Silicon carbide-boron nitride three-dimensional heat-conducting framework material as well as preparation method and application thereof

Abstract

The invention relates to a silicon carbide-boron nitride three-dimensional heat conduction framework material and a preparation method and application thereof.The preparation method comprises the steps that boron nitride nanosheets are prepared into dispersion liquid, the pH of the dispersion liquid is adjusted through ammonia, then an organic silicon source is added for a reaction, and a precursor is obtained; the precursor comprises a boron nitride nanosheet and SiO2 nanoparticles loaded on the surface of the boron nitride nanosheet; mixing the precursor, polyamide acid and trimethylamine in a solvent, and performing freeze drying treatment to obtain composite aerogel; and sequentially carrying out thermal imidization treatment, carbonization treatment and carbon thermal reduction reaction on the composite aerogel to obtain the silicon carbide-boron nitride three-dimensional heat-conducting framework material. According to the preparation method, SiC nanowires are efficiently connected with BNNS to form a microstructure welded continuous heat-conducting network, and the prepared silicon carbide-boron nitride three-dimensional heat-conducting framework material has excellent heat conductivity, electric insulativity and flexibility when being used as a thermal interface material and is wide in application prospect.

Description

Technical Field

[0001] This invention relates to the field of electronic industry technology, and in particular to a silicon carbide-boron nitride three-dimensional thermally conductive framework material, its preparation method, and its application. Background Technology

[0002] With the rapid development of flexible electronics, thermal interface materials not only need to possess good flexibility to ensure a tight fit between heat-generating and heat-dissipating components during bending, but also require higher standards for thermal conductivity and electrical insulation. While using high thermal conductivity fillers combined with a soft, elastic polymer matrix to improve thermal conductivity is a simple and efficient method, traditional three-dimensional high thermal conductivity filler preparation methods often result in extremely high interfacial thermal resistance due to weak connections between the filler interfaces, limiting the improvement of thermal conductivity. Therefore, the amount of traditional thermally conductive fillers added is often high. However, excessively high filler content in thermal interface materials can actually reduce the flexibility or electrical insulation of the material, failing to meet the practical application requirements in the field of flexible electronics. Summary of the Invention

[0003] Therefore, it is necessary to address the above-mentioned problems by providing a silicon carbide-boron nitride three-dimensional thermally conductive framework material, its preparation method, and its applications. The preparation method involves efficiently connecting silicon carbide nanowires with boron nitride nanosheets to form a continuous thermally conductive network with microstructure welding. The resulting silicon carbide-boron nitride three-dimensional thermally conductive framework material exhibits excellent thermal conductivity, electrical insulation, and flexibility when used as a thermal interface material, and has broad application prospects.

[0004] A method for preparing a silicon carbide-boron nitride three-dimensional thermally conductive framework material includes the following steps:

[0005] Boron nitride nanosheets were prepared into a dispersion and the pH of the dispersion was adjusted with ammonia. Then, an organosilicon source was added to react and a precursor was obtained. The precursor included boron nitride nanosheets and SiO2 nanoparticles loaded on the surface of the boron nitride nanosheets.

[0006] The precursor, polyamic acid, and trimethylamine were mixed in a solvent and then freeze-dried to obtain a composite aerogel.

[0007] The composite aerogel was subjected to thermal imidization, carbonization and carbothermal reduction in sequence to obtain a silicon carbide-boron nitride three-dimensional thermally conductive framework material.

[0008] In one embodiment, the ratio of the lateral dimension to the thickness of the boron nitride nanosheet is 400:1 to 5000:1.

[0009] In one embodiment, the boron nitride nanosheets have an average lateral dimension of 2 μm to 5 μm and an average thickness of 1 nm to 5 nm.

[0010] In one embodiment, the precursor preparation process satisfies at least one of the following conditions:

[0011] (1) The concentration of boron nitride nanosheets in the dispersion is 0.05 g / mL to 0.2 g / mL;

[0012] (2) The mass ratio of the boron nitride nanosheets to the organosilicon source is 1:1 to 1:4;

[0013] (3) The pH of the dispersion is adjusted to 6-8 using ammonia;

[0014] (4) The solvent in the dispersion is selected from a water-alcohol solution, wherein the volume ratio of water to alcohol in the water-alcohol solution is 1:10 to 1:3.

[0015] In one embodiment, the mass ratio of the polyamic acid to the precursor and the trimethylamine is 1:(1-4):0.2.

[0016] In one embodiment, the step of fabricating the composite aerogel into a silicon carbide-boron nitride three-dimensional thermally conductive framework material satisfies at least one of the following conditions:

[0017] (1) The temperature of the thermal imidization treatment is 300℃~350℃, and the time is 0.5h~3h;

[0018] (2) The carbonization treatment is carried out at a temperature of 800℃ to 1200℃ for a time of 0.5h to 2h;

[0019] (3) The temperature of the carbothermic reduction reaction is 1400℃~1600℃ and the time is 0.5h~2h.

[0020] A silicon carbide-boron nitride three-dimensional thermally conductive framework material prepared by the method described above.

[0021] In one embodiment, the mass fraction of silicon carbide in the silicon carbide-boron nitride three-dimensional thermally conductive framework material is less than 10%.

[0022] A thermal interface material includes: a polymer matrix and a silicon carbide-boron nitride three-dimensional thermally conductive framework material distributed in the polymer matrix as described above.

[0023] In one embodiment, the mass fraction of the silicon carbide-boron nitride three-dimensional thermally conductive framework material in the thermal interface material is 5 wt% to 25 wt%.

[0024] The above preparation method first successfully loads SiO2 nanoparticles onto the surface of boron nitride nanosheets (BNNS) via ammonia-catalyzed hydrolysis, then constructs a composite aerogel (PAA-SiO2-BNNS) with a directional structure via directional freeze-drying, and finally forms a continuous heat-conducting network with microstructure welding through sequential thermal imidization, carbonization, and carbothermal reduction reactions. In the preparation method provided by this invention, on the one hand, the layered structure of BNNS has good thermal conductivity and good orientation during freeze-drying, which is beneficial to the directional transmission of thermal conductivity, thereby effectively improving the thermal conductivity of the obtained silicon carbide-boron nitride three-dimensional thermally conductive framework material (SiC-BNNS); on the other hand, PAA-SiO2-BNNS is first converted into polyimide-based aerogel (PI-SiO2-BNNS) through thermal imidization treatment, and then converted into carbon-based compound (C-SiO2-BNNS) through carbonization treatment. Then, C-SiO2 is grown into SiC nanowires with good thermal conductivity and electrical insulation through carbothermal reduction reaction to obtain SiC-BNNS. This effectively enhances the connection between BNNS, improves the uniformity and structural stability of the connection between BNNS, and further effectively reduces the interfacial thermal resistance between BNNS and improves the thermal conductivity.

[0025] Therefore, the SiC-BNNS three-dimensional thermally conductive framework material prepared by the method of the present invention has excellent thermal conductivity, electrical insulation and flexibility when used as a thermal interface material, and has broad application prospects. Attached Figure Description

[0026] 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 recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 A physical image of the SiC-BNNS three-dimensional thermally conductive framework material;

[0028] Figure 2 SEM image of SiC-BNNS three-dimensional thermally conductive framework material. Detailed Implementation

[0029] To facilitate understanding of the present invention, it will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. Rather, these embodiments or examples are provided to make the disclosure of the present invention more thorough and complete.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments or examples only and is not intended to limit the invention. The optional scope of the term "and / or" as used herein includes any one of two or more of the related listed items, as well as any and all combinations of the related listed items, including any two related listed items, any more related listed items, or a combination of all related listed items.

[0031] The method for preparing the silicon carbide-boron nitride three-dimensional thermally conductive framework material provided by this invention specifically includes the following steps:

[0032] S1. Boron nitride nanosheets are prepared into a dispersion and the pH of the dispersion is adjusted by ammonia. Then, an organosilicon source is added to react and a precursor is obtained. The precursor includes boron nitride nanosheets and SiO2 nanoparticles loaded on the surface of the boron nitride nanosheets.

[0033] S2. The precursor, polyamic acid (PAA), and trimethylamine are mixed in a solvent and then freeze-dried to obtain a composite aerogel.

[0034] S3. The composite aerogel is subjected to thermal imidization, carbonization and carbothermal reduction in sequence to obtain a silicon carbide-boron nitride three-dimensional thermally conductive framework material.

[0035] In step S1, the self-assembly between SiO2 nanoparticles and sheet-like BNNS is achieved by ammonia-catalyzed hydrolysis. The sheet-like BNNS has good thermal conductivity and good orientation during subsequent freeze-drying, which is beneficial for the directional transport of thermal conductivity. The SiO2 nanoparticles can provide a silicon source for the subsequent carbothermal reduction reaction to grow SiC nanowires.

[0036] In one embodiment, the ratio of the lateral dimension to the thickness of the BNNS is 400:1 to 5000:1.

[0037] To further improve the thermal conductivity of the SiC-BNNS three-dimensional thermally conductive framework material, the average lateral dimension of the BNNS is 2μm to 5μm, and the average thickness is 1nm to 5nm.

[0038] In one embodiment, during the preparation of the precursor, the concentration of BNNS in the dispersion is 0.05 g / mL to 0.2 g / mL.

[0039] In one embodiment, the mass ratio of the BNNS to the organosilicon source is 1:1 to 1:4 to achieve good loading efficiency of SiO2 nanoparticles on the BNNS surface.

[0040] To promote the hydrolysis of organosilicon sources to generate SiO2 nanoparticles, it is preferable to use ammonia to adjust the pH of the dispersion to 6-8.

[0041] Specifically, the organosilicon source is selected from tetraethoxysilane, polycarbosilane, diethoxymethylsilane, etc.

[0042] It should be noted that the ammonia used in this invention can be liquid ammonia or ammonia water, or a certain amount of ammonia gas can be introduced into the dispersion.

[0043] In one embodiment, the solvent in the dispersion is selected from a water-alcohol solution, wherein the volume ratio of water to alcohol in the water-alcohol solution is 1:10 to 1:3, and the alcohol is preferably ethanol.

[0044] To ensure thorough mixing of the organosilicon source and BNNS and improve the loading effect of SiO2 nanoparticles, the system for preparing the precursor is subjected to ultrasonic dispersion or stirring.

[0045] In step S2, PAA can bond SiO2-BNNS together and provide a carbon source for the subsequent carbothermal reduction reaction to grow SiC nanowires. By controlling the direction of ice crystal growth during freezing through directional freeze-drying, a PAA-SiO2-BNNS composite aerogel with a directional structure is obtained.

[0046] It should be noted that the freeze-drying process of the present invention uses existing methods, and the present invention does not limit it. For example, the mixed solution can be poured into a Teflon mold with a copper rod at the bottom for freeze-drying.

[0047] In one embodiment, the porosity of the composite aerogel is 85% to 96%, which is beneficial for maintaining the flexibility of the thermal interface material.

[0048] In one embodiment, the density of the composite aerogel is 28 mg / cm³. 3 ~92mg / cm 3 This is beneficial for the composite of silicon carbide-boron nitride three-dimensional thermally conductive framework materials with polymer matrices when used as thermal interface materials.

[0049] In one embodiment, the mass ratio of PAA to SiO2-BNNS and trimethylamine is 1:(1-4):0.2.

[0050] Specifically, PAA and trimethylamine are first dissolved in a solvent, and then SiO2-BNNS is added and mixed. The mixing method is ultrasonic dispersion or stirring.

[0051] It should be noted that the solvents mentioned above are selected from water or water-ethanol mixtures.

[0052] In step S3, PAA is first thermally imidized to PI, and then PI is carbonized to effectively reduce the change in structural stiffness, thereby improving the uniformity of the connection between the prepared SiC nanowires and BNNS and ensuring the structural stability of SiC-BNNS. Finally, SiC nanowires are grown through a carbothermal reduction reaction. SiC nanowires have good thermal conductivity and electrical insulation, and can form strong covalent bonds with BNNS, connecting the discontinuous BNNS in the framework and forming a continuous thermally conductive network of microstructure welding. This reduces the heat dissipation of phonons between interfaces, improves the interface heat transfer efficiency, and realizes that the thermally conductive material has both high thermal conductivity and electrical insulation.

[0053] To improve the uniformity of the connection between SiC nanowires and BNNS, enhance the interfacial heat transfer efficiency of BNNS, and improve the structural stability of SiC-BNNS, the temperature of the thermal imidization treatment is preferably 300℃~350℃, and the time is preferably 0.5h~3h.

[0054] Preferably, the carbonization treatment is carried out at a temperature of 800℃ to 1200℃ for a time of 0.5h to 2h.

[0055] Preferably, the temperature of the carbothermic reduction reaction is 1400℃~1600℃ and the time is 0.5h~2h.

[0056] In one embodiment, the BN-SiC three-dimensional thermally conductive framework material obtained in step S3 is sintered at a temperature of 500°C to 600°C for 0.5 h to 1 h to remove residual carbon from the BN-SiC three-dimensional thermally conductive framework material.

[0057] This invention also provides a silicon carbide-boron nitride (BNNS) three-dimensional thermally conductive framework material prepared by the method described above. Its physical image is shown in Figure (1). Furthermore, the microstructure of the BNNS material is shown in Figure (2). It can be seen that the BNNS has a sheet-like structure, with SiC nanowires connecting the BNNS to form a continuous thermally conductive network of microstructure welding. The connections between the BNNS are relatively uniform. The SiC-BNNS three-dimensional thermally conductive framework material of this invention possesses excellent thermal conductivity and electrical insulation properties, and has broad application prospects.

[0058] In one embodiment, the mass fraction of SiC in the SiC-BNNS is less than 10%.

[0059] The present invention also provides a thermal interface material, comprising a polymer matrix and a silicon carbide-boron nitride three-dimensional thermally conductive framework material as described above distributed in the polymer matrix.

[0060] It should be noted that the composite method between the polymer matrix and the silicon carbide-boron nitride three-dimensional thermally conductive framework material in the thermal interface material of the present invention adopts the prior art, and the present invention will not elaborate on this.

[0061] In one embodiment, the polymer matrix is ​​selected from at least one of polydimethylsiloxane, rubber, and polyurethane. The polymer matrix has good flexibility, and the silicon carbide-boron nitride three-dimensional thermally conductive framework material has excellent thermal conductivity and electrical insulation. Thus, the thermal interface material has high thermal conductivity, electrical insulation, and flexibility, making it particularly suitable for the field of flexible electronics. It can ensure that the heating element and the heat dissipation element are closely attached during bending, and has broad application prospects.

[0062] It should be noted that the silicon carbide-boron nitride three-dimensional thermally conductive framework material of the present invention can also be composited with other polymer matrices and has excellent thermal conductivity and electrical insulation when used as a thermal interface material.

[0063] In one embodiment, the mass fraction of the silicon carbide-boron nitride three-dimensional thermally conductive framework material is 5 wt% to 25 wt%.

[0064] Specifically, the thermal conductivity of the thermal interface material is 2.1 W / mK to 8.6 W / mK.

[0065] The following specific embodiments will further illustrate the silicon carbide-boron nitride three-dimensional thermally conductive framework material, its preparation method, and its applications.

[0066] Application Example 1

[0067] S1. 0.5 g of BNNS with an average lateral dimension of 2 μm and a thickness of 3 nm was added to 10 mL of water-ethanol solution (water:ethanol = 1:10) and ultrasonically dispersed for 120 min to obtain a uniform dispersion. 5 mL of ammonia was added to adjust the pH of the dispersion to 7. Then, 0.5 g of tetraethoxysilane (the mass ratio of BNNS to tetraethoxysilane was 1:1) was added. After reacting for 30 min, the mixture was filtered, rinsed with deionized water, and dried to obtain SiO2-BNNS.

[0068] S2. Dissolve 0.5g of PAA and 0.1g of trimethylamine in 10mL of deionized water, then add 0.5g of SiO2-BNNS. After ultrasonic dispersion for 30min, pour the mixed solution into a Teflon mold with a copper rod at the bottom, and freeze-dry it in a freeze-drying oven where the copper rod is submerged in liquid nitrogen. This yields PAA-SiO2-BNNS aerogel with a porosity of 91% and a density of 38mg / cm³. 3 .

[0069] S3. The PAA-SiO2-BNNS aerogel was subjected to thermal imidization at 300℃ for 2 hours to generate PI, resulting in PI-SiO2-BNNS aerogel. The PI-SiO2-BNNS aerogel was then carbonized at 800℃ for 2 hours to obtain C-SiO2-BNNS aerogel. Finally, the C-SiO2-BNNS aerogel was subjected to carbothermal reduction at 1500℃ for 3 hours to grow SiC nanowires from SiO2 and C, resulting in a SiC-BNNS three-dimensional thermally conductive framework material. Residual carbon was removed by sintering at 600℃. The SiC mass fraction in the SiC-BNNS three-dimensional thermally conductive framework material was 9 wt%.

[0070] S4. 0.8g of SiC-BNNS three-dimensional thermally conductive framework material was impregnated in 10g of polydimethylsiloxane (PDMS), and then heat-treated in an oven at 100℃ for 2h to obtain the thermal interface material.

[0071] Application Example 2

[0072] S1. 0.5 g of BNNS with an average lateral dimension of 5 μm and a thickness of 2 nm was added to 10 mL of water-ethanol solution (water:ethanol = 1:10) and ultrasonically dispersed for 120 min to obtain a uniform dispersion. 5 mL of ammonia was added to adjust the pH of the dispersion to 7.5. Then, 0.8 g of tetraethoxysilane (the mass ratio of BNNS to tetraethoxysilane was 1:1.6) was added. After reacting for 30 min, the mixture was filtered, rinsed with deionized water, and dried to obtain SiO2-BNNS.

[0073] S2. Dissolve 0.8 g of PAA and 0.1 g of trimethylamine in 10 mL of deionized water, then add 0.5 g of SiO2-BNNS. After ultrasonic dispersion for 30 min, pour the mixed solution into a Teflon mold with a copper rod at the bottom, and freeze-dry it in a freeze-drying oven where the copper rod is submerged in liquid nitrogen. This yields PAA-SiO2-BNNS aerogel with a porosity of 87% and a density of 44 mg / cm³. 3 .

[0074] S3. The PAA-SiO2-BNNS aerogel was subjected to thermal imidization treatment at 350℃ for 1 h to generate PI, resulting in PI-SiO2-BNNS aerogel. The PI-SiO2-BNNS aerogel was then carbonized at 800℃ for 2 h to obtain C-SiO2-BNNS aerogel. Finally, the C-SiO2-BNNS aerogel was subjected to carbothermal reduction reaction at 1500℃ for 3 h to grow SiC nanowires from SiO2 and C, resulting in a SiC-BNNS three-dimensional thermally conductive framework material. Residual carbon was removed by sintering at 600℃. The mass fraction of SiC in the SiC-BNNS three-dimensional thermally conductive framework material was 11 wt%.

[0075] S4. 1g of SiC-BNNS three-dimensional thermally conductive framework material is immersed in 10g of rubber precursor solution for composite processing, and then heat-treated at 80℃ for 2h to obtain thermal interface material.

[0076] Application Example 3

[0077] S1. 1g of BNNS with an average lateral dimension of 5.1μm and a thickness of 0.9nm was added to 10mL of water-ethanol solution (water:ethanol = 1:10) and ultrasonically dispersed for 120min to obtain a uniform dispersion. 5mL of ammonia was added to adjust the pH of the dispersion to 7. Then, 1g of polycarbosilane (the mass ratio of BNNS to polycarbosilane was 1:2) was added. After reacting for 30min, the mixture was filtered, rinsed with deionized water and dried to obtain SiO2-BNNS.

[0078] S2. Dissolve 0.5g of PAA and 1g of trimethylamine in 10mL of deionized water, then add 1g of SiO2-BNNS. After ultrasonic dispersion for 30min, pour the mixed solution into a Teflon mold with a copper rod at the bottom, and freeze-dry it in a freeze-drying oven where the copper rod is submerged in liquid nitrogen. This yields PAA-SiO2-BNNS aerogel with a porosity of 83% and a density of 48mg / cm³. 3 .

[0079] S3. The PAA-SiO2-BNNS aerogel was subjected to thermal imidization treatment at 300℃ for 2 hours to generate PI, thus obtaining PI-SiO2-BNNS aerogel. Then, the PI-SiO2-BNNS aerogel was subjected to carbonization treatment at 1000℃ for 2 hours to obtain C-SiO2-BNNS aerogel. Finally, the C-SiO2-BNNS aerogel was subjected to carbothermal reduction reaction at 1500℃ for 3 hours to grow SiC nanowires from SiO2 and C, thus obtaining a SiC-BNNS three-dimensional thermally conductive framework material. The residual carbon was removed by sintering at 600℃. The mass fraction of SiC in the SiC-BNNS three-dimensional thermally conductive framework material was 5 wt%.

[0080] S4. Soak 1g of SiC-BNNS three-dimensional thermally conductive framework material in 10g of PDMS, and then heat treat it at 100℃ for 2h to obtain the thermal interface material.

[0081] Application Example 4

[0082] S1. 1.5g of BNNS with an average transverse dimension of 2μm and a thickness of 5nm was added to 10mL of water-ethanol solution (water:ethanol = 1:2) and ultrasonically dispersed for 120min to obtain a uniform dispersion. 5mL of ammonia was added to adjust the pH of the dispersion to 6, and then 3g of tetraethoxysilane (the mass ratio of BNNS to tetraethoxysilane was 1:2) was added. After reacting for 60min, the mixture was filtered, rinsed with deionized water and dried to obtain SiO2-BNNS.

[0083] S2. Dissolve 0.5g of PAA and 0.1g of trimethylamine in 10mL of deionized water, then add 1.5g of SiO2-BNNS. After ultrasonic dispersion for 60min, pour the mixed solution into a Teflon mold with a copper rod at the bottom, and freeze-dry it in a freeze-drying oven where the copper rod is submerged in liquid nitrogen. This yields PAA-SiO2-BNNS aerogel with a porosity of 81% and a density of 54mg / cm³. 3 .

[0084] S3. The PAA-SiO2-BNNS aerogel was subjected to thermal imidization at 300℃ for 2 hours to generate PI, resulting in PI-SiO2-BNNS aerogel. The PI-SiO2-BNNS aerogel was then carbonized at 800℃ for 2 hours to obtain C-SiO2-BNNS aerogel. Finally, the C-SiO2-BNNS aerogel was subjected to carbothermal reduction at 1600℃ for 2 hours to grow SiC nanowires from SiO2 and C, resulting in a SiC-BNNS three-dimensional thermally conductive framework material. Residual carbon was removed by sintering at 600℃. The SiC mass fraction in the SiC-BNNS three-dimensional thermally conductive framework material was 8 wt%.

[0085] S4. Soak 2g of SiC-BNNS three-dimensional thermally conductive framework material in 10g of PDMS, and then heat treat at 100℃ for 2h to obtain thermal interface material.

[0086] Application Example 5

[0087] S1. 1.5g of BNNS with an average lateral dimension of 5μm and a thickness of 1nm was added to 10mL of water-ethanol solution (water:ethanol = 1:10) and ultrasonically dispersed for 150min to obtain a uniform dispersion. 1mL of ammonia was added to adjust the pH of the dispersion to 8, and then 4.5g of tetraethoxysilane (the mass ratio of BNNS to tetraethoxysilane was 1:3) was added. After reacting for 60min, the mixture was filtered, rinsed with deionized water and dried to obtain SiO2-BNNS.

[0088] S2. Dissolve 0.5g of PAA and 0.1g of trimethylamine in 20mL of deionized water, then add 2g of SiO2-BNNS. After ultrasonic dispersion for 60min, pour the mixed solution into a Teflon mold with a copper rod at the bottom, and freeze-dry it in a freeze-drying oven where the copper rod is submerged in liquid nitrogen. This yields PAA-SiO2-BNNS aerogel with a porosity of 77% and a density of 64mg / cm³. 3 .

[0089] S3. The PAA-SiO2-BNNS aerogel was subjected to thermal imidization treatment at 300℃ for 3 hours to generate PI, resulting in PI-SiO2-BNNS aerogel. The PI-SiO2-BNNS aerogel was then carbonized at 800℃ for 2 hours to obtain C-SiO2-BNNS aerogel. Finally, the C-SiO2-BNNS aerogel was subjected to carbothermal reduction reaction at 1500℃ for 3 hours to grow SiC nanowires from SiO2 and C, resulting in a SiC-BNNS three-dimensional thermally conductive framework material. Residual carbon was removed by sintering at 600℃. The mass fraction of SiC in the SiC-BNNS three-dimensional thermally conductive framework material was 10 wt%.

[0090] S4. Immerse 3g of SiC-BNNS three-dimensional thermally conductive framework material in 10g of PDMS, and then heat treat at 120℃ for 2h to obtain thermal interface material.

[0091] Application Comparative Example 1

[0092] The difference between Comparative Example 1 and Application Example 1 is that in step S1, irregularly shaped boron nitride nanoparticles with a particle size of 200 nm are used.

[0093] Application Comparative Example 2

[0094] The difference between Comparative Example 2 and Application Example 1 is that in step S3, the PAA-SiO2-BNNS aerogel is heated at 800℃ for 4 hours to directly carbonize PAA, and then heated at 1500℃ for 3 hours to grow SiC nanowires through carbothermic reduction reaction of SiO2 and C, thus obtaining SiC-BNNS three-dimensional thermally conductive framework material.

[0095] Application Comparative Example 3

[0096] The difference between Comparative Example 3 and Application Example 1 is that in step S3, the PAA-SiO2-BNNS aerogel is first sintered at 200°C for 2 hours to directly and partially crosslink PAA to obtain the corresponding aerogel; then carbonization is performed at 800°C for 2 hours; finally, a carbothermic reduction reaction is performed at 1500°C for 3 hours, and the resulting product is a porous three-dimensional structure. Since PAA is partially crosslinked, the product is a mixture.

[0097] Application Comparative Example 4

[0098] The difference between Comparative Example 4 and Application Example 1 is that in step S3, the PAA-SiO2-BNNS aerogel is subjected to thermal imidization treatment at 300°C for 2 hours to obtain PI-SiO2-BNNS aerogel; then the PI-SiO2-BNNS aerogel is sintered at 600°C for 1 hour, and due to the low temperature, a low degree of carbonization aerogel is obtained; finally, a carbothermic reduction reaction is carried out at 1500°C for 3 hours, and the product obtained is a carbon / silicon carbide composite structure.

[0099] The thermal interface materials prepared in all application examples and comparative examples were subjected to performance tests. The test indicators and test methods are as follows:

[0100] (1) Thermal conductivity: The thermal conductivity of the thermal interface material is measured by a laser thermal conductivity meter;

[0101] (2) Electrical conductivity: The electrical conductivity of the thermal interface material is measured by a resistance meter;

[0102] The performance test results for all application examples and application comparisons are shown in Table 1.

[0103] Table 1

[0104] Thermal conductivity (W / mK) electrical conductivity Application Example 1 5.1 insulation Application Example 2 7.4 insulation Application Example 3 8.9 insulation Application Example 4 8.3 insulation Application Example 5 9.4 insulation Application Comparative Example 1 3.2 insulation Application Comparative Example 2 4.8 insulation Application Comparative Example 3 4.4 Conductive Application Comparative Example 4 3.7 Conductive

[0105] As can be seen from the performance test results in Table 1, under the same test conditions, all application examples of the present invention have higher thermal conductivity (≥5.1 W / mK) compared to the comparative examples, and also have good electrical insulation. Therefore, the silicon carbide-boron nitride three-dimensional thermally conductive framework material prepared by the present invention has excellent thermal conductivity and electrical insulation. At the same time, the thermal interface material prepared by combining it with the polymer matrix has excellent thermal conductivity, electrical insulation and flexibility, and is especially suitable for the field of flexible electronics, with broad application prospects.

[0106] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0107] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a silicon carbide-boron nitride three-dimensional thermally conductive framework material, characterized in that, Includes the following steps: Boron nitride nanosheets were prepared into a dispersion and the pH of the dispersion was adjusted with ammonia. Then, an organosilicon source was added to react and a precursor was obtained. The precursor included boron nitride nanosheets and SiO2 nanoparticles loaded on the surface of the boron nitride nanosheets. The precursor, polyamic acid, and trimethylamine were mixed in a solvent and then freeze-dried to obtain a composite aerogel. The composite aerogel was subjected to thermal imidization, carbonization and carbothermal reduction in sequence to obtain a silicon carbide-boron nitride three-dimensional thermally conductive framework material.

2. The method for preparing the silicon carbide-boron nitride three-dimensional thermally conductive framework material according to claim 1, characterized in that, The ratio of the transverse dimension to the thickness of the boron nitride nanosheets is 400:1 to 5000:

1.

3. The method for preparing the silicon carbide-boron nitride three-dimensional thermally conductive framework material according to claim 2, characterized in that, The boron nitride nanosheets have an average lateral dimension of 2 μm to 5 μm and an average thickness of 1 nm to 5 nm.

4. The method for preparing the silicon carbide-boron nitride three-dimensional thermally conductive framework material according to claim 1, characterized in that, The preparation process of the precursor satisfies at least one of the following conditions: (1) The concentration of boron nitride nanosheets in the dispersion is 0.05 g / mL to 0.2 g / mL; (2) The mass ratio of the boron nitride nanosheets to the organosilane is 1:1 to 1:4; (3) The pH of the dispersion is adjusted to 6-8 using ammonia; (4) The solvent in the dispersion is selected from a water-alcohol solution, wherein the volume ratio of water to alcohol in the water-alcohol solution is 1:10 to 1:

3.

5. The method for preparing the silicon carbide-boron nitride three-dimensional thermally conductive framework material according to claim 1, characterized in that, The mass ratio of the polyamic acid to the precursor and the trimethylamine is 1:(1-4):0.

2.

6. The method for preparing the silicon carbide-boron nitride three-dimensional thermally conductive framework material according to claim 1, characterized in that, The step of preparing the composite aerogel into a silicon carbide-boron nitride three-dimensional thermally conductive framework material satisfies at least one of the following conditions: (1) The temperature of the thermal imidization treatment is 300℃~350℃, and the time is 0.5h~3h; (2) The carbonization treatment is carried out at a temperature of 800℃ to 1200℃ for a time of 0.5h to 2h; (3) The temperature of the carbothermic reduction reaction is 1400℃~1600℃ and the time is 0.5h~2h.

7. A silicon carbide-boron nitride three-dimensional thermally conductive framework material prepared by the preparation method of the silicon carbide-boron nitride three-dimensional thermally conductive framework material according to any one of claims 1 to 6.

8. The silicon carbide-boron nitride three-dimensional thermally conductive framework material according to claim 7, characterized in that, In the silicon carbide-boron nitride three-dimensional thermally conductive framework material, the mass fraction of silicon carbide is less than 10%.

9. A thermal interface material, characterized in that, The thermal interface material includes: a polymer matrix and a silicon carbide-boron nitride three-dimensional thermally conductive framework material as described in claim 7 or 8, distributed in the polymer matrix.

10. The thermal interface material according to claim 9, characterized in that, In the thermal interface material, the mass fraction of the silicon carbide-boron nitride three-dimensional thermally conductive framework material is 5wt% to 25wt%.

Images