Multi-element copper-based metal sulfide composite material based on secondary vulcanization as well as preparation method and application of multi-element copper-based metal sulfide composite material

Abstract

The invention belongs to the technical field of electromagnetic wave absorbing materials, and discloses a multi-element copper-based metal sulfide composite material based on secondary vulcanization and a preparation method and application thereof.The method comprises the steps that a copper-based metal salt solution is prepared and subjected to heat treatment, and a product obtained after primary vulcanization is obtained; cleaning a product after the first vulcanization, drying to obtain copper sulfide, finally adding sulfur powder into the copper sulfide, grinding and mixing, and performing heat treatment again to finish the second vulcanization to obtain the multi-element copper-based metal sulfide. The microstructure of the multi-element copper-based metal sulfide composite material is of an irregular blocky structure and is used for absorbing electromagnetic waves; the composition comprises the following components in molar mass ratio: (2-3): (0-2): 2 of copper sulfide, cuprous sulfide and copper pentasulfide. The composite material has excellent wave absorbing performance in the X-Ku wave band (2-18 GHz), the preparation process is simple and controllable, the composite material is environment-friendly and high in repeatability, only conventional equipment is needed, and the composite material has outstanding industrial application potential.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic wave absorbing materials technology, specifically relating to a multi-component copper-based metal sulfide composite material based on secondary sulfidation, its preparation method, and its application. Background Technology

[0002] With the advent of 5G / 6G communication, the era of big data, and the rapid development of electromagnetic technology, intelligent electromagnetic devices and electronic communication devices (such as metamaterial mechanical antennas, multi-band wireless communication, and underwater optical communication) are constantly changing people's lives. However, the electromagnetic radiation pollution problem (residual electromagnetic waves, EMWs) generated by these devices cannot be ignored. High-frequency electromagnetic waves not only seriously interfere with the normal operation of precision instruments and equipment and damage the environment, but also threaten human health, inducing serious diseases including cancer. One of the most effective ways to solve electromagnetic pollution is to absorb unwanted EMWs and convert electromagnetic energy into heat energy or other forms of energy. In order to cope with the upcoming intelligent era and the increasingly complex electromagnetic environment (including the complex radar electromagnetic environment in the military field), the design and development of high-performance electromagnetic wave absorbing materials (absorbing materials) has important social value and military significance. An ideal absorbing material should meet the requirements of "thin, wide, strong, and light," that is, thin thickness, wide absorption bandwidth, strong absorption intensity, and light weight, to adapt to different application scenarios, especially key military requirements such as radar stealth of next-generation fighter jets.

[0003] Transition metal sulfides (TMDs) have shown application potential in electromagnetic pollution control and radar stealth due to their low cost, simple preparation, suitable electromagnetic parameters, and excellent physicochemical properties. However, pure TMDs have drawbacks such as a single electromagnetic loss mechanism, relatively high density, and easy agglomeration, making it difficult to simultaneously achieve good impedance matching and strong electromagnetic attenuation capabilities, and making it difficult to obtain broadband absorption characteristics at a small thickness.

[0004] Patent application CN120208304A discloses a layered cobalt aluminum oxide / copper sulfide microwave absorbing material and its preparation method. However, due to the poor conductivity, poor impedance matching, and narrow effective absorption bandwidth of single-component materials (layered cobalt aluminum oxide and copper sulfide), it has the disadvantages of weak microwave absorption performance, narrow effective bandwidth, and inability to meet the needs of practical applications. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention aims to provide a multi-component copper-based metal sulfide composite material based on secondary sulfidation, its preparation method, and its application. The method uses metal salts, thiourea, and sulfur powder as raw materials, combined with a subsequent secondary sulfidation process, to prepare the multi-component copper-based metal sulfide composite material, avoiding the limitations of complex preparation processes in traditional methods. Furthermore, on the one hand, secondary sulfidation can significantly reduce electromagnetic parameters, flexibly change its composition, and further enhance the material's electromagnetic loss capability through morphological characteristics. The design of an irregular blocky microstructure formed by secondary sulfidation and the multi-component metal sulfide synthesis strategy solve the problems of high density and easy particle agglomeration of metal sulfide materials. On the other hand, the secondary sulfidation strategy increases the impedance matching of the composite material while solving the problem of excessively high electromagnetic parameters of metal sulfides.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A multi-component copper-based metal sulfide composite material based on secondary sulfidation, comprising the following components in a molar mass ratio of (2-3):(0-2):2: copper sulfide (CuS), cuprous sulfide (CuS), and copper sulfide (CuS). 1.96 Copper pentasulfide (Cu9S5) and copper pentasulfide (Cu9S5).

[0008] The microstructure of the composite material is an irregular blocky structure.

[0009] A method for preparing a multi-component copper-based metal sulfide composite material based on secondary sulfidation includes the following steps:

[0010] Step 1: After cooling the heat-treated copper-based metal salt solution, filter it to obtain the product after the first sulfidation. Wash it with a mixed solution of deionized water and ethanol to remove unreacted sulfur or metal salts. Then, vacuum dry it to obtain copper sulfide (CuS).

[0011] Step 2: Mix copper sulfide (CuS) with sulfur powder at a molar mass ratio of 1:(0.1~1) and grind evenly to obtain a mixture of copper sulfide (CuS) and sulfur.

[0012] Step 3: The mixture obtained from grinding in step 2 is heated to 550-575℃ under vacuum and inert atmosphere at a heating rate of 1-10℃ / min and held for 1-3 hours to complete the second sulfidation, resulting in a multi-element copper-based metal sulfide with an irregular blocky microstructure.

[0013] The preparation method of the heat-treated copper-based metal salt solution in step 1 is as follows: copper nitrate trihydrate, thiourea and deionized water are mixed in a molar mass ratio of (0.8-1.2):(1.8-2.2):(6-10) and magnetically stirred until completely dissolved to prepare a copper-based metal salt solution. The copper-based metal salt solution is then heat-treated in an autoclave at 100-150°C for 15-24 hours.

[0014] In step 1, the molar mass ratio of the deionized water and ethanol mixed solution is (1-3):(1-3).

[0015] In step 1, the vacuum environment pressure for vacuum drying is -0.08 to -0.1 MPa, the drying temperature is 60 to 80°C, and the drying time is 6 to 8 hours.

[0016] A multi-component copper-based metal sulfide composite material based on secondary sulfidation is used to absorb electromagnetic waves.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] 1. This invention precisely optimizes electromagnetic performance through temperature control: By introducing a secondary sulfidation process (controllable temperature range of 550-575℃), under the protection of an inert atmosphere, sulfur powder is used to reconstruct the crystal structure of CuS synthesized by solvent heat treatment (water bath method) (converting it from nanoflowers to irregular blocks). The reconstructed metal sulfide material has a low crystal structure density and the particles are not easy to agglomerate, thus improving the wave absorption effect. Experiments show that 565℃ is the critical point for performance optimization. At this temperature, the material forms high-defect sulfur vacancies and heterogeneous interfaces, which significantly enhances interface polarization and conductivity loss, thereby achieving a synergistic improvement in electromagnetic wave attenuation capability and impedance matching.

[0019] 2. Compared with existing single-stage vulcanization methods, this invention adds two components, Cu. 1.96 S and Cu9S5, with Cu9S5 being a highly promising "high-loss" functional component, but the release of its absorption potential is highly dependent on composite material design and structural control to address its core impedance matching weakness. Cu... 1.96 The core advantage of CuS as an absorbing material lies in its abundant vacancy defects, which simultaneously drive two key dielectric loss mechanisms: polarization relaxation loss and conductivity loss. By combining CuS with these defects, its impedance matching characteristics are significantly optimized, synergistically enhancing multiple loss mechanisms, ultimately achieving strong and wideband absorption of electromagnetic waves with a thinner thickness and lighter weight.

[0020] 3. The process of this invention is simple and environmentally friendly: Compared with traditional multi-step composite processes (such as carbon-based loading requiring pre-synthesis and high-temperature carbonization), the preparation method of this invention only requires one step of secondary sulfidation in a tube furnace. An inert atmosphere is introduced, eliminating the need for strong acid / oxidant treatment and producing no toxic byproducts; the reaction system is closed and controllable, and the process has strong repeatability.

[0021] 4. This invention significantly improves the absorption bandwidth and intensity: the lattice distortion and sulfur vacancy defects induced by secondary sulfidation enable the material to exhibit a synergistic effect of multiple loss mechanisms in the X-Ku band (2-18GHz). Experiments have confirmed that the secondary sulfidation sample at 565℃, with a thickness of 1.77mm, achieves an effective absorption bandwidth (RL≤-10dB) of 4.6GHz, far exceeding the performance of the primary sulfidation product.

[0022] 5. The invention has outstanding potential for industrial application: the high-pressure autoclave and vacuum tube furnace used in the preparation process are both conventional equipment, and there is no complicated post-processing throughout the process, which has the stability for large-scale production.

[0023] In summary, this invention utilizes a precise temperature-controlled secondary sulfidation method (optimal 565℃) to reconstruct the crystal structure of CuS synthesized by solvothermal synthesis in one step (from nanoflowers to irregular blocks). The reconstructed metal sulfide material has a low crystal density and is less prone to particle agglomeration, while synergistically introducing Cu... 1.96 S and Cu9S5 functional components. This strategy significantly optimizes the impedance matching of the material and synergistically enhances the multiple loss mechanisms induced by interfacial polarization, conductivity loss, and sulfur vacancy defects. The results show that it achieves excellent microwave absorption performance in the X–Ku band (2–18 GHz) (effective absorption bandwidth of 4.6 GHz with a thickness of 1.77 mm), far exceeding that of the initial material. This process is simple and controllable (nitrogen protection, closed system), environmentally friendly, highly reproducible, and requires only conventional equipment, possessing outstanding potential for industrial application and providing a new approach for developing high-efficiency, lightweight microwave absorbing materials. Attached Figure Description

[0024] Figure 1(a) is a dielectric constant diagram of the multi-component copper-based metal sulfide composite material prepared in this invention.

[0025] Figure 1(b) is the X-ray diffraction pattern of the multi-component copper-based metal sulfide composite material prepared in this invention.

[0026] Figure 2(a) shows the S2p XPS spectrum of the multi-component copper-based metal sulfide composite material prepared in this invention.

[0027] Figure 2(b) shows the Cu 2p spectrum of the multi-component copper-based metal sulfide composite material prepared in this invention.

[0028] Figure 3 This is a scanning electron microscope image of CuS prepared in Comparative Example 1 of this invention.

[0029] Figure 4 This is a waveform absorption performance diagram of CuS prepared in Comparative Example 1 of this invention.

[0030] Figure 5 This is a waveform absorption performance diagram of the multi-component copper-based metal sulfide composite material prepared in Comparative Example 2 of this invention.

[0031] Figure 6 This is a scanning electron microscope image of the multi-component copper-based metal sulfide composite material prepared in Comparative Example 3 of this invention.

[0032] Figure 7 This is a waveform absorption performance diagram of the multi-component copper-based metal sulfide composite material prepared in Comparative Example 3 of this invention.

[0033] Figure 8 This is a waveform absorption performance diagram of the multi-component copper-based metal sulfide composite material prepared in Comparative Example 4 of this invention.

[0034] Figure 9 This is a waveform absorption performance diagram of the multi-element copper-based metal sulfide composite material prepared in Example 1 of this invention.

[0035] Figure 10 This is a waveform absorption performance diagram of the multi-element copper-based metal sulfide composite material prepared in Example 2 of the present invention.

[0036] Figure 11 This is a scanning electron microscope image of the multi-component copper-based metal sulfide composite material prepared in Example 3 of the present invention.

[0037] Figure 12 This is a waveform absorption performance diagram of the multi-element copper-based metal sulfide composite material prepared in Example 3 of the present invention.

[0038] Figure 13 This is a waveform absorption performance diagram of the multi-element copper-based metal sulfide composite material prepared in Example 4 of the present invention.

[0039] Figure 14 This is a waveform absorption performance diagram of the multi-element copper-based metal sulfide composite material prepared in Example 5 of the present invention.

[0040] Figure 15 This is a scanning electron microscope image of the multi-component copper-based metal sulfide composite material prepared in Comparative Example 5 of this invention.

[0041] Figure 16 This is a waveform absorption performance diagram of the multi-component copper-based metal sulfide composite material prepared in Comparative Example 5 of this invention. Detailed Implementation

[0042] The present invention will now be described in detail with reference to the accompanying drawings.

[0043] The following are specific implementation examples of the present invention. Note that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0044] A multi-component copper-based metal sulfide composite material based on secondary sulfidation, comprising the following components in a molar mass ratio of (2-3):(0-2):2: copper sulfide (CuS), cuprous sulfide (CuS), and copper sulfide (CuS). 1.96 Copper pentasulfide (Cu9S5) and copper pentasulfide (Cu9S5).

[0045] The microstructure of the composite material is an irregular blocky structure.

[0046] A method for preparing a multi-component copper-based metal sulfide composite material based on secondary sulfidation includes the following steps:

[0047] Step 1: After cooling the heat-treated copper-based metal salt solution, filter it to obtain the product after the first sulfidation. Wash it with a mixed solution of deionized water and ethanol to remove unreacted sulfur or metal salts. Then, vacuum dry it to obtain copper sulfide (CuS).

[0048] Step 2: Mix copper sulfide (CuS) with sulfur powder at a molar mass ratio of 1:(0.1~1) and grind evenly to obtain a mixture of copper sulfide (CuS) and sulfur.

[0049] Step 3: The mixture obtained from grinding in step 2 is heated to 550-575℃ under vacuum and inert atmosphere at a heating rate of 1-10℃ / min and held for 1-3 hours to complete the second sulfidation, resulting in a multi-element copper-based metal sulfide with an irregular blocky microstructure.

[0050] The preparation method of the heat-treated copper-based metal salt solution in step 1 is as follows: copper nitrate trihydrate, thiourea and deionized water are mixed in a molar mass ratio of (0.8-1.2):(1.8-2.2):(6-10) and magnetically stirred until completely dissolved to prepare a copper-based metal salt solution. The copper-based metal salt solution is then heat-treated in an autoclave at 100-150°C for 15-24 hours.

[0051] In step 1, the molar mass ratio of the deionized water and ethanol mixed solution is (1-3):(1-3).

[0052] In step 1, the vacuum drying environment pressure is -0.08 to -0.1 MPa, the drying temperature is 60 to 80°C, and the drying time is 6 to 8 hours.

[0053] A multi-component copper-based metal sulfide composite material based on secondary sulfidation is used to absorb electromagnetic waves.

[0054] Comparative Example 1

[0055] Step 1: Mix copper nitrate trihydrate, thiourea and deionized water in a molar mass ratio of 1:2:8 and stir magnetically for 20 minutes to prepare a copper-based metal salt solution;

[0056] Step 2: Transfer the copper-based metal salt solution to a 100ml PTFE-lined stainless steel autoclave, and then perform solvothermal treatment at 100℃ for 20h.

[0057] Step 3: After cooling the solution after heat treatment in Step 2, wash it three times with a mixture of deionized water and ethanol in a molar mass ratio of 3:2 to remove unreacted sulfur or metal salts, and collect the product.

[0058] Step 4: The product was vacuum dried at a pressure of -0.08 MPa and a temperature of 75°C for 7 hours to obtain copper sulfide (CuS).

[0059] Figure 1(a) shows the dielectric constant of the copper sulfide (CuS) prepared in Comparative Example 1 of this invention. Its real and imaginary dielectric constants are high, resulting in poor matching. Figure 1(b) shows the X-ray diffraction pattern of the copper sulfide (CuS) prepared in Comparative Example 1 of this invention. The main peak is that of copper sulfide (CuS), with a good peak shape, indicating good crystallinity. Figure 2(a) is the S spectrum, and Figure 2(b) is the Cu spectrum. Figure 3 Scanning electron microscope image of copper sulfide (CuS) prepared in Comparative Example 1, from Figure 3 The copper sulfide (CuS) appears to be in a nano-flower shape. A schematic diagram of the microwave absorption properties of the copper sulfide (CuS) prepared in Comparative Example 1 of this invention is shown below. Figure 4 It is evident that the absorption performance of the comparative example of this invention is poor and still needs further improvement.

[0060] Comparative Example 2

[0061] The microstructure of a multi-component copper-based metal sulfide composite material based on secondary sulfidation is an irregular blocky structure.

[0062] The composite material comprises the following components in a 2:2 molar mass ratio: copper sulfide (CuS) and copper pentasulfide (Cu9S5).

[0063] A method for preparing a multi-component copper-based metal sulfide composite material based on secondary sulfidation includes the following steps:

[0064] Step 1: Mix copper nitrate trihydrate, thiourea and deionized water in a molar mass ratio of 1:2:8 and stir magnetically until completely dissolved to prepare a copper-based metal salt solution. Transfer the copper-based metal salt solution to a 100ml PTFE-lined stainless steel autoclave and then perform solvothermal treatment at 180℃ for 20h.

[0065] Step 2: After cooling the copper-based metal salt solution after heat treatment in Step 1, filter it to obtain the product after the first sulfidation. Then wash it three times with a mixed solution of deionized water and ethanol with a molar mass ratio of 2:3 to remove unreacted sulfur or metal salts, and collect the product.

[0066] Step 3: The product collected in Step 2 was vacuum dried for 7 hours in a vacuum environment with a pressure of -0.08 MPa and a temperature of 75°C to obtain CuS.

[0067] Step 4: Place CuS and sulfur powder in an agate mortar with a molar mass ratio of 1:1 and grind until fully mixed;

[0068] Step 5: Using a vacuum tube furnace, the mixture ground in step 4 is heated to 450°C under a nitrogen atmosphere at a heating rate of 5°C / min for pyrolysis treatment and held at that temperature for 2 hours to complete the second sulfidation and obtain a multi-element copper-based metal sulfide.

[0069] A schematic diagram of the microwave absorption performance of copper sulfide (CuS) prepared in Comparative Example 2 of this invention is shown below. Figure 5 It can be seen that increasing the amount of sulfur powder added in this invention has no significant effect.

[0070] Comparative Example 3

[0071] The microstructure of a multi-component copper-based metal sulfide composite material based on secondary sulfidation is an irregular blocky structure.

[0072] The composite material comprises the following components in a 2:2 molar mass ratio: copper sulfide (CuS) and copper pentasulfide (Cu9S5).

[0073] A method for preparing a multi-component copper-based metal sulfide composite material based on secondary sulfidation includes the following steps:

[0074] Step 1: Mix copper nitrate trihydrate, thiourea and deionized water in a molar mass ratio of 1:2:8 and stir magnetically until completely dissolved to prepare a copper-based metal salt solution. Transfer the copper-based metal salt solution to a 100ml PTFE-lined stainless steel autoclave and then perform solvothermal treatment at 140℃ for 20h.

[0075] Step 2: After cooling the copper-based metal salt solution after heat treatment in Step 1, filter it to obtain the product after the first sulfidation. Then wash it three times with a mixed solution of deionized water and ethanol with a molar mass ratio of 2:3 to remove unreacted sulfur or metal salts, and collect the product.

[0076] Step 3: The product collected in Step 2 was vacuum dried for 7 hours in a vacuum environment with a pressure of -0.08 MPa and a temperature of 75°C to obtain CuS.

[0077] Step 4: Place CuS and sulfur powder in an agate mortar with a molar mass ratio of 1:0.5 and grind until fully mixed;

[0078] Step 5: Using a vacuum tube furnace, the mixture ground in step 4 is heated to 450°C under a nitrogen atmosphere at a heating rate of 5°C / min for pyrolysis treatment and held at that temperature for 2 hours to complete the second sulfidation and obtain a multi-element copper-based metal sulfide.

[0079] Figure 1(a) shows the dielectric constant diagram of Comparative Example 3 of the present invention. The real and imaginary parts of the dielectric constant are slightly lower than those of Comparative Example 1, but the matching degree is still relatively high. Figure 1(b) shows the X-ray diffraction pattern of the copper sulfide (CuS) prepared in Comparative Example 3 of the present invention at a pyrolysis temperature of 450℃ during secondary sulfidation. Compared with the copper sulfide (CuS) prepared in Comparative Example 1 of the present invention, in addition to the peaks of copper sulfide (CuS), a large number of peaks of copper sulfide (Cu9S5) also appear. Figure 6 The scanning electron microscope image prepared for Comparative Example 3 is from... Figure 6 As can be seen from the microstructure of Comparative Example 3, it exhibits an irregular blocky structure. A schematic diagram of the microwave absorption performance of the copper sulfide (CuS) prepared in Comparative Example 3 of this invention is shown below. Figure 7 It can be seen that the absorption performance is not significantly improved when the pyrolysis treatment is carried out at 450℃. Figure 2(a) shows the S spectrum prepared in Comparative Example 3, which is right-biased compared with Comparative Example 1. Figure 2(b) shows the Cu spectrum prepared in Comparative Example 3, which is left-biased compared with Comparative Example 1. This indicates that charge transfer can be achieved at 450℃ compared with Comparative Example 1.

[0080] Comparative Example 4

[0081] The microstructure of a multi-component copper-based metal sulfide composite material based on secondary sulfidation is an irregular blocky structure.

[0082] The composite material comprises the following components in a 2:2 molar mass ratio: copper sulfide (CuS) and copper pentasulfide (Cu9S5).

[0083] A method for preparing a multi-component copper-based metal sulfide composite material based on secondary sulfidation includes the following steps:

[0084] Step 1: Mix copper nitrate trihydrate, thiourea and deionized water in a molar mass ratio of 1:2:8 and stir magnetically until completely dissolved to prepare a copper-based metal salt solution. Transfer the copper-based metal salt solution to a 100ml PTFE-lined stainless steel autoclave and then perform solvothermal treatment at 140℃ for 20h.

[0085] Step 2: After cooling the copper-based metal salt solution after heat treatment in Step 1, filter it to obtain the product after the first sulfidation. Then wash it three times with a mixed solution of deionized water and ethanol with a molar mass ratio of 2:3 to remove unreacted sulfur or metal salts, and collect the product.

[0086] Step 3: The product collected in Step 2 was vacuum dried for 7 hours in a vacuum environment with a pressure of -0.05 MPa and a temperature of 75°C to obtain CuS.

[0087] Step 4: Place CuS and sulfur powder in an agate mortar with a molar mass ratio of 1:0.1 and grind until fully mixed;

[0088] Step 5: Using a vacuum tube furnace, the mixture ground in step 4 is heated to 450°C under a nitrogen atmosphere at a heating rate of 5°C / min for pyrolysis treatment and held at that temperature for 2 hours to complete the second sulfidation and obtain a multi-element copper-based metal sulfide.

[0089] A schematic diagram of the microwave absorption properties of the multi-component copper-based metal sulfide prepared in Comparative Example 4 of this invention is shown below. Figure 8 It can be seen that the microwave absorption performance of the present invention is the same as that of the aforementioned Comparative Examples 2 and 3, and its electromagnetic parameters are also similar, indicating that its vulcanization is not related to the amount of sulfur powder added, but only to the temperature during secondary vulcanization.

[0090] Example 1

[0091] A multi-component copper-based metal sulfide composite material based on secondary sulfidation has an irregular blocky structure in its microstructure and is used to absorb electromagnetic waves.

[0092] The composite material comprises the following components in a 2:2 molar mass ratio: copper sulfide (CuS) and copper pentasulfide (Cu9S5).

[0093] A method for preparing a multi-component copper-based metal sulfide composite material based on secondary sulfidation includes the following steps:

[0094] Step 1: Mix copper nitrate trihydrate, thiourea and deionized water in a molar mass ratio of 0.8:1.8:6 and stir magnetically until completely dissolved to prepare a copper-based metal salt solution. Transfer the copper-based metal salt solution to a 100ml PTFE-lined stainless steel autoclave and then perform solvothermal treatment at 100℃ for 15h.

[0095] Step 2: After cooling the copper-based metal salt solution after heat treatment in Step 1, filter it to obtain the product after the first sulfidation. Then wash it twice with a mixed solution of deionized water and ethanol with a molar mass ratio of 2:1 to remove unreacted sulfur or metal salts, and collect the product.

[0096] Step 3: The product collected in Step 2 was vacuum dried at a pressure of -0.1 MPa and a temperature of 75°C for 6 hours to obtain CuS.

[0097] Step 4: Add CuS at a molar mass ratio of 1:0.1 to sulfur powder and place it in an agate mortar, then grind until fully mixed.

[0098] Step 5: Using a vacuum tube furnace, the mixture ground in step 4 is heated to 550°C at a heating rate of 1°C / min under a nitrogen atmosphere for pyrolysis treatment and held at that temperature for 1 hour to complete the second sulfidation and obtain a multi-element copper-based metal sulfide.

[0099] A schematic diagram of the microwave absorption properties of the multi-component copper-based metal sulfide prepared in Example 1 of this invention is shown below. Figure 9 With an absorption bandwidth of 1.45 GHz, it can be seen that the absorption performance of the present invention is improved compared with that of the aforementioned comparative examples 1 to 4.

[0100] Example 2

[0101] A multi-component copper-based metal sulfide composite material based on secondary sulfidation has an irregular blocky structure in its microstructure and is used to absorb electromagnetic waves.

[0102] The composite material comprises the following components in a 2:2 molar mass ratio: copper sulfide (CuS) and copper pentasulfide (Cu9S5).

[0103] A method for preparing a multi-component copper-based metal sulfide composite material based on secondary sulfidation includes the following steps:

[0104] Step 1: Mix copper nitrate trihydrate, thiourea and deionized water in a molar mass ratio of 1:2:8 and stir magnetically until completely dissolved to prepare a copper-based metal salt solution. Transfer the copper-based metal salt solution to a 100ml PTFE-lined stainless steel autoclave and then perform solvothermal treatment at 140℃ for 20h.

[0105] Step 2: After cooling the copper-based metal salt solution after heat treatment in Step 1, filter it to obtain the product after the first sulfidation. Then wash it three times with a mixed solution of deionized water and ethanol with a molar mass ratio of 2:3 to remove unreacted sulfur or metal salts, and collect the product.

[0106] Step 3: The product collected in Step 2 was vacuum dried at a pressure of -0.08 MPa and a temperature of 60°C for 7 hours to obtain CuS.

[0107] Step 4: Place CuS and sulfur powder in an agate mortar with a molar mass ratio of 1:0.5 and grind until fully mixed;

[0108] Step 5: Using a vacuum tube furnace, the mixture ground in step 4 is heated to 550°C at a heating rate of 5°C / min under a nitrogen atmosphere for pyrolysis treatment and held at that temperature for 2 hours to complete the second sulfidation and obtain a multi-element copper-based metal sulfide.

[0109] Figure 1(a) shows the dielectric constant diagram of the sample prepared in Example 2 of this invention. The real and imaginary parts of the dielectric constant are significantly reduced compared to Comparative Examples 1 and 3. In Figure 1(b), S-550℃ represents the X-ray diffraction pattern of copper sulfide (CuS) prepared in Example 2 of this invention at a pyrolysis temperature of 550℃ during secondary sulfidation. Compared to the copper sulfide (CuS) prepared in Comparative Example 1 of this invention, in addition to the peaks of copper sulfide (CuS), a large number of peaks of copper sulfide (Cu9S5) also appear. A schematic diagram of the microwave absorption performance at S-550℃ prepared in Example 2 of this invention is shown below. Figure 10 The absorption bandwidth is 3.82 GHz, and its absorption performance is significantly improved compared to comparative examples 1-4 of this invention. This indicates that at 550°C, high-temperature sulfidation optimizes the sulfur vacancy concentration, synergistically enhancing dipole polarization and ion migration loss with copper vacancies, thereby improving the absorption performance.

[0110] Example 3

[0111] A multi-component copper-based metal sulfide composite material based on secondary sulfidation has an irregular blocky structure in its microstructure and is used to absorb electromagnetic waves.

[0112] The composite material comprises the following components in a molar mass ratio of 2:2:2: copper sulfide (CuS) and cuprous sulfide (CuS). 1.96 Copper pentasulfide (Cu9S5) and copper pentasulfide (Cu9S5).

[0113] Step 1: Mix copper nitrate trihydrate, thiourea and deionized water in a molar mass ratio of 1:2:10 and stir magnetically until completely dissolved to prepare a copper-based metal salt solution. Transfer the copper-based metal salt solution to a 100ml PTFE-lined stainless steel autoclave and then perform solvothermal treatment at 140℃ for 20h.

[0114] Step 2: After cooling the copper-based metal salt solution after heat treatment in Step 1, filter it to obtain the product after the first sulfidation. Then wash it three times with a mixed solution of deionized water and ethanol with a molar mass ratio of 1:2 to remove unreacted sulfur or metal salts, and collect the product.

[0115] Step 3: The product collected in Step 2 was vacuum dried at a pressure of -0.07 MPa and a temperature of 75°C for 7 hours to obtain CuS.

[0116] Step 4: Place CuS and sulfur powder in an agate mortar with a molar mass ratio of 1:0.5 and grind until fully mixed;

[0117] Step 5: Using a vacuum tube furnace, the mixture ground in step 4 is heated to 565°C at a heating rate of 5°C / min under a nitrogen atmosphere for pyrolysis treatment and held at that temperature for 2 hours to complete the second sulfidation and obtain a multi-element copper-based metal sulfide.

[0118] Figure 1(a) shows the dielectric constant diagram of the sample prepared in Example 3 of the present invention. The real and imaginary parts of the dielectric constant are further improved compared to Comparative Examples 1, 3, and 2. Figure 1(b) shows the X-ray diffraction pattern of the copper sulfide (CuS) prepared in Example 3 of the present invention at a pyrolysis temperature of 565℃ during secondary sulfidation. Compared to the copper sulfide (CuS) prepared in Comparative Examples 1-4 of the present invention, in addition to the peak of copper sulfide (CuS), a large amount of copper sulfide (Cu9S5, Cu...) also appears. 1.96 The peak of S). Figure 11 The scanning electron microscope image of copper sulfide S-565℃ prepared in Example 3 is shown below. Figure 11 As can be seen, the microstructure of S-565℃ is irregularly blocky. A schematic diagram of the microwave absorption performance of S-565℃ prepared in Example 3 of this invention is shown below. Figure 12 The absorption bandwidth is 4.60 GHz, and its absorption performance is significantly improved compared to Comparative Examples 1-4 and Example 1 of this invention, with electromagnetic parameters achieving a good match. This indicates that high-temperature sulfidation optimizes the sulfur vacancy concentration, synergistically enhancing dipole polarization and ion migration loss with copper vacancies. This is further corroborated by the XPS in Figure 2(b). Using CuS as the standard, they are all left-biased, with the largest bias at 565°C, indicating that 565°C can achieve stronger charge transfer capability and thus higher interfacial polarization loss compared to other times.

[0119] Example 4

[0120] A multi-component copper-based metal sulfide composite material based on secondary sulfidation has an irregular blocky structure in its microstructure and is used to absorb electromagnetic waves.

[0121] The composite material comprises the following components in a molar mass ratio of 2:1:2: copper sulfide (CuS), cuprous sulfide (CuS), and copper sulfide (CuS). 1.96 Copper pentasulfide (Cu9S5) and copper pentasulfide (Cu9S5).

[0122] A method for preparing a multi-component copper-based metal sulfide composite material based on secondary sulfidation includes the following steps:

[0123] Step 1: Mix copper nitrate trihydrate, thiourea and deionized water in a molar mass ratio of 1:2:8 and stir magnetically until completely dissolved to prepare a copper-based metal salt solution. Transfer the copper-based metal salt solution to a 100ml PTFE-lined stainless steel autoclave and then perform solvothermal treatment at 150℃ for 24h.

[0124] Step 2: After cooling the copper-based metal salt solution after heat treatment in Step 1, filter it to obtain the product after the first sulfidation. Then wash it three times with a mixed solution of deionized water and ethanol with a molar mass ratio of 2:3 to remove unreacted sulfur or metal salts, and collect the product.

[0125] Step 3: The product collected in Step 2 was vacuum dried at a pressure of -0.08 MPa and a temperature of 75°C for 7 hours to obtain CuS.

[0126] Step 4: Place CuS and sulfur powder in an agate mortar with a molar mass ratio of 1:0.5 and grind until fully mixed;

[0127] Step 5: Using a vacuum tube furnace, the mixture ground in step 4 is heated to 575°C under a nitrogen atmosphere at a heating rate of 5°C / min for pyrolysis treatment and held at that temperature for 2 hours to complete the second sulfidation and obtain a multi-element copper-based metal sulfide.

[0128] Figure 1(a) shows the dielectric constant diagram of the copper sulfide (CuS) prepared in Example 4 of this invention. In Figure 1(b), the X-ray diffraction pattern of the copper sulfide (CuS) prepared in Example 3 of this invention at a pyrolysis temperature of 575℃ during secondary sulfidation is shown. Compared with the copper sulfide (CuS) prepared in Comparative Examples 1-4 of this invention, in addition to the peak of copper sulfide (CuS), a large amount of copper sulfide (Cu9S5, Cu...) also appears. 1.96 The peak of S). A schematic diagram of the absorption performance at S-575℃ prepared in Example 4 of this invention is shown below. Figure 13 The absorption bandwidth is 3.50 GHz, and its absorption performance is significantly improved compared to Comparative Examples 1-4 of this invention. However, compared to Examples 1 and 2, the absorption performance is significantly reduced. This indicates that higher temperature is not necessarily better, possibly due to the disruption of copper vacancy order and the impedance mismatch caused by excessive sulfur vacancy generation.

[0129] Example 5

[0130] A multi-component copper-based metal sulfide composite material based on secondary sulfidation has an irregular blocky structure in its microstructure and is used to absorb electromagnetic waves.

[0131] The composite material comprises the following components in a molar mass ratio of 3:2:2: copper sulfide (CuS) and cuprous sulfide (CuS). 1.96Copper pentasulfide (Cu9S5) and copper pentasulfide (Cu9S5).

[0132] A method for preparing a multi-component copper-based metal sulfide composite material based on secondary sulfidation includes the following steps:

[0133] Step 1: Mix copper nitrate trihydrate, thiourea and deionized water in a molar mass ratio of 1.2:2.2:10 and stir magnetically until completely dissolved to prepare a copper-based metal salt solution. Transfer the copper-based metal salt solution to a 100ml PTFE-lined stainless steel autoclave and then perform solvothermal treatment at 150℃ for 24h.

[0134] Step 2: After cooling the copper-based metal salt solution after heat treatment in Step 1, filter it to obtain the product after the first sulfidation. Then wash it 5 times with a mixture of deionized water and ethanol with a molar mass ratio of 3:3 to remove unreacted sulfur or metal salts, and collect the product.

[0135] Step 3: The product collected in Step 2 was vacuum dried at a pressure of -0.1 MPa and a temperature of 80 °C for 8 hours to obtain CuS.

[0136] Step 4: Place CuS and sulfur powder in an agate mortar with a molar mass ratio of 1:1 and grind until fully mixed;

[0137] Step 5: Using a vacuum tube furnace, the mixture ground in step 4 is heated to 575°C at a heating rate of 10°C / min under a nitrogen atmosphere for pyrolysis treatment and held at that temperature for 3 hours to complete the second sulfidation and obtain a multi-element copper-based metal sulfide.

[0138] A schematic diagram of the microwave absorption properties of the multi-component copper-based metal sulfide prepared in Example 5 of this invention is shown below. Figure 14 As can be seen, compared with the absorption performance of the aforementioned comparative examples 1 to 4, the absorption bandwidth of the present invention is 2.60 GHz, and the absorption performance has been improved.

[0139] Comparative Example 5

[0140] The microstructure of a multi-component copper-based metal sulfide composite material based on secondary sulfidation is an irregular blocky structure.

[0141] The composite material comprises the following components in a 2:2 molar mass ratio: copper sulfide (CuS) and copper pentasulfide (Cu9S5).

[0142] A method for preparing a multi-component copper-based metal sulfide composite material based on secondary sulfidation includes the following steps:

[0143] Step 1: Mix copper nitrate trihydrate, thiourea and deionized water in a molar mass ratio of 1:2:8 and stir magnetically until completely dissolved to prepare a copper-based metal salt solution. Transfer the copper-based metal salt solution to a 100ml PTFE-lined stainless steel autoclave and then perform solvothermal treatment at 180℃ for 20h.

[0144] Step 2: After cooling the copper-based metal salt solution after heat treatment in Step 1, filter it to obtain the product after the first sulfidation. Then wash it three times with a mixed solution of deionized water and ethanol with a molar mass ratio of 2:3 to remove unreacted sulfur or metal salts, and collect the product.

[0145] Step 3: The product collected in Step 2 was vacuum dried for 7 hours in a vacuum environment with a pressure of -0.1 MPa and a temperature of 75°C to obtain CuS.

[0146] Step 4: Grind CuS and sulfur powder in a molar mass ratio of 1:0.5 until they are fully mixed.

[0147] Step 5: Using a vacuum tube furnace, the mixture ground in step 4 is heated to 450°C under a nitrogen atmosphere at a heating rate of 5°C / min for pyrolysis treatment and held at that temperature for 2 hours to complete the second sulfidation and obtain a multi-element copper-based metal sulfide.

[0148] Figure 1(a) shows the dielectric constant diagram of the copper sulfide (CuS) prepared in Comparative Example 5 of the present invention. Figure 1(b) shows the X-ray diffraction pattern of the copper sulfide (CuS) prepared in Comparative Example 5 of the present invention at a pyrolysis temperature of 600℃ during secondary sulfidation. Compared with the copper sulfide (CuS) prepared in Comparative Example 1 of the present invention, in addition to the peaks of copper sulfide (CuS), a large number of peaks of copper sulfide (Cu9S5) also appear. Figure 15 Scanning electron microscope image of copper sulfide prepared in Comparative Example 5, from Figure 15 As can be seen, the microstructure of Comparative Example 5 is irregular and blocky. A schematic diagram of the microwave absorption performance of Comparative Example 5 of this invention is shown below. Figure 16 The absorption performance was worse than that of Examples 1-3, and the electromagnetic parameters also dropped below 10. Figure 2(a) shows the S-spectrum prepared in Comparative Example 5. Compared with Comparative Example 1, Comparative Example 3 and Example 3, the S-spectrum shows the largest rightward shift. Figure 2(b) shows the Cu-spectrum prepared in Comparative Example 5. Compared with Comparative Example 1, Cu-spectrum shows a leftward shift. This indicates that higher temperature is not necessarily better. The reason may be the destruction of the copper vacancy order and the impedance mismatch caused by excessive sulfur vacancy generation.

[0149] Experimental verification

[0150] A coaxial ring sample (with an inner diameter of 3 mm and an outer diameter of 7 mm) with a thickness of 1.77 mm was prepared by doping paraffin with a 50% ratio of secondary sulfidation-based multi-copper-based metal sulfide. The electromagnetic parameters of the sample were measured using a vector network analyzer, and the microwave absorption performance of the material was calculated using CST STUDIO SUITE software.

[0151] According to the comparative examples and embodiments of the present invention, it can be seen that in the secondary sulfidation process, a vacuum tube furnace under a nitrogen atmosphere is heated to 565°C at a heating rate of 5°C / min for pyrolysis treatment and held at that temperature for 2 hours to obtain a pyrolyzed multi-element copper-based metal sulfide. Its microwave absorption performance, with a thickness of 1.77 mm, achieves an effective absorption bandwidth (RL≤-10dB) of 4.6 GHz. Compared to comparative examples 1-5 (absorption bandwidth 0 GHz) which have no effective microwave absorption capability, the present invention achieves a breakthrough from scratch, obtaining an absorption bandwidth as high as 4.6 GHz. Moreover, it significantly surpasses existing technologies (such as the 3.62 GHz reported in patent publication number CN120208304A), increasing the absorption bandwidth by 27.8% and significantly broadening the effective operating frequency band of the material.

Claims

1. A multi-component copper-based metal sulfide composite material based on secondary sulfidation, characterized in that, The following components, in a molar mass ratio of (2-3):(0-2):2, are: copper sulfide (CuS), cuprous sulfide (CuS), etc. 1.96 Copper pentasulfide (Cu9S5) and copper pentasulfide (Cu9S5).

2. The composite material according to claim 1, characterized in that, The microstructure of the composite material is an irregular blocky structure.

3. A method for preparing a multi-component copper-based metal sulfide composite material based on secondary sulfidation, characterized in that, Includes the following steps: Step 1: After cooling the heat-treated copper-based metal salt solution, filter it to obtain the product after the first sulfidation. Wash it with a mixed solution of deionized water and ethanol to remove unreacted sulfur or metal salts. Then, vacuum dry it to obtain copper sulfide (CuS). Step 2: Mix copper sulfide (CuS) with sulfur powder at a molar mass ratio of 1:(0.1~1) and grind evenly to obtain a mixture of copper sulfide (CuS) and sulfur. Step 3: The mixture obtained from grinding in step 2 is heated to 550-575℃ under vacuum and inert atmosphere at a heating rate of 1-10℃ / min and held for 1-3 hours to complete the second sulfidation, resulting in a multi-element copper-based metal sulfide with an irregular blocky microstructure.

4. The preparation method according to claim 3, characterized in that, The preparation method of the heat-treated copper-based metal salt solution in step 1 is as follows: copper nitrate trihydrate, thiourea and deionized water are mixed in a molar mass ratio of (0.8-1.2):(1.8-2.2):(6-10) and magnetically stirred until completely dissolved to prepare a copper-based metal salt solution. The copper-based metal salt solution is then heat-treated in an autoclave at 100-150°C for 15-24 hours.

5. The preparation method according to claim 3, characterized in that, In step 1, the molar mass ratio of the deionized water and ethanol mixed solution is (1-3):(1-3).

6. The preparation method according to claim 3, characterized in that, In step 1, the vacuum drying environment pressure is -0.08 to -0.1 MPa, the drying temperature is 60 to 80°C, and the drying time is 6 to 8 hours.

7. The preparation method according to any one of claims 3 to 6, characterized in that, Includes the following steps: Step 1: First, copper nitrate trihydrate, thiourea, and deionized water in a molar mass ratio of 1:2:10 are magnetically stirred until completely dissolved to prepare a copper-based metal salt solution. The solution is then subjected to solvothermal treatment at 140℃ for 20 hours. After cooling the heat-treated copper-based metal salt solution, it is filtered to obtain the product after the first sulfidation. The product is then washed with a mixture of deionized water and ethanol to remove unreacted sulfur or metal salts. Finally, it is vacuum dried at a pressure of -0.07 MPa and a temperature of 75℃ for 7 hours to obtain copper sulfide (CuS). Step 2: Mix copper sulfide (CuS) and sulfur powder at a molar mass ratio of 1:0.5 and grind them evenly; Step 3: The mixture obtained from grinding in Step 2 is heated to 565℃ under vacuum and inert atmosphere at a heating rate of 5℃ / min and held for 2 hours to complete the second sulfidation, resulting in a multi-element copper-based metal sulfide with an irregular blocky microstructure.

8. An application of a multi-component copper-based metal sulfide composite material based on secondary sulfidation, characterized in that, The composite material is used to absorb electromagnetic waves.

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