves as the roughness of the contact surface decreases. This is attributed to the fact that the infiltration of seawater is retarded due to the decrease in the crevice width and increase in the contact angle with the decrease in the contact surface roughness.

In this study, we combined Li₂Mn₃ZnO₈ with MXene (Ti₃C₂T_x) to improve performance in supercapacitors and hydrogen evolution reactions. MXenes are known for their electrical conductivity and high surface area, making them promising for energy storage. The Ti₃C₂T_x/Li₂Mn₃ZnO₈ composite electrode showed a specific capacitance of 182 F g^-1 at 1 A g^-1, outperforming individual Li₂Mn₃ZnO₈ and MXene electrodes. Even after 3,000 cycles, the composite retained 71% of its initial capacitance. This research introduces innovative electrode materials for next-generation supercapacitors and hydrogen evolution applications, contributing to sustainable energy solutions.

Tungsten Fiber-Reinforced Composites

In article number 2400951, Johann Riesch, Maximilian Fuhr, and Jürgen Almanstötter present a review which illuminates the unlikely revival of tungsten wire, from its iconic role as coils in incandescent bulbs to its emerging applications in high-performance composites for nuclear fusion reactors. This includes new insights into its unique combination of strength, ductility, and high-temperature properties, which are key properties for the excellent fracture behavior of tungsten fiber-reinforced composites. The authors discover how this versatile material is being reengineered and what new applications are emerging from cutting-edge research.

To design metal materials that combine high-temperature strength with room-temperature ductility, three kinds of body-centered-cubic (BCC) refractory high-entropy alloys (RHEAs) with different Mo element contents are screened and prepared by combining several parameters. The room-temperature ductility and excellent high-temperature (1500 °C) mechanical properties are investigated. Combined with the microstructure test, the characteristic of fracture and deformation is also discussed. RHEAs studied herein have great compressive yield strength approximately ranging from 1324.5 to 1424.4 MPa with excellent compressive ductility ranging from 20.7% to 44.2% at room temperature. At 1500 °C, the yield strengths of three RHEAs are over 335.47 MPa at 10⁻³ s⁻¹ strain rate, which is rarely found in traditional metals materials. The excellent mechanical properties of these three RHEAs at both room and high temperature as a promising material are beneficial to future high-temperature application.

To gain insights into the microstructure evolution of as-fabricated Ni-based superalloys during post-heat treatments, a comparative microstructure analysis is made based on the AMSC-DB alloy samples fabricated by laser-directed energy deposition (L-DED) and forging. In L-DED samples, the (Nb,Ta)C carbides experience a continuous dissolution process during the solution treatment. In contrast, the coarsening behaviors of carbide particles in forge alloys are observed to take place simultaneously with their dissolution. Characterization results show that the carbides in L-DED alloy present uniformly distributed particle sizes and nodular shapes with much irregular surface curvatures. Also, less-pronounced Nb segregation behaviors in carbide vicinity are found in L-DED alloys. Therefore, the difference in carbide dissolution kinetics in L-DED and forge alloys can be ascribed to the combined effects of phase morphologies and local chemical driving forces. Correspondingly, the segmented changes in grain boundary misorientations and recrystallization process in forge alloys are observed to be highly coupled with the carbide dissolution behaviors, compared to the continuous microstructural evolution in L-DED alloy. The different recrystallization behaviors can be quantitatively reflected by the Zener pinning effect. This work sheds light on the proper design of post-heat treatments for L-DED alloys compared to the traditionally manufactured counterparts.

It is known that the grain size plays a major role in the mechanical properties of magnesium. The aim of the present study is to evaluate its role in long-term corrosion rate. Samples of pure magnesium with grain sizes in the range of 0.9–82 μm are produced through severe plastic deformation and annealing treatments. The mechanical properties are evaluated using tensile tests and the corrosion behavior is evaluated using immersion tests in Hank's solution. A maximum yield stress of ≈150 MPa is observed in the sample with 1.8 μm of grain size and an elongation larger than 25% is observed in the ultrafine-grained sample. Ultrafine- and fine-grained magnesium display uniform corrosion with a decreasing corrosion rate while coarse-grained magnesium displays localized corrosion with an accelerated corrosion rate. A corrosion rate of ≈0.2 mm year⁻¹ is observed in the ultrafine- and fine-grained magnesium. The corrosion product layer of the fine-grained magnesium contains elements absorbed from the media. An analysis of the data in the literature suggests that grain refinement changes the corrosion type from localized to uniform corrosion. The exact relationship between grain size and the corrosion rate remains elusive.

Laser powder bed fusion (LPBF) of rare-earth-modified high-strength aluminum alloys presents a novel approach for manufacturing complex components with enhanced structural performance, particularly in aerospace applications. This study fabricates Al–Mg–Sc–Zr specimens using various powder spreading parameters to explore their impact on laser processability. The investigation reveals that varying the powder layer thickness from 30 to 70 μm yields the smallest irradiation diameter of 135 μm at an optimal thickness of 50 μm, attributable to effective multiple reflections, high laser absorption rates, and stability. With an optimal laser power of 400 W, a scanning speed of 600 mm s⁻¹, and a hatching spacing of 60 μm, the sample produced at 50 μm layer thickness achieves a relative density of 99.23%, a top surface roughness of 15.42 μm, and a refined grain size of 1.67 μm. Following aging at 325 °C for 4 h, this sample exhibits a tensile strength of 518 MPa and an elongation of 15.6%. The findings establish a theoretical basis for controlling the morphology and properties of high-strength aluminum alloys in laser additive manufacturing.