Journal of Materials Science最新文献

High entropy alloys (HEAs) represent an innovative approach in alloy design, characterized by the incorporation of multiple principal elements and a wide array of compositional possibilities. Variations in the type and concentration of alloying elements have been found to modify the coatings' crystal structure, thereby influencing their mechanical and tribological characteristics. The addition of metallic elements (e.g., Cu, Nb, Mo, Ti, Al) has been found to modify the phase structure and grain size of the coatings. Furthermore, the inclusion of non-metallic elements (e.g., C, N, Si, B) and ceramic reinforced particles (e.g., TiN, TiB₂, WC) primarily enhance wear resistance by the formation of reinforcing phases. The primary objective of this work is to investigate the mechanisms by which alloying elements modify the friction and wear properties of HEACs. Furthermore, this work explores the potential applications of HEACs, aiming to establish a theoretical framework to guide future research and practical developments.

The Janus MoSSe monolayer has garnered significant attention due to its asymmetry structure and its ability to enhance out-of-plane piezoelectricity. As a two-dimensional transition metal dichalcogenide (TMD) material, MoSSe exhibits a notable sensitivity to gases, attributed to its unique structural composition, which enables specific interactions between the substrate and gas molecules. We investigate the interaction between CO₂, N₂, and the Janus MoSSe using density functional theory. The adsorption performance of pristine, defective and O-doped MoSSe is analyzed and compared. Additionally, the defective MoSSe shows higher adsorption energy than its pristine counterpart, accompanied by a reduced gas-to-surface distance. Variations in the state and charge transfer of electrons between bilayer MoSSe, N₂, and CO₂ are also discussed to understand the mechanisms of gas adsorption.

Inverse opals are characterized by their continuous porous structures, which endow them with natural structural colors. The functionalization of inverse opals can be achieved either by modifying and loading functional materials onto their porous framework or by constructing them directly from materials with the desired functionalities. For fabricating fluorescent inverse opals, a common method involves adsorbing or incorporating fluorescent materials into the porous matrix. However, it relies on intermolecular forces such as electrostatic interactions and hydrogen bonding, which may sometimes lead to insufficient binding strength. Herein, fluorescent molecules are directly polymerized into the hydrogel matrix of inverse opal, achieving one-step fabrication of fluorescent inverse opal. The modification based on chemical bonds effectively ensures robust binding stability, while retaining the structural color of photonic crystals. Leveraging the hydrogel’s reversible volume changes and the varying polarity of the molecular chain groups, the resulting inverse opals exhibit responsive behavior to ethanol solutions of varying concentrations and fatty alcohols with different carbon numbers. The study paves the way for harnessing the combined effects of fluorescence and structural color of inverse opals, suggesting their potential in a range of applications including solvent detection, drug delivery, and beyond.

Graphical Abstract

Solid-state cooling technology based on electrocaloric effect (ECE) has attracted worldwide attention due to its high efficiency, environmental benign nature, and cost effectivity. Although different forms of EC materials, i.e., ceramic bulk, multilayer ceramic capacitor, thin film, etc., have applied for EC applications, the impact of different structures on EC performance has not been thoroughly determined. In this study, ceramic bulks and multilayer ceramic capacitor (MLCC)-structured EC materials are directly compared with the same composition of 0.92Pb(Mg_1/3Nb_2/3)O₃-0.08PbTiO₃(PMN-8PT). In order to further figure out the performance improvement caused by geometric design, the dielectric layer thicknesses and layer numbers of MLCC structures were varied, while the same effective working volume was maintained. Both indirect and direct measurements were utilized for comparative EC performance analysis of ceramic bulk and multilayer structures. It was observed that MLCC samples with 6 dielectric layers exhibited an enhanced breakdown strength of 142 kV cm⁻¹, achieving enhanced electrocaloric performance of ΔS = 0.979 J kg⁻¹ K⁻¹ and ΔT = 1.285 K. These results indicate that when the effective cooling volume maintains equivalent in ferroelectric materials, the MLCC samples with reduced dielectric layer thickness exhibit an enhancement in the EC performance. It could be concluded that the MLCC structure would be beneficial for high EC performance, especially in terms of practical applications.

Layered double hydroxides (LDHs) are recognized as a promising material for the prevention of corrosion in metals and their alloys due to their unique structure, composition, controllability and anion exchange properties. However, traditional LDHs can only serve as a physical barrier for short-term protection. To provide additional intelligent self-healing functions, LDHs loaded with corrosion inhibitors have been developed to enhance the protective ability of the coating and improve the durability of the metal matrix. Despite this progress, there is currently a lack of a complete review summarizing the status of different types of LDHs nanocontainers and control of corrosion inhibitor release behavior. This paper reviews recent advancements in metal corrosion protection using LDHs loaded with corrosion inhibitors, including the preparation process and anti-corrosion mechanism of LDHs loaded with corrosion inhibitors. Additionally, factors affecting the release behavior of corrosion inhibitors are analyzed, and existing problems and future development trends are proposed and discussed.

Gradient nano-grained (GNG) high-entropy alloys (HEAs) generally exhibit an excellent balance of plasticity and strength compared to homogeneous alloys, but their mechanical behaviors vary significantly with grain size distributions. This work has systematically investigated the mechanical behaviors and deformation mechanisms of GNG Al_0.1CoCrFeNi HEAs with various grain-size gradients using molecular dynamics. The results have indicated that the grain-size gradient induces stress and strain gradients, and results in more dislocations and a unique multiaxial stress state, which contribute to the strength-plasticity synergy in the GNG structure. The deformation mechanism of GNG Al_0.1CoCrFeNi HEA involves dislocation slip in low strain level, martensitic transformation, and twinning in high strain level. The GNG Al_0.1CoCrFeNi HEA with a grain size gradient rate of n = 3 exhibits the best strength-plasticity synergy due to its significant strain and stress gradients, alongside notable deformation-induced twins and martensite. These simulation results are consistent with the strain gradient theory and some experimental reports.

Laser additive manufactured high γ′-phase nickel-based superalloys have a high cracking susceptibility due to the unique characteristics of superalloys, which can hinder their widespread application. This work overcomes the above challenges via a compositional optimization strategy, and a novel nickel-based superalloy with high γ′ phase has been developed via laser directed energy deposition (LDED). The effects of the various Al + Ti (1:1) contents (6.4, 6.6 and 6.8 wt.%) on microstructure and mechanical properties (room temperature, 850 °C and 900 °C) of the as-deposited and heat-treated specimens were investigated. Ultimately, the crack-free Ni-based superalloy has been successfully designed and fabricated by LDED, featuring a high γ′ phase content. The results indicated that the γ′ phase content and the number of the MC carbide particles increase with the increasing Ti + Al content. When the Ti + Al content is 6.6 wt.%, the newly designed Ni-based superalloy exhibits exceptional tensile properties (UTS: 1450 ± 42 MPa, YS: 1100 ± 36 MPa and EL: 16.5 ± 1.1%). After heat treatment, the γ′ phase, bulk-like (MC), long strips-like (M₂₃C₆) carbide and moderate amount of needle-like σ phase are present in the alloy with Ti + Al content of 6.6 wt.%. Therefore, the newly designed Ni-based superalloy exhibits superior tensile properties at 850 °C (UTS: 818 ± 34 MPa, YS: 774 ± 29 MPa and EL: 10 ± 0.7%) and 900 °C (UTS: 581 ± 28 MPa, YS: 558 ± 20 MPa and EL: 11.7 ± 0.9%). This approach provide a new alloy design route for achieving optimization of high-temperature mechanical properties and formability of nickel-based superalloys with high γ′ phase for laser additive manufacturing.

To strengthen the toughness of thermosetting resins under low temperatures, tetrafunctional epoxy-modified silicone resins (TESR-1/4/9) with different lengths of flexible chains were synthesized and served as tougheners for the epoxy system. The chemical structures of TESR-1/4/9 were determined via Fourier transform infrared spectroscopy as well as nuclear magnetic resonance (¹³C-NMR and ¹H-NMR). At room temperature, with 10 wt% of TESR-1, the elongation at break of the epoxy resin (17.67%) was added up to 68.93% in comparison with neat epoxy resin (10.46%). At −70 ℃, with the content of 5 wt% TESR-4, the value of the elongation at break (12.66%) was 37.31% higher than that of the neat epoxy (9.22%). A scanning electron microscope was utilized to observe the fractured surfaces of the resins to investigate the toughening behaviors of the tougheners (TESR-1/4/9). The dynamic mechanical analysis also demonstrated the improvement of the epoxy resins in toughness and good compatibility between TESR-1/4/9 and the epoxy matrix. These research findings can offer a new perspective for the enhancement of epoxy resins in low-temperature toughness.

Graphical abstract

With the continuous development of new energy storage technologies, the graphite anode used in lithium-ion battery anode materials has approached its theoretical specific capacity. The search for anode materials with higher specific capacity has received widespread attention. High-entropy alloy is a new type of material with excellent properties, such as its excellent mechanical properties and thermal stability. Compared with bielemental metal materials, the synergistic action of various elements in high-entropy alloys can effectively improve the lithium/potassium storage efficiency of the materials. In this work, Co_0.2Sb_0.2Fe_0.2Mn_0.2Ni_0.2 high-entropy alloy carbon nanofiber (HEA-CNFs) used as electrode for lithium/potassium ion batteries (L/PIBs) showed an ultra-high specific capacity of 1400 mAh g⁻¹ after 800 cycles at 0.5 A g⁻¹. Besides, as a self-supporting PIBs anode, HEA-CNFs showed a reversible capacity of 280 mAh g⁻¹ after 200 cycles at a current density of 0.2 A g⁻¹, revealing the huge potential of potassium storage. Compared with Co_0.5Sb_0.5 carbon nanofiber, HEA-CNFS can obtain better electrochemical properties. The high-entropy structure is conducive to improving the diffusion rate of lithium/potassium ion, enhancing the specific discharge capacity and cycle stability of the material. This work provides guidance for the preparation and development of high-entropy materials.