Dielectric Parameters Research Articles

Gold Nanorod-Induced Effects in a Mesogenic Compound 4-(trans-4-n-Hexylcyclohexyl) isothiocyanatobenzene.

Gold nanorods (GNRs) have a capsule-like structure with different optical properties than spherical gold nanoparticles due to surface plasmon resonance. Liquid crystals (LCs) are mesogenic compounds having crystal-like orientation and liquid-like fluidity. They are important materials from a technological point of view. Both GNRs and LC compounds are anisotropic in shape and properties. Different nano entities show interesting results when dispersed in different liquid crystalline materials which are instrumental from the application point of view. In the present work, GNRs have been dispersed in nematic liquid crystalline materials, namely 4-(trans-4-n-hexylcyclohexyl) isothiocyanatobenzene (6CHBT). Calorimetric, texture, spectroscopic, and dielectric studies were carried out for a pure 6CHBT and its composites with GNRs. Different calorimetric and dielectric parameters such as transition temperature, enthalpy, heat flow, permittivity, dielectric strength, dielectric anisotropy, and relaxation frequency have been determined, and the effect of GNRs has been explored. This article gives an insight into the influence of GNRs on the morphology and anisotropic physical properties of the nematic liquid crystalline material.

Effect of laser repetition rate parameter in pulsed Laser ablation for synthesis Li4Ti5O12 polyether sulfone nanocomposite for optoelectronic applications

We examine Li4Ti5O12 (LTO) anode component inserted into PES produced by pulsed laser ablation in liquid media method with adjustable its particle size by tuning laser repetition rate, followed by post irradiation, to investigate the capability for using in Rechargeable lithium-ion batteries applications. Thermal analysis illustrates how material characteristics change with temperature. X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and energy dispersive spectra (EDS) are used to assess the compound's phase composition, optical characteristics, and elemental analyses. Without any usual peaks for other impurities, notably rutile and anatase TiO2, the XRD pattern showed a cubic spinel structure with high crystallinity of just LTO structure. The sample's component elements are confirmed by the EDS spectra since only the peaks for the impurities Ti and O could be seen in the spectra. FT-IR revealed that the broad absorption bands appeared at wave numbers in the figure print region because of the stretching vibrations of the octahedral groups (MO6) lattice. The XPS survey spectra reveal the presence of Li, Ti, O, C, and S. TGA revealed that the interaction of hydroxyl groups of PES with functional groups of LTO via hydrogen bonding may result in a temperature shift of breakdown. Electrical conductivity measurements were conducted at various frequencies and temperatures. The generated samples' real and imaginary parts of dielectric parameter characteristics were tested at frequencies ranging from 0.1 to 3 M Hz and temperatures ranging from 200 to 500 K. The temperature variation of the real component of the dielectric constant indicates that these compounds have high electromagnetic absorption and wideband electrical activity.

UV accelerated aging of RTV/SiO2 nanocomposites: Study on surface microstructure, hydrophobicity, and electrical properties

RTV-SiR coatings are widely used to preserve ceramic insulators in high voltage power lines. These coatings enhance insulators’ resistance to environmental factors, such as contamination and moisture, as well as UV irradiation. The functional lifespan of RTV-SiR could be improved via addition of different nanoparticles such as SiO2. In this research, the effect of nano silica content on surface microstructure, hydrophobicity, and electrical properties of RTV-SiR before and after UV irradiation was studied by FESEM, AFM, surface roughness, contact angle, hydrophobicity transfer ability, dielectric parameters, and electric resistance. Results demonstrated that the optimal percentage of filler in the composite could make an appropriate surface roughness and increases hydrophobicity. Also, the excessive destruction of the RTV-SiR caused by UV irradiation is prevented by nano silica. Moreover, the contact angle of the coating reached the first level in a shorter period of time after applying pollution thanks to the presence of nano silica. Eventually, composite samples illustrated better performance than pure RTV-SiR, and the best properties were observed in samples containing 3 wt% silica.

Impact of High Heat Treatment on Ferroelectric Materials Properties: Ba1−xSrxTiO3 as a Model

Ferroelectric materials differ from other dielectrics because their polarization stays after removing the external field. Hysteresis loops describe a wide range of behavior in engineering, chemistry, and physics disciplines. Sol-gel has prepared barium strontium titanate (Ba0.7Sr0.3TiO3; BST) nanocrystalline ceramics. Ba1-xSrxTiO3 crystal size increased as the sintering temperatures elevated from 900 °C to 1200 °C. The XRD patterns of Ba0.7Sr0.3TiO3 exhibited a tetragonal phase. (FESEM) used to measure the average particle size. The relationships between crystal size, dielectric and ferroelectric properties were investigated, showing better dielectric and piezoelectric parameters with increasing crystal and particle size. The increasing particle size also slightly shifted the curie transition temperature towards higher temperatures. The coercive field of Ba0.7Sr0.3TiO3 goes down as the crystal size increases, but the remnant and spontaneous polarization get better. This material is advantageous for applications in tunable capacitor devices.

Water State in Hemoglobin Solutions: Microwave Dielectric Spectroscopy Study

In this review, we discuss the dielectric relaxation of water in the Hemoglobin (Hb) aqueous solutions in different states (MetHb, OxyHb, and DeoxyHb)). The interpretation of the results was performed by the 3D trajectory approach, which considers dielectric parameters of water relaxation and protein concentration. It has been shown that the interaction of amino acid dipole residues, located on the surface of a protein macromolecule, with water dipoles determines the protein hydration. In addition, ions of the buffer, in which proteins are dissolved, are also hydrated. The transition from a dipole-ion interaction of water molecules to a dipole-dipole interaction of water with an increase in protein concentration is observed. We proposed a new approach to calculate hemoglobin hydration shells. The theoretical model defines the change in the ratio between the content of free and bound water molecules (BWM) as a function of MetHb concentration in ion-free and ion-containing aqueous solutions. It considers the number of positive and negative charges at the surface of the protein molecule, the number of BWMs in its hydration shells, and the partition of water molecules bound to MetHb and the inorganic ions. The theoretical evaluation of the ratio of free-to-bound water reveals that, in the absence of ions, MetHb binds about 1400 water molecules, which is in good agreement with experimental data. At MetHb concentrations close to physiological, Hb is dominating in binding water over the inorganic ions, and the amount of BWM remains at the level of ~20% of total cytosol water as the concentration of Hb increases above 15 g/dL. These results suggest that in the physiological concentration diapason (29 - 35g/dL), molecules of MetHb are so close together that their hydration shells interact and shrink from four to one layer of water molecules. In contrast, Hb molecules aggregate to neutralize their surface charges mutually.

Impact of Gamma-Irradiated SiR-Al2O3 Nanocomposites and Degradation Diagnosis Using LIBS Method

The present study elucidates the impact of gamma irradiation on the thermal properties of silicone rubber nanocomposite insulation. Contact angle measurements, water droplet-initiated corona discharge studies and laser-induced breakdown spectroscopy (LIBS) studies are combined to provide a better understanding of the materials dielectric and thermal properties subjected to different irradiation dosages. The results show that the contact angle and the water-droplet initiated corona inception voltage decrease with increasing nanofiller content and gamma irradiation dosage. Analysis of the dielectric properties of the material following gamma irradiation, shows that the Cole-Cole double relaxation model fits well with the permittivity measured at different temperatures for both virgin and gamma-irradiated specimens. The coefficient of thermal expansion, deduced from the measured dielectric parameters, decreases with the increase of alumina nanofiller content and with the dosage of gamma irradiation. LIBS studies indicate that the ablation depth of the virgin and gamma-irradiated specimens becomes smaller when the filler content is increased. The coefficient of thermal expansion correlates directly with the plasma temperature measured using LIBS spectra of the nanocomposite material for non-irradiated and irradiated specimens.

Optimal design of high voltage composite insulators with grading rings in different configurations

Reliability of high voltage composite insulators depends on achieving an optimal electrical and geometrical design that produces the lowest electric field strength. This paper proposes a method to find the optimal geometrical design of composite insulators for different voltage levels. The design variables of the insulators include dimensions and locations of sheds and grading rings, as well as physical properties of the insulators. One composite insulator with single grading ring and two with double grading rings are considered and optimized. Considering the complexity of modifying composite insulator parameters to find the lowest electric field strength, five different optimization algorithms are applied and compared to find the optimal geometric design. The main objective of these optimization algorithms to be minimized is the maximum electric field strength, which is calculated using the finite element method-based COMSOL Multiphysics. The results for three different composite insulators under study show that the particle swarm optimization (PSO) algorithm produces the best results in terms of optimal geometrical design to minimize the electric field strength. In addition, the optimal design can reduce not only the electric field strength in clean, uniform pollution and water droplets environmental conditions but also the creepage distance of composite insulators. These improvements in optimized models are achieved without introducing any additional consideration besides the optimal dimensions.

Melamine-ethylene glycol co-assisted synthesis of magnesium manganese doped nano-ferrites and its effect on magnetic properties

The synthesis of magnetic nanoferrites with excellent physicochemical properties is of great research interest. In the current investigation, magnesium manganese-doped nano-ferrite material (Mg0.9Mn0.1Fe2O4) was prepared via a simple and low-temperature “sol–gel auto-combustion” method assisted by ethylene glycol (EG) and melamine (Mel). Herein, a series of five magnesium manganese ferrite materials were synthesised by varying the ratio (1:0, 1:3, 1:1, 3:1, 0:1) of EG to Mel. The magnetic properties are confirmed from the vibrating sample magnetometer (VSM) analysis; interestingly, the enhancement of the saturation magnetization (Ms) and lower coercivity were found by improving the Mel content with EG. Also, the dielectric characteristics and parameters, such as the dielectric constant (ε') and dielectric loss, have been investigated as a function of frequency. In addition, the surface chemical nature and high crystallinity were confirmed by FT-IR spectra and XRD analysis, respectively. The size of nanoparticles calculated using XRD-analysis indicated the range of synthesised nanoparticles is 17 to 22 nm, whereas the morphology of the material using FESEM was found to be dense and spherical in shape. A comparative analysis was also done to examine the effect of crystallinity and Mel/EG content on the magnetization of the synthesised material. The present ferrite material, which is synthesised at a relatively lower temperature exhibits comparable magnetization to that of reported high-temperature calcined nanoferrites.

Influence of gamma rays on the optical characteristics of CPVC/Ag nanocomposite film

In the current study carboxylated polyvinyl chloride/silver (CPVC/Ag) nanocomposite film was prepared. Samples from the CPVC/Ag nanocomposite film (1.5cm × 1.5 cm) were treated with 25–200 kGy gamma dosages. The optical characterization of the treated films has been investigated considering dosage by applying UV spectroscopy and colour difference studies. The optical bandgap, refractive index, Urbach energy, optical dielectric parameters, chromaticity coordinates, tristimulus values, colour intensity and colour intercepts have been calculated and interpreted based on gamma dosages. The bandgap decreased from 4.14 to 3.87 eV with augmenting the gamma dosage upto 200 kGy, together with a rise in the Urbach energy. This is attributed to the domination of crosslinks which damage the crystalline phase. Moreover, the non-treated CPVC/Ag is practically transparent. It demonstrated kindliness to change in colour by gamma treatment, as the colour intensity reached a value greater than 5, meaning permanent colour changes.

Effect of CuO addition on the structural, electrical and dielectric properties of the sodium borate glasses

The sodium borate glasses doped with different CuO content (70B2O3˗30Na2O˗xCuO with x = 0, 2, 4, 6 and 8 mol%) have been prepared using the conventional melt-quenching technique. The amorphous nature of the prepared samples has been identified by X-ray diffraction (XRD). The experimental and theoretical density, the molar volume, and the oxygen packing density have been defined. The effect of CuO incorporation into the 70B2O3˗30Na2O glass base on the electrical and dielectric properties has been studied. The D.C. electrical parameters have been measured in the temperature range 323˗483 K, while the dielectric parameters have been measured in the temperature range 333˗483 K and the frequency range 10−1˗ 107 Hz. The D.C. electrical conductivity increases while the activation energy decreases by increasing CuO content (mol%). The conduction type is ionic which CuO inserts into the glass structure as a glass modifier. The A.C. study reveals that all investigated glasses obey the correlated barrier hopping model (CBH). Moreover, the dissipation factor peaks indicate the glasses' relaxation nature which has been further analyzed from the real and imaginary parts of the electric modulus.

Magnetic nitrogen-doped carbon nanofibers containing homogeneously dispersed CoFe2O4 nanoparticles with lightweight and efficient microwave absorption performance

Homogeneously dispersed ultrafine CoFe2O4 nanoparticles embedded within N-doped carbon nanofibers (named as CFO@NCNFs) have been fabricated via electrospinning and following heat treatment procedures. The dielectric and magnetic parameters of CFO@NCNFs/paraffin wax composites are regulated through adjusting the concentration of CoFe2O4 to obtain good impedance matching and excellent microwave absorption (MA) properties. Benefiting from the unique structure involving CoFe2O4 @onion-like carbon nanospheres and 3D conductive NCNFs network, as well as the synergistic mechanism between ultrasmall magnetic CoFe2O4 nanoparticles and light mass dielectric NCNFs. The CFO@NCNFs-5 exhibit outstanding MA properties at only 20 wt% filler loading and minimum reflection loss (RL) achieves −47.9 dB (surpass 99.9% MA) at 9.2 GHz with a thin thickness of merely 1.7 mm, and the corresponding effective absorption bandwidth (RL < −10 dB) achieves 5.4 GHz (6.5–11.9 GHz). Moreover, the effective absorption bandwidth (EAB) can be obtained in multiband (3.9–18.0 GHz) by adjusting the thickness of sample layer. Our work indicates that the appropriate incorporation of ultrafine CoFe2O4 nanoparticles encapsulated in NCNFs is a versatile and high-efficiency strategy to integrate lightweight and excellent properties of magnetic carbon-based absorbers.

Sol-Gel synthesis of Ni-doped Zn-based spinel nanoferrites with structural and dielectric characterizations along with magnetic analysis

Ni-doped zinc ferrites (NixZn1−xFe2O4, 0.00 ≤ x ≤ 0.20 in steps of 0.05) were successfully synthesized using a sol-gel self-combustion method. The addition of nickel was aimed at modifying the high-frequency dielectric and magnetic properties of zinc ferrites. Various characterizations, including XRD, FTIR, LCR, and VSM analyses, were conducted to examine the crystal structure, absorption bands, dielectric properties, and magnetic properties of the compounds. XRD patterns revealed a monophasic cubic spinel structure with a preferred (311) plane orientation. The incorporation of Ni resulted in an increased crystallite size as determined by the Scherrer equation and Williamson-Hall method. The lattice parameters and unit cell volume decreased, while X-ray density increased. FTIR transmittance spectra confirmed absorption bands associated with tetrahedral and octahedral bonding. Dielectric parameters were studied across a frequency range of 1 MHz to 3 GHz, with the Maxwell-Wagner model used to explain the observations. Both components of the complex dielectric constant decreased with increasing frequency, indicating normal dispersion behavior of spinel ferrites. The electric modulus revealed relaxation mechanisms, while AC conductivity demonstrated conduction mechanisms. Magnetic properties were characterized using M-H loops measured via VSM. Increasing the Ni concentration led to higher saturation magnetization (Ms), magnetic remanence (Mr), and coercivity (Hc). Magnetic moments and anisotropy constants were calculated based on observed values of Ms and Hc. In summary, the nickel-doped zinc ferrites exhibited notable structural, magnetic, and dielectric properties, suggesting their potential utility in microwave and high-storage magnetic devices.

Monitoring the process of yogurt spoilage by dielectric measurements and spread plate method

In my research work, I primarily focused on the investigation of yogurt (made from home-made raw milk) spoilage by microbiological and dielectric measurements. During the experiment, I continuously monitored the changes in aerobic and anaerobic Lactobacillus cell counts of the product, as a possible spoilage process would cause the deteriorative microbes to displace the lactic acid bacteria, and I also monitored the changes in the dielectric properties of the sample material at 400 MHz frequency. The research results verified that there is a strong correlation between the variation in live cell counts and dielectric parameters in both aerobically and anaerobically cultured lactic acid bacteria. The main conclusions of the results are that the change in the bacterial count, and thus the deterioration process leading to it, can be indirectly monitored in the dairy product under study by low-frequency determination of both the dielectric constant and the loss factor.

Indium tin oxide nanoparticles induced molecular rearrangement in nematic liquid crystal material

In the present article, we report the influence of indium tin oxide (ITO) nanoparticles (NPs) on the macroscopic molecular arrangement of a nematic liquid crystal (NLC) material namely 4 cyano-4ʹ-pentylbiphenyl (5CB). To achieve the objective, we have adopted various concentrations (0.25, 0.5 and 1 wt%) of ITO NPs in 5CB and filled them in the homogeneously aligned sample cells to observe their influence on the dielectric and optical texture of the NLC under investigation. Firstly, polarizing optical micrographs under crossed polarizers were recorded to observe the uniform dispersion and miscibility of ITO NPs in the nematic phase of 5CB. These micrographs also infer the molecular rearrangement of 5CB material that is occurred under the simultaneous and cumulative anchoring effect induced by ITO NPs and aligning layers. Furthermore, the dielectric parameters (permittivity, loss and dielectric loss factor) of pristine and composites as the function of frequency, temperature and DC biasing have been studied. Surprisingly, dielectric permittivity and relaxation frequency of 0.25 wt% ITO NPs composite was found to be the maximum that is decreased with further increment in the concentration of ITO NPs. We have also confirmed the thermal stability of 0.25 wt% ITO NP-induced changes in 5CB. Apart from it, by virtue of temperature-dependent dielectric anisotropy and optical textures, we have reported a significant decrement (∼14 %) in clearing temperature of 5CB. These results will pave the way to devise a system with ITO NPs as the dopant in order to obtain desired phase transition temperature of liquid crystal materials.

Structural, dielectric, electric and magnetic properties of magnesium substituted lithium nanoferrites

Magnesium substituted Li-ferrites nanoparticles with chemical composition Li0.5-0.5xMgxFe2.5-0.5xO4 (x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1) synthesized by sol-gel auto combustion method. Synthesized materials were sintered at 600 °C for 4 h in the air and heated samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive x-ray spectroscopy (EDS) techniques. Rietveld refinement of XRD patterns confirmed the formation of the spinel structure where the lattice constant varied with the increase of Mg content. The crystallite size of magnesium-substituted lithium ferrites was calculated using Scherrer's equation and showed slight changes while the W-H plot shows more changes. The electrical conductivity and activation energy of Mg-substituted lithium ferrite were strongly affected by Mg content and by which they appear to confirm to semiconductor nature. The paramagnetic transition to ferrite was confirmed by the change in the Arrhenius plot, which showed a large variation between two regions that differ in the values of the activation energy, where the values of activation energies in the ferrite region were greater than those that appeared in the para region, as well as the variation between the activation energy values in the non-substituted lithium ferrite. The dielectric parameters such as the real part of the dielectric constant and loss tangent of the samples were analyzed in the range of 50 Hz to 5 MHz at room temperature, 100, 300, and 500 °C. Curie's temperature showed a decrease with the increase in Mg content. Hysteresis loops were measured using a vibrating sample magnetometer (VSM) where both the temperature and the applied magnetic field were changed. The FC result of Li0.5-0.5xMgxFe2.5-0.5xO4 (x = 0.2, 0.4, and 0.6) is almost flat below TB which demonstrates that the Li–Mg nano ferrites show a super-spin glass behaviour.

Nano structural engineering of Ba-substituted Sr-hexaferrites for viable microwave absorbance and magnetic data storage

This work focuses on optimization of magnetic attributes of Sr hexaferrites using Ba as a substituent at Sr-site, for viable utilization in magnetic data storage devices and as microwave attenuation media. In this context, a series of Sr1-xBaxFe12O19 samples was prepared using a facile hydrothermal route. X-ray diffraction confirmed the hexagonal structure with space group P63/mmc. The morphological analysis revealed that the samples had hexagonal nanorod-like morphology which was quite suitable for microwave-absorbing devices and data storage. The analysis demonstrated that the particle sizes were decreased while the width of particles increased with increasing Ba contents. The dielectric parameters were suitably tuned as a function of frequency and Ba contents. The saturation magnetization, coercivity, remanent magnetization, and squareness ratio of all the sample compositions showed an increasing behavior with Ba contents, revealing that the prepared samples were favorable for use as microwave absorbers, data storage devices, and magnetic recording media.

Effect of reinforcing flexible biofriendly ternary polymer blend film with bio ionic liquid on structural, thermal and low-frequency dielectric properties for multifunctional biomedical and soft electronics applications

ABSTRACT In present work the effect of reinforcing choline acetate in PVC-PVP-50%PPy on structural, morphological, mechanical, thermal, electrical and low-frequency dielectric properties of base matrix is studied. Synergistic changes in structural, morphological, mechanical, thermal properties and dielectric parameters in low-frequency region of the host matrix are seen. Disk diffusion test for Escherichia coli and Bacillus subtilis shows that the blend film reinforced with Choline acetate showed their benign nature toward bacteria indicating their potentiality to be used for various scale multifunctional dielectric and electrical applications working in close contact with living matter, green electronics and various health monitoring systems.

Three-dimensional conductive network constructed by in-situ preparation of sea urchin-like NiFe2O4 in expanded graphite for efficient microwave absorption

Expanded graphite (EG) is a modified conductive lamellar carbon that has been widely studied in the field of electromagnetic wave absorption due to its low density, good electrical conductivity, and unique structure. However, its application is limited because the interlayer gap cannot match microwave wavelength, and its single composition has less microwave loss. In this study, sea urchin-like NiFe2O4/EG composites are prepared in situ between expanded graphite layers by microwave treatment. The sea urchin-like NiFe2O4 grows between the expanded graphite to form a three-dimensional conductive network structure, which enhances conductive loss of composites and further increases the interlayer distance of EG. The extended interlayer distance promotes multiple reflections and scattering of electromagnetic waves in composites and improves dielectric properties. In addition, EG with a large specific surface area provides many active sites, further promoting interface and dipole polarization. Benefiting from synergistic effect of NiFe2O4 and EG, magnetic loss and dielectric loss of NiFe2O4/EG composites have been improved and impedance matching is further enhanced. The results indicate that the minimal reflection loss of NiFe2O4/EG-4 reaches −53.47 dB at 2.69 mm, and the effective absorption bandwidth reaches 2.97 GHz. In addition, based on the computer simulation technology results, NiFe2O4/EG can attenuate microwave energy under experimental conditions. This work provides a strategy for synthesizing carbon matrix composites with adjustable dielectric parameters and electromagnetic wave properties.

Exploring the sustainable frontier by investigating structural, electrochemical and ion transport properties of potassium salt-doped PVA-based polymer electrolyte for supercapacitor application

In the current study, a biodegradable green polymer was used for energy storage application. Solid polymer electrolytes (SPEs) are fabricated by incorporating constant loading weight percent (40 wt%) potassium thiocyanate (KSCN) and various glycerol into PVA by the solution cast method. The X-ray diffraction (XRD) test shows that the most conductive electrolyte (σdc = 4.34 × 10−3 S cm−1) determined by electrochemical impedance spectroscopy (EIS) possesses the lowest degree of crystallinity (Xc = 11.4). The EIS test reveals that the PVKSG4 sample has the minimum resistance. The interaction between various constituents of the electrolyte was observed by the fourier transform infrared (FTIR) spectroscopy. The transport parameters (D, n, and μ) associated with moving cations as determined by both EIS and FTIR approaches are comparable and well matched with DC conductivity results. Ionic conductivity and dielectric parameters have the same trend with glycerol concentration. Transference numbers of ions (ti) and electrons (te) for the PVKSG4 are calculated to be 0.918 and 0.082, respectively, meaning that ions are the dominant species contributing to conduction. Linear sweep voltammetry (LSV) study displays that the PVKSG4 film possesses a breakdown voltage of 2.3 V which is enough for device construction. The equivalent series resistance (ESR) of the electric double layer capacitor (EDLC) device has been slightly increased from 59 to 68 Ω over the initial and finial cycle. The capacitive nature of EDLC was confirmed by the cyclic voltammetry (CV), and from the galvanostatic charge/discharge (GCD) test the values of specific capacitance, specific energy density, and specific power density were found to be 72 F g−1, 11 Wh Kg−1, and 1800 W Kg−1. The parameters of EDLC device is an indicative for the fact that the future of green energy is linked to supercapacitors as an alternative for toxic Li-ion batteries.

Rational construction of mushroom-like Ni@N-doped carbon tubes composites with enhanced electromagnetic wave absorption

It is confirmed that electromagnetic wave absorption (EMA) materials with a metal-carbon dual-phase structure has exposed great potential for achieving tunable, strong, and wide EMA. Herein, the mushroom-like Ni@N-doped carbon tubes (NNCTs) are prepared by nickel-catalyzed growth of carbon tubes, realizing carbon encapsulated metal particles. One end of the carbon tube grows and connects to form a bundle of mushroom-like structures, and the other end of the carbon tube is filled with nickel as the mushroom head. The structure control of NNCTs can be achieved by adjusting the amount of catalyst Ni. Appropriate amount of nickel can control the formation of mushroom-like structure. The results show that the structure has a great influence on the EMA performance. Particularly, NNCT-0.5 provides a minimum reflection loss of -60.47 dB with a thickness of 4.0 mm, and the widest effective absorption bandwidth for RL< -10 dB of NNCT-1.5 at a thickness of 2.00 mm was 7.53 GHz (10.47–18.00 GHz). The immobilization of carbon in melamine was achieved by catalytic generation of carbon tubes with metal ions Ni. Metal-carbon biphasic composites introduce dielectric and magnetic losses. The presence of multiple interfaces and voids in the mushroom structure allows tuning the dielectric parameters and optimizing the impedance matching. This work provides an effective strategy for the fabrication of dielectric and magnetic composites with special structures, which has great potential in attenuating electromagnetic wave energy.