Excellent Electromagnetic Wave Absorption Properties Research Articles

A Semi-amorphous Ti-BDC-derived Ti/C nanocomposite for efficient electromagnetic wave absorption

Electromagnetic (EM) interference presents a crippling risk to both human health and the dependability of technological devices. Due to their diverse advantages, metal-organic framework (MOF) derivatives have received much attention in developing novel EM wave-absorbing materials. Nevertheless, achieving desirable EM wave absorption capabilities in magnetic carbon-based absorbers through deliberate adjustment of MOFs remains a difficult task. In this study, a novel nanoporous carbon material (TiO2/C) has been successfully synthesized by a semi-amorphous material (Ti-BDC), which has excellent EM wave absorption properties. In detail, the minimum reflection loss (RL) of −49.7 dB and broad effective absorbing bandwidth (EAB) of 4.16 GHz can be reached with an absorbent thickness of 2.2 mm. The improved performance is mostly due to the dipole polarization of the functional groups and the even distribution of the nanoparticles, which form a seamless network. This promotes the dissipation of polarization and dielectric energy at the interface. In addition, the TiO2 nanoparticles on the carbon material improve the impedance matching, further enhancing the material's absorption performance.

Microstructure and EMW absorption properties of PDCs-SiCN(Ti) ceramics with adjustable SiC nanowires and TiC nanocrystallines

Herein, a novel type of ceramic material exhibiting tunable electromagnetic properties was synthesized using the polymer-derived ceramics (PDCs) method. The precursor employed in this process was a tetrabutyl titanate-modified polysilazane, which ultimately led to the formation of PDCs-SiCN(Ti) ceramics. High-temperature annealing (1400 °C-1500 °C) was used to prepare PDCs-SiCN(Ti) ceramics, which exhibited a unique dual nanostructure comprising SiC nanowires and TiC nanocrystals and served as effective nanoabsorbents. The SiC and TiC contents are closely related to the annealing temperature and induced Ti content. After annealing at 1500 °C, the PDCs-SiCN(Ti) ceramics with the typical A + B + C electromagnetic absorbing structure exhibited excellent electromagnetic wave (EMW) absorption properties. The PDCs-SiCN(Ti) ceramics, with a Ti content of 5 wt%, demonstrated an effective absorption bandwidth (EAB) of 3.8 GHz, which encompassed 90.5 % of the X band, despite having a relatively thin impedance matching thickness of only 2.1 mm. The outstanding EMW attenuation capability of the PDC-SiCN(Ti) ceramics can be ascribed to their large specific surface area and defects combined with the high permittivity of dispersed TiC nanocrystals, which facilitates multiple reflections of EMW within the SiCN matrix. Therefore, this work provides a controllable preparation method for PDCs-SiCN(Ti) ceramics with various microwave absorbing phases.

High-performance electromagnetic wave absorption by two-dimensional mesoporous monolayer Ti3C2Tx MXene

Transition metal carbide MXene, with its unique chemical composition, structure and sizeable particular surface area, is widely applied in wave absorption. However, the high conductivity of MXene resulted in an impedance mismatch that prevented electromagnetic waves from entering the material to achieve dissipation, and thus, tuning the intrinsic properties of pure MXene to obtain excellent electromagnetic wave absorption is still a challenge. Here, we strengthen the absorption of electromagnetic waves by generating titanium vacancies through hydrogen peroxide etching and thus forming micro-sized wrinkles with porous MXene. Porous MXene possesses an excellent microstructure and surface state, abundant porous defects, and moderate electrical conductivity, allowing it to achieve well-matched impedance, dipole polarization, and conduction loss, thus inheriting excellent electromagnetic wave absorption (EWA) properties. Therefore, the porous MXene achieves a strong absorption of − 63.31 dB and an adequate absorption bandwidth (EAB) of 6.88 GHz at a matched thickness of 2.39 mm with a fill ratio of 6 wt%.

Abundant vacancies induced high polarization-attenuation effects in flower-like WS2 microwave absorbers

Defect engineering could provide new ideas for the design of transition metal disulfide electromagnetic wave (EMW) absorbers with high performance. Since the effects of dipoles on impedance matching and EMW absorption are crucial for the development of novel absorbers, the polarization attenuation dependence on defect engineering should be understood at micro- and macro-scales. In this paper, it is found that the defect-rich WS2 nanoflowers synthesized by the cold plasma method possess excellent EMW absorption properties. Cold plasma treatment of materials is easy to perform and maintains the original shape of the material to a high degree. The formation of defects results in abundant electrochemically active sites, increased multiple reflection losses, improved dielectric properties and impedance matching in the materials. The RLmin of the defect-rich material with a thickness of 3.19 mm is as high as −54.36 dB at 8.16 GHz, and the effective absorption bandwidth is 4.72 GHz. The results reveal that the formation of defective vacancies enhances the effects of dipole polarization of the material on improving its EMW absorption properties. Thus, this work provides not only a facile preparation route for novel EMW-absorbing materials, but also a new strategy for tunning defects in transition metal disulfides.

Fabrication of Metal–Organic Framework‐Derived LaCo/C‐Decorated Ti3C2Tx Composites with High Electromagnetic Wave Absorption

Thin‐thickness and lightweight electromagnetic wave (EMW) absorption materials are critically needed for stealth technology in the military stealth field. The special structure of a material is important for improving its good EMW absorption. Herein, a series of porous metal–organic framework‐derived LaCo/C‐decorated Ti3C2Tx (LaCo/C/Ti3C2Tx) composites are prepared by carbonization at high temperatures. Impressively, the minimum reflection loss of LaCo/C/Ti3C2Tx–2 is −47.72 dB at 10.26 GHz (thickness 2.3 mm), and the optimal effective absorption bandwidth is 5.45 GHz (thickness 1.9 mm). The excellent EMW absorption properties are due to multiple electromagnetic loss mechanisms, such as polarization loss, magnetic loss, and multiple reflections and scattering. This work provides a new route for the application of Ti3C2Tx‐based derivatives.

Fabrication of hollow Ni/NiO/C/MnO2@polypyrrole core-shell structures for high-performance electromagnetic wave absorption

In response to the increasingly serious problem of electromagnetic wave pollution, there is a growing demand for materials capable of absorbing electromagnetic waves. A crucial strategy involves optimizing the microstructure and composition of these materials. In this study, the Ni/NiO/C/MnO2@PPy (NCMP) composites are successfully fabricated through the combination of hydrothermal method, high-temperature calcination process, chemical method and in situ polymerization. Due to the strong synergistic effect of the dielectric and magnetic components, and good impedance match, the NCMP-40 exhibits excellent electromagnetic wave absorption properties, with an optimal reflection loss (RLmin) of −56.23 dB at a thickness of 3.87 mm, and a high effective absorption bandwidth (EAB) of 6.86 GHz (10.68–17.54 GHz) at a thickness of 1.97 mm covering the entire Ku-band part of the X-band. Moreover, the radar cross section (RCS) attenuation is obtained through a simulation procedure. Compared to the sole perfect electrically conductive (PEC) layer, the PEC layer coated with NCMP-40 achieves an RCS value consistently below −10 dB m2 in the range of −60° < θ < 60°, and an RCS value is −22.0 dB m2 at θ = 0°. The prepared NCMP-40 presented herein shows excellent electromagnetic wave absorption performances. And this study provides a new method for the structural design of electromagnetic wave absorption materials.

Fabrication of polydopamine-coated ZIF-67 derived Co@CN/rGO composite with excellent electromagnetic wave absorption properties

Constructing a reasonable microstructure and component modulation is considered as an effective way to improve the absorption performance of the absorbents. Herein, a series of Co@CN/rGOs composites were obtained via simple pyrolysis of dopamine-coated ZIF-67 loaded graphene oxide (ZIF-67@PDA/GO) at a high temperature. The existence of rGO after thermal treatment effectively improved dielectric loss. The multiple heterogeneous interfaces between rGO and the carbon layers formed by the polydopamine pyrolysis facilitated the interfacial polarization and relaxation. As a result, with only 20 wt% filler content, the RLmin value of Co@CN/10%rGO reached −49.98 dB at 5.50 GHz (low frequency) with a thickness of 4.5 mm. The effective absorption bandwidth increased to 5.70 GHz (10.26–15.96 GHz) by adjusting the thickness to 2.3 mm. This work provides a facile method for the construction of multicomponent nonhomogeneous interfaces and offers a novel strategy for the design of efficient absorbents.

Enhanced electromagnetic wave absorption properties of SiCN(Ni)/BN ceramics by in situ generated Ni and Ni3Si.

In this paper, the SiCN(Ni)/BN ceramic with excellent electromagnetic wave (EMW) absorption performance was successfully prepared. The Ni and Ni3Si were in situ formed by the introduction of nickel acetylacetonate (NA), which effectively improved the impedance matching performance of SiCN(Ni)/BN ceramics. The EMW absorption properties of the SiCN(Ni)/BN ceramics showed a trend of first increasing and then decreasing with the increase in content of NA. When the NA content reached 7 wt%, the impedance matching range of SiCN-7 was optimal. The minimum reflection loss (RLmin) of SiCN-7 reached -53.47 dB at 4.2 mm and the effective absorption bandwidth (EAB) was 2.32 GHz at 3.48 mm. Through the analysis of electrical conductivity, it was found that the proportion of polarization loss in dielectric loss was more than 99%. It is worth noting that the radar cross section (RCS) value of SiCN-7 absorber was lower than that of the perfect electrical conductor (PEC) plate in the range of -90-90°, and showed a larger coverage angle, indicating that it possessed a good practical application prospect in the field of electromagnetic wave absorption.

Tuning the microstructure of porous SiCnw/SiC fabricated by vat photopolymerization 3D printing for electromagnetic wave absorption

SiC is recognized as a viable material for electromagnetic wave (EMW) absorption due to its unique physicochemical properties. However, there are still some challenges at present, such as poor EMW absorption performance and difficulty in the fabrication of complicated structures for optimized EMW properties. Here, we presented a novel strategy through vat photopolymerization (VPP) 3D printing technology and carbothermal reduction to prepare porous SiCnw/SiC ceramics with controlled topologies and excellent EMW absorption properties. The gradient hole structure produced by carbothermal reduction facilitates material impedance matching regulation and improves incident wave multiple scattering as well as the in-situ grown SiCnw acts as the dipole center and improves incident wave dielectric loss. Porous SiCnw/SiC ceramics achieve improved EMW absorption performance with a minimum reflection loss (RL) of −57.67 dB at a thickness of 2.20 mm and with an effective absorption bandwidth (EAB) of 3.93 GHz at a thickness of 2.60 mm, covering almost the whole X-band, demonstrating outstanding EMW absorption properties. Furthermore, it exhibits the potential in the application of EMW absorbing devices with complex structure.

Cobalt-nickel carbonate hydroxide composites achieving excellent electromagnetic absorption and wide bandwidth through incorporation with polypyrrole nanotubes

Electromagnetic absorption composite with prominent absorption properties and wider absorption bandwidth are in urgent desire. Polypyrrole-based composite is a prosperous candidate due to its easiness in synthesis, morphological diversity and controllable conductivity. In the present work, cobalt-nickel carbonate hydroxide (CCH) microwave absorption materials incorporating polypyrrole nanotubes (PNTs) in different loadings (CCH/PNTs) were prepared via a facile template method next to a hydrothermal treatment. The CCH is revealed in a sea-urchin-like morphology and PNTs are dispersed on the surface of the CCH. In light of the unique morphology, large specific surface area and interfaces, the CCH/PNTs composites exhibit excellent electromagnetic wave (EMW) absorption performance and extensive bandwidth of absorption. With a 180 mg loading of PNTs, the composite delivers a minimum reflection loss (RLmin) of − 57.4 dB with an effective absorption bandwidth (EAB) of 5.44 GHz. By tuning the matching thickness, a wide EAB larger than 7 GHz can be obtained in the X-band and Ku-band. The prominent EMW absorption properties can be ascribed to the dielectric loss, the polarization loss and multiple scattering attenuation from the large surfaces and interfaces from PNTs, and the optimization of impedance matching via CCH. The present research can offer an intuitive guide for the conception of microwave absorbers with wide absorption bandwidth.

α-PW11Fe(Co/Ni)/BC derived carbon fiber based nanocomposites for high efficiency electromagnetic wave absorption via synergistic effects of polarization and conductance

In order to enhance the wave-absorbing performance of dielectric/carbon fiber based wave-absorbing materials and explore the dissipative mechanism of electromagnetic wave (EMW), this study utilizes liquid diffusion of K4PW11O39Fe(III)(H2O) (α-PW11Fe), K5PW11O39Co(II)(H2O) (α-PW11Co), K5PW11O39Ni(II)(H2O) (α-PW11Ni) and bacterial cellulose (BC), as well as high temperature carbonization strategy to prepare polycrystalline polyphase transition metals and their compounds with three dimensional porous conductive network structure loaded carbon fiber based nanocomposites wave-absorbing materials. By changing the element type, drying mode and filling amount, we can achieve the tunability of electromagnetic parameters and absorbing properties. Impressively, the best synthesized sample 20 %-α-PW11Ni/BC derived carbon fiber based nanocomposites has excellent EMW absorption properties, with a maximum reflection loss (RL) of -68.1 dB at 2.6 mm matching thickness. The effective absorbing bandwidth (EAB) is 7.2 GHz, and the RL less than -10 dB in the frequency band of 2.2–5.0 mm thickness is 5.3 to 18.0 GHz. The excellent absorbing performance is attributed to the synergy of polarization and conductance, balanced impedance matching, good interface/dipole polarization, and multiple reflections and scattering. Therefore, the prepared composite has a broad application prospect in the field of EMW absorption, and provides a new idea for the design of new efficient absorbing materials.

Dually inner-porous composites with Co@C prismatic rods anchored into graphene aerogel toward superior electromagnetic wave absorbing materials

For electromagnetic wave absorbing materials, integration of excellent electromagnetic wave absorbing property in view of strong electromagnetic wave absorbing intensity and wide effective absorption bandwidth with a very low usage, and a ultralight weight into one material is still challenging. Herein, composites of Co@C@GA (CCGA: CCGA-1, CCGA-2, CCGA-3 and CCGA-4) with a dually three-dimensional (3D) and porous structure were obtained through introducing a prismatic rod shaped Co@C prepared by calcining Co-MOF-74–3D graphene aerogel (GA). At a loading of only 12 wt%, all the CCGA with a wide weight ratio of graphene oxide to Co@C (2:1, 4:3, 1:1 and 4:5) exhibit excellent electromagnetic wave absorption properties. A minimum reflection loss (RLmin) of − 70.28 dB at 12.28 GHz with the thickness of 2.913 mm for CCGA-3 and the maximum effective absorption bandwidth (EAB) of 7.12 GHz at a thickness of 2.520 mm for CCGA-4 are achieved. The low filling ratio, the high RLmin intensity, the wide EAB and the compatibility of the two components in a broad compositional range for losing electromagnetic waves are impressive. Co@C with inner-porous and prismatic rod bundles like unique morphology is confirmed to be very important and can endow CCGA with greatly enlarged interface, enhanced conductivity and proper magnetic property, leading to the effective tuning of electromagnetic property and impedance matching condition.

Effect of Mn content on the structure, electromagnetic properties, and electromagnetic wave absorption characteristics in La0.7Sr0.3Mn1+xO3

The perovskite manganese oxide, La0.7Sr0.3Mn1+xO3 (x = −0.4, −0.2, 0, 0.2, 0.4, 0.6, 0.8, 1.0), was synthesized using the solid-state reaction method. A single-phase perovskite structure was obtained at the stoichiometric composition (x = 0). However, with an increase in Mn excess (x > 0), secondary phases of Mn2O3 and Mn3O4 formed and increased, while La2O3 and Sr-rich phases emerged when Mn is deficient (x < 0). The electrical conductivity, permittivity, and permeability of the samples showed significant variations with x, as both charge transport and magnetism originate from the presence of Mn. Complex permittivity (ε', ε") and permeability (μ', μ") spectra were utilized to calculate RL maps based on a transmission line theory. For samples with x ≥ 0, which exhibited relatively high values of ε' and ε", there was no significant absorption of electromagnetic (EM) waves within the measured frequency range (0.1 ≤ f ≤ 18 GHz) due to high EM wave reflection. Conversely, the Mn-deficient samples (x = −0.2, −0.4) demonstrated excellent EM wave absorption properties in the GHz range. This can be attributed to their favorable impedance matching characteristics, resulting from significantly reduced ε' and ε" values in the Mn-deficient samples. Notably, the sample with x = −0.2 exhibited the most outstanding EM wave absorption characteristics, with an RL value of −56 dB at a frequency of 2.33 GHz and a thickness of 7.59 mm. Additionally, it achieved an RL value of −50 dB at 9.8 GHz and 2.90 mm thickness.

Electromagnetic wave absorption properties of red mud-blast furnace slag based geopolymers filled with various wave-absorption materials

In this work, red mud-blast furnace slag (RM-BFS) based geopolymers with excellent electromagnetic wave absorption property is synthesized through the incorporation of wave-absorption materials. The electromagnetic absorption property of geopolymer is characterized through the arched test, in which the reflection loss of specimens is tested by vector network analyzer (VNA). The microstructure and conductivity of geopolymers are characterized through scanning electron microscopy (SEM), concrete porous structure analyzer and conductivity tester. The crystalline phase and functional groups of geopolymers are characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Compared to Portland cement concrete (PCC), wave absorption band of the geopolymer is wider and the absorption peak in high frequency band is more intense. With the optimal addition of hollow glass microsphere (HGM), Fe2O3 and graphite particles, the absorption bandwidth with reflection loss less than −5 dB are 12.4, 7.7 and 8.1 GHz, and the maximum reflection loss are −9.4, −8.4 and −8.7 dB, respectively. This study might give a clue for preparation of geopolymers with high electromagnetic wave absorption properties.

Ternary borides Cr3AlB4: A novel material of layered structure for efficient broadband microwave-absorption

In this study, a novel MAB phase Cr3AlB4 was successfully synthesized and is, characterized by a layered microstructure that is created via a two-step reaction process. The Cr3AlB4 powders exhibit superior electromagnetic absorption performance, showcasing a minimum reflection loss of - 35.80 dB at a thickness of 1.4 mm, along with an effective absorption bandwidth spanning 5.6 GHz. The excellent electromagnetic wave (EMW) absorption properties of Cr3AlB4 can be ascribed to the synergistic interplay of dielectric and magnetic losses, which is determined by material attributes such as electrical conductivity, inherent defects, and paramagnetic qualities. Notably, the existence of a heterogeneous interface between Cr3AlB4 and Al2O3 impurities significantly promotes impedance matching and improves the microwave-absorption properties. Consequently, Cr3AlB4 emerges as a promising candidate in the realm of EMW absorption materials, offering substantial potential for achieving broad absorption profiles even at a small material thickness. This research expands the realm of possibilities for advanced broadband wave-absorbing materials.

Natural green raw-based Biochar@Co/C composites: Simple water bath synthesis and excellent electromagnetic wave absorption properties

Over the last few years, wave absorbing materials synthesized based on green and eco-friendly natural materials were less studied. Carbon materials derived from natural materials, for example, have a limited absorption performance due to impedance mismatch in electromagnetic wave absorption applications. In this work, composites of MOF derivatives and biochar with strong wave absorbing capability were prepared by biochar and MOF. Biochar was green raw material originated from kapok trees in the school. Then it was compounded with MOF derivatives by pretreatment and water bath to form Biochar@Co/C composites. The effect of annealing temperature on the absorption properties was investigated by varying the annealing temperature. According to the results of the transmission line theory analysis, Biochar@Co/C-700 have RLmin value of −55.22 dB at 5.43 GHz and 3.69 mm. Also, the effective absorption bandwidth EAB can reach 6.37 GHz at 1.94 mm. And the above absorption properties were measured when the filling ratio was only 15 %. Electromagnetic parameter analyses showed that the combination between biochar and MOF derivatives greatly improves the impedance matching of the carbon-based materials, which is a vital factor that enables Biochar@Co/C-700 to have excellent wave-absorbing properties. In addition, the loss mechanism of the complexes to electromagnetic waves was also analyzed and summarized. These results provide a reference path for the preparation of high-performance electromagnetic wave absorption composites from green materials.

Multiple interfacial Fe3C/MnO/NC composites towards high-performance microwave absorption

Exploring high-performance electromagnetic wave (EMW) absorbers remains a formidable challenge in the face of severe EMW radiation and interference. The incorporation of manganese oxide into carbon matrix magnetic composites is proposed to enhance the EMW absorption properties in this work. Multiple interfacial ternary-component Fe3C/MnO/Nitrogen-doped carbon (NC) absorbers were synthesized through facile hydrothermal, oxidative polymerization and carbothermal reduction processes. The results indicated that the composites designed exhibit excellent EMW absorption properties, with an effective absorption bandwidth of 4.88 GHz (13.12–18 GHz) at a mere thickness of 1.5 mm. The outstanding performance of EMW absorption can be attributed to the effective modulation of electromagnetic parameters through a large number of heterogeneous interfaces, defects, and magnetic loss. Meanwhile, adjusting the filling ratios of the composites in the absorber also can significantly adjust the electromagnetic parameters of the samples. This work presents effective approach for the preparation of high-performance EMW absorbers with ternary components, as well as a strategy for developing novel broadband absorbers that are lightweight and have thin thickness.

Co/C composites generated from biomass exhibit outstanding electromagnetic wave absorption

The development of high-performance electromagnetic wave-absorbent materials from inexpensive biomass feedstock is currently the subject of considerable interest. In this study, we developed Co/C composites with excellent electromagnetic wave absorption properties using a simple carbonization method with mangosteen shells as a precursor. The Co/C composite has a minimum reflection loss value (RLmin) of −61.88 dB and a maximum effective absorption bandwidth of 6.32 GHz. For thicknesses ranging from 1 to 5.5 mm, the effective absorption frequency range could cover the entire C, X, and Ku bands. The magnetic loss produced by Co and the dielectric loss, dipole polarization, interfacial polarization, and multiple reflections of biomass carbon synergies enhance the impedance matching capabilities and microwave absorption performance of the composites. The results demonstrate that the activated mangosteen shell magnetic composite has a wider effective absorption bandwidth and greater absorption intensity. This work provides a good potential method for preparation of magnetic particle/biomass-derived carbon microwave absorbing structural materials.

Construction of magnetic nanoparticle channels in SiC/SiO2 composite foam toward efficient electromagnetic wave absorption

The combination of dielectric-magnetic loss synergy and rational microstructure construction is conducive to satisfy the thin thickness, strong absorption and wide frequency bandwidth of the absorbers. In this study, a novel strategy of constructing magnetic nickel nanoparticle channels inside SiC/SiO2 composite foams for the synthesis of Ni/SiC/SiO2 porous composites (NSPC). The magnetic nickel nanoparticle channels retain SiC/SiO2 composite foam internal pore structure, which can optimize the impedance matching and satisfy the dielectric-magnetic loss synergy effect. The results confirm that the presence of multiple heterogeneous interfaces in NSPC, the magnetic and conductive losses imparted by magnetic particles and the unique foam porous structure synergistically make it have extremely excellent electromagnetic wave (EMW) absorption properties. NSPC can obtain ultra-strong reflection loss of −64.86 dB (1.46 mm) and the effective absorption range covers 13.20 GHz (4.80–18 GHz) at a total thickness of 1.79 mm (1.21–3 mm), representing 82.5 % of the whole range of frequencies. Additionally, RCS simulation confirms that NSPC can dissipate more electromagnetic capability in a real environment. In short, this work provides a new reference for the development of materials with rational microstructure construction while achieving thin thickness, strong absorption and broadband absorption.

Polymer-derived NixSiy/Graphene/SiCN composite ceramics with enhanced electromagnetic wave absorption performance

Benefiting from its light weight, unique microstructure and high thermal stability, SiCN ceramics have attracted extensive attention in the field of electromagnetic wave (EMW) absorption. However, due to its poor impedance matching performance and single loss mechanism, the EMW absorption performance of SiCN ceramics requires further improvement. Herein, we introduced Ni and graphene into polysilazane to fabricate NixSiy/Graphene/SiCN composite ceramics by polymer derived ceramics (PDCs) route. The introduction of Ni not only facilitated the formation of various phases, including Si3N4, Ni2Si, Ni31Si12, graphite carbon and Si2N2O, but also catalyzed the in-situ generation of one-dimensional carbon nanotubes (1D CNTs). When the addition content of Ni was 6 wt% and the addition content of graphene was 2 wt%, the NixSiy/Graphene/SiCN composite ceramics exhibited the optimal EMW absorption performance. The minimum reflection loss (RLmin) of NixSiy/Graphene/SiCN composite ceramics reached -52.13 dB at 7.6 GHz with the thickness of 2.7 mm, and widest effective absorption bandwidth (EAB) reached 3.56 GHz (14.44-18 GHz) at 1.26 mm. The dielectric loss was enhanced by carbon materials (turbostratic carbon, 1D CNTs and 2D graphene) and various phases, while the magnetic loss was improved by Ni and nickel silicide. The synergism of multiple loss mechanisms and good impedance matching lead to excellent EMW absorption properties of NixSiy/Graphene/SiCN ceramics.