Relative Complex Permeability Research Articles

A Facile Route Preparation of Fe3O4/MWCNT/ZnO/PANI Nanocomposite and its Characterization for Enhanced Microwave Absorption Properties

AbstractWith increasing concerns regarding the potential health risks associated with microwave‐based technology, researchers have been actively investigating materials with impressive microwave absorption properties. In this study, a synthesis and investigation of a nanocomposite, named Fe3O4/MWCNT/ZnO/PANI, consisting of magnetite (Fe3O4), multi‐walled carbon nanotube (MWCNT), zinc oxide (ZnO), and polyaniline (PANI) as a microwave‐absorbing material, was carried out for the first time. The nanocomposite was prepared through a simple physical mixing approach and demonstrated tunable microwave absorption, making it highly suitable for shielding applications. Structural analysis techniques, including X‐ray diffraction (XRD), Fourier‐transform infrared spectroscopy (FTIR), and scanning electron microscopy with energy‐dispersive X‐ray analysis (SEM‐EDAX), confirmed the presence of all components in the nanocomposite. Moreover, ultraviolet‐visible spectroscopy (UV‐Vis) further verified the formation of nanocomposite components and revealed an adjustable optical bandgap ranging from 2.86 to 3.34 eV. Impressively, the nanocomposite exhibited promising microwave absorption properties, with a minimum reflection loss (RL) of −32.66 dB for the nanocomposite containing 37.50 % PANI by weight, and a maximum electromagnetic bandwidth (EB) of 2.26 GHz for the nanocomposite containing 44.44 % PANI by weight, indicating its potential as an effective shielding material. Furthermore, a modified theory combining transmission line, Landau‐Lifshits, and Drude‐Lorentz theories was introduced to extract complex relative permittivity and permeability, providing insights into the role of polyaniline in enhancing the microwave absorption properties of the nanocomposite as measured by reflection loss (RL).

Higher-Frequency Permeability Measurement by Harmonic Resonance Cavity Perturbation Method

A new combination of electric field antenna and coupling hole plates are introduced to extend the measurable frequency range of rectangular waveguide type harmonic resonator to evaluate complex relative permeability of magnetic composites by perturbation method from 18 GHz to 38 GHz (K/Ka-band). The noise suppression performance parameter ωμ”=2πfμ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> μ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> ” [kΩ/m] is useful to estimate the performance of magnetic powder composite sheets especially beyond 10 GHz range where relative permeability is as small as 0-2. The ωμ” exhibited the maximum of 166 kΩ/m at 27 GHz for a carbonyl iron powder composite sheet, and as high as 510 at 38 GHz for Sendust sheet. These values meet ωμ”≥100 kΩ/m criteria that some commercially available noise suppression sheets exhibit in their recommended frequency range. These performance match Sub-6 GHz band and 28 GHz band used for 5G telecommunication equipment.

Temperature Dependence of Complex Relative Permeability of the Polycrystalline La0.7Sr0.3MnO3

&lt;p&gt;吾人量測多晶態鑭鍶錳氧變化溫度的電阻率與頻率範圍為 10 kHz 至 10 MHz 的相對複數磁導率特性。樣品室溫電阻率很小，僅為數 m&amp;sdot;Ωcm。電阻率隨著溫度增加，在相轉變溫度 TP = 361 K 附近顯現金屬到半導體的相轉變。室溫量測到的磁譜顯現與磁壁位移有關的鬆弛特性，色散情況非常明顯。隨著溫度升高，磁導率增加，在居禮溫度 TC前達到最大值，然後迅速下降。當溫度從室溫增加，磁壁位移鬆弛頻率 fr幾乎保持不變。當溫度升高到 TC附近，由於磁導率迅速降低，fr劇烈增加。在 TC以上，磁譜的色散現象消失。量測到的 fr與理論值相當符合，可看出磁壁位移的阻滯來源主要源自於渦電流阻滯。&lt;/p&gt; &lt;p&gt;&amp;nbsp;&lt;/p&gt;&lt;p&gt;The temperature-dependent resistivity and complex relative permeability of the polycrystalline La0.7Sr0.3MnO3 have been investigated in the frequency range 10 kHz -10 MHz. The measured room-temperature resistivity is of the order of mcm. As the temperature increases, the resistivity increases and shows a metal-insulator transition. The transition temperature TP is about 361 K. There are pronounced dispersions of the relaxation in the measured spectra, which are due to the domain-wall displacement. The magnitude of permeability increases with increasing temperature, reaches its maximum value near the Curie temperature TC, and then abruptly drops. As the temperature increases, the relaxation frequency fr almost remains a constant value. However, it rapidly increases around TC due to the suddenly decrease of the permeability. The dispersion phenomena of the permeability spectra disappear above TC. The consistence of the measured and calculated fr value shows that the damping factor of domain-wall displacement mainly comes from the eddy current.&lt;/p&gt; &lt;p&gt;&amp;nbsp;&lt;/p&gt;

A New Adaptive Implicit Method for Multicomponent Surfactant-Polymer Flooding Reservoir Simulation

Summary In the oil industry, chemicals can improve oil production by mobilizing trapped and bypassed oil. Such processes are known as chemical-enhanced oil recovery (CEOR). Surfactants and polymers are important chemicals used in CEOR with different mechanisms to improve oil recoveries, such as reduction in residual saturation, oil solubilization, and mobility control. However, both surfactant and polymer may increase the cost of oil production, making optimizing these processes essential. Reservoir simulators are tools commonly used when performing such field optimization. The simulation of surfactant flooding processes has been historically performed with the implicit pressure explicit composition (IMPEC) approach. The injection of surfactants requires modeling the brine/oil/microemulsion phase behavior along with other processes, such as capillary desaturation and retention. The microemulsion phase behavior and the complex relative permeability behavior can lead to convergence issues when using fully implicit (FI) schemes. Only recently, the FI approach has been efficiently applied to simulate this process using new modeling. The adaptive implicit method (AIM) can combine the benefits of the FI and IMPEC approaches by dynamically selecting the implicitness level of gridblocks in the domain. This work presents a new AIM in conjunction with recently developed models to mitigate discontinuities in the microemulsion relative permeabilities and phase behavior. The approach presented here considers the stability analysis method as a switching criterion between IMPEC and FI. To the best of our knowledge, the approach presented here is the first AIM to consider the brine/oil/microemulsion three-phase flow in its conception. The new approach uses the finite volume method in conjunction with Cartesian grids as spatial discretization and is applied here for field-scale problems. The new approach is tested for polymer flooding and surfactant-polymer (SP) flooding for problems with several active cells ranging from about a hundred thousand to almost a million. The AIM approach was compared with the FI and IMPEC approaches and displayed little variation in the computational performance despite changes in the timestep size. The AIM also obtained the fastest performance for all cases, especially for SP flooding cases. Furthermore, the results here suggest that the gap in performance between the AIM and FI seems to increase as the number of gridblocks increases.

3D printed crack-free SiOC(Fe) structures with pyrolysis-induced carbon nanowires for enhanced wave absorption performance

High-performance SiOC(Fe) wave-absorbing ceramics, containing a large number of carbon nanowires, were successfully prepared using a combination of photopolymerization 3D printing technology and the polymer-derived ceramic pyrolysis method. By employing an optimized segmented slow heating scheme with extended holding time, the pyrolysis of SiOC(Fe) ceramics at 1000 °C facilitated the growth of carbon nanowires, Fe3C and SiO2 grains. These carbon nanowires were interlaced and interconnected within the samples, forming abundant conductive networks. This highly conducive network efficiently converted electromagnetic energy into thermal energy, effectively dissipating electromagnetic waves, and consequently enhancing the microwave absorption performance of ceramics. Moreover, this approach not only reduced ceramic cracks but also improved the dielectric loss performance of the materials, achieving a minimum reflectivity value of −35.72 dB. The SiOC(Fe) ceramics added with 5 wt% VcFe effectively enhanced the magnetic loss of the material, reduced the difference between the relative complex permeability (μr) and the relative complex dielectric constant (εr), and improved the impedance matching between the material surface and air, thereby further improving its microwave absorption performance. This resulted in an increase in the maximum effective absorption bandwidth of the material to 12.7 GHz at 5 mm. This study offers a promising solution for the preparation of ceramic matrix composite materials incorporating carbon nanowires, magnetic particles and ceramic precursors, which would be potentially valuable for radar detection and sensor applications.

Wide Microstrip Line Type Probe With Slits and Permeability Evaluation of Thick Magnetic Material

We have developed a new microstrip line type probe with a wide conductor having some slits to eliminate the measurement error of the demagnetizing effect in thick samples. The slits enhanced the homogeneity of the high-frequency current in the wide direction of the microstrip conductor, which resulted in the application of a uniform high-frequency magnetic field to the sample. Complex relative permeability of thick NiZn ferrite sheet and carbonyl iron particle (CIP) sheet ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3\times $ </tex-math></inline-formula> 1 mm, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$100 ~\mu \text{m}$ </tex-math></inline-formula> in thickness) has been evaluated accurately using the probe. The measurement error of permeability was evaluated within about 15% in 0.1–20 GHz compared with the conventional Nicolson–Ross–Weir method.

Comprehensive study of electromagnetic wave absorption properties of GdMnO3-MoSe2 hybrid composites

Recently, the public does not avoid the use of RF/microwave communication and non-communication devices, which means they will be constantly exposed to radiation from those devices, which will worsen their health in the long term, as well as there will be interference and coupling effects between devices. In this paper, a novel and high-performance absorber material is created and analyzed. The microscopic and macroscopic properties of Gadolinium Manganite (GdMnO3), Molybdenum Diselenide (MoSe2), and three mixtures of GdMnO3-MoSe2 (GdMo) with 20, 30, and 40% filler loading were investigated. The procedure for producing the five materials was explained and described in detail. The mixture of GdMo with 20, 30, and 40 wt% filler loading has the features of GdMnO3 and MoSe2. For macroscopic analysis, the measured relative complex permittivity and permeability of the five synthesized materials are modeled using the Lorentz dispersion model. Among the five study materials, GdMo with 40 wt% filler loading shows the highest electric and magnetic losses with loss tangent, tan δe ≈ 0.228 and tan δm ≈ 0.38 where the absorption performance is better compared to its pristine components, namely GdMnO3 and MoSe2. Based on the transmission theory of metal plate backing materials, the GdMo with 40 wt% filler loading and thicknesses ranging from 0.0014 m to 0.0021 m, which is terminated by a metal plate on the back side, exhibited the optimum microwave absorption performance with a minimum reflection loss value better than −20 dB at X-band operating frequency. Without a metal backing, a 0.008 m thickness of GdMo with 40 wt% can achieve reflection loss, RL of −10 dB from 9.2 GHz to 12.4 GHz, and RL of −20 dB from 11.1 GHz to 12.4 GHz.

Micro-Structural Design of CoFe2O4/SWCNTs Composites for Enhanced Electromagnetic Properties

In order to prepare microwave-absorbing materials with low density and high wave absorption performance, CoFe2O4/SWCNTs composites with well-designed necklace-like structures were successfully prepared in this paper by a simple solvothermal method. CoFe2O4/SWCNTs composites with different cobalt salt contents were synthesized by adjusting the experimental parameters. The results of the relative complex permeability and relative permittivity of the samples, which were investigated by vector network analysis in the frequency range of 2 to 18 GHz, are collected to support the study of the microwave absorption characteristics of the samples. Different microsphere densities and different cobalt salt contents have obvious differences in the electromagnetic absorption properties of the composites. When the additions of FeCl3·6H2O, Co(Ac)2·4H2O, and NH4Ac were 0.432, 0.200, and 0.400 g, respectively, the best reflection loss reached −42.07 dB, and the effective absorption frequency (RL &lt; −10 dB) ranges from 3.2 to 18 GHz. Therefore, this is a preparation strategy of CoFe2O4/SWCNTs composites with necklace structure, which has the advantages of simple process, environmental friendliness, low cost, and high stability. The unique necklace-like structure design makes the carbon nanotubes partially exposed, which is more beneficial to achieve good impedance matching and giving the CoFe2O4/SWCNTs composite excellent electromagnetic loss capability.

Research on Detent Force Characteristics of Winding Segmented Permanent Magnet Linear Synchronous Motor Based on Analytical Model

The winding segmented permanent magnet linear synchronous motor (WS-PMLSM) has not only a general slotting effect but also a unique two-end effect caused by the segmented stator and the finite length passive mover, which makes the detent force of WS-PMLSM possess the qualities of all types of linear motors. This paper adopts a physics-based multiple analytical method to study the detent force properties. First, an accurate sub-domain model is used to obtain the magnetic field distribution of the tooth slot, and the results of the analytical solution and the graph of the tooth slot effect are obtained using the scalar magnetic potential. Subsequently, the effect of the end unenergized core on the magnetic field is analyzed using Maxwell’s theory for the stator end effect, revealing that the end effect causes pulsating and reversing magnetic fields in the motor, which in turn creates mutual inductance with unequal phases, and generates thrust fluctuations. Finally, a complex relative air-gap permeability is introduced on the basis of the conformal mapping to equate the end effect generated by the permanent magnet. The accuracy of the proposed multiple analytical models was verified by the results of the finite element method (FEM) and experimental model.

Preparation and Thickness Optimization of Graphenic-Based Carbon Material as a Microwave Absorber

The purpose of this study is to optimize the thickness of a layered graphenic-based carbon compound, which is a non-magnetic material derived from biomass (old coconut shell). After the sample was exfoliated using HCl solution, the morphological structure showed that the material used in this study is a reduced graphene oxide (rGO), similar to carbon but with a thickness of less than 10 nm and lateral size in submicron (100 nm). The sample with a 2 mm thickness was then characterized using a vector network analyzer (VNA) to measure its reflection loss (RL). The measurement result is evaluated by converting the S-parameter values (S11 and S21) from the VNA using the Nicolsson Ross Weir (NRW) method to obtain input variables such as relative complex permeability and relative complex permittivity. Following this, the single-layer thickness of the sample was optimized using a genetic algorithm (GA), which can predict the appropriate thickness so that the optimum RL can be obtained. The optimum thickness of the sample was found to be 3.48 mm, which resulted in a much higher RL. The RL was re-measured for verification using a sample with the corresponding optimized thickness, revealing that this optimization is feasibly operational for a radar absorbing material (RAM) design.&#x0D; HIGHLIGHTS&#x0D; &#x0D; Carbon compounds containing graphenic phase derived from coconut shell are functional materials having various unique properties such as superior electrical conductivity, large surface area, and excellent structural flexibility, and microwave absorbtion&#x0D; The single-layer microwave absorber employing carbon compounds has been prepared&#x0D; The layer thickness optimized using a genetic algorithm (GA) can estimate the appropriate design with the maximum reflection loss (RL)&#x0D;

Sintered microstructure effect on RF-wave shielding properties of a Cu-doped Ni–Zn-polycrystalline ferrite

The shielding properties of a Cu-doped Ni–Zn polycrystalline ferrite in the frequency range 1MHz to 1GHz were explored. Samples of composition (Cu0.12Ni0.23Zn0.65)Fe2O4 were prepared by the traditional ceramic route. The complex relative permittivity (εr=ε′−jε″) and permeability (μr=μ′−jμ″) of the absorber ceramics were measured, and the minimum reflection-loss RL, matching frequency fm, matching thickness dm and bandwidth for RL≤−20 dB were calculated using the theory of the absorbing wall. Effect of the main process parameters (pressing pressure P, sintering temperature T, and sintering time t) on the electromagnetic properties and microwave-absorbing characteristics was deeply investigated. The rise of the three selected process parameters was observed to improve the sintered microstructure of the final specimens (monitored by the relative density ϕ and the average grain size G), provided that abnormal grain growth does not occurred. The increase in sintered relative density and average grain growth modifies complex permeability and permittivity in the explored frequency range, enhancing the shielding properties of the material.

Investigation of the Microwave Absorption Properties of Fe Based Nanocomposites

The objective of this work was to provide information about the behaviour of Fe-based nanocomposites when exposed to microwaves. It is about rectangular bulk samples of epoxy resin reinforced by nanocrystalline Fe powders and shaped in accordance to the internal section of the R100 metallic waveguide (8.2 to 12.4 GHz) at a fixed thickness of 7 mm. The nanocrystalline Fe powders were obtained by high-energy mechanical milling process using a planetary Retsch PM 400-ball mill. The milling speed was fixed at 200 rpm for three durations and the milling process were performed under Argon atmosphere. The bulk nanocomposites were obtained by dispersion of 30% vol. of the nanocrystalline Fe powders in the resin matrix. Electromagnetic parameters as complex relative dielectric permittivity and magnetic permeability, electric and magnetic loss tangent and reflection loss were calculated using reordered S parameters. The scattering parameters were characterized using a measure cell made off two metallic R100 wave-guides associated to an Agilent 8719 network analyser according to the reflection-transmission technique. The obtained spectra inform on the new electromagnetic properties as well as the absorption characteristic acquired by the bulk nanocomposites due to the presence of the nanocrystalline Fe powders.

High Permeability Photosintered Strontium Ferrite Flexible Thin Films.

The paper is focused on the development and optimization of strontium ferrite nanomaterial and photosintered flexible thin films. These magnetic thin films are characterized with direct current (DC) and high frequency measurements. For photosintered strontium ferrite samples, we achieved relative complex permeability of about 29.5-j1.8 and relative complex permittivity of about 12.9-j0.3 at a frequency of 5.9 GHz.

Parallel Aligned Nickel Nanocone Arrays for Multiband Microwave Absorption.

Magnetic nanostructures with conical shape are highly desired for pursuing extraordinary magnetic properties and microwave absorption. However, the fabrication of such nanostructures with controlled shape and size uniformities and alignment is not yet realized. Accordingly, the magnetic properties and their application as microwave absorber are not well understood. Here, we report on the first demonstration of controlled fabrication of soft magnetic nickel nanocone arrays with sharp geometry, large aspect ratio, uniform size, and parallel alignment. The imaginary part of the relative complex permeability shows multiband absorption in the 2-17 GHz range. Such an exceptional microwave absorption results from the uniform conical shape and size and the parallel alignment. The absorption mechanisms are discussed under the framework of natural resonance and exchange resonance. The natural resonance is dependent on the shape anisotropy and facilitated by the conical geometry. The exchange resonance is well explained by the observation of the bulk spin waves with exchange coupling at the tip of nanocones using the inelastic light scattering and is consistent with exchange theory predictions for the quantization of bulk spin waves. We expect that our work will shed light on the physical insights into the magnetic properties of nanocones and find great potential in applications of microwave absorption.

Enhancement of electromagnetic interference shielding based on Co0.5Zn0.5Fe2O4/PANI-PTSA nanocomposites

Nanotechnology has involved enormous attention in enhancing electromagnetic interference (EMI) shielding. The nanocomposite {Co0.5Zn0.5Fe2O4/PANI-PTSA} was synthesized in different ratios (9:1, 3:1, 1:1 and 1:3) and coded as (CZFP1, CZFP2, CZFP3 and CZFP4), respectively. X-ray diffraction, Hall effect, vibrating-sample magnetometer and then vector network analyzer in X-band were used to be characterized. The Nicholson–Ross–Weir (NRW) method was applied to determine the real and imaginary parts of the complex relative permittivity (e*) and permeability (μ*). The nanocomposite CZFP3 exhibited the best absorption property with the optimal matching thickness of 3 mm in the frequency of 8–12 GHz. The value of the maximum RL was − 2.3 dB (> 40% power absorption) at 8.1 GHz, − 17.08 dB (98% power absorption) at 9 GHz and − 24.86 dB (99.73% power absorption) at 10.9 GHz. The excellent absorption properties of Co0.5Zn0.5Fe2O4/PANI-PTSA nanocomposites with ratio weight 1:1 indicated their great potential as microwave absorbing materials.

Bio-silica incorporated barium ferrite composites: Evaluation of structure, morphology, magnetic and microwave absorption traits

A series of bio-silica incorporated barium-ferrite-composites with the composition of (x)Bio-SiO2:(80-x)γ-Fe2O3:(20)BaO, where x = 0, 1, 2, and 3 wt% were prepared using the modified solid-state reaction method. The influence of different bio-silica (extricated from sintered rice husk) contents on the surface morphologies, structures, and magnetic characteristics of these composites were assessed. The relative complex permittivity and permeability were resolved using the Nicholson-Ross-Weir strategy in the frequency range of 8–13 GHz. Meanwhile, the reflection loss was estimated through the transmission/reflection line theory to assess the MW absorption properties of the composites. Incorporation of the bio-silica in the barium ferrite composites generated a new hexagonal phase (Ba3Fe32O51) and a tetragonal phase (BaFeSi4O10) which led to a decrease in the saturation magnetization and significant shift in the MW frequency absorption peak positions.

Dynamic Coupled Model of Vibration System With Galfenol Damper Considering Eddy Currents and Hysteresis

Based on the effective magnetic-field expression, the constitutive equations with eddy currents, the hysteresis model, and the electromechanical coupled model, a dynamic mechanical-magnetic-electro bidirectional coupled (MMEBC) model of the vibration system with the Galfenol damper is established, and the system's transmissibility and key frequency-dependent complex stiffness are derived. Comparisons between the calculated and measured results show that the proposed model can accurately describe the dynamic minor-loop curves of the Galfenol rod around the bias point, can provide reasonable data trends of the frequency-dependent complex Young's modulus, piezomagnetic coefficients, and relative permeability, and can predict the changing laws of the resonant frequency and the resonant peak with bias point and shunt resistance. It is found that the damper under the shunt resistance circuit can provide the peak attenuation rate of 87.91%, which is higher than 79.58% of the damper under open circuit.

A facile precursor pyrolysis route to bio-carbon/ferrite porous architecture with enhanced electromagnetic wave absorption in S-band

Bio-carbon has been deemed as a promising species of electromagnetic wave absorption materials for stealth material due to its unique pore structure and light weight as well as abundant available crude materials such as plants. In this paper, bio-carbon/ferrite porous architecture is prepared by a facile precursor pyrolysis route to acquire a light weight absorbent using natural bamboo and Fe(NO3)3 as the precursors. The product can be directly synthesized in a tube furnace at 800–1000 °C under nitrogen atmosphere protection. The minimum reflection loss (RL) can be tailored ranging from −43.2 dB at 17.6 GHz (the band width below −10 dB is 13.6 GHz, from 4.4 to 18.0 GHz) to −21.9 dB at 14.6 GHz (the band width below −10 dB is 6.4 GHz, from 11.6 to 18.0 GHz) by controlling the annealing temperature. The enhanced and frequency-adjustable EM absorption properties are provable determined by the coordination of complex permittivity and relative magnetic permeability of the composite carbon/ferrite.

In situ dynamics response mechanism of the tunable length-diameter ratio nanochains for excellent microwave absorber

Faster response benefits the high-performance of magnetic material in various live applications. Hence, enhancing response speed toward the applied field via engineering advantages in structures is highly desired. In this paper, the precise synthesis of Co nanochain with the tunable length-diameter ratio is realized via a magnetic-field-guided assembly approach. The Co nanochain exhibits enhanced microwave absorption performance (near to -60 dB, layer thickness 2.2 mm) and broader effective absorption bandwidth (over 2/3 of total S, C, X, Ku bands). Furthermore, the simulated dynamic magnetic response reveals that the domain motion in 1D chain is faster than that in 0D nanoparticle, which is the determining factor of magnetic loss upgrade. Meanwhile, based on the controllable magnetic field experiment via in situ transmission electron microscopy, the association between magnetic response and microstructure is first present at the nanometer-level. The real and imaginary parts of relative complex permeability are determined by the domain migration confined inside Co nanochain and the magnetic flux field surrounded outside Co nanochain, respectively. Importantly, these findings can be extended to the novel design of microwave absorbers and promising candidates of magnetic carriers based on 1D structure.

A novel synthesize approach and electromagnetic wave absorbing properties of expanded graphite/Fe3O4/carbon nanorod composite microstructure

Expanded graphite (EG), as a new carbon nanomaterial, has excellent characteristics, which includes great specific surface area, good electrical conductivity, and excellent mechanical properties. In this study, the microwave puffing method combined a rapid, simple and inexpensive process that has been developed to synthesize EG/Fe3O4/carbon nanorod(CN) nanoparticle hybrids, which can be applied as an electromagnetic radiation absorbent. Carbon nanorods not only played a role to connect the graphene layer structure but also promoted a synergistic graphene absorbing effect. Meanwhile, the catalyst of carbon nanotubes was decomposed into nano magnetic particles under microwave conditions, which can improve the absorbing properties of the composite material. The morphologies of the carbon nanocomposites were examined by SEM, EDX and TEM, respectively. The complex relative permittivity and permeability of the absorber were measured using a microwave network analyzer in the frequency range of 2–18 GHz. With an increase of the matching thickness, the maximum absorbing peak of the carbon nanocomposites shifted to a lower frequency region, under above the frequency range. When the matching thickness was 2.4 mm, the minimum absorption peak of the carbon nanocomposites was − 28 dB at 14.4 GHz, and a minimum reflection loss of − 10 dB was achieved within the range of 12.3–17.8 GHz.