High-thermal-conductivity low-specific-gravity composite gel and preparation method thereof

Abstract

The invention provides a composite gel with high thermal conductivity and low specific gravity and a preparation method thereof, and belongs to the technical field of heat-conducting functional materials, the composite gel comprises a heat-conducting filler system accounting for 50-80% of the weight of the composite gel and a gel matrix accounting for 20-50% of the weight of the composite gel, the heat-conducting filler system comprises hexagonal boron nitride, hollow aluminum powder and a powder surface modifier, the hexagonal boron nitride, the hollow aluminum powder and the powder surface modifier respectively account for 24%-50%, 25%-55% and 0.1%-1.0% of the weight of the composite gel, the gel matrix comprises matrix resin, a cross-linking agent and a curing agent, and the matrix resin, the cross-linking agent and the curing agent respectively account for 18%-45%, 1%-4% and 0.5%-1% of the weight of the composite gel. According to the invention, a high-thermal-conductivity path-lightweight skeleton composite structure is constructed, and the composite structure has the advantages of high thermal conductivity, low specific gravity and high insulativity.

Description

Technical Field

[0001] This application relates to the field of thermally conductive functional materials technology, and in particular to a high thermal conductivity, low specific gravity composite gel and its preparation method. Background Technology

[0002] As new energy vehicles develop towards higher voltage and higher power density, the heat dissipation requirements of battery thermal management systems are further increasing, and the requirements for thermal conductive materials have shifted from single thermal conductivity to multi-functional integration of "lightweight and high thermal conductivity".

[0003] Existing traditional thermally conductive gel materials for new energy vehicles have the following technical drawbacks: they use alumina, zinc oxide, aluminum hydroxide, etc., as thermally conductive fillers, with thermal conductivity generally below 6 W / (m·K). Furthermore, to improve thermal conductivity, the filler content needs to be increased (usually ≥70%), leading to an increase in material specific gravity (≥2.5 g / cm³). 3 This cannot meet the requirements for lightweight design.

[0004] Boron nitride (h-BN) has a graphite-like layered structure and excellent thermal conductivity (≥300 W / (m·K) in-plane). However, the layers are prone to agglomeration and have high oil absorption, making it difficult to achieve high-quality filler fractions. Therefore, the improvement of the thermal conductivity of the gel by a single hexagonal boron nitride (h-BN) is limited (usually ≤5 W / (m·K)). Meanwhile, the density of h-BN (2.27 g / cm³) is also limited. 3 The weight is still too high, and the lightweighting effect is not good.

[0005] Hollow aluminum powder has a low specific gravity (0.3~0.8 g / cm³). 3 While aluminum powder can significantly reduce the overall density of the material, it is conductive and has a breakdown voltage of less than 3 kV / mm when used alone, which cannot meet the insulation requirements of new energy battery packs.

[0006] Existing composite thermally conductive gels lack optimized filler synergy and interfacial bonding, resulting in a trade-off between high thermal conductivity, low specific gravity, and insulation. Furthermore, the gels exhibit insufficient mechanical strength and aging resistance. Therefore, developing a composite gel material that combines high thermal conductivity, low specific gravity, and good insulation through the synergistic effect of hexagonal boron nitride and hollow aluminum powder is crucial for addressing the thermal management material requirements of new energy vehicles, necessitating lightweight and thermally conductive materials. Summary of the Invention

[0007] In view of this, embodiments of this application provide a high thermal conductivity, low specific gravity composite gel and its preparation method, which at least partially solves the problems of "high thermal conductivity, low specific gravity and insulation cannot be obtained at the same time" and insufficient mechanical strength and aging resistance in the prior art.

[0008] In a first aspect, embodiments of this application provide a thermally conductive filler system comprising 50% to 80% of the composite gel by weight and a gel matrix comprising 20% ​​to 50% by weight. The thermally conductive filler system comprises hexagonal boron nitride, hollow aluminum powder, and a powder surface modifier, wherein the hexagonal boron nitride, hollow aluminum powder, and powder surface modifier comprise 24% to 50%, 25% to 55%, and 0.1% to 1.0% of the composite gel by weight, respectively. The gel matrix comprises a matrix resin, a crosslinking agent, and a curing agent, wherein the matrix resin, crosslinking agent, and curing agent comprise 18% to 45%, 1% to 4%, and 0.5% to 1% of the composite gel by weight, respectively.

[0009] According to a specific implementation of this application, the hexagonal boron nitride is a micron-sized lamellar crystal with a thickness ≤1μm, a particle size of 15~50μm, and an in-plane thermal conductivity ≥300 W / (m·K).

[0010] According to a specific implementation of this application, the hollow aluminum powder has a particle size of 10~80 μm, a hollowness of 50%~80%, an aluminum shell thickness of 1~5 μm, and a specific gravity of 0.4~0.7 g / cm³. 3 .

[0011] According to one specific implementation of the embodiments of this application, the powder surface modifier is a vinyl silane coupling agent oligomer with a degree of polymerization of 3 to 10.

[0012] According to a specific implementation of an embodiment of this application, the matrix resin is a vinyl silicone resin, and the viscosity of the vinyl silicone resin is 100~1000 mPa·s.

[0013] According to one specific implementation of the embodiments of this application, the crosslinking agent is a hydrogen-containing silicone oil with a hydrogen content of 0.05% to 0.36%.

[0014] According to one specific implementation of this application, the curing agent is a platinum catalyst with a content of 3000 ppm.

[0015] Secondly, embodiments of this application also provide a method for preparing a high thermal conductivity, low specific gravity composite gel as described in any embodiment of the first aspect, the method comprising: Surface modification of hexagonal boron nitride and hollow aluminum powder: Hexagonal boron nitride and hollow aluminum powder are added to anhydrous ethanol and ultrasonically dispersed. A powder surface modifier is added at 0.5%~2% of the weight of hollow aluminum powder to form a suspension. The suspension is stirred and reacted at 60~80℃. A crosslinking agent is added at 1%~5% of the weight of the added powder surface modifier and stirred and reacted at 10~20℃. The suspension is atomized into micron-sized spherical droplets using a centrifugal spray dryer. After drying, a core-shell composite filler of hollow aluminum powder-hexagonal boron nitride is obtained. Gel preparation: The matrix resin, crosslinking agent, and curing agent are mixed in proportion and stirred at room temperature to form a uniform resin matrix; the obtained core-shell composite filler is gradually added to the resin matrix and mechanically stirred at 50~70℃ while being ultrasonically dispersed; stirring is continued and vacuum degassing is performed to remove air bubbles, thus obtaining the composite gel product.

[0016] According to a specific implementation of the present application, in the surface modification step of hexagonal boron nitride and hollow aluminum powder, the ultrasonic dispersion time is 10-20 minutes, the ultrasonic dispersion power is 150-250W, the stirring reaction is carried out at 60-80℃ for 30-60 minutes, and the stirring reaction is carried out at 10-20℃ for 5-15 minutes.

[0017] According to a specific implementation of the embodiments of this application, in the gel preparation step, the mechanical stirring time is 30-60 minutes, the mechanical stirring speed is 500-1000 r / min, the ultrasonic dispersion power is 200-400W, and the ultrasonic dispersion time is 20-40 minutes.

[0018] Beneficial effects: The high thermal conductivity, low specific gravity composite gel and its preparation method described in this application have advantages over traditional fillers, including high thermal conductivity, low specific gravity, and high insulation. The composite gel has a thermal conductivity ≥10 W / (m·K) and a material specific gravity ≤2.0 g / cm³. 3 Compared to traditional thermally conductive gels of the same specific gravity, its thermal conductivity is increased by 2 to 5 times, and its breakdown voltage meets the requirement of ≥10 kV / mm, making it suitable for lightweight thermal management scenarios. Details are as follows: Construction of thermal conduction pathways: Hollow aluminum powder serves as a thermally conductive "skeleton," with heat transferred along the outer shell of the aluminum powder. Hexagonal boron nitride (h-BN) sheets are uniformly dispersed after surface modification and coated on the surface of the hollow aluminum powder. The "face-to-face" overlap between the sheets acts as a "thermal bridge," forming a highly efficient thermally conductive network. The thermal conductivity is significantly higher than that of the "point-to-point" contact between hollow aluminum powders, effectively improving the thermal conductivity of the gel. Lightweighting is achieved through the hollow structure of the hollow aluminum powder (hollow ratio 50%~80%), which significantly reduces the overall density of the filler system, with a specific gravity of 0.4~0.7 g / cm³. 3 It is much lower than h-BN (2.27 g / cm³). 3 It combines high filler content with traditional thermally conductive fillers, effectively balancing the contradiction between high filler content and low specific gravity; Insulation performance: Hexagonal boron nitride is coated on the surface of hollow aluminum powder, forming an effective insulation barrier with a "core-shell". At the same time, the powder surface modifier (vinyl oligomer) forms an organic film on the surface of the composite filler, further improving the insulation performance. Detailed Implementation

[0019] The embodiments of this application are described in detail below.

[0020] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this application, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0022] Furthermore, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the described aspects can be practiced without these specific details.

[0023] In the first aspect, embodiments of this application provide a high thermal conductivity, low specific gravity composite gel, specifically involving a gel material based on a composite of hexagonal boron nitride and hollow aluminum powder microspheres, which has both high thermal conductivity, low specific gravity and excellent electrical properties, and is suitable for lightweight thermal conductive component scenarios such as thermal management of new energy batteries, aerospace and drones.

[0024] This high thermal conductivity, low specific gravity composite gel comprises a thermally conductive filler system comprising 50%–80% of the composite gel by weight and a gel matrix comprising 20%–50% of the composite gel. The thermally conductive filler system comprises hexagonal boron nitride, hollow aluminum powder, and a powder surface modifier, which comprise 24%–50%, 25%–55%, and 0.1%–1.0% of the composite gel by weight, respectively. The gel matrix comprises a matrix resin, a crosslinking agent, and a curing agent, which comprise 18%–45%, 1%–4%, and 0.5%–1% of the composite gel by weight, respectively.

[0025] In this embodiment, by controlling the weight percentage of the thermally conductive filler system to 50%~80% and setting the weight percentage of the gel matrix to 20%~50%, the thermal conductivity of the composite gel can be significantly improved while ensuring good formability and mechanical properties. Specifically, hexagonal boron nitride, as a high thermal conductivity insulating material, accounts for 24%~50% of the composite gel by weight. It has excellent thermal conductivity and can construct an effective thermal conduction path. Hollow aluminum powder accounts for 25%~55% of the composite gel by weight. The hollow structure not only reduces the overall density of the composite gel, achieving a low specific gravity, but the aluminum powder itself also has a certain thermal conductivity, working synergistically with hexagonal boron nitride to further optimize the thermal conduction network. The powder surface modifier, accounting for 0.1%~1.0% of the composite gel by weight, can improve the interfacial compatibility between hexagonal boron nitride and hollow aluminum powder and the gel matrix, reducing interfacial thermal resistance and thus improving the thermal conductivity efficiency of the composite material. For the gel matrix, 18% to 45% by weight of matrix resin serves as the main matrix component, providing basic structural support and molding basis for the composite gel; 1% to 4% of crosslinking agent enables the matrix resin to form a three-dimensional network structure, enhancing the mechanical strength and stability of the gel; and 0.5% to 1% of curing agent promotes the crosslinking reaction, ensuring that the gel matrix can be cured and molded under suitable conditions, giving the composite gel good comprehensive properties.

[0026] Furthermore, the hexagonal boron nitride is a micron-sized lamellar crystal with a thickness ≤1μm, a particle size of 15~50μm, and an in-plane thermal conductivity ≥300 W / (m·K).

[0027] Furthermore, the hollow aluminum powder has a particle size of 10-80 μm, a hollowness of 50%-80%, an aluminum shell thickness of 1-5 μm, and a specific gravity of 0.4-0.7 g / cm³. 3 .

[0028] Furthermore, the powder surface modifier is a vinyl silane coupling agent oligomer with a degree of polymerization of 3 to 10.

[0029] Furthermore, the matrix resin is a vinyl silicone resin with a viscosity of 100~1000 mPa·s and is a room temperature curing type.

[0030] Furthermore, the crosslinking agent is a hydrogen-containing silicone oil with a hydrogen content of 0.05% to 0.36%.

[0031] Furthermore, the curing agent is a platinum catalyst with a content of 3000 ppm.

[0032] Secondly, embodiments of this application also provide a method for preparing a high thermal conductivity, low specific gravity composite gel as described in any embodiment of the first aspect, the method comprising: Surface modification of hexagonal boron nitride and hollow aluminum powder: Hexagonal boron nitride and hollow aluminum powder are added to anhydrous ethanol and ultrasonically dispersed. A powder surface modifier is added at 0.5%~2% of the weight of hollow aluminum powder to form a suspension. The suspension is stirred and reacted at 60~80℃. A crosslinking agent is added at 1%~5% of the weight of the added powder surface modifier and stirred and reacted at 10~20℃. The suspension is atomized into micron-sized spherical droplets using a centrifugal spray dryer. After drying, a core-shell composite filler of hollow aluminum powder-hexagonal boron nitride is obtained. Gel preparation: The matrix resin, crosslinking agent, and curing agent are mixed in proportion and stirred at room temperature to form a uniform resin matrix; the obtained core-shell composite filler is gradually added to the resin matrix and mechanically stirred at 50~70℃ while being ultrasonically dispersed; stirring is continued and vacuum degassing is performed to remove air bubbles, thus obtaining the composite gel product.

[0033] Furthermore, in the surface modification steps of hexagonal boron nitride and hollow aluminum powder, the ultrasonic dispersion time is 10-20 minutes, the ultrasonic dispersion power is 150-250W, the stirring reaction is carried out at 60-80℃ for 30-60 minutes, and the stirring reaction is carried out at 10-20℃ for 5-15 minutes.

[0034] Furthermore, in the gel preparation step, the mechanical stirring time is 30-60 minutes, the mechanical stirring speed is 500-1000 r / min, the ultrasonic dispersion power is 200-400W, and the ultrasonic dispersion time is 20-40 minutes.

[0035] In one specific embodiment, the preparation of a high thermal conductivity, low specific gravity composite gel includes the following steps: (1) Surface modification of hexagonal boron nitride (h-BN) and hollow aluminum powder: Hexagonal boron nitride (h-BN) and hollow aluminum powder were added to anhydrous ethanol and ultrasonically dispersed for 10-20 minutes (power 150-250W). Vinyl silane coupling agent oligomers were added at 0.5%-2% of the weight of the hollow aluminum powder to form a suspension. The mixture was stirred and reacted at 60-80℃ for 30-60 minutes. A crosslinking agent with a hydrogen content of 0.05-0.36% was added at 1%-5% of the added vinyl silane coupling agent oligomers, and the mixture was stirred and reacted at 10-20℃ for 5-15 minutes. The suspension was atomized into micron-sized spherical droplets using a centrifugal spray dryer. After drying, a core-shell composite filler of hollow aluminum powder-hexagonal boron nitride (h-BN) was obtained. The vinyl coupling agent oligomers coated on the surface of the composite filler underwent a crosslinking reaction with hydrogen-containing silicone oil to form an organic coating film, ensuring that boron nitride is tightly adsorbed on the surface of the hollow aluminum powder, forming a stable core-shell granulation structure.

[0036] (2) Gel preparation: Mix the matrix resin, crosslinking agent, and curing agent in proportion, and stir at room temperature for 20-30 minutes to form a uniform resin matrix. Gradually add the core-shell composite filler prepared in step (1) into the resin matrix, and mechanically stir at 50-70℃ for 30-60 minutes (500-1000 r / min), while simultaneously using ultrasonic dispersion (200-400 W power, 20-40 minutes) to ensure that the filler does not agglomerate. Continue stirring for 15-20 minutes, and remove air bubbles under vacuum (vacuum degree ≤ -0.09 MPa, 10-20 minutes) to obtain the gel product.

[0037] In this embodiment, the crosslinking agent is added in steps. In the first step, during the dispersion of the powder and ethanol, a very small amount is added at a weight ratio of 1% to 5% of the vinyl silane coupling agent oligomer, primarily to allow the vinyl silane coupling agent to undergo some crosslinking. In the second step, a larger amount of the crosslinking agent is added during gel preparation, mainly to crosslink the vinyl silicone resin. The main principle behind these two steps is the reaction between hydrogen-containing groups and vinyl groups.

[0038] The performance of the high thermal conductivity, low specific gravity composite gel of this application is illustrated below through specific embodiments.

[0039] Example 1 The components include (by weight percentage): Thermally conductive filler system: 70%, of which: hexagonal boron nitride (h-BN): 25% (particle size 25μm, layer thickness 0.8μm, in-plane thermal conductivity 320W / (m·K)); hollow aluminum powder: 44.5% (particle size 50μm, hollowness 70%, Al shell thickness 3μm, specific gravity 0.5g / cm³); vinyl silane coupling agent oligomer, degree of polymerization 6, addition amount 0.5%; Gel matrix: 30%, of which vinyl silicone resin: 28% (viscosity 500 mPa·s); crosslinking agent: hydrogen-containing silicone oil with hydrogen content of 0.18%, accounting for 1.3%; platinum catalyst: 0.7%, content 3000 ppm.

[0040] Properties: The composite gel has a thermal conductivity of 10.5 W / (m·K) and a specific gravity of 1.6 g / cm³. 3 The voltage breakdown is 13kV / mm. Example 2 The components include (by weight percentage): Thermally conductive filler system: 80%, of which hexagonal boron nitride (h-BN): 30% (particle size 25μm, lamellar thickness 0.8μm, in-plane thermal conductivity 320W / (m·K)); hollow aluminum powder: 49.2% (particle size 50μm, hollowness 70%, Al shell thickness 3μm, specific gravity 0.5g / cm³). 3 Vinylsilane coupling agent oligomer, degree of polymerization 6, addition amount 0.8%; Gel matrix: 20%, of which vinyl silicone resin: 18.3% (viscosity 500 mPa·s); crosslinking agent: hydrogen-containing silicone oil with hydrogen content of 0.18%, accounting for 1%; platinum catalyst: 0.7%, content of 3000 ppm.

[0041] Properties: The gel has a thermal conductivity of 12 W / (m·K) and a specific gravity of 1.9 g / cm³. 3 The voltage breakdown is 11kV / mm.

[0042] Comparative Example 1 (Single Alumina Gel) The components include (by weight percentage): Alumina: 70%, particle size 50μm; Gel matrix: 30%, of which vinyl silicone resin: 28% (viscosity 500 mPa·s); crosslinking agent: hydrogen-containing silicone oil with hydrogen content of 0.18%, accounting for 1.3%; platinum catalyst: 0.7%, content of 3000 ppm.

[0043] Performance: Thermal conductivity is 6 W / (m·K), specific gravity is 3.1 g / cm³ 3 The breakdown voltage was 11 kV / mm. Comparative Example 2 (Single Aluminum Powder Gel) The components include (by weight percentage): Aluminum: 80%, particle size 50μm; Gel matrix: 20%, of which vinyl silicone resin: 18.3% (viscosity 500 mPa·s); crosslinking agent: hydrogen-containing silicone oil with hydrogen content of 0.18%, accounting for 1%; platinum catalyst: 0.7%, content of 3000 ppm.

[0044] Performance: Thermal conductivity is 8.5 W / (m·K), specific gravity is 2.6 g / cm³ 3 The voltage breakdown is 2kV / mm.

[0045] The experimental results from the examples and comparative examples demonstrate that the high thermal conductivity and low specific gravity composite gel prepared in this invention has significant performance advantages. Compared with the gel in Comparative Example 1 that uses only alumina as a thermally conductive filler, Example 1, with the same total filler addition (70%), shows an increase in thermal conductivity from 6 W / (m·K) to 10.5 W / (m·K), an increase of up to 75%, while the material specific gravity increases from 3.1 g / cm³. 3 Significantly reduced to 1.6 g / cm³ 3 The thermal conductivity decreased by approximately 48.4%, and the voltage breakdown strength (13 kV / mm) was also superior to that of Comparative Example 1 (11 kV / mm). Compared to the gel in Comparative Example 2, which used a single solid aluminum powder as the thermally conductive filler, Example 2, with a similar total filler content (80%), increased the thermal conductivity from 8.5 W / (m·K) to 12 W / (m·K), an increase of approximately 41.2%, and the material specific gravity increased from 2.6 g / cm³. 3 Reduced to 1.9 g / cm³ 3 The thermal conductivity decreased by approximately 26.9%, with a significant increase in voltage breakdown strength from 2kV / mm to 11kV / mm, demonstrating excellent insulation performance. This fully demonstrates that by compounding highly thermally conductive hexagonal boron nitride (h-BN) with low-density hollow aluminum powder and modifying its surface with vinylsilane coupling agent oligomers, the thermal conductivity of the composite gel can be synergistically improved, while effectively reducing the material's specific gravity and maintaining good electrical insulation performance. This achieves a good balance between high thermal conductivity and low specific gravity, solving the problem of single fillers struggling to balance thermal conductivity, specific gravity, and insulation performance.

[0046] This application presents a high thermal conductivity, low specific gravity composite gel, a gel material based on a composite of hexagonal boron nitride and hollow aluminum powder microspheres, possessing both high thermal conductivity, low specific gravity, and excellent electrical properties. It is suitable for lightweight thermally conductive components in applications such as thermal management of new energy batteries, aerospace, and drones. By optimizing the ratio of hexagonal boron nitride to hollow aluminum powder, surface modification processes, spherical granulation of composite fillers, and gel matrix formulation, a "high thermal conductivity pathway-lightweight framework" composite structure is constructed, achieving a thermal conductivity ≥10 W / (m·K) and a specific gravity ≤2.0 g / cm³. 3 A breakthrough in performance with a voltage breakdown of ≥10 kV / mm, while ensuring the mechanical flexibility and long-term stability of the gel.

[0047] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A high thermal conductivity, low specific gravity synthetic gel, characterized in that, The composite gel comprises a thermally conductive filler system comprising 50%–80% by weight and a gel matrix comprising 20%–50% by weight. The thermally conductive filler system includes hexagonal boron nitride, hollow aluminum powder, and powder surface modifier, which comprise 24%–50%, 25%–55%, and 0.1%–1.0% by weight of the composite gel, respectively. The gel matrix comprises a matrix resin, a crosslinking agent, and a curing agent, which comprise 18%–45%, 1%–4%, and 0.5%–1% by weight of the composite gel, respectively.

2. The high thermal conductivity, low specific gravity composite gel and its preparation method according to claim 1, characterized in that, The hexagonal boron nitride is a micron-sized lamellar crystal with a thickness of ≤1μm, a particle size of 15~50μm, and an in-plane thermal conductivity of ≥300 W / (m·K).

3. The high thermal conductivity, low specific gravity composite gel and its preparation method according to claim 1, characterized in that, The hollow aluminum powder has a particle size of 10-80 μm, a hollowness of 50%-80%, an aluminum shell thickness of 1-5 μm, and a specific gravity of 0.4-0.7 g / cm³. 3 .

4. The high thermal conductivity, low specific gravity composite gel and its preparation method according to claim 1, characterized in that, The powder surface modifier is a vinyl silane coupling agent oligomer with a degree of polymerization of 3 to 10.

5. The high thermal conductivity, low specific gravity composite gel and its preparation method according to claim 1, characterized in that, The matrix resin is a vinyl silicone resin with a viscosity of 100~1000 mPa·s.

6. The high thermal conductivity, low specific gravity composite gel and its preparation method according to claim 1, characterized in that, The crosslinking agent is hydrogen-containing silicone oil, and the hydrogen content of the hydrogen-containing silicone oil is 0.05%~0.36%.

7. The high thermal conductivity, low specific gravity composite gel and its preparation method according to claim 1, characterized in that, The curing agent is a platinum catalyst with a content of 3000 ppm.

8. A method for preparing a high thermal conductivity, low specific gravity composite gel as described in any one of claims 1-7, characterized in that, The method includes: Surface modification of hexagonal boron nitride and hollow aluminum powder: Hexagonal boron nitride and hollow aluminum powder are added to anhydrous ethanol and ultrasonically dispersed. A powder surface modifier is added at 0.5%~2% of the weight of hollow aluminum powder to form a suspension. The suspension is stirred and reacted at 60~80℃. A crosslinking agent is added at 1%~5% of the weight of the added powder surface modifier and stirred and reacted at 10~20℃. The suspension is atomized into micron-sized spherical droplets using a centrifugal spray dryer. After drying, a core-shell composite filler of hollow aluminum powder-hexagonal boron nitride is obtained. Gel preparation: The matrix resin, crosslinking agent, and curing agent are mixed in proportion and stirred at room temperature to form a uniform resin matrix; the obtained core-shell composite filler is gradually added to the resin matrix and mechanically stirred at 50~70℃ while being ultrasonically dispersed; stirring is continued and vacuum degassing is performed to remove air bubbles, thus obtaining the composite gel product.

9. The preparation method according to claim 8, characterized in that, In the surface modification steps of hexagonal boron nitride and hollow aluminum powder, the ultrasonic dispersion time is 10~20 minutes, the ultrasonic dispersion power is 150~250W, the stirring reaction is carried out at 60~80℃ for 30~60 minutes, and the stirring reaction is carried out at 10~20℃ for 5~15 minutes.

10. The preparation method according to claim 8, characterized in that, In the gel preparation step, the mechanical stirring time is 30-60 minutes, the mechanical stirring speed is 500-1000 r / min, the ultrasonic dispersion power is 200-400W, and the ultrasonic dispersion time is 20-40 minutes.