Magnetic composite adhesive, preparation method and application

Abstract

The invention discloses a magnetic composite adhesive, a preparation method and application, and belongs to the field of magnetic materials, the magnetic composite adhesive is structurally characterized in that the magnetic composite adhesive is a multi-scale heterogeneous interface, and the magnetic composite adhesive comprises the following components in percentage by weight: 15-30% of an epoxy resin matrix, paint or silica gel, 10-99% of graphene, 30-60% of magnetic powder, 5-20% of iron-silicon alloy powder and 0.5-1.0% of a silane coupling agent; a key interface in the composite adhesive reacts to generate a chemical bridging structure. By adopting the magnetic composite adhesive, the preparation method and the application, through three-in-one innovation of a chemical bonding interface, multi-scale material design and process precise regulation and control, the contradiction of high loss, low strength and weak heat dissipation of a high-frequency magnetic material is broken through, and a bottom layer material support is provided for a high-reliability electronic system.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic materials, and particularly to a magnetic composite adhesive, a preparation method and an application thereof. Background Art

[0002] Currently, in the field of manufacturing magnetic components, conventional magnetic conductive adhesives are mainly composed of epoxy adhesives as the matrix material, compounded with components such as curing agents, toughening agents and carbonyl iron powder; or prepared by blending polymer materials such as polystyrene and polyethylene with ferrite powder and carbonyl iron powder. Such materials mainly undertake the dual functions of magnetic medium bonding and forming and particle insulation; on the one hand, the shaping process of ferrite powder is realized through the bonding effect, and on the other hand, the eddy current loss in the alternating magnetic field is reduced by isolating iron powder particles, thereby improving the quality factor of the magnetic core.

[0003] However, through practical verification, the existing magnetic conductive adhesive technology has the following significant defects: 1. Poor adaptability to high-frequency working conditions: When the working frequency exceeds 5 MHz, the dielectric loss of the material increases sharply, resulting in a significant decrease in the current-carrying capacity; 2. Insufficient thermal stability: The glass transition temperature range is narrow (80 - 100 °C), and the mismatch rate between the thermal expansion coefficient and the magnetic matrix material > 15%, resulting in high-temperature interface peeling; 3. Lack of heat dissipation performance: The thermal conductivity is generally lower than 0.3 W / (m·K), and it is unable to effectively conduct the Joule heat generated under high-frequency working conditions; 4. Low electromagnetic comprehensive efficiency: The relative magnetic permeability , the loss tangent value , making it difficult to meet the energy efficiency requirements of high-frequency transformers; 5. Insufficient electromagnetic shielding efficiency: The shielding efficiency in the 1 - 10 GHz frequency band < 20 dB, resulting in the inability to effectively suppress electromagnetic radiation from the transformer spray coating and the shell.

[0004] The above technical defects seriously restrict the development of high-frequency magnetic devices towards miniaturization and high power density. Summary of the Invention

[0005] The purpose of the present invention is to provide a magnetic composite adhesive, a preparation method and an application thereof to solve the above technical problems.

[0006] To achieve the above purpose, the present invention provides a magnetic composite adhesive. The structural feature of the magnetic composite adhesive is a multi-scale heterogeneous interface, and it includes the following components by weight percentage: 15% - 30% of epoxy resin matrix, paint or silica gel, 10% - 99% of graphene, 30% - 60% of magnetic powder, 5% - 20% of iron-silicon alloy powder, and 0.5% - 1.0% of silane coupling agent; In the composite adhesive, a key interfacial reaction generates a chemical bridging structure. The bonding between the silane coupling agent and the magnetic powder is ≡Si-O-Fe / Si / Al on the surface of Fe / Si / Al particles. The bond type is a covalent bond, and the bond energy is 103.5 eV.

[0007] Preferably, the purity of graphene is greater than 99.9%, and the number of layers is less than 6; the mesh number of the iron-silicon alloy powder is 50 mesh - 300 mesh.

[0008] A preparation method of a magnetic composite adhesive includes the following steps: S1. Prepare an epoxy resin matrix, paint or silica gel, graphene, magnetic powder, iron-silicon alloy powder, and silane coupling agent according to weight components; S2. Ultrasonic mixing: The iron-silicon alloy powder and magnetic powder are loaded into a sealed constant-temperature ultrasonic tank for ultrasonic dispersion treatment to obtain a composite material; S3. Ball milling treatment: Add a silane coupling agent and steel balls to the composite material for ball milling treatment to obtain a powder composite material; S4. Shear emulsification: Add paint, epoxy resin or silica gel to the powder composite material for shear emulsification treatment to obtain a magnetic composite adhesive.

[0009] Preferably, in step S2, the ultrasonic mixing time is 4 h, and the temperature is 100 °C.

[0010] Preferably, in step S3, the ball milling treatment time is 4 h, the temperature is 100 °C, and the pH value is 6; In step S3, the silane coupling agent Undergoes the following hydrolysis and condensation reactions: .

[0011] Preferably, in step S4, the shear emulsification time is 6 h; When adding epoxy resin, the following coupling reaction occurs with the amino group in the powder composite material: .

[0012] Applications of the magnetic composite adhesive in inductance coating, external spraying of transformers, metallization electrodes on ferrite cores, coils, bypass shielding, heat radiation conduction, core encapsulation, electromagnetic shielding, and filters.

[0013] Therefore, by using the above-mentioned magnetic composite adhesive, preparation method, and application, the beneficial effects of the present invention are as follows: 1. Increase the magnetic flux by more than about 15%: By introducing graphene, iron-silicon alloy powder, and magnetic powder, the magnetic permeability is significantly improved. Specifically, graphene has excellent electrical and thermal conductivity, which can effectively reduce the internal resistance of the material and reduce hysteresis loss. At the same time, the addition of iron-silicon alloy powder and magnetic powder further enhances the magnetic induction intensity of the material, increasing the magnetic flux by more than about 15% under the same conditions. This not only improves the overall magnetic properties of the material but also provides more efficient energy transfer for applications such as high-frequency inductors and transformers. 2. Have excellent broadband electromagnetic wave shielding effectiveness: By optimizing the type and distribution of fillers, effective shielding of broadband electromagnetic waves is achieved. The principle lies in that graphene and magnetic powder can absorb and dissipate electromagnetic energy in different frequency ranges, thus preventing electromagnetic waves from penetrating the material surface. In addition, ultrasonic dispersion and ball milling processes ensure the uniform distribution of fillers, forming a multi-layer electromagnetic shielding barrier that effectively covers a wide frequency band from low frequency to high frequency. This broadband electromagnetic wave shielding property is crucial for anti-interference design in electronic devices, especially applicable to the fields of wireless communication, radar, and microwave technology. 3. Can reduce eddy current loss and improve efficiency under high-frequency applications: By introducing highly conductive graphene and high magnetic permeability magnetic powder, the generation of eddy currents is effectively suppressed. Specifically, the two-dimensional structure of graphene can disperse the current path and reduce the concentration effect, while magnetic powder improves the coupling efficiency of the magnetic circuit and reduces the useless consumption of magnetic field energy. Therefore, under high-frequency current, the eddy current loss of the material is significantly reduced, significantly improving the overall working efficiency and reducing energy loss and heat accumulation. 4. In the application scenarios of high-frequency and low-loss, it has low coercivity, high magnetic permeability, and low hysteresis loss: First, low coercivity means that the material requires less reverse magnetization energy when the magnetic field changes, which helps to quickly respond to the changes of high-frequency signals. Second, high magnetic permeability enables the material to achieve efficient magnetic flux transmission at a lower magnetic field strength, further improving the energy utilization efficiency. Second, low hysteresis loss reduces the energy loss during the repeated magnetization process of the magnetic field and extends the working life of the device, especially suitable for high-frequency inductors and transformers that require long-term stable operation. 5. Extend the service life of the device: By improving the magnetic permeability of the material and reducing hysteresis loss, the thermal stability and mechanical strength of the device are significantly improved. Specifically, the internal heat conduction path of the material is optimized, and heat can be quickly dissipated, avoiding local overheating. At the same time, the high-strength composite structure can withstand greater stress and vibration, ensuring the long-term reliability of the device in complex environments. In addition, the antioxidant and corrosion-resistant properties of the material are also enhanced, further extending the service life of the device and reducing the maintenance cost. 6. Lightweight, High Strength, and Electromagnetic Shielding: Lightweight and high-strength graphene and magnetic powder are used as fillers, which not only reduce the weight of the material but also maintain good mechanical properties. The two-dimensional structure of graphene endows the material with excellent mechanical strength and flexibility, enabling it to have sufficient support even in a thinner state. At the same time, the presence of magnetic powder enhances the electromagnetic shielding effect of the material, forming a new composite material with the characteristics of lightweight, high strength, and electromagnetic shielding. This material is particularly suitable for fields such as aerospace, automotive electronics, and portable electronic devices, as it can not only reduce weight but also provide reliable electromagnetic protection.

[0014] The technical solutions of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a flowchart of a method for preparing a magnetic composite adhesive according to the present invention; Figure 2 is a comparison chart of ripple processing tests in the test examples of the present invention, where (a) is a ripple test chart using ordinary coating materials; (b) is a ripple test chart using magnetic composite adhesive; Figure 3 is an EMI (electromagnetic interference) test chart in the test examples of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0016] In order to make the objectives, technical solutions, and advantages of the embodiments of the present invention more clearly understood, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the embodiments of the present invention and are not used to limit the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of this application. The examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions throughout.

[0017] It should be noted that the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or server that includes a series of steps or units does not necessarily have to be limited to those clearly listed steps or units, but may include other steps or units that are not clearly listed or are inherent to these processes, methods, products, or devices.

[0018] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0019] A magnetic composite adhesive, the structural feature of the magnetic composite adhesive is a multi-scale heterogeneous interface, and it includes the following components by weight percentage: 15%-30% of epoxy resin matrix, paint or silica gel, 10%-99% of graphene, 30%-60% of magnetic powder, 5%-20% of iron-silicon alloy powder, and 0.5%-1.0% of silane coupling agent; a key interfacial reaction in the composite adhesive generates a chemical bridging structure, and the bonding of the silane coupling agent and the magnetic powder is ≡Si-O-Fe / Si / Al on the surface of Fe / Si / Al particles, where the bond type is a covalent bond and the bond energy is 103.5 eV, that is, Fe 3 Si / FeSiAl magnetic powder, graphene and epoxy resin matrix achieve inorganic-organic interface bridging through Si-O-M covalent bonds (M = Fe / Si / Al). Among them, graphene, as a reinforcing agent of the composite material, provides excellent electrical conductivity and thermal conductivity; the iron-silicon alloy powder has high magnetic permeability and low coercivity, and combined with the good electrical conductivity of graphene, it further improves the electromagnetic properties of the composite material; the magnetic powder is used to improve the magnetic properties of the material.

[0020] Preferably, the purity of graphene is greater than 99.9% and the number of layers is less than 6; the mesh number of the iron-silicon alloy powder is 50 mesh - 300 mesh.

[0021] As Figure 1 shown, a preparation method of a magnetic composite adhesive includes the following steps: S1. Prepare epoxy resin matrix, paint or silica gel, graphene, magnetic powder, iron-silicon alloy powder and silane coupling agent according to the weight components; S2. Ultrasonic mixing: Put the iron-silicon alloy powder and magnetic powder into a sealed constant-temperature ultrasonic tank for ultrasonic dispersion treatment to obtain a composite material; S3. Ball milling treatment: Add silane coupling agent and steel balls to the composite material for ball milling treatment to obtain a powder composite material; S4. Shear emulsification: Add paint, epoxy resin or silica gel to the powder composite material for shear emulsification treatment to obtain a magnetic composite adhesive.

[0022] Preferably, in step S2, the ultrasonic mixing time is 4 h and the temperature is 100 °C.

[0023] Preferably, in step S3, the ball milling treatment time is 4 h, the temperature is 100 °C, and the pH value is 6; In step S3, the silane coupling agent undergoes the following hydrolysis and condensation reactions: .

[0024] In step S4, the shear emulsification time is 6 h; When adding epoxy resin, the following coupling reaction occurs with the amino groups in the powder composite material: .

[0025] Applications of the magnetic composite adhesive in inductor coating, external spraying of transformers, metallization electrodes on ferrite cores, coils, bypass shielding, heat radiation conduction, core encapsulation, electromagnetic shielding, and filters.

[0026] Specifically, the magnetic composite adhesive can be directly coated on the surface of the inductor to form a uniform protective film, producing the following beneficial effects: (1) Improving magnetic flux: Due to the addition of graphene and magnetic powder, the magnetic permeability of the coated inductor is significantly improved, and the magnetic flux increases by more than about 15%, thus improving the working efficiency of the inductor. (2) Reducing eddy current loss: The highly conductive graphene disperses the current path, reduces the eddy current effect, and greatly reduces the energy loss under high-frequency applications. (3) Enhancing mechanical strength: The coating layer not only provides an improvement in electromagnetic performance but also enhances the mechanical strength of the inductor and extends its service life.

[0027] Spraying the magnetic composite adhesive on the surface of the transformer housing forms a uniform and dense coating. This coating not only has good adhesion but also can effectively block the influence of the external environment on the inside of the transformer, with the following beneficial effects: (1) Wide-frequency electromagnetic wave shielding: The coating can absorb and dissipate electromagnetic waves from low frequency to high frequency, preventing external electromagnetic interference from entering the inside of the transformer and ensuring its stable operation. (2) Improving heat dissipation performance: The coating has good heat conduction performance and can quickly dissipate the heat generated during the operation of the transformer, preventing overheating and improving the overall working efficiency. (3) Protection and anti-corrosion: The anti-oxidation and anti-corrosion characteristics of the coating extend the service life of the transformer and reduce the maintenance cost.

[0028] The magnetic composite adhesive is used for the metallization treatment of the surface of the ferrite core. The material is evenly coated on the surface of the core by screen printing or spraying, and then subsequent electroplating or electroless plating of the metal layer is carried out. It has the following beneficial effects: (1) Low coercivity and high magnetic permeability: The low coercivity characteristic of the material makes the core easy to magnetize and demagnetize, improving the response speed; the high magnetic permeability ensures efficient magnetic flux transmission and reduces energy loss. (2) Reducing hysteresis loss: The magnetic composite adhesive effectively reduces the energy consumption of the core during repeated magnetization, improving the efficiency under high-frequency applications. (3) Enhancing the bonding strength: The coating forms a firm bond with the surface of the core, ensuring the long-term stability of the metallization electrode and improving the reliability of the device.

[0029] The magnetic composite adhesive can be used for winding or filling coils, forming a protective film between the coils or inside and outside, playing a role in fixing and supporting. It has the following beneficial effects: (1) Improving insulation performance: The insulation characteristics of the material effectively isolate the electrical connections between the coils, prevent the occurrence of short - circuit phenomena, and improve safety. (2) Enhancing magnetic coupling: The magnetic composite adhesive with high magnetic permeability forms a good magnetic - circuit coupling between the coils, enhancing the magnetic induction intensity and energy - transfer efficiency. (3) Reducing weight and volume: The characteristics of the material being lightweight and high - strength make the coil structure more compact, suitable for miniaturized and lightweight designs.

[0030] The magnetic composite adhesive is applied to key positions of circuit boards or device enclosures, serving as a bypass shielding material to form an effective electromagnetic barrier. It has the following beneficial effects: (1) Wide - band electromagnetic - wave shielding: The material has excellent shielding effectiveness for wide - band electromagnetic waves, can effectively block electromagnetic interference, and ensure the normal operation of electronic devices. (2) Strong anti - interference ability: Even in a complex electromagnetic environment, it can maintain a stable shielding effect, avoiding signal crosstalk and misoperation. (3) Flexible application: The magnetic composite adhesive can be customized in thickness and shape according to actual needs, suitable for various complex bypass - shielding scenarios.

[0031] The magnetic composite adhesive is coated on the surface of heating elements, such as CPUs, power transistors, etc., to help quickly conduct and dissipate heat. It has the following beneficial effects: (1) Efficient heat dissipation: The material has good heat - conduction performance, can quickly conduct heat from the heat source to the heat - dissipation device, prevent local overheating, and improve the heat - dissipation efficiency of the device. (2) Extending service life: By effectively controlling the temperature, it reduces the damage of heating elements caused by overheating and extends their service life. (3) Optimizing thermal management: The magnetic composite adhesive can adjust the coating thickness according to different heating situations to achieve precise thermal management, suitable for high - performance computing and industrial control fields.

[0032] The magnetic composite adhesive is used for encapsulating magnetic cores, wrapping them outside the magnetic cores to form a complete protective shell. It has the following beneficial effects: (1) Enhancing mechanical strength: The encapsulation layer not only protects the magnetic core from physical damage but also enhances the overall structural stability of the magnetic core, improving its anti - impact and vibration resistance. (2) Moisture and corrosion protection: The moisture - proof and corrosion - proof characteristics of the material ensure that the magnetic core can still maintain good performance in a humid or corrosive environment. (3) Simplifying the assembly process: The strong shell formed after the magnetic composite adhesive cures is convenient for assembling the magnetic core with other components, simplifies the production process, and improves production efficiency.

[0033] The magnetic composite glue is coated or sprayed on the outer shell or key internal components of electronic devices to form an effective electromagnetic shielding layer. It has the following beneficial effects: (1) Wide-band electromagnetic wave shielding: The material has excellent shielding effects on electromagnetic waves from low frequency to high frequency, ensuring that the internal circuits of the devices are not affected by external electromagnetic interference. (2) Strong anti-interference ability: In a complex electromagnetic environment, the magnetic composite glue can maintain stable shielding performance, avoiding signal interference and misoperation. (3) Lightweight and flexibility: The lightweight characteristic of the material makes it suitable for electromagnetic shielding requirements of various shapes and sizes, ensuring the shielding effect without increasing the weight of the devices.

[0034] The magnetic composite glue is used for key components of filters, such as magnetic rings, magnetic rods, etc. The material is evenly coated on their surfaces by means of impregnation, spraying or injection molding. It has the following beneficial effects: (1) Improving filtering performance: The high magnetic permeability and low hysteresis loss characteristics of the material enhance the selectivity and attenuation effect of the filter on specific frequency signals, and improve the filtering performance. (2) Reducing energy loss: The low coercivity and low hysteresis loss reduce the energy loss generated by the filter during operation, improving the overall efficiency. (3) Enhancing reliability: The application of the magnetic composite glue improves the mechanical strength and anti-aging performance of the filter, ensuring its stable and reliable performance during long-term use.

[0035] Test example In this test example, the verification of the improvement effect of the magnetic composite glue on the circuit stability, filtering and reduction of ripples is carried out.

[0036] The magnetic composite glue described in the present invention and ordinary coating materials are respectively coated on a 40 nH inductor, and the filtering unit is connected in series in the AC - DC circuit. The filtering effects at different times are recorded, and the results are as Figure 2 shown. It can be seen that for the filtering unit coated with the magnetic composite glue, the ripple processing is significantly improved. From the data, the average value of the ripples is significantly reduced, such as from 27.0 mV to 35.9 μV; from the graphical characteristics, the width of the energy concentration area changes, and the width at the output is wider than that at the input; while for the filtering unit with ordinary coating, there is no obvious change in the ripple filtering effect and the width of the energy concentration area. This shows that the magnetic composite glue described in the present invention has a positive effect on the ripple processing of electronic circuits, can effectively reduce the ripple voltage, and optimize the stability of the circuit.

[0037] As Figure 3 shown, after using the magnetic composite glue, the electromagnetic radiation is below the standard limit line, proving that the magnetic composite glue described in the present invention can effectively suppress the electromagnetic radiation of electronic devices.

[0038] Example 1: Example of low-loss high-frequency application 1. Material preparation: Epoxy resin matrix 15%; Graphene 99%; Magnetic powder 30%; Iron-silicon alloy powder 5%; Silane coupling agent 1%; 2. Ultrasonic mixing: Load the iron-silicon alloy powder and magnetic powder into a sealed constant-temperature ultrasonic tank, and perform ultrasonic dispersion treatment at 100°C for 4 hours to obtain a composite material.

[0039] 3. Ball milling treatment: Add the silane coupling agent and steel balls to the composite material, and perform ball milling treatment at 100°C and a pH value of 6 for 4 hours to obtain a powder composite material.

[0040] 4. Shear emulsification: Add the epoxy resin matrix to the powder composite material, and perform shear emulsification treatment in a high-speed emulsifying shear machine for 6 hours to obtain a magnetic composite adhesive.

[0041] Application fields: External spraying of high-frequency inductors, transformers or inductor coating.

[0042] Performance characteristics: (1) The magnetic flux is increased by about 15% or more; (2) It has excellent broadband electromagnetic wave shielding efficiency; (3) Eddy current loss is reduced, and the efficiency under high-frequency applications is improved.

[0043] Example 2: Example of medium-loss medium-frequency application 1. Material preparation: Epoxy resin matrix 25%; Graphene 50%; Magnetic powder 45%; Iron-silicon alloy powder 10%; Silane coupling agent 0.5%; 2. Ultrasonic mixing: Load the iron-silicon alloy powder and magnetic powder into a sealed constant-temperature ultrasonic tank, and perform ultrasonic dispersion treatment at 100°C for 4 hours to obtain a composite material.

[0044] 3. Ball milling treatment: Add the silane coupling agent and steel balls to the composite material, and perform ball milling treatment at 100°C and a pH value of 6 for 4 hours to obtain a powder composite material.

[0045] 4. Shear emulsification: Add the epoxy resin matrix to the powder composite material, and perform shear emulsification treatment in a high-speed emulsifying shear machine for 6 hours to obtain a magnetic composite adhesive.

[0046] Application fields: Filters, electromagnetic shielding materials or coil winding.

[0047] Performance characteristics: (1) Balanced magnetic permeability and loss, suitable for medium-frequency applications; (2) Has certain electromagnetic wave shielding ability; (3) Moderate mechanical strength and thermal stability.

[0048] Example 3: Example of high-strength low-frequency application 1. Material preparation: Epoxy resin matrix 30%; Graphene 10%; Magnetic powder 60% Iron-silicon alloy powder 20%; Silane coupling agent 0.5%; 2. Ultrasonic mixing: Load the iron-silicon alloy powder and magnetic powder into a sealed constant-temperature ultrasonic tank, and perform ultrasonic dispersion treatment at 100 °C for 4 hours to obtain a composite material.

[0049] 3. Ball milling treatment: Add a silane coupling agent and steel balls to the composite material, and perform ball milling treatment at 100 °C and a pH value of 6 for 4 hours to obtain a powder composite material.

[0050] 4. Shear emulsification: Add an epoxy resin matrix to the powder composite material, and perform shear emulsification treatment in a high-speed emulsifying shear machine for 6 hours to obtain a magnetic composite adhesive.

[0051] Application fields: Low-frequency inductors, magnetic core encapsulation or bypass shielding.

[0052] Performance characteristics: (1) It has high magnetic permeability and low coercivity, suitable for low-frequency applications; (2) High strength and high mechanical stability, suitable for occasions that need to withstand large stresses; (3) Moderate electromagnetic shielding effectiveness, meeting general low-frequency electromagnetic shielding requirements.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A magnetic composite adhesive, characterized in that: The structural feature of the magnetic composite adhesive is a multi-scale heterogeneous interface, which includes the following components by weight percentage: 15%-30% epoxy resin matrix, paint or silicone, 10%-99% graphene, 30%-60% magnetic powder, 5%-20% iron-silicon alloy powder and 0.5%-1.0% silane coupling agent; The key interface reaction in the composite adhesive generates a chemical bridging structure, and the bonding between the silane coupling agent and the magnetic powder is Fe / Si / Al particle surface ≡Si-O-Fe / Si / Al, where the bond type is covalent bond and the bond energy is 103.5eV.

2. The magnetic composite adhesive according to claim 1, characterized in that: The purity of graphene is greater than 99.9%, and the number of layers is less than 6; the mesh size of iron silicon alloy powder is 50 mesh-300 mesh.

3. A method for preparing a magnetic composite adhesive as claimed in claim 1 or 2, characterized in that: The following steps are involved: S1. Prepare epoxy resin matrix, paint or silicone, graphene, magnetic powder, iron-silicon alloy powder and silane coupling agent according to weight components; S2, ultrasonic mixing: the iron-silicon alloy powder and the magnetic powder are placed in a sealed constant temperature ultrasonic tank and subjected to ultrasonic dispersion treatment to obtain a composite material; S3, ball milling treatment: adding a silane coupling agent and steel balls to the composite material, and performing ball milling treatment to obtain a powder composite material; S4. Shear emulsification: Add paint, epoxy resin or silicone to the powder composite material and perform shear emulsification treatment to obtain a magnetic composite adhesive.

4. The method for preparing a magnetic composite adhesive according to claim 3, characterized in that: In step S2, the ultrasonic mixing time is 4 hours and the temperature is 100°C.

5. The method for preparing a magnetic composite adhesive according to claim 3, characterized in that: In step S3, the ball milling time is 4 h, the temperature is 100° C., and the pH value is 6; In step S3, a silane coupling agent The following hydrolysis and condensation reactions occur: 。 6. The method for preparing a magnetic composite adhesive according to claim 3, characterized in that: In step S4, the shear emulsification time is 6 h; When epoxy resin is added, the following coupling reaction occurs with the amino groups in the powder composite material: 。 7. Application of a magnetic composite adhesive in inductor coating, transformer external spraying, metallized electrodes on ferrite cores, coils, bypass shielding, thermal radiation conduction, core packaging, electromagnetic shielding and filters.

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