Microwave Absorption Properties of Spinel‐Structured Mg–ZnAl2O4

Magnetic materials have a very broad application prospect in the field of microwave absorption, among which soft magnetic materials become the focus of magnetic materials research because of their high saturation magnetization and low coercivity. FeNi3 alloy has been widely used in soft magnetic materials because of its excellent ferromagnetism and electrical conductivity. In this work, FeNi3 alloy was prepared by the liquid reduction method. The effect of the filling ratio of FeNi3 alloy on the electromagnetic properties of absorbing materials was studied. It is found that the impedance matching ability of FeNi3 alloy is better when the filling ratio is 70 wt% than that of other samples with different filling ratios (30-60 wt%), showing better microwave absorption characteristics. When the matching thickness is 2.35 mm, the minimum reflection loss (RL) of FeNi3 alloy with a 70 wt% filling ratio reaches -40.33 dB, and the effective absorption bandwidth is 5.5 GHz. When the matching thickness is between 2 and 3 mm, the effective absorption bandwidth ranges from 7.21 GHz to 17.81 GHz, almost covering the whole X and Ku bands (8-18 GHz). The results show that FeNi3 alloy has adjustable electromagnetic properties and microwave absorption properties with different filling ratios, which is conducive to selecting excellent microwave absorption materials.

This study presents the utilization of mill scale waste, which has attracted much attention due to its high content of magnetite (Fe3O4). This work focuses on the extraction of Fe3O4 from mill scale waste via magnetic separation, and ball milling was used to fabricate a microwave absorber. The extracted magnetic powder was ground-milled using two different techniques: (i) a conventional milling technique (CM) and (ii) mechanical alloying (MM) process. The Fe3O4/CM samples were prepared by a conventional milling process using steel pot ball milling, while the Fe3O4/MM samples were prepared using a high-energy ball milling (HEBM) method. The effect of milling time on the structural, phase composition, and electromagnetic properties were examined using X-ray diffraction (XRD) and a vector network analyzer (VNA). XRD confirmed the formation of magnetite after both the magnetic separation and milling processes. The results revealed that Fe3O4 exhibited excellent microwave absorption properties because of the synergistic characteristics of its dielectric and magnetic loss. The results showed that the Fe3O4/CM particle powder had a greater absorption power (reflection loss: <−10 dB) with 99.9% absorption, a minimum reflection loss of −30.83 dB, and an effective bandwidth of 2.30 GHz for 2 mm thick samples. The results revealed the Fe3O4/MM powders had higher absorption properties, including a higher RL of −20.59 dB and a broader bandwidth of 2.43 GHz at a matching thickness of only 1 mm. The higher microwave absorption performance was attributed to the better impedance matching property caused by the porous microstructure. Furthermore, the magnetite, Fe3O4 showed superior microwave absorption characteristics because of the lower value of permittivity, which resulted in better impedance matching. This study presents a low-cost approach method by reutilizing mill scale waste to fabricate a high purity crystalline Fe3O4 with the best potential for designing magnetic nano-sized based microwave absorbers.

Electromagnetic properties and microwave absorbing characteristics of doped barium hexaferrite

Preparation and microwave absorption mechanisms of the NiZn ferrite nanofibers

Polymer‐derived ceramics (PDCs) are typically prepared as ceramic‐based microwave absorption materials by doping with high‐dielectric materials or transition metals, which may lead to the issue of uneven mixing. This study achieves uniform blending at the molecular level by using poly(dimethylsilylene)diacetylenes (PDSDA) to modify hyperbranched polyborosilazane (PBSZ). The alkynyl group and Si−H bonds crosslink to form a ceramic precursor, which is then pyrolyzed to prepare SiBCN ceramics with excellent microwave absorption performance and high temperature stability. The introduction of PDSDA significantly improved the ceramic yield, resulting in the in situ formation of more ordered carbon, SiC nanocrystals, and ceramic nanowires within the SiBCN ceramics. These nanophases are uniformly dispersed throughout the ceramic matrix, enhancing the ceramic's dielectric loss and microwave absorption properties. After pyrolyzed at 1400°C, the ceramic derived from the precursor with a PBSZ:PDSDA mass ratio of 10:1 exhibits excellent electromagnetic wave absorption properties, with a minimum reflection loss of −50.11 dB and a maximum effective absorption bandwidth of 3.11 GHz. Moreover, ceramics maintain excellent stability at 1500°C in both argon and air environments. This study fully exploits the designability of precursor molecules, providing a new approach for the preparation of microwave absorption materials from PDCs route.

Anion vacancy engineering represents an effective strategy to construct built-in electric fields (BIEFs) for the purpose of modulating electromagnetic (EM) properties. However, the in-depth and systematic comparative analysis of the effects of various anionic vacancies on defect-induced polarization is still lacking. In this work, the effects of defect-induced polarization resulting from group VA anion vacancies, particularly phosphorus vacancies (VP), are compared to the anion vacancies of other elements. The EM property modulation mechanisms and quantitative structure-property relations of NiCo0.5Fe0.5P1-x with varying contents of VP are investigated. It is concluded that the high content of VP establishes more intense BIEFs, forming permanent induced dipoles that function as polarization centers, thus enhancing defect-induced polarization and improving permittivity and dielectric loss. NiCo0.5Fe0.5P1-x3 with a high content of VP exhibits significant reflection loss (RL) with multi-band compatibility and wide effective absorption bandwidth (EAB) covering the whole X-band. This work offers a constructive perspective on the exploration of anionic vacancies from group VA, particularly VP, in modulating EM properties. Additionally, it addresses the issue of incompatibility associated with multi-band strong microwave absorption (MA) and offers a viable strategy for designing advanced metal phosphide MA materials.

Electromagnetic wave absorption properties of nickel-containing polymer-derived SiCN ceramics

Yttrium-substituted Co0.5Ni0.5YxFe2-xO4 ferrites as microwave absorbers by investigating structural, magnetic, dielectric, and absorption characteristics

A nickel coating on the surface of alumina particles, used as a reinforcement in metal-ceramic composite materials, its dielectric and electromagnetic properties have important application value. In this paper, nickel was deposited on alumina powder surface by the way of hydrothermal and sintering. The results showed that the nickel powders were fcc structure. The size of the crystal grains ranged from 10 nm-50 nm. The electro-magnetic characteristics were measured by HP 8722ES microwave net work analyzer in the band of 2-18 GHz. It was showed that both the Ni-Al203 and Co-Al203 nanopowders had low dielectric constant, low electromagnetic and good properties in microwave absorption.

Excellent microwave absorption of Y2Fe15.5Co0.5Si/paraffin composites by tuning powder particle size

Effect of milling on dielectric and microwave absorption properties of SiC based composites

The concept of producing structure–function integrated wave‐absorbing ceramics by combining three‐dimensional (3D) printing with the precursor conversion method has sparked extensive discussion and research. However, the synergistic enhancement of both the mechanical and electromagnetic (EM) properties of structural wave‐absorbing ceramics remains an area requiring further exploration. In this study, we employed the direct ink writing (DIW) process and polymer‐derived ceramics (PDCs) method to fabricate SiOC/SiCN composites with excellent mechanical and EM properties, modified by the polymer infiltration pyrolysis (PIP) process. The results demonstrated that PIP significantly improved the mechanical properties of SiOC/SiCN composites. After one cycle of infiltration pyrolysis, the compressive strength of the material was 6.3 times that of the unmodified state, and after three cycles, the compressive strength reached 10.13 MPa, which was 12.8 times that of the original. Furthermore, after three cycles of infiltration pyrolysis, the material exhibited effective absorption across the entire X‐band range (8.2–12.4 GHz) for thicknesses of 4.0 mm and 4.5 mm, with a minimum reflection loss (RLmin) of −64 dB, showcasing excellent wave‐absorbing capabilities. This study provides an innovative solution for the synergistic enhancement of both mechanical and EM properties in structure–function integrated wave‐absorbing ceramics.

Synthesis and electromagnetic absorption properties of CeO2@Fe composites with core-shell structure

The review addresses the effect of various carbon and iron-based percentage nano- additives on both electromagnetic (EM) wave and mechanical properties of composite materials. It also assessed the influence of particle and fiber size along with the manufacturing process, on mechanical properties (tensile strength and flexural strength), fracture behaviors (fracture toughness) and electromagnetic properties (reflection loss). Reviewing the selection of nanomaterials for a particular frequency band and application, as well as their impacts on bulk materials in relation to loading, were overviewed. As per this review, adding those iron and carbon-based additives influence positively for both electromagnetic and mechanical properties. Furthermore, review organized natural based fiber and filler-based composites along with fillers for the production of green strong radar materials. The review also showed, how highest and smaller percentage of iron-based fillers affected for microwave absorption and mechanical properties. Mainly, the optimized use of nano particles percentage for both mechanical and electromagnetic wave to produce strong radar materials were overlooked. Finally, these papers give a quick hint on how these nano particles manufacturing methods and particle size affect the mechanical properties and micro wave absorption of composite materials.

A novel microwave absorption material of Ni doped cryptomelane type manganese oxides