A transition metal oxide and / or transition metal sulfide / carbon cloth composite wave-absorbing material and a preparation method thereof

Abstract

The application discloses a preparation method of a transition metal oxide and / or transition metal sulfide / carbon cloth composite wave-absorbing material, and belongs to the technical field of wave-absorbing materials. The method comprises the following steps: dissolving metal salt and sodium citrate in a mixed solvent to obtain a mixed solution; immersing hydrophilic carbon cloth treated by acid in the mixed solution, and then moving to a hydrothermal kettle for heat preservation treatment to obtain a transition metal oxide / carbon cloth; dissolving a sulfur-containing compound in an alcohol solution, immersing the transition metal oxide / carbon cloth in the alcohol solution containing the sulfur-containing compound, and then moving to the hydrothermal kettle for heat preservation treatment; adjusting the temperature and time of the heat preservation treatment to control the content of sulfide in the product, and finally obtaining a transition metal oxide / sulfide / carbon cloth or a transition metal sulfide / carbon cloth. The application further discloses the obtained transition metal oxide and / or transition metal sulfide / carbon cloth composite wave-absorbing material. The method is simple, the micro-morphology and components of the obtained material are controllable, the material has excellent wave-absorbing performance, and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to the field of flexible microwave absorbing materials, and more specifically to a transition metal oxide and / or transition metal sulfide / carbon cloth composite microwave absorbing material and its preparation method. Background Technology

[0002] With the advancement of modern technology and the rapid development of information technology, especially with the rapid development of 5G technology, electronic devices are constantly evolving towards higher frequencies and increasing power. The environmental impact of leaked electromagnetic radiation is becoming increasingly significant. Furthermore, with the expanding market for wearable electronics, high-performance flexible absorbing materials have become an important direction for future development.

[0003] Carbon fiber woven fabric has important applications in many research fields due to its excellent self-supporting structure, flexibility, thermal stability, chemical stability, and high conductivity. However, the high conductivity of carbon fabric can easily lead to impedance mismatch, causing electromagnetic wave reflection and hindering electromagnetic wave absorption. Therefore, achieving good impedance matching is a key research focus. To improve this problem, modifying the surface of carbon fabric with semiconductor materials may be an effective measure.

[0004] Transition metal salts, oxides, and sulfides are considered good surface modification materials for carbon cloth due to their controllable microstructure and simple synthesis methods. Patent application CN114421180A discloses a method for preparing a needle-shaped nickel cobalt oxide / hydrophilic carbon cloth microwave absorbing composite material. This method involves impregnating hydrophilic carbon cloth in a mixture of nickel salt, cobalt salt, and urea, then transferring it to an autoclave for hydrothermal treatment to obtain a needle-shaped nickel cobalt oxide precursor / hydrophilic carbon cloth. The carbon cloth material is then subjected to heat treatment under different atmospheres to obtain the needle-shaped nickel cobalt oxide / hydrophilic carbon cloth microwave absorbing composite material.

[0005] The invention patent application with publication number CN115323766A discloses a method for preparing a cobalt tetroxide / carbon cloth flexible microwave absorbing material. The method involves adding acid-treated carbon cloth to a mixture of cobalt salt and dimethylimidazole to obtain a cobalt-metal-organic framework / carbon cloth, and then annealing the carbon cloth in an air atmosphere to obtain the cobalt tetroxide / carbon cloth flexible microwave absorbing material.

[0006] While existing technologies have laid some foundation for the research of carbon cloth absorbing composite materials, current modifications to the carbon cloth surface are mostly single materials, and the reported control methods are primarily based on microstructure and defect manipulation, offering limited control over absorption performance and failing to meet current application requirements. Constructing heterojunction structures, however, can optimize the carrier transport characteristics of semiconductors, enhance conduction and polarization losses, and significantly alter the electromagnetic parameters of the material through different heterojunction morphologies, thereby achieving a wide range of impedance matching adjustments to meet diverse needs. Therefore, further research is needed to effectively construct heterojunction structures on the carbon cloth surface to improve the material's electromagnetic wave absorption performance. Summary of the Invention

[0007] To address the aforementioned problems, this invention provides a method for preparing a transition metal oxide / carbon cloth composite microwave absorbing material. This invention utilizes a hydrothermal treatment method to prepare the transition metal oxide / carbon cloth. This preparation method is simple, and the resulting carbon cloth material exhibits excellent electromagnetic absorption performance, meeting the requirements for flexible applications.

[0008] A method for preparing a transition metal oxide / carbon cloth composite microwave absorbing material includes the following steps:

[0009] (1) Add the metal salt and sodium citrate to a mixed solvent of ethanol and water, and then stir until completely dissolved to obtain a mixed solution;

[0010] (2) The hydrophilic carbon cloth was placed in a nitric acid solution, ultrasonically treated, then removed, washed, and dried to obtain the acid-treated hydrophilic carbon cloth.

[0011] (3) The acid-treated hydrophilic carbon cloth is placed in the mixed solution obtained in step (1), and the hydrophilic carbon cloth is completely wetted to obtain a mixture of solution and carbon cloth.

[0012] (4) The mixture of solution and carbon cloth is transferred to a hydrothermal reactor and kept at a constant temperature. After the reaction is completed and the reactor is cooled to room temperature, the carbon cloth is taken out, washed and dried to obtain a transition metal oxide / carbon cloth composite microwave absorbing material.

[0013] Preferably, the metal salt is one or more metal anions such as chloride, nitrate, and sulfate of the corresponding transition metal.

[0014] Preferably, the molar ratio of the metal salt to sodium citrate is 1:0.1-5, the volume ratio of ethanol to water in the mixture of ethanol and water is 1:0.1-10, and the mass ratio of the mixed solvent to the mixed solution is 1:5-50.

[0015] Preferably, the mass ratio of the hydrophilic carbon cloth to the nitric acid solution is 1:50-300, and the concentration of the nitric acid solution is 5-40 wt%.

[0016] Preferably, the impregnation is performed by placing a mixture of solution and carbon cloth in a vacuum chamber and subjecting it to vacuum treatment.

[0017] Preferably, the heat preservation temperature is 110-180℃ and the heat preservation time is 2-24 hours.

[0018] Preferably, the transition metal oxide includes oxides of various valence states of transition metals such as Fe, Co, Ni, Cu, Zn, or Sn.

[0019] More preferably, the transition metal oxide is Fe2O3, Co3O4, NiO, CuO, ZnO, or SnO2, etc.

[0020] The present invention also provides a transition metal oxide / carbon cloth composite microwave absorbing material obtained by the above preparation method.

[0021] This invention also provides a method for preparing transition metal sulfide / carbon cloth composite absorbing materials or transition metal oxide / transition metal sulfide / carbon cloth composite absorbing materials. This method mainly addresses the problem of insufficient control over the absorption performance of current single semiconductor materials by constructing a heterojunction interface on the surface of the carbon cloth. The preparation process is simple, the microstructure and composition of the obtained material are controllable, and it can significantly improve the electromagnetic wave absorption performance of the material.

[0022] A method for preparing a transition metal sulfide / carbon cloth composite microwave absorbing material or a transition metal oxide / transition metal sulfide / carbon cloth composite microwave absorbing material includes the following steps:

[0023] (1) Add the sulfur-containing compound to the alcohol solution and stir until completely dissolved to obtain a mixed solution of the sulfur-containing compound;

[0024] (2) The transition metal oxide / carbon cloth composite microwave absorbing material prepared above is placed into the mixed solution of sulfur-containing compounds above and soaked to obtain a mixture of sulfur-containing compound solution and transition metal oxide / carbon cloth composite microwave absorbing material;

[0025] (3) The mixture of sulfur-containing compound solution and transition metal oxide / carbon cloth composite microwave absorbing material is transferred to a hydrothermal reactor and kept warm. The content of transition metal sulfides in the reaction product is controlled by adjusting the temperature and time of the heat preservation treatment. After the reaction is completed, the carbon cloth is taken out after the reactor is cooled to room temperature, washed and dried to obtain transition metal oxide / transition metal sulfide / carbon cloth composite microwave absorbing material or transition metal sulfide / carbon cloth composite microwave absorbing material.

[0026] Different reaction temperatures can control the activity of sulfur (S) in solution. S has a lower electronegativity than oxygen (O). Under high temperature and high pressure reaction conditions rich in S, S tends to replace oxygen. The higher the temperature, the stronger its activity and the easier it is to replace oxygen in oxides. Different holding times can control the development of its crystal structure and better grow specific micromorphologies.

[0027] This invention controls the content of transition metal sulfides in the reaction products by adjusting the temperature and time of the heat treatment. Preferably, temperature adjustment is used, as the higher the temperature, the shorter the time required for the oxide to be completely converted into sulfides.

[0028] This invention allows for the matching of the holding temperature and time according to different reaction raw materials, the amount of raw materials, and the required content of transition metal sulfides in the final product, to obtain the desired product. Preferably, the matching is performed within the range of a holding temperature of 100-240℃ and a holding time of 2-24 hours.

[0029] Preferably, when the heat preservation temperature is between 100-220℃ and the heat preservation time is within 10 hours, the reaction product is a transition metal oxide / transition metal sulfide / carbon cloth composite microwave absorbing material.

[0030] Preferably, when the heat preservation temperature exceeds 200°C and the heat preservation time exceeds 6 hours, the oxide is completely converted into sulfide, and the reaction product is a transition metal sulfide / carbon cloth composite microwave absorbing material.

[0031] By constructing heterojunction structures of different transition metal oxides / transition metal sulfides on the surface of carbon cloth through a secondary hydrothermal reaction, the carrier transport performance of the material is changed, the electromagnetic parameters of the material are adjusted over a wide range, thereby enhancing the material's ability to absorb electromagnetic waves, optimizing impedance matching, and improving wave absorption performance.

[0032] Preferably, the sulfur-containing compound is thiourea, thioacetamide, or sodium sulfide, etc.; the organic alcohol solution is an alcohol solution such as methanol, ethanol, or isopropanol; and the mass ratio of the sulfur-containing compound to the organic alcohol solution is 1:5-50.

[0033] Preferably, the transition metal sulfides include sulfides of various valence states of transition metals such as Fe, Co, Ni, Cu, Zn, or Sn.

[0034] More preferably, the transition metal sulfide is FeS2, CoS2, NiS, CuS, ZnS, or SnS2, etc.

[0035] This invention also provides a transition metal oxide / transition metal sulfide / carbon cloth composite absorbing material or a transition metal sulfide / carbon cloth composite absorbing material prepared by the above method. The surface of the transition metal oxide / transition metal sulfide / carbon cloth composite absorbing material exhibits a heterogeneous phase interface structure, and its electromagnetic wave absorption performance is higher than that of its corresponding transition metal oxide / carbon cloth composite absorbing material or transition metal sulfide / carbon cloth composite absorbing material. That is, this material possesses a larger effective bandwidth and a lower maximum reflectivity compared to its corresponding individual transition metal oxide or transition metal sulfide / carbon cloth.

[0036] Compared with the prior art, the present invention has at least the following beneficial effects:

[0037] (1) The preparation method of the present invention is simple, the microstructure and composition of the carbon cloth composite material are controllable, and it can meet the needs of flexible applications.

[0038] (2) Compared with modifying the surface of carbon cloth with a single material, this invention uses a two-stage hydrothermal reaction method to prepare a composite microwave absorbing material of transition metal oxide / transition metal sulfide / carbon cloth. This method constructs different heterojunction structures of transition metal oxide / sulfide on the surface of carbon cloth, thereby changing the carrier transport performance of the resulting composite microwave absorbing material, adjusting the electromagnetic parameters of the material over a wide range, thereby enhancing the material's ability to absorb electromagnetic waves, optimizing impedance matching, and improving microwave absorption performance, which can meet the requirements of thin layer, wide bandwidth, and strong absorption. Attached Figure Description

[0039] Figure 1 This is a flowchart illustrating the preparation process of the carbon cloth composite microwave absorbing material according to an embodiment of the present invention.

[0040] Figure 2 The images are XRD images of the carbon cloth composite microwave absorbing materials prepared in Examples 1-3 of this invention.

[0041] Figure 3 These are SEM and HRTEM images of the SnO2 / SnS2 / carbon cloth prepared in Example 2 of this invention, wherein... Figure 3 a is the SEM image. Figure 3 b is the HRTEM image;

[0042] Figure 4 The reflection loss spectrum of the SnO2 / carbon cloth prepared in Example 1 of this invention in the 2-18 GHz frequency band;

[0043] Figure 5 The reflection loss spectrum of the SnO2 / SnS2 / carbon cloth prepared in Example 2 of the present invention in the 2-18 GHz frequency band;

[0044] Figure 6The reflection loss spectrum of the SnS2 / carbon cloth prepared in Example 3 of this invention in the 2-18 GHz frequency band;

[0045] Figure 7 The reflection loss spectrum of the ZnO / ZnS / carbon cloth prepared in Example 1 of this invention in the 2-18 GHz frequency band;

[0046] Figure 8 The reflection loss spectrum of the NiO / NiS / carbon cloth prepared in Example 2 of this invention is shown in the 2-18 GHz frequency band. Detailed Implementation

[0047] The present invention will be further described below with reference to specific embodiments. Obviously, the embodiments described below are only a part of typical embodiments of the present invention and are merely used to explain the present invention and not to limit it. Furthermore, based on the embodiments of the present invention, those skilled in the art can make various modifications or alterations. Therefore, any simple modifications, alterations, equivalent substitutions, and equivalent changes made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention's technical solution are all within the protection scope of the present invention's technical solution.

[0048] Figure 1 This is a flowchart illustrating the preparation process of the carbon cloth composite microwave absorbing material according to an embodiment of the present invention. Figure 1 As shown, the preparation method includes the following steps:

[0049] (1) Add the metal salt and sodium citrate to V 水 V 乙醇 In a 1:1 mixture of solutions, stir magnetically until completely dissolved to obtain a mixed solution;

[0050] (2) The hydrophilic carbon cloth was placed in a 10 wt% nitric acid solution, ultrasonically treated for 1 hour, then removed, washed and dried to obtain the acid-treated hydrophilic carbon cloth.

[0051] (3) Place the acid-treated hydrophilic carbon cloth in the mixed solution in step (1), transfer it into a vacuum chamber and vacuum process for 30 minutes to completely wet the carbon cloth with the solution and obtain a mixture of solution and carbon cloth.

[0052] (4) The mixture of solution and carbon cloth is transferred to a hydrothermal reactor and kept at 160°C for 12 hours. After the reaction is completed, the reactor is cooled to room temperature and the carbon cloth is taken out, washed and dried to obtain the product transition metal oxide / carbon cloth composite microwave absorbing material.

[0053] (5) Add thioacetamide to the isopropanol solution and stir magnetically until completely dissolved to obtain a mixed solution containing sulfur compounds;

[0054] (6) The transition metal oxide / carbon cloth composite microwave absorbing material obtained in step (4) is placed in a mixed solution containing sulfur compounds, and after soaking, it is transferred to a hydrothermal reactor. The content of transition metal sulfides in the reaction product is controlled by adjusting the temperature and time of the heat treatment. After the reaction is completed, the reactor is cooled to room temperature and the carbon cloth is taken out, washed and dried to obtain the product transition metal sulfide / carbon cloth composite microwave absorbing material or transition metal oxide / transition metal sulfide / carbon cloth composite microwave absorbing material.

[0055] The present invention will be further described below with reference to specific embodiments.

[0056] Example 1

[0057] This embodiment demonstrates a method for preparing a SnO2 / carbon cloth composite microwave absorbing material according to the following steps:

[0058] (1) Add 0.45g of tin chloride dihydrate and 0.6g of sodium citrate to 35mL of V 水 V 乙醇 Add the mixture to a 1:1 ratio solution and then stir magnetically until completely dissolved to obtain a mixed solution.

[0059] (2) The hydrophilic carbon cloth was placed in a 10 wt% nitric acid solution, ultrasonically treated for 1 hour, then removed, washed and dried to obtain the acid-treated hydrophilic carbon cloth.

[0060] (3) Place the acid-treated hydrophilic carbon cloth in the mixed solution in step (1), transfer it into a vacuum chamber and vacuum process for 30 minutes to completely wet the carbon cloth with the solution and obtain a mixture of solution and carbon cloth.

[0061] (4) The mixture of the above solution and carbon cloth is transferred to a hydrothermal reactor and kept at 160°C for 12 hours. After the reaction is completed, the reactor is cooled to room temperature and the carbon cloth is taken out. After washing and drying, the SnO2 / carbon cloth composite microwave absorbing material is obtained.

[0062] Example 2

[0063] This embodiment demonstrates a method for preparing a SnO2 / SnS2 / carbon cloth composite microwave absorbing material according to the following steps:

[0064] (1) Add 0.45g of tin chloride dihydrate and 0.6g of sodium citrate to 35mL of V 水 V 乙醇 Add the mixture to a 1:1 ratio solution and then stir magnetically until completely dissolved to obtain a mixed solution.

[0065] (2) The hydrophilic carbon cloth was placed in a 10 wt% nitric acid solution, ultrasonically treated for 1 hour, then removed, washed and dried to obtain the acid-treated hydrophilic carbon cloth.

[0066] (3) Place the acid-treated hydrophilic carbon cloth in the mixed solution in step (1), transfer it into a vacuum chamber and vacuum process for 30 minutes to completely wet the carbon cloth with the solution and obtain a mixture of solution and carbon cloth.

[0067] (4) The mixture of solution and carbon cloth is transferred to a hydrothermal reactor and kept at 160°C for 12 hours. After the reaction is completed, the reactor is cooled to room temperature and the carbon cloth is taken out. After washing and drying, the product SnO2 / carbon cloth composite microwave absorbing material is obtained.

[0068] (5) Add 0.375g of thioacetamide to 35mL of isopropanol solution and stir magnetically until completely dissolved to obtain a mixed solution containing sulfur compounds;

[0069] (6) The SnO2 / carbon cloth composite microwave absorbing material obtained in step (4) is placed into the mixed solution of sulfur-containing compounds in step (5), and after wetting, it is transferred to a hydrothermal reactor and kept at 180°C for 10 hours. After the reaction is completed, the reactor is cooled to room temperature and the carbon cloth is taken out, washed and dried to obtain the product SnO2 / SnS2 / carbon cloth composite microwave absorbing material.

[0070] Example 3

[0071] This embodiment demonstrates a method for preparing a SnS2 / carbon cloth composite microwave absorbing material according to the following steps:

[0072] (1) Add 0.45g of tin chloride dihydrate and 0.6g of sodium citrate to 35mL of V 水 V 乙醇 Add the mixture to a 1:1 ratio solution and then stir magnetically until completely dissolved to obtain a mixed solution.

[0073] (2) The hydrophilic carbon cloth was placed in a 10 wt% nitric acid solution, ultrasonically treated for 1 hour, then removed, washed and dried to obtain the acid-treated hydrophilic carbon cloth.

[0074] (3) Place the acid-treated hydrophilic carbon cloth in the mixed solution in step (1), transfer it into a vacuum chamber and vacuum process for 30 minutes to completely wet the carbon cloth with the solution and obtain a mixture of solution and carbon cloth.

[0075] (4) The mixture of solution and carbon cloth is transferred to a hydrothermal reactor and kept at 160°C for 12 hours. After the reaction is completed, the reactor is cooled to room temperature and the carbon cloth is taken out. After washing and drying, the product SnO2 / carbon cloth composite microwave absorbing material is obtained.

[0076] (5) Add 0.375g of thioacetamide to 35mL of isopropanol solution and stir magnetically until completely dissolved to obtain a mixed solution containing sulfur compounds;

[0077] (6) The SnO2 / carbon cloth composite microwave absorbing material obtained in step (4) is placed into the mixed solution of sulfur-containing compounds in step (5), and after wetting, it is transferred to a hydrothermal reactor and kept at 220°C for 10 hours. After the reaction is completed, the reactor is cooled to room temperature and the carbon cloth is taken out, washed and dried to obtain the product SnS2 / carbon cloth composite microwave absorbing material.

[0078] Example 4

[0079] This embodiment demonstrates a method for preparing a ZnO / ZnS / carbon cloth composite microwave absorbing material according to the following steps:

[0080] (1) Add 0.27g zinc chloride and 0.6g sodium citrate to 35mL of V 水 V 乙醇 Add the mixture to a 1:1 ratio solution and then stir magnetically until completely dissolved to obtain a mixed solution.

[0081] (2) The hydrophilic carbon cloth was placed in a 10 wt% nitric acid solution, ultrasonically treated for 1 hour, then removed, washed and dried to obtain the acid-treated hydrophilic carbon cloth.

[0082] (3) Place the acid-treated hydrophilic carbon cloth in the mixed solution in step (1), transfer it into a vacuum chamber and vacuum process for 30 minutes to completely wet the carbon cloth with the solution and obtain a mixture of solution and carbon cloth.

[0083] (4) The mixture of solution and carbon cloth is transferred to a hydrothermal reactor and kept at 160°C for 12 hours. After the reaction is completed, the reactor is cooled to room temperature and the carbon cloth is taken out. After washing and drying, the product ZnO / carbon cloth composite microwave absorbing material is obtained.

[0084] (5) Add 0.375g of thioacetamide to 35mL of isopropanol solution and stir magnetically until completely dissolved to obtain a mixed solution containing sulfur compounds;

[0085] (6) The ZnO / carbon cloth composite microwave absorbing material obtained in step (4) is placed into the mixed solution of sulfur-containing compounds in step (5), and after soaking, it is transferred to a hydrothermal reactor and kept at 180°C for 10 hours. After the reaction is completed, the reactor is cooled to room temperature and the carbon cloth is taken out, washed and dried to obtain the product ZnO / ZnS / carbon cloth composite microwave absorbing material.

[0086] Example 5

[0087] This embodiment demonstrates a method for preparing a NiO / NiS / carbon cloth composite microwave absorbing material according to the following steps:

[0088] (1) Add 0.48g of nickel chloride hexahydrate and 0.6g of sodium citrate dihydrate to 35mL of V 水 V 乙醇Add the mixture to a 1:1 ratio solution and then stir magnetically until completely dissolved to obtain a mixed solution.

[0089] (2) The hydrophilic carbon cloth was placed in a 10 wt% nitric acid solution, ultrasonically treated for 1 hour, then removed, washed and dried to obtain the acid-treated hydrophilic carbon cloth.

[0090] (3) Place the acid-treated hydrophilic carbon cloth in the mixed solution in step (1), transfer it into a vacuum chamber and vacuum process for 30 minutes to completely wet the carbon cloth with the solution and obtain a mixture of solution and carbon cloth.

[0091] (4) The mixture of solution and carbon cloth is transferred to a hydrothermal reactor and kept at 160°C for 12 hours. After the reaction is completed, the reactor is cooled to room temperature and the carbon cloth is taken out. After washing and drying, the product NiO / carbon cloth composite microwave absorbing material is obtained.

[0092] (5) Add 0.375g of thioacetamide to 35mL of isopropanol solution and stir magnetically until completely dissolved to obtain a mixed solution containing sulfur compounds;

[0093] (6) The NiO / carbon cloth composite microwave absorbing material obtained in step (4) is placed into the mixed solution of sulfur-containing compounds in step (5), and after wetting, it is transferred to a hydrothermal reactor and kept at 180°C for 10 hours. After the reaction is completed, the reactor is cooled to room temperature and the carbon cloth is taken out, washed and dried to obtain the product NiO / NiS / carbon cloth composite microwave absorbing material.

[0094] The transition metal oxide and / or transition metal sulfide / carbon cloth composite microwave absorbing materials prepared in Examples 1-5 were tested.

[0095] The microstructure of the carbon cloth composite microwave absorbing materials prepared in Examples 1-3 was analyzed using a scanning electron microscope (SEM; model: Verios G4 UC). The heterogeneous interfaces of the materials were observed using a transmission electron microscope (TEM; model: JEOL-2011TEM). The carbon cloth microwave absorbing materials prepared in Examples 1-5 were uniformly mixed with molten paraffin at a mass ratio of 1:9 (i.e., absorber content of 10 wt%), and pressed into standard coaxial ring samples with an inner diameter of 3.0 mm, an outer diameter of 7.0 mm, and a thickness of 2.0 mm in a specially designed mold. The electromagnetic properties of each sample in the electromagnetic wave range of 2-18 GHz were tested using a vector network analyzer (VNA; model: Agilent N5234A) employing the coaxial method.

[0096] Based on the test results, the following conclusions were drawn:

[0097] The XRD spectra of the carbon cloth absorbing materials prepared in Examples 1-3 are as follows: Figure 2As shown, the XRD patterns of the samples obtained in Examples 1 and 3 show diffraction peaks of SnO2 and SnS2, respectively, indicating that Examples 1 and 3 correspond to pure SnO2 / carbon cloth composite absorbing materials and pure SnS2 / carbon cloth composite absorbing materials, respectively. However, the XRD pattern of the sample obtained in Example 2 shows diffraction peaks of both pure SnO2 and SnS2, indicating that SnO2 and SnS2 are present simultaneously in the carbon cloth composite absorbing material prepared in Example 2.

[0098] Figure 3 SEM image of the SnO2 / SnS2 / carbon cloth composite microwave absorbing material prepared in Example 2 of this invention. Figure 3 a) and HRTEM Figure 3 b) Image. See also Figure 3 SEM image of a, showing that in Example 2, the SnO2 and SnS2 arrays grown on the carbon cloth surface are uniformly and vertically distributed on the carbon cloth fibers. See also Figure 3 b is an HRTEM image, which shows a clear heterogeneous phase interface structure on the carbon cloth, confirming the existence of the SnO2 / SnS2 heterogeneous interface in the carbon cloth sample of Example 2.

[0099] Figure 4 The electromagnetic wave absorption performance of the SnO2 / carbon cloth absorbing material sample described in Example 1 is shown. When the matching thickness is 2.0 mm, the SnO2 / carbon cloth absorbing material has an effective bandwidth of 5.7 GHz in the 2–18 GHz frequency band and a maximum reflectivity of -29.8 dB.

[0100] Figure 5 The electromagnetic wave absorption performance of the SnO2 / SnS2 / carbon cloth absorbing material sample described in Example 2 is shown. When the matching thickness is 2.0 mm, the effective bandwidth is 9.8 GHz in the 2–18 GHz frequency band, and the maximum reflectivity is -44 dB.

[0101] Figure 6 The electromagnetic wave absorption performance of the SnS2 / carbon cloth composite absorbing material sample described in Example 3 is shown. When the matching thickness is 2.0 mm, the effective bandwidth is 0.9 GHz in the 2–18 GHz frequency band, and the maximum reflectivity is -15 dB.

[0102] contrast Figure 4-6 The reflection loss spectrum of the obtained carbon cloth composite absorbing materials showed that the SnO2 / SnS2 / carbon cloth absorbing material sample had the largest effective bandwidth and the lowest maximum reflectivity. This indicates that the SnO2 / SnS2 / carbon cloth absorbing material sample has better electromagnetic wave absorption performance than the SnO2 / carbon cloth absorbing material and the SnS2 / carbon cloth composite absorbing material, proving that constructing a heterogeneous phase interface structure on the carbon cloth surface can effectively improve the electromagnetic wave absorption performance of the material.

[0103] Figure 7 The electromagnetic wave absorption performance of the ZnO / ZnS / carbon cloth absorbing material sample described in Example 4 is shown. When the matching thickness is 2.0 mm, the effective bandwidth is 1.1 GHz in the 2–18 GHz frequency band, and the maximum reflectivity is -29.8 dB.

[0104] Figure 8 The electromagnetic wave absorption performance of the NiO / NiS / carbon cloth absorbing material sample described in Example 5 is shown. When the matching thickness is 2.0 mm, the effective bandwidth is 3.1 GHz in the 2–18 GHz frequency band, and the maximum reflectivity is -32 dB.

[0105] The embodiments described above are merely illustrative of implementation methods of the present invention and should not be construed as limiting the scope of the present invention. It should be noted that all equivalent changes or modifications made in accordance with the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a transition metal oxide / transition metal sulfide / carbon cloth composite microwave absorbing material, characterized in that, Includes the following steps: (1) Add the sulfur-containing compound to the alcohol solution and stir until completely dissolved to obtain a mixed solution of the sulfur-containing compound; wherein the sulfur-containing compound is thiourea, thioacetamide or sodium sulfide; the alcohol solution is methanol, ethanol or isopropanol solution; the mass ratio of the sulfur-containing compound to the organic alcohol solution is 1:5-50. (2) The transition metal oxide / carbon cloth composite microwave absorbing material is placed in the above-mentioned mixed solution of sulfur-containing compounds and soaked to obtain a mixture of sulfur-containing compound solution and transition metal oxide / carbon cloth composite microwave absorbing material; (3) The mixture of sulfur-containing compound solution and transition metal oxide / carbon cloth composite microwave absorbing material is transferred to a hydrothermal reactor for heat treatment. The content of transition metal sulfides in the reaction product is controlled by adjusting the temperature and time of the heat treatment. After the reaction is completed, the reactor is cooled to room temperature, the carbon cloth is removed, washed and dried to obtain the transition metal oxide / transition metal sulfide / carbon cloth composite microwave absorbing material; wherein the heat treatment temperature is 100-240°C. o C, the heat preservation time is 2-24 hours; The aforementioned transition metal oxide / carbon cloth composite microwave absorbing material is prepared by the following method: S1. Add the metal salt and sodium citrate to a mixed solvent of ethanol and water, and then stir until completely dissolved to obtain a mixed solution; wherein the metal salt is one or more transition metal anions; the molar ratio of the metal salt to sodium citrate is 1:0.1-5, the volume ratio of ethanol to water in the mixture of ethanol and water is 1:0.1-10, and the mass ratio of the mixed solvent to the mixed solution is 1:5-50; S2. The hydrophilic carbon cloth is placed in a nitric acid solution, ultrasonically treated, then removed, washed, and dried to obtain the acid-treated hydrophilic carbon cloth. S3. The acid-treated hydrophilic carbon cloth is placed in the mixed solution obtained in step S1, and the hydrophilic carbon cloth is completely wetted to obtain a mixture of solution and carbon cloth. S4. Transfer the mixture of solution and carbon cloth to a hydrothermal reactor and maintain the temperature. After the reaction is complete, cool the reactor to room temperature, remove the carbon cloth, wash and dry it to obtain a transition metal oxide / carbon cloth composite microwave absorbing material; wherein the maintaining temperature is 110-180°C. o C, the heat preservation time is 2-24 hours.

2. The preparation method according to claim 1, characterized in that: In step S2, the mass ratio of the hydrophilic carbon cloth to the nitric acid solution is 1:50-300, and the concentration of the nitric acid solution is 5-40 wt%.

3. The preparation method according to claim 1, characterized in that: In step S3, the impregnation is performed by placing the mixture of solution and carbon cloth in a vacuum chamber for vacuum treatment.

4. The preparation method according to claim 1, characterized in that: In step S4, the transition metal oxide includes transition metal oxides of various valence states of Fe, Co, Ni, Cu, Zn, or Sn.

5. The preparation method according to claim 1, characterized in that: In step (3), the transition metal sulfide includes transition metal sulfides of various valence states of Fe, Co, Ni, Cu, Zn or Sn.

6. A transition metal oxide / transition metal sulfide / carbon cloth composite microwave absorbing material prepared by the preparation method according to any one of claims 1-5.

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