MetalMat最新文献

Metal matrix composites (MMCs) are attracting increasing attention owing to their high strength, thermal stability, and wear resistance, making them essential in industries such as aerospace, automotive, and energy. However, traditional manufacturing methods often face limitations in achieving the complex geometries and uniform reinforcement dispersion necessary to optimize the performance and reliability of the final product. To address these challenges, additive manufacturing (AM) has emerged as a promising approach offering enhanced design flexibility, precise microstructural control, and improved material efficiency. This study discusses the advantages of AM in MMC research and classifies AM-based MMC fabrication methods into three categories: (1) using reinforcement-dispersed metal powders, (2) co-feeding metal and reinforcement powders during AM, and (3) in situ formation of MMCs through reactive processes during AM. This review compares the characteristics and microstructural differences between these methods and highlights the mechanical and structural advantages of AM. Despite their potential, challenges, such as microstructural uniformity and process optimization, necessitate further research. Finally, future research directions for advancing AM-based MMC fabrication technologies are discussed.

Growing demand for secure, sustainable, and affordable magnetic materials has drawn significant attention to rare-earth-free Fe-based permanent magnets. This review integrates recent advances from atomic-scale theory to bulk processing. We first outline the fundamental parameters that govern permanent-magnet performance, such as saturation magnetization (M_s), magnetocrystalline anisotropy, Curie temperature (T_c), and microstructural factors. We then survey four principal material families. The first is Fe–Co alloys whose anisotropy is enhanced through lattice strain and light-element doping. The second is chemically ordered Fe–Ni, tetrataenite, originally discovered in meteorites. The third is nitrogen-rich iron phases typified by α″-Fe₁₆N₂. The fourth is iron phosphides and borides such as Fe₂P and Fe–B. Although calculations predict outstanding magnetic strength, experimental results remain limited by phase instability, grain-size effects, and processing constraints. To bridge this gap, we highlight four complementary research directions: strain engineering, heteroatom doping, deliberate microstructure control, and data-driven ab initio calculations. Coordinated progress in these areas could yield Fe-based magnets with high coercivity and robust magnetization, enabling practical devices for electrified transport, renewable-energy conversion, and compact electronics without costly rare-earth elements.

High-entropy materials (HEMs) have emerged as a novel class of functional materials that exhibit outstanding mechanical, thermal, and electromagnetic properties due to their unique atomic-scale features, such as high configurational entropy, lattice distortion, sluggish diffusion, and the cocktail effect. This review provides a comprehensive overview of recent progress in the synthesis, structure, and electromagnetic performance of HEMs, with a particular focus on electromagnetic wave absorption and electromagnetic interference (EMI) shielding applications. Unlike previous reviews that focused on specific material types or general trends, this work systematically analyzes all major categories of HEMs—including alloys, ceramics, and composites—by correlating synthesis methods, microstructural characteristics, and electromagnetic properties. By identifying structure–property–processing relationships, this review highlights key mechanisms driving electromagnetic performance and outlines current challenges and future research directions. This unified perspective aims to guide the rational design of next-generation HEM-based materials for advanced electromagnetic applications.

The emission of carbon dioxide (CO₂) and its impact on global warming have shown exponential growth in recent decades. Hence, the mitigation of CO₂ emissions is indeed important. Among the developed protocols, the selective and effective capture of CO₂ using porous materials is foremost. Though the porous materials demonstrated excellent CO₂ capture activity, the synthesis of those porous materials using chemical precursors limits their applicability. As a consequence, serious attention has been given to the synthesis of porous materials using biomass. Several biomass components have been reported to synthesize heteroatom-doped porous carbon (PC) materials, which proved to be an excellent adsorbent for CO₂ capture and conversion to utilitarian products. This review will focus on the different synthetic techniques reported for the synthesis of PC using biological materials. Here, we elucidate the synthesis of the heteroatom (N, S, P, O, B)-doped porous carbon materials. Furthermore, CO₂ capture has been discussed concerning the influence of pore size and heteroatoms. Lastly, the conversion of CO₂ to utility products has been covered. We foresee that the information gathered regarding the synthesis of PC using biomass and its conversion to utility products will provide a strong platform to researchers and learners.

Metal nanowires, as representative one-dimensional (1D) materials, have found widespread applications in electrocatalysis, energy storage, and flexible electronics. Despite the development of various synthetic routes, existing methods still suffer from limitations such as restricted compositional diversity and complex preparation procedures. Recently, a strategy based on the mechanochemical decomposition of MAX phase precursors has been proposed to accelerate the growth of metal whiskers, offering advantages such as rich compositional diversity, template-free operation, and procedural simplicity, thereby demonstrating promising application potential. However, the whiskers produced by this approach typically exhibit relatively large diameters, hindering their integration into miniaturized nanoscale devices. To address this challenge, this study introduces a liquid medium–assisted strategy to confine the diameter of Sn whiskers derived from Ti₂SnC, successfully synthesizing Sn nanowires with diameters as low as several tens of nanometers. Experimental results reveal that the liquid medium effectively suppresses the coalescence of metallic nuclei, reduces their initial size, and thereby facilitates the formation of finer whiskers. This strategy not only provides a new experimental foundation for understanding the geometry of A-site metal whiskers derived from MAX phases, but also offers a novel approach for the controlled synthesis of various nonprecious metal nanowires.

Thermochemical treatments performed at low temperatures (< ∼500°C) have received increasing interest for the surface modification of austenitic stainless steels. In fact, when treatment media rich in nitrogen and/or carbon are used at these temperatures, the formation of chromium compounds is inhibited and the interstitial atoms are retained in the face-centered cubic lattice of austenite beyond the solubility limit. The obtained supersaturated solid solution, known as expanded austenite or S-phase, has high hardness and can maintain or even increase the corrosion resistance in many environments. In the international literature, many studies are present that highlight the effects of the formation of this phase on tribological properties, fatigue resistance, corrosion behavior, wettability, biocompatibility, and magnetic properties of austenitic stainless steels. However, using analogous treatment conditions, expanded austenite can be obtained in many other alloys having a matrix with a face-centered cubic lattice, such as austenitic steels, nickel and cobalt alloys, and the more recent medium- and high-entropy alloys, but the studies on this topic are mostly at their very beginning. In this review, the characteristics and properties of expanded austenite and of the modified surface layers in which it is present are analyzed and discussed, considering all the different alloys in which this supersaturated phase can be produced. The role of alloy elements in promoting or hindering the formation of expanded austenite and the competing compound precipitates is taken into account. The opportunities and challenges of the low-temperature treatments are highlighted, and possible future directions for the investigation are suggested.

In the early 2000s, the soldering industry faced a major shift due to regulations restricting Pb usage. As a result, four main alloy systems emerged as alternatives: Sn–Bi, Sn–In, Sn–Cu, and Sn–Ag. However, for reasons not initially evident, higher melting point alloys were the first to be widely developed, most notably the Sn–Ag–Cu (SAC) alloys, which became the industry standard due to their balanced performance in reliability, mechanical strength, and process compatibility. Over the past decade, increasing emphasis has been placed on low-temperature soldering (LTS), requiring studies not only on defects such as warpage, interfacial pores, and joint strength but also on the fundamental melting and solidification behavior of these alloys. Sn–Bi alloys have emerged as a commercial alternative, particularly for consumer products such as clients and server computers, while maintaining compatibility with surface mount technology (SMT) technology for high-volume manufacturing. The thermal fatigue reliability of Sn–Bi is also well-recognized. This short review will provide an overview of various studies conducted on the solidification behavior of Sn–Bi based alloys. The solidification paths, eutectic formation, morphologies, and properties will be explored. Future research directions comprise microalloying insights to improve ductility, interaction between Sn–Bi solder balls and SAC (Sn–Ag–Cu) pastes to mitigate PCB warpage, and exploring advanced characterization techniques such as X-ray microtomography (XMT) and nanohardness testing. These developments are essential for optimizing LTS alloys and ensuring their reliability in next-generation electronic packaging.

Cobalt (Co) is a promising next-generation contact metal to replace tungsten for the system-large-scale integration devices beyond the 5 nm technology node due to its low resistivity and high gap-filling capability at high aspect ratios. To complete Co metallization, surface roughness control after chemical mechanical planarization (CMP) is critical because it directly influences contact resistance. However, a low removal rate during CMP hinders achieving low surface roughness. Here, we have designed the Co oxide layer with a unique oxidation state, crystallinity, and thickness to enhance the removal rate with low roughness. The physicochemical properties of a Co oxidant are controlled by the reduction potential and diffusion coefficient of the oxidant associated with the thermodynamics and kinetics, respectively. Co oxide layer with a dominant oxidation state of Co (II), an amorphous phase, and a thin thickness improves CMP performance. As a result, compared to the conventional metal CMP slurry with H₂O₂, the designed oxide layer increases the removal rate by 254% and reduces the surface roughness by 41%.