Lightweight and high-efficiency wave-absorbing material based on water-absorbing resin and preparation method thereof

Abstract

The application discloses a kind of light, efficient wave-absorbing material based on water-absorbing resin and preparation method, it is related to C-X waveband wave-absorbing material technical field.The preparation method includes the following steps: step S1, preparation concentration is 2-6g / L of cobalt salt aqueous solution, water-absorbing resin is soaked in the cobalt salt aqueous solution until the color of solution becomes colorless, obtain Co@resin composite material;Wherein, the mass ratio of water-absorbing resin and cobalt salt is (4-6):(1-3);Step S2, Co@resin composite material is pyrolyzed, then natural cooling, obtain Co / C composite material.The Co / C composite wave-absorbing material obtained by the method of the application has the advantages of strong electromagnetic wave attenuation ability, and also has the characteristics of light weight and stability.

Description

Technical Field

[0001] This invention belongs to the field of CX band absorbing materials technology, and particularly relates to a lightweight, high-efficiency absorbing material based on water-absorbing resin and its preparation method. Background Technology

[0002] Radar-absorbing materials have wide applications in military stealth technology, electromagnetic compatibility of electronic equipment, radiation protection for wireless communication base stations, and electromagnetic shielding of buildings. For example, radar-absorbing materials can effectively absorb radar waves, helping military equipment such as aircraft and ships reduce radar reflection signals and improve stealth performance; radar-absorbing materials can be used for electromagnetic shielding of electronic equipment to reduce mutual interference between devices and ensure normal operation; wireless communication base stations and antenna systems require radar-absorbing materials to reduce the reflection and scattering of electromagnetic waves and improve communication quality; radar-absorbing materials can be used in building materials to reduce the potential harm of electromagnetic waves to the human body.

[0003] As the requirements for lightweight equipment increase, absorbing materials also need to be lightweight to reduce their impact on the overall weight of the equipment. At the same time, absorbing materials need to have high absorption efficiency and be able to effectively absorb electromagnetic waves over a wide frequency band. In addition, absorbing materials should be easy to process into various shapes and sizes and be mass-produced to adapt to different application scenarios. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a lightweight and efficient microwave absorbing material based on water-absorbing resin and its preparation method. Using water-absorbing resin as a precursor, a Co@organic resin composite material is obtained by absorbing a certain amount of cobalt salt aqueous solution. The Co@organic resin composite material is then pyrolyzed at a certain temperature to obtain a Co / C composite microwave absorbing material. The Co / C composite microwave absorbing material obtained by the method of this invention has the advantage of strong electromagnetic wave attenuation capability, while also possessing lightweight and stable characteristics.

[0005] The first aspect of this invention discloses a method for preparing a lightweight, high-efficiency microwave absorbing material based on water-absorbing resin, comprising the following steps:

[0006] Step S1: Prepare a cobalt salt aqueous solution with a concentration of 2-6 g / L, and immerse the water-absorbing resin in the cobalt salt aqueous solution until the solution becomes colorless to obtain the Co@ resin composite material;

[0007] The mass ratio of the water-absorbing resin to the cobalt salt is (4-6):(1-3);

[0008] Step S2: The Co@ resin composite material is pyrolyzed and then cooled naturally to obtain the Co / C composite material.

[0009] According to the method for preparing a lightweight and efficient microwave absorbing material based on a water-absorbing resin according to the first aspect of the present invention, in step S1, the water-absorbing resin is a polyacrylate-polyacrylamide copolymer.

[0010] According to the method for preparing a lightweight and efficient microwave absorbing material based on a water-absorbing resin according to the first aspect of the present invention, in step S1, the cobalt salt is one or more of cobalt chloride, cobalt nitrate, cobalt acetate, and cobalt sulfate.

[0011] According to the method for preparing a lightweight, high-efficiency microwave absorbing material based on a water-absorbing resin according to the first aspect of the present invention, the cobalt salt is cobalt chloride.

[0012] According to the method for preparing a lightweight and efficient microwave absorbing material based on water-absorbing resin according to the first aspect of the present invention, in step S1, the time for static soaking is 24-48 hours.

[0013] According to the method for preparing a lightweight and efficient microwave absorbing material based on water-absorbing resin according to the first aspect of the present invention, in step S2, the heating rate during pyrolysis is 9-11℃ / min, the target temperature is 400-800℃, and the holding time is 28-32min.

[0014] According to the method for preparing a lightweight, high-efficiency microwave absorbing material based on a water-absorbing resin according to the first aspect of the present invention, in step S2, the pyrolysis is carried out in an air atmosphere.

[0015] According to the method for preparing a lightweight and efficient microwave absorbing material based on water-absorbing resin according to the first aspect of the present invention, in step S2, a tube furnace is used to pyrolyze the Co@ resin composite material.

[0016] According to the method for preparing a lightweight and efficient microwave absorbing material based on water-absorbing resin according to the first aspect of the present invention, in step S2, the Co@ resin composite material is crushed and then pyrolyzed.

[0017] The second aspect of this invention discloses a microwave absorbing material prepared by the aforementioned method for preparing a lightweight and efficient microwave absorbing material based on water-absorbing resin.

[0018] The solution proposed in this invention has the following technical effects:

[0019] This invention uses water-absorbing resin as a precursor to obtain Co@organic resin composite material by absorbing a certain amount of cobalt salt aqueous solution. Then, the Co@organic resin composite material is pyrolyzed to obtain Co / C composite microwave absorbing material. The Co / C composite microwave absorbing material obtained by the method of this invention has the advantages of strong electromagnetic wave attenuation ability, and also has the characteristics of being lightweight and stable.

[0020] Furthermore, the Co / C composite material prepared by this invention has strong plasticity, and its phase composition and material structure can be reasonably controlled at the microscopic level by controlling the pyrolysis temperature and the concentration of cobalt salt, thereby controlling the microwave absorption frequency band of the Co / C composite material.

[0021] Furthermore, the preparation process of the microwave absorbing material of this invention is green and environmentally friendly, and absorption can be carried out in an aqueous environment, which can also fully recover residual Co ions; the heating environment requirements are low, and it can be carried out in an air atmosphere, without the need for extremely high temperature treatment, resulting in low cost and suitability for large-scale mass production.

[0022] Furthermore, the absorbing material of this invention is in powder form, which can be added to a suitable medium and evenly coated on the surface of equipment. It is not limited by the shape of the equipment and is easy to carry with the equipment in spare quantity. It can provide electromagnetic protection and reinforcement to the equipment at any time, and can better meet the needs of military applications that are in harsh environments with rapid changes in temperature and humidity for a long time. Attached Figure Description

[0023] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0024] Figure 1 This is a flowchart illustrating a method for preparing a lightweight, high-efficiency microwave absorbing material based on water-absorbing resin according to an embodiment of the present invention.

[0025] Figure 2 Transmission electron microscope (TEM) images of the Co / C composite material prepared using 0.2g CoCl2 crystals as reactants in Example 1 of this invention, taken at scales of 500nm (a), 200nm (b), and 100nm (c).

[0026] Figure 3 Transmission electron microscope (TEM) images of the Co / C composite material prepared using 0.2 g CoCl2 crystals as reactants in Example 2 of this invention, taken at scales of 100 nm (a), 50 nm (b), and 20 nm (c).

[0027] Figure 4 Transmission electron microscope (TEM) images of the Co / C composite material prepared using 0.2 g CoCl2 crystals as reactants in Example 3 of this invention, at scales of 100 nm (a), 50 nm (b), and 20 nm (c).

[0028] Figure 5The XRD patterns are of the Co / C composite materials prepared using 0.2 g of CoCl2 crystals as reactants in Examples 1(a), 2(b), and 3(c) of the present invention.

[0029] Figure 6 The reflection loss diagrams are for the Co / C composite materials prepared using 0g (a), 0.1g (b), 0.2g (c), and 0.3g (d) CoCl2 crystals as reactants in Example 1 of the present invention.

[0030] Figure 7 The reflection loss diagrams are shown for the Co / C composite materials prepared using 0g (a), 0.1g (b), 0.2g (c), and 0.3g (d) CoCl2 crystals as reactants in Example 2 of this invention.

[0031] Figure 8 The reflection loss diagrams are for the Co / C composite materials prepared using 0g (a), 0.1g (b), 0.2g (c), and 0.3g (d) CoCl2 crystals as reactants in Example 3 of the present invention.

[0032] Figure 9 The diagram shows the reflection loss of the composite materials prepared in Comparative Examples 1, 2 and 3. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] The first aspect of this embodiment discloses a method for preparing a lightweight, high-efficiency microwave absorbing material based on water-absorbing resin, such as... Figure 1 As shown, it includes the following steps:

[0035] Step S1: Prepare a cobalt salt aqueous solution with a concentration of 2-6 g / L, and immerse the water-absorbing resin in the cobalt salt aqueous solution until the solution becomes colorless to obtain the Co@ resin composite material.

[0036] Step S2: The Co@ resin composite material is pyrolyzed and then cooled naturally to obtain the Co / C composite material.

[0037] In this invention, water-absorbing resin is used as a precursor, Co 2+Co@organic resin composite material is formed by combining with water-absorbing resin through resin adsorption, and then Co / C composite microwave absorbing material is obtained by pyrolysis of Co@organic resin composite material.

[0038] Meanwhile, the Co / C composite material prepared by this invention has strong plasticity. Its phase composition and material structure can be reasonably controlled at the microscopic level by controlling the pyrolysis temperature and the concentration of cobalt salt, which further improves the impedance matching and attenuation coefficient of the Co / C composite material, thereby reducing the reflection of electromagnetic waves by the Co / C composite material, making it easier for more electromagnetic waves to enter the internal loss of the Co / C composite material, and achieving the ideal effect of strong absorption, weak reflection, low density and wide bandwidth.

[0039] In step S1, a cobalt salt aqueous solution with a concentration of 2-6 g / L is prepared, and the water-absorbing resin is immersed in the cobalt salt aqueous solution until the solution becomes colorless, thus obtaining the Co@ resin composite material.

[0040] In some embodiments, the mass ratio of the water-absorbing resin to the cobalt salt is (4-6):(1-3).

[0041] If the concentration of the cobalt salt aqueous solution is less than 2 g / L, the Co that is adsorbed into the water-absorbing resin will be lost. 2+ Too little cobalt will not provide sufficient magnetic loss for the absorbent material. Furthermore, soaking the water-absorbing resin in a cobalt salt aqueous solution with a concentration higher than 6 g / L will damage its water absorption capacity due to the acidity or alkalinity of the solution, preventing the resin from absorbing water and growing. This will significantly reduce the resin's ability to absorb Co… 2+ The adsorption capacity. Furthermore, a mass ratio of water-absorbing resin to cobalt salt of (4-6):(1-3) can better achieve Co… 2+ Chemical adsorption between the absorbent resin and the absorbent polymer.

[0042] Specifically, the concentration of the cobalt salt aqueous solution can be 2 g / L, 3 g / L, 4 g / L, 5 g / L, or 6 g / L. Preferably, the concentration of the cobalt salt aqueous solution is 3-5 g / L. More preferably, the concentration of the cobalt salt aqueous solution is 4 g / L.

[0043] Specifically, the mass ratio of the water-absorbing resin to the cobalt salt can be 4:(1-3), 5:(1-3), or 6:(1-3). Preferably, the mass ratio of the water-absorbing resin to the cobalt salt is 5:2.

[0044] In some embodiments, in step S1, the water-absorbing resin is a polyacrylate-polyacrylamide copolymer.

[0045] In some embodiments, in step S1, the cobalt salt is one or more of cobalt chloride, cobalt nitrate, cobalt acetate, and cobalt sulfate.

[0046] In some embodiments, the cobalt salt is cobalt chloride.

[0047] In some embodiments, in step S1, the soaking time is 24-48 hours.

[0048] Specifically, the soaking time can be 24h, 26h, 28h, 30h, 32h, 34h, 36h, 38h, 40h, 42h, 44h, 46h, or 48h. Preferably, the soaking time is 24-40h. More preferably, the soaking time is 24-30h.

[0049] In step S2, the Co@ resin composite material is pyrolyzed and then cooled naturally to obtain the Co / C composite material.

[0050] In some embodiments, in step S2, the heating rate during pyrolysis is 9-11℃ / min, the target temperature is 400-800℃, and the holding time is 28-32min.

[0051] The target pyrolysis temperature of this invention is 400-800℃. If the temperature is too low, the water-absorbing resin cannot be completely decomposed into carbon, and the obtained material has no microwave absorption performance; if the temperature is too high, the material will carbonize into CO2 or CO in the air, and very little microwave absorbing material will be obtained. Similarly, if the holding time is too short, the material will not react completely, and if it is too long, the material will vaporize severely, leaving little material.

[0052] Specifically, the heating rate during pyrolysis can be 9°C / min, 10°C / min, or 11°C / min. Preferably, the heating rate during pyrolysis is 10°C / min.

[0053] Specifically, the target temperature during pyrolysis can be 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, or 800℃. Preferably, the target temperature during pyrolysis is 600-800℃. More preferably, the target temperature during pyrolysis is 650-750℃.

[0054] Specifically, the holding time during pyrolysis can be 28 min, 29 min, 30 min, 31 min, or 32 min. Preferably, the holding time during pyrolysis is 30 min.

[0055] In some embodiments, in step S2, the pyrolysis is carried out in an air atmosphere.

[0056] In some embodiments, in step S2, the Co@ resin composite material is pyrolyzed using a tube furnace.

[0057] In some embodiments, in step S2, the Co@ resin composite material is crushed and then pyrolyzed.

[0058] The second aspect of this embodiment discloses a microwave absorbing material prepared by the aforementioned method for preparing a lightweight and efficient microwave absorbing material based on water-absorbing resin.

[0059] Example 1

[0060] (1) Add 0.1g CoCl2, 0.2g CoCl2 and 0.3g CoCl2 to 50ml of deionized water and stir thoroughly to obtain three cobalt salt aqueous solutions of different concentrations.

[0061] (2) Weigh four portions of 0.4-0.6g of polyacrylate-polyacrylamide copolymer and add them to the above three different concentrations of cobalt salt aqueous solution and 50ml of deionized water without cobalt salt. Let them stand and soak for 24h to obtain four Co@ resin composite materials containing different amounts of cobalt ions.

[0062] (3) The four Co@ resin composite materials containing different amounts of cobalt ions were crushed and placed in a ceramic boat. The ceramic boat containing the Co@ resin composite material was then placed in a tube furnace for pyrolysis. The heating rate was set to 10℃ / min. After heating to 400℃ in an air atmosphere, the temperature was held for 30min, followed by natural cooling to obtain four Co / C composite materials, numbered as: Example 1-Co0, Example 1-Co 0.1 Example 1-Co 0.2 Example 1-Co 0.3 .

[0063] Example 2

[0064] The difference from Example 1 is that the target temperature for pyrolysis is 600°C.

[0065] Example 3

[0066] The difference from Example 1 is that the target temperature for pyrolysis is 800°C.

[0067] Comparative Example 1

[0068] (1) Add 0.2g AlCl3 to 50ml of deionized water and stir thoroughly to obtain an aluminum salt aqueous solution.

[0069] (2) Weigh 0.4-0.6g of polyacrylate-polyacrylamide copolymer and add it to aluminum salt aqueous solution. Let it stand for 24h to obtain Al@ resin composite material.

[0070] (3) The Al@ resin composite material was crushed and placed in a ceramic boat. Then, the ceramic boat containing the Al@ resin composite material was placed in a tube furnace for pyrolysis. The heating rate was set to 10℃ / min. After heating to 600℃ in an air atmosphere, the temperature was held for 30min, and then cooled naturally to obtain the product labeled Comparative Example 1-Al. 0.2 Al / C composite material.

[0071] Comparative Example 2

[0072] The difference from Comparative Example 1 is that the metal salt is ZnCl2, resulting in Comparative Example 2-Zn. 0.2 Zn / C composite material.

[0073] Comparative Example 3

[0074] The difference from Comparative Example 1 is that the metal salt is NiCl2, resulting in Comparative Example 3-Ni. 0.2 Ni / C composite material.

[0075] Figure 2 Transmission electron microscopy (TEM) images of the Co / C composite material prepared using 0.2 g CoCl2 crystals as reactants in Example 1 of this invention, taken at scales of 500 nm (a), 200 nm (b), and 100 nm (c). Figure 2 It can be seen that at a pyrolysis temperature of 400℃, the particle size of Co-containing nanocrystals is generally between 150-200nm, and they are loaded on the carbon layer.

[0076] Figure 3 Transmission electron microscopy (TEM) images of the Co / C composite material prepared using 0.2 g CoCl2 crystals as reactants in Example 2 of this invention, at scales of 100 nm (a), 50 nm (b), and 20 nm (c). Figure 3 It can be seen that at a pyrolysis temperature of 600℃, the particle size of Co-containing nanocrystals is significantly reduced to between 50-100 nm; as the particle size decreases, the distribution of Co-containing nanocrystals also tends to be more uniform, and at the same time, the thickness of the carbon layer supporting the Co-containing nanocrystals becomes significantly thinner.

[0077] Figure 4 Transmission electron microscopy (TEM) images of the Co / C composite material prepared using 0.2 g CoCl2 crystals as reactants in Example 3 of this invention, at scales of 100 nm (a), 50 nm (b), and 20 nm (c). Figure 4 It can be seen that at a pyrolysis temperature of 800℃, extremely fine Co-containing nanocrystals uniformly loaded on a thin layer of carbon were generated, with a particle size between 1 and 5 nm.

[0078] At 400℃, the upper limit of the high temperature is not very high. Therefore, during the pyrolysis of Co@resin composites, the nucleation rate of Co nanocrystals is not high. During pyrolysis, under conditions with fewer crystal nuclei, Co... 2+ Co nanocrystals participate in crystal growth, resulting in larger Co nanocrystal sizes. Furthermore, as the heat treatment temperature increases to 600℃ and 800℃, the undercooling during pyrolysis is enhanced, thus increasing the nucleation rate of Co-containing nanocrystals. With more Co-containing nuclei, the amount of Co participating in crystal growth increases. 2+ The number of nanocrystals is relatively smaller, thus resulting in a smaller nanocrystal size. Smaller Co nanocrystals can achieve more abundant Co / C interfaces, thereby improving the dielectric loss capability and microwave absorption performance of the material.

[0079] Figure 5 The XRD patterns are of the Co / C composite materials prepared using 0.2 g of CoCl2 crystals as reactants in Examples 1(a), 2(b), and 3(c) of this invention. Figure 5It can be seen that the peaks at 2θ angles of 19.000°, 31.271°, 36.845°, 38.423°, 44.808°, 55.655°, 59.353°, 65.231°, 77.338° and 78.403° of the Co / C composite material obtained in Example 1 are mainly present in magnetic Co3O4. The peaks with 2θ angles of 19.000°, 31.271°, 36.845°, 44.808°, 55.655°, 65.231°, 74.117°, 77.338°, and 78.403° of the Co / C composite material obtained in Example 2 are attributed to Co3O4 (standard PDF card number 43-1003); the peaks with 2θ angles of 16.131° and 32.411° are attributed to CoC8 (standard PDF card number 51-0625); and the peaks with 2θ angles of 38.183°, 41.451°, 46.711°, and 59.236° are attributed to Co3C (standard PDF card number 51-0625). In Example 3, the peaks with 2θ angles of 19.000°, 31.271°, 36.845°, 44.808°, 55.655°, 65.231°, 74.117°, 77.338°, and 78.403° in the Co / C composite material belong to Co3O4 (standard PDF card number 43-1003); the peaks with 2θ angles of 16.131° and 32.411° belong to CoC8 (standard PDF card number 51-0625); and the peaks with 2θ angles of 38.183°, 41.451°, 46.711°, and 59.236° belong to Co3C (standard PDF card number 51-0625). Therefore, Co is present in Co3O4, CoC8, and Co3C simultaneously in the Co / C composite materials obtained in Examples 2 and 3.

[0080] Figure 6 This is a reflection loss diagram of the Co / C composite material prepared according to Example 1 of the present invention using 0g (a), 0.1g (b), 0.2g (c), and 0.3g (d) CoCl2 crystals as reactants. The frequency range with a reflection loss less than -10dB is generally referred to as the effective absorption bandwidth. From... Figure 6 It can be seen that at a pyrolysis temperature of 400℃, the undoped Co composite material with a thickness of less than 1.85 mm cannot achieve effective electromagnetic loss. However, with increasing thickness, it can effectively absorb electromagnetic waves within a relatively small bandwidth. Example 1-Co 0.1The effective bandwidth and peak reflection loss of the sample were significantly improved compared to pure carbon materials. It exhibited strong electromagnetic wave attenuation capabilities across all thickness ranges greater than 1.75 mm in the 11.5-13, 13.5-14, 15-16, and 17.5-18 GHz frequency bands. Notably, the reflection loss at a thickness of 2.25 mm reached a peak of -40.81 dB at 12 GHz, almost completely attenuating electromagnetic waves. However, with increasing Co concentration, Example 1-Co... 0.2 and Example 1-Co 0.3 The electromagnetic wave attenuation performance of the sample decreased significantly, and the effective absorption bandwidth was narrow. This indicates that at a pyrolysis temperature of 400℃, the addition of a small amount of Co can significantly improve the electromagnetic wave attenuation performance. However, as the amount of Co increases, it has a negative effect on the performance, even resulting in a performance lower than that of the Co0 sample in Example 1.

[0081] Figure 7 This is a reflection loss diagram of the Co / C composite material prepared according to Example 2 of the present invention using 0g (a), 0.1g (b), 0.2g (c), and 0.3g (d) CoCl2 crystals as reactants. From... Figure 7 It can be seen that at a pyrolysis temperature of 600℃, Example 2-CoO and Example 2-Co 0.1 The samples almost all lacked effective absorption bandwidth and exhibited poor electromagnetic wave attenuation performance, indicating that at this temperature, the addition of a small amount of Co could not effectively improve the electromagnetic wave attenuation capability of the Co / C composite material. However, with the increase of Co, the reflection loss capability was significantly improved. (Example 2 - Co) 0.2 The sample exhibited an effective absorption bandwidth of 4.5 GHz within a thickness range of 1.75-2.45 mm; notably, at a thickness of 2.15 mm, the effective absorption bandwidth reached 6 GHz, and the peak reflection loss at 13.28 GHz reached -44.85 dB. Example 2-Co 0.3 The sample also exhibits excellent absorption performance in the high-frequency range, effectively absorbing electromagnetic waves in the 14.5GHz-18GHz range. Within a thickness range of 1.85-2.45mm, the effective absorption bandwidth reaches over 4.5GHz; notably, the 2.35mm thick sample achieves an effective bandwidth of 6.6GHz. At a frequency of 16.16GHz, the 1.95mm thick sample achieves a minimum reflection loss of -42.65dB.

[0082] Figure 7 and Figure 6 The comparison shows that the samples at 600℃ and 400℃ pyrolysis temperatures have a large difference in reflection loss performance, indicating that temperature has a significant impact on the electromagnetic wave absorption capacity of the prepared Co / C composite material.

[0083] Figure 8This is a reflection loss diagram of the Co / C composite material prepared according to Example 3 of the present invention using 0g (a), 0.1g (b), 0.2g (c), and 0.3g (d) CoCl2 crystals as reactants. From... Figure 8 It can be seen that at a pyrolysis temperature of 800℃, the CoO sample of Example 3, with a thickness of 2.25 mm or more, achieves a relatively wide effective absorption bandwidth of approximately 4 GHz in the high-frequency region (13-18 GHz). The addition of Co significantly improves electromagnetic wave absorption performance. 0.1 In the mid-to-high frequency (8-16 GHz) region, the sample exhibits an effective absorption bandwidth of approximately 4 GHz within a thickness range of 1.75 mm to 2.45 mm. With increasing thickness, thicknesses above 2.25 mm show good absorption performance in the 6-7 GHz range, while a thickness of 2.35 mm results in a reflection loss of -37.65 dB at 12 GHz. Example 3-Co 0.2 The absorption performance of the sample shifts to lower frequencies. When the thickness ranges from 1.75mm to 2.05mm, the absorption frequency band is concentrated in the X-band. At a thickness of 2.05-2.45mm, the electromagnetic wave attenuation capability becomes prominent in the 6-7.5GHz range. At a thickness of 2.45mm, the reflection loss reaches -28.21dB at 6.5GHz. Example 3-Co 0.3 The sample's absorption capability is mainly reflected in the X-band range, but the effective absorption bandwidth is relatively narrow, basically around 1.2-1.5 GHz.

[0084] Compared to Example 1, Examples 2 and 3 yielded a richer variety of Co compounds, with finer nanocrystals. The abundant Co compounds effectively enhance the magnetic loss capability of the material, while the rich Co / C interfaces effectively modulate the electromagnetic parameters of the Co / C composite material, thereby achieving efficient wave absorption in specific frequency bands. A comparison of the reflection loss diagrams also shows that compared to Example 1-Co… 0.2 Sample, Example 2-Co 0.2 Sample and Example 3-Co 0.2 The sample exhibits stronger reflection loss and an adjustable absorption frequency band.

[0085] Figure 9 The diagram shows the reflection loss of the composite materials prepared in Comparative Examples 1, 2, and 3. Figure 9As can be seen, compared to Example 2, the reflection loss performance of the Co-containing composite material is far superior to that of the Al, Zn, or Ni-containing composite materials of the same thickness. This is because Co is a magnetic metal, capable of simultaneously achieving electrical and magnetic losses in electromagnetic wave loss; while Al and Zn in the comparative examples are not magnetic metals, so electromagnetic wave loss is mainly achieved through electrical losses, with limited loss mechanisms. Although Ni is a magnetic metal, the pH of its salt solution does not match the pH required for adsorption by the absorbent resin. Therefore, compared to Co salt, Ni salt cannot be effectively adsorbed, resulting in insufficient wave absorption capability of its derived composite material.

[0086] Example 4

[0087] The difference from Example 2 is that the heating rate during pyrolysis is 9°C / min, and the holding time is 28min.

[0088] Example 5

[0089] The difference from Example 2 is that the heating rate during pyrolysis is 11°C / min, and the holding time is 29 min.

[0090] Example 6

[0091] The difference from Example 2 is that the holding time during pyrolysis is 31 minutes.

[0092] Example 7

[0093] The difference from Example 2 is that the holding time during pyrolysis is 32 minutes.

[0094] In summary, the solution proposed in this invention has the following technical effects:

[0095] This invention uses water-absorbing resin as a precursor to obtain Co@organic resin composite material by absorbing a certain amount of cobalt salt aqueous solution. Then, the Co@organic resin composite material is pyrolyzed to obtain Co / C composite microwave absorbing material. The Co / C composite microwave absorbing material obtained by the method of this invention has the advantages of strong electromagnetic wave attenuation ability, and also has the characteristics of being lightweight and stable.

[0096] Furthermore, the Co / C composite material prepared by this invention has strong plasticity, and its phase composition and material structure can be reasonably controlled at the microscopic level by controlling the pyrolysis temperature and the concentration of cobalt salt, thereby controlling the microwave absorption frequency band of the Co / C composite material.

[0097] Furthermore, the preparation process of the microwave absorbing material of this invention is green and environmentally friendly, and absorption can be carried out in an aqueous environment, which can also fully recover residual Co ions; the heating environment requirements are low, and it can be carried out in an air atmosphere, without the need for extremely high temperature treatment, resulting in low cost and suitability for large-scale mass production.

[0098] Furthermore, the absorbing material of this invention is in powder form, which can be added to a suitable medium and evenly coated on the surface of equipment. It is not limited by the shape of the equipment and is easy to carry with the equipment in spare quantity. It can provide electromagnetic protection and reinforcement to the equipment at any time, and can better meet the needs of military applications that are in harsh environments with rapid changes in temperature and humidity for a long time.

[0099] Please note that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. The above embodiments only illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for preparing a lightweight, high-efficiency wave-absorbing material based on a water-absorbing resin, characterized by, Includes the following steps: Step S1: Prepare a cobalt salt aqueous solution with a concentration of 2-6 g / L, and immerse the water-absorbing resin in the cobalt salt aqueous solution until the solution becomes colorless to obtain the Co@ resin composite material; The mass ratio of the water-absorbing resin to the cobalt salt is (4-6):(1-3); the water-absorbing resin is a polyacrylate-polyacrylamide copolymer. Step S2: Pyrolyze the Co@ resin composite material in air atmosphere, and then allow it to cool naturally to obtain the Co / C composite material; The heating rate during pyrolysis is 9-11℃ / min, the target temperature is 400-600℃, and the holding time is 28-32min.

2. The method for producing a lightweight, high-efficiency wave-absorbing material based on a water-absorbing resin according to claim 1, characterized by, In step S1, the cobalt salt is one or more of cobalt chloride, cobalt nitrate, cobalt acetate, and cobalt sulfate.

3. The method for producing a lightweight, high-efficiency wave-absorbing material based on a water-absorbing resin according to claim 2, characterized by, The cobalt salt is cobalt chloride.

4. The method for preparing a lightweight, high-efficiency microwave absorbing material based on water-absorbing resin according to claim 1, characterized in that, In step S1, the soaking time is 24-48 hours.

5. The method for preparing a lightweight, high-efficiency microwave absorbing material based on water-absorbing resin according to claim 1, characterized in that, In step S2, the Co@ resin composite material is pyrolyzed using a tube furnace.

6. The method for preparing a lightweight, high-efficiency microwave absorbing material based on water-absorbing resin according to claim 1, characterized in that, In step S2, the Co@ resin composite material is crushed and then pyrolyzed.

7. A microwave absorbing material prepared by the method for preparing a lightweight and efficient microwave absorbing material based on a water-absorbing resin according to any one of claims 1-6.

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