The microwave absorbing properties of materials are mainly related to the impedance matching characteristics and microwave attenuation properties of materials.

For the impedance matching characteristics, it is necessary to meet certain boundary conditions when designing the material, so as to minimize the reflection of the electromagnetic wave incident on the surface of the material, so that more of it can enter the material. The impedance matching characteristics are related to the electromagnetic characteristics of the material, the frequency of the electromagnetic wave, the thickness of the coating, and other factors. According to the transmission line theory, its normalization is shown in equation (1):^[24]

Where ：Z_in represents the input impedance of the absorbing material, ε_r and μ_r represent the complex permittivity and complex permeability, respectively, d represents the coating thickness, C is the speed of light, and f is the frequency of electromagnetic wave. The input impedance should be consistent with the impedance of the absorber for good matching characteristics, and the optimal matching condition of electromagnetic parameters is that the ε_r is infinitely close to the μ_r. In the microwave band, the permittivity of existing absorbing materials is often greater than the permeability, so minimizing the difference between them can improve the impedance matching performance.

For the attenuation characteristics of the material, the absorbing material is required to have a higher imaginary part of the electromagnetic parameter to attenuate the electromagnetic wave by strengthening the polarization and magnetization of the material, as shown in formula (2):^[25]

The attenuation constant is positively correlated with the electromagnetic wave loss ability of the material, that is, the larger the attenuation constant is, the stronger the electromagnetic wave loss ability is.

The reflection loss (RL) of the absorbing material to the electromagnetic wave is a parameter that comprehensively reflects the absorbing characteristics of the absorbing material, and the degree is expressed in decibel (dB), and the calculation formula is shown in formula (3):^[24]

Dielectric loss is the loss and absorption of electromagnetic waves by converting electromagnetic energy into heat energy through the action of materials themselves, which mainly includes dielectric loss caused by polarization effect and conductivity loss caused by thermal resistance effect^[25].

In the centimeter band (2 ~ 18 GHz), the dielectric loss is mainly caused by the interface polarization and the dipole relaxation polarization. Interfacial polarization occurs at the interface of the incongruent phase. It is caused by the inhomogeneous aggregation of charged particles due to the external alternating electric field. Thermionic relaxation polarization and dipole polarization can be analyzed by Debye relaxation polarization theory, as shown in Equation (4)^[26]. If the dielectric material has a relaxation polarization process, a semicircle curve called Cole-Cole semicircle will be formed in the coordinate system with the real part of the dielectric constant as the horizontal axis and the imaginary part of the dielectric constant as the vertical axis. To a certain extent, the number of Cole-Cole semicircles formed is positively correlated with the strength of the relaxation polarization effect.

The conductance loss is related to the conductivity of the material. When there is an external electric field, the movement of electrons under the action of the electric field produces a macroscopic current, which produces a thermal effect under the action of the material resistance and dissipates energy^[27]. In theory, the greater the conductivity of a material, the greater the macroscopic current generated and the greater is the thermal effect. In fact, when the conductivity of the material is high, the electromagnetic wave can only be distributed on the surface of the material and cannot enter the interior, so that the material becomes a reflector and produces skin effect. The skin depth of the ferromagnetic material can be obtained by using Maxwell's equations, as shown in equation (5):^[28]

Where μ_i represents the initial permeability and σ is the electrical conductivity of the material. It can be seen from the formula (5) that the higher the frequency of the electromagnetic wave is, the smaller the skin depth is. If the skin depth is smaller than the particle size, the electromagnetic wave can only act on the surface of the material. Therefore, the development of small-size absorbing materials plays an important role in counteracting the skin effect.

Silicon carbide is a typical wide band gap semiconductor, which has adjustable electrical properties, good high temperature and oxidation resistance, low thermal expansion coefficient and high mechanical strength, and can be used in a variety of high temperature and high corrosive environments, such as high temperature insulation, electromagnetic wave absorption, filtration and catalyst support^[29]. There are more than 250 different stacking sequence types of SiC, mainly cubic β-SiC (3C-SiC) and hexagonal α-SiC (including 2H-SiC, 4H-SiC, 6H-SiC), and their stacking sequences are shown in Fig. 1^[12]. Different types of materials show different microwave absorbing properties. For dielectric loss SiC materials, the conductivity of different materials plays an important role in its dielectric loss properties. For the band gap of several common types of SiC at present, 3C-SiC has the lowest band gap, thus showing more excellent dielectric properties^[30].

Due to its unique morphology and structure, the fiber has unique properties different from powder materials in electronic transport, optics, magnetism, electricity, etc. At the same time, it has more excellent physical and chemical properties than the traditional bulk structure, such as low density, high temperature resistance, corrosion resistance, good mechanical strength, etc^[31,32]. Therefore, nanofibers have become a very promising high-performance and multifunctional absorber, which is expected to achieve the comprehensive requirements of "thin, wide, light and strong". Among them, silicon carbide nanowire （SiC_NWs） have the characteristics of large specific area, superior thermo-mechanical properties, adjustable electrical properties, high temperature resistance and oxidation resistance, which also show good application prospects in the field of electromagnetic wave absorption. At present, the preparation of absorbing SiC_NWs mainly includes carbothermal reduction, vapor deposition, polymer precursor pyrolysis, electrospinning and so on^{[33][34][35][36]}. Li et al. used polycarbosilane (PCS) as a precursor to prepare a flexible silicon carbide nanowire film by electrospinning and pyrolysis, as shown in Figure 2 (a). When the content of the material in the paraffin matrix is 10 wt%, it has good dielectric loss performance.The minimum reflection loss （RL_min） is − 41 dB, and the effective absorption bandwidth (EAB) is 5 GHz, which indicates that the three-dimensional network structure can effectively strengthen the polarization effect and improve the dielectric loss performance, and its mechanism diagram is shown in Fig. 2 (B)^[36]. The material has the characteristics of low filling ratio and high efficiency of wave absorption, and also has the advantage of simple preparation. Changing the cross section of the fiber is of great significance to improve the microwave absorbing properties of fibrous SiC. Liu Xuguang used PCS as raw material to prepare silicon carbide fibers with special cross sections such as strip, trilobal, quatrefoil, pentalobal, hexalobal, seven-leaf, three-fold leaf, T-shape and C-shape by melt spinning, air curing and high temperature firing.It is found that the special-shaped fiber section changes the specific surface area and surface curvature of the fiber, thereby affecting the dielectric constant and polarization ability of the fiber, and improving its microwave absorbing properties^[37]. In addition to intrinsic SiC fiber, SiC fiber can also be used as a matrix to introduce new phases to further improve its flexibility, dielectric properties and microwave absorption properties. Yi et al. Used SiC fiber felt as a template to introduce cemented carbide (HfC) phase, and when the HfC content was 2.5 wt%, the HfC/SiC nanofiber/silicone resin composite (10 wt%) had a RL_min of − 33.9 dB and an EAB of 7.4 GHz at 12.8 GHz with a matching thickness of 3 mm^[38]. SiC fiber can be used not only as the matrix of flexible radar absorbing materials, but also as the reinforcement phase of ceramic matrix radar absorbing materials. Gao et al. Fabricated a SiC fiber/mullite-silica composite by precursor infiltration and sintering (PIS) process, and found that the microwave absorption properties of the composite were significantly enhanced from 8.2 GHz to 12.4 GHz when the SiC fiber was doped with （SiC_f）^[39]. When the matching thickness is 2. 9 mm, the RL_min is − 44 dB at 12 GHz. At the same time, Gao et al. Also explored the effects of preparation conditions on the mechanical, dielectric and microwave absorption properties of SiC_f/Mu composites^[40]. The results show that the bending strength increases from 81 MPa to 213 MPa with the increase of sintering temperature. The SiC_f/Mu has excellent electromagnetic wave absorption performance, the RL_min is − 38 dB at 12 GHz, the thickness is 2. 9 mm, and the effective absorption bandwidth covers the whole frequency range from 8. 2 GHz to 12. 4 GHz. SiC fiber radar absorbing material is a kind of good lightweight and flexible radar absorbing material, which can be used not only as a radar absorbing matrix material, but also as a reinforcement phase in other radar absorbing materials. However, the properties of SiC fiber absorbing materials are closely related to its fiber diameter, thickness, morphology and other factors. Further exploration of the relationship between fiber structure and absorbing properties is of great significance to guide the preparation of high-performance SiC fiber absorbing materials.

The hollow structure can make the electromagnetic wave reflect and scatter many times in the cavity, and has the characteristics of low density and high specific surface area, which can effectively improve the absorption rate of electromagnetic wave. At present, the common hollow SiC absorbing materials mainly include hollow spherical and hollow tubular structures and hollow foam structures. Xiao et al. Fabricated hollow silicon carbide microtubes by using carbon fiber (CF) as a template and SiC/CF coaxial material prepared by microwave heating as a template^[41]. It is found that the hollow silicon carbide microtube has a dB@14.9 of − 25.7 dB@14.9 GHz and an EAB of 5 GHz at a sample thickness of 2 mm. The dielectric properties of the hollow silicon carbide microtube can be tuned by the wall thickness of the silicon carbide microtube. Using yeast as a biological template, Zhou et al. Prepared β-crystalline hollow silicon carbide with yeast micromorphology, with the maximum diameter of about 4.3 mm and the minimum diameter of about 3.5 mm^[42]. It is found that hollow silicon carbide achieves a RL_min of − 51.74 dB at 12.08 GHz when the thickness is 3.1 mm, and an EAB of 6.05 GHz when the thickness is 4.0 mm. This is because the hollow spherical structure not only further reduces the weight of the absorber particles, but also effectively improves the impedance matching characteristics and the attenuation performance of electromagnetic waves. The absorbing mechanism is shown in Figure 3. The combination of hollow structure and porous structure can not only improve the absorbing performance, but also strengthen the mechanical properties of the material. In theory, the rich pore structure in absorbing materials will increase the number of reflection and scattering of electromagnetic waves in the pores, and improve the efficiency of electromagnetic absorption and loss. On the other hand, the existence of porous structure can also provide more polarization centers, strengthen the polarization effect, and may change the transmission path of electromagnetic waves, increasing the probability of electromagnetic wave dissipation through interference. Ye et al., using chemical vapor deposition and direct oxidation, fabricated a hollow silicon carbide foam with a double interconnected network, which had a superior compressive response of 14.09 MPa at a strain of 17.51%, and in addition, it achieved a RL_min of − 50.75 dB at 6 GHz when the thickness was 4.85 mm^[43]. Generally speaking, the hollow structure has the characteristics of lightweight microwave absorption. Although the special hollow structure can effectively enhance the microwave absorption performance of the material, its preparation process is relatively complex, and how to achieve the controllable preparation of the hollow structure with low cost and high efficiency is a key and difficult problem.

Compared with the traditional absorbing materials, the core-shell structure composite absorbing materials can improve the impedance matching characteristics of the materials by compounding materials with different characteristics, thereby improving the absorbing properties of the materials, and the core-shell structure materials can also improve the absorbing properties of the materials by changing the proportion of the core-shell layer materials, the micro-morphology, the size of the core shell, and the like. At present, the common core-shell SiC absorbing materials mainly have core-shell fiber structure and core-shell spherical particle structure.

Metal-organic frameworks (MOFs) are a kind of organic-inorganic hybrid porous crystal materials with periodic network structure, which are formed by coordination self-assembly of Metal nodes as Secondary building units (SBUs) and organic ligands. They have shown broad application prospects in the field of microwave absorption due to their structural diversity, high specific surface area and good structural tunability^[48][49]. The structure of MOFs is regular polyhedral particles, and MOFs and their derivatives generally have a low aspect ratio, resulting in insufficient connectivity in the matrix, which is not conducive to further enhancing the absorbing properties. The structure of MOFs based on SiC nanowires can effectively solve this problem. Zhang et al. Grew a co-base MOF structure material on the surface of one-dimensional SiC_NWs, and synthesized a roast-like MOFs/SiC_NWs hybrid nanostructure, whose preparation method and micromorphology are shown in Fig. 5. Compared with pure SiC_NWs and pure calcined MOFs, MOFs/SiC_NWs calcined under air and argon showed significantly enhanced electromagnetic wave absorption capacity, and the EAB of the material could reach 5.92 GHz at a matching thickness of 2 mm^[50]. This stems from its enlarged aspect ratio, improved connectivity within the material, and reduced complex dielectric constant, resulting in more electromagnetic waves entering the material, thus enhancing its interfacial polarization performance. At the same time, the introduction of magnetic materials into the structure of MOFs can further enhance the absorbing properties. Yang et al. Prepared a multi-component composite composed of silicon carbide, Ni, nickel monoxide, and carbon nanoparticles (NPs) by annealing silicon carbide NPs and Ni-based metal-organic frameworks (Ni-MOF) in argon^[51]. Compared with the single silicon carbide NPs and Ni-MOF components, the SiC/Ni/NiO/C nanocomposite has a more efficient electromagnetic wave absorption (EWA) performance, achieving a RL_min of − 50.52 dB at 13 GHz when the material matching thickness is 4.0 mm. The structure of most MOFs-derived absorbing materials mainly depends on the structure of MOFs themselves, and how to further strengthen the design of the internal structure and further explore the relationship between its structure and performance needs further study. At the same time, how to improve the microwave absorbing properties of MOFs at low and wide frequencies is also a challenge.

SiC aerogel is a typical ceramic aerogel, which has high strength, corrosion resistance, low thermal expansion coefficient and infrared shielding effect, making it a potential electromagnetic wave absorbing material in complex environment^[52][53]. Wang Zhijiang's team of Harbin Institute of Technology prepared graphene oxide-derived silicon carbide aerogel by carbothermal reduction method. The results show that graphene oxide aerogel can be well converted into ultra-low density silicon carbide aerogel, which has the advantages of low density and wide absorbing bandwidth, and EAB can reach 5.5 GHz^[54]; In addition, in order to reduce the cost of SiC preparation, the team also used biomass eggplant as a precursor to prepare biomass-derived SiC-based aerogel through freeze-drying, high-temperature carbonization and carbothermal reduction steps. The sample has a maximum RL_min of − 43 dB and an effective microwave absorption bandwidth of 4.0 GHz at a thickness of 2.0 mm^[55]. The electromagnetic wave loss mechanism of silicon carbide aerogel should come from its special porous structure, good impedance matching, interfacial polarization, defect-induced dipole polarization, and locally formed micro-current. Using flexible nanofibers as the matrix to construct three-dimensional fiber aerogels can overcome the shortcomings of poor mechanical properties of traditional aerogels to a certain extent, and can further reduce the mass of materials, which is in line with the current development trend of absorbing materials. Professor Wang Hongjie's team at Xi'an Jiaotong University used chemical vapor deposition technology to prepare a large number of SiC-based fiber aerogels^[56,57]. It is found that the conductive continuous network constructed by the fiber aerogel structure can reduce the energy barrier of electron hopping and provide a longer transmission path for the migration of free carriers, thus improving the conductive loss capability. In addition, in highly porous structures, the repeated reflection and scattering of electromagnetic field on the interface can further improve the absorption performance of electromagnetic wave. In addition to the common lightweight fiber aerogels, the preparation of hierarchical (layered) aerogel structure is also an effective way to improve the absorbing properties of SiC. From the macroscopic layering point of view, Wang Hongjie's team used the overlapping method to prepare high-performance electromagnetic wave absorbing aerogel composed of alternating multilayer wave transparent silicon nitride (N) layers and absorbing silicon carbide (C) layers, which has ultra-low density （∼8 mg/cm³）, wide effective absorption bandwidth (8.4 GHz), and strong reflection loss (− 45 dB) performance at room temperature^[58]. From the point of view of micro-stratification, Wang Zhijiang's team used free radical polymerization to add carbon fibers to hydrogel to form a three-dimensional framework, and introduced silicon carbide through carbothermal reduction reaction, thus preparing layered carbon fiber reinforced SiC/C/C (CF-SC) aerogel^[59]. The method can wrap the carbon fiber in a porous skeleton to form a layered porous structure. The results show that when the matching thickness is 3. 2 mm, the RL_min of the material is − 52.6 dB and the EAB is 8. 6 GHz, which can cover the whole Ku-band, because the layered porous structure helps to build the conductive network of electron transfer.This leads to higher conductance loss, and in addition, extensive inhomogeneous interfaces are formed between the porous skeleton and the fiber, as well as between C and silicon carbide inside the material, which enhances the interfacial polarization and promotes the dissipation of electromagnetic waves.

As a new type of aerogel, the preparation process of SiC aerogel is more complex than that of traditional oxide and carbon aerogels, especially the ultra-light SiC fiber-based aerogels reported at present, which require high preparation conditions and cost. At the same time, there are still some shortcomings in the current preparation processes of SiC aerogels, such as how to solve the problems of large shrinkage and easy cracking of aerogels, how to improve the mechanical properties of materials, and how to take into account the economic requirements.

SiC material is a wide band gap semiconductor, and SiC fiber (SiC_f) has good resistivity tunability (resistivity tuning range ：10⁻³~10⁴Ω·m）, and it also has high saturated carrier drift velocity and thermal conductivity, which plays an important role in improving the strength and dielectric properties of SiC materials^[60][61]. Han et al. Prepared five-directional braided silicon carbide fiber preform reinforced SiC_f/SiC composite by precursor infiltration pyrolysis (PIP), and found that the material had good microwave absorption ability, which could achieve a RL_min of − 16.1 dB at 8.2 GHz and an EAB of 1.5 GHz^[62]. In order to solve the problem that the absorbing properties of SiC_f/SiC composites prepared by traditional PIP method need to be further improved, Mu et al. Made some improvements on the PIP method. Firstly, the precursor of polycarbosilane (PCS) was properly crosslinked, and the SiC fiber was decarburized to prepare SiC_f/SiC composites with strong absorbing properties.The results show that the reflection loss of the untreated composite is less than − 5 dB in the frequency range of 8. 2 ~ 18 GHz, while the RL_min and EAB of the treated composite with a thickness of 3. 1 mm are − 23.5 dB and 5. 9 GHz, respectively^[63]. The use of coating technology on silicon carbide fibers also plays an important role in improving the electromagnetic wave absorption properties of silicon carbide fiber reinforced silicon carbide composite （SiC_f/SiC）. Huang et al. Deposited silicon carbide nanowires （SiC_NWs） on pyrolytic carbon (PyC) coated silicon carbide by electrophoretic deposition (EPD), followed by silicon carbide chemical vapor infiltration (CVI) to obtain SiC_NWs/PyC-SiC_f/SiC composite^[64]. The results show that the dB@15.6 of the composite is − 58.5 dB@15.6 GHz, and when the matching thickness is 2.2 mm, the EAB can reach 6.13 GHz (11.43 ~ 17.56 GHz), which is mainly due to the improvement of dielectric loss capability and impedance matching and the enhancement of multiple reflection of the material. The preparation method, morphology and loss mechanism are shown in Fig. 7. The principle and method of collaborative design of SiC fiber type, weaving pattern, interface layer and matrix electrical properties are very important for the performance optimization of SiC_f/SiCstructural absorbing materials. At present, there is a lack of systematic research, and the synergistic optimization matching principle of absorbing properties and mechanical properties needs to be further studied^[61].

In order to further improve the single loss mechanism of SiC materials, the magnetic loss is introduced by compounding SiC materials with magnetic materials, and the microwave absorption properties of SiC materials are further enhanced through the synergistic effect of the dual loss mechanism of magnetic loss and dielectric loss. The magnetic loss mechanism is mainly through hysteresis loss, ferromagnetic resonance and eddy current loss to absorb a large amount of electromagnetic wave energy and convert it into heat energy to achieve the goal of microwave absorption. At present, SiC-based materials are mainly compounded with magnetic materials such as Fe, Co and Ni.

Hou et al. Prepared Fe/SiC hybrid fibers by electrospinning and high-temperature (1300 ° C) pyrolysis using PCS and ferroferric oxide precursors^[65]. The results show that the introduction of iron has a significant effect on the morphology, crystallization temperature and microwave electromagnetic properties of the hybrid fibers. In addition, the Fe particles can also be used as a catalyst to promote the growth of SiCO nanowires on the surface of the hybrid fiber.It is found that when the PCS/Fe ratio is 3: 0.5, the RL_min is about − 46.3 dB at 6.4 GHz, and the EAB can cover the C-band (4 ~ 8 GHz), which is an excellent microwave absorbing material, especially in the field of low-frequency microwave absorption. Wang et al. Prepared covalently bonded SiC/Co hybrid nanowires (NWs), and the analysis showed that Si — O — Co bonds were formed between SiC NWs and magnetic Co NCs^[66]. The charge transfer occurs in the covalently bonded SiC/Co hybrid NWs. When the content of Co in the hybrid is 25.1 wt%, the cooperative coupling effect induced by SiC/Co realizes broadband absorption with an effective bandwidth of 6.6 GHz (10 – 16.6 GHz). Li et al. Fabricated SiC-coated Ni nanocomposite by arc discharge method, and the Ni @ SiC nanocomposite absorber composed of crystalline SiC and a small amount of C/SiO_x has excellent microwave absorption properties in the C ~ Ku band, with EAB up to 7.2 GHz (6.2 ~ 13.4 GHz), covering almost half of the C band and the whole X band^[67]. For the composite of magnetic materials and SiC materials, how to further improve its impedance matching performance and maximize the synergy of magnetic loss and dielectric loss is an important research topic.At the same time, the magnetic saturation of magnetic materials decreases at high temperature, so how to meet the good absorbing properties of magnetic materials/SiC at high temperature and other special environments is one of the important problems worthy of study.

Carbon-based materials have low density, good conductivity and strong dielectric loss properties. The combination of carbon-based materials with SiC can effectively enhance the dielectric loss properties of composites, and achieve the goal of enhancing the absorption properties and broadening the absorbing bandwidth. The common carbon-based materials combined with SiC are carbon black, carbon nanotubes (CNTs) and graphene.

Du et al. Prepared C-doped silicon carbide ceramic nanocomposites using glucose as carbon (C) source^[68]. The doped silicon carbide nanocomposite consists of amorphous carbon and graphite uniformly coated on the silicon carbide matrix. The dielectric properties of the nanocomposite can be tuned by varying the glucose content. When the glucose content is 0.50 mmol/mL and the matching thickness is 1.66 mm, the minimum reflection loss is − 76.6 dB at 16.0 GHz. CNTs have high thermal conductivity and excellent mechanical properties, which can not only enhance the mechanical properties of composites, but also improve the electromagnetic absorption properties. Zhang et al. Fabricated carbon nanotube-supported flexible silicon carbide fiber mats by electrospinning and polymer derived ceramic (PDC) method^[69]. It is found that the introduction of carbon nanotubes greatly improves the electromagnetic absorption performance, and the conduction loss and polarization relaxation loss under the synergistic effect of silicon carbide fibers and carbon nanotubes consume the electromagnetic energy.When the carbon nanotube content is 3 wt%, the RL_min is − 61 dB and the EAB is 2. 9 GHz at a thickness of 3. 5 mm. Cheng et al. Added SiC_NWs into supercritical ethanol-dried graphene aerogel (GA-S) by chemical vapor infiltration (CVI) to prepare a lightweight, heat-resistant, high-performance electromagnetic (EM) absorbing composite^[70]. It is found that the growth of SiC_NWs increases the yield strength of GA-S from 0.15 MPa to 0.47 MPa in the linear elastic region; The two-scale surface roughness increases the water contact angle from 53 ° to 134 ° of the SiC_NW/GA-S; When the thickness is 3.63 mm, the RL_min value of the SiC_NW/GA-S sample is − 54.8 dB at 5.3 GHz, and when the thickness is 2.0 mm, the SiC_NW/GA-S sample has a wide effective absorption bandwidth of 6.5 GHz, as shown in Fig. 8. Silicon carbide and carbon composites are mainly fabricated by incorporating carbon nanostructures into nano-sized SiC, often resulting in limited and unstable interfaces. At the same time, carbon-based materials such as CNTs and graphene are expensive and complex to prepare, which to some extent hinders the wider application of SiC/C composites in electromagnetic wave absorption^[71].

The SiC-based multi-component composite material has a plurality of interfaces between different components, can generate a structure similar to a capacitor, and brings strong relaxation loss to the polarization of the interfaces, and the multi-component magnetic composite material can further enhance the magnetic loss performance, thereby enhancing the wave absorbing performance of the intrinsic SiC and binary SiC composite materials. Zhang et al. Used an in situ carbothermal reduction strategy to prepare a nanocomposite composed of SiC@SiO₂ nanowires and Fe₃Si magnetic nanoparticles from expandable graphite, Si-SiO₂ mixed powder, and ferrocene^[72]. The nanocomposite was found to have an EAB of 5.4 GHz at a matching thickness of 2.4 mm and a RL_min value as low as − 37.53 dB at 15.5 GHz at a matching thickness of 4.9 mm (Table 2). This is due to the synergistic effect of dielectric loss, magnetic loss, interface loss and scattering theory of the composite to produce good absorbing properties. At the same time, the introduction of organic polymer materials and the emerging MXene materials in multi-component composites is also an effective way to improve the absorbing properties. Ma et al. Developed a multiphase nanostructure of SiC_NW/MXene in a polyvinylidene fluoride (PVDF) matrix through electrostatic self-assembly, and found that when the SiC_NW：MXene ratio and the SiC_NW/MXene concentration were 7:1 and 20 wt%, respectively, it reached an effective bandwidth of 5.0 GHz at Ku band.The RL_min can reach − 75.8 dB at the matched thickness of 1.45 – 1.5 mm, which is attributed to the formation of many inhomogeneous interfaces in the polymer matrix due to the synergistic effect of two-dimensional MXene nanosheets and one-dimensional SiC_Nw in the structure^[73]. SiC-based multi-component composites achieve efficient absorption of electromagnetic waves through the dual enhancement of dielectric properties and magnetic loss properties, but how to further analyze the composite loss mechanism, improve the interface stability, and explore the best ratio system need further study.

Metamaterials are structural materials composed of sub-wavelength resonant or non-resonant units arranged periodically or aperiodically, which have extraordinary physical properties such as negative refractive index, inverse Doppler, inverse Cherenkov and so on, which are not possessed by materials in nature, and have shown great research potential in optics, acoustics, thermology and other fields^{[74][75⇓~77]}. Metamaterials have gradually come into people's vision as absorbing materials because of their unique electromagnetic response law. By controlling the transmission characteristics of the electromagnetic wave on the surface of the metamaterial through artificial design, efficient electromagnetic wave absorption can be realized, and the limitations of certain design dimensions and preparation methods of conventional absorbing materials can be effectively compensated, so that the electromagnetic wave absorption area can be flexibly regulated, and the metamaterial has important application value in the field of electromagnetic wave absorption^[78].

Mei et al. Fabricated alumina/carbon nanotubes/SiOC composites with a twisted cross-metamaterial structure using 3D printing technology as well as precursor infiltration pyrolysis (PIP) method, in which carbon nanotubes not only act as a nucleating agent to obtain SiC_NW, but also act as a conductive phase to form a conductive network structure, thereby improving the dielectric and conductive losses of the composite^[79]. When the thickness is 2. 8 mm, the RL_min of the Al₂O₃/CNT/SiC_NW/SiOC composite is − 56.84 dB at 12. 2 GHz, and the effective absorption bandwidth ranges from 8. 2 GHz to 12. 4 GHz; When the thickness is 3. 2 mm, EAB can cover the whole X-band and has excellent EMW absorption performance. In order to further explore the influence of metamaterial structure on absorbing performance and the regulation mechanism of impedance matching characteristics. Li et al. Developed a broadband radar absorbing composite foam metamaterial (CFMM) constructed by silicon carbide/carbon (SiC/C) foam material, FR4 dielectric material and metal pattern, designed and studied the influence of the geometric size of the metal pattern design on the absorption performance of CFMM, and found that by adjusting the side length, array period, line width or split width of the metal pattern,The CFFM impedance can be effectively adjusted to change the absorption characteristics of the CFMM, and the low-density CFMM with an effective absorbing bandwidth of about 14 GHz (4 ~ 18 GHz) is prepared by the template method. The material better meets the development trend of "thin, light, wide and strong" absorbing materials, and its structure, physical object and performance are shown in Figure 9^[80]. In order to reduce the influence of the pattern layer on the absorbing material, Li et al. Studied an all-dielectric radar absorbing array metamaterial (AMM) based on silicon carbide/carbon (SiC/C) foam dielectric material and metamaterial through simulation and experiment, and analyzed the influence of the physical size and array period of AMM on the absorption performance.An optimized AMM with excellent absorption properties was fabricated, and the effective absorption bandwidth of the optimized AMM was about 14 GHz (4 ~ 18 GHz), and the material also had good mechanical properties and thermal stability, which provided a reference for the development of multifunctional SiC-based absorbing metamaterials^[81]. Although there have been many studies on SiC-based absorbing metamaterials, most of them focus on the realization of lightweight, broadband absorption and polarization angle insensitivity. In addition, metamaterials may face a more severe use environment in practical applications, and how to further broaden the functionality, while considering the economy and accuracy of material design and preparation, is an important research aspect in the future.

High temperature absorbing materials are mainly used to meet the stealth requirements of aircraft engine nozzles, aircraft aerodynamic heating components and high temperature parts of naval ships, and show good application prospects in both military and civil fields. SiC material has good high temperature resistance and can maintain good dielectric properties at high temperature, so it is a kind of high temperature absorbing material with great development potential. At present, SiC-based high-temperature absorbing materials can be divided into SiC_f/SiC-based high-temperature absorbing materials, C/SiC-based high-temperature absorbing materials, SiC/ceramic-based high temperature absorbing materials and SiC high-temperature absorbing metamaterials. Han et al. Fabricated SiC_f reinforced SiC_f/SiC composites by in situ growth of silicon carbide nanowires on silicon carbide fibers by chemical vapor infiltration^[82]. It is found that the conductivity and complex permittivity of the composite show obvious temperature dependence in the frequency range of 8. 2-12. 4 GHz at 25-600 ℃, and increase with the increase of temperature, with a minimum reflection loss of − 47.5 dB at 11. 4 GHz and an effective bandwidth of 2. 8 GHz at 600 ℃. Ceramic matrix composites are the main high temperature absorbing materials because of their lightweight, high strength, high hardness, good dielectric properties and excellent environmental stability^[83]. Silicon nitride (Si₃N₄) is a typical ceramic material, and SiC as an absorber of Si₃N₄ can show good high-temperature microwave absorption properties, which has attracted more and more attention. Zhou et al. Prepared silicon nitride ceramics modified by silicon carbide nanofibers by gel casting to improve the dielectric and microwave absorption properties in the X-band (8.2 ~ 12.4 GHz) at 25 ~ 800 ℃, and the composite also had obvious temperature dependence.The dielectric constant increases with the increase of temperature from 25 ℃ to 800 ℃, and when the content of silicon carbide nanofibers is 7. 5 wt%, it shows excellent X-band microwave absorption ability and stability at 25 ~ 800 ℃^[84]. In order to further improve the absorbing properties of binary ceramic matrix composites, Li et al. Designed a high temperature electromagnetic wave absorption structure model with low, high and low dielectric constant hierarchical structure from two aspects of multi-material composite and morphology control.And Si₃N₄-SiC/SiO₂ composite ceramics were prepared. It was found that the effective dielectric constant was weakly dependent on temperature, so the Si₃N₄-SiC/SiO₂ showed good matching characteristics between room temperature electromagnetic absorption and high temperature electromagnetic absorption^[85]. At 500 and 600 ℃, the RL_min of the Si₃N₄-SiC/SiO₂ with a certain sample thickness reaches − 51.9 and − 35.9 dB, respectively, and the effective bandwidth reaches 4.16 and 4.02 GHz, respectively, indicating that it has broad application prospects in the field of high temperature electromagnetic absorption. The combination of SiC/ceramic matrix composites and metamaterial design is also one of the effective ways to improve the absorbing properties of materials. According to the design principle of sandwich metamaterial absorbing composite materials, Zhou Qian et al. Selected low resistance SiC_f/Si₃N₄ as the loss layer and high resistance SiCf/Si₃N₄ as the dielectric layer to prepare sandwich structure SiC_f/Si₃N₄ composite metamaterial^[86]. The experimental results show that the design of the discontinuous loss layer on the mesoscopic scale can improve the impedance matching of the material and enhance its surface current, so that the room temperature reflection loss of the composite metamaterial is less than − 11.3 dB in the frequency range of 8 ~ 18 GHz. When the temperature rises to 600 ℃, the average reflection loss in the frequency range of 8 ~ 18 GHz hardly changes, and the absorber has temperature-insensitive microwave absorbing characteristics. In addition, some scholars have used aluminosilicate fibers and SiC materials to show good high temperature absorbing properties^[18]. For high-temperature SiC-based absorbing materials, most of them focus on the composite of SiC materials and ceramic-based materials, and develop towards metamaterials. However, low-frequency absorbing materials are an important research topic.The low frequency absorbing properties at high temperature are worthy of attention, and whether SiC-based high temperature and low frequency absorbing materials can be developed by using new material design and material preparation is one of the key research directions.

With the rapid development of high and new technology, it provides a broader stage for absorbing materials. However, these materials will also face more demanding application environments. Therefore, it is an inevitable development direction to develop microwave absorbing materials with high adaptability to complex environment, multi-function and ultra-long life^[87,88]. Fan Bingbing's team at Zhengzhou University prepared a multifunctional SiC nanofiber aerogel (SiC NFA) by chemical vapor deposition (CVD) technology, which showed low density （~9 mg·cm⁻³）, excellent mechanical properties, high fatigue resistance, fire resistance, high temperature thermal stability and good thermal insulation properties^[89]. In addition, the oil-modified silicon carbide NFA has significant hydrophobicity and good self-cleaning property, and it has good microwave absorption property with a RL_min of − 39.37 dB at 7.04 GHz when its thickness is 1.9 mm. On the basis of intrinsic SiC nanofiber aerogel, the team also prepared a multifunctional SiC@SiO₂ nanofiber aerogel （SiC@SiO₂NFA） with three-dimensional (3D) porous crosslinking structure.The material has the advantages of ultra-low density （~11 mg·cm⁻³）, superelasticity, fatigue resistance and fire resistance, high-temperature thermal stability, thermal insulation property and strain-dependent piezoresistive sensing behavior, the RL_min value of the material is − 50.36 dB, the EAB value is 8.6 GHz, the versatility is further expanded, and the microwave absorbing property is enhanced to a certain extent^[90]. In addition, compounding SiC materials with organic materials can also enhance their functionality. Wang Zhijiang's team prepared uniform size silicon carbide nanoparticles (silicon carbide NPs) by carbothermal reduction, and then dispersed them into epoxy resin matrix.Silicon carbide type memory epoxy (SSME) composite was formed, and it was found that when the proportion of silicon carbide NPs was 20 wt%, the RL_min was − 62.02 dB and the EAB was 7.7 GHz at the optimum thickness of 4.25 mm.When the thickness is 4. 50 mm, the EAB is 8. 1 GHz. In addition, the addition of silicon carbide NPs makes the material have good deformability and shape recovery ability, compared with the sample without silicon carbide NPs.The deformation efficiency and shape recovery rate are improved by 125. 81% and 17. 84%, respectively, which further expands the application prospect of SiC-based radar absorbing materials, indicating that it has great potential in the development of multi-functional, flexible, wearable and coating materials^[91]. At present, there are many studies on the functional expansion of SiC-based multifunctional absorbing materials, which have laid a good foundation for future practical applications to a certain extent. The research on SiC absorbing materials in the field of anti-corrosion is mostly in its infancy.At the same time, it is particularly important to study its superhydrophobicity and antifouling properties, so the development of efficient, green, environmentally friendly, anticorrosive and antifouling SiC-based multifunctional absorbing materials is of great value to improve the safety and reliability of naval equipment in the marine environment^[89].