Composite wave-absorbing material and preparation method thereof

Abstract

The embodiment of the invention provides a composite wave-absorbing material and a preparation method thereof.According to the preparation method, carbonyl iron powder and a dielectric material are mixed to form a mixture, then the mixture is placed in a coating tank, and in the protective gas atmosphere, a hammer in the coating tank is used for conducting hot pressing treatment on the mixture, and the composite wave-absorbing material is obtained. Coating the surface of the carbonyl iron powder with the dielectric material to obtain the composite wave-absorbing material; pressing treatment is conducted through physical heating and hammer hammering, micro-area high temperature is formed on the surface of the carbonyl iron powder, the technology is simple, the dielectric material can be adsorbed to the surface of the carbonyl iron powder, the similar welding effect is achieved, the dielectric material and the carbonyl iron powder are combined more powerfully, and the bonding strength of the carbonyl iron powder is improved. Therefore, the method can effectively relieve the problem that the coating layer is easy to peel off due to the fact that the existing process for forming the SiO2 coating layer on the surface of the carbonyl iron powder is complex and the interface bonding is weak.

Description

Technical Field

[0001] The present application relates to the technical field of ferromagnetic absorbing materials, and in particular to a composite absorbing material based on carbonyl iron powder and a preparation method thereof. Background Art

[0002] Carbonyl iron powder has become an important candidate for high-performance microwave absorbing materials due to its high saturation magnetization, excellent magnetic permeability, and temperature stability. However, it has the following problems: (1) Low resistivity leads to a high complex dielectric constant, which is mismatched with the complex magnetic permeability and exacerbates electromagnetic wave reflection; (2) It is easily oxidized at high temperatures, causing magnetic properties to degrade; and (3) Conductive networks are easily formed between particles, exacerbating dielectric loss.

[0003] To address the above problems, existing technologies mostly use SiO2 coating modification to isolate oxidation and reduce the dielectric constant. However, traditional methods (such as the sol-gel method) have problems such as complex process, poor uniformity of the coating layer, and weak interface bonding that leads to easy peeling of the coating layer. Summary of the Invention

[0004] The technical problem to be solved by the present application is to provide a composite absorbing material and a preparation method thereof, so as to solve the problem that the existing SiO2 coating layer formed on the surface of carbonyl iron powder has a complex process and weak interface bonding, resulting in easy peeling of the coating layer.

[0005] In order to solve the above problems, this application is implemented through the following technical solutions:

[0006] This application proposes a method for preparing a composite absorbing material, which includes:

[0007] mixing carbonyl iron powder with a dielectric material to form a mixture;

[0008] The mixed material is placed in a coating tank body, and in a protective gas atmosphere, the mixed material is subjected to a hot pressing treatment using a hammer head in the coating tank body to coat the dielectric material on the surface of the carbonyl iron powder to obtain a composite absorbing material; wherein the hammer head can move relative to the coating tank body.

[0009] Furthermore, in the electrical preparation method, the hammer head is rotatably arranged in the coating tank body, and there is a gap between the hammer head and the inner wall of the coating tank body; by controlling the rotation of the coating tank body, the hammer head can rotate relative to the coating tank body and hammer the mixture in the coating tank body, thereby realizing hot pressing treatment of the mixture.

[0010] Furthermore, in the electrical preparation method, during the hot pressing treatment, the temperature of the coated tank body is controlled to be 100°C to 200°C, and the rotation speed of the coated tank body is controlled to be 2500 rpm to 3500 rpm, and the time is controlled to be 10 minutes to 30 minutes.

[0011] Furthermore, in the electrical preparation method, the gap between the hammer head and the inner wall of the coating tank body is 0.1 mm to 1 mm.

[0012] Furthermore, before the mixture is subjected to a hot pressing treatment using the hammer in the coating tank, the electrical preparation method further comprises:

[0013] The mixture is kept warm at 100° C. to 200° C. for 1 to 20 minutes.

[0014] Furthermore, before mixing the carbonyl iron powder with the dielectric material, the electrical preparation method further comprises:

[0015] The carbonyl iron powder is subjected to annealing treatment.

[0016] Furthermore, in the electrical preparation method, the carbonyl iron powder is subjected to annealing treatment, comprising:

[0017] In a protective gas atmosphere, the temperature is raised to 300-550°C for heat treatment for 3-5 hours, and then lowered to 20-30°C before discharging.

[0018] Furthermore, in the above-mentioned electrochemical preparation method, the mixture further comprises a pressing aid, and the pressing aid is selected from at least one of polyethylene glycol, a silane coupling agent, and calcium stearate.

[0019] Furthermore, in the electrical preparation method, the carbonyl iron powder is mixed with the dielectric material, comprising:

[0020] The dielectric material and the grinding aid are mixed with the carbonyl iron powder according to the mass percentage of the dielectric material to the carbonyl iron powder being 1% to 8% and the mass percentage of the grinding aid to the carbonyl iron powder being 1% to 5%.

[0021] Furthermore, in the electrical preparation method, the dielectric material is at least one of nano-scale silicon oxide and nano-scale aluminum oxide; and / or

[0022] The carbonyl iron powder is micron-sized spherical carbonyl iron powder.

[0023] Furthermore, in the electrical preparation method, the particle size of the carbonyl iron powder is 3 to 8 microns, and the particle size of the dielectric material is 5 to 100 nanometers.

[0024] The present application also proposes a composite wave-absorbing material, and the secondary battery is obtained by processing the above method.

[0025] Compared with the prior art, the embodiments of the present application have the following advantages:

[0026] In the embodiment of the present application, in the preparation method of the composite absorbing material provided, carbonyl iron powder and dielectric material are mixed to form a mixture, and then the mixture is placed in a coating tank body, and in a protective gas atmosphere, the mixture is subjected to a hot pressing treatment using a hammer head in the coating tank body to coat the dielectric material on the surface of the carbonyl iron powder to obtain a composite absorbing material; wherein, the hammer head can move relative to the coating tank body. The pressing treatment by physical heating and hammering forms a micro-area high temperature on the surface of the carbonyl iron powder. Not only is the process simple, but the dielectric material can be adsorbed on the surface of the carbonyl iron powder to achieve a similar "welding effect", so that the dielectric material and the carbonyl iron powder are more strongly bonded. Therefore, this method can effectively alleviate the problem that the existing SiO2 coating formed on the surface of the carbonyl iron powder is complex in process and has weak interface bonding, resulting in the coating layer being easy to peel off.

[0027] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic flow chart of a method for preparing a composite absorbing material provided in an embodiment of the present application;

[0029] Figure 2 This is a schematic diagram of the structure of the coated tank provided in an embodiment of the present application;

[0030] Figure 3 is a scanning electron microscope image of the original spherical carbonyl iron powder;

[0031] Figure 4 is a scanning electron microscope image of the composite absorbing material in Example 2 of the present application;

[0032] Figure 5 is a scanning electron microscope image of the composite absorbing material in Example 3 of the present application;

[0033] Figure 6 This is a graph showing the microwave absorption performance when the carbonyl iron content in the original spherical carbonyl iron powder is 40% by weight;

[0034] Figure 7 This is a graph showing the absorbing performance of the composite absorbing material of Example 2 of the present application when the content is 40% by weight;

[0035] Figure 8 This is a graph showing the microwave absorption performance of the original spherical carbonyl iron powder when its content is 60% by weight;

[0036] Figure 9 This is a graph showing the absorbing performance of the composite absorbing material of Example 2 of the present application when the content is 60% by weight. DETAILED DESCRIPTION

[0037] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0038] Carbonyl iron powder has become an important candidate for high-performance absorbers due to its high saturation magnetization, excellent magnetic permeability, and temperature stability. In particular, flake carbonyl iron powder can break through the Snoek limit by enhancing the anisotropy field, further improving magnetic permeability and resonant frequency. However, its application is still limited by the following problems: (1) Low resistivity leads to a high complex dielectric constant, which is mismatched with the complex magnetic permeability and exacerbates electromagnetic wave reflection; (2) It is easily oxidized at high temperatures, causing magnetic properties to degrade; and (3) Conductive networks are easily formed between particles, exacerbating dielectric loss.

[0039] The applicant of this application found that the existing technology mostly uses SiO2 coating modification to isolate oxidation and reduce the dielectric constant, but the traditional method (such as the sol-gel method) has significant defects: (1) the process is complicated, requiring multiple steps of hydrolysis and calcination, and high energy consumption; (2) the coating layer has poor uniformity, and is prone to local exposure or SiO agglomeration; (3) the interface bonding is weak, and the coating layer is easy to peel off.

[0040] In order to solve the above problems, the present invention provides a method for preparing a composite absorbing material. Figure 1 As shown, it includes steps 101 to 102:

[0041] Step 101: Mix carbonyl iron powder and dielectric material to form a mixture.

[0042] In step 101, the dielectric material is a material that can adjust the electromagnetic parameters of the carbonyl iron powder, improve impedance matching and attenuation characteristics, and enhance the overall performance of the carbonyl iron powder. Alternatively, in one embodiment, the dielectric material can be at least one of nano-sized silicon oxide and nano-sized aluminum oxide.

[0043] In the above step 101, the carbonyl iron powder is micron-sized spherical carbonyl iron powder, which facilitates the dielectric material to be evenly coated on the surface of the spherical carbonyl iron powder by hot pressing.

[0044] In the above step 101, the carbonyl iron powder and the dielectric material are evenly mixed to form a mixture by stirring, rotating, etc., so that the dielectric material can be evenly distributed around the carbonyl iron powder, so that after subsequent hot pressing treatment, the dielectric material can be evenly coated on the surface of the carbonyl iron powder.

[0045] Optionally, the particle size of the carbonyl iron powder can be 3 to 8 microns, for example, one or any two of 3 microns, 4 microns, 5 microns, 6 microns, 7 microns, and 8 microns, and the particle size of the dielectric material can be 5 to 100 nanometers, for example, one or any two of 5 nanometers, 10 nanometers, 20 nanometers, 50 nanometers, 80 nanometers, and 100 nanometers, so as to effectively form a dielectric thin layer on the surface of the carbonyl iron powder.

[0046] Step 102: placing the mixture in a coating tank, and performing a hot pressing process on the mixture using a hammer in the coating tank in a protective gas atmosphere to coat the dielectric material on the surface of the carbonyl iron powder to obtain a composite absorbing material; wherein the hammer can move relative to the coating tank.

[0047] In the above step 102, the protective gas may be high-purity argon or nitrogen, etc., which can effectively isolate oxygen and prevent the carbonyl iron powder from being oxidized during the hot pressing process.

[0048] In the above step 102, under the protection of the protective gas, the mixture is subjected to a heat-pressing and pressing treatment by the hammering action of the hammer head. Since the mixture is placed in the coating tank body and the hammer head can move relative to the coating tank body, the physical heating of the mixture and the pressing treatment by the hammering of the hammer head can form a micro-area high temperature on the surface of the carbonyl iron powder. At the same time, the dielectric material can be adsorbed on the surface of the carbonyl iron powder by the pressing action, achieving a similar "welding effect", so that the dielectric material and the carbonyl iron powder are more strongly combined to coat the dielectric material on the surface of the carbonyl iron powder to obtain a composite absorbing material.

[0049] Alternatively, in one embodiment, Figure 2 As shown, the hammer head 12 is rotatably arranged in the coating tank body 11, and there is a gap between the hammer head 12 and the inner wall of the coating tank body 11; by controlling the rotation of the coating tank body 11 or the hammer head 12, the hammer head 12 can rotate relative to the coating tank body 11 and hammer the mixture in the coating tank body 11, thereby realizing hot pressing treatment of the mixture.

[0050] In this embodiment, because the hammer head is rotatably arranged in the coating tank body, and there is a gap between the hammer head and the inner wall of the coating tank body, under heating conditions, the coating tank body or the hammer head is controlled to rotate, so that the hammer head can rotate relative to the coating tank body and hammer the mixture in the coating tank body, thereby achieving dry compression of the mixture and controlling the rolling of the mixture, forming micro-area high temperature on the surface of the carbonyl iron powder, and being able to adsorb the dielectric material on the surface of the carbonyl iron powder by cold welding, thereby achieving uniform dry coating of the surface of the carbonyl iron powder by the dielectric material particles, which not only improves the oxidation resistance of the carbonyl iron powder, but also the dielectric material as an insulator can effectively prevent the formation of a conductive loop between the carbonyl iron powder particles, thereby effectively reducing its dielectric constant.

[0051] In this specific embodiment, a hammer head that can rotate relative to the coating tank body is provided in the coating tank body. After the mixture is placed in the coating tank body, the rotation of the coating tank body itself or the rotation of the hammer head is controlled so that the hammer head can rotate at high speed along the inside of the coating tank body. The hammer head with a curved surface will compress the powder between itself and the tank wall, thereby driving the powder to roll along the tank wall, so that the mixture can be compressed and rolled along the wall at high speed in a dry method, thereby realizing uniform dry coating of the surface of the carbonyl iron powder by the dielectric material particles.

[0052] In this specific embodiment, the dielectric material particles can be uniformly coated on the surface of the carbonyl iron powder simply by using the coating tank 11 with the hammer head 12. It has low cost, simple preparation process, and is easy to achieve large-scale industrial production.

[0053] Optionally, in a specific embodiment, during the hot pressing process, the temperature of the coated can body is controlled to be 100° C. to 200° C., and the rotation speed of the coated can body is controlled to be 2500 rpm to 3500 rpm for 10 minutes to 30 minutes.

[0054] In this specific embodiment, the temperature is controlled at 100°C to 200°C and the rotation speed is 2500 rpm to 3500 rpm, which can not only effectively form micro-region high temperature for dielectric material adsorption, but also avoid oxygen contamination caused by high temperature; under the above temperature and rotation speed conditions, the dielectric material can be wrapped around the surface of the carbonyl iron powder in 10 minutes to 30 minutes.

[0055] Optionally, during the hot pressing process, the temperature can be one of 100°C, 110°C, 150°C, 180°C, 200°C or any two of the range values, the rotation speed can be one of 2500 rpm, 2600 rpm, 2800 rpm, 3000 rpm, 3500 rpm or any two of the range values, and the pressing time can be one of 10 minutes, 12 minutes, 15 minutes, 20 minutes, 3 minutes or any two of the range values.

[0056] Alternatively, in one embodiment, Figure 2As shown, a scraper 13 is also provided in the coating tank 11. A mixture 20 of the dielectric material for the coating layer and the coated carbonyl iron powder is placed in the coating tank 11. By controlling the rotation of the coating tank 11, the hammer head 12 rotates at high speed relative to the coating tank 11, thereby compressing the mixed material powder in the tank to achieve coating. That is, as the hammer head 12 rotates at high speed along the interior of the coating tank 11, the hammer head 12 with a curved surface compresses the powder between itself and the tank wall, driving the powder to roll along the tank wall, thereby achieving uniform coating of the carbonyl iron powder surface with the nano-dielectric material particles without destroying the structure of the carbonyl iron particles themselves. Moreover, because it is a purely physical dry coating method, its process flow is particularly simple, avoiding the problems of secondary pollution and corrosion of carbonyl iron powder caused by wet coating.

[0057] The scraper 13 is relatively fixed to the hammer 12 so that the scraper 13 can rotate at high speed closely with the hammer 12 to remove the powder material adhering to the tank wall in preparation for the next compression and rolling process of the hammer 12 on the powder material.

[0058] In this specific embodiment, the above-mentioned can covering equipment further has a heating component (not shown), which can be a heating rod, etc., which can heat the inside of the covered can.

[0059] Optionally, in a specific embodiment, the gap between the hammer head 12 and the inner wall of the coating tank body 11 is 0.1 mm to 1 mm, which can match the size of the carbonyl iron powder and the dielectric material in the mixture, and can apply pressure to compress the mixture without over-extruding the material and destroying the overall structure of the carbonyl iron powder.

[0060] The preparation method provided in the embodiment of the present application comprises mixing carbonyl iron powder with a dielectric material, and then subjecting the mixture to a hot pressing treatment in a protective gas atmosphere to coat the dielectric material on the surface of the carbonyl iron powder to obtain a composite absorbing material; wherein, the pressing treatment is performed by physical heating and hammering to form a micro-area high temperature on the surface of the carbonyl iron powder. This not only simplifies the process, but also enables the dielectric material to be adsorbed on the surface of the carbonyl iron powder by cold welding, achieving a similar "welding effect", so that the dielectric material and the carbonyl iron powder are more strongly bonded. Therefore, this method can effectively alleviate the problem that the existing SiO2 coating formed on the surface of the carbonyl iron powder is complex in process and has weak interface bonding, resulting in the coating being easy to peel off.

[0061] Optionally, in one embodiment, the preparation method provided in the examples of the present application, before mixing the carbonyl iron powder with the dielectric material, further comprises:

[0062] The carbonyl iron powder is subjected to annealing treatment.

[0063] In this embodiment, the carbonyl iron powder is annealed separately before being mixed with the dielectric material, which can improve the ductility of the carbonyl iron powder and reduce its hardness, making it easier to adsorb the dielectric material on the surface of the carbonyl iron powder by subsequent hot pressing.

[0064] Optionally, in a specific embodiment, the carbonyl iron powder is subjected to annealing treatment, comprising:

[0065] Heat to 300-550℃ in a protective gas atmosphere for 3-5h, then cool to room temperature before discharging.

[0066] In this specific embodiment, heat treating the carbonyl iron powder at a temperature of 300-550° C. for 3-5 hours in a protective gas atmosphere can not only effectively improve the ductility of the material and reduce its hardness, but also avoid affecting the overall magnetic effect of the material due to high temperature.

[0067] Optionally, in one embodiment, the preparation method provided in the embodiment of the present application further comprises, before the mixture is subjected to a hot pressing treatment using the hammer in the coating tank:

[0068] The mixture is kept warm at 100° C. to 200° C. for 1 to 20 minutes.

[0069] In this embodiment, before the hot pressing process, the coated tank body is first evacuated and a protective gas such as high-purity argon is introduced to remove the air inside the tank. At the same time, the heating rod in the center of the tank body is started to 100°C to 200°C and kept warm for 10 minutes to further soften the material and avoid oxygen contamination caused by high temperature that affects the overall performance of the material.

[0070] Optionally, in one embodiment, the mixture further comprises a pressing aid, and the pressing aid is selected from at least one of polyethylene glycol, a silane coupling agent, and calcium stearate.

[0071] In this embodiment, by adding the above-mentioned pressing aid to the mixture, the pressing aid has a lubricating effect and can also enhance the bonding strength between the interface dielectric material and the carbonyl iron powder, while preventing the hot pressing from exerting too much force on the carbonyl iron powder, and has a buffering and protective effect on the carbonyl iron powder, so that the dielectric material can be more easily and evenly coated on the surface of the carbonyl iron powder.

[0072] Alternatively, in one embodiment, carbonyl iron powder is mixed with a dielectric material, comprising:

[0073] The dielectric material and the grinding aid are mixed with the carbonyl iron powder according to the mass percentage of the dielectric material to the carbonyl iron powder being 1% to 8% and the mass percentage of the grinding aid to the carbonyl iron powder being 1% to 5%.

[0074] In this embodiment, the dielectric material is added in an amount of 1% to 8% by mass of the carbonyl iron powder, which can not only uniformly coat the carbonyl iron powder but also avoid magnetic loss caused by an overly thick coating layer.

[0075] In this embodiment, the grinding aid is added at a mass percentage of 1% to 5% of the carbonyl iron powder, which can effectively assist in the grinding of the carbonyl iron powder and the dielectric material without affecting the function of the dielectric material.

[0076] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0077] (1) The hot pressing coating is carried out by hammer grinding equipment, which is a pure physical dry particle fusion coating process. The required preparation equipment is simple in principle, the process flow is simple, the cost is low, it is environmentally friendly, and it is easy to scale up production capacity;

[0078] (2) The dry particle fusion coating method can achieve uniform coating of the surface of micron-shaped spherical carbonyl iron powder with nano-dielectric material particles without using solvents and without pre-dispersing the powder, even if the powder to be treated has obvious agglomeration problems;

[0079] (3) The composite absorbing material formed by hot pressing has significantly improved anti-oxidation performance; compared with the uncoated carbonyl iron, the dielectric constant and impedance matching of the composite absorbing material are significantly improved, and the absorbing performance is significantly improved.

[0080] The present application also proposes a composite absorbing material, wherein the composite absorbing material is obtained by processing using the above method.

[0081] For the above composite absorbing material embodiment, the above composite absorbing material is obtained by the above method and can achieve the same technical effect. To avoid repetition, it will not be described here. For relevant details, please refer to the partial description of the method embodiment.

[0082] The present application is described in detail below through examples.

[0083] Performance testing methods

[0084] (1) Electromagnetic performance test:

[0085] The composite absorbing material sample was uniformly mixed with paraffin wax in a mass ratio of 3:7 and then pressed into a standard coaxial ring sample (outer diameter 7.00 mm, inner diameter 3.04 mm, thickness 2 mm). The reflection loss (RL) performance was measured in the 2-18 GHz frequency band using a Keysight N5224B vector network analyzer. The sample was installed in a coaxial test fixture and the system was calibrated using the free-space calibration method. The electromagnetic properties were measured to obtain the dielectric constant, permeability, frequency point, and absorbing performance.

[0086] Example 1

[0087] (1) placing micron-sized spherical carbonyl iron powder in a vacuum furnace and introducing inert gas, annealing at 300°C for 3 hours;

[0088] (2) The annealed spherical carbonyl iron powder is uniformly mixed with 1% by mass of the dielectric material nano-SiO2 and placed in a coating tank, and polyethylene glycol accounting for 1% by mass of the carbonyl iron powder is added to the powder; the coating tank is sealed, and the coating tank is evacuated and argon gas is introduced into the coating tank, and then the heating rod is started to heat the powder in the coating tank to 100°C and keep it warm for 10 minutes; then the coating tank is started to rotate at high speed, and the speed of the coating tank is controlled to 2500 rpm. The coating time is 10 minutes, and a composite absorbing material with spherical carbonyl iron powder uniformly coated with nano-SiO2 is prepared under dry conditions.

[0089] Example 2

[0090] (1) placing micron-sized spherical carbonyl iron powder in a vacuum furnace and introducing inert gas, annealing at 450°C for 4 hours;

[0091] (2) The annealed spherical carbonyl iron powder is uniformly mixed with 3% by mass of the dielectric material nano-SiO2 and placed in a coating tank, and polyethylene glycol accounting for 2% by mass of the carbonyl iron powder and a silane coupling agent accounting for 2% by mass of the carbonyl iron powder are added to the powder; the coating tank is sealed, and argon gas is introduced into the coating tank after vacuuming the coating tank, and then the heating rod is started to heat the powder in the coating tank to 150°C and keep it warm for 10 minutes; then the coating tank is started to rotate at high speed, and the speed of the coating tank is controlled to 3000 rpm. The coating time is 15 minutes, and a composite absorbing material with spherical carbonyl iron powder uniformly coated with nano-SiO2 is prepared under dry conditions.

[0092] Example 3

[0093] (1) placing micron-sized spherical carbonyl iron powder in a vacuum furnace and introducing inert gas, annealing at 500°C for 5 hours;

[0094] (2) The annealed spherical carbonyl iron powder is uniformly mixed with 5% by mass of the dielectric material nano-SiO2 and placed in a coating tank, and polyethylene glycol accounting for 1% by mass of the carbonyl iron powder, a silane coupling agent accounting for 2% by mass of the carbonyl iron powder, and calcium stearate accounting for 1% by mass of the carbonyl iron powder are added to the powder; the coating tank is sealed, and the coating tank is evacuated and argon gas is introduced, and then the heating rod is started to heat the powder in the coating tank to 200°C and keep it warm for 20 minutes; then the coating tank is started to rotate at high speed, and the speed of the coating tank is controlled to 3500 rpm. The coating time is 30 minutes, and a composite absorbing material with spherical carbonyl iron powder uniformly coated with nano-SiO2 is prepared under dry conditions.

[0095] Example 4

[0096] (1) placing micron-sized spherical carbonyl iron powder in a vacuum furnace and introducing inert gas, annealing at 550°C for 3 hours;

[0097] (2) The annealed spherical carbonyl iron powder is uniformly mixed with 8% by mass of the dielectric material nano-SiO2 and placed in a coating tank, and polyethylene glycol accounting for 2% by mass of the carbonyl iron powder and a silane coupling agent accounting for 1% by mass of the carbonyl iron powder are added to the powder; the coating tank is sealed, and the coating tank is evacuated and argon gas is introduced into the coating tank, and then the heating rod is started to heat the powder in the coating tank to 160°C and keep it warm for 10 minutes; then the coating tank is started to rotate at high speed, and the speed of the coating tank is controlled to 3200 rpm. The coating time is 20 minutes, and a composite absorbing material with spherical carbonyl iron powder uniformly coated with nano-SiO2 is prepared under dry conditions.

[0098] Example 5

[0099] (1) placing micron-sized spherical carbonyl iron powder in a vacuum furnace and introducing inert gas, annealing at 500°C for 3 hours;

[0100] (2) The annealed spherical carbonyl iron powder is uniformly mixed with 3% by mass of the dielectric material nano-SiO2 and placed in a coating tank, and polyethylene glycol accounting for 3% by mass of the carbonyl iron powder is added to the powder; the coating tank is sealed, and the coating tank is evacuated and argon gas is introduced into the coating tank, and then the heating rod is started to heat the powder in the coating tank to 160°C and keep it warm for 10 minutes; then the coating tank is started to rotate at high speed, and the speed of the coating tank is controlled to 3200 rpm. The coating time is 20 minutes, and a composite absorbing material with spherical carbonyl iron powder uniformly coated with nano-SiO2 is prepared under dry conditions.

[0101] Example 6

[0102] (1) placing micron-sized spherical carbonyl iron powder in a vacuum furnace and introducing inert gas, annealing at 500°C for 3 hours;

[0103] (2) The annealed spherical carbonyl iron powder is uniformly mixed with 3% by mass of the dielectric material nano-SiO2 and placed in a coating tank, and polyethylene glycol accounting for 2% by mass of the carbonyl iron powder and calcium stearate accounting for 2% by mass of the carbonyl iron powder are added to the powder; the coating tank is sealed, and the coating tank is evacuated and argon gas is introduced into the coating tank, and then the heating rod is started to heat the powder in the coating tank to 160°C and keep it warm for 10 minutes; then the coating tank is started to rotate at high speed, and the speed of the coating tank is controlled to 3200 rpm. The coating time is 20 minutes, and a composite absorbing material with spherical carbonyl iron powder uniformly coated with nano-SiO2 is prepared under dry conditions.

[0104] Example 7

[0105] (1) placing micron-sized spherical carbonyl iron powder in a vacuum furnace and introducing inert gas, annealing at 450°C for 4 hours;

[0106] (2) The annealed spherical carbonyl iron powder is uniformly mixed with 3% by mass of the dielectric material nano-Al2O3 and placed in a coating tank, and polyethylene glycol accounting for 2% by mass of the carbonyl iron powder and a silane coupling agent accounting for 2% by mass of the carbonyl iron powder are added to the powder; the coating tank is sealed, and the coating tank is evacuated and argon gas is introduced into the coating tank, and then the heating rod is started to heat the powder in the coating tank to 150°C and keep the temperature for 10 minutes; then the coating tank is started to rotate at high speed, and the speed of the coating tank is controlled to 3000 rpm. The coating time is 15 minutes, and a composite absorbing material with spherical carbonyl iron powder uniformly coated with nano-Al2O3 is prepared under dry conditions.

[0107] Example 8

[0108] Spherical carbonyl iron powder that has not been annealed is evenly mixed with 3% by mass of dielectric material nano-SiO2 and placed in a coating tank, and polyethylene glycol accounting for 2% by mass of the carbonyl iron powder and a silane coupling agent accounting for 2% by mass of the carbonyl iron powder are added to the powder; the coating tank is sealed, evacuated and then introduced with argon gas, and then a heating rod is started to heat the powder in the coating tank to 150°C and keep the temperature for 10 minutes; then the coating tank is started to rotate at high speed, the speed of the coating tank is controlled to 3000 rpm, and the coating time is 15 minutes, thereby preparing a composite absorbing material with spherical carbonyl iron powder evenly coated with nano-SiO2 under dry conditions.

[0109] The control parameters of each embodiment are shown in Table 1.

[0110] The original spherical carbonyl iron powder and the composite absorbing materials prepared in Example 2 and Example 3 were respectively subjected to scanning electron microscopy. The scanning electron microscopy results of the original spherical carbonyl iron powder and the composite absorbing materials in Example 2 and Example 3 are as follows: Figures 3-5 shown.

[0111] The results show that the composite absorbing material produced by the embodiment of the present application is surface-welded and embedded with dielectric material.

[0112] The composite absorbing materials prepared in each embodiment were subjected to electromagnetic performance tests, and the test data are shown in Table 1.

[0113] The absorption performance diagrams of the original spherical carbonyl iron powder and the composite absorbing material in Example 2 when the content is 40% by weight are shown as follows: Figures 6-7 shown.

[0114] The absorption performance diagrams of the original spherical carbonyl iron powder and the composite absorbing material in Example 2 when the content is 60% by weight are shown as follows: Figures 8-9 shown.

[0115] Table 1

[0116]

[0117]

[0118] Where εˊ represents the real part of the dielectric constant and μˊ represents the real part of the magnetic permeability.

[0119] From the test results in Table 1, it can be seen that compared with the uncoated carbonyl iron, the composite absorbing material prepared in the embodiment of the present application has significantly improved electromagnetic and microwave absorption performance, significantly improved dielectric constant and impedance matching, and significantly improved absorbing performance.

[0120] To sum up, in this embodiment, carbonyl iron powder and dielectric material are mixed to form a mixture, and then the mixture is placed in a coating tank, and in a protective gas atmosphere, the mixture is hot pressed using a hammer in the coating tank to coat the dielectric material on the surface of the carbonyl iron powder to obtain a composite absorbing material; wherein, micro-area high temperature is formed on the surface of the carbonyl iron powder through physical heating and hammering pressing treatment, which not only has a simple process, but also can adsorb the dielectric material on the surface of the carbonyl iron powder to achieve a similar "welding effect", so that the dielectric material and the carbonyl iron powder are more strongly bonded, so this method can effectively alleviate the problem that the existing SiO2 coating formed on the surface of the carbonyl iron powder is complex in process and the interface bonding is weak, which makes the coating layer easy to peel off.

[0121] Although preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they become aware of the basic inventive concepts. Therefore, the claims are intended to include the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0122] The above is a detailed introduction to a composite absorbing material and its preparation method provided by the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only intended to help understand the method and core concept of the present application. At the same time, for those skilled in the art, based on the concept of the present application, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present application.

Claims

1. A method for preparing a composite absorbing material, characterized in that: include: mixing carbonyl iron powder with a dielectric material to form a mixture; The mixed material is placed in a coating tank body, and in a protective gas atmosphere, the mixed material is subjected to a hot pressing treatment using a hammer head in the coating tank body to coat the dielectric material on the surface of the carbonyl iron powder to obtain a composite absorbing material; wherein the hammer head can move relative to the coating tank body.

2. The preparation method according to claim 1, characterized in that The hammer head is rotatably arranged in the coating tank body, and there is a gap between the hammer head and the inner wall of the coating tank body; by controlling the rotation of the coating tank body or the hammer head, the hammer head can be rotated relative to the coating tank body and hammer the mixture in the coating tank body, thereby realizing hot pressing treatment of the mixture.

3. The preparation method according to claim 2, characterized in that During the hot pressing process, the temperature of the coated can body is controlled to be 100° C. to 200° C., and the rotation speed of the coated can body is controlled to be 2500 rpm to 3500 rpm for 10 minutes to 30 minutes.

4. The preparation method according to claim 1 or 2, characterized in that The gap between the hammer head and the inner wall of the coating tank body is 0.1mm to 1mm.

5. The preparation method according to claim 1, characterized in that Before the mixed material is subjected to a hot pressing process by the hammer in the coating tank, the method further comprises: The mixture is kept warm at 100° C. to 200° C. for 1 to 20 minutes.

6. The preparation method according to claim 1, characterized in that Before mixing the carbonyl iron powder with the dielectric material, it also includes: The carbonyl iron powder is subjected to annealing treatment.

7. The preparation method according to claim 6, characterized in that Annealing the carbonyl iron powder comprises: In a protective gas atmosphere, the temperature is raised to 300-550°C for heat treatment for 3-5 hours, and then lowered to 20-30°C before discharging.

8. The preparation method according to claim 1, characterized in that The mixture further comprises a pressing aid, which is selected from at least one of polyethylene glycol, a silane coupling agent, and calcium stearate.

9. The preparation method according to claim 8, characterized in that Mix the carbonyl iron powder with dielectric materials, including: The dielectric material and the grinding aid are mixed with the carbonyl iron powder according to the mass percentage of the dielectric material to the carbonyl iron powder being 1% to 8% and the mass percentage of the grinding aid to the carbonyl iron powder being 1% to 5%.

10. The preparation method according to any one of claims 1 to 8, characterized in that: The dielectric material is at least one of nano-scale silicon oxide and nano-scale aluminum oxide; and / or The carbonyl iron powder is micron-sized spherical carbonyl iron powder.

11. A composite absorbing material, characterized in that: The composite absorbing material is obtained by processing according to any one of claims 1 to 10.

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