Thermally conductive composite material and preparation method and application thereof

Abstract

The application discloses a heat-conducting composite material and a preparation method and application thereof. The heat-conducting composite material comprises silicon carbide nanowires and spherical and / or spheroid-like diamond deposited on the silicon carbide nanowires. That is, the diamond is arranged on the silicon carbide nanowires in a spherical or spheroid-like form to form a sugar-cane structure. The composite material with the appearance does not agglomerate in a polymer and has good heat-conducting performance; and a composite thermal interface material formed by the composite material and a high-molecular polymer has a thermal conductivity easy to reach a percolation threshold.

Description

Technical Field

[0001] This application relates to a thermally conductive composite material, its preparation method, and its application, belonging to the field of composite materials. Background Technology

[0002] With the advent of fifth-generation (5G) mobile communication technology, improving the heat dissipation capacity of high-power 5G materials faces significant challenges. Developing novel thermal interface materials (TIMs) with excellent thermal conductivity is an effective way to solve the heat dissipation problem of 5G electronic devices. Polymer composites are widely used in TIM preparation due to their advantages such as light weight, low cost, and simple preparation. However, since high-molecular-weight polymers without any fillers typically have only about 0.1-0.5 W·m⁻², their thermal conductivity is limited. -1 ·K -1 The thermal conductivity of the polymer is far from meeting the heat dissipation requirements of TIM applications. Adding high thermal conductivity fillers to polymers is an effective way to improve the thermal conductivity of polymer composites.

[0003] Diamond is valued for its excellent electrical insulation properties and 2000 W·m. -1 ·K -1 The ultra-high thermal conductivity of diamond makes it a promising filler for preparing polymer composites. However, there are still some problems with using diamond as a filler in the preparation of polymer composites. First, diamond fillers tend to agglomerate in the polymer, leading to a decrease in thermal conductivity; second, there is a high interfacial thermal resistance between diamond and the polymer matrix; in addition, it is difficult for the thermal conductivity of polymer composites containing diamond fillers to reach their percolation threshold. Therefore, the development of a novel diamond thermally conductive filler has become increasingly important. Summary of the Invention

[0004] According to one aspect of this application, a thermally conductive composite material is provided, which is a novel diamond@silicon carbide nanowire with a candied hawthorn-like structure. Specifically, diamonds are arranged in a spherical or near-spherical shape on silicon carbide nanowires to form a candied hawthorn-like structure. This composite material does not agglomerate within the polymer and exhibits excellent thermal conductivity; furthermore, it contains a composite thermal interface material formed by this composite material and the polymer, whose thermal conductivity easily reaches its percolation threshold.

[0005] A thermally conductive composite material comprising silicon carbide nanowires and spherical and / or near-spherical diamond deposited on the silicon carbide nanowires.

[0006] Optionally, the morphology of the thermally conductive composite material is similar to that of a candied hawthorn. Specifically, spherical and / or near-spherical diamonds are arranged in a linear fashion (in a row) on silicon carbide nanowires to form a candied hawthorn-like shape.

[0007] Optionally, the silicon carbide nanowires include 3C-SiC type silicon carbide nanowires, 4H-SiC type silicon carbide nanowires, and 6H-SiC type silicon carbide nanowires.

[0008] Optionally, the length L of the silicon carbide nanowire is in the range of 10μm≤L≤150μm;

[0009] The diameter of the silicon carbide nanowire is d, and the value of d is in the range of 100nm≤d≤600nm.

[0010] Optionally, the diamond has a particle size distribution of 1.5–3.0 μm; the average particle size of the diamond is 2.0–2.5 μm.

[0011] Optionally, the length L of the silicon carbide nanowire is independently selected from any value or a range between 10 μm, 20 μm, 30 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 110 μm, 120 μm, 130 μm, 140 μm, and 150 μm.

[0012] Optionally, the diameter d of the silicon carbide nanowire is independently selected from any value or a range between 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, and 600nm.

[0013] Optionally, the diamond grain size distribution is independently selected from any value of 1.5μm, 1.7μm, 2.0μm, 2.2μm, 2.5μm, 2.7μm, 3.0μm or a range between any two.

[0014] Optionally, the average grain size of the diamond is independently selected from any value of 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm or a range between any two.

[0015] According to a second aspect of this application, a method for preparing the thermally conductive composite material described in any of the preceding claims is also provided, the method comprising: performing chemical vapor deposition of a carbon source on a substrate with attached silicon carbide nanowires to obtain the thermally conductive composite material.

[0016] Optionally, the carbon source is selected from at least one of C1-C5 alkanes, C1-C5 ketones, graphite, carbon fibers, and carbon nanotubes. In this application, the carbon source used for depositing diamond can be methane, graphite, or other carbon-containing substances.

[0017] Optionally, the carbon source is selected from at least one of methane, acetone, and graphite.

[0018] Specifically, for example, methane, graphite, etc.

[0019] Optionally, the preparation method includes:

[0020] S100, Obtain a dispersion containing silicon carbide nanowires;

[0021] S200: Transfer the dispersion onto a substrate, evaporate, and remove the solvent;

[0022] S300. The carbon source is deposited on the substrate obtained in step S200 by plasma chemical vapor deposition to obtain the thermally conductive composite material.

[0023] Optionally, the solvent for the dispersion in step S100 can be acetone, alcohol, or other easily evaporating solvents.

[0024] The concentration of silicon carbide nanowires in the dispersion was 0.1 g / ml–1 g / ml.

[0025] Optionally, the concentration of silicon carbide nanowires is independently selected from any value of 0.1 g / ml, 0.2 g / ml, 0.3 g / ml, 0.4 g / ml, 0.5 g / ml, 0.6 g / ml, 0.7 g / ml, 0.8 g / ml, 0.9 g / ml, 1.0 g / ml, or any range between both.

[0026] Optionally, the substrate can be a copper plate, a glass plate, or a silicon substrate, and its shape can be a cuboid, a cylinder, or other polyhedrons.

[0027] Optionally, the process conditions for plasma chemical vapor deposition include:

[0028] The carbon-hydrogen molar ratio in the deposition atmosphere is 2.5–10%;

[0029] The deposition temperature is 700–1100℃;

[0030] The deposition pressure was 1.8–8 kPa;

[0031] The deposition time is 1 to 6 hours.

[0032] In this application, the chemical vapor deposition process conditions are crucial, as only under suitable process conditions can a candied hawthorn-like morphology be formed.

[0033] Specifically, the upper limit of the carbon-hydrogen molar ratio in the deposition atmosphere is selected from 5%, 7.5%, and 10%; the lower limit of the carbon-hydrogen molar ratio in the deposition atmosphere is selected from 2.5%, 5%, and 7.5%.

[0034] The upper limit of the deposition temperature is selected from 900℃, 1000℃, and 1100℃; the lower limit of the deposition temperature is selected from 700℃, 900℃, and 1000℃.

[0035] The upper limit of deposition pressure is selected from 2.0 kPa, 5.3 kPa, 6 kPa, and 8 kPa; the lower limit of deposition pressure is selected from 1.8 kPa, 2.0 kPa, 5.3 kPa, 6 kPa, and 8 kPa.

[0036] The upper limit of the deposition time is selected from 2h, 3h, and 6h; the lower limit of the deposition time is selected from 1h, 2h, and 3h.

[0037] Optionally, the plasma chemical vapor deposition includes any one of hot filament plasma chemical vapor deposition, direct current plasma chemical vapor deposition, and microwave plasma chemical vapor deposition.

[0038] Optionally, when using hot-filament plasma chemical vapor deposition, the process conditions also include:

[0039] The heating element power is 4000-4500W;

[0040] The distance between the hot wire and the substrate surface is 3.5–6 mm.

[0041] Specifically, the process conditions best suited for hot-filament plasma chemical vapor deposition are: a carbon-hydrogen molar ratio of 8–10% in the deposition atmosphere; a deposition temperature of 900–1100℃; a deposition pressure of 1.8–2 kPa; and a deposition time of 1–3 h.

[0042] Optionally, when using DC plasma chemical vapor deposition, the process conditions also include:

[0043] Deposition voltage: 500~800V;

[0044] Deposition current: 2-6A.

[0045] Specifically, the process conditions best matched with DC plasma chemical vapor deposition are: a carbon-hydrogen molar ratio of 2-3% in the deposition atmosphere; a deposition temperature of 700-900℃; a deposition pressure of 5-6 kPa; and a deposition time of 5-6 h.

[0046] Optionally, when microwave plasma chemical vapor deposition is used, the process conditions also include:

[0047] The microwave power is 1200-1800W.

[0048] Specifically, the process conditions best suited for microwave plasma chemical vapor deposition are: a carbon-hydrogen molar ratio of 7–8% in the deposition atmosphere; a deposition temperature of 900–1100℃; a deposition pressure of 7–8 kPa; and a deposition time of 1–2 h.

[0049] According to a third aspect of this application, a thermally conductive filler is also provided, the thermally conductive filler comprising any one of the thermally conductive composite materials described in any of the preceding claims, and the thermally conductive composite materials obtained by any one of the preparation methods described in any of the preceding claims.

[0050] Specifically, this invention provides a method for preparing a novel diamond@silicon carbide nanowire composite material with a candied hawthorn-like structure. This composite material can be used as a thermally conductive filler and belongs to the field of thermally conductive composite materials. First, silicon carbide nanowires are dispersed on a substrate using a solvent. Then, the substrate is placed in the cavity of a chemical vapor deposition (CVD) device, where diamond is deposited under certain conditions, forming a candied hawthorn-like diamond@silicon carbide nanowire composite material, which can be used as a novel filler for manufacturing polymer composite materials.

[0051] Optionally, the thermally conductive filler is any one of the thermally conductive composite materials described in any of the above claims or the thermally conductive composite materials obtained by the preparation method described in any of the above claims.

[0052] According to a fourth aspect of this application, a thermal interface material is also provided, the thermal interface material comprising a polymer and the thermally conductive filler described above.

[0053] Optionally, the thermally conductive filler accounts for 0.01wt%-95wt% of the polymer.

[0054] Specifically, the ratio of polymer to thermally conductive filler is such that the thermally conductive filler accounts for 0.01 wt% to 95 wt% of the polymer.

[0055] Specifically, the polymer in the thermal interface material that forms with the thermally conductive filler in this application can be a polymer commonly used in the art, such as epoxy resin, polyvinylidene fluoride (PVDF), polydimethylsiloxane (PDMS), polyvinyl alcohol (PVA), etc.

[0056] According to the fifth aspect of this application, the application of the above-described thermally conductive filler and / or the above-described thermal interface material in the field of 5G mobile communication is also provided.

[0057] The beneficial effects that this application can produce include:

[0058] The thermally conductive composite material provided in this application is a novel diamond@silicon carbide nanowire with a candied hawthorn-like structure. Specifically, diamond is inserted into silicon carbide nanowires in a spherical or near-spherical shape to form a candied hawthorn-like structure. This composite material does not agglomerate within the polymer and exhibits excellent thermal conductivity; furthermore, it contains a composite thermal interface material formed by this composite material and the polymer, whose thermal conductivity easily reaches its percolation threshold. Attached Figure Description

[0059] Figure 1 Figure (a) shows the SEM images of the diamond@silicon carbide nanowire structure with a candied hawthorn-like shape prepared in Example 1 of this application. Figure (b) shows the SEM image at the 10 μm scale.

[0060] Figure 2 The particle size test results are for the diamond in the candied hawthorn-like diamond@silicon carbide nanowire structure prepared in Example 1 of this application.

[0061] Figure 3 This is the Raman spectrum of the diamond particles deposited in Example 1 of this application.

[0062] Figure 4 Figure (a) shows the SEM images of the diamond@silicon carbide nanowires prepared in Comparative Example 1. Figure (b) shows the SEM image at the 10 μm scale.

[0063] Figure 5 Figure (a) shows the SEM images of diamond@silicon carbide nanowires prepared in Comparative Example 2. Figure (b) shows the SEM image at the 10 μm scale.

[0064] Figure 6 The image shows the Raman spectrum of the deposited diamond particles in Comparative Example 3.

[0065] Figure 7 Figure 1 shows the morphology of the thermal interface material obtained by mixing diamond@silicon carbide nanowires as fillers and polymer PDMS in Example 1. Figure (a) is a SEM image at the 8μm scale, and Figure (b) is a SEM image at the 2μm scale.

[0066] Figure 8 The thermal conductivity test diagram is shown for the thermal interface material obtained by mixing diamond@silicon carbide nanowires as fillers and polymer PDMS in Example 1. Detailed Implementation

[0067] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0068] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0069] The following describes possible implementation methods:

[0070] This invention provides a method for preparing a novel diamond@silicon carbide nanowire filler with a candied hawthorn-like structure, belonging to the field of thermally conductive composite materials.

[0071] The technical solution of the present invention:

[0072] A method for preparing a novel diamond@silicon carbide nanowire thermally conductive composite filler with a candied hawthorn-like structure is disclosed. First, silicon carbide nanowire powder is dispersed in a solvent, spread evenly on a substrate, and the solvent is evaporated. Then, the substrate is placed in a chemical vapor deposition (CVD) apparatus to deposit diamond, thereby obtaining the diamond@silicon carbide nanowire composite material with a candied hawthorn-like structure. The steps are as follows:

[0073] 1) The types of silicon carbide nanowires can be 3C-SiC type, 4H-SiC type, and 6H-SiC type. The length of the silicon carbide nanowires used is 10-500 μm, and the diameter is 100-600 nm;

[0074] 2) The solvent used to disperse the silicon carbide nanowires can be acetone, alcohol, or other easily evaporating solvents;

[0075] 3) The substrate used is a copper plate, glass plate or silicon substrate, etc., and the shape can be a cuboid, cylinder or other polyhedron;

[0076] 4) The CVD equipment used can be hot filament chemical vapor deposition (HFCVD) equipment, direct current chemical vapor deposition (DCCVD) equipment, microwave chemical vapor deposition (MWCVD) equipment, and other chemical vapor deposition equipment;

[0077] 5) Disperse silicon carbide nanowires in a solvent at a certain ratio (the ratio is not fixed, as long as they can be dispersed evenly), and after ultrasonic dispersion for 5-20 minutes, pour the resulting solution evenly onto the surface of the selected substrate, and then evaporate the solvent.

[0078] 6) After the solvent has evaporated, the substrate with silicon carbide nanowires is placed in the CVD equipment. Then, plasma is formed by direct current, hot wire, microwave and other methods to achieve the conditions required for diamond deposition. The carbon source is decomposed by the energy of the plasma and deposited on the surface of silicon carbide nanowires to form the desired diamond@silicon carbide nanowire composite material with a candied hawthorn-like structure.

[0079] The carbon source used for diamond deposition can be methane, graphite, or other carbon-containing substances. The carbon-to-hydrogen concentration ratio in the cavity is 2.5%-10%, the internal pressure of the cavity is 1.8-8 kPa, the temperature maintained during deposition is 700-1100℃, and the deposition time is 1-6 hours.

[0080] In this embodiment, the silicon carbide nanowire powder was purchased from Changsha Saitai New Materials Co., Ltd., with a length of 50-150μm and a diameter of 100-600nm.

[0081] Example 1:

[0082] 0.05g of silicon carbide nanowire powder was poured into 10ml of acetone solution and sonicated for 5 minutes to form a suspension. The resulting suspension was then evenly poured onto a plate measuring 200×80×10mm. 3 After acetone evaporates, the copper plate coated with silicon carbide nanowires is placed into the HFCVD chamber. Methane is used as the carbon source. Under the following process parameters: carbon-to-hydrogen ratio of 10.0%, hot filament power of 4000W, distance from the hot filament to the copper plate surface of 5mm, deposition temperature of 900℃, chamber pressure of 1.8kPa, and deposition time of 3h, a diamond@silicon carbide nanowire filler with a candied hawthorn-like structure was successfully prepared.

[0083] Example 2:

[0084] 0.05 g of silicon carbide nanowire powder was poured into 15 ml of alcohol solution and sonicated for 20 min to form a suspension. The resulting suspension was then uniformly poured onto a silicon substrate with a diameter of 100 mm and a height of 2 mm. After the alcohol evaporated, the silicon substrate with silicon carbide nanowires was placed in a DCCVD chamber. Graphite was used as the carbon source. Under the following process parameters: carbon-to-hydrogen ratio of 2.5%, voltage of 600 V, current of 4 A, deposition temperature of 700 °C, chamber pressure of 5.3 kPa, and deposition time of 6 h, a diamond@silicon carbide nanowire filler with a candied hawthorn-like structure was successfully prepared.

[0085] Example 3:

[0086] 0.03 g of silicon carbide nanowire powder was poured into 12 ml of acetone solution and sonicated for 15 min to form a suspension. The resulting suspension was then evenly poured onto a 200 × 80 × 10 mm plate. 3 On a copper plate, after acetone evaporates, the copper plate with silicon carbide nanowires is placed into the MWCVD chamber. The carbon source is acetone. Under the process parameters of a carbon-to-hydrogen ratio of 7.5%, a power of 1500W, a deposition temperature of 1000℃, a chamber pressure of 8kPa, and a deposition time of 2h, diamond silicon carbide nanofillers with a candied hawthorn-like structure were successfully prepared.

[0087] Example 4:

[0088] 0.05 g of silicon carbide nanowire powder was poured into 10 ml of alcohol solution and sonicated for 20 min to form a suspension. The resulting suspension was then uniformly poured onto a glass substrate with a diameter of 50 mm and a height of 2 mm. After the alcohol evaporated, the glass substrate with silicon carbide nanowires was placed in an HFCVD chamber. Methane was used as the carbon source. Under the following process parameters: a carbon-to-hydrogen ratio of 10.0%, a hot filament power of 4400 W, a hot filament-to-copper plate surface distance of 5 mm, a deposition temperature of 1100 °C, a chamber pressure of 2.0 kPa, and a deposition time of 1 h, a diamond@silicon carbide nanowire filler with a candied hawthorn-like structure was successfully prepared.

[0089] Example 5 Morphological Characterization

[0090] The measurement equipment was a field emission scanning electron microscope (FE-SEM, S4800, Hitachi, Japan). The microstructure of the diamond@silicon carbide nanowires prepared in Examples 1-4 was observed under an accelerating voltage of 8 kV. In all cases, diamond particles were found to be regularly arranged in a row on the silicon carbide nanowires, forming a novel, unique, candied hawthorn-like structure.

[0091] Taking Example 1 as a typical example, such as Figure 1 As shown, the SEM images of the diamond@silicon carbide nanowire structure resembling a candied hawthorn prepared in Example 1 are shown in Figure (a), which is a SEM image at the 10 μm scale, and Figure (b), which is a SEM image at the 2 μm scale. It can be seen that the deposited diamond particles are neatly arranged in a row on the silicon carbide nanowires, forming a special novel structure resembling a candied hawthorn.

[0092] Example 6: Particle size characterization of diamond particles

[0093] The measurement equipment was a field emission scanning electron microscope (FE-SEM, S4800, Hitachi, Japan). The diamond particle size in the diamond@silicon carbide nanowires prepared in Examples 1 to 4 was measured. The diamond@silicon carbide nanowires with a candied hawthorn-like shape prepared in Example 1 were used as a typical example. Figure 2 The results show the particle size distribution of diamonds in the structure. The results indicate that the diamond particle size is distributed in the range of 1.5 to 3.0 μm, with an average value of 2.0 to 2.5 μm.

[0094] Example 7 Material Characterization

[0095] The measurement equipment was a Raman spectrometer (inVia-reflex, Renishaw, UK), and Raman spectroscopy analysis was performed on the diamond@silicon carbide nanowires prepared in Examples 1-4 under a laser with a wavelength of 532 nm. The characterization results showed that the obtained substances were all diamond particles.

[0096] Example 1 is a typical example. Figure 3 The Raman spectrum of this image, after Lorentz peak finding, shows peaks at 1140, 1332, 1482, and 1546 cm⁻¹. -1 There are four peaks, one of which is at 1332 cm. -1 The peaks are characteristic of diamond, confirming that the deposited particles are indeed diamond particles. They are located at 1140 and 1482 cm⁻¹. -1 The peak is caused by the grain boundaries of diamond, and its appearance is usually due to the presence of nanocrystalline diamond. It is located at 1546 cm⁻¹. -1 The peak is the G peak of carbon materials.

[0097] Comparative Example 1

[0098] 0.05 g of silicon carbide nanowire powder was poured into 10 ml of alcohol solution and sonicated for 20 min to form a suspension. The resulting suspension was then uniformly poured onto a glass substrate with a diameter of 50 mm and a height of 2 mm. After the alcohol evaporated, the glass substrate with silicon carbide nanowires was placed in an HFCVD chamber. Methane was used as the carbon source. Under the following process parameters: carbon-to-hydrogen ratio of 1%, filament power of 4000 W, distance from the filament to the copper plate surface of 5 mm, deposition temperature of 1000 °C, chamber pressure of 2.0 kPa, and deposition time of 2 h, a diamond@silicon carbide nanowire filler with a candied hawthorn-like structure could not be prepared.

[0099] Comparative Example 2

[0100] 0.03 g of silicon carbide nanowire powder was poured into 12 ml of acetone solution and sonicated for 15 min to form a suspension. The resulting suspension was then evenly poured onto a 200 × 80 × 10 mm plate. 3 On a copper plate, after acetone evaporates, the copper plate with silicon carbide nanowires is placed into the MWCVD chamber. The carbon source is acetone. Under the process parameters of a carbon-to-hydrogen ratio of 7.5%, a power of 900W, a deposition temperature of 650℃, a chamber pressure of 8kPa, and a deposition time of 3h, diamond silicon carbide nanofillers with a candied hawthorn-like structure could not be prepared.

[0101] Comparative Example 3

[0102] 0.1 g of silicon carbide nanowire powder was poured into 10 ml of alcohol solution and sonicated for 20 min to form a suspension. The resulting suspension was then uniformly poured onto a glass substrate with a diameter of 50 mm and a height of 2 mm. After the alcohol evaporated, the glass substrate with silicon carbide nanowires was placed in an HFCVD chamber. Methane was used as the carbon source. Under the following process parameters: carbon-to-hydrogen ratio of 15.0%, filament power of 4400 W, distance from the filament to the copper plate surface of 5 mm, deposition temperature of 1100 °C, chamber pressure of 2.0 kPa, and deposition time of 6 h, a diamond@silicon carbide nanowire filler with a candied hawthorn-like structure could not be prepared.

[0103] Morphological tests were performed on Comparative Example 1 above, and the test results are as follows: Figure 4 As shown, Figure (a) is the SEM image at a scale of 10 μm, and Figure (b) is the SEM image at a scale of 4 μm. Figure 4 It can be seen that no diamond is formed on the surface of the silicon carbide nanowires.

[0104] Morphological tests were performed on Comparative Example 2 above, and the test results are as follows: Figure 5 As shown, Figure (a) is the SEM image at a scale of 10 μm, and Figure (b) is the SEM image at a scale of 2 μm. Figure 5 It can be seen that the diamond particles generated on the surface of silicon carbide nanowires are too small to form a typical candied hawthorn structure.

[0105] Raman spectroscopy was performed on the deposited diamond particles in Comparative Example 3 above, and the test results are as follows: Figure 6 The display shows that, by Figure 6 It can be seen that what is formed on the surface of silicon carbide nanowires is not crystalline diamond, but a substance in which graphite, diamond, and amorphous carbon coexist.

[0106] Example 8: Preparation of thermal interface materials

[0107] The diamond@silicon carbide nanowire fillers from Examples 1-4 were mixed with the polymer PDMS in a mass ratio of 5%-80% to obtain thermal interface materials.

[0108] The morphology of the obtained thermal interface materials was tested, and the results showed that the diamond@silicon carbide nanowires did not agglomerate in the polymer.

[0109] Taking the thermal interface material formed by the filler in Example 1 as a typical example, the mass ratio of filler to polymer is 70%, and the test results are as follows. Figure 7 As shown, Figure (a) is a SEM image at the 8 μm scale and Figure (b) is a SEM image at the 2 μm scale. These figures show that the diamond@silicon carbide nanowire filler with a candied hawthorn-like structure is well dispersed in PDMS.

[0110] The thermal conductivity of the obtained thermal interface materials was tested separately (thermal conductivity λ is given by the formula λ=α×C). p ×ρ, where α is the thermal diffusivity, determined by a flash thermal conductivity meter (LFA467). According to measurements by NETZSCH (Germany), C p (where ρ is the specific heat capacity and ρ is the density). Test results show that the thermal conductivity of the obtained thermal interface material is 0.2–2 W / m³. -1 K -1 .

[0111] The thermal interface material formed by the filler in Example 1 is a typical example, such as Figure 8 As shown, its thermal conductivity is 0.57 W / m. -1 K -1 .

[0112] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A thermally conductive composite material, characterized by, The thermally conductive composite material includes silicon carbide nanowires and spherical and / or near-spherical diamonds deposited on the silicon carbide nanowires; the spherical and / or near-spherical diamonds are arranged on the silicon carbide nanowires to form a candied hawthorn-like shape. The length of the silicon carbide nanowire is L, and the value of L is in the range of 10μm≤L≤150μm; The diameter of the silicon carbide nanowire is d, and the value of d is in the range of 100 nm ≤ d ≤ 600 nm; The diamond has a particle size distribution of 1.5~3.0μm; The diamond has an average grain size of 2.0~2.5μm.

2. The thermally conductive composite material according to claim 1, characterized in that, The silicon carbide nanowires include 3C-SiC type silicon carbide nanowires, 4H-SiC type silicon carbide nanowires, or 6H-SiC type silicon carbide nanowires.

3. The method for preparing the thermally conductive composite material according to any one of claims 1 to 2, characterized in that, The preparation method includes: The thermally conductive composite material can be obtained by chemical vapor deposition of a carbon source on a substrate with attached silicon carbide nanowires.

4. The preparation method according to claim 3, characterized in that, The carbon source is selected from at least one of C1-C5 alkanes, C1-C5 ketones, graphite, carbon fibers, and carbon nanotubes.

5. The preparation method according to claim 3, characterized in that, The preparation method includes: S100, Obtain a dispersion containing silicon carbide nanowires; S200: Transfer the dispersion onto a substrate, evaporate, and remove the solvent; S300. The carbon source is deposited on the substrate obtained in step S200 by plasma chemical vapor deposition to obtain the thermally conductive composite material.

6. The preparation method according to claim 5, characterized in that, The process conditions for plasma chemical vapor deposition include: The carbon-hydrogen molar ratio in the deposition atmosphere is 2.5–10%; The deposition temperature is 700~1100℃; The deposition pressure was 1.8~8 kPa; The deposition time is 1~6 hours; The plasma chemical vapor deposition includes any one of hot-filament plasma chemical vapor deposition, direct current plasma chemical vapor deposition, and microwave plasma chemical vapor deposition.

7. The preparation method according to claim 6, characterized in that, When using hot-filament plasma chemical vapor deposition, the process conditions also include: The heating element power is 4000~4500W; The distance from the hot wire to the substrate surface is 3.5~6mm.

8. The preparation method according to claim 6, characterized in that, When using DC plasma chemical vapor deposition, the process conditions also include: Deposition voltage: 500~800V; Deposition current: 2~6A.

9. The preparation method according to claim 6, characterized in that, When using microwave plasma chemical vapor deposition, the process conditions also include: The microwave power is 1200~1800W.

10. A thermally conductive filler, characterized in that, The thermally conductive filler includes any one of the thermally conductive composite materials according to any one of claims 1 to 2, and any one of the thermally conductive composite materials obtained by the preparation method according to any one of claims 3 to 9.

11. A thermal interface material, characterized in that, The thermal interface material includes a polymer and the thermally conductive filler as described in claim 10.

12. The application of the thermally conductive filler of claim 10 and / or the thermal interface material of claim 11 in the field of 5G mobile communication.

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