An electromagnetic shielding nanocrystalline soft magnetic composite and its preparation method

Abstract

The present invention discloses an electromagnetic shielding nanocrystalline soft magnetic composite and a preparation method thereof in the technical field of composite materials, which are prepared from the following components in parts by weight: 3-4.5 parts of graphene oxide, 6-7 parts of ferric nitrate nonahydrate, 1.9-2.2 parts of cobalt nitrate hexahydrate, 300-350 parts of nanocrystalline alloy powder, and 3-4.2 parts of insulating resin. The present invention proposes to introduce cobalt ferrite into graphene oxide to wrap the nanocrystalline alloy powder, prepare a nanocrystalline double magnetic core shielding body with a core-shell structure, realize the improvement of the magnetic loss ability, and at the same time further coat the shielding body with insulating resin to eliminate defects and form a dense insulating layer, inhibit the eddy current between magnetic particles, and realize the improvement of the electromagnetic shielding efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite materials, and specifically refers to an electromagnetic shielding nanocrystalline soft magnetic composite body and a preparation method thereof. Background Art

[0002] With the development and popularization of various electronic devices, the electromagnetic pollution generated by electrical equipment has posed a threat to the environment and people's physical health. Electromagnetic shielding refers to reducing the intensity of electromagnetic fields and the radiation of electromagnetic waves through materials or physical barriers, so as to achieve the purpose of reducing electromagnetic interference. Traditional electromagnetic shielding materials have the disadvantages of large thickness, large density, low electromagnetic shielding efficiency, and limitations in the application of the electromagnetic shielding field; Absorbing materials are a widely used shielding material, which means that when electromagnetic waves enter the material, they are converted into other forms of energy and dissipated, or the electromagnetic waves cancel each other out due to interference, so as to effectively reduce electromagnetic radiation. Excellent absorbing materials must first have a strong ability to absorb and dissipate electromagnetic waves. Currently, the commonly used absorbing materials are as follows: ferrite, hydroxy iron material, ceramic material, conductive polymer material, amorphous material, nanocrystalline material; Nanocrystalline materials have a higher saturation magnetic induction intensity and magnetic permeability than amorphous alloys, a lower specific gravity, and higher frequency eddy current losses. Therefore, they have a stronger absorbing ability and a wider absorption frequency band.

[0003] Currently, the existing technologies mainly have the following problems: the electromagnetic shielding efficiency of commonly used shielding materials is insufficient. Summary of the Invention

[0004] In view of the above situation, in order to overcome the defects of the existing technology, the present invention provides an electromagnetic shielding nanocrystalline soft magnetic composite body and a preparation method thereof. In order to solve the problem of insufficient electromagnetic shielding efficiency of commonly used shielding materials, the present invention proposes to introduce cobalt ferrite into graphene oxide to wrap the nanocrystalline alloy powder, and prepare a nanocrystalline dual magnetic core shielding body with a core-shell structure, realizing the improvement of the magnetic loss ability. At the same time, the shielding body is further coated with an insulating resin to eliminate defects and form a dense insulating layer, suppressing the eddy current between magnetic particles, and realizing the improvement of the electromagnetic shielding efficiency.

[0005] In order to achieve the above purpose, the technical solution adopted by the present invention is as follows: The present invention provides an electromagnetic shielding nanocrystalline soft magnetic composite body, which is prepared from the following components in parts by weight: 3-4.5 parts of graphene oxide, 6-7 parts of ferric nitrate nonahydrate, 1.9-2.2 parts of cobalt nitrate hexahydrate, 300-350 parts of nanocrystalline alloy powder, and 3-4.2 parts of insulating resin.

[0006] Preferably, the insulating resin is an epoxy-modified silicone resin, CAS: 67763-03-5, model: SH-023-4.

[0007] Preferably, the nanocrystalline alloy powder is composed of the following components by weight percentage: Mo 1.8 - 2%, Si 2.5 - 3%, B 8 - 8.6%, P 4 - 4.2%, Cu 1 - 1.3%, and the balance is Fe and unavoidable impurities;

[0008] Preferably, the preparation method of the nanocrystalline alloy powder specifically includes the following steps:

[0009] Mix Mo, Si, B, P, Cu, and Fe evenly, and under the protection of argon with a vacuum degree of 3×10 -3 Pa, perform arc melting to obtain an Fe - Si - B - P - Cu - Mo alloy ingot, then perform single - roll strip casting to obtain an amorphous alloy strip with a thickness of 22 μm. Vacuum anneal the amorphous alloy strip. Under the condition of a vacuum degree of 5×10 -3 Pa, heat it at 10 °C / min to 500 - 550 °C, hold for 30 min, then cool to room temperature. Finally, take 8 - mm steel grinding balls, and perform ball milling at a ball - to - material ratio of 8 - 10:1 and a speed of 300 rpm for 10 - 12 h to obtain the nanocrystalline alloy powder.

[0010] The present invention also provides a preparation method of an electromagnetic shielding nanocrystalline soft magnetic composite, which specifically includes the following steps:

[0011] S1. Add graphene oxide to deionized water, and ultrasonically disperse to obtain a dispersion. Add ferric nitrate nonahydrate to deionized water, add cobalt nitrate hexahydrate, and stir evenly to obtain a mixed solution;

[0012] S2. Drop the mixed solution obtained in S1 into the dispersion obtained in S1, adjust the pH to 12.5, stir in an oil bath, cool, and perform magnetic separation to obtain cobalt ferrite - graphene oxide;

[0013] S3. Uniformly mix the cobalt ferrite - graphene oxide obtained in S2 and the nanocrystalline alloy powder to obtain a mixed powder, and perform ball milling to obtain a nanocrystalline dual - core shielding body;

[0014] S4. Add the nanocrystalline dual - core shielding body obtained in S3 to a 10 wt% insulating resin acetone solution, heat at 50 °C, stir at 80 - 100 rpm until the powder is dry to obtain the electromagnetic shielding nanocrystalline soft magnetic composite.

[0015] Preferably, in S1, the addition amount of graphene oxide in deionized water is 3 - 4 mg / mL.

[0016] Preferably, in S1, the addition amount of ferric nitrate nonahydrate in deionized water is 60 - 80 mg / mL.

[0017] Preferably, in S2, the oil bath stirring is carried out at a temperature of 80 - 90 °C, a speed of 60 - 80 rpm, and a time of 4 - 5 h.

[0018] Preferably, in S3, for the ball milling, 6 mm alumina balls are used as grinding balls, the ball-to-material ratio is 15 - 20:1, the rotation speed is 280 - 300 rpm, and the time is 100 - 120 min.

[0019] The beneficial effects achieved by the present invention are as follows: By adding Mo, the α-Fe grains in the nanocrystalline alloy are refined, and the composition is adjusted to obtain a nanocrystalline alloy with good soft magnetic properties; at the same time, cobalt ferrite is introduced onto graphene oxide to coat the nanocrystalline alloy powder, constructing an electromagnetic loss composite material to obtain a nanocrystalline double magnetic core shield with a core-shell structure. The double magnetic core structure is conducive to generating a synergistic effect through coupling, enhancing the magnetic loss ability of the material. Its heterogeneous structure forms rich dipole polarization and interfacial polarization to further improve the shielding effect; the nanocrystalline double magnetic core shield is secondarily coated with an insulating resin to further eliminate defects, form a dense insulating layer, effectively suppress the eddy current between ferromagnetic particles, increase the resistivity of the material, maximize the matching of magnetic properties and dielectric properties, improve the absorption rate of the material, and simultaneously optimize the impedance matching of the material with cobalt ferrite-graphene oxide, enhance the wave absorption performance, thereby reducing the reflection coefficient while improving the total shielding efficiency and reducing the pollution caused by secondary reflection. Description of the Drawings

[0020] Figure 1 It is a result diagram of the reduction rate of the reflection coefficient for the shielding performance test of Examples 1 - 3 and Comparative Examples 1 - 2 of the present invention;

[0021] Figure 2 It is a result diagram of the improvement rate of the total shielding efficiency for the shielding performance test of Examples 1 - 3 and Comparative Examples 1 - 2 of the present invention.

[0022] 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. Detailed Embodiments

[0023] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0024] Unless otherwise defined, all professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to the described content can be applied to the present invention. The preferred implementation methods and materials described herein are for illustrative purposes only and do not limit the content of this application.

[0025] In the experimental methods of the following examples, unless otherwise specified, they are all conventional methods; in the test materials used in the following examples, unless otherwise specified, they are all purchased from commercial channels.

[0026] Example 1

[0027] An electromagnetic shielding nanocrystalline soft magnetic composite is prepared from the following components by weight: 3 parts of graphene oxide, 6 parts of ferric nitrate nonahydrate, 1.9 parts of cobalt nitrate hexahydrate, 300 parts of nanocrystalline alloy powder, and 3 parts of insulating resin.

[0028] The nanocrystalline alloy powder is composed of the following weight percentage components: Mo 1.8%, Si 2.5%, B 8%, P 4%, Cu 1%, and the balance is Fe and unavoidable impurities;

[0029] The preparation method of the nanocrystalline alloy powder specifically includes the following steps:

[0030] Mix Mo, Si, B, P, Cu, and Fe evenly, and under an argon protection with a vacuum degree of 3×10 -3 Pa, perform arc melting to obtain an Fe-Si-B-P-Cu-Mo alloy ingot, and then perform single-roll strip casting to obtain an amorphous alloy strip with a thickness of 22 μm. Anneal the amorphous alloy strip in vacuum. Under the condition of a vacuum degree of 5×10 -3 Pa, heat it to 500 °C at a rate of 10 °C / min, keep it warm for 30 min, then cool it to room temperature. Finally, take 8 mm steel ball grinding balls, and perform ball milling at a ball-to-material ratio of 8:1 and a speed of 300 rpm for 10 h to obtain the nanocrystalline alloy powder.

[0031] The present invention also provides a preparation method of an electromagnetic shielding nanocrystalline soft magnetic composite, which specifically includes the following steps:

[0032] S1. Add graphene oxide to deionized water at an addition amount of 3 mg / mL, and obtain a dispersion liquid by ultrasonic dispersion. Add ferric nitrate nonahydrate to deionized water at an addition amount of 60 mg / mL, add cobalt nitrate hexahydrate, and stir evenly to obtain a mixed liquid;

[0033] S2. Drop the mixed liquid obtained in S1 into the dispersion liquid obtained in S1, adjust the pH to 12.5, stir at 60 rpm in an 80 °C oil bath for 4 h, cool and perform magnetic separation to obtain cobalt ferrite-graphene oxide;

[0034] S3. Uniformly mix the cobalt ferrite-graphene oxide and nanocrystalline alloy powder obtained in S2 to obtain a mixed powder. Perform ball milling with 6 mm alumina balls at a ball-to-material ratio of 15:1, a rotation speed of 280 rpm, and a time of 100 min to obtain a nanocrystalline dual-core shield.

[0035] S4. Add the nanocrystalline dual-core shield obtained in S3 to a 10 wt% insulating resin acetone solution, heat at 50 °C, stir at 80 rpm until the powder is dry to obtain an electromagnetic shielding nanocrystalline soft magnetic composite.

[0036] Example 2

[0037] An electromagnetic shielding nanocrystalline soft magnetic composite is prepared from the following components by weight: 4.5 parts of graphene oxide, 7 parts of ferric nitrate nonahydrate, 2.2 parts of cobalt nitrate hexahydrate, 350 parts of nanocrystalline alloy powder, and 4.2 parts of insulating resin.

[0038] The nanocrystalline alloy powder is composed of the following weight percentages: Mo 2%, Si 3%, B 8.6%, P 4.2%, Cu 1.3%, and the balance is Fe and unavoidable impurities.

[0039] The preparation method of the nanocrystalline alloy powder specifically includes the following steps:

[0040] Uniformly mix Mo, Si, B, P, Cu, and Fe. Under an argon protection with a vacuum degree of 3×10 -3 Pa, perform arc melting to obtain an Fe-Si-B-P-Cu-Mo alloy ingot, and then perform single-roll strip casting to obtain an amorphous alloy strip with a thickness of 22 μm. Vacuum anneal the amorphous alloy strip. Under the condition of a vacuum degree of 5×10 -3 Pa, heat at 10 °C / min to 550 °C, hold for 30 min, then cool to room temperature. Finally, take 8 mm steel ball grinding balls and perform ball milling at a ball-to-material ratio of 10:1 and a speed of 300 rpm for 12 h to obtain the nanocrystalline alloy powder.

[0041] The present invention also provides a preparation method of an electromagnetic shielding nanocrystalline soft magnetic composite, which specifically includes the following steps:

[0042] S1. Add graphene oxide to deionized water at an addition amount of 4 mg / mL, and ultrasonically disperse to obtain a dispersion. Add ferric nitrate nonahydrate to deionized water at an addition amount of 80 mg / mL, add cobalt nitrate hexahydrate, and stir evenly to obtain a mixed solution.

[0043] S2. Drop the mixed solution obtained in S1 into the dispersion obtained in S1, adjust the pH to 12.5, perform oil bath stirring at 90 °C and 80 rpm for 5 h, cool and perform magnetic separation to obtain cobalt ferrite-graphene oxide.

[0044] S3. Uniformly mix the cobalt ferrite-graphene oxide and nanocrystalline alloy powder obtained in S2 to obtain a mixed powder. Use 6 mm alumina balls for ball milling with a ball-to-material ratio of 20:1, a rotation speed of 300 rpm, and a time of 120 min to obtain a nanocrystalline dual magnetic core shield.

[0045] S4. Add the nanocrystalline dual magnetic core shield obtained in S3 to a 10 wt% insulating resin acetone solution, heat at 50 °C, stir at 100 rpm until the powder is dry to obtain an electromagnetic shielding nanocrystalline soft magnetic composite.

[0046] Example 3

[0047] An electromagnetic shielding nanocrystalline soft magnetic composite is prepared from the following components by weight: 4 parts of graphene oxide, 6.5 parts of ferric nitrate nonahydrate, 2 parts of cobalt nitrate hexahydrate, 325 parts of nanocrystalline alloy powder, and 3.5 parts of insulating resin.

[0048] The nanocrystalline alloy powder is composed of the following components by weight percentage: Mo 1.9%, Si 2.7%, B 8.3%, P 4.1%, Cu 1.2%, and the balance is Fe and unavoidable impurities;

[0049] The preparation method of the nanocrystalline alloy powder specifically includes the following steps:

[0050] Uniformly mix Mo, Si, B, P, Cu, and Fe. Under an argon protection with a vacuum degree of 3×10 -3 Pa, perform arc melting to obtain a Fe-Si-B-P-Cu-Mo alloy ingot, and then perform single-roll casting to obtain an amorphous alloy strip with a thickness of 22 μm. Vacuum anneal the amorphous alloy strip. Under the condition of a vacuum degree of 5×10 -3 Pa, heat at 10 °C / min to 525 °C, hold for 30 min, then cool to room temperature. Finally, take 8 mm steel ball grinding balls, perform ball milling at a ball-to-material ratio of 9:1 and a speed of 300 rpm for 11 h to obtain the nanocrystalline alloy powder.

[0051] The present invention also provides a preparation method of an electromagnetic shielding nanocrystalline soft magnetic composite, specifically including the following steps:

[0052] S1. Add graphene oxide to deionized water at an addition amount of 3.5 mg / mL, and obtain a dispersion liquid by ultrasonic dispersion. Add ferric nitrate nonahydrate to deionized water at an addition amount of 70 mg / mL, add cobalt nitrate hexahydrate, and stir evenly to obtain a mixed liquid;

[0053] S2. Drop the mixed liquid obtained in S1 into the dispersion liquid obtained in S1, adjust the pH to 12.5, perform oil bath stirring at 85 °C and 70 rpm for 4.5 h, cool and perform magnetic separation to obtain cobalt ferrite-graphene oxide;

[0054] S3. Uniformly mix the cobalt ferrite-graphene oxide and nanocrystalline alloy powder obtained in S2 to obtain a mixed powder. Use 6 mm alumina balls for ball milling. The ball-to-material ratio is 17:1, the rotation speed is 290 rpm, and the time is 110 min to obtain a nanocrystalline dual-core shield.

[0055] S4. Add the nanocrystalline dual-core shield obtained in S3 to a 10 wt% insulating resin acetone solution, heat at 50 °C, stir at 90 rpm until the powder is dry to obtain an electromagnetic shielding nanocrystalline soft magnetic composite.

[0056] Comparative Example 1

[0057] This comparative example provides a composite, the difference from Example 1 is only that the component does not contain cobalt ferrite-graphene oxide, and the remaining components and component contents are the same as those in Example 1.

[0058] Comparative Example 2

[0059] This comparative example provides a composite, the difference from Example 1 is only that the component does not contain insulating resin, and the remaining components and component contents are the same as those in Example 1.

[0060] Experimental Example

[0061] 1. Shielding performance test

[0062] Uniformly mix the materials obtained in Examples 1-3 and Comparative Examples 1-2 and the nanocrystalline alloy powder obtained in Example 1 with paraffin at a mass ratio of 3:1, and press them into ring-shaped samples with an inner diameter of 3 mm, an outer diameter of 7 mm, and a thickness of 2 mm using a mold. Among them, Examples 1-3 and Comparative Examples 1-2 are the experimental groups, and the nanocrystalline alloy powder is the control group. Use an AV3629 high-performance microwave integrated vector network analyzer to measure the samples by the coaxial method, and take the reflection coefficient and total shielding effectiveness of each group of samples at 10 GHz, and calculate the reflection coefficient reduction rate and shielding performance improvement rate of the samples;

[0063] Calculate the reflection coefficient reduction rate according to the following formula:

[0064] Reflection coefficient reduction rate = (Reflection coefficient of the control group - Reflection coefficient of the experimental group) / Reflection coefficient of the control group × 100%;

[0065] Calculate the total shielding performance improvement rate according to the following formula:

[0066] Total shielding effectiveness improvement rate = (Total shielding effectiveness of the experimental group - Total shielding effectiveness of the control group) / Total shielding effectiveness of the control group × 100%.

[0067] Figure 1This is the result graph of the reduction rate of the reflection coefficient for the shielding performance test of Examples 1-3 and Comparative Examples 1-2 of the present invention; as shown in the figure, the reduction rates of the reflection coefficient of Examples 1-3 and Comparative Examples 1-2 are 76.5%, 77.3%, 75.9%, 50.6%, and 36.2% respectively; the reduction rate of the reflection coefficient of Examples 1-3 is significantly higher than that of Comparative Examples 1-2, indicating that the use of cobalt ferrite-graphene oxide and insulating resin reduces the reflection coefficient of the material and can effectively reduce the secondary pollution of electromagnetic radiation.

[0068] Figure 2 This is the result graph of the improvement rate of the total shielding effectiveness for the shielding performance test of Examples 1-3 and Comparative Examples 1-2 of the present invention; as shown in the figure, the improvement rates of the total shielding effectiveness of Examples 1-3 and Comparative Examples 1-2 are 43.0%, 42.3%, 43.9%, 25.1%, and 32.3% respectively; the improvement rate of the total shielding effectiveness of Examples 1-3 is significantly higher than that of Comparative Examples 1-2, indicating that the use of cobalt ferrite-graphene oxide and insulating resin improves the total shielding effectiveness of the material.

[0069] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention.

[0070] The above describes the present invention and its implementation manners. Such a description is not restrictive. What is shown in the drawings is only one of the implementation manners of the present invention, and the actual application is not limited thereto. Generally speaking, if those of ordinary skill in the art are inspired by it and design similar ways and embodiments to this technical solution without creative efforts without departing from the purpose of the present invention, they shall fall within the protection scope of the present invention.

Claims

1. An electromagnetic shielding nanocrystalline soft magnetic composite, characterized in that, Prepared from the following components in parts by weight: 3 - 4.5 parts of graphene oxide, 6 - 7 parts of ferric nitrate nonahydrate, 1.9 - 2.2 parts of cobalt nitrate hexahydrate, 300 - 350 parts of nanocrystalline alloy powder, and 3 - 4.2 parts of insulating resin; The nanocrystalline alloy powder consists of the following components by weight percentage: Mo 1.8 - 2%, Si 2.5 - 3%, B 8 - 8.6%, P 4 - 4.2%, Cu 1 - 1.3%, and the balance is Fe and unavoidable impurities; The preparation method of the nanocrystalline alloy powder specifically includes the following steps: Mix Mo, Si, B, P, Cu, and Fe evenly, and under a vacuum of 3×10 -3 Pa and under argon protection, perform arc melting to obtain an Fe-Si-B-P-Cu-Mo alloy ingot. Subsequently, perform single-roll strip casting to obtain an amorphous alloy strip with a thickness of 22 μm. Anneal the amorphous alloy strip in vacuum. Under the condition of a vacuum of 5×10 -3 Pa, heat it to 500 - 550 °C at a rate of 10 °C / min, hold for 30 min, then cool to room temperature. Finally, take 8 mm steel grinding balls, and perform ball milling at a ball-to-material ratio of 8 - 10:1 and a speed of 300 rpm for 10 - 12 h to obtain nanocrystalline alloy powder; The insulating resin is epoxy-modified silicone resin, CAS: 67763-03-5, model: SH-023-4.

2. A preparation method of the electromagnetic shielding nanocrystalline soft magnetic composite according to claim 1, characterized in that: Specifically includes the following steps: S1. Add graphene oxide into deionized water, and obtain a dispersion liquid by ultrasonic dispersion. Add ferric nitrate nonahydrate into deionized water, add cobalt nitrate hexahydrate, and stir evenly to obtain a mixed liquid; S2. Drop the mixed liquid obtained in S1 into the dispersion liquid obtained in S1, adjust the pH to 12.5, stir in an oil bath, cool, and perform magnetic separation to obtain cobalt ferrite-graphene oxide; S3. Uniformly mix the cobalt ferrite-graphene oxide obtained in S2 and the nanocrystalline alloy powder to obtain a mixed powder, and perform ball milling to obtain a nanocrystalline dual magnetic core shield; S4. Add the nanocrystalline dual magnetic core shield obtained in S3 into a 10wt% insulating resin acetone solution, heat at 50°C, stir at 80 - 100 rpm until the powder is dry to obtain an electromagnetic shielding nanocrystalline soft magnetic composite.

3. The preparation method of the electromagnetic shielding nanocrystalline soft magnetic composite according to claim 2, characterized in that: In S1, the addition amount of graphene oxide in deionized water is 3 - 4 mg / mL.

4. The preparation method of the electromagnetic shielding nanocrystalline soft magnetic composite according to claim 3, characterized in that: In S1, the addition amount of ferric nitrate nonahydrate in deionized water is 60 - 80 mg / mL.

5. The preparation method of the electromagnetic shielding nanocrystalline soft magnetic composite according to claim 4, characterized in that: In S2, for the oil bath stirring, the temperature is 80 - 90°C, the speed is 60 - 80 rpm, and the time is 4 - 5 h.

6. The preparation method of the electromagnetic shielding nanocrystalline soft magnetic composite according to claim 5, characterized in that: In S3, for the ball milling, the grinding balls are 6 mm alumina balls, the ball-to-material ratio is 15 - 20:1, the rotation speed is 280 - 300 rpm, and the time is 100 - 120 min.

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