Gradient modified diamond-based high-thermal-conductivity insulating composite resin and preparation method thereof

Abstract

The application discloses a gradient modified diamond-based high-thermal-conductivity insulating composite resin and a preparation method thereof, and belongs to the technical field of preparation of thermal-conductivity insulating materials.The composite resin is composed of an insulating resin matrix and a gradient modified diamond filler, takes diamond as a base, and sequentially has a carbide inner layer transition layer, 0-n layers of nitride intermediate buffer layers, and an oxide outermost combined layer from inside to outside; and the finished product is prepared through a complete set of procedures of gradient coating, surface activation and mixing and heat curing.The application breaks the limitation of traditional single coupling agent modification, gradually reduces the modulus difference between the filler and the matrix by relying on the multilayer gradient structure, weakens the interface phonon scattering to reduce the interface thermal resistance, simultaneously improves the surface activity of the filler by combining with a special activation procedure, improves the infiltration and combination capacity of the filler and the resin, effectively solves the problems of easy agglomeration of the diamond filler and poor interface combination, and can be widely applied to the insulating packaging field of high-power power components.

Description

Technical Field

[0001] This invention belongs to the field of thermally conductive and insulating material preparation technology, specifically to a gradient-modified diamond-based high thermal conductivity insulating composite resin and its preparation method. Background Technology

[0002] In the manufacturing of high-voltage power equipment, epoxy resins, due to their excellent insulation properties and molding characteristics, are often used as core materials for insulation encapsulation and are widely applied in power components such as DC converter valves, DC bushings, and gas-insulated switches. These polymer resins are composite materials based on polymers, possessing both insulation and plasticity. Currently, electrical equipment is gradually developing towards higher power and smaller, more integrated designs. Under high-load operation, the total heat generated increases significantly. If this heat cannot be dissipated in time, it will accelerate the aging of the insulating substrate, easily causing component damage and directly affecting the stability of equipment operation. Conventional pure resins have a thermal conductivity of only 0.1~0.3 W / (m·K), indicating weak heat dissipation performance. Compared to conventional inorganic thermally conductive fillers such as alumina and boron nitride, diamond has a thermal conductivity of up to 2000 W / (m·K), demonstrating outstanding thermal conductivity and making it an ideal functional filler for preparing high thermal conductivity insulating composite resins.

[0003] Based on practical R&D analysis, excessively high interfacial thermal resistance is the core challenge limiting the widespread application of diamond composite resins. The surface layer of diamond is chemically inert, making it difficult to form a dense and robust interface with the resin matrix. Heat transfer within solid materials primarily relies on phonons, energy quanta derived from lattice vibrations, which are the main carriers of heat conduction in solid media. Mechanical modulus reflects a material's resistance to elastic deformation, and this indicator can directly control the phonon vibration frequency and propagation rate. The elastic modulus of diamond is approximately 500 times that of epoxy resin; this significant performance difference causes severe reflection and scattering of phonons at the interface. Combined with interfacial bonding defects, the interfacial thermal resistance of this composite system is generally higher than 20 mm. 2 ·K·W -1 Currently, optimizing interfacial thermal resistance mainly focuses on two directions: strengthening the bonding ability of the two-phase interface and reducing the phonon reflection loss at the interface. However, relying solely on optimizing the interfacial bonding performance cannot solve the phonon loss problem caused by modulus mismatch, and the optimization effect has a clear upper limit.

[0004] To address the aforementioned pain points, mainstream R&D efforts in the industry focus on two main areas: strengthening interfacial bonding and constructing continuous thermally conductive networks. The corresponding mature technologies fall into two main categories. The first is the silane coupling agent surface modification process, which utilizes the unique molecular structure of silane reagents to form chemical bonds with diamond fillers and resin matrices, thereby improving interfacial compatibility and bonding stability. The second is the bimodal particle size filler compounding process, which uses diamond particles of varying sizes to complementarily fill the gaps between particles, constructing a continuous thermally conductive pathway within the resin. This, combined with silane surface modification, synergistically optimizes performance and is currently a widely adopted method for preparing composite materials in the industry.

[0005] Based on experimental results and practical feedback, it is evident that both existing technical solutions have significant drawbacks and cannot fundamentally solve the problem of excessively high interfacial thermal resistance. In the silane modification process, even with strong alkali activation pretreatment of diamond, its inherent chemical inertness limits the number of active hydroxyl groups on the surface capable of participating in the reaction, resulting in limited modification gain, poor batch stability, and the inability to improve phonon mismatch. The particle size blending process only increases filler density and optimizes the internal thermal conductivity network structure, without addressing the fundamental issues of loose interfacial bonding and severe phonon loss. In summary, there is currently a lack of preparation schemes that can simultaneously optimize interfacial bonding strength and phonon transmission efficiency, making it difficult to meet the usage standards of high-power electrical equipment. Therefore, there is an urgent need to develop novel diamond surface modification processes to overcome existing technological bottlenecks. Summary of the Invention

[0006] The purpose of this invention is to overcome the industry shortcomings of existing traditional modification processes, which have a single optimization dimension and cannot simultaneously solve the problems of poor interfacial bonding and phonon mismatch. This invention provides a gradient-modified diamond-based high thermal conductivity insulating composite resin and its preparation method. This invention employs a gradient coating method to modify diamond in layers, gradually reducing the difference in mechanical modulus between the filler and the resin matrix, weakening interfacial phonon loss, and simultaneously improving the surface activity of the filler. Ultimately, a composite resin material with low interfacial thermal resistance, high thermal conductivity, and excellent insulation properties is obtained.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a gradient modified diamond-based high thermal conductivity insulating composite resin, comprising an insulating resin matrix and gradient modified diamond filler dispersed within the insulating resin matrix; the gradient modified diamond filler uses diamond particles as a substrate, and from the inside to the outside of the substrate, a carbide material inner transition layer, a nitride material intermediate buffer layer (0~n layers), and an oxide material outermost bonding layer are sequentially disposed; the gradient modified diamond filler is uniformly dispersed and fixed within the insulating resin matrix after surface activation treatment.

[0008] Where n is a positive integer.

[0009] Furthermore, the volume doping ratio of the gradient modified diamond filler in the insulating resin matrix is ​​10 vol% to 50 vol%.

[0010] Furthermore, the diamond particle size ranges from 10μm to 50μm.

[0011] Furthermore, the inner transition layer material is selected from any one of silicon carbide, aluminum carbide, boron carbide, titanium carbide, and zirconium carbide; the intermediate buffer layer material is selected from any one or a combination of two of silicon nitride and aluminum nitride; and the outermost bonding layer material is selected from any one of silicon dioxide, aluminum oxide, titanium dioxide, and zirconium dioxide.

[0012] Furthermore, the insulating resin matrix is ​​epoxy resin or polyurethane.

[0013] This invention also provides a method for preparing a gradient-modified diamond-based high thermal conductivity insulating composite resin, comprising the following steps: Diamond particles of a predetermined size are selected as the substrate, and a carbide inner transition layer is prepared on the outside of the substrate. According to the heat dissipation requirements, a nitride intermediate buffer layer is selectively added on the outside of the inner transition layer. Finally, an oxide outermost bonding layer is uniformly prepared to obtain a gradient-coated diamond filler. A modification treatment solution was prepared, and the gradient-coated diamond filler was modified by constant temperature impregnation with the modification treatment solution to remove residual free reagents on the surface and dry it to obtain the gradient-modified diamond filler with completed surface activation treatment. Gradient-modified diamond filler with surface activation treatment was added to the insulating resin matrix in a preset ratio. After mechanical dispersion, vacuum degassing, and segmented thermosetting, a gradient-modified diamond-based high thermal conductivity insulating composite resin was obtained.

[0014] Furthermore, the processes for preparing the inner transition layer, the intermediate buffer layer, and the outermost bonding layer are independently selected from any one of vacuum sintering, chemical vapor deposition, spark plasma sintering, laser cladding, and vacuum multi-arc ion plating; wherein the preparation temperature of the inner transition layer is controlled at 1450℃~1550℃, and the shaping oxidation temperature of the outermost bonding layer is controlled at 1100℃~1300℃.

[0015] Furthermore, when preparing the inner transition layer of titanium carbide material using vacuum multi-arc ion plating, the specific process is as follows: the vacuum degree of the plating chamber is adjusted to ≤3×10 -3 Pa, using high-purity metallic titanium as the target material, sets the arc current to 50A~80A, and continuously deposits for 10min~30min to form a 100nm thick metallic titanium layer on the surface of the diamond substrate; then heat-treats in a vacuum environment at 850℃~900℃ to promote the in-situ reaction between metallic titanium and diamond to generate an inner titanium carbide transition layer.

[0016] Furthermore, the preparation of the modified treatment solution specifically includes: mixing anhydrous ethanol and deionized water in a volume ratio of 80:20 to 90:10, and adding a modifier to the mixed solvent to prepare a modified treatment solution with a mass concentration of 3wt% to 5wt%; the modifier is divided into two categories: silane coupling agents and organic acids; the silane coupling agents are KH550 and KH560; the organic acid is stearic acid.

[0017] Furthermore, the constant temperature impregnation modification specifically involves impregnation at 50℃~60℃ for 2h~12h, followed by washing the filler with anhydrous ethanol and deionized water and drying after impregnation.

[0018] Compared with the prior art, the present invention has at least the following beneficial effects: This invention discloses a gradient-modified diamond-based high thermal conductivity insulating composite resin. Unlike traditional exposed filler structures, it employs a gradient coating treatment on the diamond substrate. The overall structure, from the inside out, consists of a carbide inner transition layer, a flexibly configurable nitride intermediate buffer layer (0-n layers), and an outermost oxide bonding layer. Depending on the product application scenario, operators can choose to omit the intermediate buffer layer to create a simple two-layer structure, or add multiple nitride buffer layers to create a composite multi-layer structure. This invention also limits the diamond particle size range, the selectable materials for each functional coating layer, and the filler filling ratio, and is compatible with two common insulating matrices: epoxy resin and polyurethane. The gradient layer structure gradually weakens the modulus difference between the diamond and the resin matrix, mitigating phonon scattering during heat transfer and reducing interfacial heat loss. The outermost oxide material of the filler is easily activated and modified, providing sufficient reaction sites for subsequent activation processes. Based on this structural design, it can adapt to diamond powders of different specifications and is compatible with mainstream insulating resin substrates, exhibiting far superior adaptability compared to traditional uncoated modified fillers.

[0019] Furthermore, unlike the industry's approach of directly activating bare diamond, this invention prioritizes gradient coating before surface activation and curing of the coated powder. This coating-then-activation logic avoids the drawbacks of excessive surface inertness and poor adhesion of modifying agents in bare diamond. Subsequent processes, including mechanical dispersion, vacuum degassing, and segmented thermosetting, are used to prepare the finished product. Each step is an optimized complement to the preceding steps, progressing layer by layer. This approach controls the interfacial bonding and molding quality of the composite material from the source of preparation, effectively solving the problems of fragmented processes and unstable modification effects in traditional manufacturing processes.

[0020] Furthermore, this invention provides multiple processing techniques for preparing gradient coatings, allowing companies to freely choose the appropriate technique based on their equipment reserves and production scale, thus lowering the barrier to implementation. Precise and detailed process parameters effectively avoid common production defects such as coating peeling, detachment, and uneven thickness, ensuring a strong bond between the coating and the diamond substrate. In mass production, the modified diamond powder exhibits stronger performance consistency, balancing mass production costs and product yield.

[0021] Furthermore, this invention includes a customized activation system that specifies the ratio of alcohol-water mixed solvent and the concentration of the modified treatment solution. It also categorizes modifiers into two types suitable for different operating conditions and clearly defines the constant-temperature immersion temperature, duration, and post-treatment cleaning method. Compared to general activation solutions, this invention's customized activation treatment solution can specifically adapt to the oxide surface structure, stably generating hydroxyl and amino functional groups on the filler surface. The activated gradient-modified diamond exhibits better wetting effect with the resin matrix, effectively inhibiting filler agglomeration and sedimentation, allowing the filler to be uniformly distributed within the matrix, and providing the foundation for constructing continuous and stable internal thermal conductivity pathways.

[0022] Furthermore, the curing process is the core step in preparing solid insulating composite materials. After vacuum degassing, the mixture undergoes segmented thermosetting to achieve resin cross-linking polymerization, transforming it from a liquid state to an irreversible solid structure. During the curing and molding stage, the filler dispersion is locked in, stabilizing the already formed thermally conductive network. On the other hand, the shrinkage of the cross-linked resin tightly encapsulates the modified filler, and, combined with the active functional groups generated on the filler surface, further compacts the interface between the filler and the matrix, reducing interfacial gaps and minimizing the interfacial thermal resistance of the composite system. This invention can meet the needs of large-scale mass production of conventional insulating materials and is also suitable for high-end packaging scenarios of high-power power components, demonstrating high industrial application value. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the cross-sectional hierarchical structure of the gradient-modified diamond of the present invention. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0025] This invention provides a gradient-modified diamond-based high thermal conductivity insulating composite resin, which has a layered gradient coating structure prepared on the diamond surface. The functional layers have fixed properties from the inside out, while an optional buffer layer is provided; wherein M x C y Refers to various metal carbides, M x N y Refers to metal or nonmetal nitrides, M x O y Refers to oxides of metals or nonmetals. For example... Figure 1 As shown, the gradient-modified diamond monolithic structure uses diamond as a base and an inner layer fixedly encapsulating M. x C y Material transition layer, outer layer finally uniformly molded into M x O y Oxide bonding layer; workers can selectively add M between the inner and outer layers according to actual heat dissipation requirements. x N y Nitride intermediate buffer layer, which is used to classify two types of gradient structures: two-layer gradient structure and multi-layer gradient structure.

[0026] This invention also provides a method for preparing the aforementioned gradient-modified diamond-based high thermal conductivity insulating composite resin. The overall process is divided into three stages: diamond gradient modification, filler surface activation, and composite resin mixing and curing. The entire process is adapted to industrial mass production conditions. The specific operation steps are as follows: (1) Gradient treatment of diamond surface Diamond particles with a particle size of 10μm to 50μm are selected as the substrate, and the gradient coating preparation process can be any one of vacuum sintering, chemical vapor deposition, spark plasma sintering, laser cladding, or vacuum multi-arc ion plating.

[0027] Specific preparation process: The first step is to prepare the inner transition layer. Diamond powder and corresponding metal powder are mixed uniformly at a volume ratio of 1:1 to 1:3. Alternatively, a metal coating can be directly deposited on the diamond surface using a deposition process. An in-situ reaction occurs at a high temperature of 1450℃ to 1550℃ to generate M. x C y The inner transition layer is a carbide layer. Optional carbides include silicon carbide, aluminum carbide, boron carbide, titanium carbide, and zirconium carbide. In actual production, titanium carbide is preferred for small-diameter diamonds, while silicon carbide is preferred for large-diameter diamonds.

[0028] The second step involves the differentiated fabrication of the outer functional layer. After the inner transition layer is fabricated, two structural methods are employed: if a bilayer gradient structure is to be fabricated, M is directly fabricated on the outer side of the inner transition layer. x O y The oxide bonding layer can be made of materials such as silicon dioxide, aluminum oxide, titanium dioxide, or zirconium dioxide. If a multilayer gradient structure is fabricated, one or more M layers are added between the inner transition layer and the outer oxide layer. x N y The buffer layer is made of silicon nitride or aluminum nitride. After the buffer layer is laid, the outermost oxide bonding layer is prepared.

[0029] The third step is to standardize the outer layer. The semi-finished fillers with the above two structures are placed in a high-temperature oxidation environment of 1100℃~1300℃ for secondary modification to ensure that the outermost layer of all graded modified diamonds is stably M. x O y The oxide structure ensures that the finished filler has a uniform structure and controllable performance.

[0030] (2) Activation treatment The surface layer of the gradient-modified diamond still exhibits inert characteristics. To further increase the number of active functional groups on the filler surface and enhance the compatibility and interfacial bonding strength between the filler and the resin matrix, this invention requires a uniform surface activation treatment for all gradient-coated diamond fillers. The specific operation steps and process parameters are as follows: 1) Preparation of mixed solvent: Using anhydrous ethanol and deionized water as base solvents, prepare the mixed solvent at a volume ratio of 80:20~90:10, and stir thoroughly until the system is homogeneous before use. 2) Preparation of modified treatment solution: Add a quantitative amount of modifier to the prepared mixed solvent and stir continuously until the modifier is completely dissolved to prepare a modified treatment solution with a mass concentration in the range of 3wt%~5wt%. 3) Constant-temperature impregnation modification: The gradient-modified diamond is completely immersed in the modification solution, and the overall reaction system is kept at a constant temperature of 50℃~60℃ for 2h~12h. After the reaction, the filler is washed repeatedly with anhydrous ethanol and deionized water to remove the free modifier and impurities remaining on the surface. After drying, activated diamond filler rich in hydroxyl and amino active groups is obtained.

[0031] Further, the modifiers are divided into two categories: silane coupling agents and organic acids. Among them, KH550 and KH560 are preferred silane coupling agents, which are suitable for all types of gradient structure fillers in both double-layer and multi-layer structures. Stearic acid is selected as the organic acid, which is mainly suitable for the activation of small-particle-size double-layer gradient structure diamond.

[0032] (3) Preparation and molding of composite resin Using activated gradient-modified diamond as a thermally conductive filler, a composite insulating resin was prepared through a three-step process of batching, dispersion, and curing. The specific operation and parameter ranges are as follows: 1) Batching and feeding: According to production needs, the activated diamond is weighed at a volume ratio of 10vol% to 50vol%. For routine performance testing and small-batch production scenarios, a doping ratio of 10vol% is preferred, as the filler is less likely to agglomerate at this ratio, resulting in the best overall cost performance. 2) Dispersion and mixing: Slowly add the weighed diamond filler into the liquid resin matrix and disperse the material by mechanical stirring at a speed of 300~800 r / min for 30~120 min to ensure uniform dispersion of the filler and avoid agglomeration and sedimentation. 3) Curing and molding: After mixing, vacuum degassing is performed to eliminate tiny air bubbles entangled in the stirring. Then, the mixture is introduced into a special molding mold and cured in stages with controlled temperature, taking into account the curing characteristics of the resin itself. After cooling and demolding, a dense and stable high thermal conductivity insulating composite resin can be obtained.

[0033] Furthermore, the resin matrix used in this invention is epoxy resin or polyurethane. Both types of substrates have excellent insulation properties and are suitable for most power insulation encapsulation scenarios.

[0034] Compared to existing traditional technologies, this invention innovatively sets up a gradient covering structure, with M arranged sequentially from the inside out. x C y Carbide inner layer, optional M x N y Nitride buffer layer, M x O y The outer oxide layer, through a multi-layer structure, gradually weakens the modulus difference between diamond and the resin matrix, thereby reducing interfacial phonon scattering loss from the source. At the same time, the outer oxide layer can significantly improve the surface activity of the filler. With the unified activation process, the bonding strength between the filler and the matrix is ​​significantly improved, effectively solving the drawback of poor thermal resistance optimization effect of traditional modification technology, and making it suitable for use in various specifications of high-power electrical equipment.

[0035] To facilitate a better understanding and implementation of the technical solutions disclosed in this invention by those skilled in the art, the invention will be described in detail below with reference to specific embodiments. It should be noted that the following embodiments are merely preferred exemplary implementations of this invention, used to explain the core preparation process, and are not intended to limit the scope of protection of this invention. Any conventional and simple equivalent substitutions made by those skilled in the art based on the overall technical concept of this invention for relevant process parameters, coating materials, and substrate types should fall within the scope of protection of this invention.

[0036] All the following embodiments were prepared strictly according to the overall process flow described in this invention, sequentially completing three processes: gradient coating of diamond substrate, surface activation treatment of filler, and curing of composite resin. The filler was uniformly added at a volume percentage of 10 vol%. All thermal conductivity data were obtained by averaging multiple parallel tests at room temperature. Each set of embodiments was accompanied by a blank control group of pure resin without any thermally conductive filler, for visual evaluation of the improvement effect on the thermal conductivity of the material. The gradient coating layers of this invention are defined from the inside to the outside as follows: inner transition layer (M x C y Carbide), intermediate buffer layer (M)x N y Nitrides, added as needed), outermost bonding layer (M x O y (Oxides).

[0037] Example 1 This embodiment uses a double-layer gradient coating structure diamond filler, with diamond of average particle size of 20μm as the substrate. The coating structure consists of an inner transition layer of silicon carbide material and an outermost bonding layer of silicon dioxide material from the inside to the outside.

[0038] Gradient coating preparation: Diamond powder and silicon powder (particle size ~50 nm) are uniformly mixed at a volume ratio of 1:2, and vacuum sintering is carried out at 1500℃ for 45 min to generate a silicon carbide inner transition layer on the diamond surface. Subsequently, it was placed in a high-purity oxygen atmosphere at 1200℃ for constant temperature oxidation for 60 minutes to prepare the outermost bonding layer of dense silicon dioxide.

[0039] Surface activation treatment: Prepare a mixed solvent of anhydrous ethanol and deionized water (volume ratio 90:10), add KH550 silane coupling agent to prepare a 3wt% modification treatment solution; completely immerse the gradient modified diamond in the solution and immerse it at 55℃ for 8 hours. After the reaction, wash the filler alternately with anhydrous ethanol and deionized water, and dry it for later use.

[0040] Sample preparation and performance testing: Activated diamond was added to the epoxy resin matrix at a doping ratio of 10 vol%, mechanically stirred at 500 r / min for 60 min, and then vacuum degassed before segmental curing. The thermal conductivity of the composite resin in this embodiment was tested to be 0.48 W·m. -1 ·K -1 The thermal conductivity of the blank epoxy resin matrix is ​​0.36 W·m. -1 ·K -1 Thermal conductivity is improved by 33%.

[0041] Example 2 This embodiment uses a double-layer gradient coating structure diamond filler, with diamond of average particle size of 50μm as the substrate. The coating structure consists of an inner silicon carbide transition layer and an outermost silicon dioxide bonding layer from the inside out.

[0042] Gradient coating preparation: The preparation process is consistent with that in Example 1. The silicon carbide-silica bilayer gradient coating modification is completed by a two-step method of vacuum sintering and high-temperature oxidation.

[0043] Surface activation treatment: Solvent ratio 85:15, use KH560 silane coupling agent to prepare 5wt% modified treatment solution, immerse at constant temperature of 55℃ for 8h, clean and dry to complete activation.

[0044] Sample preparation and performance testing: Polyurethane resin was used as the matrix, with a filler doping amount of 10 vol%, and the mixture was stirred at 500 r / min for 60 min before curing. The tested thermal conductivity of the finished product was 0.44 W·m. -1 ·K -1 The thermal conductivity of the blank polyurethane matrix is ​​0.34 W·m. -1 ·K -1 Thermal conductivity is improved by 29%.

[0045] Example 3 This embodiment uses a double-layer gradient coating structure diamond filler, with diamond of average particle size of 10μm as the substrate. The coating structure consists of an inner titanium carbide transition layer and an outermost titanium dioxide bonding layer from the inside out.

[0046] Gradient coating preparation: Titanium plating was performed on the diamond substrate using a vacuum multi-arc ion plating process. The specific process parameters are as follows: Before plating, the vacuum level in the cavity was evacuated to ≤3×10. -3 Pa, using high-purity metallic titanium as the target material, controlling the titanium target arc current at 50A~80A, and continuously depositing for 10min~30min, finally forming a uniform and dense metallic titanium layer with a thickness of about 100nm on the diamond surface; after completing the titanium plating operation, the diamond powder coated with the titanium layer is placed in a vacuum environment at 850℃~900℃ for heat treatment, which promotes the in-situ solid-phase reaction between the surface metallic titanium and the diamond matrix, generating a firmly bonded titanium carbide inner transition layer; finally, the semi-finished powder is placed in a high-purity oxygen atmosphere at 1100℃~1300℃ for constant temperature oxidation for 1h, forming an outermost titanium dioxide bonding layer on the outer layer of titanium carbide.

[0047] Surface activation treatment: Prepare an 80:20 ethanol-deionized water mixed solvent, use stearic acid as a modifier, prepare a 5wt% treatment solution, immerse at 50℃ for 10h and then dry.

[0048] Sample preparation and performance testing: Polyurethane was used as the matrix, with 10 vol% modified diamond doped and cured by stirring at 400 r / min for 90 min. The finished product had a thermal conductivity of 0.42 W·m. -1 ·K -1 The improvement was 23% compared to the blank polyurethane matrix.

[0049] Example 4 This embodiment uses a three-layer gradient coating structure diamond filler with an added nitride intermediate buffer layer; diamond with an average particle size of 10μm is selected, and the structure from the inside out is a silicon carbide inner transition layer, a silicon nitride intermediate buffer layer, and a silicon dioxide outermost bonding layer.

[0050] Gradient coating preparation: Diamond and silicon powder (particle size ~50nm) are mixed in a 1:1 ratio and sintered in vacuum at 1450℃ to prepare the silicon carbide inner layer; nitriding is carried out in a high-purity nitrogen atmosphere at 1200℃ to generate the silicon nitride intermediate buffer layer; oxidation is carried out in a high-purity oxygen atmosphere at 1150℃ to obtain the outermost silicon dioxide bonding layer.

[0051] Surface activation treatment: KH550 silane coupling agent was used to prepare a 3wt% ethanol-water solution (80:20), which was immersed at 60℃ for 4 hours, and then cleaned and dried.

[0052] Sample preparation and performance testing: Epoxy resin was used as the matrix, with filler added at 10 vol%, and the mixture was stirred at 800 r / min for 30 min and then cured. The finished product had a thermal conductivity of 0.46 W·m. -1 ·K -1 Compared to the blank epoxy resin, it improved by 28%.

[0053] Example 5 This embodiment adopts a four-layer composite gradient coating structure, which is suitable for high heat dissipation conditions; diamond with an average particle size of 50μm is selected, and from the inside to the outside are a silicon carbide inner transition layer, a silicon nitride and aluminum nitride double-layer intermediate buffer layer, and an aluminum oxide outermost bonding layer.

[0054] Gradient coating preparation: Silicon carbide inner transition layer synthesized in vacuum at 1550℃; silicon nitride and aluminum nitride two M layers were prepared sequentially. x N y Nitride buffer layer; high-temperature oxidation at 1300℃ for 30 minutes to form the outermost bonding layer of alumina.

[0055] Surface activation treatment: A 3wt% treatment solution was prepared using KH560 silane coupling agent and immersed at a constant temperature of 55℃ for 12 hours to complete the activation modification.

[0056] Sample preparation and performance testing: Epoxy resin matrix, 10 vol% filler doped, cured by stirring at 600 r / min for 120 min. The finished product has a thermal conductivity of 0.49 W·m. -1 ·K -1 Compared to the blank epoxy resin, it improved by 36%.

[0057] Based on the test data from the above five sets of embodiments, it can be seen that, under the premise that the filler doping amount and preparation environment are completely consistent, the present invention can effectively solve the technical problem of modulus mismatch between diamond and resin matrix through gradient coating modification. The double-layer gradient structure simplifies the preparation process through direct carbide-oxide composite, making it suitable for mass production, and the thermal conductivity improvement is consistently within the range of 23% to 33%. The multi-layer gradient structure, through the addition of M... x N yThe nitride intermediate buffer layer buffers the interface modulus difference step by step, minimizing the interface phonon scattering loss. Among them, the five-layer composite structure in Example 5 has the best gain effect, with a thermal conductivity improvement rate of up to 36%.

[0058] Furthermore, the experimental results show that the modified process of this invention is adaptable to diamonds with different particle sizes ranging from 10μm to 50μm, and is compatible with both epoxy resin and polyurethane, two mainstream insulating resin substrates on the market, demonstrating strong process versatility. The entire preparation process is simple and controllable, without demanding reaction conditions, and can meet the production needs of conventional civilian insulating devices as well as be adapted to high-end packaging scenarios for high-power power components, possessing high industrialization value.

Claims

1. A gradient-modified diamond-based high thermal conductivity insulating composite resin, characterized in that, The invention includes an insulating resin matrix and gradient modified diamond filler dispersed within the insulating resin matrix. The gradient modified diamond filler uses diamond particles as a substrate, and from the inside to the outside of the substrate, an inner transition layer of carbide material, an intermediate buffer layer of nitride material (0~n layers), and an outermost bonding layer of oxide material are sequentially arranged. The gradient modified diamond filler is uniformly dispersed and fixed within the insulating resin matrix after surface activation treatment.

2. The gradient-modified diamond-based high thermal conductivity insulating composite resin according to claim 1, characterized in that, The volume doping ratio of the gradient modified diamond filler in the insulating resin matrix is ​​10 vol% to 50 vol%.

3. The gradient-modified diamond-based high thermal conductivity insulating composite resin according to claim 1, characterized in that, The diamond particle size ranges from 10μm to 50μm.

4. The gradient-modified diamond-based high thermal conductivity insulating composite resin according to claim 1, characterized in that, The inner transition layer is made of any one of silicon carbide, aluminum carbide, boron carbide, titanium carbide, and zirconium carbide; the intermediate buffer layer is made of any one or a combination of two of silicon nitride and aluminum nitride; and the outermost bonding layer is made of any one of silicon dioxide, aluminum oxide, titanium dioxide, and zirconium dioxide.

5. The gradient-modified diamond-based high thermal conductivity insulating composite resin according to claim 1, characterized in that, The insulating resin matrix is ​​epoxy resin or polyurethane.

6. A method for preparing a gradient-modified diamond-based high thermal conductivity insulating composite resin according to any one of claims 1 to 5, characterized in that, Includes the following steps: Diamond particles of a predetermined size are selected as the substrate, and a carbide inner transition layer is prepared on the outside of the substrate. According to the heat dissipation requirements, a nitride intermediate buffer layer is selectively added on the outside of the inner transition layer. Finally, an oxide outermost bonding layer is uniformly prepared to obtain a gradient-coated diamond filler. A modification treatment solution was prepared, and the gradient-coated diamond filler was modified by constant temperature impregnation with the modification treatment solution to remove residual free reagents on the surface and dry it to obtain the gradient-modified diamond filler with completed surface activation treatment. Gradient-modified diamond filler with surface activation treatment was added to the insulating resin matrix in a preset ratio. After mechanical dispersion, vacuum degassing, and segmented thermosetting, a gradient-modified diamond-based high thermal conductivity insulating composite resin was obtained.

7. The method for preparing a gradient-modified diamond-based high thermal conductivity insulating composite resin according to claim 6, characterized in that, The processes for preparing the inner transition layer, the intermediate buffer layer, and the outermost bonding layer are independently selected from any one of vacuum sintering, chemical vapor deposition, spark plasma sintering, laser cladding, and vacuum multi-arc ion plating; the preparation temperature of the inner transition layer is controlled at 1450℃~1550℃, and the shaping and oxidation temperature of the outermost bonding layer is controlled at 1100℃~1300℃.

8. The method for preparing a gradient-modified diamond-based high thermal conductivity insulating composite resin according to claim 7, characterized in that, When preparing the inner transition layer of titanium carbide material using vacuum multi-arc ion plating, the specific process is as follows: the vacuum degree of the plating chamber is adjusted to ≤3×10. -3 Pa, using high-purity metallic titanium as the target material, sets the arc current to 50A~80A, and continuously deposits for 10min~30min to form a 100nm thick metallic titanium layer on the surface of the diamond substrate; then heat-treats in a vacuum environment at 850℃~900℃ to promote the in-situ reaction between metallic titanium and diamond to generate an inner titanium carbide transition layer.

9. The method for preparing a gradient-modified diamond-based high thermal conductivity insulating composite resin according to claim 6, characterized in that, The preparation of the modified treatment solution specifically includes: mixing anhydrous ethanol and deionized water in a volume ratio of 80:20 to 90:10, and adding a modifier to the mixed solvent to prepare a modified treatment solution with a mass concentration of 3wt% to 5wt%; the modifier is divided into two categories: silane coupling agents and organic acids; the silane coupling agents are KH550 and KH560; the organic acid is stearic acid.

10. The method for preparing a gradient-modified diamond-based high thermal conductivity insulating composite resin according to claim 9, characterized in that, The constant temperature impregnation modification specifically involves impregnation at 50℃~60℃ for 2h~12h. After impregnation, the filler is washed with anhydrous ethanol and deionized water and then dried.

Images