Carbonyl iron powder-graphite electromagnetic wave absorption composite material and preparation and application thereof

Abstract

The invention discloses a carbonyl iron powder-graphite electromagnetic wave absorption composite material and a preparation method thereof. The carbonyl iron powder-graphite electromagnetic wave absorption composite material is composed of superfine spherical carbonyl iron powder and flake graphite. According to the method for preparing the carbonyl iron powder-graphite electromagnetic wave absorbing composite material, a room-temperature dry ball milling technology is utilized, various carbonyl iron powder-carbon composite wave absorbing materials can be flexibly prepared, the preparation process is simple, the condition is mild, consumed time is short, use of a large amount of solvent is avoided, and the method is economical and environmentally friendly. According to the method for preparing the carbonyl iron powder-graphite electromagnetic wave absorption composite material, cheap carbonyl iron powder and flake graphite are adopted as raw materials, the raw materials are cheap and easy to obtain, and the method is suitable for actual industrial application. The carbonyl iron powder-graphite electromagnetic wave absorption composite material provided by the invention has large reflection loss and absorption bandwidth under the condition of low thickness, and can effectively absorb electromagnetic waves.

Description

Technical Field

[0001] The present invention relates to a carbonyl iron powder-graphite electromagnetic wave absorbing composite material and its preparation and application. Background Art

[0002] Electromagnetic radiation can have an adverse impact on human health. Electromagnetic radiation can affect the normal operation of electronic instruments and precision equipment. Some devices need to reduce the reflection of electromagnetic waves to improve the survival probability in an electromagnetic radiation environment. Electromagnetic wave absorbing materials can be used to solve the above problems. Electromagnetic wave absorbing materials with light weight, effective absorption bandwidth, high absorption intensity, and thin thickness will have a wider range of application scenarios.

[0003] Carbonyl iron powder has the advantages of good thermal stability, high magnetic permeability, and low price, and has been widely used in the preparation of wave-absorbing materials. However, common carbonyl iron powders usually have a low complex permittivity, poor impedance matching with the natural space, too strong reflection of electromagnetic waves, and mostly have problems of low overall electromagnetic loss performance and too narrow effective absorption bandwidth, and cannot meet the use requirements of wave-absorbing materials for achieving high attenuation in each wave band. At present, the research on improving the wave-absorbing performance of carbonyl iron powder mostly focuses on morphology control and coating modification, etc. However, these preparation methods often involve high-temperature calcination, use of highly acidic or alkaline solutions and flammable gases, as well as multi-step processing, etc., which are complex, energy-consuming, time-consuming, and dangerous, and the regulation of electromagnetic parameters and performance of materials during the synthesis process is poor. In addition, the prepared carbonyl iron powder wave-absorbing materials often also have disadvantages such as high density and large mass, which also limit their large-scale manufacturing and commercial applications. Summary of the Invention

[0004] In order to further optimize the performance of electromagnetic wave absorbing materials and enrich the selection space of electromagnetic wave absorbing materials, the present invention is made.

[0005] An embodiment of the present invention provides a carbonyl iron powder-graphite electromagnetic wave absorbing composite material. Its preparation method uses ultrafine carbonyl iron powder and light and inexpensive flaky graphite as raw materials, and combines subsequent dry, non-solvent, non-high-temperature ball milling technology, and can prepare a high-performance light-weight carbonyl iron powder-graphite electromagnetic wave absorbing composite material with strong absorption and broadband response at room temperature, avoiding the disadvantages of high energy consumption, high cost, high density, complex steps, low wave-absorbing efficiency, and poor repeatability of the prior art.

[0006] As an aspect of the present invention, it relates to a method for preparing a carbonyl iron powder-graphite electromagnetic wave absorbing composite material, and the method includes:

[0007] (1) Mix ultrafine spherical carbonyl iron powder and flaky graphite in a mass ratio of 1-8:1 to obtain a carbonyl iron powder-graphite composite pre-powder; the particle size of the ultrafine spherical carbonyl iron powder is 0.5-3 μm;

[0008] (2) Use a ball mill to perform dry ball milling on the carbonyl iron powder-graphite composite pre-powder at room temperature to obtain a carbonyl iron powder-graphite composite wave-absorbing material; the grinding balls of the ball mill are composed of three kinds of grinding balls with diameters of 12-15 mm, 9-10 mm, and 3-6 mm with a mass ratio of 20:50:30. The ball-to-material mass ratio of the ball mill is 1-10:1, the rotation speed of the ball mill is 50-500 r / min, and the ball milling time of the ball mill is 3-72 h.

[0009] In a specific implementable manner, in step (1), the method for preparing the ultrafine spherical carbonyl iron powder is: use an ultrasonic vibrating screen to screen the original carbonyl iron powder at room temperature.

[0010] In a specific implementable manner, in step (1), the mass ratio of the ultrafine spherical carbonyl iron powder to the flaky graphite is 2-8:1; preferably 4-7:1; more preferably 4-6:1.

[0011] In a specific implementable manner, in step (2), the ball-to-material mass ratio of the ball mill is 1-9:1, the rotation speed of the ball mill is 100-500 r / min, and the ball milling time of the ball mill is 6-72 h.

[0012] In a specific implementable manner, in step (2), the ball-to-material mass ratio of the ball mill is 2-6:1, the rotation speed of the ball mill is 200-500 r / min, and the ball milling time of the ball mill is 36-60 h.

[0013] In a specific implementable manner, in step (2), the ball-to-material mass ratio of the ball mill is 3-6:1, the rotation speed of the ball mill is 300-500 r / min, and the ball milling time of the ball mill is 36-48 h.

[0014] As another aspect of the present invention, it relates to a carbonyl iron powder-graphite electromagnetic wave absorption composite material prepared by the above method.

[0015] As still another aspect of the present invention, it relates to the application of the above carbonyl iron powder-graphite electromagnetic wave absorption composite material in wave-absorbing devices.

[0016] The minimum reflection loss value of the carbonyl iron powder-graphite composite wave-absorbing material provided by the present invention is -48 dB, and the effective absorption bandwidth can reach 8.10 GHz, realizing "strong" absorption and "wide" frequency band response to electromagnetic waves, almost exceeding the absorption performance of current commercial carbonyl iron powder, and having good application prospects.

[0017] Compared with the prior art, the beneficial effects of the present invention at least include:

[0018] 1. Compared with the traditional high - energy - consuming high - temperature treatment method, the conditions of the present invention are mild and the time consumption is short.

[0019] 2. The present invention utilizes the room - temperature dry ball - milling technology with non - solvents and non - high - temperatures, and can flexibly prepare a variety of carbonyl iron powder - carbon composite absorbing materials. It avoids the complex processes of traditional methods and the use of a large amount of solvents, reduces the subsequent treatment process, and has the effects of simple preparation process, strong repeatability and controllability, and being economical and environmentally friendly.

[0020] 3. The raw materials used in the present invention are inexpensive carbonyl iron powder and flaky graphite. The raw materials are inexpensive and easily available, the method is green and environmentally friendly, has the potential for industrialization, and is suitable for practical industrial applications.

[0021] 4. The present invention uses the composite of ultrafine spherical carbonyl iron powder and flaky graphite, which can generate a multi - level interface structure, form a good magnetoelectric synergy loss mechanism, has large reflection loss and absorption bandwidth at low thickness, and can effectively absorb 99.99% of electromagnetic waves.

[0022] In summary, compared with the prior art, the present invention uses ultrafine carbonyl iron powder and flaky graphite as raw materials, utilizes the room - temperature dry ball - milling technology with non - solvents and non - high - temperatures, can flexibly prepare a variety of carbonyl iron powder - graphite composite absorbing materials. The preparation raw materials are inexpensive and easily available, the process is simple, the repeatability and controllability are strong, the time consumption is short and it is green and environmentally friendly. The prepared composite material has the characteristics of light weight, wide electromagnetic wave absorption frequency band and large absorption intensity. Brief Description of the Drawings

[0023] The drawings are used to provide a further understanding of the present invention, and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention, and do not constitute a limitation to the present invention. In the drawings:

[0024] Figure 1 It is the reflection loss result diagram of the pure carbonyl iron powder absorbing material prepared in Comparative Example 1;

[0025] Figure 2 It is the reflection loss result diagram of the pure flaky graphite absorbing material prepared in Comparative Example 2;

[0026] Figure 3 It is the reflection loss result diagram of the carbonyl iron powder - graphite composite absorbing material prepared in Comparative Example 3;

[0027] Figure 4 It is the reflection loss result diagram of the carbonyl iron powder - graphite composite absorbing material prepared in Example 1;

[0028] Figure 5 It is the reflection loss result diagram of the carbonyl iron powder - graphite composite absorbing material prepared in Example 2;

[0029] Figure 6Reflection loss result diagram of the carbonyl iron powder-graphite composite microwave absorbing material prepared in Example 3;

[0030] Figure 7 Reflection loss result diagram of the carbonyl iron powder-graphite composite microwave absorbing material prepared in Example 4.

[0031] Figure 8 Reflection loss result diagram of the carbonyl iron powder-graphite composite microwave absorbing material prepared in Example 5;

[0032] Figure 9 Reflection loss result diagram of the carbonyl iron powder-graphite composite microwave absorbing material prepared in Example 6;

[0033] Figure 10 X-ray diffraction pattern of the carbonyl iron powder-graphite composite microwave absorbing material prepared in Example 6;

[0034] Figure 11 Scanning electron microscope image of the carbonyl iron powder-graphite composite microwave absorbing material prepared in Example 6;

[0035] Figure 12 Reflection loss result diagram of the carbonyl iron powder-graphite composite microwave absorbing material prepared in Comparative Example 7;

[0036] Figure 13 Reflection loss result diagram of the carbonyl iron powder-graphite composite microwave absorbing material prepared in Comparative Example 8. Detailed implementation manners

[0037] The inventor refers to CN105271437A to prepare a carbonyl iron powder absorbent for low-frequency electromagnetic wave absorbing materials, which can transform the carbonyl iron powder from spherical to flaky, thereby improving its absorption performance in low-frequency electromagnetic waves. However, due to the need for atmosphere (hydrogen) and high-temperature (490-600 °C) reduction treatment in the preparation process, it has disadvantages such as high energy consumption and high cost. In addition, the absorbent still has problems such as high density, narrow absorption bandwidth, and low absorption intensity.

[0038] The inventor refers to CN 112266200A to prepare a carbonyl iron powder absorbent with high magnetic loss. The wet ball milling method is used to transform the spherical carbonyl iron powder into flaky, thereby increasing the magnetic permeability to achieve the purpose of high magnetic loss. However, this method requires a coupling agent, a diluent, and curing treatment (100-110 °C), and involves the use of a large amount of solvents, having disadvantages such as complex process, high cost, and high density of the absorbent.

[0039] The inventor refers to CN116970368A to prepare a low-frequency high-absorption composite microwave absorbing material. This method introduces carboxyl and hydroxyl groups on the surfaces of carbon nanotubes (CNTs) and flaky carbonyl iron powder (CIPs) respectively, and then induces manganese-zinc ferrite (Mn 0.8 Zn0.2 Aggregation growth of Fe2O4) to form a CIPs-Mn 0.8 Zn 0.2 Fe2O4-CNTs ternary composite material, thereby improving its electromagnetic wave absorption performance. However, since the preparation process involves multiple steps and requires highly acidic and alkaline solutions (sodium hydroxide and citric acid) and hydrothermal treatment at high temperature, it has the disadvantages of complex steps, poor repeatability, high energy consumption, and high cost.

[0040] In view of the above, the existing technologies cannot meet the expectations of the inventor. After further research and development, the present invention is made. A lightweight broadband carbonyl iron powder absorbing material is prepared by a simple process, low cost, economical and environmentally friendly method.

[0041] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0042] Comparative Example 1

[0043] A preparation method of a carbonyl iron powder absorbing material includes the following steps:

[0044] Step 1: Use an ultrasonic vibrating screen to screen the original carbonyl iron powder at room temperature. The power of the ultrasonic vibrating screen machine is 1.5 kw, the screen has 3 layers, the ultrasonic treatment is carried out 5 times, each time for 10 minutes, with an interval of 2 minutes; after cooling to room temperature, ultrafine spherical carbonyl iron powder with a particle size of 0.5-3 μm is obtained.

[0045] Step 2: Use a planetary ball mill to carry out dry ball milling of the ultrafine spherical carbonyl iron powder obtained in Step 1 at room temperature without solvent and high temperature: The grinding balls of the planetary ball mill are three kinds of agate balls with diameters of 3, 9, and 12 mm respectively. Among them, the mass ratio of the agate balls with a diameter of 12 mm: the agate balls with a diameter of 9 mm: the agate balls with a diameter of 3 mm is 20:50:30, the ball-to-material mass ratio is 3:1, and positive and reverse two ball milling methods are adopted. The ball milling speed is 500 r / min, and it is intermittent for 5-10 minutes every 1 h, and then reverse ball milling is carried out. After ball milling for 48 h, a carbonyl iron powder absorbing material is obtained.

[0046] Step 3: Mix the carbonyl iron powder absorbing material obtained in Step 2 with paraffin, and carry out coaxial method wave absorption test according to the national standard GJB 2038A-2011. The reflection loss results of the carbonyl iron powder absorbing material prepared in Comparative Example 1 obtained by the test are shown in Figure 1 .

[0047] It can be seen from Figure 1 that the carbonyl iron powder absorbing material of Comparative Example 1 has an absorption bandwidth of 2 GHz only in the high-frequency range (15-17 GHz), and the wave absorption performance is very unsatisfactory. This result shows that even after the ball milling process treatment, the wave absorption performance of pure carbonyl iron powder is still insufficient to meet the actual requirements.

[0048] Comparative Example 2

[0049] A preparation method of a graphite wave-absorbing material, comprising the following steps:

[0050] Step 1: Use a planetary ball mill to perform dry ball milling of flake graphite at room temperature without solvents and high temperatures. The grinding balls of the planetary ball mill are three kinds of agate balls with diameters of 3, 9, and 12 mm respectively. Among them, the mass ratio of agate balls with a diameter of 12 mm: agate balls with a diameter of 9 mm: agate balls with a diameter of 3 mm is 20:50:30, the ball-to-material mass ratio is 3:1, and two ball milling methods of forward and reverse are adopted. The ball milling speed is 500 r / min, with an intermittent period of 5 - 10 minutes every 1 h, and then reverse ball milling. After ball milling for 48 h, a graphite wave-absorbing material is obtained.

[0051] Step 2: Mix the graphite wave-absorbing material obtained in Step 2 with paraffin, and perform coaxial wave-absorbing tests in accordance with the national standard GJB 2038A-2011. The reflection loss results of the graphite wave-absorbing material prepared in Comparative Example 2 obtained by the test are shown in Figure 2 .

[0052] It can be seen from Figure 2 that the pure graphite wave-absorbing material in Comparative Example 2 has almost no loss in the range of 2 - 18 GHz, the absorption bandwidth is 0, and the wave-absorbing performance is very poor. This result also shows that even after being treated by the ball milling process, the wave-absorbing performance of pure graphite cannot meet the actual requirements.

[0053] Comparative Example 3

[0054] A preparation method of a carbonyl iron powder-graphite electromagnetic wave absorption composite material, comprising the following steps:

[0055] Step 1: Use an ultrasonic vibrating screen to screen the original carbonyl iron powder at room temperature. The power of the ultrasonic vibrating screen machine is 1.5 kw, with 3 layers of screens, ultrasonic vibration for 5 times, 10 minutes each time, and an interval of 2 minutes; cool to room temperature to obtain ultrafine spherical carbonyl iron powder with a particle size of 0.5 - 3 μm.

[0056] Step 2: Manually mix the ultrafine spherical carbonyl iron powder obtained in Step 1 with flake graphite according to a mass ratio of 1:1 to obtain a carbonyl iron powder-graphite composite pre-powder;

[0057] Mix the carbonyl iron powder wave-absorbing material obtained in Step 2 with paraffin, and perform coaxial wave-absorbing tests in accordance with the national standard GJB 2038A-2011. The reflection loss results of the carbonyl iron powder-graphite composite wave-absorbing material prepared in Comparative Example 3 obtained by the test are shown in Figure 3 .

[0058] It can be seen from Figure 3It can be seen that when the thickness of the carbonyl iron powder-graphite composite microwave absorption material is 2.10 mm, the effective microwave absorption bandwidth reaches 3.89 GHz, and its microwave absorption performance is improved compared with that of Comparative Example 1 and Comparative Example 2. This result shows that even by manually mixing carbonyl iron powder and graphite, its microwave absorption performance is better than that when used alone.

[0059] Example 1

[0060] A preparation method of a carbonyl iron powder-graphite electromagnetic wave absorption composite material includes the following steps:

[0061] Step 1: Screen the original carbonyl iron powder at room temperature using an ultrasonic vibrating screen. The power of the ultrasonic vibrating screen machine is 1.5 kw, there are 3 layers of screens, ultrasonic treatment is carried out 5 times, 10 minutes each time, with an interval of 2 minutes; after cooling to room temperature, ultrafine spherical carbonyl iron powder with a particle size of 0.5 - 3 μm is obtained.

[0062] Step 2: Mix the ultrafine spherical carbonyl iron powder obtained in Step 1 with flake graphite in a mass ratio of 1:1, and mechanically stir for 10 minutes at a rotation speed of 100 r / min to obtain a carbonyl iron powder-graphite composite pre-powder;

[0063] Step 3: Use a planetary ball mill to carry out non-solvent and non-high-temperature room-temperature dry ball milling on the carbonyl iron powder-graphite composite pre-powder obtained in Step 2: The grinding balls of the planetary ball mill are three kinds of agate balls with diameters of 3, 9, and 12 mm respectively. Among them, the mass ratio of the agate balls with a diameter of 12 mm: the agate balls with a diameter of 9 mm: the agate balls with a diameter of 3 mm is 20:50:30, the ball-to-material mass ratio is 10:1, and positive and reverse ball milling methods are adopted. The ball milling speed is 50 r / min, with an intermittent period of 5 - 10 minutes every 1 h, and then reverse ball milling. After ball milling for 3 h, a carbonyl iron powder-graphite composite microwave absorption material is obtained.

[0064] Mix the carbonyl iron powder microwave absorption material obtained in Step 3 with paraffin, and according to the national standard GJB 2038A-2011, carry out coaxial method microwave absorption testing. The reflection loss results of the carbonyl iron powder-graphite composite microwave absorption material prepared in Example 1 of the present invention obtained by testing are shown in Figure 4 .

[0065] From Figure 4 It can be seen that when the thickness of the carbonyl iron powder-graphite composite microwave absorption material in Example 1 is 1.91 mm, the effective microwave absorption bandwidth reaches 4.71 GHz, and its microwave absorption performance is greatly improved compared with that of Comparative Examples 1 - 3.

[0066] Example 2

[0067] A preparation method of a carbonyl iron powder-graphite electromagnetic wave absorption composite material includes the following steps:

[0068] Step 1: Screen the original carbonyl iron powder at room temperature using an ultrasonic vibrating screen. The power of the ultrasonic vibrating screen machine is 1.5 kw, with 3 layers of screening mesh. Ultrasonic treatment is carried out 5 times, 10 minutes each time, with an interval of 2 minutes. After cooling to room temperature, ultrafine spherical carbonyl iron powder with a particle size of 0.5 - 3 μm is obtained.

[0069] Step 2: Mix the ultrafine spherical carbonyl iron powder obtained in Step 1 with flake graphite in a mass ratio of 2:1, and mechanically stir for 10 minutes at a rotation speed of 100 r / min to obtain carbonyl iron powder - graphite composite pre - powder.

[0070] Step 3: Use a planetary ball mill to carry out dry ball milling of the carbonyl iron powder - graphite composite pre - powder obtained in Step 2 at room temperature without solvent and high temperature. The grinding balls of the planetary ball mill are three kinds of agate balls with diameters of 3, 10, and 12 mm respectively. Among them, the mass ratio of agate balls with a diameter of 12 mm: agate balls with a diameter of 10 mm: agate balls with a diameter of 3 mm is 20:50:30, and the ball - to - material mass ratio is 9:1. Two ball - milling methods, forward and reverse, are adopted, with a ball - milling speed of 100 r / min. Intermittence of 5 - 10 minutes is carried out every 1 h, and then reverse ball - milling is carried out. After ball - milling for 6 h, a carbonyl iron powder - graphite composite wave - absorbing material is obtained.

[0071] Mix the carbonyl iron powder wave - absorbing material obtained in Step 3 with paraffin, and according to the national standard GJB 2038A - 2011, carry out coaxial wave - absorption testing. The reflection loss results of the carbonyl iron powder - graphite composite wave - absorbing material prepared in Example 2 of the present invention obtained by testing are shown in Figure 5 。

[0072] From Figure 5 it can be seen that for the carbonyl iron powder - graphite composite wave - absorbing material of Example 2, when the thickness is only 1.25 mm, the effective wave - absorption bandwidth reaches 5.23 GHz, and its wave - absorption performance is greatly improved compared with Comparative Example 1 and Comparative Example 2. At the same time, compared with Comparative Example 3 (the effective wave - absorption bandwidth is 3.89 GHz), the carbonyl iron powder - graphite composite wave - absorbing material prepared in Example 2 has a wider effective absorption bandwidth.

[0073] Example 3

[0074] A preparation method of a carbonyl iron powder - graphite electromagnetic wave - absorbing composite material, comprising the following steps:

[0075] Step 1: Screen the original carbonyl iron powder at room temperature using an ultrasonic vibrating screen. The power of the ultrasonic vibrating screen machine is 1.5 kw, with 3 layers of screening mesh. Ultrasonic treatment is carried out 5 times, 10 minutes each time, with an interval of 2 minutes. After cooling to room temperature, ultrafine spherical carbonyl iron powder with a particle size of 0.5 - 3 μm is obtained.

[0076] Step 2: Mix the ultrafine spherical carbonyl iron powder obtained in Step 1 with flake graphite at a mass ratio of 3:1, and mechanically stir for 10 minutes at a rotation speed of 100 r / min to obtain a carbonyl iron powder-graphite composite pre-powder;

[0077] Step 3: Use a planetary ball mill to perform room-temperature dry ball milling of the carbonyl iron powder-graphite composite pre-powder obtained in Step 2 without solvent and high temperature: The grinding balls of the planetary ball mill are three kinds of agate balls with diameters of 3, 11, and 12 mm respectively. Among them, the mass ratio of the 12-mm-diameter agate ball: the 11-mm-diameter agate ball: the 3-mm-diameter agate ball is 20:50:30, the ball-to-material mass ratio is 8:1, and two ball milling methods of forward and reverse are adopted. The ball milling speed is 150 r / min, with an intermittent period of 5-10 minutes every 1 h, and then reverse ball milling. After ball milling for 12 h, a carbonyl iron powder-graphite composite wave-absorbing material is obtained.

[0078] Mix the carbonyl iron powder wave-absorbing material obtained in Step 3 with paraffin. According to the national standard GJB 2038A-2011, the reflection loss results of the carbonyl iron powder-graphite composite wave-absorbing material prepared in Example 3 of the present invention are shown in Figure 6 .

[0079] It can be seen from Figure 6 that for the carbonyl iron powder-graphite composite wave-absorbing material of Example 3, when the thickness is 1.87 mm, the effective wave-absorbing bandwidth reaches 6.94 GHz. When the thickness is 2.40 mm, the wave-absorbing bandwidth is 5.89 GHz (8-13.89 GHz), achieving full coverage of the X band, and its wave-absorbing performance is greatly improved compared with Comparative Examples 1-3.

[0080] Example 4

[0081] A preparation method of a carbonyl iron powder-graphite electromagnetic wave absorption composite material, comprising the following steps:

[0082] Step 1: Use an ultrasonic vibrating screen to screen the original carbonyl iron powder at room temperature. The power of the ultrasonic vibrating screen machine is 1.5 kw, with 3 layers of sieve meshes, ultrasonic treatment for 5 times, 10 minutes each time, and an interval of 2 minutes; cool to room temperature and filter to obtain ultrafine spherical carbonyl iron powder with a particle size of 0.5-3 μm.

[0083] Step 2: Mix the ultrafine spherical carbonyl iron powder obtained in Step 1 with flake graphite at a mass ratio of 4:1, and mechanically stir for 10 minutes at a rotation speed of 100 r / min to obtain a carbonyl iron powder-graphite composite pre-powder;

[0084] Step 3: Use a planetary ball mill to perform room-temperature dry ball milling on the carbonyl iron powder-graphite composite pre-powder obtained in Step 2 without using a solvent and at a non-high temperature. The grinding balls of the planetary ball mill are three types of agate balls with diameters of 4, 9, and 12 mm respectively. Among them, the mass ratio of the 12-mm-diameter agate balls: the 9-mm-diameter agate balls: the 4-mm-diameter agate balls is 20:50:30, the ball-to-material mass ratio is 6:1. Use two ball milling methods, forward and reverse. The ball milling speed is 300 r / min, with an intermittent period of 5 - 10 minutes every 1 hour, and then perform reverse ball milling. After ball milling for 36 hours, a carbonyl iron powder-graphite composite absorbing material is obtained.

[0085] Mix the carbonyl iron powder absorbing material obtained in Step 3 with paraffin. According to the national standard GJB 2038A-2011, the reflection loss results of the carbonyl iron powder-graphite composite absorbing material prepared in Example 4 of the present invention are shown in Figure 7 ;

[0086] From Figure 7 it can be seen that when the thickness of the carbonyl iron powder-graphite composite absorbing material in Example 4 is 1.88 mm, the effective absorbing bandwidth reaches 7.55 GHz, and its absorbing performance is greatly improved compared with Comparative Examples 1 - 3.

[0087] Example 5

[0088] A preparation method of a carbonyl iron powder-graphite electromagnetic wave absorbing composite material, comprising the following steps:

[0089] Step 1: Use an ultrasonic vibrating screen to screen the original carbonyl iron powder at room temperature. The power of the ultrasonic vibrating screen machine is 1.5 kw, with 3 layers of sieve meshes. Ultrasonic treatment is performed 5 times, 10 minutes each time, with an interval of 2 minutes; after cooling to room temperature and filtering, ultrafine spherical carbonyl iron powder with a particle size of 0.5 - 3 μm is obtained.

[0090] Step 2: Mix the ultrafine spherical carbonyl iron powder obtained in Step 1 with flaky graphite in a mass ratio of 5:1, and perform mechanical stirring for 10 minutes at a rotation speed of 100 r / min to obtain a carbonyl iron powder-graphite composite pre-powder;

[0091] Step 3: Use a planetary ball mill to perform room-temperature dry ball milling on the carbonyl iron powder-graphite composite pre-powder obtained in Step 2 without using a solvent and at a non-high temperature. The grinding balls of the planetary ball mill are three types of agate balls with diameters of 5, 9, and 12 mm respectively. Among them, the mass ratio of the 12-mm-diameter agate balls: the 9-mm-diameter agate balls: the 5-mm-diameter agate balls is 20:50:30, the ball-to-material mass ratio is 5:1. Use two ball milling methods, forward and reverse. The ball milling speed is 400 r / min, with an intermittent period of 5 - 10 minutes every 1 hour, and then perform reverse ball milling. After ball milling for 42 hours, a carbonyl iron powder-graphite composite absorbing material is obtained.

[0092] Mix the carbonyl iron powder microwave absorption material obtained in Step 3 with paraffin. According to the national standard GJB 2038A-2011, the reflection loss results of the carbonyl iron powder-graphite composite microwave absorption material prepared in Example 5 of the present invention are shown in Figure 8 ; It can be seen from Figure 8 that for the carbonyl iron powder-graphite composite microwave absorption material of Example 5, when the thickness is 1.83 mm, the effective microwave absorption bandwidth reaches 8.03 GHz, and its microwave absorption performance has been greatly improved compared with Comparative Examples 1-3.

[0093] Example 6

[0094] A preparation method of a carbonyl iron powder-graphite electromagnetic wave absorption composite material includes the following steps:

[0095] Step 1: Use an ultrasonic vibrating screen to screen the original carbonyl iron powder at room temperature. The power of the ultrasonic vibrating screen machine is 1.5 kw, with 3 layers of sieve meshes, ultrasonic treatment for 5 times, 10 minutes each time, and an interval of 2 minutes; after cooling to room temperature, filter to obtain ultrafine spherical carbonyl iron powder with a particle size of 0.5-3 μm.

[0096] Step 2: Mix the ultrafine spherical carbonyl iron powder obtained in Step 1 with flaky graphite in a mass ratio of 6:1, and mechanically stir for 10 minutes at a rotation speed of 100 r / min to obtain a carbonyl iron powder-graphite composite pre-powder;

[0097] Step 3: Use a planetary ball mill to perform non-solvent and non-high-temperature room-temperature dry ball milling on the carbonyl iron powder-graphite composite pre-powder obtained in Step 2: The grinding balls of the planetary ball mill are three kinds of agate balls with diameters of 6, 9, and 12 mm respectively. Among them, the mass ratio of the agate balls with a diameter of 12 mm: the agate balls with a diameter of 9 mm: the agate balls with a diameter of 6 mm is 20:50:30, the ball-to-material mass ratio is 3:1, and positive and reverse ball milling methods are adopted. The ball milling speed is 500 r / min, with an intermittent period of 5-10 minutes every 1 h, and then reverse ball milling. After ball milling for 48 h, a carbonyl iron powder-graphite composite microwave absorption material is obtained.

[0098] Mix the carbonyl iron powder microwave absorption material obtained in Step 3 with paraffin. According to the national standard GJB 2038A-2011, the reflection loss results of the carbonyl iron powder-graphite composite microwave absorption material prepared in Example 6 of the present invention are shown in Figure 9 .

[0099] Test the X-ray diffraction pattern of the carbonyl iron powder-graphite composite microwave absorption material prepared in Example 6 of the present invention, and the results are shown in Figure 10 ; Test the scanning electron microscope image of the carbonyl iron powder-graphite composite microwave absorption material prepared in Example 6 of the present invention, and the results are shown in Figure 11 .

[0100] It can be seen from Figure 10It can be seen that in the X-ray diffraction pattern of Example 6, a diffraction peak of graphite appears at 26.7°. At the same time, characteristic diffraction peaks of iron carbonyl are found at 44.5°, 56.7° and 66.3°, which proves the successful combination of the two.

[0101] From Figure 11 the scanning electron microscope image of [], it can be clearly observed that ultrafine spherical iron carbonyl powder with a particle size of 0.5 - 3 μm and flaky graphite are uniformly compounded, further confirming the effective compounding of iron carbonyl powder and graphite under the ball milling process. The spherical iron carbonyl powder loaded on the flaky graphite can produce a multi-level interface structure, obtaining a high dielectric and high magnetic permeability system, resulting in a significant attenuation of the incident electromagnetic wave due to polarization loss. Facilitated by the combined impedance matching of interface polarization and electromagnetic synergy, it is beneficial to excellent microwave absorption performance.

[0102] From Figure 9 It can be seen that when the thickness of the iron carbonyl powder - graphite composite microwave absorption material of Example 6 is 1.75 mm, the effective microwave absorption bandwidth reaches 8.10 GHz, and the minimum reflection loss value is -48 dB. It has a large reflection loss and absorption bandwidth, and can effectively absorb 99.99% of the electromagnetic wave. Its microwave absorption performance has been greatly improved compared with Comparative Examples 1 - 3.

[0103] Example 7

[0104] A preparation method of an iron carbonyl powder - graphite electromagnetic wave absorption composite material includes the following steps:

[0105] Step 1: Use an ultrasonic vibrating screen to screen the original iron carbonyl powder at room temperature. The power of the ultrasonic vibrating screen machine is 1.5 kw, with 3 layers of sieve meshes. Ultrasonic treatment is carried out 5 times, 10 minutes each time, with an interval of 2 minutes; after cooling to room temperature, filtration is carried out to obtain ultrafine spherical iron carbonyl powder with a particle size of 0.5 - 3 μm.

[0106] Step 2: Mix the ultrafine spherical iron carbonyl powder obtained in Step 1 with flaky graphite according to a mass ratio of 7:1, and mechanically stir for 10 minutes at a rotation speed of 100 r / min to obtain an iron carbonyl powder - graphite composite pre-powder;

[0107] Step 3: Use a planetary ball mill to carry out room-temperature dry ball milling of the iron carbonyl powder - graphite composite pre-powder obtained in Step 2 without using solvents and high temperatures: The grinding balls of the planetary ball mill are three kinds of agate balls with diameters of 6, 10 and 15 mm respectively. Among them, the mass ratio of the agate ball with a diameter of 15 mm: the agate ball with a diameter of 10 mm: the agate ball with a diameter of 6 mm is 20:50:30, the ball-to-material mass ratio is 2:1, and positive - reverse two ball milling methods are adopted. The ball milling speed is 200 r / min, with an intermittent period of 5 - 10 minutes every 1 h, and then reverse ball milling is carried out. After ball milling for 60 h, an iron carbonyl powder - graphite composite electromagnetic wave absorption material is obtained.

[0108] Mix the carbonyl iron powder absorbing material obtained in Step 3 with paraffin wax. According to the national standard GJB 2038A-2011, the reflection loss results of the carbonyl iron powder-graphite composite absorbing material prepared in Example 7 of the present invention are shown in Figure 12 . As can be seen from the figure, for the carbonyl iron powder-graphite composite absorbing material of Example 7, when the thickness is 1.66 mm, the effective absorbing bandwidth reaches 7.42 GHz, and its absorbing performance is greatly improved compared with Comparative Examples 1-3 (7.42 GHz vs. 3.89 GHz vs. 2 GHz vs. 0 GHz).

[0109] Example 8

[0110] A preparation method of a carbonyl iron powder-graphite electromagnetic wave absorbing composite material, comprising the following steps:

[0111] Step 1: Use an ultrasonic vibrating screen to screen the original carbonyl iron powder at room temperature. The power of the ultrasonic vibrating screen machine is 1.5 kw, with 3 layers of screening mesh, ultrasonic treatment for 5 times, 10 minutes each time, and an interval of 2 minutes; cool to room temperature and filter to obtain ultrafine spherical carbonyl iron powder with a particle size of 0.5-3 μm.

[0112] Step 2: Mix the ultrafine spherical carbonyl iron powder obtained in Step 1 with flaky graphite at a mass ratio of 8:1, and mechanically stir for 10 minutes at a rotation speed of 100 r / min to obtain a carbonyl iron powder-graphite composite pre-powder;

[0113] Step 3: Use a planetary ball mill to perform room-temperature dry ball milling of the carbonyl iron powder-graphite composite pre-powder obtained in Step 2 without using solvents and high temperatures: The grinding balls of the planetary ball mill are three kinds of agate balls with diameters of 6, 12, and 15 mm respectively. Among them, the mass ratio of the 15-mm-diameter agate ball: the 12-mm-diameter agate ball: the 6-mm-diameter agate ball is 20:50:30, the ball-to-material mass ratio is 1:1, and two ball milling methods, forward and reverse, are adopted. The ball milling speed is 250 r / min, with an intermittent period of 5-10 minutes every 1 h, and then reverse ball milling. After ball milling for 72 h, a carbonyl iron powder-graphite composite absorbing material is obtained.

[0114] Mix the carbonyl iron powder absorbing material obtained in Step 3 with paraffin wax. According to the national standard GJB 2038A-2011, the reflection loss results of the carbonyl iron powder-graphite composite absorbing material prepared in Example 8 of the present invention are shown in Figure 13 . As can be seen from the figure, for the carbonyl iron powder-graphite composite absorbing material of Example 8, when the thickness is 1.96 mm, the effective absorbing bandwidth reaches 6.67 GHz, and its absorbing performance is greatly improved compared with Comparative Examples 1-3 (6.67 GHz vs. 3.89 GHz vs. 2 GHz vs. 0 GHz).

[0115] As can be seen from the above examples and comparative examples, compared with Comparative Examples 1-3 (the effective absorption bandwidth is 0-3.89 GHz), the effective absorption bandwidth of the carbonyl iron powder-graphite composite absorbing material prepared in Examples 1-8 is 4.71-8.10 GHz, achieving an improvement in absorption performance.

[0116] The preparation methods of the carbonyl iron powder-graphite electromagnetic wave absorbing composites in Examples 1-8 can be summarized as follows:

[0117] (1) Mix ultrafine spherical carbonyl iron powder and flaky graphite in a mass ratio of 1-8:1 to obtain a carbonyl iron powder-graphite composite pre-powder; the particle size of the ultrafine spherical carbonyl iron powder is 0.5-3 μm;

[0118] (2) Use a ball mill to perform room-temperature dry ball milling on the carbonyl iron powder-graphite composite pre-powder without solvent and high temperature to obtain a carbonyl iron powder-graphite composite absorbing material; the grinding balls of the ball mill are composed of three kinds of grinding balls with diameters of 12-15 mm, 9-10 mm, and 3-6 mm in a mass ratio of 20:50:30, the ball-to-material mass ratio of the ball mill is 1-10:1, the rotation speed of the ball mill is 50-500 r / min, and the ball milling time of the ball mill is 3-72 h.

[0119] Among them, the preparation method of the ultrafine spherical carbonyl iron powder is: use an ultrasonic vibrating screen to screen the original carbonyl iron powder at room temperature.

[0120] Furthermore, in Examples 1-8, the effective absorption bandwidths of Examples 2-8 are 5.23-8.10 GHz, and the absorption performance is better; the preferred preparation methods of Examples 2-8 are:

[0121] In step (1), the mass ratio of the ultrafine spherical carbonyl iron powder to the flaky graphite is 2-8:1;

[0122] In step (2), the ball-to-material mass ratio of the ball mill is 1-9:1, the rotation speed of the ball mill is 100-500 r / min, and the ball milling time of the ball mill is 6-72 h.

[0123] Even further, in Examples 2-8, the effective absorption bandwidths of Examples 4-7 are 7.42-8.10 GHz, and the absorption performance is better; the preferred preparation methods of Examples 4-7 are:

[0124] In step (1), the mass ratio of the ultrafine spherical carbonyl iron powder to the flaky graphite is 4-7:1;

[0125] In step (2), the ball-to-material mass ratio of the ball mill is 2-6:1, the rotation speed of the ball mill is 200-500 r / min, and the ball milling time of the ball mill is 36-60 h.

[0126] Furthermore, in Examples 4-7, the effective wave absorption bandwidth of Examples 4-6 is 7.55-8.10 GHz, and the wave absorption performance is better; the preparation method of Examples 4-6 is preferably as follows:

[0127] In step (1), the mass ratio of the ultrafine spherical carbonyl iron powder to the flaky graphite is 4-6:1;

[0128] In step (2), the mass ratio of the grinding balls to the materials in the ball mill is 3-6:1, the rotation speed of the ball mill is 300-500 r / min, and the ball milling time of the ball mill is 36-48 h.

[0129] The preparation method of the present invention synergistically optimizes multiple parameters such as the mass ratio of the ultrafine spherical carbonyl iron powder to the flaky graphite, the diameter of the grinding balls, the mass ratio of the grinding balls to the materials, the rotation speed of the ball mill, and the ball milling time during the ball milling process, and obtains a carbonyl iron powder-graphite composite wave absorption material with better wave absorption performance.

Claims

1. A method for preparing a carbonyl iron powder-graphite electromagnetic wave absorbing composite material, characterized in that, The method includes: (1) Mixing ultrafine spherical carbonyl iron powder and flaky graphite at a mass ratio of 1-8:1 to obtain a carbonyl iron powder-graphite composite pre-powder; the particle size of the ultrafine spherical carbonyl iron powder is 0.5-3 μm; (2) Using a ball mill to perform dry ball milling on the carbonyl iron powder-graphite composite pre-powder at room temperature to obtain a carbonyl iron powder-graphite composite microwave absorbing material; the grinding balls of the ball mill are composed of three kinds of grinding balls with diameters of 12-15 mm, 9-10 mm, and 3-6 mm at a mass ratio of 20:50:30, the ball-to-material mass ratio of the ball mill is 1-10:1, the rotation speed of the ball mill is 50-500 r / min, and the ball milling time of the ball mill is 3-72 h.

2. The method according to claim 1, wherein In step (1), the preparation method of the ultrafine spherical carbonyl iron powder is: screening the original carbonyl iron powder at room temperature using an ultrasonic vibrating screen.

3. The method according to any one of claims 1-2, characterized in that In step (1), the mass ratio of the ultrafine spherical carbonyl iron powder to the flaky graphite is 2-8:

1.

4. The method according to claim 3, characterized in that, In step (1), the mass ratio of the ultrafine spherical carbonyl iron powder to the flaky graphite is 4-7:

1.

5. The method according to claim 3, characterized in that, In step (1), the mass ratio of the ultrafine spherical carbonyl iron powder to the flaky graphite is 4-6:

1.

6. The method according to any one of claims 1-2, characterized in that, In step (2), the ball-to-material mass ratio of the ball mill is 1-9:1, the rotation speed of the ball mill is 100-500 r / min, and the ball milling time of the ball mill is 6-72 h.

7. The method according to claim 6, characterized in that, In step (2), the ball-to-material mass ratio of the ball mill is 2-6:1, the rotation speed of the ball mill is 200-500 r / min, and the ball milling time of the ball mill is 36-60 h.

8. The method according to claim 6, wherein In step (2), the ball-to-material mass ratio of the ball mill is 3-6:1, the rotation speed of the ball mill is 300-500 r / min, and the ball milling time of the ball mill is 36-48 h.

9. Carbonyl iron powder-graphite electromagnetic wave absorption composite material, characterized in that, The carbonyl iron powder-graphite electromagnetic wave absorbing composite material is a carbonyl iron powder-graphite electromagnetic wave absorbing composite material prepared by using any one of the methods described in claims 1-8.

10. Application of the carbonyl iron powder-graphite electromagnetic wave absorbing composite material according to claim 9 in a microwave absorbing device.

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