High-thermal-conductivity and low-dielectric silica gel composite material and preparation method thereof

Abstract

The preparation method comprises the following steps: S1, adding a two-dimensional filler into an acid ester water-containing solvent, adjusting the pH value to a preset range, and carrying out a hydrolytic condensation reaction, so that a transition layer is deposited on the surface of the two-dimensional filler, and a primary product is obtained; s2, modifying a transition layer of the primary product to form a pore structure, and adding a one-dimensional filler in the modification process so that the one-dimensional filler is located in the pore structure of the transition layer to obtain a build-in material; s3, adding three-dimensional filler into the build-in material, stirring and mixing to obtain composite filler, uniformly mixing the composite filler with a silica gel matrix, curing and forming to obtain the silica gel composite material with high thermal conductivity and low dielectric, and realizing structured connection of the fillers in different dimensions through a transition layer to form an interpenetrating heat-conducting network, thereby realizing high thermal conductivity under the condition of lower filler consumption. Meanwhile, the overall density of the material is reduced, and the low dielectric property of the material is considered.

Description

Technical Field

[0001] This invention relates to the field of polymer composite materials technology, and more particularly to a silicone composite material with high thermal conductivity and low dielectric constant, and its preparation method. Background Technology

[0002] Thermal pads, as an important interfacial thermal management material, are widely used between electronic components and heat sinks, playing a crucial role in filling gaps and transferring heat. Their overall performance directly affects the overall heat dissipation efficiency. Currently, most common thermal pads are made with polymers such as silicone rubber as the matrix and filled with thermally conductive fillers such as boron nitride and alumina. However, this type of traditional material faces significant contradictions in the synergistic optimization of multiple performance indicators. To improve the thermal conductivity, it is usually necessary to significantly increase the filler content, but this often leads to an increase in pad density and dielectric constant, while decreasing mechanical strength and flexibility. Conversely, if the filler content is reduced to maintain lower density and dielectric properties, the thermal conductivity may not meet the high-power heat dissipation requirements.

[0003] In existing silicone composite materials, fillers of different dimensions are typically introduced into the system through simple physical mixing or surface coupling agent modification, with each filler existing in an independent dispersed state within the matrix. In this approach, there is a lack of stable interface between fillers of different dimensions. One-dimensional fillers struggle to form effective overlaps with two-dimensional fillers, and the contact between three-dimensional and two-dimensional fillers is mostly localized or point-to-point, resulting in unstable contact relationships between fillers and making it difficult to form a continuous and controllable filler network within the material.

[0004] Furthermore, to improve the interfacial compatibility between the filler and the silica matrix, existing technologies typically modify fillers of different dimensions separately with silane coupling agents, introducing an organic functional layer onto the filler surface. While this method can improve the dispersibility of the filler in the matrix, it also forms an organic coating layer on the filler surface, isolating the direct contact interface between fillers. When multiple fillers are modified separately and mixed, the contact interface between fillers of different dimensions mainly occurs between the organic modification layers on their respective surfaces, making it difficult for the fillers to form a stable contact relationship, further weakening the structural connection between fillers of different dimensions. Summary of the Invention

[0005] In view of this, the present invention proposes a high thermal conductivity and low dielectric silicone composite material and its preparation method, which solves the technical problem of poor contact effect and low bonding force of fillers of different dimensions in existing silicone composite materials, resulting in a decrease in dielectric properties and thermal conductivity.

[0006] The technical solution of this invention is implemented as follows: A method for preparing a silicone composite material with high thermal conductivity and low dielectric constant includes the following steps: S1, the two-dimensional filler is added to an acid acid-based aqueous solvent, the pH value is adjusted to a preset range to carry out a hydrolysis and condensation reaction, so that a transition layer is deposited on the surface of the two-dimensional filler to obtain the initial product; S2, modify the transition layer of the initial material to form a porous structure, and add one-dimensional filler during the modification process so that the one-dimensional filler is in the porous structure of the transition layer to obtain an embedded material. S3, add three-dimensional filler to the embedding material, stir and mix to obtain composite filler, mix the composite filler with silicone matrix, and cure to obtain silicone composite material with high thermal conductivity and low dielectric.

[0007] In this technical solution, step S1 further includes: S1.1, the two-dimensional filler is added to a solvent containing the precursor, ultrasonically dispersed, and then a regulator is added to adjust the pH value until the preset pH value is reached, so that the precursor undergoes a hydrolysis and condensation reaction to form a precursor deposit on the surface of the two-dimensional filler. S1.2, a pore-forming agent is added to form a porous structure in the precursor sediment, which is then converted into a transition layer to obtain the initial product.

[0008] In this technical solution, the mass ratio of the two-dimensional filler to the solvent is 1:6-30. The two-dimensional filler includes one of boron nitride, molybdenum disulfide, and carbon nitride. The solvent includes water and organic matter. The organic matter includes one of ethanol, isopropanol, methanol, and n-butanol. The modifier is selected from one of ammonia, sodium hydroxide, and triethylamine. The precursor includes at least one of silicate ester, titanate ester, and aluminate ester precursors. The amount of the precursor is 1-10% of the mass of the two-dimensional filler. The pore-forming agent includes at least one of polyethylene glycol, ammonium bicarbonate, urea, and sodium dodecyl sulfate. The amount of the pore-forming agent is 0.5-5% of the mass of the two-dimensional filler. The ultrasonic dispersion power is 200-500W, and the dispersion time is 10-30min.

[0009] In this technical solution, step S2 further includes: S2.1, the primary material is subjected to a combination of heating and ultrasonic treatment, one-dimensional filler is added, high-speed shearing is performed, and the mixture is homogenized to form a porous structure in the transition layer; S2.2, a hydrolysis-condensation reaction is carried out to solidify the pore structure of the transition layer, and the one-dimensional filler is embedded in the pores of the transition layer to obtain the embedded material.

[0010] In this technical solution, the heating temperature of the combined heating and ultrasonic treatment is 40-60℃, the ultrasonic power is 300-600W, and the treatment time is 5-20min; the rotation speed of the high-speed shear mixing is 800-1500r / min, and the mixing time is 5-15min; the holding temperature of the continued hydrolysis and condensation is 50-70℃, and the holding time is 1-3h; the one-dimensional filler includes at least one of boron-nitrogen nanotubes and alumina nanofibers, and the amount of one-dimensional filler is 1-5% of the mass of the two-dimensional filler.

[0011] In this technical solution, step S3 further includes S3.1, after adding the three-dimensional filler to the embedding material, it is first ultrasonically dispersed and then stirred and mixed. The ultrasonic power is 200-400W, the dispersion time is 5-10min, the stirring speed is 300-800r / min, and the mixing time is 10-30min, so that the three-dimensional filler is uniformly filled in the gap between the transition layer and the two-dimensional filler and is in close contact with the outer surface of the transition layer to obtain the composite filler; S3.2, the composite filler and silicone matrix are mixed by low-temperature shearing at a temperature of 20-30℃, a shearing speed of 30-50 r / min, and a mixing time of 30-60 min. Then, the mixture is pre-pressed under a pressure of 10-16 MPa and then subjected to gradient heating curing. The mixture is kept at 60-80℃ for 1-2 h, at 80-110℃ for 2-3 h, and at 110-130℃ for 1-2 h. After curing, a silicone composite material with high thermal conductivity and low dielectric constant is obtained.

[0012] Furthermore, in this technical solution, the silicone matrix is ​​composed of hydrogen-containing silicone oil, vinyl silicone oil, and platinum catalyst, with a mass ratio of hydrogen-containing silicone oil: vinyl silicone oil: platinum catalyst = 3:2.8:0.005; the mass ratio of the composite filler to the silicone matrix is ​​1:3-12; the three-dimensional filler includes at least one of spherical alumina, boron nitride microspheres, and hollow silica microspheres; the amount of the three-dimensional filler is 10-40% of the mass of the two-dimensional filler; and the particle size of the three-dimensional filler is 50-500 nm.

[0013] On the other hand, the present invention also provides a high thermal conductivity and low dielectric silicone composite material, which is made by the preparation method of the high thermal conductivity and low dielectric silicone composite material according to any one aspect, including a two-dimensional filler with a transition layer on its surface, a one-dimensional filler embedded in the transition layer, a three-dimensional filler in contact with the outer surface of the transition layer, and a silicone matrix.

[0014] The present invention has the following advantages over the prior art: The surface of the two-dimensional packing is hydrolyzed and condensed to form a transition layer with a porous structure. The one-dimensional packing is embedded in the pores of the transition layer to achieve an anchoring connection with the two-dimensional packing, preventing the one-dimensional packing from becoming free or agglomerated, and improving the bonding force and structural stability between the one-dimensional and two-dimensional packings. The outer surface of the transition layer provides a contact interface for the three-dimensional packing, improving the contact effect between the three-dimensional packing and the transition layer, enhancing the effective connection between the three-dimensional packing and the one-dimensional and two-dimensional packings, reducing the interfacial thermal resistance between the packings, and improving the connectivity efficiency of the heat conduction path. Different dimensional fillers are structurally connected through a transition layer to form an interconnected thermally conductive network. This avoids the problem of reduced thermal conductivity caused by stacking two-dimensional fillers and point contact between fillers. It achieves high thermal conductivity with a low filler content, while reducing the overall density of the material and taking into account the low dielectric properties of the material. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic flowchart illustrating the preparation method of a high thermal conductivity, low dielectric silicone composite material according to the present invention. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] This invention provides a high thermal conductivity and low dielectric constant silicone composite material and its preparation method. By constructing a transition layer with a porous structure on the surface of a two-dimensional filler, the structured embedding and tight connection of fillers of different dimensions (one-dimensional, two-dimensional, and three-dimensional) are achieved, which greatly improves the bonding force and contact effect between fillers, effectively reduces interfacial thermal resistance, and constructs a continuous and interconnected thermally conductive network. This achieves high thermal conductivity of the material with a low filler content, while maintaining excellent low dielectric properties.

[0019] like Figure 1 As shown, a method for preparing a silicone composite material with high thermal conductivity and low dielectric constant includes the following steps: S1, the two-dimensional filler is added to an acid-ester aqueous solvent, and the pH value is adjusted to a preset range to carry out a hydrolysis-condensation reaction, so that a transition layer is deposited on the surface of the two-dimensional filler to obtain the preliminary product; specifically, step S1 includes: S1.1, the two-dimensional filler is added to a solvent containing the precursor, ultrasonically dispersed, and then a regulator is added to adjust the pH value until the preset pH value is reached, so that the precursor undergoes a hydrolysis and condensation reaction to form a precursor deposit on the surface of the two-dimensional filler. S1.2, a pore-forming agent is added to form a porous structure in the precursor sediment, which is then converted into a transition layer to obtain the initial product.

[0020] The mass ratio of the two-dimensional filler to the solvent is 1:6-30. The two-dimensional filler includes one of boron nitride, molybdenum disulfide, and carbon nitride. The solvent includes water and organic matter. The organic matter includes one of ethanol, isopropanol, methanol, and n-butanol. The modifier is selected from one of ammonia, sodium hydroxide, and triethylamine. The precursor includes at least one of silicate ester, titanate ester, and aluminate ester precursors. The amount of the precursor is 1-10% of the mass of the two-dimensional filler. The pore-forming agent includes at least one of polyethylene glycol, ammonium bicarbonate, urea, and sodium dodecyl sulfate. The amount of the pore-forming agent is 0.5-5% of the mass of the two-dimensional filler. The ultrasonic dispersion power is 200-500W, and the dispersion time is 10-30min.

[0021] By ultrasonically dispersing the two-dimensional filler, it can be uniformly dispersed in the solvent, avoiding agglomeration and laying the foundation for the uniform deposition of the subsequent precursor. One or more of silicates, titanates, and aluminates are selected as precursors. Under the action of a regulator, they undergo hydrolysis and condensation reactions, forming uniform precursor deposits on the surface of the two-dimensional filler, providing a basis for the formation of the transition layer. The addition of a pore-forming agent enables the precursor deposits to form a uniform pore structure. This pore structure not only provides space for the subsequent embedding of one-dimensional fillers but also increases the specific surface area of ​​the filler, improving the bonding effect with the silica matrix, while not compromising the low dielectric properties of the material.

[0022] S2, modifying the transition layer of the initial material to form a porous structure, adding a one-dimensional filler during the modification process so that the one-dimensional filler is located in the porous structure of the transition layer, thus obtaining an embedded material; specifically, step S2 includes: S2.1, the primary material is subjected to a combination of heating and ultrasonic treatment, one-dimensional filler is added, high-speed shearing is performed, and the mixture is homogenized to form a porous structure in the transition layer; S2.2, a hydrolysis-condensation reaction is carried out to solidify the pore structure of the transition layer, and the one-dimensional filler is embedded in the pores of the transition layer to obtain the embedded material.

[0023] The heating temperature for the combined heating and ultrasonic treatment is 40-60℃, the ultrasonic power is 300-600W, and the treatment time is 5-20min; the high-speed shear mixing speed is 800-1500r / min, and the mixing time is 5-15min; the holding temperature for the continued hydrolysis and condensation is 50-70℃, and the holding time is 1-3h; the one-dimensional filler includes at least one of boron-nitrogen nanotubes and alumina nanofibers, and the amount of one-dimensional filler is 1-5% of the mass of the two-dimensional filler.

[0024] Heating and ultrasonic treatment of the initial material can fully open the pore structure of the transition layer and improve the fluidity of the system, facilitating the dispersion and entry of one-dimensional fillers. High-speed shearing further disperses the one-dimensional fillers evenly and fills the pores of the transition layer. Subsequent hydrolysis and condensation reactions solidify the pore structure of the transition layer, achieving anchoring connection between the one-dimensional and two-dimensional fillers, preventing the one-dimensional fillers from becoming free or agglomerated, and significantly improving the bonding force and structural stability between the one-dimensional and two-dimensional fillers, providing a foundation for constructing a continuous heat-conducting network.

[0025] S3, adding three-dimensional filler to the embedding material, stirring and mixing to obtain a composite filler, mixing the composite filler with the silicone matrix, and curing to obtain a silicone composite material with high thermal conductivity and low dielectric constant; specifically, step S3 includes: S3.1 After adding the three-dimensional filler to the embedding material, it is first ultrasonically dispersed and then stirred and mixed. The ultrasonic power is 200-400W, the dispersion time is 5-10min, the stirring speed is 300-800r / min, and the mixing time is 10-30min. This allows the three-dimensional filler to uniformly fill the gap between the transition layer and the two-dimensional filler and to be in close contact with the outer surface of the transition layer, thus obtaining the composite filler. S3.2, the composite filler and silicone matrix are mixed by low-temperature shearing at a temperature of 20-30℃, a shearing speed of 30-50 r / min, and a mixing time of 30-60 min. Then, the mixture is pre-pressed under a pressure of 10-16 MPa and then subjected to gradient heating curing. The mixture is kept at 60-80℃ for 1-2 h, at 80-110℃ for 2-3 h, and at 110-130℃ for 1-2 h. After curing, a silicone composite material with high thermal conductivity and low dielectric constant is obtained.

[0026] The silica matrix is ​​composed of hydrogen-containing silicone oil, vinyl silicone oil, and platinum catalyst, with a mass ratio of hydrogen-containing silicone oil: vinyl silicone oil: platinum catalyst = 3:2.8:0.005. The mass ratio of the composite filler to the silica matrix is ​​1:3-12. The three-dimensional filler includes at least one of spherical alumina, boron nitride microspheres, and hollow silica microspheres. The amount of the three-dimensional filler is 10-40% of the mass of the two-dimensional filler, and the particle size of the three-dimensional filler is 50-500 nm.

[0027] The ultrasonic-first, then agitated mixing method ensures that the 3D filler is uniformly dispersed and fills the gaps between the transition layer and the 2D filler, while maintaining close contact with the outer surface of the transition layer. The transition layer provides a stable contact interface for the 3D filler, enhancing the effective connection between the 3D filler and the 1D and 2D fillers, further improving the thermal conductivity network, reducing interfacial thermal resistance between fillers, and increasing the connectivity efficiency of the heat conduction path. The composite filler and silicone matrix are mixed using low-temperature, low-speed shearing, avoiding filler agglomeration and silicone matrix performance damage caused by high-temperature, high-speed processing. Pre-compression molding ensures a more uniform distribution of the composite filler within the silicone matrix, while gradient heating curing allows the silicone matrix to gradually cross-link and solidify, reducing internal stress, improving the structural stability of the material, and ensuring a tight bond between the filler and the matrix, thus guaranteeing the continuity of the thermal conductivity network.

[0028] In a preferred embodiment, the present invention provides a high thermal conductivity and low dielectric silicone composite material, which is prepared by the preparation method of the high thermal conductivity and low dielectric silicone composite material described in any one of the above claims. It includes a two-dimensional filler with a transition layer on its surface, a one-dimensional filler embedded in the transition layer, a three-dimensional filler in contact with the outer surface of the transition layer, and a silicone matrix. The fillers of different dimensions are structurally connected through the transition layer to form an interconnected thermally conductive network, achieving high thermal conductivity with a low filler content while maintaining low dielectric properties.

[0029] Example 1 10g of boron nitride was used as a two-dimensional filler and added to a mixed solvent consisting of 80g of deionized water and 20g of ethanol. Then, 0.5g of tetraethyl orthosilicate was added as a precursor. The mixture was dispersed in an ultrasonic device with a power of 300W for 20 minutes. Ammonia was then added dropwise as a regulator to adjust the pH to 9. The mixture was stirred to induce a hydrolysis and condensation reaction of the tetraethyl orthosilicate, forming a uniform precursor deposit on the boron nitride surface. 0.3g of polyethylene glycol was added to the precursor deposit mixture as a pore-forming agent, and stirring was continued for 30 minutes to form a uniform porous structure in the precursor deposit. The precursor deposit was then transformed into a transition layer, yielding the initial product.

[0030] The above-mentioned preliminary material was placed in a 50°C water bath heating environment and subjected to combined heating and ultrasonic treatment with 400W ultrasonic power for 10 minutes. 0.3g of boron-nitrogen nanotubes were added to the system as a one-dimensional filler, and high-speed shearing and mixing was performed at 1200r / min for 10 minutes to fully open the pore structure of the transition layer and disperse the boron-nitrogen nanotubes into the pores. The mixture was heated to 60°C and subjected to a heat preservation hydrolysis condensation reaction for 2 hours to solidify the pore structure of the transition layer and firmly embed the boron-nitrogen nanotubes into the pores of the transition layer. After natural cooling, the embedded material was obtained.

[0031] 2g of spherical alumina with a particle size of 200nm was added to the above-mentioned embedding material as a three-dimensional filler. The mixture was first dispersed using 300W ultrasonic power for 8 minutes, then stirred at 500r / min for 20 minutes to ensure the spherical alumina uniformly filled the gaps between the transition layer and boron nitride, and made close contact with the outer surface of the transition layer. After filtration and drying, a composite filler was obtained. Hydrogen-containing silicone oil, vinyl silicone oil, and platinum catalyst were weighed at a mass ratio of 3:2.8:0.005 and mixed evenly to prepare a silicone matrix. 10g of the above-mentioned composite filler was mixed with 60g of silicone matrix and sheared at 40r / min for 45 minutes at a low temperature of 25℃. The mixed slurry was placed in a mold and pre-pressed under a pressure of 12MPa. Gradient heating curing was then performed: first, the reaction was carried out at 70℃ for 1.5h, then at 90℃ for 2.5h, and finally at 120℃ for 1.5h. After curing, the mixture was demolded to obtain a silicone composite material with high thermal conductivity and low dielectric constant.

[0032] Example 2 8g of molybdenum disulfide was used as a two-dimensional filler and added to a mixed solvent consisting of 60g of deionized water and 30g of isopropanol. Then, 0.08g of tetrabutyl titanate was added as a precursor. The mixture was dispersed in an ultrasonic device with a power of 200W for 30 minutes. Subsequently, sodium hydroxide solution was added dropwise as a regulator to adjust the pH of the system to 10. The mixture was stirred to allow the tetrabutyl titanate to undergo a hydrolysis-condensation reaction, forming a precursor deposit on the surface of the molybdenum disulfide. 0.04g of ammonium bicarbonate was added to the precursor deposit mixture as a pore-forming agent, and the mixture was stirred for another 20 minutes to allow the precursor deposit to form a porous structure and transform into a transition layer, yielding the initial product.

[0033] The above-mentioned preliminary material was placed in a 40°C water bath heating environment and subjected to combined heating and ultrasonic treatment with 300W ultrasonic power for 20 minutes. 0.08g of alumina nanofibers were added to the system as a one-dimensional filler, and high-speed shearing and mixing was performed at 800r / min for 15 minutes to allow the alumina nanofibers to enter the pores of the transition layer. The mixed system was heated to 50°C and subjected to a heat preservation hydrolysis condensation reaction for 3 hours to solidify the pores of the transition layer and embed the alumina nanofibers into the pores, thus obtaining the embedded material.

[0034] 0.8g of boron nitride microspheres were added to the above-mentioned embedding material as a three-dimensional filler. The mixture was first dispersed using 200W ultrasonic power for 10 minutes, then stirred at 300r / min for 30 minutes. After filtration and drying, a composite filler was obtained. A silicone matrix was prepared at a mass ratio of 3:2.8:0.005. 8g of the composite filler was mixed with 24g of the silicone matrix. The mixture was sheared and mixed at 30r / min for 60 minutes at a low temperature of 20℃. It was then pre-pressed under 10MPa pressure, followed by gradient heating curing: 60℃ for 2 hours, then 80℃ for 3 hours, and finally 110℃ for 2 hours. After demolding, a silicone composite material with high thermal conductivity and low dielectric constant was obtained.

[0035] Example 3 12g of carbon nitride was used as a two-dimensional filler and added to a mixed solvent consisting of 100g of deionized water and 50g of n-butanol. Then, 1.2g of triethyl aluminate was added as a precursor. The mixture was dispersed in an ultrasonic device with a power of 500W for 10 minutes. Subsequently, triethylamine was added dropwise as a regulator to adjust the pH of the system to 8. The mixture was stirred to allow the triethyl aluminate to undergo a hydrolysis-condensation reaction, forming a precursor deposit on the surface of the carbon nitride. 0.6g of sodium dodecyl sulfate was added to the precursor deposit mixture as a pore-forming agent, and the mixture was stirred for another 40 minutes to allow the precursor deposit to form a porous structure and transform into a transition layer, yielding the initial product.

[0036] The above-mentioned preliminary material was placed in a 60°C water bath heating environment and subjected to combined heating and ultrasonic treatment with 600W ultrasonic power for 5 minutes. 0.6g of a mixed one-dimensional filler of boron nitrogen nanotubes and alumina nanofibers was added to the system and subjected to high-speed shear mixing at 1500r / min for 5 minutes to ensure that the mixed one-dimensional filler uniformly enters the pores of the transition layer. The mixed system was heated to 70°C and subjected to a heat preservation hydrolysis condensation reaction for 1 hour to solidify the pores of the transition layer and embed the mixed one-dimensional filler into the pores to obtain the embedded material.

[0037] 4.8g of silica hollow microspheres were added to the above-mentioned embedding material as a three-dimensional filler. The mixture was first dispersed using 400W ultrasonic power for 5 minutes, then stirred and mixed at 800r / min for 10 minutes. After filtration and drying, a composite filler was obtained. A silicone matrix was prepared at a mass ratio of 3:2.8:0.005. 12g of the above-mentioned composite filler was mixed with 144g of the silicone matrix. The mixture was sheared and mixed at 50r / min for 30 minutes at a low temperature of 30℃. It was then pre-pressed under 16MPa pressure, followed by gradient heating curing: 80℃ for 1 hour, then 110℃ for 2 hours, and finally 130℃ for 1 hour. After demolding, a silicone composite material with high thermal conductivity and low dielectric constant was obtained.

[0038] Example 4 10g of boron nitride was used as a two-dimensional filler and added to a mixed solvent consisting of 70g of deionized water and 30g of methanol. Then, a mixed precursor of 0.3g of tetraethyl orthosilicate and 0.2g of tetrabutyl titanate was added. The mixture was dispersed in an ultrasonic device with a power of 300W for 20 minutes. Ammonia was then added dropwise as a regulator to adjust the pH to 9. The mixture was stirred to induce a hydrolysis-condensation reaction in the mixed precursor, forming a uniform precursor deposit on the boron nitride surface. A mixed pore-forming agent of 0.2g of urea and 0.2g of polyethylene glycol was added to the precursor deposit mixture, and stirring was continued for 30 minutes to form a uniform porous structure. The precursor deposit was transformed into a transition layer, yielding the initial product.

[0039] The above-mentioned preliminary material was placed in a 50°C water bath heating environment and subjected to combined heating and ultrasonic treatment with 450W ultrasonic power for 12 minutes. 0.4g of boron-nitrogen nanotubes were added to the system as a one-dimensional filler, and high-speed shearing and mixing was performed at 1000r / min for 12 minutes to fully open the pore structure of the transition layer and disperse the boron-nitrogen nanotubes into the pores. The mixture was heated to 65°C and subjected to a thermal hydrolysis-condensation reaction for 1.8h to solidify the pore structure of the transition layer and firmly embed the boron-nitrogen nanotubes into the pores of the transition layer. After natural cooling, the embedded material was obtained.

[0040] Add 3g of a mixture of spherical alumina and boron nitride microspheres as a three-dimensional filler to the above-mentioned embedding material. First, disperse the mixture using ultrasonic power of 350W for 7 minutes, then stir and mix it at a speed of 600r / min for 15 minutes to ensure that the mixed three-dimensional filler uniformly fills the gaps between the transition layer and boron nitride and makes close contact with the outer surface of the transition layer. After filtration and drying, a composite filler is obtained. Weigh hydrogen-containing silicone oil, vinyl silicone oil and platinum catalyst at a mass ratio of 3:2.8:0.005 and mix them evenly to prepare a silicone matrix. Take 10g of the above-mentioned composite filler and mix it with 80g of silicone matrix. Shear and mix it at a speed of 45r / min for 40 minutes at a low temperature of 25℃. Place the mixed slurry in a mold and pre-press it under a pressure of 14MPa. Then, perform gradient heating curing: first, keep it at 75℃ for 1.2h, then keep it at 100℃ for 2h, and finally keep it at 125℃ for 1.2h. After curing, demold to obtain a silicone composite material with high thermal conductivity and low dielectric constant.

[0041] Comparative Example 1 The difference from Example 1 is that no pore-forming agent was added in step S1, the precursor deposit did not form a porous structure, and subsequent steps were carried out directly.

[0042] Comparative Example 2 The difference from Example 1 is that the combined heating and ultrasonic treatment and high-speed shearing step S2 were not performed; instead, boron-nitrogen nanotubes were directly added to the primary material and stirred.

[0043] Comparative Example 3 The difference from Example 1 is that no one-dimensional filler was added; instead, the composite filler was prepared by mixing the preliminary transition layer of the two-dimensional filler with the three-dimensional filler.

[0044] Comparative Example 4 The difference from Example 1 is that no three-dimensional filler was added; instead, a two-dimensional filler with embedded one-dimensional filler was used as the filler and combined with the silica matrix. The other steps and parameters were the same as in Example 1.

[0045] The silicone composite materials obtained in the examples and comparative examples were subjected to relevant performance tests. The test contents and methods are as follows: Thermal conductivity: The thermal diffusivity of the material is tested at room temperature, and the thermal conductivity is calculated in combination with density and specific heat capacity; Dielectric constant: The dielectric constant of the material is tested using a dielectric spectrometer at a test frequency of 1MHz and room temperature.

[0046] Table 1 Performance testing of silicone composite materials As shown in Table 1, compared with Example 1, Comparative Example 1 did not add a pore-forming agent, the transition layer had no porous structure, the one-dimensional filler could not achieve solid connection, the contact effect between fillers was poor, the interfacial thermal resistance was high, and the thermal conductivity was only 2.13 W / (m²). K), and the poor dispersibility of the filler leads to a significant increase in dielectric constant. This indicates that the pore-forming agent helps to promote the embedding of one-dimensional fillers and build a continuous thermally conductive network. The formation of the pore structure can ensure that the material maintains low dielectric properties while having high thermal conductivity. However, without the addition of the pore-forming agent, the thermal conductivity and dielectric properties of the silicone composite material may be directly reduced.

[0047] Comparative Example 2 did not undergo the combined heating and ultrasonic treatment and high-speed shearing steps, resulting in insufficient opening of the transition layer pores. This led to poor embedding effect of the one-dimensional filler, low bonding force with the two-dimensional filler, and inability to form a stable one-dimensional-two-dimensional filler connection structure. Consequently, the thermal conductivity and dielectric properties decreased significantly. This indicates that the combined heating and ultrasonic treatment and high-speed shearing can fully open the transition layer pores, ensuring uniform dispersion and effective embedding of the one-dimensional filler, and improving the bonding force between fillers.

[0048] In Comparative Example 3, without the addition of one-dimensional filler, the thermal conductivity network was constructed using only two-dimensional and three-dimensional fillers. The two-dimensional filler sheets were prone to stacking and agglomeration, and there were a large number of gaps between the three-dimensional filler particles. The two could only form limited point-to-surface or point-to-point contact. The connection points of the thermal conductivity path were few, and the continuous transmission path was difficult to connect. The scattering loss of electrons at the filler interface increased significantly, resulting in high interfacial thermal resistance. Ultimately, the thermal conductivity was significantly lower than that of Example 1. In Comparative Example 4, due to the lack of three-dimensional filler, the linear thermal conductivity path of the one-dimensional filler and the sheet thermal conductivity surface of the two-dimensional filler could not form a three-dimensional interpenetrating structure in three-dimensional space. Not only could the gaps between the fillers not be effectively filled, but the orientation dispersion of the one-dimensional filler and the local agglomeration of the two-dimensional filler were also prone to occur. This resulted in a large number of transmission breakpoints in the thermal conductivity network in three-dimensional space, which destroyed the continuity and integrity of the thermal conductivity network and thus significantly reduced the thermal conductivity.

[0049] In summary, the high thermal conductivity and low dielectric constant silicone composite material and its preparation method obtained by this invention achieve structural connection of fillers of different dimensions through a transition layer, forming an interconnected thermally conductive network. This effectively reduces the interfacial thermal resistance between fillers and improves the connectivity efficiency of the heat conduction path, achieving high thermal conductivity with a relatively low filler content. At the same time, this method maintains excellent low dielectric properties, solving the technical problem of poor filler contact effect and low bonding force in existing silicone composite materials, which leads to a decline in thermal conductivity and dielectric properties. The prepared silicone composite material has broad application prospects in fields such as heat dissipation of electronic devices and high-frequency communication.

[0050] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. 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 method for preparing a silicone composite material with high thermal conductivity and low dielectric constant, characterized in that, Includes the following steps: S1, the two-dimensional filler is added to an acid acid-based aqueous solvent, the pH value is adjusted to a preset range to carry out a hydrolysis and condensation reaction, so that a transition layer is deposited on the surface of the two-dimensional filler to obtain the initial product; S2, modify the transition layer of the initial material to form a porous structure, and add one-dimensional filler during the modification process so that the one-dimensional filler is in the porous structure of the transition layer to obtain an embedded material. S3, add three-dimensional filler to the embedding material, stir and mix to obtain composite filler, mix the composite filler with silicone matrix, and cure to obtain silicone composite material with high thermal conductivity and low dielectric.

2. The method for preparing the high thermal conductivity, low dielectric silica composite material as described in claim 1, characterized in that, Step S1 includes: S1.1, the two-dimensional filler is added to a solvent containing the precursor, ultrasonically dispersed, and then a regulator is added to adjust the pH value until the preset pH value is reached, so that the precursor undergoes a hydrolysis and condensation reaction to form a precursor deposit on the surface of the two-dimensional filler. S1.2, a pore-forming agent is added to form a porous structure in the precursor sediment, which is then converted into a transition layer to obtain the initial product.

3. The method for preparing the high thermal conductivity, low dielectric constant silicone composite material as described in claim 2, characterized in that, The mass ratio of the two-dimensional filler to the solvent is 1:6-30. The two-dimensional filler includes one of boron nitride, molybdenum disulfide, and carbon nitride. The solvent includes water and organic matter. The organic matter includes one of ethanol, isopropanol, methanol, and n-butanol. The modifier is selected from one of ammonia, sodium hydroxide, and triethylamine. The precursor includes at least one of silicate ester, titanate ester, and aluminate ester precursors. The amount of the precursor is 1-10% of the mass of the two-dimensional filler. The pore-forming agent includes at least one of polyethylene glycol, ammonium bicarbonate, urea, and sodium dodecyl sulfate. The amount of the pore-forming agent is 0.5-5% of the mass of the two-dimensional filler. The ultrasonic dispersion power is 200-500W, and the dispersion time is 10-30min.

4. The method for preparing the high thermal conductivity, low dielectric silicone composite material as described in claim 1, characterized in that, Step S2 includes: S2.1, the primary material is subjected to a combination of heating and ultrasonic treatment, one-dimensional filler is added, high-speed shearing is performed, and the mixture is homogenized to form a porous structure in the transition layer; S2.2, a hydrolysis-condensation reaction is carried out to solidify the pore structure of the transition layer, and the one-dimensional filler is embedded in the pores of the transition layer to obtain the embedded material.

5. The method for preparing the high thermal conductivity, low dielectric silicone composite material as described in claim 4, characterized in that, The heating temperature for the combined heating and ultrasonic treatment is 40-60℃, the ultrasonic power is 300-600W, and the treatment time is 5-20min; the high-speed shear mixing speed is 800-1500r / min, and the mixing time is 5-15min; the holding temperature for the continued hydrolysis and condensation is 50-70℃, and the holding time is 1-3h; the one-dimensional filler includes at least one of boron-nitrogen nanotubes and alumina nanofibers, and the amount of one-dimensional filler is 1-5% of the mass of the two-dimensional filler.

6. The method for preparing the high thermal conductivity, low dielectric silica composite material as described in claim 1, characterized in that, Step S3 includes S3.1, after adding the three-dimensional filler to the embedding material, it is first ultrasonically dispersed and then stirred and mixed. The ultrasonic power is 200-400W, the dispersion time is 5-10min, the stirring speed is 300-800r / min, and the mixing time is 10-30min, so that the three-dimensional filler is uniformly filled in the gap between the transition layer and the two-dimensional filler and is in close contact with the outer surface of the transition layer, thus obtaining the composite filler. S3.2, the composite filler and silicone matrix are mixed by low-temperature shearing at a temperature of 20-30℃, a shearing speed of 30-50 r / min, and a mixing time of 30-60 min. Then, the mixture is pre-pressed under a pressure of 10-16 MPa and then subjected to gradient heating curing. The mixture is kept at 60-80℃ for 1-2 h, at 80-110℃ for 2-3 h, and at 110-130℃ for 1-2 h. After curing, a silicone composite material with high thermal conductivity and low dielectric constant is obtained.

7. The method for preparing the high thermal conductivity, low dielectric silicone composite material as described in claim 1, characterized in that, The silica matrix is ​​composed of hydrogen-containing silicone oil, vinyl silicone oil, and platinum catalyst, with a mass ratio of hydrogen-containing silicone oil: vinyl silicone oil: platinum catalyst = 3:2.8:0.

005. The mass ratio of the composite filler to the silica matrix is ​​1:3-12. The three-dimensional filler includes at least one of spherical alumina, boron nitride microspheres, and hollow silica microspheres. The amount of the three-dimensional filler is 10-40% of the mass of the two-dimensional filler, and the particle size of the three-dimensional filler is 50-500 nm.

8. A high thermal conductivity, low dielectric silica composite material, prepared by the method for preparing the high thermal conductivity, low dielectric silica composite material according to any one of claims 1-7, characterized in that, It includes two-dimensional fillers with a transition layer on the surface, one-dimensional fillers embedded in the transition layer, three-dimensional fillers in contact with the outer surface of the transition layer, and silicone matrix.

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