An absorbent for shielding materials of 5G base stations and its preparation method

Abstract

The present invention relates to the technical field of electromagnetic wave absorption materials, and particularly to a wave absorber applicable to shielding materials for 5G base stations and a preparation method thereof. The preparation method of the wave absorber comprises the following steps: mixing carbonyl iron powder with a dielectric material and then performing three-stage ball milling, and then performing annealing treatment to obtain the wave absorber; the three-stage ball milling specifically is: Stage 1: the ball-to-material ratio is 10:1, the rotation speed is 300-350 rpm, and the time is 2 h; Stage 2: the ball-to-material ratio is (20-25):1, the rotation speed is 600-700 rpm, and the time is 3.5-5 h; Stage 3: after adding an additive accounting for 1% of the total mass of the carbonyl iron powder and the dielectric material, perform ball milling in Stage 3, the ball-to-material ratio is 5:1, the rotation speed is 200-250 rpm, and the time is 1 h. The present invention adopts a multi-stage ball milling process to realize the morphology control of the wave absorber particles, thereby improving the wave absorption ability of the wave absorber in the P band below 1 GHz.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic wave absorbing materials, and particularly to a wave absorber applicable to 5G base station shielding materials and a preparation method thereof. Background Art

[0002] Carbonyl iron powder is one of the commonly used wave absorbing materials because of its high magnetic permeability and adjustable dielectric constant. However, the current commercially available carbonyl iron powder wave absorbers usually work in the frequency band of 1 GHz - 18 GHz. As can be seen from the current commonly used communication frequency bands, the low-frequency end has extended to 700 MHz. In order to expand the working frequency band of the wave absorbing material, the commonly used technical means is to compound carbonyl iron powder with other absorbers. For example, Chinese invention patent CN114899618B discloses a wave absorbing patch for 5G base stations at 700 MHz within the P band and a preparation method thereof, which is made of a ternary magnetic composite absorber and rubber; among them, the ternary magnetic composite absorber includes secondary sintered ferrite, flaky carbonyl iron, and flaky iron silicon aluminum; the secondary sintered ferrite includes iron oxide, zinc oxide, cobalt oxide, and barium carbonate; its preparation process is complex, which is not conducive to large-scale production, and at the same time, the thickness is relatively thick and the efficiency needs to be improved.

[0003] Therefore, it is of great significance to provide a wave absorber applicable to 5G base station shielding materials with a simple preparation process, simple composition, and wave absorbing ability in the P band below 1 GHz for the technical field of electromagnetic wave absorbing materials. Summary of the Invention

[0004] Based on the above, the present invention provides a wave absorber applicable to 5G base station shielding materials and a preparation method thereof. Using this wave absorber to prepare a wave absorbing material can achieve strong absorption of the electromagnetic radiation of 5G base stations around 700 MHz; the preparation method of the present invention is simple and environmentally friendly.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] One of the technical solutions of the present invention, a preparation method of a wave absorber applicable to 5G base station shielding materials, includes the following steps:

[0007] Mix carbonyl iron powder with a dielectric material and then perform three-stage ball milling, and then perform annealing treatment to obtain the wave absorber;

[0008] The specific three-stage ball milling is as follows:

[0009] Stage 1: The ball-to-material ratio is 10:1, the rotation speed is 300 - 350 rpm, and the time is 2 h;

[0010] Stage 2: The ball-to-material ratio is (20 - 25):1, the rotation speed is 600 - 700 rpm, and the time is 3.5 - 5 h;

[0011] Stage 3: After adding an additive accounting for 1% of the total mass of carbonyl iron powder and dielectric material, ball milling in Stage 3 is carried out with a ball-to-material ratio of 5:1, a rotation speed of 200 - 250 rpm, and a time of 1 h.

[0012] The second technical solution of the present invention is an absorbing agent prepared according to the above preparation method.

[0013] The third technical solution of the present invention is the application of the above absorbing agent in the preparation of 5G base station shielding materials.

[0014] The fourth technical solution of the present invention is a 5G base station shielding material, the raw materials of which include the above absorbing agent.

[0015] The fifth technical solution of the present invention is a preparation method of the above 5G base station shielding material. After mixing the absorbing agent with rubber, it is successively subjected to internal mixing, open mixing, sheet extrusion, and vulcanization to obtain the 5G base station shielding material.

[0016] The present invention discloses the following technical effects:

[0017] The present invention provides a method for preparing an absorbing agent suitable for 5G base station shielding materials by high-energy ball milling. By adopting a staged ball milling process, the morphology of the absorbing agent particles is regulated, thereby enhancing the absorbing ability of the absorbing agent in the P band below 1 GHz.

[0018] The magnetic permeability of the absorbing agent prepared by the method of the present invention is significantly improved in the low-frequency band below 1 GHz. The real part of the magnetic permeability > 7, and the imaginary part of the magnetic permeability > 2, which can be effectively used for electromagnetic shielding of 5G base stations. Description of the Drawings

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0020] Figure 1 It is the SEM image of the absorbing agent prepared in Comparative Example 1 of the present invention.

[0021] Figure 2 It is the SEM image of the absorbing agent prepared in Example 2 of the present invention.

[0022] Figure 3 It is the particle size distribution diagram of the absorbing agent prepared in Example 2 of the present invention. Detailed Embodiments

[0023] The various exemplary embodiments of the present invention will be described in detail below. This detailed description should not be construed as a limitation on the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0024] It should be understood that the terms used in the present invention are only for describing specific embodiments and are not intended to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0025] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0026] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the present invention specification, which are obvious to those skilled in the art. Other embodiments obtained from the specification of the present invention are obvious to those skilled in the art. The specification and embodiments of the present invention are merely exemplary.

[0027] Regarding the use of "comprising", "including", "having", "containing", etc. herein, they are all open-ended terms, meaning including but not limited to.

[0028] The "%" mentioned in the present invention, unless otherwise specified, all represent mass percentages.

[0029] The first aspect of the present invention provides a preparation method for an electromagnetic wave absorber applicable to 5G base station shielding materials, comprising the following steps:

[0030] Mix carbonyl iron powder with a dielectric material and then perform three-stage ball milling (argon or nitrogen is filled for protection during the ball milling process, and the gas flow rate is 0.5 - 1.5 L / min), and then perform annealing treatment to obtain the electromagnetic wave absorber;

[0031] The specific process of the three-stage ball milling is as follows:

[0032] Stage 1: The ball-to-material ratio is 10:1, the rotation speed is 300 - 350 rpm, and the time is 2 h. The main function of Stage 1 is to break large particles;

[0033] Stage 2: The ball-to-material ratio is (20 - 25):1, the rotation speed is 600 - 700 rpm, and the time is 3.5 - 5 h; the main function of Stage 2 is to form a flaky structure;

[0034] Stage 3: After adding an additive accounting for 1% of the total mass of carbonyl iron powder and dielectric material, ball milling in Stage 3 is carried out with a ball-to-material ratio of 5:1, a rotation speed of 200 - 250 rpm, and a time of 1 h; the main function of Stage 3 is to perform surface activation.

[0035] The present invention realizes the "crushing - flattening - surface activation" hierarchical treatment by regulating the rotation speed, ball-to-material ratio, and time of ball milling in stages, thereby achieving the wave absorption ability of the wave absorber for the P band (about 700 MHz) below 1 GHz.

[0036] In a preferred embodiment of the present invention, the mass ratio of the carbonyl iron powder to the dielectric material is (3 - 10):1, and more preferably (5 - 8):1; the dielectric material is carbon nanotubes.

[0037] In a preferred embodiment of the present invention, hard stainless steel grinding balls (hardness HRC 60) are used. In Stage 1, Φ8 mm grinding balls (70%) + Φ10 mm grinding balls (30%) are used; in both Stage 2 and Stage 3, Φ8 mm grinding balls (50%) + Φ5 mm grinding balls (50%) are used.

[0038] In a preferred embodiment of the present invention, the additive is stearic acid and / or silane coupling agent.

[0039] In a preferred embodiment of the present invention, the annealing treatment adopts overall annealing or segmented annealing; the specific overall annealing is: annealing at 200 - 400°C for 1 - 3 h under a protective atmosphere; the specific segmented annealing is: under a protective atmosphere, first keep warm at 200°C for 1 h, then heat up to 300°C at a rate of 1 hour, keep warm for 2 h, and then heat up to 400°C at a rate of 1 hour and keep warm for 1 h.

[0040] The protective atmosphere is argon, or an argon - hydrogen mixed atmosphere with a hydrogen content of 1 - 5 vol%.

[0041] The second aspect of the present invention provides a wave absorber prepared by the above - mentioned preparation method.

[0042] The third aspect of the present invention provides the application of the above - mentioned wave absorber in the preparation of 5G base station shielding materials.

[0043] The fourth aspect of the present invention provides a 5G base station shielding material, the raw materials of which include the above - mentioned wave absorber.

[0044] The fifth aspect of the present invention provides a method for preparing the above-mentioned shielding material for 5G base stations. After mixing the wave-absorbing agent with rubber, it is successively subjected to internal mixing, open mixing, sheet extrusion, and vulcanization to obtain the shielding material for 5G base stations.

[0045] The present invention does not make special limitations on the conditions of internal mixing, open mixing, sheet extrusion, and high-temperature flat vulcanization. The conditions of internal mixing, open mixing, sheet extrusion, and high-temperature flat vulcanization well-known to those skilled in the art can be adopted.

[0046] In a preferred embodiment of the present invention, the mass ratio of the wave-absorbing agent to the rubber is 73:27.

[0047] The wave-absorbing material prepared by using the wave-absorbing agent of the present invention can achieve strong absorption of electromagnetic radiation around 700 MHz and can be used as a shielding material for 5G base stations.

[0048] The technical solutions of the present invention are all conventional solutions in the art unless otherwise specified. The reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.

[0049] In the examples of the present invention, the carbonyl iron powder used is spherical, with a particle size of 1-5 microns, and is purchased from Jiangsu Tianyi Ultra-fine Metal Powder Co., Ltd.; the carbon nanotubes are purchased from Beijing Dekedaojin Technology Co., Ltd., with a tube diameter of 1-2 nm and a length of 5-30 microns.

[0050] In the examples of the present invention, the silane coupling agent used is the conventional model KH560 and is purchased from Nanjing Chengong Organosilicon Materials Co., Ltd.; the rubber used in the examples of the present invention is specifically methyl vinyl silicone rubber (PDMS is also applicable to the present invention).

[0051] The technical solutions provided by the present invention will be described in detail below in conjunction with the examples, but they should not be construed as limiting the protection scope of the present invention.

[0052] Example 1

[0053] Step 1: Mix carbonyl iron powder and carbon nanotubes according to a mass ratio of 6:1, and then perform three-stage ball milling (argon gas is filled for protection during the ball milling process, and the gas flow rate is 1.0 L / min):

[0054] Stage 1 (coarse grinding): The ball-to-material ratio is 10:1, the rotation speed is 300 rpm, and the time is 2 h;

[0055] Stage 2 (fine grinding): The ball-to-material ratio is 20:1, the rotation speed is 600 rpm, and the time is 4 h;

[0056] Stage 3 (Surface modification): Add stearic acid and silane coupling agent (mass ratio of stearic acid to silane coupling agent is 1:1) accounting for 1% of the total mass of carbonyl iron powder and carbon nanotubes. The ball-to-material ratio is 5:1, the rotation speed is 200 rpm, and the time is 1 h.

[0057] Use hard stainless steel grinding balls (hardness HRC 60), which can provide high impact energy and reduce pollution; in Stage 1, use Φ8 mm grinding balls (70%) + Φ10 mm grinding balls (30%); in both Stage 2 and Stage 3, use Φ8 mm grinding balls (50%) + Φ5 mm grinding balls (50%). Larger-sized grinding balls are selected in Stage 1 to increase the collision energy density; smaller-sized grinding balls are selected in the subsequent stages to increase the collision frequency and refine the surface structure.

[0058] Step 2, Annealing treatment: After ball milling, anneal at 300 °C for 2 h, and the protective atmosphere is argon containing 3 vol% hydrogen. The wave-absorbing agent is obtained after annealing.

[0059] The wave-absorbing agent prepared in this example has a high degree of integrity of the flaky structure and strong surface activity. The wave-absorbing agent and paraffin are melted into a ring-shaped test piece according to a mass ratio of 83:17. The real part of the magnetic permeability of the ring-shaped test piece is >7 and the imaginary part of the magnetic permeability is >2 in the low-frequency band below 1 GHz measured by a vector network analyzer and a coaxial air transmission line.

[0060] The wave-absorbing agent prepared in Example 1 and rubber are mixed according to a mass ratio of 73:27, and a flat wave-absorbing material is prepared through internal mixing, open mixing, sheet extrusion, and high-temperature flat vulcanization. Among them, the internal mixing time is 15 minutes, the open mixing time is 60 minutes, the vulcanization temperature is 150 °C, the vulcanization time is 15 minutes, and the specification size of the flat test sample is 800*800 mm and the thickness is 3.0 mm. The reflection loss of the prepared flat wave-absorbing material to 700 MHz electromagnetic waves is ≤ -10 dB.

[0061] Example 2

[0062] Step 1, Mix carbonyl iron powder and carbon nanotubes according to a mass ratio of 7:1, and then carry out three-stage ball milling (argon is filled for protection during ball milling, and the gas flow rate is 1.0 L / min):

[0063] Stage 1: The ball-to-material ratio is 10:1, the rotation speed is 350 rpm, and the time is 2 h;

[0064] Stage 2: The ball-to-material ratio is 25:1, the rotation speed is 650 rpm, and the time is 3.5 h;

[0065] Stage 3: Add stearic acid accounting for 1% of the total mass of carbonyl iron powder and carbon nanotubes, the ball-to-material ratio is 5:1, the rotation speed is 250 rpm, and the time is 1 h.

[0066] Hard stainless steel grinding balls (hardness HRC 60) are used. In stage 1, Φ8 mm grinding balls (70%) + Φ10 mm grinding balls (30%) are used; in stages 2 and 3, Φ8 mm grinding balls (50%) + Φ5 mm grinding balls (50%) are used.

[0067] Step 2, annealing treatment: After ball milling, annealing is carried out at 350 °C for 1.5 h, and the protective atmosphere is pure argon. After annealing, the wave-absorbing agent is obtained.

[0068] The SEM image of the wave-absorbing agent prepared in this example is as Figure 2 shown. It can be seen from Figure 2 that the flaky structure of the wave-absorbing agent is thinner and more evenly distributed, the proportion of flaky particles > 90%, and the thickness < 200 nm. The particle size distribution of the wave-absorbing agent prepared in this example is as Figure 3 shown. It can be seen from Figure 3 that D50 = 4.880 microns and D90 = 8.486 microns. Compared with the raw material carbonyl iron powder, the measured equivalent particle size has increased significantly, which is the result of ball milling and flakiness. The wave-absorbing agent and paraffin are melted into a ring-shaped test piece according to a mass ratio of 83:17. Using a vector network analyzer and a coaxial air transmission line, it is measured that the real part of the magnetic permeability of the ring-shaped test piece in the low-frequency band below 1 GHz > 7, and the imaginary part of the magnetic permeability > 2.

[0069] The wave-absorbing agent prepared in Example 2 is used to prepare a flat wave-absorbing material according to the same method as in Example 1. The results show that its wave-absorbing frequency band is broadened to 600 - 800 MHz, and the reflection loss of electromagnetic waves at 600 - 800 MHz ≤ -10 dB.

[0070] Example 3

[0071] The difference from Example 1 is only that in step 1, the mass ratio of carbonyl iron powder to carbon nanotubes is 8:1; in step 2, the annealing treatment adopts segmented annealing: first, keep it at 200 °C for 1 h, then heat it to 300 °C at a rate of 1 hour and keep it for 2 h, and then heat it to 400 °C at a rate of 1 hour and keep it for 1 h. The protective atmosphere is argon containing 2 vol% hydrogen; the remaining steps and parameters are the same as those in Example 1.

[0072] The wave-absorbing agent prepared in this example and paraffin are melted into a ring-shaped test piece according to a mass ratio of 83:17. Using a vector network analyzer and a coaxial air transmission line, it is measured that the real part of the magnetic permeability of the ring-shaped test piece in the low-frequency band below 1 GHz > 7, and the imaginary part of the magnetic permeability > 2. After annealing by the annealing method of Example 3, the crystallinity of the wave-absorbing agent is improved, and the thermal stability of the material is enhanced. It is confirmed by high and low temperature cycle tests (referring to the standard GB / T 2423.22 - 2012) that the electromagnetic shielding performance can be maintained at an ambient temperature of 200 °C.

[0073] Example 4

[0074] Step 1: Mix carbonyl iron powder and carbon nanotubes at a mass ratio of 5:1, and then perform three-stage ball milling (argon gas is filled for protection during ball milling, and the gas flow rate is 1.0 L / min):

[0075] Stage 1: The ball-to-material ratio is 10:1, the rotation speed is 300 rpm, and the time is 2 h;

[0076] Stage 2: The ball-to-material ratio is 20:1, the rotation speed is 700 rpm, and the time is 5 h;

[0077] Stage 3: Add stearic acid accounting for 1% of the total mass of carbonyl iron powder and carbon nanotubes. The ball-to-material ratio is 5:1, the rotation speed is 200 rpm, and the time is 1 h.

[0078] Use hard stainless steel grinding balls (hardness HRC 60). In stage 1, use Φ8 mm grinding balls (70%) + Φ10 mm grinding balls (30%); in stage 2 and stage 3, use Φ8 mm grinding balls (50%) + Φ5 mm grinding balls (50%).

[0079] Step 2: Annealing treatment: After ball milling, anneal at 400 °C for 1 h. The protective atmosphere is argon containing 4 vol% hydrogen. After annealing, the wave-absorbing agent is obtained.

[0080] The thickness of the flaky structure of the wave-absorbing agent prepared in this example is reduced to the nanometer level, and the thickness < 200 nm. The wave-absorbing agent and paraffin are melted and made into a ring-shaped test piece at a mass ratio of 83:17. Use a vector network analyzer and a coaxial air transmission line to measure that the real part of the magnetic permeability of the ring-shaped test piece is > 7 and the imaginary part of the magnetic permeability is > 2 in the low-frequency band below 1 GHz; in the frequency band of 1 - 3 GHz, the real part of the magnetic permeability is > 7 and the imaginary part of the magnetic permeability is > 2.5. Use the same method as in Example 1 to prepare the wave-absorbing agent of this example into a flat wave-absorbing material with a thickness of 3.0 mm, and its reflection loss for electromagnetic waves of 600 MHz - 3.2 GHz ≤ -10 dB.

[0081] Comparative Example 1

[0082] Step 1: Mix carbonyl iron powder and carbon nanotubes at a mass ratio of 6:1, and then perform two-stage ball milling (argon gas is filled for protection during ball milling, and the gas flow rate is 1.0 L / min):

[0083] Stage 1 (coarse grinding + surface modification): The ball-to-material ratio is 10:1. Add stearic acid and silane coupling agent accounting for 1% of the total mass of carbonyl iron powder and carbon nanotubes (the mass ratio of stearic acid to silane coupling agent is 1:1). The rotation speed is 300 rpm, and the time is 2 h;

[0084] Stage 2 (fine grinding): The ball-to-material ratio is 20:1, the rotation speed is 600 rpm, and the time is 4 h.

[0085] Hard stainless steel grinding balls (hardness HRC 60) were used. In stage 1, Φ8 mm grinding balls (70%) + Φ10 mm grinding balls (30%) were used; in stage 2, Φ8 mm grinding balls (50%) + Φ5 mm grinding balls (50%) were used.

[0086] Step 2, annealing treatment: after the ball milling is completed, annealing is performed at 300° C. for 2 h, the protective atmosphere is argon containing 3 vol% hydrogen, and the absorber is obtained after the annealing is completed.

[0087] The difference between this example and Example 1 is that the addition of the surface modifier in stage 3 of Example 1 is adjusted to stage 1 and the ball milling in stage 3 is omitted, and the steps are simplified compared with Example 1. The SEM image of the absorber obtained in this comparative example is as follows Figure 1 As shown. Figure 1 It can be seen that the integrity of the sheet structure is acceptable, but the size is uneven. The absorber and paraffin were melted in a mass ratio of 83:17 to make a ring test piece. The real part of the magnetic permeability of the ring test piece in the low frequency band below 1 GHz was measured using a vector network analyzer and a coaxial air transmission line. The imaginary part of the magnetic permeability is <7 and the imaginary part is <2.

[0088] Comparative Example 2

[0089] The only difference from Example 2 is that the addition of stearic acid in step 1 is omitted, and the remaining steps and parameters are the same as those in Example 2.

[0090] The absorber prepared in this comparative example was verified in the same way as in Example 2. The results showed that the particle size distribution became wider and the proportion of large-sized particles increased. The real part of the magnetic permeability of the annular test piece measured by a vector network analyzer and a coaxial air transmission line was <5 and the imaginary part of the magnetic permeability was <2 in the low-frequency band below 1 GHz.

[0091] Comparative Example 3

[0092] The only difference from Example 2 is that the timing of adding stearic acid in step 1 is adjusted from adding in stage 3 to adding stearic acid in stage 2; the remaining steps and parameters are the same as in Example 2.

[0093] The absorber prepared in this comparative example was verified in the same effect as in Example 2, and the results showed that the particle size became relatively smaller, and D50 changed to below 4 um, so that the real part of the magnetic permeability in the low frequency band below 1 GHz obtained by the test became smaller, and the performance in the high frequency band was improved.

[0094] Comparative Example 4

[0095] The difference from Example 2 is only that the three-stage ball milling in Step 2 is adjusted to two-stage ball milling, specifically: Stage 1: ball-to-material ratio of 10:1, rotation speed of 350 rpm, time of 2 h; Stage 2: adding stearic acid accounting for 1% of the total mass of carbonyl iron powder and carbon nanotubes, ball-to-material ratio of 25:1, rotation speed of 650 rpm, time of 4.5 h.

[0096] The same effect verification as in Example 2 was carried out on the absorbent prepared in this comparative example. The results show that: using a vector network analyzer and a coaxial air transmission line to measure the real part of the magnetic permeability of the annular test piece in the low-frequency band below 1 GHz < 6.5, and the imaginary part < 1.8.

[0097] Comparative Example 5

[0098] The difference from Example 2 is only that no protective gas (argon) was filled during the ball milling process in Stages 1 to 3, and the remaining steps and parameters are the same as those in Example 2.

[0099] The same effect verification as in Example 2 was carried out on the absorbent prepared in this comparative example. The results show that: the surface of the absorbent particles is severely oxidized, the real part of the magnetic permeability < 5, the imaginary part < 1.5, and the absorption frequency band is significantly narrowed.

[0100] Comparative Example 6

[0101] The difference from Example 2 is only that nitrogen protection (flow rate of 1.0 L / min) was used instead of argon protection during the ball milling in Stage 3, and the remaining parameters are the same as those in Example 2.

[0102] The same effect verification as in Example 2 was carried out on the absorbent prepared in this comparative example. The results show that: the real part of the magnetic permeability of the absorbent > 6.8, the imaginary part > 1.9, but the uniformity of the flaky structure is slightly lower than that in Example 2 (the proportion of flaky particles is about 85%).

[0103] The above-described embodiments are only descriptions of the preferred modes of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention should fall within the protection scope determined by the claims of the present invention.

Claims

1. An application of a wave absorbing agent in the preparation of 5G base station shielding materials, characterized in that: The preparation method of the wave absorbing agent comprises the following steps: The carbonyl iron powder is mixed with the dielectric material and subjected to three-stage ball milling, followed by annealing to obtain the absorbent; The three-stage ball milling is specifically as follows: Stage 1: ball-to-material ratio is 10:1, rotation speed is 300-350 rpm, and time is 2 h; Stage 2: ball-to-material ratio is (20-25):1, speed is 600-700 rpm, and time is 3.5-5 h; Stage 3: After adding additives accounting for 1% of the total mass of carbonyl iron powder and dielectric material, ball milling in stage 3 was carried out, with a ball-to-material ratio of 5:1, a rotation speed of 200-250 rpm, and a time of 1 h; The mass ratio of the carbonyl iron powder to the dielectric material is (3-10):1; the dielectric material is carbon nanotubes; The additive is stearic acid and / or a silane coupling agent; The annealing treatment adopts overall annealing or segmented annealing; the overall annealing is specifically: annealing at 200-400°C for 1-3 hours under a protective atmosphere; the segmented annealing is specifically: in a protective atmosphere, first keep the temperature at 200°C for 1 hour, then increase the temperature to 300°C in 1 hour and keep the temperature for 2 hours, and then increase the temperature to 400°C in 1 hour and keep the temperature for 1 hour; The three-stage ball milling was carried out under argon atmosphere.

2. A 5G base station shielding material, characterized in that: The raw materials include the wave absorbing agent described in claim 1.

3. A method for preparing the 5G base station shielding material according to claim 2, characterized in that: After the absorber is mixed with the rubber, the 5G base station shielding material is obtained by sequentially performing internal mixing, open mixing, sheeting and vulcanization.

4. The method for preparing a 5G base station shielding material according to claim 3, characterized in that: The mass ratio of the absorber to the rubber is 73:27.

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