Absorption Applications Research Articles

Design and tuneable magnetodielectric ferrite-based meta-absorbers for high-frequency microwave absorption applications

EM absorbers with outstanding absorption, shielding capability, and dissipation performance are still challenging in hostile environments. To address the EMI issues, the meta-absorbers of the spinel-based structure were designed and prepared. Herein, Zr-In co-substituted Ni-Zn nano ferrites with the composition of Ni0.7Zn0.3(ZrIn)xFe2–2xO4 for 0≤x≤0.20 with 0.05 step size were prepared using the citrate-gel self-ignition route. The characteristic features of the Zr-In doped NiZn nano ferrites were evaluated from FESEM, XRD, FTIR, and VSM, respectively. The bond lengths and unshared-shared edges in Zr-In doped NiZn ferrite were estimated using the Bertaut method. FTIR analysis confirms the occurrence of phase in Zr-In co-substituted Ni-Zn ferrite. The micrographs of Zr-In doped NiZn ferrite show circular and hexagonal mixed-shaped particles. SFD and high-frequency response from the Zr-In doped NiZn ferrites were evaluated. NiZn ferrite shows higher SFD at the high-frequency response than Zr-In doped NiZn ferrite. The dielectric measurements were captured using VNA in the frequency range from 1 GHz to 6 GHz. The minimum reflection loss of -61.5 dB at 2.43 GHz was observed for the x = 0.20 sample. However, the reflection loss of -57.3 dB at 1.93 GHz was achieved for the x = 0.15 sample. Metaabsorbers of rod-like Zr-In doped NiZn were designed and simulated. The absorption resonance peak was observed at 5.8 GHz with maximum absorptivity for Zr-In doped NiZn absorber at x = 0.15, respectively. The present study reveals the planer and rod-like prepared EM irradiated Zr-In doped NiZn meta-absorber are suitable for SFD, MLCI's high-frequency EMI shielding applications in C band applications.

Effects of different atomic passivation on conductive and dielectric properties of silicon carbide nanowires

Based on the transport and polarization relaxation theories, the effects of hydrogen, fluorine, and chlorine atom passivation on the conductivity and dielectric properties of silicon carbide nanowires (SiCNWs) were numerically simulated. The results show that passivation can decrease the dark conductivity of SiCNWs and increase its ultraviolet photoconductivity. Among them, the photoconductivity of univalent (H) passivated SiCNWs is better than that of seven-valent (Cl, F) passivated SiCNWs. In terms of dielectric properties, the passivated SiCNWs exhibit a strong dielectric response in both deep ultraviolet and microwave regions. Hydrogen passivation SiCNWs produce the strongest dielectric response in deep ultraviolet, while fluorine passivation SiCNWs produce the strongest dielectric relaxation in the microwave band, which indicates that atomic passivation SiCNWs have a wide range of applications in ultraviolet optoelectronic devices and microwave absorption and shielding.

Morphology dependent EMI shielding performance of Ag-Ni core-shell nanowires

The proposed work reports a facile chemical reduction method for synthesizing the hierarchical silver-nickel core-shell nanowire structures with controllable morphologies by varying the Ag concentration. The growth of Ni shells around the Ag core to make thorny and smooth Ag-Ni core-shell nanowires is studied for addressing electromagnetic interference (EMI). The synthesized Ag-Ni nanowires show better EMI shielding effectiveness (SE) than Ni nanowires with much-improved absorption loss (SEA). Due to high electrical conductivity (8630 S cm−1), magnetic permeability (44.1 emu/g), and heterojunction core-shell interfaces, the bimetallic nanowires flakes exhibit exceptional average EMI SE of 90.5 dB in the X-band frequency range (8–12 GHz) with a thickness of 0.11 mm, taking specific EMI SE to 822.72 dB/mm. In addition, the EMI shielding performance of the smooth Ag-Ni nanowires showed a 45% enhancement in SEA with marginal change in reflection loss (SER) compared to the thorny ones, indicating high absorption of EM waves. The unique core-shell nanowires with high aspect ratio with tunable physical properties can be ideal candidates for futuristic applications in microwave absorption and electromagnetic interference shielding.

Isotropic cellular structure design strategies based on triply periodic minimal surfaces

Isotropy is a desired characteristic in cellular structures for load bearing and energy absorption applications that must respond uniformly under external loads in all orientations. Triply periodic minimal surface (TPMS) cellular structures are attracting much attention for such applications due to their demonstrated high performance, tailorable properties, and open cell architecture. However, TPMS structures usually display stiffness anisotropy. In this work, new design strategies are presented for isotropic TPMS-based cellular structures, revealing a large available design space in terms of relative density and relative stiffness. The first design strategy arranges TPMS-based cells in a Simple-Cubic/Face-Centred Cubic inspired pattern, resulting in reduced elastic anisotropy. Two parametric optimisation approaches involving level-set mid-surface offsetting and the functional grading of relative density are then applied in a second step to eliminate any residual elastic anisotropy. Anisotropy is characterised through finite element analysis using the Zener ratio. Four families of cells are optimised, each based on a different TPMS unit cell, and then additively manufactured using the material extrusion process with polylactic acid. Finally, experimental quasi-static compressive tests are conducted to characterise stiffness, strength, and energy absorption properties. Optimised designs are tested in three crystal orientations ([001], [101] and [111]) and manufactured in three orthogonal print orientations. The Primitive TPMS-based design is the stiffest of the four designs reaching 64.4% of the Hashin-Shtrikman upper bound of bulk modulus at 20% relative density. Experimental results validate all four optimised cell designs for elastic isotropy and indicate that all the cell designs are also isotropic in terms of crushing strength and energy absorption.

Heterointerface regulation of core-shell FeSiAl magnetic powders by in situ oxidation as high-efficiency absorbers

Developing electromagnetic (EM) absorbers that are highly efficient across a wide bandwidth is a significant hurdle in mitigating the growing issue of EM pollution emanating from the increasing prevalence of electronic and telecommunication devices. When considering the applications of absorbers in high-temperature environment, ensuring both structural and chemical stability becomes crucial. Incorporating a magnetic core and dielectric shell within core-shell structures appears to be a promising strategy for addressing this challenge. In this work, we have successfully synthesized the core-shell FeSiAl@oxide composites through in situ oxidation process, which offers a facile route for significantly enhancing their EM absorbing performance by promoting multiple interfacial polarizations and achieving ideal impedance matching. A systematic analysis has been conducted to uncover the morphological and microstructural evolution of the FeSiAl@oxide composites, shedding light on their EM properties. The remarkable EM dissipation capacity of these composites, owing to the strong synergistic effects between magnetic and dielectric losses, has been demonstrated with the minimum absorption of −41.7 dB over an impressive absorption bandwidth of 7.92 GHz at 2.5 mm.

Integrated MCDM techniques for the selection of hybrid MWCNT/Ni–Zn–Fe nanocomposites for X-band radar absorption applications

In the 21st century, microwave-absorbing materials are used in a wide range of applications, such as in anechoic chambers and as electromagnetic interference shielding materials in radar and wireless communications. The design and development of new microwave-absorbing materials require substantial resources such as time, raw materials, and energy, and need to be cost-effective. Judicious selection of radar-absorbing materials from available alternatives often becomes difficult because it involves conflicting and non-commensurate attributes, such as bandwidth, reduced reflection loss, and thickness. This study aims to design and select novel double-layered multi-walled carbon nanotubes (MWCNT)/ Ni–Zn–Fe (NZF) microwave-absorbing materials using multi-criteria decision-making (MCDM) techniques such as TOPSIS, VIKOR, and PROMETHEE-II. Single-layered microwave-absorbing materials with various compositions of MWCNT and NZF were prepared using a low-cost and facilein-situpolymerization process. The multi-layered radar-absorbing materials reflection loss was determined using transmission line theory. Subjective and objective criteria weights from the analytical hierarchy process, entropy methods, and their calculated combined weights were utilized to implement the MCDM techniques. The combination of MWCNT/NZF radar-absorbing materials was chosen using integrated MCDM methods as the preferred microwave-absorbing material with a reflection loss of −15 dB for a 2.6 GHz bandwidth and a maximum reflection loss of –22 dB at 9.6 GHz in the X-band.

Manipulating the phase and morphology of MgFe2O4 nanoparticles for promoting their optical, magnetic, and microwave absorbing/shielding characteristics

Morphology and phase regulation shed light on the tuning of microwave absorbing characteristics, as well as magnetic and optical features. Not only is the development of electromagnetic wave absorbing materials the best way to equip us against harmful electromagnetic waves in the technology era, but the widespread applications of microwave absorbers in military and civilian fields have also enhanced their importance. Hence, MgFe2O4 nanoparticles were synthesized, and then (1) its main crystalline phase was divided into Mg, Fe2O3, and Fe3O4, and (2) its morphology was manipulated to evaluate the influence of morphology and phase on the microwave absorbing performance, optical characteristics, and magnetic capability. The novel precursors, along with modified sol-gel and solvothermal scenarios, were applied to regulate the structures toward strengthening the features. Interestingly, polyethylene terephthalate (PET) was chosen as the recyclable plastic to fabricate the final composites to evaluate the microwave absorbing/shielding characteristics due to its fascinating susceptibilities as building materials, minimizing environmental hazards and implementing green and sustainable manufacturing. Noticeably, Mg/Fe3O4/PET nanocomposite gained a brilliant RL of −95.50 dB at 21.80 GHz meanwhile the one-pot-synthesized Fe2O3/MgFe2O4 composited by PET attained a maximum RL of −71.32 dB at 23.06 GHz and an ultra-high efficient bandwidth (RL ≤ −20 dB) of 8.50 GHz with only thickness of 0.50 mm. Interestingly, the PET-based microwave absorbers were fabricated with a low filling ratio of 10 wt%. More significantly, the samples illustrated proper shielding efficiency, desirable for practical applications in the modern era.

Recyclable flexible materials with MOF-derived nanospheres for electromagnetic wave absorption

Self−healing and recyclable characteristics were beneficial for wave−absorbing materials to extend the service life, reduce the cost, stability and electromagnetic pollution in the practical application. The flexible composites with recyclable and electromagnetic wave (EMW) absorption were fabricated by employing MOF derived carbon nanoparticles (ZnCoNC) and polymers with dynamic boron ester bonds. The benzene structure of eugenol derived polybenzoxazine structure can stick on the surface of the MOF−derived nanoparticles by π−π interaction, which benefits the recyclable and mechanical properties. With the synergistic effect of dynamic boron ester bond and π−π interaction, the tensile strength of composites with 15 wt% ZnCoNC reached 7.88 MPa after 3 times recycling, it remained 88 % compared to origin composites. The minimum RL obtained is −36.6 dB at a thickness of 2 mm, it can approximately maintain the same effect in EMW absorption performance after recycling. This work was expected to broaden the EMW absorption application field and extend the service life of materials.

Simple preparation of SiC@SiO2 nanofiber with bead-like structure by microwave sintering

SiC@SiO2 nanofiber material holds great potential for a wide range of applications in microelectronic devices and electromagnetic wave absorption. However, its development has been hindered by high energy consumption (＞1500 °C) and complex fabrication methods. This work introduces a sample approach to produce the SiC@SiO2 nanofiber at temperature of ∼1000 °C by using microwave heating. The SiC@SiO2 nanofiber possess a unique bead-like structure, which are composed of single-crystalline SiC nanowires and amorphous SiO2 beads. The growth mechanism under the action of microwave was explained. Moreover, the SiC@SiO2 nanofiber exhibits an Excellent electromagnetic wave absorption performance with a minimum refection loss (RLmin) value of −36.54 dB. The successful preparation of SiC@SiO2 nanofiber provides a new idea for preparing ceramic materials with low cost and high efficiency in the future.

A Liquid‐Metal‐Assisted Competitive Galvanic Reaction Strategy Toward Indium/Oxide Core−Shell Nanoparticles with Enhanced Microwave Absorption

AbstractThe preparation of core–shell structured nanoparticles using the galvanic replacement reaction of liquid metals is a simple and efficient method. However, precise modulation of the core and shell components to regulate the microwave absorption performance still needs to be further explored. In this study, various types of indium/oxide core–shell nanoparticles are prepared based on a competitive galvanic reaction of gallium‐indium liquid metals. The prepared indium/oxide core–shell structured nanoparticles exhibit superior electromagnetic (EM) wave absorption properties with a minimum reflection loss (RL) of −40.25 dB at 1.7 mm and the widest effective absorption band of 6.12 GHz at 2.1 mm. The superior wave‐absorbing properties originate from the dielectric losses of the interfacial and dipole polarizations. In addition, an externally applied magnetic field improves the polarization loss and microwave dissipation to achieve a minimum RL of −45.65 dB at 2.4 mm. The liquid‐metal‐assisted competitive galvanic reaction strategies extend the variety of core–shell structured nanoparticles for electromagnetic wave absorption applications.

Ni-PI-Ni based nanoarchitectonics near-perfect metamaterial absorber with incident angle stability for visible and near-infrared applications

This article presents a wideband metamaterial absorber (WMMA) for the visible and near-infrared (NIR) region application. The proposed metamaterial absorber comprises three layers of sandwiched (metal-dielectric-metal) model based on Nickel-Polyamide-Nickel. The multiple resonators on top layers achieve an average absorption of 98.16% over a range from 380 to 2300 nm with a compact unit cell size of 100 × 100 × 42 nm3. The designed WMMA shows 99% perfect absorption for a large bandwidth of 685 nm. Considering its wideband absorption, the physical absorption phenomenon was also explained in terms of the proposed WMMA's surface electric field, magnetic field, and current distribution. Also, the effects of materials and structural parameters on absorption performance with a FOM have been studied. The absorption performance is analysed with various polarization angles to demonstrate polarization insensitivity. The designed WMMA shows the absorption of >70% at large incident angles of 70°. The perceptible contribution of this WMMA is large unity absorption bandwidth at visible to NIR region with high incident angle stability, polarisation insensitivity, thermal robustness of the constituting metal and simple nanostructure geometry. Therefore, the proposed WMMA has good potential in sensors, thermal emitters, photodetectors, and absorber applications.

Constructing graphene-based aerogel with bi-continuous interpenetrating networks as a multi-functional microwave absorber

The design of three-dimensional networks in graphene-based aerogels is an effective strategy for fabricating a lightweight microwave absorber with strong absorption and broad effective bandwidth. Herein, a multi-functional aerogel with bi-continuous interpenetrating networks comprised of reduced graphene oxide (RGO) and cellulose nanofiber (CNF) was developed via an “ice-dissolving” (freezing and solvent exchange) and subsequent annealing strategy. Different from the conventional step-by-step construction of two independent networks, the bi-continuous interpenetrating networks were simultaneously built in a one-step freezing process. Notably, the network structure of the aerogel can be tuned by adjusting the concentration of CNF (CCNF) during the freezing stage. When the CCNF increased from 2 to 8 wt%, the network structure transitioned from a single three-dimensional RGO skeleton to ordered bi-continuous interpenetrating networks, and then to a disordered CNF/RGO mixed network. The mutual contributions from the RGO skeleton and CNF network endowed the aerogel (14.96 mg cm−3) with improved conduct loss and optimized characteristic impedance, leading to an excellent microwave absorption capacity. Consequently, the aerogel achieved a maximum reflection loss of −68.3 dB and an effective bandwidth of 6.9 GHz, respectively. Moreover, the unique network structure also enabled the sample to have superior noise absorbing performance (normalized absorption coefficient of 0.894 in 250–6300 Hz) and good structural stability. This strategy provides a facile avenue for constructing multi-functional aerogels with bi-continuous interpenetrating networks for both microwave absorption and noise absorption applications.

Dielectric, physicochemical, and reflection loss features of Gd-substituted W-type hexaferrites for microwave absorption application

Dielectric, physicochemical, and reflection loss features of Gd-substituted W-type hexaferrites for microwave absorption application

Synthesis of metallic-phase MoS2 nanospheres with high microwave absorbing performance

Metallic phase of MoS2 (M−MoS2) is a metastable state that does not occur naturally. To the best of our knowledge, there has been no prior preparation of pure and stable M−MoS2 nanospheres. The high purity, uniform, and stable two-dimensional M−MoS2 nanospheres were synthesized in ethyl alcohol through a hydrothermal reaction in this study. The as-prepared M−MoS2 demonstrates excellent microwave absorbing performance (MAP), with a minimum reflection loss (RL) of −39.88 dB at a thickness of 1.3 mm and an effective attenuation bandwidth (RL < -10 dB) up to 8.31 GHz (9.6875–18.0 GHz). These results suggest that M−MoS2 is a promising and cost-effective option for microwave absorption applications.

Structural, morphological, dielectric, and spectral properties of Sr-Mg-Ho X-type magnetic nano materials suitable for microwave absorption application

Holmium (Ho3+) substituted Sr2Mg2Fe28O46 X-type hexa-ferrites were synthesized using the sol-gel auto-combustion route. The single phase of Sr2Mg2Fe28-xHoxO46 where 0.00 ≤ x ≤ 0.20, Δx = 0.05, X-type hexa-ferrites was confirmed using XRD peaks. The crystalline size was studied from XRD data and found to be in the 11 nm–24 nm range. The micro strain increased with the substitution of Ho3+. FTIR exposed the specific stretching vibration and absorption peaks in the 400 cm−1 - 600 cm−1 range. The force constant (ko) decreased from 1.74 N/cm to 1.65 N/cm with the increasing concentration of Ho3+. The grain size range is 371–493 nm, measured by SEM analysis, and plate-like structure plays a crucial role in enhancing the permeability of magnetic material. Transmission electron microscopy (TEM) analysis showed the hexagonal structure of X-type ferrites (x = 0.20). The results of the X-ray photoelectron spectroscopy (XPS) experiment confirmed the presence of all metal ions in the given composition with their required valences. The dielectric constant, dielectric loss, and tangent loss are found to increase with the substitution of the Ho3+ ion. In addition, the higher values of dielectric parameters and dielectric loss suggest that the material may suitable for high-frequency applications and best for microwave absorbers. Our aim is to discuss the characteristics and applications of microwave absorption materials, understand their behavior, and contribute to the development of upcoming novel devices. The resonance peak's appearance shows that these materials are best for multilayer chip inductors and EMI attenuation.

Single-frequency fiber lasers based on metal thiophosphites with sub-kHz linewidths.

Metal thiophosphites (CrPX4) (X = S and Se), emerging layered metal chalcogenophosphate materials, have found extensive utility in the fields of advanced electronic devices, magnetic technologies, and electrochemical systems. However, their applications in single-frequency fiber lasers have been relatively limited. Here, liquid phase exfoliation technology is used to exfoliate the CrPX4 into few-layered samples. Subsequently, we explored the application of CrPX4-based saturable absorbers (CrPX4-SA) by precisely depositing CrPX4 nanosheets onto the surface of D-shaped fibers. This led to the successful creation of two stable single-frequency fiber lasers (SFFLs) based on CrPS4 and CrPSe4 with center wavelengths of 1550.068 nm and 1550.092 nm, respectively. The linewidth of CrPSe4 was tested and determined to be roughly 375 Hz, which is the narrowest ever value attained for an SFFL based on its structure, and its signal-to-noise ratio (SNR) was 74.17 dB. The maximum output power of each oscillator was 0.796 mW and 0.963 mW, and their corresponding power fluctuations were 2.5% and 1.4%, respectively.

Analysis of the operation and reсovery capacity of a magnetic fluidless shock absorber

This paper presents an analysis of the application of fluidless magnetic absorbers (FMA) in automotive suspensions and examines their performance. Various magnet arrangements and the influence of spacer thickness on energy recovery efficiency were studied. The results confirm the high efficiency and potential of using FMA in modern automotive suspensions. This article is published based on the results of scientific research conducted within the framework of the grant competition for scientific research conducted by scientific and pedagogical workers of SPbGASU (St. Petersburg State University of Architecture and Civil Engineering) in 2024. Keywords magnetic absorber, fluidless magnetic absorber, electromagnetic absorber, suspension, damping, modeling, energy recovery

The roles of templates consisting of amino acids in the synthesis and application of gold nanoclusters.

Gold nanoclusters (AuNCs) with low toxicity, high photostability, and facile synthesis have attracted great attention. The ligand is of great significance in stabilizing AuNCs and regulating their properties. Ligands consisting of amino acids (proteins and peptides) are an ideal template for synthesizing applicative AuNCs due to their inherent bioactivity, biocompatibility, and accessibility. In this review, we summarize the correlation of the template consisting of amino acids with the properties of AuNCs by analyzing different peptide sequences. The selection of amino acids can regulate the fluorescence excitation/emission and intensity, size, cell uptake, and light absorption. By analyzing the role played by AuNCs stabilized by proteins and peptides in the application, universal rules and detailed performances of sensors, antibacterial agents, therapeutic reagents, and light absorbers are reviewed. This review can guide the template design and application of AuNCs when selecting proteins and peptides as ligands.

АНАЛИЗ ВИБРАЦИЙ И ИХ ВЛИЯНИЕ НА РАБОТУ МЕХАТРОННЫХ СИСТЕМ

The paper considers vibration as a critical factor affecting the performance of mechatronic systems. The study covers the nature and sources of vibrations, their effects on various components and on the accuracy of system functioning. Techniques for modeling vibration processes are described, as well as ways to minimize them, including the application of shock absorbers and active control. The results of experimental studies are presented and the prospects for further developments in the field of vibration protection of mechatronic systems are analyzed.

Design and performance evaluation of low-volatility and low-viscosity absorbent for CO2 capture

Deficiencies such as high viscosity, volatility, and rich phase precipitation limited the engineering application of non-aqueous absorbents. A series of high boiling point solvent screening experiments were conducted to develop...