Papers by Keyword: Electromagnetic Properties

Abstract: Nowadays, many individuals utilize the 5G network, which can give detrimental effects due to electromagnetic interference (EMI). EMI may harm not only high-tech electronic devices but also human health. In this study, the porous carbon was synthesized from palm kernel shell (PKS) via hydrothermal treatment at varying temperatures (160 °C, 180 °C, and 200 °C) followed by carbonization, and comprehensively characterized to understand its structural, chemical, and electromagnetic properties. X-ray diffraction (XRD) revealed broad (002) and (100) peaks across all samples, indicating amorphous graphitic carbon with limited crystallinity. Fourier-transform infrared spectroscopy (FTIR) confirmed the presence of O–H, C–H, and C=C functional group. As the synthesis temperature increased, aromatic and graphitic characteristics became more pronounced, with 180 °C exhibiting a significant rise in C–H peak intensity. This suggests that 180 °C is an optimal carbonization temperature, promoting the formation or preservation of stable aliphatic structures without excessive degradation. Surface area analysis using the BET method showed that the sample treated at 180 °C exhibited the highest surface area (547.4 m²/g), suggesting optimal porosity formation. Scanning electron microscopy (SEM) supported this finding, showing a fragmented and open morphology at 180 °C, in contrast to denser, spherical agglomerates observed at 200 °C. Due to its characteristics, the 180 °C sample was selected for electromagnetic characterization. S-parameter measurements at X-band frequency for epoxy composites filled with porous carbon revealed that increasing filler content led to reduced transmission coefficient, indicating enhanced electromagnetic wave attenuation. These improvements are attributed to increased dielectric losses and interfacial polarization facilitated by the highly porous carbon network. In conclusion, the study highlights the significance of hydrothermal synthesis temperature in tuning the structure and electromagnetic performance of biomass-derived porous carbon.

Abstract: We investigate the predictive performance of specific analytical and numerical methods to determine the effective magnetic properties of two-phase steels at the macroscale. We utilize various mixture rules reported in the literature for the former, some of which correspond to rigorous bounds, e.g., Voigt (arithmetic) and Reuss (harmonic) averages. For the latter, we employ asymptotic homogenization together with the finite element method (FEM) and periodic boundary conditions (PBC). The voxel-based discretization of the representative volume element is conducted with digital image processing on the existing micrographs of DP600-grade steel. We show that unlike the considered isotropic mixture rules, which use only the phase volume fraction as the statistical microstructural descriptor, finite element method-based first-order asymptotic homogenization allows prediction of both phase content and directional dependence in the magnetic permeability by permitting an accurate consideration of the underlying phase geometry.

Abstract: Today, under the conditions of sanctions, the Russian Federation needs more than ever the development of energy-saving technologies in various industries. The greatest impact on the life and operability of hard alloy cutting tools is exerted by the physical and mechanical properties of tool materials. Studies have shown that the physical and mechanical properties of tungsten hard alloys in the process of operation, namely in the process of cutting difficult-to-process materials under the influence of high temperatures, vary symmetrically. This study was based on the laws of physics of the division of electrodynamics, as well as well-known non-destructive testing techniques, scientific foundations of materials science, all studies were carried out in accredited laboratories of Tyumen Industrial University. Results of research on determination of temperature of maximum operability of replaceable cutting hard-alloy plates based on study of change of electromagnetic properties are obtained. On the basis of persistent tests in factory conditions, it was proved that the developed technique allows determining temperature intervals of maximum operability based on the study of changes in electromagnetic properties of hard alloys.

Abstract: Porous Ni_0.5Zn_0.5Fe_2-xCr_xO₄ (x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5) ceramics were prepared by a sol-gel method using basswood as the mold. At the same time, Ni_0.5Zn_0.5Fe_2-xCr_xO₄ nanocrystalline powders were obtained by sintering the gel in oxygen at high temperature. The result of the XRD test showed that all samples presented the single-phase of the cubic spinel structure. With the increase of doping amount x, both porous ceramics and nanopowders decreased their grain size; At the same doping amount, the grain size of powder ferrites was about twice as large as that of porous ceramics. The magnetic test results showed that with the increase of doping amount x, the coercivity values increased monotonously and the saturation magnetization values decreased monotonously for all samples. Under the same doping content, the saturation magnetization values were lower but the coercivity values were higher as compared to the powder ferrites.

Abstract: CIP/ZnO electromagnetic functional composites with core-shell structure were prepared by chemical precipitation method, and then the morphology, structure and electromagnetic properties in 2-18GHz were characterized by X-ray diffraction, scanning electron microscopy and vector network analyzer, respectively. In process by controlling the component ratio between core and shell, it has been found that the more ZnO particles were coated on the CIP surface, the smaller electromagnetic parameters become. Based with the Electromagnetic Wave Absorption (EMWA) Theory, the composites could prepare EMWA building coating by monolayer design, the theoretical simulation results show that the minimum RL of CIP/ZnO composites is-10.25dB, better than pure CIP particles, exhibiting excellent EMWA properties in 2-18GHz. The magnetic loss of CIP and the dielectric loss of ZnO were the main mechanisms of EMWA for the CIP/ZnO composites, which could be used for electromagnetic radiation protection.

Abstract: In principle gravity will affect everything. Although practically negligible it is legitimate to inquire the effect of gravity on the electromagnetic properties of materials which can be expressed as the relation between (d,b) fields (electric displacement and magnetic induction) with the (e,h) fields (electric and magnetic field strength). A sample of material in a weak gravitational field is equivalent with placing the sample in an accelerating reference field (which is the statement of the equivalence principle). By using the relation between the accelerating frame with the inertial frame we can compute the electromagnetic properties with the assistance of CAS (Computer Algebra System) Reduce due to the tedious algebraic manipulations needed to accomplish the task. The linear and isotropic relation in inertial frame (free of gravity), although still linear, becomes unisotropic and mixed up between electric and magnetic fields.

Abstract: Impregnation method was used for fabricating Co/YIG (Y₃Fe₅O₁₂) composites under low temperature, and the electromagnetic properties were tuned by adjusting the content (0 wt% - 35 wt%) and microstructure of the metal in composites. The XRD and SEM were used to analyze the phase and microstructure. Electromagnetism properties including reactance, permittivity and permeability of the composites were tested using impedance analyzer (10 MHz~1 GHz). The results indicated that, the high cobalt content leads to the formation of three-dimensional cobalt networks on the pore walls of porous YIG gradually, and their electromagnetic properties have also been changed significantly with the Co content increasing. Especially, double negative properties were achieved in Co/YIG composites when the content of Co reached 35 wt% at the frequency band of 575 MHz-1 GHz. The appearance of double negative properties in cermets provides promising applications in electromagnetic stealth materials, microwave antenna, and traveling wave tubes.

Abstract: A new kind of organic prepolymer containing cobalt phthalocyanine ring (Co-FOM) was prepared by reaction from ferrocenyl organic magnetic prepolymer (FOM) and cobalt chloride. The structure of Co-FOM was characterized by Fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible spectrophotometry (UV-vis). The magnetic properties of Co-FOM exhibited stronger magnetism than FOM at room temperature. The maximum saturation magnetization of Co-FOM reached to 15.8 emu/g at the magnetic field of 5000 Oe. Meanwhile, Co-FOM had one resonance peak for dielectric loss and two resonance peaks for magnetic loss in 0.5-18 GHz. Furthermore, this kind of magnetic material had a strong reflection loss at higher frequency (around 17 GHz). So Co-FOM will have potential application in electromagnetic shielding area.

Abstract: In this work, novel Fe₃O₄–hyperbranched copper phthalocyanines (Fe₃O₄–CuPc) nanostructures were fabricated via a simple solvent-thermal method, and the electromagnetic absorption property of the composites was investigated. The introduction of CuPc molecules were not only attached to the surface of Fe₃O₄ in form of beads, but embedded in the interior of Fe₃O₄. Importantly, the Fe₃O₄–CuPc composites exhibit excellent microwave absorbability, compared with that of Fe₃O₄. The composites with a coating layer thickness of 4.0 mm exhibit a maximum absorption of –30.3 dB at 10.2 GHz and the bandwidth below −10.0 dB reaches up to 10.6 GHz (from 7.4 to 18.0 GHz range). The excellent microwave absorption properties are ascribed to the improved impedance matching. The as–prepared novel Fe₃O₄–CuPc composites are shown to be lightweight, strong absorption, and broad frequency bandwidth microwave absorbers.

Abstract: This paper presents results of the research project: "Characterization of the radio frequency (RF) properties of LDS-MID" where RF parameters of laser direct structureable (LDS) molded interconnect device (MID) materials were investigated. First of all the most important material parameters influencing the RF performance of a device are introduced. In the next section the broadband characterization of the metallization and material properties using a coplanar waveguide (CPW) is described. For a selected LDS material the conduction losses due to different metallization compositions are discussed in detail.