Electromagnetic absorbing materials in the 600MHz-1GHz frequency band, their preparation methods and applications

Abstract

This invention relates to an electromagnetic wave absorbing material in the 600MHz-1GHz frequency band, its preparation method, and its applications. The electromagnetic wave absorbing material comprises a magnetic composite material and carbonyl iron particles, wherein the carbonyl iron particles are aggregates of multiple two-dimensional nano-carbonyl iron particles. The magnetic composite material comprises carbon crystal clusters composed of multiple carbon crystals and tungsten disulfide. At least a portion of the carbon crystals have tungsten disulfide and carbonyl iron particles attached to their surfaces, and at least a portion of the interstices between the carbon crystal clusters are filled with tungsten disulfide and carbonyl iron particles. The carbon crystals are three-dimensional prismatic in shape and have a porous structure, while the tungsten disulfide is plate-like. This electromagnetic wave absorbing material has the advantages of being lightweight and having good thermal stability, and exhibits strong absorption performance for electromagnetic waves in the 600MHz-1GHz frequency band.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic absorbing materials technology, and in particular to electromagnetic absorbing materials in the 600MHz-1GHz frequency band, their preparation methods, and applications. Background Technology

[0002] With the rapid development of electronic information technology, more and more electromagnetic compatibility (EMC) problems have arisen. Most EMC problems in the 600MHz-1GHz frequency band are interference from the system itself or harmonics generated by high-speed electronic circuits in some circuits.

[0003] Currently, in order to improve the electromagnetic compatibility of electronic devices in the 600MHz-1GHz frequency band, metal-based materials are usually used to form shielding shells around electronic components in electronic devices. However, metal-based materials have disadvantages such as high raw material cost, high density, narrow absorption bandwidth, and poor thermal stability. In addition, when using metal-based materials to prepare shielding shells, in order to meet the broadband absorption requirements, a large amount of electromagnetic wave absorber usually needs to be added, which leads to the deterioration of the processing performance of the shielding shell and a shortened service life. Summary of the Invention

[0004] Therefore, it is necessary to provide an electromagnetic absorbing material in the 600MHz-1GHz frequency band, its preparation method, and its application to address the aforementioned technical problems. This electromagnetic absorbing material has the advantages of being lightweight and having good thermal stability, and it also has strong absorption performance for electromagnetic waves in the 600MHz-1GHz frequency band.

[0005] This invention provides an electromagnetic absorbing material in the 600MHz-1GHz frequency band, comprising a magnetic composite material and carbonyl iron particles, wherein the carbonyl iron particles are aggregates of multiple two-dimensional nano-carbonyl iron particles;

[0006] The magnetic composite material comprises a carbon crystal cluster consisting of multiple carbon crystals and tungsten disulfide. At least a portion of the carbon crystals have tungsten disulfide and carbonyl iron particles attached to their surfaces, and at least a portion of the gaps between the carbon crystal clusters are filled with tungsten disulfide and carbonyl iron particles. The carbon crystals are three-dimensional prismatic and have a porous structure, while the tungsten disulfide is plate-like.

[0007] In one embodiment, the hardness of the two-dimensional nano-carbonyl iron is 100 N / mm. 2 -130N / mm 2 .

[0008] In one embodiment, the maximum diameter of the two-dimensional nano-carbonyl iron is 3nm-6nm, and the intermediate diameter is 2nm-5nm.

[0009] In one embodiment, the mass ratio of the carbonyl iron particles to the magnetic composite material is 4:1 to 4.5:1.

[0010] In one embodiment, the edge length of the carbon crystal is 10nm-13nm;

[0011] And / or, the maximum diameter of the tungsten disulfide is 3nm-6nm, and the intermediate diameter is 2nm-5nm.

[0012] In one embodiment, in the magnetic composite material, the ratio of the maximum diameter of the tungsten disulfide to the edge length of the carbon crystal is 1:1.8-1:3, and the mass ratio of the tungsten disulfide to the carbon crystal is 1:1.3-1:1.5.

[0013] A method for preparing an electromagnetic absorbing material in the 600MHz-1GHz frequency band as described above includes the following steps:

[0014] Tungsten disulfide and carbon crystal groups are provided, and then the tungsten disulfide and the carbon crystal groups are mixed to obtain a magnetic composite material; and

[0015] The magnetic composite material is mixed with two-dimensional nano-carbonyl iron to obtain an electromagnetic wave absorbing material.

[0016] In one embodiment, the method for preparing the two-dimensional nano-carbonyl iron includes: thermally decomposing pentacarbonyl iron, then reducing it with hydrogen to obtain soft powder, and finally grinding the soft powder to obtain two-dimensional nano-carbonyl iron.

[0017] In one embodiment, the step of mixing the magnetic composite material with two-dimensional nano-carbonyl iron includes: adding the magnetic composite material and the two-dimensional nano-carbonyl iron to a reducing solution, heating and stirring, and then cooling in a reducing gas atmosphere; wherein, in the heating and stirring step, the temperature is 40°C-60°C.

[0018] Application of an electromagnetic absorbing material in the 600MHz-1GHz frequency band as described above in the fabrication of electronic devices.

[0019] In the electromagnetic absorbing material provided by this invention, firstly, tungsten disulfide is in the form of sheets; secondly, carbon crystal is in the form of three-dimensional prismatic shapes with a porous structure; and thirdly, the three-dimensional prismatic carbon crystals can be tightly bonded together to form a carbon crystal cluster. Simultaneously, the sheet-like tungsten disulfide not only adheres to the surface of at least a portion of the carbon crystals but also fills at least a portion of the gaps between the carbon crystal clusters, enabling a tighter and more stable bond between the carbon crystals and tungsten disulfide. These three aspects work together to achieve synergy between the carbon crystals and tungsten disulfide. On the one hand, this allows the absorption bandwidth of the magnetic composite material in the electromagnetic absorbing material to cover electromagnetic waves in the 30MHz-8GHz frequency band. On the other hand, it gives the magnetic composite material high conductivity, enhancing the movement of electrons within it, resulting in an insertion loss of 20dB-30dB and excellent absorption performance.

[0020] Furthermore, since at least some of the carbon crystals are also coated with carbonyl iron particles, and at least some of the gaps in the carbon crystal clusters are filled with carbonyl iron particles, the surface of the magnetic composite material becomes more aggregated, further improving the density of the electromagnetic absorbing material. This results in the absorption bandwidth of the electromagnetic absorbing material changing from the 30MHz-8GHz band to the 600MHz-1GHz band, and the insertion loss increasing from 20dB-30dB to 30dB-40dB. In particular, the insertion loss reaches over 35dB in the 700MHz-850MHz band and over 38dB in the 600MHz band. This allows the electromagnetic absorbing material to not only absorb low-frequency (600MHz-800MHz) electromagnetic interference but also suppress high-frequency (800MHz-1GHz) electromagnetic wave emission, thereby improving the electromagnetic compatibility of electronic devices in the 600MHz-1GHz band and enabling better application in the security field.

[0021] In addition, since both carbon crystal and tungsten disulfide in the electromagnetic absorbing material of the present invention have the advantages of low density and good thermal stability, the electromagnetic absorbing material provided by the present invention also has the advantages of being lightweight and having good thermal stability.

[0022] In summary, when electromagnetic absorbing materials are used in electronic devices, firstly, they can enhance the signal transmission quality of electronic devices under 5G high-speed networks and improve the electromagnetic wave immunity of the 600MHz-1GHz frequency band in high-speed environments; secondly, they can enhance the functional stability of electronic devices; and thirdly, they will not increase the weight of electronic devices. Attached Figure Description

[0023] Figure 1 The image shows a scanning electron microscope (SEM) image of the carbon crystal group obtained in Example 1.

[0024] Figure 2 Microscopic image of tungsten disulfide prepared in Example 1 under a stereomicroscope;

[0025] Figure 3 This is a scanning electron microscope image of tungsten disulfide prepared in Example 1;

[0026] Figure 4 This is a high-magnification scanning electron microscope image of tungsten disulfide prepared in Example 1;

[0027] Figure 5 Microscopic image of the magnetic composite material prepared in Example 1 under a stereomicroscope;

[0028] Figure 6 This is a high-magnification scanning electron microscope image of the magnetic composite material prepared in Example 1;

[0029] Figure 7 The insertion loss diagram is shown for the magnetic composite material prepared in Example 1.

[0030] Figure 8 Microscopic image of the electromagnetic absorbing material prepared in Example 1 under a stereo microscope;

[0031] Figure 9 The diagram shows the insertion loss of the electromagnetic absorbing material prepared in Example 1. Detailed Implementation

[0032] To facilitate understanding of the present invention, it will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. Rather, these embodiments or examples are provided to make the disclosure of the present invention more thorough and complete.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments or examples only and is not intended to limit the invention. The optional scope of the term "and / or" as used herein includes any one of two or more of the related listed items, as well as any and all combinations of the related listed items, including any two related listed items, any more related listed items, or a combination of all related listed items.

[0034] The electromagnetic absorbing material for the 600MHz-1GHz frequency band provided by this invention includes a magnetic composite material and carbonyl iron particles. The carbonyl iron particles are aggregates of multiple two-dimensional nano-carbonyl iron particles. The magnetic composite material includes a carbon crystal group composed of multiple carbon crystals and tungsten disulfide. At least some of the carbon crystals have tungsten disulfide and carbonyl iron particles attached to their surfaces, and at least some of the gaps between the carbon crystal groups are filled with tungsten disulfide and carbonyl iron particles. The carbon crystals are three-dimensional prismatic and have a porous structure, while the tungsten disulfide is plate-like.

[0035] Carbon crystal and tungsten disulfide have diverse structures, and different structural types of carbon crystal and tungsten disulfide have different electromagnetic wave conversion capabilities.

[0036] First, in this invention, a three-dimensional prismatic carbon crystal is selected, which also has a porous structure. Thus, when electromagnetic waves are transmitted to the surface of the carbon crystal, whether they are low-frequency or high-frequency electromagnetic waves, the electromagnetic waves are reflected multiple times in the porous structure of the carbon crystal, thereby converting the electromagnetic waves into heat energy more quickly and efficiently, and thus achieving a better absorption effect. Furthermore, tungsten disulfide in sheet form has the advantage of enhancing planar electrical transport performance. When tungsten disulfide in sheet form is selected, electromagnetic waves can be converted into heat energy more quickly and efficiently, thus achieving a better absorption effect.

[0037] In addition, the three-dimensional prismatic carbon crystals can be tightly bonded to form a carbon crystal cluster. Meanwhile, the plate-like tungsten disulfide not only adheres to the surface of at least part of the carbon crystals, but also fills at least part of the gaps in the carbon crystal cluster, so that the carbon crystals and tungsten disulfide can be bonded more tightly and stably.

[0038] Thus, through the combined effect of the above three aspects, carbon crystal and tungsten disulfide can work synergistically to enable the magnetic composite material of the electromagnetic absorbing material to cover the absorption bandwidth of low-frequency electromagnetic waves to high-frequency electromagnetic waves, such as 30MHz-8GHz. On the other hand, it enables the magnetic composite material to have high conductivity, enhances the movement of electrons in the magnetic composite material, and enhances the insertion loss of the magnetic composite material, such as 20dB-30dB. This results in the magnetic composite material having excellent absorption performance in the absorption frequency band.

[0039] Furthermore, since at least some of the carbon crystals are also covered with carbonyl iron particles, and at least some of the gaps in the carbon crystal clusters are also filled with carbonyl iron particles, the surface of the magnetic composite material becomes more aggregated, further improving the density of the electromagnetic absorbing material. As a result, the absorption bandwidth of the electromagnetic absorbing material changes from the 30MHz-8GHz band to the 600MHz-1GHz band, and the insertion loss increases from 20dB-30dB to 30dB-40dB. In particular, the insertion loss reaches more than 35dB in the 700MHz-850MHz band and more than 38dB in the 600MHz band.

[0040] Since the hardness of two-dimensional nano-carbonyl iron affects the density of electromagnetic absorbing materials, in one embodiment, the hardness of the two-dimensional nano-carbonyl iron is 100 N / mm. 2 -130N / mm 2 , including but not limited to 100N / mm 2 105 N / mm 2 110N / mm 2 115N / mm 2 120N / mm 2 125N / mm 2 Or 130N / mm 2 This results in electromagnetic absorbing materials possessing excellent density and flexibility.

[0041] In order to achieve better synergy between the magnetic composite material and the carbonyl iron particles, thereby enabling the electromagnetic absorbing material to have superior absorption performance in the 600MHz-1GHz frequency band, in one embodiment, the mass ratio of carbonyl iron particles to magnetic composite material is 4:1-4.5:1, including but not limited to 4:1, 4.1:1, 4.2:1, 4.25:1, 4.3:1, 4.4:1 or 4.5:1.

[0042] Since the size of two-dimensional nano-carbonyl iron affects the particle size of carbonyl iron particles, and thus the density of electromagnetic absorbing materials, in one embodiment, the maximum diameter of the two-dimensional nano-carbonyl iron is 3nm-6nm, including but not limited to 3nm, 4nm, 5nm or 6nm, and the middle diameter is 2nm-5nm, including but not limited to 2nm, 3nm, 4nm or 5nm, thereby making the particle size of carbonyl iron particles 3nm-8nm, including but not limited to 3nm, 4nm, 5nm, 6nm, 7nm or 8nm; it can be understood that a tangent rectangle is drawn on the maximum projection surface of the two-dimensional nano-carbonyl iron, with the long side of the rectangle being the maximum diameter and the short side of the rectangle being the middle diameter.

[0043] Since the edge length of carbon crystal affects the absorption frequency band and absorption performance of electromagnetic absorbing materials, in one embodiment, the edge length of carbon crystal is preferably 10nm-13nm, including but not limited to 10nm, 10.5nm, 11nm, 11.5nm, 12nm, 12.5nm or 13nm, so that the electromagnetic absorbing material has better absorption performance in the 600MHz-1GHz frequency band.

[0044] To achieve a tighter and more stable bond between carbon crystal and tungsten disulfide, and to enhance the electromagnetic absorbing material's absorption performance in the 600MHz-1GHz frequency band, the maximum diameter of the tungsten disulfide is preferably smaller than the edge length of the carbon crystal. In one embodiment, the maximum diameter of the tungsten disulfide is 3nm-6nm, including but not limited to 3nm, 3.5nm, 4nm, 4.5nm, 5nm, 5.5nm, or 6nm, and the intermediate diameter is 2nm-5nm, including but not limited to 2nm, 2.5nm, 3nm, 3.5nm, 4nm, 4.5nm, or 5nm. Preferably, the tungsten disulfide is rectangular. It is understood that a tangent rectangle is drawn over the maximum projection surface of the tungsten disulfide, with the longer side of the rectangle representing the maximum diameter and the shorter side representing the intermediate diameter.

[0045] In order to enable a tighter and more stable bond between carbon crystal and tungsten disulfide, in one embodiment, the ratio of the maximum diameter of tungsten disulfide to the edge length of carbon crystal is 1:1.8-1:3, including but not limited to 1:1.8, 1:1.9, 1:2, 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, 1:2.8, 1:2.9 or 1:3.

[0046] In order to achieve better synergy between carbon crystal and tungsten disulfide, thereby enabling the electromagnetic absorbing material to have superior absorption performance in the 600MHz-1GHz frequency band, the mass ratio of tungsten disulfide to carbon crystal in the magnetic composite material is preferably 1:1.3-1:1.5; including but not limited to 1:1.3, 1:1.35, 1:1.4, 1:1.4.5 or 1:1.5.

[0047] Since both carbon crystal and tungsten disulfide in the electromagnetic absorbing material of this invention have the advantages of low density and good thermal stability, the electromagnetic absorbing material provided by this invention also has the advantages of being lightweight and having good thermal stability.

[0048] In one embodiment, in order to improve the thermal conductivity of the electromagnetic absorbing material, the magnetic composite material further includes thermally conductive particles, at least a portion of the carbon crystals and at least a portion of the tungsten disulfide surfaces are covered with thermally conductive particles, and at least a portion of the gaps between the carbon crystal clusters are filled with thermally conductive particles.

[0049] This invention does not impose any special restrictions on the type of thermally conductive particles. The thermally conductive particles may be selected from at least one of the following: graphite, carbon black, carbon nanotubes, carbon fibers, diamond, copper (Cu), silver (Ag), gold (Au), aluminum (Al), nickel (Ni), silicon carbide (SiC), boron carbide (B4C), titanium carbide (TiC), zirconium carbide (ZrC), chromium carbide (Cr3C2), tungsten carbide (WC), silicon nitride (Si3N4), boron nitride (BN), aluminum nitride (AlN), beryllium oxide (BeO), aluminum oxide (Al2O3), or zinc oxide (ZnO). When the magnetic composite material includes thermally conductive particles, the mass fraction of the thermally conductive particles in the magnetic composite material is less than or equal to 10%.

[0050] In summary, the electromagnetic absorbing material provided by this invention can not only absorb electromagnetic interference in the low-frequency band (600MHz-800MHz), but also suppress electromagnetic wave emission in the high-frequency band (800MHz-1GHz), thereby improving the electromagnetic compatibility of electronic devices in the 600MHz-1GHz frequency band and making it better suited for use in the security field.

[0051] Since both carbon crystal and tungsten disulfide in the electromagnetic absorbing material of this invention have the advantages of low density and good thermal stability, the electromagnetic absorbing material provided by this invention also has the advantages of being lightweight and having good thermal stability.

[0052] This invention also provides a method for preparing electromagnetic absorbing materials in the 600MHz-1GHz frequency band as described above, comprising the following steps:

[0053] S10, providing magnetic composite materials; and

[0054] S20. Mix the magnetic composite material with two-dimensional nano-carbonyl iron to obtain an electromagnetic absorbing material.

[0055] Step S10, the step of providing the magnetic composite material includes:

[0056] S101, providing tungsten disulfide and carbon crystal groups; and

[0057] S102. Tungsten disulfide and carbon crystals are mixed to obtain a magnetic composite material.

[0058] In step S101, the present invention does not impose any special restrictions on the preparation method of tungsten disulfide and carbon crystal group, as long as the tungsten disulfide obtained is in the form of a sheet, the carbon crystal in the carbon crystal group is in the form of a three-dimensional prismatic shape, and has a channel structure.

[0059] In one embodiment, the step of providing tungsten disulfide includes: subjecting tungsten chloride to a hydrothermal reaction with thioacetamide, and then sulfiding the resulting solid product to obtain tungsten disulfide. It should be noted that the sulfidation step of the solid product stabilizes the generated tungsten disulfide and prevents its reduction during the mixing step with the carbon crystal group.

[0060] In the hydrothermal reaction solution, the mass fraction of tungsten chloride, the mass fraction of thioacetamide, the mass ratio of tungsten chloride to thioacetamide, temperature, and time all affect the properties of tungsten disulfide, such as its maximum diameter, intermediate diameter, and shape. In one embodiment, in the step of hydrothermally reacting tungsten chloride with thioacetamide, the mass fraction of tungsten chloride in the hydrothermal reaction solution is 0.4%-0.7%, including but not limited to 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, or 0.7%. The mass fraction of thioacetamide in the hydrothermal reaction solution is... The mass fraction of the tungsten disulfide is 0.9%-1.2%, including but not limited to 0.9%, 1.0%, 1.1% or 1.2%. The hydrothermal reaction temperature is preferably 270℃-290℃, including but not limited to 270℃, 275℃, 280℃, 285℃ or 290℃. The reaction time is preferably 12h-24h, including but not limited to 12h, 14h, 16h, 18h, 20h, 22h or 24h. As a result, the maximum diameter of the obtained tungsten disulfide is 3nm-6nm, the intermediate diameter is 2nm-5nm, and part of the tungsten disulfide is rectangular in shape.

[0061] In one embodiment, the step of providing carbon crystal clusters includes: mixing hydrogen peroxide with graphene oxide, then mixing it with a suspension of porous graphene oxide, concentrating it after heat preservation, and drying the concentrated product under vacuum conditions to obtain carbon crystal clusters; wherein, the chemical bonds between graphene oxide and porous graphene oxide are broken and recombined to form three-dimensional prismatic carbon crystals with a porous structure.

[0062] In the step of mixing hydrogen peroxide with graphene oxide, the mass fraction of hydrogen peroxide and the mass fraction of graphene oxide affect the edge length and pore size of the carbon crystal. The mass fraction of hydrogen peroxide is 1.5%-3%, including but not limited to 1.5%, 2.0%, 2.5% or 3%, and the mass fraction of graphene oxide is 40%-60%, including but not limited to 40%, 42.5%, 45%, 47.5%, 50%, 52.5%, 55%, 57.5% or 60%, thereby making the edge length of the carbon crystal 10nm-13nm.

[0063] In the step of mixing hydrogen peroxide with graphene oxide and then mixing it with a suspension of porous graphene oxide, the mass fraction of hydrogen peroxide to the mass fraction of the graphene oxide dispersion is 1:25-1:35, including but not limited to 1:25, 1:26, 1:27, 1:28, 1:29, 1:30, 1:31, 1:32, 1:33, 1:34 or 1:35; thereby making the edge length of the carbon crystal 10nm-13nm.

[0064] In one embodiment, the temperature in the heat preservation and concentration step is 100°C-150°C, including but not limited to 100°C, 110°C, 120°C, 130°C, 140°C or 150°C.

[0065] In step S20, the present invention does not impose any special restrictions on the step of mixing tungsten disulfide and carbon crystal clusters. Regardless of the mixing method, at least some of the carbon crystals can be coated with tungsten disulfide, and at least some of the gaps in the carbon crystal clusters can be filled with tungsten disulfide.

[0066] In one embodiment, the step of mixing tungsten disulfide and carbon crystal clusters includes: sulfiding a suspension containing carbon crystal clusters, then mixing it with tungsten disulfide, separating the solid product, and annealing it under a protective gas atmosphere. The step of sulfiding the suspension containing carbon crystal clusters prevents the carbon crystals from reducing the tungsten disulfide, allowing the tungsten disulfide to stably adhere to the surface of some of the carbon crystals or fill at least some of the gaps between the carbon crystal clusters.

[0067] Optionally, the step of sulfiding the suspension containing carbon crystal clusters includes: mixing the suspension containing carbon crystal clusters with a solution of thiopropane sulfonic acid (MPS) and keeping it at 3°C-5°C for 20-24 hours.

[0068] Optionally, in the step of annealing under a protective gas atmosphere, the temperature is 290℃-310℃, including but not limited to 290℃, 295℃, 300℃, 305℃ or 310℃, and the time is 4h-6h, including but not limited to 4h, 4.5h, 5h, 5.5h or 6h, and the protective gas is selected from at least one of inert gas or nitrogen.

[0069] When the magnetic composite material also includes thermally conductive particles, after the step of mixing tungsten disulfide and carbon crystal groups, the mixture further includes a step of mixing the product with the thermally conductive particles.

[0070] In step S20, the present invention does not impose any special restrictions on the source of two-dimensional nano-carbonyl iron. Two-dimensional nano-carbonyl iron can be prepared by itself or obtained directly from commercial products. The present invention does not impose any special restrictions on the step of mixing magnetic composite material with two-dimensional nano-carbonyl iron. Regardless of the mixing method, carbonyl iron particles can be attached to the surface of at least part of the carbon crystals, and carbonyl iron particles can be filled in at least part of the gaps between the carbon crystal groups.

[0071] Two-dimensional carbonyl iron nanoparticles can be obtained by thermally decomposing pentacarbonyl iron. The specific steps include: thermally decomposing pentacarbonyl iron, then reducing it with hydrogen to obtain a soft powder, and finally grinding the soft powder to obtain two-dimensional carbonyl iron nanoparticles. Grinding the soft powder can change the anisotropy of the shape and the particle size of the two-dimensional carbonyl iron nanoparticles, thereby making the two-dimensional carbonyl iron nanoparticles finer and thus better able to mix with magnetic composite materials.

[0072] In one embodiment, the particle size of the powder is 80nm-120nm. During the grinding step, the grinding pressure is 0.2MPa-1.0MPa, including but not limited to 0.2MPa, 0.3MPa, 0.4MPa, 0.5MPa, 0.6MPa, 0.7MPa, 0.8MPa, 0.9MPa, or 1.0MPa. The grinding speed is 100rpm-400rpm, including but not limited to 100rpm, 150rpm, 200rpm, 210rpm, 220rpm, and 230rpm. The grinding speeds are set at m, 240rpm, 250rpm, 260rpm, 270rpm, 280rpm, 290rpm, 300rpm, 350rpm, or 400rpm, with grinding times ranging from 10h to 24h, including but not limited to 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, and 24h. This results in a maximum diameter of 3nm-5nm for two-dimensional carbonyl iron nanoparticles, an intermediate diameter of 2nm-4nm, and a hardness of 100N / mm. 2 -130N / mm 2 .

[0073] Understandably, iron pentacarbonyl can be obtained by reacting CO with iron under high temperature and pressure. In order to avoid CO from undergoing a disproportionation reaction, NH3 is usually introduced as a protective gas.

[0074] It should be noted that, due to the high reactivity of two-dimensional nano-carbonyl iron, it will automatically aggregate to form carbonyl iron particles.

[0075] The steps of mixing the magnetic composite material with two-dimensional nano-carbonyl iron include: adding the magnetic composite material and two-dimensional nano-carbonyl iron to a reducing solution, heating and stirring, and then cooling in a reducing gas atmosphere; both the reducing solution and the reducing gas can prevent the two-dimensional nano-carbonyl iron from being oxidized. In one embodiment, the reducing solution includes a ferrous chloride solution, and the reducing gas is selected from hydrogen or CO.

[0076] In one embodiment, the temperature during the heating and stirring step is 40°C-60°C, including but not limited to 40°C, 45°C, 50°C, 55°C or 60°C.

[0077] The method for preparing electromagnetic absorbing materials in the 600MHz-1GHz frequency band provided by this invention achieves simple preparation of electromagnetic absorbing materials that are lightweight, have good thermal stability, and have strong absorption performance for electromagnetic waves in the 600MHz-1GHz frequency band.

[0078] The present invention also provides an application of the electromagnetic absorbing material in the 600MHz-1GHz frequency band as described above in the fabrication of electronic devices.

[0079] When electromagnetic absorbing materials are made into absorbing materials and applied to electronic devices, firstly, they can enhance the signal transmission quality of electronic devices under 5G high-speed networks and enhance the electromagnetic wave anti-interference capability of high-frequency bands in high-speed environments; secondly, they can enhance the functional stability of electronic devices; and thirdly, they will not increase the weight of electronic devices.

[0080] The following specific examples will further illustrate electromagnetic absorbing materials in the 600MHz-1GHz frequency band, their preparation methods, and applications.

[0081] Example 1

[0082] 5 mL of a 3% (w / w) hydrogen peroxide solution was mixed with 100 mL of a 35% (w / w) graphene oxide dispersion (solvent: 1 mol / L hydrochloric acid) to form a homogeneous and stable solution. Then, 150 mL of a 60% (w / w) porous graphene oxide suspension (solvent: 1 mol / L hydrochloric acid) was added. The mixture was then placed in a polytetrafluoroethylene-lined reactor, heated to 130°C, and maintained at a constant temperature for 13 hours. Excess hydrogen peroxide solution was removed by high-speed centrifugation and rinsing with deionized water. After concentration, the concentrated product was dried under vacuum at high temperature to obtain carbon crystal clusters. Figure 1 The image shown is a scanning electron microscope (SEM) image of a carbon crystal group. Figure 1 It can be seen that the carbon crystals in the carbon crystal group are three-dimensional prismatic and have a porous structure.

[0083] Weigh 0.6 g of WCl6 and 1.12 g of thioacetamide, slowly dissolve them in 105 mL of deionized water, stir at room temperature for 2 hours, then transfer to a temperature-controlled device with a polytetrafluoroethylene liner, heat to 280 °C, and maintain the temperature for one day. After the reaction is complete, allow the product to cool naturally to room temperature, filter to obtain the precipitate, wash repeatedly with deionized water at 100 °C, and finally vacuum dry at 61 °C to obtain a solid product. For further sulfidation, disperse this solid product in a freshly prepared MPS / dichloromethane mixed solution with a volume ratio of 1:15, refrigerate at 4 °C for one day, and then anneal the prepared product at 295 °C for 5 hours under an argon atmosphere to finally obtain tungsten disulfide; Figure 2 The image shown is a microscopic image of tungsten disulfide under a stereo microscope. Figure 3 The image shown is a scanning electron microscope (SEM) image of tungsten disulfide. Figure 4 The image shown is a high-magnification scanning electron microscope (SEM) image of tungsten disulfide. Figure 2-4 It can be seen that tungsten disulfide is in the form of flakes.

[0084] The obtained carbon crystal clusters were uniformly dispersed in water to prepare a 110 mL suspension with a concentration of 1 g / L. 110 mL of a 1 g / L hydrochloric acid solution was added, and the mixture was stirred at room temperature for 2 hours. The mixture was then transferred to a stainless steel reactor lined with PTFE and heated to 265°C for one day. After the reaction was complete, the sample was allowed to cool naturally to room temperature. A black precipitate was obtained by filtration, washed repeatedly with deionized water, and then vacuum dried at 60°C to obtain the precipitate. This precipitate was dispersed in a freshly prepared MPS / dichloromethane mixed solution with a volume ratio of 1:14 and refrigerated at 3°C ​​for one day. It was then mixed with tungsten disulfide and annealed at 300°C for 5 hours under an inert gas atmosphere to obtain the magnetic composite material. Figure 5 The image shown is a microscopic image of the magnetic composite material prepared in Example 1 under a stereomicroscope. Figure 6 The image shown is a high-magnification scanning electron microscope image of the magnetic composite material. Figure 7 This is a diagram showing the insertion loss of magnetic composite materials.

[0085] 10g of iron was placed in a CO atmosphere and subjected to a high-temperature and high-pressure reaction at 210℃ and 1.5MPa to obtain an oily substance. The oily substance was then separated under low pressure to obtain a soft powder, which was reduced with hydrogen to obtain the soft powder. Finally, the soft powder was ground at a pressure of 0.7MPa, a speed of 150rpm, and a grinding time of 12h to obtain two-dimensional nano-carbonyl iron.

[0086] The prepared two-dimensional nano-carbonyl iron and magnetic composite material were added to a ferrous chloride solution at a mass ratio of 4:1, heated and stirred at 50°C for 6 hours, and then cooled in a reducing gas CO to obtain the electromagnetic absorbing material. Figure 8 The image shown is a microscopic view of an electromagnetic absorbing material, such as... Figure 9 The diagram shows the insertion loss of the electromagnetic absorbing material.

[0087] Comparative Example 1

[0088] Graphene oxide was dispersed in a 1:1 mixture of water and N,N-dimethylformamide at a concentration of 1.0 mg / mL. Then, 0.6 g of tungsten hexachloride and 1.2 g of thioacetamide were added sequentially and stirred until homogeneous. The resulting mixture was heated at 120 °C for reaction. The solid product after reaction was centrifuged multiple times, washed with alcohol and water to remove impurities, and then freeze-dried at -50 °C for 24 hours to obtain the three-dimensional self-assembled structure of tungsten disulfide-reduced graphene oxide.

[0089] Comparative Example 2

[0090] Tungsten disulfide nanosheets and graphene were mixed under ultrasonic conditions to obtain graphene-modified tungsten disulfide nanosheets. The two two-dimensional layered structures can form a heterolayer structure.

[0091] Comparative Example 3

[0092] Replacing graphene oxide with layered graphene, and replacing porous graphene oxide with layered porous graphene, results in carbon crystals that are sheet-like, not three-dimensional prismatic, and do not have a porous structure.

[0093] Comparative Example 4

[0094] By replacing WCl6 with tungsten powder and thioacetamide with sulfur powder, the prepared tungsten disulfide is in block form, not in flake form.

[0095] Test Example 1

[0096] The density, thermal conductivity, and absorption performance of the electromagnetic absorbing materials obtained in Example 1 and Comparative Examples 1-4 were tested. The test methods are shown below, and the test results are shown in Table 1.

[0097] Density: Place the sample to be tested in 0.8L of water until a 1L mixture is obtained. Weigh the total mass of the 1L mixture and subtract the mass of 0.8L of water to get the mass of the sample to be tested. Divide the mass of the sample to be tested by 0.2L to get the density of the sample to be tested.

[0098] Thermal conductivity: Measured using the steady-state heat flow method, referring to the national standard GB / T8722.

[0099] Absorption performance: Refer to the national standard GB / T32596 to test the absorption bandwidth and insertion loss.

[0100] Table 1

[0101]

[0102] Example 2

[0103] Example 2 was carried out in accordance with Example 1, except that the grinding pressure was 0.8 MPa, the grinding speed was 350 rpm, the grinding time was 12 h, and the maximum diameter of the two-dimensional nano carbonyl iron in the electromagnetic absorbing material was 3 nm, and the middle diameter was 2 nm.

[0104] Example 3

[0105] Example 3 was carried out in accordance with Example 1, except that the grinding pressure was 0.6 MPa, the grinding speed was 350 rpm, the grinding time was 12 h, and the maximum diameter of the two-dimensional nano carbonyl iron in the electromagnetic absorbing material was 5 nm, and the middle diameter was 4 nm.

[0106] Example 4

[0107] Example 4 was carried out in accordance with Example 1, except that the grinding pressure was 0.5 MPa, the grinding speed was 350 rpm, the grinding time was 12 h, and the maximum diameter of the two-dimensional nano carbonyl iron in the electromagnetic absorbing material was 6 nm, and the middle diameter was 5 nm.

[0108] Test Example 2

[0109] The density, thermal conductivity, and absorption performance of the electromagnetic absorbing materials obtained in Examples 2-4 were tested. The test methods are shown below, and the test results are shown in Table 2.

[0110] Table 2

[0111]

[0112] Example 5

[0113] Example 5 was carried out in accordance with Example 3, except that the mass ratio of carbonyl iron particles to magnetic composite material was 4:1.

[0114] Example 6

[0115] Example 6 was carried out in accordance with Example 3, except that the mass ratio of carbonyl iron particles to magnetic composite material was 4.25:1.

[0116] Example 7

[0117] Example 7 was carried out in accordance with Example 3, except that the mass ratio of carbonyl iron particles to magnetic composite material was 4.5:1.

[0118] Test Example 3

[0119] The density, thermal conductivity, and absorption performance of the electromagnetic absorbing materials obtained in Examples 5-7 were tested. The test methods are shown below, and the test results are shown in Table 3.

[0120] Table 3

[0121]

[0122] Example 8

[0123] Example 8 differs from Example 6 in that, in the step of preparing the carbon crystal group, the mass fraction of hydrogen peroxide solution to the mass fraction of graphene oxide dispersion is 1:25, and the edge length of the carbon crystal is 10 nm.

[0124] Example 9

[0125] Example 9 differs from Example 6 in that, in the step of preparing the carbon crystal group, the mass fraction of hydrogen peroxide solution to the mass fraction of graphene oxide dispersion is 1:30, and the edge length of the carbon crystal is 11.5 nm.

[0126] Example 10

[0127] Example 10 differs from Example 6 in that, in the step of preparing the carbon crystal group, the mass fraction of hydrogen peroxide solution to the mass fraction of graphene oxide dispersion is 1:35, and the edge length of the carbon crystal is 13 nm.

[0128] Test Example 4

[0129] The density, thermal conductivity, and absorption performance of the electromagnetic absorbing materials obtained in Examples 8-10 were tested. The test methods are shown below, and the test results are shown in Table 4.

[0130] Table 4

[0131]

[0132] Example 11

[0133] Example 11 was carried out in accordance with Example 9, except that in the step of preparing tungsten disulfide, the ratio of WCl6 to thioacetamide was 1:2, the maximum diameter of tungsten disulfide was 4 nm, and the middle diameter was 3 nm.

[0134] Example 12

[0135] Example 12 was carried out in accordance with Example 9, except that in the step of preparing tungsten disulfide, the ratio of WCl6 and thioacetamide was reduced to 1:3, the maximum diameter of tungsten disulfide was 5 nm, and the middle diameter was 4 nm.

[0136] Example 13

[0137] Example 13 was carried out in accordance with Example 9, except that in the step of preparing tungsten disulfide, the ratio of WCl6 to thioacetamide was reduced to 1:3, the ion cleaning temperature was 120°C, and the maximum diameter of tungsten disulfide was 6 nm and the middle diameter was 5 nm.

[0138] Test Example 5

[0139] The density, thermal conductivity, and absorption performance of the electromagnetic absorbing materials obtained in Examples 11-13 were tested. The test methods are shown below, and the test results are shown in Table 5.

[0140] Table 5

[0141]

[0142] Example 14

[0143] Example 14 was carried out in accordance with Example 12, except that in the step of mixing tungsten disulfide and carbon crystals, the mass ratio of tungsten disulfide to carbon crystals was 1:1.3.

[0144] Example 15

[0145] Example 15 was carried out in accordance with Example 12, except that in the step of mixing tungsten disulfide and carbon crystals, the mass ratio of tungsten disulfide to carbon crystals was 1:1.4.

[0146] Example 16

[0147] Example 16 was carried out with reference to Example 12, except that in the step of mixing tungsten disulfide and carbon crystals, the mass ratio of tungsten disulfide to carbon crystals was 1:1.5.

[0148] Test Example 6

[0149] The density, thermal conductivity, and absorption performance of the electromagnetic absorbing materials obtained in Examples 14-16 were tested. The test methods are shown below, and the test results are shown in Table 6.

[0150] Table 6

[0151]

[0152] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0153] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. An electromagnetic wave absorbing material in the frequency range of 600 MHz-1 GHz, characterized in that, The magnetic composite material and the carbonyl iron particles are a plurality of two-dimensional nanometer carbonyl iron agglomerates; The magnetic composite material comprises a carbon crystal group composed of a plurality of carbon crystals and tungsten disulfide, at least part of the surfaces of the carbon crystals are attached with the tungsten disulfide and the carbonyl iron particles, and at least part of the gaps of the carbon crystal group are filled with the tungsten disulfide and the carbonyl iron particles, wherein the carbon crystals are three-dimensional prisms, and the carbon crystals have a pore structure, and the tungsten disulfide is in a sheet shape.

2. The electromagnetic wave absorbing material for 600 MHz-1 GHz band according to claim 1, wherein, The hardness of the two-dimensional nanometer carbonyl iron is 100 N / mm 2 -130 N / mm 2 . 3.The electromagnetic wave absorbing material for 600MHz-1GHz band of claim 2, wherein, The maximum diameter of the two-dimensional nanometer carbonyl iron is 3-6 nm, and the intermediate diameter is 2-5 nm. 4.The electromagnetic wave absorbing material for 600MHz-1GHz band of claim 1, wherein, The mass ratio of the carbonyl iron particles to the magnetic composite material is 4:1-4.5:

1.

5. The electromagnetic wave absorbing material for 600 MHz-1 GHz band according to any one of claims 1 to 4, wherein The edge length of the carbon crystal is 10-13 nm. The maximum diameter of the two-dimensional nanometer carbonyl iron is 3-6 nm, and the intermediate diameter is 2-5 nm.

6. The electromagnetic wave absorbing material of 600 MHz-1 GHz band according to any one of claims 1-4, characterized in that, In the magnetic composite material, the ratio of the maximum diameter of the tungsten disulfide to the edge length of the carbon crystal is 1:1.8-1:3, and the mass ratio of the tungsten disulfide to the carbon crystal is 1:1.3-1:1.

5.

7. A method for preparing an electromagnetic wave absorbing material in the frequency range of 600 MHz-1 GHz as claimed in any one of claims 1-6, characterized in that, The method comprises the following steps: Providing tungsten disulfide and a carbon crystal group, and then mixing the tungsten disulfide and the carbon crystal group to obtain a magnetic composite material; And Mixing the magnetic composite material with two-dimensional nanometer carbonyl iron to obtain an electromagnetic wave absorbing material.

8. The method for preparing the electromagnetic absorbing material in the 600MHz-1GHz frequency band according to claim 7, characterized in that, The preparation method of the two-dimensional nanometer carbonyl iron comprises the following steps: subjecting iron pentacarbonyl to a thermal decomposition reaction, then reducing the soft powder with hydrogen to obtain a soft powder, and finally grinding the soft powder to obtain two-dimensional nanometer carbonyl iron.

9. The method of claim 8, wherein the electromagnetic wave absorbing material in the 600 MHz-1 GHz band is prepared by the method, characterized in that, The step of mixing the magnetic composite material with two-dimensional nanometer carbonyl iron comprises the following steps: adding the magnetic composite material and the two-dimensional nanometer carbonyl iron into a solution with reducing property, heating and stirring, and then cooling in an atmosphere of a reducing gas; wherein the temperature in the step of heating and stirring is 40-60°C.

10. Use of the electromagnetic wave absorbing material of 600 MHz-1 GHz frequency band according to any one of claims 1-6 in the preparation of electronic equipment.

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