Advanced Engineering Materials最新文献

In order to improve the corrosion resistance of micro-arc oxidation (MAO) ceramic layer of AZ31 magnesium alloy, a hydrophobic Mg–Al layered double hydroxide (LDH) coating was prepared on its surface by a one-step hydrothermal method. The microstructure of the coating was characterized by scanning electron microscope, energy disperse spectroscopy, X-ray diffractometer, and Fourier transform infrared spectrometer. The wettability and corrosion resistance of the coating were studied by contact angle (CA) measuring instrument and electrochemical workstation. Meanwhile, the durability of the coating was evaluated by sandpaper abrasion, tape peeling and immersion test. The results showed that the hydrophobic Mg–Al LDH coating can be successfully prepared on the surface of MAO ceramic layer by one-step hydrothermal treatment with alkaline aluminum nitrate solution containing sodium laurate. The hydrophobic Mg–Al LDH coating sealed the inherent defects of MAO ceramic coating, resulting in significantly improved corrosion resistance. With the extension of sandpaper abrasion distance, tape peeling times, and immersion time, the CA of the coating shows a downward trend, and the coating gradually changed from hydrophobic to hydrophilic. However, after the durability test, the coating still has good corrosion resistance, and its corrosion current density was still lower than that of MAO ceramic layer.

In this study, the effects of discontinuous precipitation, a process known to enhance mechanical properties in alloys, on the microstructure and mechanical properties of the (FeCoNi)₈₆Al₇Ti₇ high-entropy alloy (HEA) are investigated. Varying the aging temperatures leads to the formation of lamellar structures consisting of face-centered cubic (FCC) and body-centered cubic phases, which significantly influence the mechanical properties of the alloy. The aging treatments reveal an inverse relationship between temperature and microhardness, with values decreasing from 890 to 700 HV as the temperature rises from 550 to 650 °C. Despite this reduction, the alloy retains a high hardness level, suitable for wear-resistant applications. The best wear resistance is observed at 550 °C, with a wear rate as low as 8.45 ± 1.6 × 10⁻⁵ mm³ N⁻¹ m⁻¹. This is attributed to stacking faults and dislocations within the FCC lamellae, which enhance resistance to dislocation glide. In this study, the critical role of microstructural engineering in optimizing the properties of HEAs is highlighted, providing valuable insights for developing high-performance materials for specific engineering applications.

Room Temperature Thermal Energy Storage

In article number 2400012, Michael D. Toomey, Jaswinder Sharma, and co-workers demonstrate the first example of wet-spun PCM fibers comprised of a polymer sheath and a salt hydrate core for thermal energy storage applications. Fibers produced using this scalable production method achieve enthalpies of melting of ca. 130 J/g, melting onset at 29°C, and supercooling of 4.8°C while retaining 96.5% of its phase change capacity after 1000 cycles.

Ion doping is a feasible method to improve the mechanical and biological properties of hydroxyapatite (HA) as an implant coating material. F and Se codoped HA (SeF-HA) powder is synthesized with the method of chemical codeposition and directly used for coating preparation via suspension plasma spray technology. Various characterizations indicate that F and Se ions have been codoped into the HA structure by substituting OH⁻ and PO₄³⁻ groups, respectively. The SeF-HA coatings exhibit excellent adhesion strength with the substrate, fully meeting the ISO requirement of 15 MPa. The dissolution behavior is investigated by immersing the coatings in simulated body fluid for different durations. The results show that the dissolution rate of the SeF-HA coatings is lower than that of the single Se-doped HA coating, suggesting an improvement in the stability of the SeF-HA coating. The in vitro studies show that the SeF-HA coating can promote the osteogenic activity of osteoblasts and has an antiproliferative effect on osteosarcoma cells. Based on these results, it can be concluded that the combined effects of Se and F can make suspension plasma sprayed HA coating a potential coating material for dental implants or for bone tissue repair in osteosarcoma patients.

This study examines the development of TiN/SiO_x/Cu/SiO_x/TiN memristive devices for neuromorphic applications using wedge-type deposition and Monte Carlo simulations. Identifying critical parameters for the desired device characteristics can be challenging with conventional trial-and-error methods, which often obscure the effects of varying layer compositions. By employing an off-center thermal evaporation method, a thickness gradient of SiO_x and Cu on a 4 inch wafer is created, facilitating detailed resistance map analysis through semiautomatic measurements. This approach allows for investigating the influence of layer composition and thickness while keeping other process conditions constant. Combining experimental data with simulations provides a precise understanding of layer thickness distribution and its impact on device performance. Optimizing the SiO_x layers to be below 12 nm, coupled with a discontinuous Cu layer with a nominal thickness under 0.6 nm, exhibits analog switching properties with an R_on/R_off ratio of >100, suitable for neuromorphic applications, while R × A and power exponent γ analysis show signs of multiple conduction mechanisms. The findings highlight the importance of SiO_x and Cu thickness in determining switching behavior, offering insights for developing high-performance analog switching components for bioinspired computing systems.

Thermal paints are essential for mapping the surface temperature of gas turbine engine components but can only indicate maximum temperature. A novel transient thermal history sensor that combines the capabilities of a thermocouple with those of a thermal paint is developed here, enabling the retrieval of full thermal history using a “sintering” model. The glassy ceramic thermal paint undergoes a qualitative optical transition due to sintering in response to temperature that is quantified using UV–vis spectroscopy. This provides high-resolution transient temperature measurement (±6 °C) when maximum temperature is above its glass transition temperature (T_g) of 563 °C and up to 660 °C. The glass-ceramic coating exhibits strong adhesion to Inconel 718 substrates due to matched coefficients of thermal expansion. By fabricating similar paints with distinct temperature ranges and placing them in proximity, this approach can significantly reduce the number of thermocouples needed for surface temperature mapping, thereby improving the accuracy of measurements required for engine validation.

Zinc has a successful history of being a protective coating on a wide range of objects and in many exposure settings due to its strong corrosion resistance in most environments. Because zinc may produce dense, adhering corrosion byproducts, it is resistant to corrosion. The industrial applications of zinc are extensive. Due to their excellent properties, zinc-based coatings have garnered great attention in the modern world. The present study focuses on advances in surface modifications of zinc composite coatings through selective reinforcements. The study also includes a detailed description of recent experimental work conducted on zinc-based coatings. Various coating techniques and their advantages and limitations have been discussed along with the relevant parameters. Zinc and its alloys have been suggested as viable options for biodegradable metals recently because of their acceptable biocompatibility and preferred corrosion behavior. The use of zinc-based biodegradable materials in clinical applications like orthopedic and cardiovascular systems has also been discussed in detail. The current study also includes the latest developments in zinc-based biodegradable metals and the related surface modification techniques. Future perspectives on zinc-based alloys and their variety of applications have also been undertaken in the study.

The double-network (DN) concept, initially applied to hydrogels, has been adapted to elastomers, resulting in materials that combine exceptional toughness with tunable elasticity. This article delves into the constitutive and fracture behaviors of DN elastomers, elucidating the pivotal role of prestretch and composition in tailoring their properties. An incompressible hyperelastic model is employed to predict the stress–strain behavior and energy release rate of a DN elastomer, focusing on how the interactions between the two networks influence its overall material properties. The influence of prestretch and composition on increasing the stiffness and energy release rate of a DN elastomer is analytically determined. The analytical predictions are validated experimentally through comprehensive mechanical and fracture testing using a DN elastomer fabricated by a two-step crosslinking process to decouple the prestretch and composition. The results show that manipulating these processing parameters can finely tune the mechanical responses of DN elastomers, optimizing them for specific applications. The findings provide new insights into the mechanics of DN elastomers.

The ferroalloy powder (FeP) with remarkably high-magnetic permeability and high-temperature stability has attracted much attention for its potential application in the field of radar stealth. However, achieving high stealth performance in different frequency bands by controlling the shape of iron alloys remains a major challenge. Herein, FeP-filled high-density polyethylene composites with different FeP shapes by hot pressing are prepared. This work employs a straightforward vacuum hot-pressing molding technique to analyze the electromagnetic wave absorption property of composite materials utilizing two distinct forms of FeP as different fillers. It is noted that composites filled with 75 wt% spherical FeP with excellent impedance matching exhibit a minimum reflection loss (RL_min) of −60.75 dB at 12.23 GHz with a thickness of 2.55 mm, and a maximum effective absorption bandwidth of 8.31 GHz at 2.5 mm. While high-density polyethylene composites filled with 75 wt% flaky FeP obtain the RL_min value at a low frequency of 2 GHz because of the high magnetic loss. This work provides a guideline for developing applications of FeP-filled composites with different shapes.

The room temperature (RT) and high-temperature (373–573 K) hardness of individual phases of Ti₄₅Ni₅₀Fe₅ multiphase intermetallic are evaluated using nanoindentation. The B2 matrix exhibits anomalous behavior whose hardness decreases from RT to 373 K followed by an increase up to 573 K. In contrast, the hardness of the DO₂₄ phase continuously reduces up to 473 K. Molecular dynamics simulation of single crystal compression of B2 matrix shows the presence of $��\frac{1}{2}�⟨�\overline{1}�11�⟩�$ screw partial dislocations at all temperatures whose density increases up to 473 K followed by a decrease at 573 K. It is anticipated that individual screw super partial cross-slips from {110} to {211} plane at the higher temperature, with their core becoming nonplanar. The nonplanar core of these screw partials acts as a dragging point for the motion of dislocation leading to hardness anomaly vis-à-vis yield strength anomaly. The DO₂₄ phase does not exhibit any anomalous behavior in hardness in the studied temperature range due to the presence of super partial dislocations bounded by super intrinsic stacking faults instead of antiphase boundaries.