Gasification fine slag with Fe3O4 composite material, preparation method and application

Abstract

This invention discloses a Fe3O4-infused composite material for gasification slag, its preparation method, and its application. The preparation method of this composite material includes the following steps: S1: Mixing coal gasification slag and polyvinylpyrrolidone, then adding the mixture to water, followed by ultrasonication and stirring to obtain a suspension; S2: Dissolving FeCl3·6H2O and FeCl2·4H2O separately in water, then adding them to the suspension from S1, mixing thoroughly to obtain a mixed solution, and adjusting the pH of the mixed solution to 10-11 using NH3·H2O for reaction; S3: Washing and drying the product after the reaction to obtain the Fe3O4-infused composite material for gasification slag. This invention synthesizes a multi-interface Fe3O4-infused composite material for gasification slag using a direct co-precipitation method. This composite material exhibits excellent microwave absorption properties, characterized by high electromagnetic loss and a wide absorption band; with a thickness of only 2.7 mm, the composite material has a high RL (radiofrequency response)... min The effective bandwidth is -28.10 dB, while the effective bandwidth reaches 4.00 GHz with a thickness of 1.7 mm. The excellent absorption performance of the composite material is due to its multi-interface structure and good electromagnetic impedance matching, as well as the cooperative effect between the dielectric and magnetic loss.

Description

Technical Field

[0001] This invention relates to the field of microwave absorbing materials technology, and in particular to a composite material of gasified fine slag mixed with Fe3O4, its preparation method and application. Background Technology

[0002] The widespread use of electronic devices has led to severe environmental pollution from electromagnetic radiation, threatening human health and shortening the lifespan of sophisticated electronic equipment, thus affecting its normal operation. To avoid this problem, many fields, such as aerospace, information security, and healthcare, have raised the performance requirements for electromagnetic wave absorbing materials. Therefore, in recent decades, researchers have focused on developing and exploring more efficient microwave absorbing materials. The electromagnetic loss performance of absorbing materials is determined by their dielectric or magnetic loss characteristics. Researchers have therefore developed many different compositions of absorbing materials based on these two properties. Magnetic loss materials include ferrites (Fe3O4, CoFe2O4, MnFe2O4, ZnFe2O4, etc.), magnetic metal oxides (γ-Fe2O3, CoO, etc.), and magnetic metals (Fe, Co, Ni, and their alloys). In addition, dielectric loss materials mainly include composites of conductive polymers, specific oxides, and carbon-based materials. Among these, Fe-based magnetic loss materials exhibit excellent performance, have been extensively studied, and have a wide range of applications.

[0003] However, Fe-based magnetic loss materials inherently possess defects such as poor impedance matching, high density, easy oxidation, and strong skin effect, which severely affect their microwave absorption performance. These defects need to be mitigated by designing their morphology and structure and doping with multi-component enhanced ferromagnetic wave absorbing particles. Currently, the basic approaches to preparing Fe-based composite materials include mixing and surface coating. A simple method for preparing Fe-based composite materials is to directly mix pure iron particles with other microwave absorbing materials. This method enhances electromagnetic absorption performance through the synergistic effect of impedance matching and polarization loss. Jang et al. used the DoctorBlade method to disperse carbonyl iron powder of different mass fractions in polydimethylsiloxane matrix. In the 0.1–18 GHz range, the optimal microwave absorption performance was achieved with a 72 wt% carbonyl iron powder content and a thickness of 1.5 mm, reaching the minimum reflection loss (RL) at 14.6 GHz. min The RL value was -27.5 dB. Zhang et al. synthesized a composite material composed of iron oxide, carbon nanotubes, polypyrrole, and carbon through in-situ polymerization. The material doped with 8.8% wt% multi-interface carbon nanotubes produced a multilayer structure and multiple interfaces, resulting in magnetic and dielectric losses, and achieving optimal microwave absorption performance. When this material was loaded with 25 wt% paraffin and the thickness was 2.2 mm, an RL value of -27.5 dB was achieved at 13.92 GHz. minThe value reaches -53.07 dB and an effective absorption bandwidth of 6.4 GHz. Although combining ferromagnetic and carbon materials in a hybrid preparation can produce the desired composite absorption performance, the material cost still limits its widespread adoption.

[0004] In recent years, an increasing number of solid wastes have been used as raw materials for preparing microwave absorbing materials. Wang et al. prepared Co / C / CG composite materials with higher absorption intensity and a larger effective absorption bandwidth by controlling the type and state of carbon in starch (carbon source) and coal gangue (carrier) through temperature regulation. Zhu et al. synthesized nickel-containing fatty acid composite materials by using fly ash as raw material and employing a two-step method to liquefy it on the surface of a ceramic substrate. Ting et al. chose plasma melting technology to heat and quench municipal solid waste incineration fly ash, fixing it in epoxy resin and exploring its effect on the dielectric and magnetic properties of microwave absorbers. In summary, developing microwave absorbing materials from solid waste is not only feasible but also offers excellent performance. Coal gasification slag (CGFS) is also a solid waste from syngas production. Typically, it is a porous and lightweight sphere composed of an aluminosilicate glass matrix with dispersed iron phase components, similar to the structural characteristics of microwave absorbing materials. Due to its unique properties, it is often used as a filler for polymers, an adsorbent, and a raw material for cement preparation. Moreover, a number of microwave absorbing materials have been prepared using gasification slag as a carbon source. For example, He et al. prepared nitrogen-doped Fe2O3@CGFS composite materials with high-efficiency microwave absorption properties; Gao et al. prepared high-performance Fe@RC microwave absorbing materials. However, due to the complex composition of the fine slag, it must be treated before preparation, such as by acidification. However, acidification generates a large amount of acidic waste liquid, increasing the burden on waste liquid treatment. Therefore, it is urgent to develop a new preparation process to solve the environmental protection problem. Summary of the Invention

[0005] Based on the technical problems existing in the background technology, the present invention proposes a gasification fine slag-blended Fe3O4 composite material, its preparation method and application. The composite material exhibits good microwave absorption performance, which is manifested in high electromagnetic loss and wide absorption band.

[0006] The method for preparing Fe3O4-blended composite material from gasified fine slag proposed in this invention comprises the following steps:

[0007] S1: After mixing coal gasification fine slag and polyvinylpyrrolidone, add water and treat with ultrasound and stirring to obtain a suspension;

[0008] S2: Dissolve FeCl3·6H2O and FeCl2·4H2O in water respectively, then add them to the suspension of S1, mix well to obtain a mixed solution, and adjust the pH of the mixed solution to 10-11 with NH3·H2O to carry out the reaction.

[0009] S3: After the reaction, the product is washed and dried to obtain a gasified fine slag-infused Fe3O4 composite material.

[0010] Preferably, the molar ratio of coal gasification fine slag, polyvinylpyrrolidone, FeCl3·6H2O and FeCl2·4H2O is 2g:1g:1-10mmol:1-5mmol.

[0011] Preferably, the ultrasonic time in S1 is 5-15 min, and the stirring time is 10-20 min.

[0012] Preferably, the suspension in S1 is heated to 50-70°C after stirring.

[0013] Preferably, the reaction time in S2 is 1-3 hours.

[0014] Preferably, the drying temperature in S3 is 50-70℃ and the drying time is 8-16h.

[0015] The gasification fine slag and Fe3O4 composite material prepared by the above method proposed in this invention.

[0016] The present invention relates to the application of the above-mentioned gasification fine slag-infused Fe3O4 composite material in microwave absorption.

[0017] Beneficial technical effects of the present invention:

[0018] This invention synthesizes multi-interface Fe3O4@CGFS composite materials using a direct co-precipitation method. This method achieves high microwave absorption performance without acid hydrolysis, thus solving the environmental problems associated with existing preparation processes. These composite materials exhibit excellent microwave absorption properties, characterized by high electromagnetic loss and a wide absorption band. With a thickness of only 2.7 mm, the composite material achieves a high RL... min The absorption efficiency is -28.10 dB, while the effective bandwidth reaches 4.00 GHz with a thickness of 1.7 mm. The excellent microwave absorption performance of Fe3O4@CGFS composite material is due to its multi-interface structure and good electromagnetic impedance matching, as well as the cooperative effect between the dielectric and magnetic loss. Furthermore, CST simulations confirm that Fe3O4@FS-1 composite material possesses superior microwave absorption capabilities in practical radar stealth applications. Therefore, Fe3O4@CGFS composite material provides a simple solution for fabricating high-performance electromagnetic wave absorbers and can improve the resource utilization of CGFS. Attached Figure Description

[0019] Figure 1 The XRD pattern of (a) the CGFS and Fe3O4@CGFS composite material proposed in this invention; and (b) the FT-IR spectrum of CGFS and Fe3O4@CGFS.

[0020] Figure 2 Raman spectra of (a) Fe3O4@CGFS composite material proposed in this invention; (b) fitting peak fractionation results of Fe3O4@FS-1, (c) Fe3O4@FS-2 and (d) Fe3O4@FS-3;

[0021] Figure 3 The electromagnetic parameters (ε′, ε″; μ′, μ″) of (a) Fe3O4@FS-1, (b) Fe3O4@FS-2 and (c) Fe3O4@FS-3 proposed in this invention are as follows:

[0022] Figure 4 (a) Cole-Cole curve of Fe3O4 / CGFS composite material proposed in this invention; (b) Co curve of Fe3O4@CGFS composite material; (c) and (d) hysteresis loop of Fe3O4@CGFS composite material;

[0023] Figure 5 The present invention presents the reflection loss curves for (a) Fe3O4@FS-1, (b) Fe3O4@FS-2, and (c) Fe3O4@FS-3 at different thicknesses; and (d) the optimal RL of the Fe3O4@CGFS composite material. min and f B ;

[0024] Figure 6 The RL,t of (a) Fe3O4@FS-1, (b) Fe3O4@FS-2, and (c) Fe3O4@FS-3 proposed in this invention m , and |Z in The curve of / Z0| as a function of f;

[0025] Figure 7 XPS spectra of the Fe3O4@CGFS composite material proposed in this invention: (a) full spectrum, (b) C1s, (c) O1s, and (d) Fe2p;

[0026] Figure 8 The images provided in this invention are: (a) SEM image of Fe3O4@FS-2, (bc) EDS spectrum of Fe3O4@FS-2, and (de) corresponding TEM and electron diffraction images of Fe3O4@FS-2.

[0027] Figure 9 The present invention presents (a) an electromagnetic wave model in which electromagnetic waves pass only through PEC, (b) an electromagnetic wave model in which electromagnetic waves pass through PEC coated with Fe3O4@FS-1, and (c) RCS curves of PEC and PEC coated with Fe3O4@FS-1 at 10.00 GHz. Detailed Implementation

[0028] The present invention will be further explained below with reference to specific embodiments.

[0029] Example 1

[0030] A suspension was obtained by mixing gasified fine slag (CGFS) and polyvinylpyrrolidone (PVP) at a mass ratio of 2:1 and then adding the mixture to 50 mL of distilled water. The suspension was sonicated for 10 minutes, mechanically stirred for 15 minutes, and then heated to 60 °C. Subsequently, 1 mmol of FeCl3·6H2O and 0.5 mmol of FeCl2·4H2O were dissolved in 50 mL of distilled water respectively and stirred with the suspension to form a mixture. The mixture was stirred for 2 hours, and NH3·H2O was added dropwise to adjust the pH to 10. Finally, the solution was washed until neutral and dried at 60 °C for 12 hours to obtain the Fe3O4@CGFS composite material, denoted as Fe3O4@FS-1.

[0031] Example 2

[0032] CGFS and polyvinylpyrrolidone (PVP) were mixed at a mass ratio of 2:1 and then added to 50 mL of distilled water to obtain a suspension. The suspension was sonicated for 10 minutes, mechanically stirred for 15 minutes, and then heated to 60 °C to obtain a final suspension. Subsequently, 2 mmol of FeCl3·6H2O and 1 mmol of FeCl2·4H2O were dissolved in 50 mL of distilled water respectively and stirred with the suspension to form a mixture. The mixture was stirred for 2 hours, and NH3·H2O was added dropwise to adjust the pH to 10. Finally, the solution was washed until neutral and dried at 60 °C for 12 hours to obtain the Fe3O4@CGFS composite material, denoted as Fe3O4@FS-2.

[0033] Example 3

[0034] CGFS and polyvinylpyrrolidone (PVP) were mixed at a mass ratio of 2:1 and then added to 50 mL of distilled water to obtain a suspension. The suspension was sonicated for 10 minutes, mechanically stirred for 15 minutes, and then heated to 60 °C to obtain a final suspension. Subsequently, 3 mmol of FeCl3·6H2O and 1.5 mmol of FeCl2·4H2O were dissolved in 50 mL of distilled water respectively and stirred with the suspension to form a mixture. The mixture was stirred for 2 hours, and NH3·H2O was added dropwise to adjust the pH to 10. Finally, the solution was washed until neutral and dried at 60 °C for 12 hours to obtain the Fe3O4@CGFS composite material, denoted as Fe3O4@FS-1.

[0035] The crystal structure of the Fe3O4@CGFS composites prepared in Examples 1-3 was characterized by powder X-ray diffraction (XRD; Bruker, D8-Advance, Germany), with 2θ ranging from 15° to 80°. The infrared (IR) spectra of CGFS and Fe3O4@CGFS were obtained using Fourier transform infrared spectroscopy (FTIR; Bruker, VECTOR-33, Germany). The magnetic properties of Fe3O4@CGFS were tested using a vibrating sample magnetometer (Quantum Design, PPMS-9, USA). The structural stability of the Fe3O4@CGFS composites was analyzed using Raman spectroscopy (Renishaw, 2000, UK). The microstructure and size of CGFS and Fe3O4@CGFS were determined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) with a JEOL S-4800 (Japan) and a JEOL JEM-2100F (Japan), respectively. The elemental states of C, O, and Fe were analyzed using X-ray photoelectron spectroscopy (XPS; Thermo Fisher Scientific Inc ESCALABMK-II, the USA). Finally, the Fe3O4@CGFS composite material was mixed with paraffin at a 2:3 mass ratio and shaped into cylinders with an outer diameter of 7.00 mm and an inner diameter of 3.04 mm. The S-parameters of the Fe3O4@CGFS composite material were tested using an Agilent PNA-N5244A microwave network analyzer.

[0036] The XRD patterns of the three Fe3O4@CGFS composites showed obvious diffraction peaks at 30.12°, 35.53°, 43.18°, 53.73°, 57.26°, and 62.73°, respectively, corresponding to the (220), (311), (400), (422), (511), and (440) planes of Fe3O4 (JCPDS#19-0629). Figure 1 a). Two different planes of CGFS graphite, (002) and (100), were detected at 26.01° and 44.48°, respectively. The intensity of the diffraction peaks of Fe3O4NPs increased with increasing Fe3O4 content.

[0037] Figure 1 b shows the FTIR spectra of carbon / graphene fiber sheets (CGFS) and Fe3O4@CGFS composites at different concentrations of NP (Fe3O4). The characteristic peaks and corresponding functional groups are as follows: the peak corresponding to the –OH functional group is located at 3435.2 cm⁻¹. –1 At 2924.3cm –1 The peak at 1399.0 cm⁻¹ corresponds to the C–H tensile vibration peak. –1The tensile vibration peak at 1621.5 cm corresponds to the bending vibration in the O–H plane. Furthermore, at 1621.5 cm... –1 Up to 1542.8cm –1 The peak corresponds to the stretching vibration peak of the benzene ring skeleton. In the CGFS spectrum, at 1057.0 cm⁻¹ –1 Up to 990.7cm –1 The spectrum corresponds to C–C, C–O, and C–H peaks within the range. Compared to the spectrum of CGFS, the Fe3O4@CGFS composite material exhibits peaks at approximately 585 cm⁻¹. –1 A peak representing an Fe–O bond is observed. The intensity of this peak increases with increasing iron ion concentration in the reaction system. After the addition of magnetic NPs, these peaks show a shrinking trend and exhibit a "redshift." Therefore, it can be inferred that certain functional groups and NPs may have reacted during the fabrication of the Fe3O4@CGFS composite material.

[0038] The irregular carbon in CGFS is divided into four forms—G, D1, D2, D3, and D4—in Raman spectroscopy, corresponding to 1580, 1350, 1620, 1500, and 1200 cm⁻¹, respectively. –1 . Figure 2 The Raman spectra of the Fe3O4@CGFS composite material were analyzed, with values ​​at 1347.9 and 1599.0 cm⁻¹. –1 The D and G peaks were displayed at

[54] ,

[55] . The D peak was decomposed into three Lorentz bands (D1, D2 and D4 bands) and a Gaussian band (D3 band) and its intensity (I) was quantified. The I values ​​of FS, Fe3O4@FS-1, Fe3O4@FS-2 and Fe3O4@FS-3 were quantified. D / I G The values ​​were 2.50, 2.70, 3.13, and 3.54, respectively. D and I G The area ratios were 1.09, 1.02, 1.07, and 1.12, respectively. These two types of values ​​can be used to assess the degree of banding and electron mobility in the studied material. With the increase of magnetic NPs content in the Fe3O4@CGFS composite material, I... D1+D2+D3+D4 / I G and I D / I G The value also increases accordingly, indicating that the structural stability of CGFS is affected by magnetic NPs during high-temperature calcination and reduction. Furthermore, with increasing magnetic NP content, the Fe3O4@CGFS composite material exhibits more defects, which may be due to the catalytic effect of magnetic NPs on CGFS at 600℃.

[0039] The dielectric constant (εr = ε′ – jε″) and permeability (μr = μ′ – jμ″) of an electromagnetic wave absorber represent the storage and dissipation of electric and magnetic field energy, respectively, and determine its absorption capacity. The ε′ of the Fe3O4@CGFS composite material gradually decreases with increasing frequency, indicating an attenuation of EMW energy. Conversely, the values ​​of μ′ and ε″ are positively correlated with the Fe3O4 content, indicating that Fe3O4 affects the absorption performance. The slight upward trend in the Fe3O4@FS-1 range from 10.5 GHz to 12.5 GHz indicates polarization relaxation and multiple dual polarization phenomena. The behavior of the ε″ value is characterized by an initial decrease followed by an increase (…). Figure 3 (ac). Conversely, the values ​​of μ′ and μ″ show a decreasing trend, with multiple natural and exchange resonances at values ​​of 0 and 1. Numerous defects during the hydrothermal process will promote dipole polarization and Debye relaxation formation. This can be mathematically expressed using the Debye model, Equation 1:

[0040]

[0041] Each semicircle in the Cole-Cole curve is considered a Debye relaxation process, which is associated with an increase in the absorber's electromagnetic wave absorption capability. The Fe3O4@CGFS composites exhibit three distorted semicircles due to polarization relaxation at heterogeneous boundaries within the composite, enhancing dielectric loss, such as CGFS-air, CGFS-Fe3O4, and air-Fe3O4. Furthermore, upon exposure to electromagnetic waves, electrons in Fe3O4@CGFS absorb energy and migrate to the conductive carbon layer, forming a conductive network that promotes conductive loss.

[0042] Previous studies have shown that magnetoelectric absorbers exhibit eddy current losses, natural resonances, and exchange resonances, with magnetic losses being the primary contributor within the measured frequency range. Eddy current losses can be calculated using Equations 2 and 3:

[0043] μ”≈2πμ0(μ') 2 σd 2 f / 3 (2)

[0044] C0=μ(μ') 2 f -1 (3)

[0045] We assume that the magnetic loss comes from eddy current loss, and the value of C0 is (C0 = 2πμ0σd). 2 / 3 The magnetic loss remains constant with frequency, where μ0 represents the permeability of vacuum, σ represents the conductivity, and d represents the thickness of the object. However, the C0 value of the Fe3O4@CGFS composite material varies with frequency within the test range. Clearly, the magnetic loss is not due to eddy current loss. Figure 4a) The curve shows a significant decrease in the 2.0 GHz–9.0 GHz range, indicating that the magnetic loss is mainly caused by natural resonance; the significant fluctuations in the 9.0 GHz–18.0 GHz range are caused by exchange resonance. Therefore, the magnetic loss observed in the Fe3O4@CGFS composite material is mainly attributed to resonances generated by natural and exchange phenomena. To evaluate the electromagnetic wave absorption capability of the absorber, the attenuation coefficient (α) is an important indicator, which can be calculated using Equation 4:

[0046]

[0047] like Figure 4 As shown in b, in the 2.0 GHz–6.0 GHz range, the α value of the Fe3O4@CGFS composite follows the pattern Fe3O4@FS-1=Fe3O4@FS-2=Fe3O4@FS-3; in the 6.0 GHz–18.0 GHz range, Fe3O4@FS-1>Fe3O4@FS-2>Fe3O4@FS-3; and in the 12.0 GHz–18.0 GHz range, Fe3O4@FS-2>Fe3O4@FS-3>Fe3O4@FS-1. The results indicate that the NP content has a significant impact on the electromagnetic wave absorption capability of the Fe3O4@CGFS composite. Furthermore, Fe3O4@FS-1 exhibits a higher attenuation capability than Fe3O4@FS-2 in terms of electromagnetic wave absorption. This suggests that impedance matching is another crucial factor that should be considered.

[0048] Figure 4 The hysteresis loop of cd represents the magnetic properties of the Fe3O4@CGFS composite material: magnetic induction and permeability. These vary with the presence of magnetic NP. The saturation magnetization (Ms) values ​​of Fe3O4@FS-1, Fe3O4@FS-2, and Fe3O4@FS-3 are 12.2, 23.9, and 30.7 emu·g, respectively. –1 Their coercivity (Hc) is approximately 9.14, 27.8, and 63.3 Oe, respectively. With the increase of magnetic NP content, Ms increases and enhances the dissipation of incident electromagnetic wave energy.

[0049] Formulas (5) and (6) calculate RL, a parameter used to evaluate the absorber's ability to absorb EMW:

[0050]

[0051] RL = 20log|(Z) in -Z0) / (Z in +Z0)| (6)

[0052] Z of Fe3O4@CGFS / paraffin complex inAnd Z0, microwave frequency f, speed of light c, absorber thickness d, complex dielectric constant ε r and permeability μ r related. Figure 5 As shown in Figure ac, the Fe3O4@CGFS absorber exhibits a long effective bandwidth f B When t RL The minimum reflection loss (RL) of the Fe3O4@FS-1 composite material at a frequency of 10.00 GHz and a diameter of 2.7 mm is [value missing]. min The value is -28.03 dB, f B Reaching 3.36GHz (9.14GHz-12.50GHz) Figure 5 a) The RL of the Fe3O4@FS-2 composite material at 4.32 GHz. min -27.34 dB; f B Reaching 4.00GHz (13.52-17.52GHz), the corresponding thickness is 1.7mm. Figure 5 b). The Fe3O4@FS-3 absorber at 4.48 GHz RL min -21.45dB, f B Reaching 3.84GHz (13.92GHz-17.84GHz), t RL It is 1.8mm ( Figure 5 c) Best RL min and f B Displayed Figure 5 d. The addition of NP enhances the electromagnetic wave absorption properties of the material. Optimal absorption performance is achieved by adding 2.0 mmol FeCl3·6H2O + 1.0 mmol FeCl2·4H2O.

[0053]

[0054] According to the theory of λ / 4 matching, when t m and f m When Equation 7 is satisfied, phase cancellation occurs, resulting in a reduction in the incident electromagnetic wave. Figure 6 The RL of the Fe3O4@CGFS composite material and the thickness (t) of the absorber were described. m ) and |Z in The behavior of / Z0| and the f curve. With t m As the frequency decreases, the RL peak shifts to higher frequency bands. Furthermore, t m All experimental values ​​(represented by diamonds) are consistent with the λ / 4 matching theoretical curve, indicating that the λ / 4 thickness of the material is the optimal impedance matching. For impedance matching, a thickness of 2.7 mm corresponds to |Z in / Z0| is closest to 1, which is consistent with the observed RL of Fe3O4@CGFS composites.min The matching thickness is consistent. Therefore, |Z| can be further improved. in / Z0| and RL, while reducing the material thickness to improve its performance. When the absorption performance reaches RL min At frequency, |Z in The / Z0| value converges to 1. This is because the Fe3O4@FS-1 composite material exhibits enhanced impedance matching and superior absorption capabilities, outperforming other materials in wave absorption. Furthermore, the three materials show improved impedance matching at ε... r and μ r Maintaining a balance between them.

[0055] To determine the ionic valence states and compound types present in the Fe3O4@CGFS composite material, to speculate on the reaction between FS and NP, and to reveal the cause of the electromagnetic wave absorption characteristics, XPS analysis was performed on the FS and Fe3O4@FS-2 composite material. CGFS produces a C1s peak ( Figure 7 b) Both magnetic Fe3O4 and CGFS produce O1s peaks. It can be inferred that oxygen-containing functional groups formed by the combination of C═O, C–O, and Fe–O can act as polarization centers, promoting dipole polarization and polarization relaxation. Magnetic Fe3O4 produces Fe2p peaks, which can be divided into six peaks: Fe2p3 / 2 (711.1 eV), Fe2p1 / 2 (725.5 eV), Fe… 2+ 2p3 / 2 (709.2 eV), Fe 2+ sat2p3 / 2 (713.4 eV), Fe 2+ 2p1 / 2 (723.7 eV), Fe 2+ sat2p1 / 2 (729.5 eV), Fe 3+ sat2p3 / 2 (718.8 eV) and Fe 3+ sat2p1 / 2 (733.7eV).

[0056] The unique properties of Fe3O4@CGFS composites are not only related to their elemental states; to further explore the microscopic distribution of NPs in CGFS, their morphology needs to be analyzed. (Taking Fe3O4@FS-2 as an example.) SEM analysis was performed to study the morphology of CGFS and Fe3O4@CGFS composites. Figure 8 a). SEM images show that the surface of CGFS is inhomogeneous and layered, while images of the Fe3O4@CGFS composite material indicate the presence of NP aggregation on the surface of CGFS, leading to enhanced magnetic loss. Figure 8 Elemental distribution results show that Fe3O4@FS-2 contains C, O, Al, Si, and Fe, with corresponding mass fractions of 64.27, 21.57, 2.08, 2.79, and 9.30 wt.%, respectively. Figure 8c). The distribution of iron is uniform throughout the sample, while carbon and oxygen show localized concentrations. These results indicate that the Fe3O4@CGFS composite contains iron in different valence states. TEM images of the structure of the Fe3O4@CGFS composite show that the diameters of the magnetic Fe3O4NPs range from 10 to 40 nm, and they are spherical or nearly spherical. Figure 8 d). The interplanar distances between the (040) and (311) planes of Fe3O4NPs were found to be 0.21 and 0.25 nm, respectively. Figure 8 e). Due to the stable interaction forces and the tight bond between the magnetic NP and the CGFS matrix, the magnetic NP remains intact during ultrasonic processing and TEM sample preparation.

[0057] In summary, the microwave absorption capability of the Fe3O4@CGFS composite material is the result of a synergistic coupling of multiple properties, including impedance matching, electromagnetic parameters, and multi-dielectric loss. The fundamental mechanism involves the heterojunction interface formed between Fe3O4NP and CGFS, leading to the amplification of NP-C interface polarization within the system. In a microwave field, interfacial polarization loss occurs because the polarization cannot keep up with changes in the external electric field. Furthermore, under an electromagnetic field, defects and heteroatoms in the graphitized region can act as double poles, inducing dual polarization. Due to the synergistic effect of interfacial polarization, dipole polarization, conductivity, and microcurrent networks, this composite material exhibits good dielectric loss, resulting in excellent microwave energy absorption. Through its multiphase composition, this FS-based composite material can achieve ultra-wideband EWA, demonstrating its enormous potential for microwave device applications.

[0058] RCS (Radar Cross Section) is a critical parameter in the development of stealth aircraft to avoid radar detection. Therefore, this paper uses CSTStudioSuite2022 software to evaluate the RCS value of the Fe3O4@CGFS composite material to determine its practical feasibility in the far field. A coating model was constructed using a 180mm × 180mm PEC layer (0.5mm) and the Fe3O4@CGFS composite material (2.70mm). Figure 9 The results show the three-dimensional attenuation radar intensity model and RCS value curves of the PEC layer and the Fe3O4@FS-1 coated PEC in the range of –90° to 90° at 10 GHz. The results indicate that the lowest RCS value of the Fe3O4@FS-1 coated PEC is approximately –5 dBm. 2 The value is significantly lower than the minimum value of the PEC model. Therefore, Fe3O4@FS-1 has the ability to attenuate radar electromagnetic waves at all angles. Thus, Fe3O4@CGFS composite materials have considerable future applicability and practicality.

Claims

1. A method for preparing a gasified fine slag blended Fe304 composite material, characterized by, The method steps are as follows: S1: mixing coal gasification fine slag and polyvinylpyrrolidone, then adding water, and treating by ultrasonic and stirring to obtain a suspension; S2: dissolving FeCl3·6H2O and FeCl2·4H2O in water respectively, then adding the suspension of S1, mixing, adjusting the pH of the mixture to 10-11 by NH3·H2O, and reacting; S3: washing and drying the product after the reaction to obtain a gasification fine slag doped with Fe3O4 composite material; The mass molar ratio of the coal gasification fine slag, polyvinylpyrrolidone, FeCl3·6H2O and FeCl2·4H2O is 2g:1g:1-10mmol:1-5mmol; The ultrasonic time in S1 is 5-15min, and the stirring time is 10-20min; The suspension after stirring in S1 is heated to 50-70℃.

2. The method of claim 1, wherein the Fe304 composite material is prepared by mixing the gasified fine slag with Fe304. The reaction time in S2 is 1-3h.

3. The method of claim 1, wherein the Fe304 composite material is prepared by mixing the gasified fine slag with Fe304. The drying temperature in S3 is 50-70℃, and the time is 8-16h.

4. The gasification fine slag doped with Fe3O4 composite material prepared by the method according to any one of claims 1-3.

5. The application of the gasification fine slag doped with Fe3O4 composite material according to claim 4 in wave absorption.

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