High-thermal-conductivity pouring sealant based on modified nitrogen-doped graphene as well as preparation method and application of high-thermal-conductivity pouring sealant

Abstract

The invention discloses a high-thermal-conductivity pouring sealant based on modified nitrogen-doped graphene as well as a preparation method and application of the high-thermal-conductivity pouring sealant, and belongs to the technical field of pouring sealants. The pouring sealant comprises a pouring sealant matrix and modified nitrogen-doped graphene, wherein the pouring sealant matrix comprises 50-85 parts of matrix resin, 1-10 parts of a filler, 1-5 parts of a flexibilizer and 10-30 parts of a solvent; the modified nitrogen-doped graphene is prepared by the following steps: uniformly adsorbing manganese carbonate in nitrogen-doped graphene, treating in a high-temperature reducing atmosphere, uniformly distributing lithium fluosilicate in the nitrogen-doped graphene, and finally sintering. The nitrogen-doped graphene is pretreated by adopting manganese carbonate and lithium fluosilicate, so that the dispersity and the compatibility with a resin matrix of the nitrogen-doped graphene are effectively improved, the heat-conducting property, the tensile strength, the hardness and the heat stability of the pouring sealant are improved, the construction performance is good, the nitrogen-doped graphene can stably work in a high-temperature and high-power environment, and the service life of the pouring sealant is prolonged. And the packaging method can be widely applied to packaging of the vehicle-mounted charger transformer of the electric vehicle.

Description

Technical Field

[0001] This invention belongs to the field of potting compound technology, specifically relating to a high thermal conductivity potting compound based on modified nitrogen-doped graphene, its preparation method, and its application. Background Technology

[0002] The electronic control system of electric vehicles, including the on-board charger (OBC) transformer, is one of the core electronic components of electric vehicles. Thermal management is crucial in high-power-density OBC transformers. Ineffective heat dissipation can lead to overheating and even damage to electronic components. Therefore, designing a potting compound with high thermal conductivity, good electrical insulation, resistance to high and low temperatures, and anti-aging properties to improve the operational reliability and lifespan of the OBC transformer is key to solving this problem.

[0003] Currently, commercially available silicone thermally conductive potting compounds primarily achieve their thermal conductivity by adding micron-sized inorganic thermally conductive fillers, such as alumina, aluminum nitride, and silicon carbide, to the resin matrix. However, this traditional approach has significant drawbacks: First, to achieve a high thermal conductivity (typically >4 W / m·K), the amount of inorganic filler added often needs to reach over 70 wt%. Such a high filler content leads to a sharp increase in the viscosity of the potting compound, resulting in poor flowability. During actual potting, it easily traps air bubbles, forming pores and negatively impacting thermal conductivity and insulation performance. Second, a high proportion of rigid inorganic fillers severely compromises the original flexibility of the silicone material, leading to increased modulus, increased hardness, and decreased flexibility in the cured compound. This makes it prone to cracking under long-term thermal shock, compromising the long-term reliability of electronic devices. Furthermore, the poor interfacial compatibility between inorganic fillers and the silicone matrix, along with severe phonon mismatch, results in high interfacial thermal resistance, limiting further improvements in thermal conductivity.

[0004] In recent years, to overcome the aforementioned bottlenecks of traditional fillers, researchers have begun to focus on novel carbon materials with intrinsically high thermal conductivity. Among them, nitrogen-doped graphene has gradually become an ideal thermally conductive filler material due to its excellent thermal conductivity, good mechanical properties, and thermal stability. Nitrogen-doped graphene alters the electronic structure and polarity of the graphene surface by introducing nitrogen into the six-membered rings of graphene.

[0005] Theoretically, nitrogen atoms (such as pyridine nitrogen and pyrrole nitrogen) form polar sites in the structure of graphene, enabling them to chemically interact with functional groups in the organosilicon matrix, thereby improving interfacial bonding and promoting cross-linking. However, in practice, we have found that simply adding nitrogen-doped graphene as a single filler directly to the matrix resin does not achieve the expected results. The main reason is that nitrogen-doped graphene has a huge specific surface area and extremely strong van der Waals forces. Even with surface polarity, it is still prone to severe agglomeration and stacking in low-viscosity liquid matrix resins. This agglomeration not only fails to form an effective, continuous thermally conductive network, but also creates thermally conductive "islands" and stress concentration points within the material, offering very limited improvement to thermal conductivity and mechanical properties, and may even have negative effects. Furthermore, the introduction of nanosheet materials, even at low addition levels, can lead to a significant increase in system viscosity, posing challenges to processing applications.

[0006] Therefore, existing technologies, whether employing traditional methods with large quantities of micron-sized inorganic fillers or simply using emerging nitrogen-doped graphene materials, have failed to perfectly balance the relationship between thermal conductivity, mechanical properties, and processability. How to effectively suppress the aggregation of nitrogen-doped graphene in the matrix resin and synergistically compound it with traditional fillers to construct a highly efficient thermally conductive network has become a pressing technical challenge in this field. Summary of the Invention

[0007] The purpose of this invention is to provide a high thermal conductivity potting compound based on modified nitrogen-doped graphene, its preparation method and application. It has good thermal conductivity, tensile strength, hardness and thermal stability, good construction performance, and can work stably in high temperature and high power environments, with broad application prospects.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A high thermal conductivity potting compound based on modified nitrogen-doped graphene is provided, comprising a potting compound matrix and modified nitrogen-doped graphene; wherein: By weight, the potting compound matrix comprises 50-85 parts of matrix resin, 1-10 parts of filler, 1-5 parts of toughening agent, and 10-30 parts of solvent; The modified nitrogen-doped graphene is obtained by pretreating nitrogen-doped graphene with manganese carbonate and lithium fluorosilicate. Specifically, manganese carbonate is uniformly adsorbed in nitrogen-doped graphene and then treated under a high-temperature reducing atmosphere to reduce manganese carbonate (MnCO3) to elemental manganese (Mn). Then, lithium fluorosilicate is uniformly distributed in nitrogen-doped graphene and finally sintered to obtain modified nitrogen-doped graphene. The nitrogen-doped graphene accounts for 0.5-3.5% of the mass of the potting compound matrix; the mass ratio of nitrogen-doped graphene, manganese carbonate and lithium fluorosilicate is 1:0.01-0.1:0.02-0.2.

[0009] According to the above scheme, the nitrogen-doped graphene accounts for 1-2.5% of the mass of the potting compound matrix.

[0010] According to the above scheme, the preparation of modified nitrogen-doped graphene specifically includes the following steps: 1) Mix the ethanol solution of manganese carbonate with the nitrogen-doped graphene dispersion to ensure that the manganese source fully wets the nitrogen-doped graphene. Then, treat it under a high-temperature reducing atmosphere to reduce manganese carbonate (MnCO3) to elemental manganese (Mn) to obtain manganese-containing nitrogen-doped graphene. 2) Immerse the manganese-containing nitrogen-doped graphene obtained in step 1) in an ethanol solution of lithium fluorosilicate to ensure that the lithium fluorosilicate is uniformly distributed in the nitrogen-doped graphene; then vacuum dry and finally sinter to obtain modified nitrogen-doped graphene containing manganese oxide and lithium fluorosilicate.

[0011] Preferably, in step 1), the solvent in the nitrogen-doped graphene dispersion is acetone.

[0012] Preferably, in step 1), the concentration of the ethanol solution of manganese carbonate is 0.05-0.5M; and the concentration of the nitrogen-doped graphene dispersion is 2-13 wt%.

[0013] Preferably, in step 1), the mixing time between the ethanol solution of manganese carbonate and the nitrogen-doped graphene dispersion is 0.5-6 hours.

[0014] Preferably, in step 1), the treatment is carried out under a high-temperature reducing atmosphere, specifically using a hydrogen reducing atmosphere at a temperature of 400-600℃ for 0.5-6 hours.

[0015] Preferably, in step 2), the concentration of the lithium fluorosilicate ethanol solution is 0.05-0.5M.

[0016] Preferably, in step 2), the soaking time is 0.5-6 hours.

[0017] Preferably, in step 2), the vacuum drying process is: drying at 30-60℃ for 3-24 hours.

[0018] Preferably, in step 2), the sintering process is: sintering at 400-500℃ for 0.5-6 hours.

[0019] According to the above scheme, the nitrogen doping content in the nitrogen-doped graphene is 0.5-3% by atomic percentage.

[0020] According to the above scheme, the nitrogen-doped graphene is prepared by chemical vapor deposition (CVD), ammonia treatment or other nitrogen doping methods.

[0021] According to the above scheme, the specific surface area of ​​the nitrogen-doped graphene is 200-700 m². 2 / g, preferably 400-600m 2 / g.

[0022] According to the above scheme, the particle size of the nitrogen-doped graphene is 1nm-10μm, preferably 10-500nm.

[0023] According to the above scheme, the thermal conductivity of the potting compound at room temperature is greater than 2.0 W / m·K, preferably 4-5 W / m·K.

[0024] According to the above scheme, the matrix resin is one or more of epoxy resin, polyurethane resin, silicone resin or acrylic resin.

[0025] According to the above scheme, the matrix resin is 60-75 parts, the filler is 5-8 parts, and the solvent is 15-20 parts.

[0026] According to the above scheme, the filler is a thermally conductive reinforcing material such as silicon dioxide, aluminum powder, or carbon fiber.

[0027] According to the above scheme, the toughening agent is polyurethane, rubber, or silicone rubber.

[0028] According to the above scheme, the solvent is cyclohexene, benzene, or acetone.

[0029] A method for preparing the above-mentioned high thermal conductivity potting compound based on modified nitrogen-doped graphene is provided, comprising the following steps: 1) Mix the matrix resin and solvent evenly, then add the filler and mix evenly, and finally add the toughening agent and continue to mix evenly; 2) Disperse the modified nitrogen-doped graphene in acetone, and then add it to the resin mixture obtained in step 1), and stir until homogeneous; 3) The mixture obtained in step 2) is subjected to vacuum degassing treatment to obtain a high thermal conductivity silicone potting compound.

[0030] According to the above scheme, in step 2), the stirring time is 1-3 hours.

[0031] According to the above scheme, in step 2), the concentration of the modified nitrogen-doped graphene dispersed in acetone is 2-13%.

[0032] According to the above scheme, in step 3), the vacuum degassing time is 10-60 min.

[0033] This invention provides an application of the aforementioned high thermal conductivity potting compound based on modified nitrogen-doped graphene in the encapsulation of OBC transformers for electric vehicles.

[0034] The beneficial effects of this invention are as follows: 1. This invention provides a high thermal conductivity potting compound based on modified nitrogen-doped graphene. The modified nitrogen-doped graphene is obtained by pretreating nitrogen-doped graphene with manganese carbonate and lithium fluorosilicate. Manganese carbonate in the form of manganese oxide and lithium fluorosilicate are sequentially attached to the nitrogen-doped graphene, synergistically improving the dispersibility of nitrogen-doped graphene and its compatibility with the resin matrix. This effectively improves the thermal conductivity, tensile strength, hardness and thermal stability of the potting compound, and it also has good workability. It can work stably in high temperature and high power environments and has broad application prospects.

[0035] 2. The high thermal conductivity potting compound of the present invention can effectively improve thermal conductivity, mechanical properties and durability by introducing a small amount of modified nitrogen-doped graphene, while significantly reducing the amount of filler used.

[0036] 3. The high thermal conductivity potting compound of the present invention is used for encapsulation of on-board charger (OBC) transformers for electric vehicles, and has high thermal conductivity, electrical insulation, high and low temperature resistance and long-term thermal aging stability.

[0037] 4. The present invention also provides a method for preparing the above-mentioned high thermal conductivity potting compound. The preparation method is simple, the conditions are mild, and it has prospects for industrial application. Attached Figure Description

[0038] Figure 1 This is a comparison of the Raman spectra of graphene and nitrogen-doped graphene used in the embodiments of the present invention.

[0039] Figure 2 Here are scanning electron microscope (SEM) images of the nitrogen-doped graphene used in the embodiments of the present invention; wherein: Figure 2 a is a transmission electron microscope image of nitrogen-doped graphene, with the arrow pointing to the nitrogen-doping sites; Figure 2 b is a transmission electron microscope (TEM) image of nitrogen-doped graphene, showing its unit cell structure. Figure 2 c is a scanning electron microscope image of nitrogen-doped graphene, showing its carbon framework structure. Detailed Implementation

[0040] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0041] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0042] The performance specifications of the nitrogen-doped graphene used in the examples and comparative examples are as follows: nitrogen doping content of 1.5%; particle size of 300 nanometers; specific surface area of ​​450 m². 2 / g.

[0043] Example 1 A high thermal conductivity potting compound based on modified nitrogen-doped graphene is provided, the raw materials including a potting compound matrix and modified nitrogen-doped graphene; wherein: By weight, the potting compound matrix comprises 60 parts epoxy resin, 5 parts silica, 5 parts polyurethane toughening agent, and 15 parts cyclohexene. The modified nitrogen-doped graphene was obtained by pretreating nitrogen-doped graphene with manganese carbonate and lithium fluorosilicate; the nitrogen-doped graphene accounted for 0.6% of the mass of the potting compound matrix; the mass ratio of nitrogen-doped graphene, manganese carbonate and lithium fluorosilicate was 1:0.1:0.2.

[0044] The above-mentioned method for preparing modified nitrogen-doped graphene includes the following steps: 1) Dispersion of nitrogen-doped graphene: Nitrogen-doped graphene was ultrasonically dispersed in acetone at a concentration of 3 wt%. The dispersion time was 45 min to ensure that the nitrogen-doped graphene was completely and uniformly dispersed in acetone and to avoid agglomeration, thus obtaining a nitrogen-doped graphene dispersion.

[0045] 2) Introduction of elemental manganese: Manganese carbonate (MnCO3) was dissolved in ethanol to prepare a homogeneous solution with a concentration of 0.05 M. The nitrogen-doped graphene dispersion obtained in step 1) was added to the manganese carbonate solution to ensure that the manganese source fully wetted the nitrogen-doped graphene. The impregnation time was 4 hours to ensure that the manganese was uniformly adsorbed on the nitrogen-doped graphene. The impregnated nitrogen-doped graphene was placed in a tube furnace and heated to 500°C in a hydrogen atmosphere and held for 5 hours. During this process, manganese carbonate was reduced to elemental manganese (Mn) and interacted with the surface of the nitrogen-doped graphene.

[0046] 3) Introduction of Lithium Fluorosilicate: Lithium fluorosilicate (Li₂SiF₆) was dissolved in ethanol at a concentration of 0.1 M. The solution was stirred until completely dissolved to form a homogeneous solution. The manganese-containing nitrogen-doped graphene sample obtained in step 2) was immersed in the lithium fluorosilicate solution for 2 hours. This ensures that the lithium fluorosilicate is uniformly distributed on the graphene surface and in the pores. The immersed sample was then removed and dried in a vacuum drying oven at 60°C for 12 hours to remove the ethanol solvent. To enhance the bonding force between lithium fluorosilicate and graphene, the dried sample was sintered at 450°C for a short time (2 hours) to further solidify the lithium fluorosilicate and enhance its bonding with the nitrogen-doped graphene.

[0047] The preparation method of the above-mentioned high thermal conductivity potting compound based on modified nitrogen-doped graphene includes the following steps: 1) Preparation of the potting compound matrix: Mix 60 parts of epoxy resin with 15 parts of cyclohexene solvent and stir until homogeneous. Add 5 parts of silica filler to the resin solution and stir until homogeneous, ensuring uniform distribution of the filler. Add 5 parts of polyurethane toughening agent to the mixture and continue stirring to ensure full reaction between the toughening agent and the resin matrix.

[0048] 2) The modified nitrogen-doped graphene was dispersed in acetone to a dispersion concentration of 3 wt%; then slowly added to the resin matrix and mixed uniformly by mechanical stirring (1200 rpm). The stirring time was 1 hour to ensure that the nitrogen-doped graphene and the resin matrix were fully integrated to form a uniform thermally conductive potting compound system.

[0049] 3) Place the mixture in a vacuum degassing machine and perform vacuum degassing treatment for 30 minutes to obtain a high thermal conductivity potting compound based on modified nitrogen-doped graphene.

[0050] Example 2 A high thermal conductivity potting compound based on modified nitrogen-doped graphene is provided, the raw materials including a potting compound matrix and modified nitrogen-doped graphene; wherein: By weight, the potting compound matrix comprises 60 parts epoxy resin, 5 parts silica, 5 parts polyurethane toughening agent, and 15 parts cyclohexene. The modified nitrogen-doped graphene was obtained by pretreating nitrogen-doped graphene with manganese carbonate and lithium fluorosilicate; the nitrogen-doped graphene accounted for 1.2% of the mass of the potting compound matrix; the mass ratio of nitrogen-doped graphene, manganese carbonate and lithium fluorosilicate was 1:0.05:0.1.

[0051] The above-mentioned method for preparing modified nitrogen-doped graphene includes the following steps: 1) Dispersion of nitrogen-doped graphene: Nitrogen-doped graphene was ultrasonically dispersed in acetone at a concentration of 6 wt%. The dispersion time was 45 min to ensure that the nitrogen-doped graphene was completely and uniformly dispersed in acetone and to avoid agglomeration, thus obtaining a nitrogen-doped graphene dispersion.

[0052] 2) Introduction of elemental manganese: Same as in Example 1.

[0053] 3) Introduction of lithium fluorosilicate: Same as in Example 1.

[0054] The preparation method of the above-mentioned high thermal conductivity potting compound based on modified nitrogen-doped graphene includes the following steps: 1) Preparation of the potting compound matrix: Mix 60 parts of epoxy resin with 15 parts of cyclohexene solvent and stir until homogeneous. Add 5 parts of silica filler to the resin solution and stir until homogeneous, ensuring uniform distribution of the filler. Add 5 parts of polyurethane toughening agent to the mixture and continue stirring to ensure full reaction between the toughening agent and the resin matrix.

[0055] 2) The modified nitrogen-doped graphene was dispersed in acetone to a dispersion concentration of 6 wt%; then slowly added to the resin matrix and mixed uniformly by mechanical stirring (1200 rpm). The stirring time was 1 hour to ensure that the nitrogen-doped graphene and the resin matrix were fully integrated to form a uniform thermally conductive potting compound system.

[0056] 3) Place the mixture in a vacuum degassing machine and perform vacuum degassing treatment for 30 minutes to obtain a high thermal conductivity potting compound based on modified nitrogen-doped graphene.

[0057] The preparation methods of modified nitrogen-doped graphene and potting compound are the same as in Example 1; wherein nitrogen-doped graphene and

[0058] Example 3 A high thermal conductivity potting compound based on modified nitrogen-doped graphene is provided, the raw materials including a potting compound matrix and modified nitrogen-doped graphene; wherein: By weight, the potting compound matrix comprises 60 parts epoxy resin, 5 parts silica, 5 parts polyurethane toughening agent, and 15 parts cyclohexene. The modified nitrogen-doped graphene was obtained by pretreating the nitrogen-doped graphene with manganese carbonate and lithium fluorosilicate; the nitrogen-doped graphene accounted for 2.5% of the mass of the potting compound matrix; the mass ratio of nitrogen-doped graphene, manganese carbonate and lithium fluorosilicate was 1:0.025:0.05.

[0059] The above-mentioned method for preparing modified nitrogen-doped graphene includes the following steps: 1) Dispersion of nitrogen-doped graphene: Nitrogen-doped graphene was ultrasonically dispersed in acetone to a dispersion concentration of 12.5 wt%. The dispersion time was 45 min to ensure that the nitrogen-doped graphene was completely and uniformly dispersed in acetone and to avoid agglomeration, thus obtaining a nitrogen-doped graphene dispersion.

[0060] 2) Introduction of elemental manganese: Same as in Example 1.

[0061] 3) Introduction of lithium fluorosilicate: Same as in Example 1.

[0062] The preparation method of the above-mentioned high thermal conductivity potting compound based on modified nitrogen-doped graphene includes the following steps: 1) Preparation of the potting compound matrix: Mix 60 parts of epoxy resin with 15 parts of cyclohexene solvent and stir until homogeneous. Add 5 parts of silica filler to the resin solution and stir until homogeneous, ensuring uniform distribution of the filler. Add 5 parts of polyurethane toughening agent to the mixture and continue stirring to ensure full reaction between the toughening agent and the resin matrix.

[0063] 2) The modified nitrogen-doped graphene was dispersed in acetone to a dispersion concentration of 12.5 wt%. This dispersion was then slowly added to the resin matrix, and the mixture was kept homogeneous by mechanical stirring (1200 rpm). The stirring time was 1 hour to ensure that the nitrogen-doped graphene and the resin matrix were fully integrated to form a uniform thermally conductive potting compound system.

[0064] 3) Place the mixture in a vacuum degassing machine and perform vacuum degassing treatment for 30 minutes to obtain a high thermal conductivity potting compound based on modified nitrogen-doped graphene.

[0065] Comparative Example 1 The specific implementation is the same as in Example 1, except that nitrogen-doped graphene is replaced with graphene.

[0066] Comparative Example 2 The specific implementation is the same as in Example 2, except that nitrogen-doped graphene is replaced with graphene.

[0067] Comparative Example 3 The specific implementation is the same as in Example 3, except that nitrogen-doped graphene is replaced with graphene.

[0068] Comparative Example 4 A thermally conductive potting compound is provided, comprising, by weight parts, 60 parts epoxy resin, 5 parts silica, 5 parts polyurethane toughening agent, 15 parts cyclohexene, and 15 parts acetone; it does not contain modified nitrogen-doped graphene.

[0069] The preparation method of thermally conductive potting compound includes the following steps: 1) Preparation of the potting compound matrix: Mix 60 parts epoxy resin with 15 parts cyclohexene and 15 parts acetone solvent, and stir until homogeneous. Add 5 parts silica filler to the resin solution and stir until homogeneous, ensuring uniform distribution of the filler. Add 5 parts polyurethane toughening agent to the mixture and continue stirring to ensure full reaction between the toughening agent and the resin matrix.

[0070] 2) Mix the resin matrix thoroughly using mechanical stirring (1000 rpm to 1500 rpm). Stir for 1 hour to ensure the resin matrix is ​​fully integrated and forms a uniform thermally conductive potting compound system.

[0071] 3) Place the mixture in a vacuum degassing machine and perform vacuum degassing treatment for 30 minutes to obtain thermally conductive potting compound.

[0072] Comparative Example 5 A thermally conductive potting compound is provided, the raw materials of which include a potting compound matrix and modified nitrogen-doped graphene; wherein: By weight, the potting compound matrix comprises 60 parts epoxy resin, 5 parts silica, 5 parts polyurethane toughening agent, and 15 parts cyclohexene. The modified nitrogen-doped graphene was obtained by pretreating the nitrogen-doped graphene with lithium fluorosilicate; the nitrogen-doped graphene accounted for 0.6% of the mass of the potting compound matrix; the mass ratio of nitrogen-doped graphene to lithium fluorosilicate was 1:0.2.

[0073] The above-mentioned method for preparing modified nitrogen-doped graphene includes the following steps: 1) Dispersion of nitrogen-doped graphene: Nitrogen-doped graphene was ultrasonically dispersed in acetone at a concentration of 3 wt%. The dispersion time was 45 min to ensure that the nitrogen-doped graphene was completely and uniformly dispersed in acetone and to avoid agglomeration, thus obtaining a nitrogen-doped graphene dispersion.

[0074] 2) Introduction of Lithium Fluorosilicate: Lithium fluorosilicate (Li₂SiF₆) was dissolved in the nitrogen-doped graphene dispersion obtained in step 1), and the impregnation time was controlled to be 2 hours. This ensures that the lithium fluorosilicate is uniformly distributed on the graphene surface and in the pores. The impregnated sample was taken out and dried in a vacuum drying oven at 60°C for 12 hours to remove the ethanol solvent. To enhance the bonding force between lithium fluorosilicate and graphene, the dried sample was sintered at 450°C for a short time (2 hours) to further solidify the lithium fluorosilicate and enhance its bonding with the nitrogen-doped graphene.

[0075] The preparation method of the above-mentioned thermally conductive potting compound includes the following steps: 1) Preparation of the potting compound matrix: Mix 60 parts of epoxy resin with 15 parts of cyclohexene solvent and stir until homogeneous. Add 5 parts of silica filler to the resin solution and stir until homogeneous, ensuring uniform distribution of the filler. Add 5 parts of polyurethane toughening agent to the mixture and continue stirring to ensure full reaction between the toughening agent and the resin matrix.

[0076] 2) The modified nitrogen-doped graphene was dispersed in acetone to a dispersion concentration of 3 wt%; then slowly added to the resin matrix and mechanically stirred (1200 rpm) to maintain uniform mixing. The stirring time was 1 hour to ensure that the nitrogen-doped graphene and the resin matrix were fully integrated to form a uniform thermally conductive potting compound system.

[0077] 3) Place the mixture in a vacuum degassing machine and perform vacuum degassing treatment for 30 minutes to obtain thermally conductive potting compound.

[0078] Comparative Example 6 A thermally conductive potting compound is provided, the raw materials of which include a potting compound matrix and modified nitrogen-doped graphene; wherein: By weight, the potting compound matrix comprises 60 parts epoxy resin, 5 parts silica, 5 parts polyurethane toughening agent, and 15 parts cyclohexene. The modified nitrogen-doped graphene was obtained by pretreating nitrogen-doped graphene with manganese carbonate; the nitrogen-doped graphene accounted for 0.6% of the mass of the potting compound matrix; the mass ratio of nitrogen-doped graphene to manganese carbonate was 1:0.1.

[0079] The above-mentioned method for preparing modified nitrogen-doped graphene includes the following steps: 1) Dispersion of nitrogen-doped graphene: Nitrogen-doped graphene was ultrasonically dispersed in acetone at a concentration of 3 wt%. The dispersion time was 45 min to ensure that the nitrogen-doped graphene was completely and uniformly dispersed in acetone and to avoid agglomeration, thus obtaining a nitrogen-doped graphene dispersion.

[0080] 2) Introduction of elemental manganese: Manganese carbonate (MnCO3) was dissolved in ethanol to prepare a homogeneous solution. The concentration was controlled at 0.05 M. The nitrogen-doped graphene dispersion obtained in step 1) was added to the manganese carbonate solution to ensure that the manganese source fully wetted the nitrogen-doped graphene. The impregnation time was 4 hours to ensure that the manganese was uniformly adsorbed on the graphene surface. The impregnated graphene was placed in a tube furnace and heated to 500°C in a hydrogen atmosphere and maintained for 5 hours. During this process, manganese carbonate was reduced to elemental manganese (Mn) and interacted with the surface of the nitrogen-doped graphene.

[0081] The preparation method of the above-mentioned high thermal conductivity potting compound based on modified nitrogen-doped graphene includes the following steps: 1) Preparation of the potting compound matrix: Mix 60 parts of epoxy resin with 15 parts of cyclohexene solvent and stir until homogeneous. Add 5 parts of silica filler to the resin solution and stir until homogeneous, ensuring uniform distribution of the filler. Add 5 parts of polyurethane toughening agent to the mixture and continue stirring to ensure full reaction between the toughening agent and the resin matrix.

[0082] 2) The modified nitrogen-doped graphene was dispersed in acetone to a dispersion concentration of 3 wt%; then slowly added to the resin matrix and mechanically stirred (1200 rpm) to maintain uniform mixing. The stirring time was 1 hour to ensure that the nitrogen-doped graphene and the resin matrix were fully integrated to form a uniform thermally conductive potting compound system.

[0083] 3) Place the mixture in a vacuum degassing machine and perform vacuum degassing treatment for 30 minutes to obtain thermally conductive potting compound.

[0084] Performance testing: Thermal conductivity testing: Thermal conductivity was tested using the laser flash method or steady-state method, conforming to ASTM E1952 standard. The effect of different amounts of graphene (nitrogen-doped and pure graphene) on thermal conductivity was measured.

[0085] Tensile strength test: The effect of different components on the tensile strength of the material was tested using a tensile testing machine according to ASTM D412 standard.

[0086] Thermal stability testing: Thermogravimetric analysis (TGA) was used in accordance with ASTM D6370 to evaluate the thermal stability of different components.

[0087] Electrical insulation performance test: resistivity test is used to test electrical insulation according to IEC 60093 standard.

[0088] Viscosity testing: The rheological properties of different components were tested using a rotational viscometer (Brookfield Viscometer) in accordance with ISO 2555 standards.

[0089] Coefficient of thermal expansion (CTE) test: Thermomechanical analysis (TMA) or laser interferometer (LDA) methods are used to test the thermal expansion characteristics of different formulations, in accordance with ASTM D3386 standard.

[0090] Table 1. Performance tests of Examples 1-3 and Comparative Examples 1-6

[0091] As shown in Table 1: In Examples 1-3, the thermal conductivity, mechanical properties and thermal stability of the potting compound were significantly improved by adding nitrogen-doped graphene modified with manganese carbonate and lithium fluorosilicate. The thermal conductivity can reach as high as 4.9 W / m·K, which is excellent.

[0092] In Comparative Examples 1-3, the nitrogen-doped graphene in Examples 1-3 was replaced with graphene, and the relevant performance all declined. Figure 1 This demonstrates the difference in energy absorption capabilities between graphene and nitrogen-doped graphene.

[0093] Comparative Example 4 only had a potting compound matrix and no modified nitrogen-doped graphene, resulting in a significant deterioration in related performance.

[0094] In Comparative Examples 5 and 6, manganese carbonate and lithium fluorosilicate were omitted from Example 1, respectively, and the thermal conductivity decreased by 43% and 13%, respectively, indicating that manganese carbonate and lithium fluorosilicate have a good synergistic effect in modifying nitrogen-doped graphene.

[0095] As can be seen from the above, the potting compound obtained by the present invention has excellent performance and can exhibit excellent comprehensive performance such as heat dissipation, mechanical properties, and thermal stability in the application of high-power electronic devices, thus meeting the industry's high requirements for thermally conductive materials.

[0096] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high thermal conductivity potting compound based on modified nitrogen-doped graphene, characterized in that, The high thermal conductivity potting compound comprises a potting compound matrix and modified nitrogen-doped graphene; wherein: By weight, the potting compound matrix comprises 50-85 parts of matrix resin, 1-10 parts of filler, 1-5 parts of toughening agent, and 10-30 parts of solvent; The modified nitrogen-doped graphene is obtained by pretreating nitrogen-doped graphene with manganese carbonate and lithium fluorosilicate. Specifically, manganese carbonate is uniformly adsorbed in nitrogen-doped graphene and treated under a high-temperature reducing atmosphere; then lithium fluorosilicate is uniformly distributed in nitrogen-doped graphene, and finally sintered to obtain modified nitrogen-doped graphene. The nitrogen-doped graphene accounts for 0.5-3.5% of the mass of the potting compound matrix; the mass ratio of nitrogen-doped graphene, manganese carbonate and lithium fluorosilicate is 1:0.01-0.1:0.02-0.

2.

2. The high thermal conductivity potting compound according to claim 1, characterized in that, The nitrogen-doped graphene accounts for 1-2.5% of the mass of the potting compound matrix.

3. The high thermal conductivity potting compound according to claim 1, characterized in that, The preparation of modified nitrogen-doped graphene specifically includes the following steps: 1) Mix the ethanol solution of manganese carbonate with the nitrogen-doped graphene dispersion to ensure that the manganese source fully wets the nitrogen-doped graphene. Then, treat it under a high-temperature reducing atmosphere to reduce manganese carbonate to elemental manganese and obtain manganese-containing nitrogen-doped graphene. 2) Immerse the manganese-containing nitrogen-doped graphene obtained in step 1) in an ethanol solution of lithium fluorosilicate to ensure that the lithium fluorosilicate is uniformly distributed in the nitrogen-doped graphene; then vacuum dry and finally sinter to obtain modified nitrogen-doped graphene containing manganese oxide and lithium fluorosilicate.

4. The high thermal conductivity potting compound according to claim 3, characterized in that, In step 1), the concentration of the manganese carbonate ethanol solution is 0.05-0.5M; the concentration of the nitrogen-doped graphene dispersion is 2-13wt%; in step 2), the concentration of the lithium fluorosilicate ethanol solution is 0.05-0.5M.

5. The high thermal conductivity potting compound according to claim 3, characterized in that, In step 1), the mixing time of the ethanol solution of manganese carbonate and the nitrogen-doped graphene dispersion is 0.5-6 hours; in step 2), the soaking time is 0.5-6 hours.

6. The high thermal conductivity potting compound according to claim 3, characterized in that, In step 1), the treatment is carried out under a high-temperature reducing atmosphere. Specifically, the process involves using a hydrogen reducing atmosphere at a temperature of 400-600℃ for 0.5-6 hours. In step 2), the sintering process is carried out at 400-500℃ for 0.5-6 hours.

7. The high thermal conductivity potting compound according to claim 1, characterized in that, The nitrogen-doped graphene contains 0.5-3% nitrogen by atomic percentage.

8. The high thermal conductivity potting compound according to claim 1, characterized in that, The matrix resin is one or more of epoxy resin, polyurethane resin, silicone resin or acrylic resin; the filler is at least one of silica, aluminum powder or carbon fiber; the toughening agent is at least one of polyurethane, rubber or silicone rubber; and the solvent is at least one of cyclohexene, benzene or acetone.

9. A method for preparing a high thermal conductivity potting compound based on modified nitrogen-doped graphene according to any one of claims 1-8, characterized in that, Includes the following steps: 1) Mix the base resin and solvent evenly, then add the filler and mix evenly, and finally add the toughening agent and continue to mix evenly; 2) Disperse the modified nitrogen-doped graphene in acetone, and then add it to the resin mixture obtained in step 1), and stir until homogeneous; 3) The mixture obtained in step 2) is subjected to vacuum degassing treatment to obtain a high thermal conductivity silicone potting compound.

10. The application of the high thermal conductivity potting compound based on modified nitrogen-doped graphene as described in any one of claims 1-8 in the encapsulation of an electric vehicle OBC transformer.

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