Microstructure Design of High-Entropy Alloys Through a Multistage Mechanical Alloying Strategy for Temperature-Stable Megahertz Electromagnetic Absorption

Abstract

Developing megahertz (MHz) electromagnetic wave (EMW) absorption materials with broadband absorption, multi-temperature adaptability, and facile preparation method remains a challenge. Herein, nanocrystalline FeCoNiCr0.4Cu0.2 high-entropy alloy powders (HEAs) with both large aspect ratios and thin intergranular amorphous layers are constructed by a multistage mechanical alloying strategy, aiming to achieve excellent and temperature-stable permeability and EMW absorption. A single-phase face-centered cubic structure with good ductility and high crystallinity is obtained as wet milling precursors, via precisely controlling dry milling time. Then, HEAs are flattened to improve aspect ratios by synergistically regulating wet milling time. FeCoNiCr0.4Cu0.2 HEAs with dry milling 20 h and wet milling 5 h (D20) exhibit higher and more stable permeability because of larger aspect ratios and thinner intergranular amorphous layers. The maximum reflection loss (RL) of D20/SiO2 composites is greater than − 7 dB with 5 mm thickness, and EMW absorption bandwidth (RL < − 7 dB) can maintain between 523 and 600 MHz from − 50 to 150 °C. Furthermore, relying on the “cocktail effect” of HEAs, D20 sample also exhibits excellent corrosion resistance and high Curie temperature. This work provides a facile and tunable strategy to design MHz electromagnetic absorbers with temperature stability, broadband, and resistance to harsh environments.

In‐Situ Fabrication of Sustainable‐N‐Doped‐Carbon‐Nanotube‐Encapsulated CoNi Heterogenous Nanocomposites for High‐Efficiency Electromagnetic Wave Absorption

“…[16,17] However, magnetic metals, especially for nano-or microscale magnetic metal particles, are easily oxidized and prone to agglomeration, which degrades the attenuation capability to EMWs. Even if alloying strategy [18][19][20] can improve the oxidation resistance due to high Curie temperature, challenges also exist in constructing robust, stable, and durable magnetic composites. The carbon encapsulation protocol thus attracts more and more attention to achieve magnetic composite.…”

Status and Prospects of High-Entropy Materials for Lithium–Sulfur Batteries

“…HEAs and other HEMs have potential development abilities and broad application prospects, resulted from the unique design strategies and unique properties. As shown in Figure 3, for example, NH3 decomposition reaction [36], Hydrogen Evolution Reaction (HER) [37], Lithium−sulfur Batteries(LSBs), Oxygen Reduction Reaction (ORR) [38], Methane Oxidation Reaction (MOR) [39], Formic Acid Oxidation Reaction (FAOR) [40], CO Oxidation Reaction [41], Methanol Oxidation Reaction [42], electromagnetic wave shielding materials [43], functional coating and antibacterial materials, hydrogen storage materials, anti-radiation materials, thermoelectric materials, etc., which are expected to be widely used in various new fields.…”

Efficient and Homogeneous Carbonitriding of High-Entropy Alloys by a Mechanochemical Process for Obtaining Coordinated Electromagnetic Matching

“…Due to their unique microstructure and multiprincipal components, HEAs demonstrate substantial benefits in enhancing dielectric loss, fostering high-frequency magnetic loss, and enhancing impedance matching. Usually, the permeability of EMA materials is significantly less than the permittivity, and enhancing the permeability is the key to improving impedance matching and achieving excellent EMA performances. − The high resistivity resulting from the severe lattice distortion effect of HEAs can help to reduce the complex permittivity to enhance impedance matching and EMA efficacy. − …”