Graphene thermally conductive composite material, preparation method thereof, and thermally conductive composition comprising the graphene thermally conductive composite material

Abstract

This invention provides a method for preparing a graphene thermally conductive composite material, comprising: a carrier particle treatment step, in which carrier particles are placed in a fluidized bed reactor and an inert gas with a specific flow rate is introduced to fluidize the carrier particles; and a graphene deposition step, in which a process gas composed of a carbon source gas and a reducing gas is introduced while a chemical vapor deposition reaction is carried out at an internal temperature of 550°C to 1350°C in the fluidized bed reactor, so that graphene is deposited on the surface of the carrier particles, and after a deposition time, a graphene thermally conductive composite material with a thermal conductivity of 70 W / mK or higher is obtained. This preparation method utilizes a fluidized bed reactor and uses an inorganic material as a carrier to form a graphene film on its surface, allowing graphene to conduct heat in a planar manner in the XYZ directions. This effectively increases the addition rate of the graphene thermally conductive composite material in polymer materials and improves the dispersion and orientation of conventional graphene.

Description

[Technical Field]

[0001] This invention relates to a thermally conductive composite material and a method for manufacturing the same, and more particularly to a graphene thermally conductive composite material, a method for preparing the same, and a thermally conductive composition comprising the graphene thermally conductive composite material. [Previous Technology]

[0002] As a quasi-two-dimensional crystalline material composed entirely of sp2 mixed carbon atoms, with a thickness of only one or a few atomic layers, graphene has attracted much attention as a novel carbon material since its discovery in 2004. Graphene possesses excellent properties such as high light transmittance, electrical conductivity, thermal conductivity, high specific surface area, high strength, and flexibility.

[0003] Among them, graphene has excellent thermal conductivity (thermal conductivity up to 5000W / mK), which is 12 times that of copper (398 W / mK), and has good flexibility and extensibility. Theoretically, it would be an ideal lightweight and efficient thermal management material. However, as is well known, for graphene to exhibit excellent thermal conductivity in polymer systems, it needs to have excellent dispersibility and orientation.

[0004] Based on the above characteristics, in the process of preparing graphene composite thermal conductive products, simply modifying graphene to obtain better dispersion performance cannot enable the prepared thermal conductive products to fully utilize the excellent planar thermal conductivity of graphene. Furthermore, directly adding graphene powder will rapidly increase viscosity, resulting in limited addition amount and affecting the performance of the product's thermal conductivity.

[0005] Therefore, in Chinese patent CN107353017A, graphene oxide is coated using an amino-modified alumina suspension and a graphene oxide dispersion. In CN107226476B, alumina particles and graphite spheres are placed in the same container, and graphite is transferred to the alumina surface by physical friction. However, the aforementioned two methods still cannot effectively improve the dispersibility and thermal conductivity of graphene composite materials in polymer systems. [Summary of the Invention]

[0006] In view of the above, the purpose of the present invention is to provide a novel graphene thermal conductivity composite material and its preparation method, which can effectively improve the addition rate of graphene thermal conductivity composite material in polymer materials and improve the dispersibility and orientation of conventional graphene.

[0007] The preparation method of the present invention utilizes a fluidized bed reactor, with inorganic materials as carriers, to form a graphene film on its surface, so that the graphene conducts heat in a planar manner in the XYZ directions.

[0008] That is, the present invention can provide a method for preparing a graphene thermally conductive composite material, comprising: a carrier particle treatment step, wherein the carrier particles are placed in a fluidized bed reactor and an inert gas with a specific flow rate is introduced to fluidize the carrier particles; a graphene deposition step, wherein a process gas composed of a carbon source gas and a reducing gas is introduced while a chemical vapor deposition reaction is performed at an internal temperature of 550°C to 1350°C in the fluidized bed reactor, so that graphene is deposited on the surface of the carrier particles, and after a deposition time, a graphene thermally conductive composite material with a thermal conductivity of 70 W / mK or higher is obtained; wherein the average particle size of the carrier particles is between 200 nm and 200 µm; the specific flow rate is between 0.5 L / min and 500 L / min; the volume ratio of the carbon source gas to the reducing gas is between 1:0.33 and 1:3; and the specific reaction time is between 1 minute and 300 minutes.

[0009] According to one embodiment of the present invention, the carrier particles are selected from at least one of alumina, silicon dioxide, magnesium oxide, magnesium hydroxide, aluminum hydroxide, aluminum nitride, boron nitride, and zinc oxide.

[0010] According to one embodiment of the present invention, the flow rate of the carbon source gas is between 0.01 L / min and 100 L / min.

[0011] According to one embodiment of the present invention, the carbon source gas is at least one selected from methane, ethane, ethylene, acetylene, methanol, and ethanol.

[0012] According to one embodiment of the present invention, the flow rate of the reducing gas is between 0.01 L / min and 100 L / min.

[0013] According to one embodiment of the present invention, the reducing gas is selected from at least one of hydrogen, ammonia, methane, hydrogen sulfide and carbon monoxide.

[0014] In addition, according to one embodiment of the present invention, in the graphene thermal conductivity composite material, the graphene deposition thickness H (nm) and deposition time t (min) conform to the following relationship (1): H=(t 2- 45t + 3188) / 10000 (1) In formula (1), t represents the time (min) of chemical vapor deposition reaction in the graphene deposition step; H represents the thickness (nm) of graphene deposited on the surface of the carrier particles.

[0015] In addition, according to one embodiment of the present invention, in the graphene thermal conductivity composite material, the relationship between the graphene deposition thickness H (nm) and the thermal conductivity k (W / mK) of the graphene thermal conductivity composite material is given by equation (2): k = 58.192H 0.1436 (2) In equation (2), k represents the thermal conductivity (W / mK) of the graphene thermal conductivity composite material; H represents the thickness (nm) of the graphene deposited on the surface of the carrier particles.

[0016] Furthermore, the present invention may also provide a thermally conductive composition comprising at least: 5.0 wt% to 15.0 wt% of epoxy resin, 30.0 wt% to 90.0 wt% of alumina, and 3.0 wt% to 60.0 wt% of the above-mentioned graphene thermally conductive composite material.

[0017] According to one embodiment of the present invention, the content of the graphene thermal conductive composite material in the thermally conductive composition is 3 wt% or more.

[0018] According to one embodiment of the present invention, the volume resistivity (Ω·cm) of the thermally conductive composition is 3.0*10 14.

Implementation Method

[0019] In the following, various applicable examples are listed and described in detail with reference to the accompanying drawings, etc., regarding the technical content of the present invention related to graphene thermally conductive composite materials, their preparation methods, and thermally conductive compositions comprising the graphene thermally conductive composite materials; however, the present invention is by no means limited to the listed embodiments, drawings or detailed descriptions.

[0020] Furthermore, those skilled in the art should understand that the listed embodiments and accompanying drawings are for reference and illustration only and are not intended to limit the present invention; any modifications or alterations that can be easily implemented based on these descriptions are also considered to be within the scope of the spirit and intent of the present invention, and of course, such creations are also included in the scope of the patent application of the present invention.

[0021] Furthermore, the directional terms mentioned in the following embodiments, such as "up," "down," "left," "right," "front," and "back," are only for reference to the directions shown in the accompanying illustrations. Therefore, the directional terms used are for illustrative purposes and not for limiting the present invention; moreover, in the following embodiments, the same or similar elements will be labeled with the same or similar element numbers.

[0022] First, the preparation method of the graphene thermally conductive composite material of the present invention will be described, the preparation method comprising the following steps S1 and S2:

[0023] Step S1: Place the carrier particles into a fluidized bed reactor and introduce an inert gas with a specific flow rate to fluidize the carrier particles.

[0024] Step S2: While the internal temperature of the fluidized bed reactor is 550℃~1350℃, a process gas composed of carbon source gas and reducing gas is introduced, and a chemical vapor deposition reaction is carried out to deposit graphene on the surface of the carrier particles. After a deposition time, a graphene thermal conductivity composite material with a thermal conductivity of 70W / mK or higher is obtained.

[0025] In step S1, the carrier microparticles are materials used to support graphene and help improve thermal conductivity. According to the technical concept of the present invention, the material of the carrier microparticles is not particularly limited. For example, it can be at least one selected from alumina, silicon dioxide, magnesium oxide, magnesium hydroxide, aluminum hydroxide, aluminum nitride, silicon, and zinc oxide; preferably, it is selected from at least one selected from alumina, silicon dioxide, magnesium oxide, magnesium hydroxide, aluminum nitride, and zinc oxide; more preferably, it is selected from at least one selected from alumina, silicon dioxide, magnesium oxide, aluminum nitride, and zinc oxide; most preferably, it is selected from at least one selected from alumina, silicon dioxide, and magnesium oxide. Furthermore, the average particle size of the carrier microparticles can be between 200 nm and 200 µm, preferably between 400 nm and 150 µm; more preferably between 600 nm and 100 µm; and most preferably between 800 nm and 50 µm.

[0026] Furthermore, the inert gas in step S1 can be nitrogen or argon, but is not limited to these; other inert gases with the same properties can be selected. The specific flow rate of the inert gas entering the fluidized bed reactor is between 0.5 L / min and 500 L / min, more preferably between 5 L / min and 100 L / min, and most preferably between 8 L / min and 30 L / min. The actual flow rate can vary depending on the physical properties of different carrier particles.

[0027] In step S2, the reaction temperature of the process is between 550°C and 1350°C, preferably between 700°C and 1200°C, and even more preferably between 900°C and 1100°C. Furthermore, the volume ratio of the carbon source gas to the reducing gas is between 1:0.33 and 1:3, preferably between 1:0.6 and 1:2.5; more preferably between 1:0.8 and 1:2; and most preferably between 1:1 and 1:1.5.

[0028] According to the inventive concept of the present invention, the flow rate of the carbon source gas is between 0.01 L / min and 100 L / min, preferably between 0.1 L / min and 40 L / min, and more preferably between 0.2 L / min and 25 L / min; the flow rate of the reducing gas is between 0.01 L / min and 100 L / min, preferably between 0.1 L / min and 40 L / min, and more preferably between 0.2 L / min and 25 L / min.

[0029] Furthermore, the carbon source gas is selected from at least one of methane, ethane, ethylene, acetylene, methanol, and ethanol, preferably from at least one of methane, ethane, ethylene, acetylene, and methanol, more preferably from at least one of methane, ethane, ethylene, and acetylene, and most preferably from at least one of methane, ethane, and acetylene; the reducing gas is selected from at least one of hydrogen, ammonia, methane, hydrogen sulfide, and carbon monoxide, preferably from at least one of hydrogen, ammonia, methane, and carbon monoxide, more preferably from at least one of hydrogen, ammonia, and methane, and most preferably from at least one of hydrogen and ammonia.

[0030] Furthermore, according to the inventive concept of the present invention, the specific reaction time in step S2 can be determined according to the type and flow rate of the carbon source gas, the type and flow rate of the reducing gas, and the reaction temperature. Generally, it is between 1 minute and 300 minutes, preferably between 10 minutes and 250 minutes, more preferably between 50 minutes and 200 minutes, and most preferably between 100 minutes and 150 minutes.

[0031] After graphene is deposited on the surface of the carrier particles, the carbon source gas and reducing gas can be stopped from entering the fluidized bed reactor, and an inert gas with a larger flow rate and volume can be introduced instead, so that the graphene thermal conductivity composite material can leave the reaction chamber of the fluidized bed reactor with the inert gas and enter the collection chamber, and the graphene thermal conductivity composite material of the present invention can be collected.

[0032] In one embodiment of the present invention, the graphene thermally conductive composite material can be further mixed and processed with a polymer to obtain a thermally conductive composition with high thermal conductivity; the polymer may be selected from at least one of polyimide resin, epoxy resin, polytetrafluoroethylene, BT resin, polyamine formaldehyde, polysiloxane and phenolic resin, and is not particularly limited herein.

[0033] Next, the present invention will be described with reference to specific embodiments. 《Comparative Example 1》

[0034] 1 kg of carrier particles (alumina, with an average particle size of 20,000 nm) were placed into the reaction chamber of a fluidized bed reactor (self-made equipment). Then, nitrogen gas was introduced into the reaction chamber at a flow rate of 18 liters / minute (L / min) to suspend or flow the carrier particles and thus fluidize them; while introducing nitrogen gas, the internal temperature of the reaction chamber was raised to 500°C at a heating rate of 15 (°C / min).

[0035] Next, after the internal temperature of the reaction chamber reaches 500°C, 0.3 L / min of carbon source gas (acetylene) and 0.3 L / min of reducing gas (ammonia) are introduced into the reaction chamber of the fluidized bed reactor to react, so that graphene is deposited on the surface of the carrier particles to obtain graphene thermal conductivity composite material C1. The reaction time is 20 minutes.

[0036] After the reaction is completed, the supply of acetylene and ammonia is stopped, and a large amount of nitrogen is introduced into the reaction chamber so that the graphene thermal conductivity composite material C1 leaves the reaction chamber with the flow of nitrogen and enters the collector connected to the fluidized bed reactor, and the obtained graphene thermal conductivity composite material C1 can be collected.

[0037] Next, the properties of the graphene thermal conductivity composite material C1 were analyzed, and the results are recorded in Table 1. (Comparative Example 2)

[0038] 1 kg of carrier particles (silicon dioxide, average particle size 45000 nm) were placed into the reaction chamber of a fluidized bed reactor (self-made equipment). Then, nitrogen gas was introduced into the reaction chamber at a flow rate of 15 liters / minute (L / min) to suspend or flow the carrier particles and thus fluidize them; while introducing nitrogen gas, the internal temperature of the reaction chamber was raised to 850°C at a heating rate of 15 (°C / min).

[0039] Next, after the internal temperature of the reaction chamber reaches 850°C, 0.5 liters / minute (L / min) of carbon source gas (acetylene) is introduced into the reaction chamber of the fluidized bed reactor to react, so that graphene is deposited on the surface of the carrier particles to obtain graphene thermal conductivity composite material C2. The reaction time is 60 minutes.

[0040] After the reaction is completed, the supply of acetylene is stopped, and a large amount of nitrogen gas is introduced into the reaction chamber so that the graphene thermal conductivity composite material C2 leaves the reaction chamber with the flow of nitrogen gas and enters the collector connected to the fluidized bed reactor, and the obtained graphene thermal conductivity composite material C2 can be collected.

[0041] Next, the properties of the graphene thermal conductivity composite material C2 were analyzed, and the results are recorded in Table 1. 《Example 1》

[0042] 1 kg of carrier particles (silicon dioxide, average particle size 45000 nm) were placed into the reaction chamber of a fluidized bed reactor (self-made equipment). Then, nitrogen gas was introduced into the reaction chamber at a flow rate of 7 liters / minute (L / min) to suspend or flow the carrier particles and thus fluidize them; while introducing nitrogen gas, the internal temperature of the reaction chamber was raised to 750°C at a heating rate of 15 (°C / min).

[0043] Next, after the internal temperature of the reaction chamber reaches 750°C, 0.3 liters / minute (L / min) of carbon source gas (methane) and 0.3 liters / minute (L / min) of reducing gas (hydrogen) are introduced into the reaction chamber of the fluidized bed reactor to react, so that graphene is deposited on the surface of the carrier particles to obtain graphene thermal conductivity composite material V1. The reaction time is 80 minutes.

[0044] After the reaction is completed, the supply of methane and hydrogen is stopped, and a large amount of nitrogen is introduced into the reaction chamber so that the graphene thermal conductivity composite material V1 leaves the reaction chamber with the flow of nitrogen and enters the collector connected to the fluidized bed reactor, and the obtained graphene thermal conductivity composite material V1 can be collected.

[0045] Next, the properties of the graphene thermal conductivity composite material V1 were analyzed, and the results are recorded in Table 1. 《Example 2》

[0046] 0.5 kg of carrier particles (silicon, with an average particle size of 200 nm) were placed into the reaction chamber of a fluidized bed reactor (self-made equipment). Then, nitrogen gas was introduced into the reaction chamber at a flow rate of 14 liters / minute (L / min) to suspend or flow the carrier particles and thus fluidize them; while introducing nitrogen gas, the internal temperature of the reaction chamber was raised to 850°C at a heating rate of 15 (°C / min).

[0047] Next, after the internal temperature of the reaction chamber reaches 850°C, 0.45 liters / minute (L / min) of carbon source gas (ethane) and 0.15 liters / minute (L / min) of reducing gas (ammonia) are introduced into the reaction chamber of the fluidized bed reactor to react, so that graphene is deposited on the surface of the carrier particles to obtain graphene thermal conductivity composite material V2. The reaction time is 100 minutes.

[0048] After the reaction is completed, the supply of ethane and ammonia is stopped, and a large amount of nitrogen is introduced into the reaction chamber so that the graphene thermal conductivity composite material V2 leaves the reaction chamber with the flow of nitrogen and enters the collector connected to the fluidized bed reactor, and the obtained graphene thermal conductivity composite material V2 can be collected.

[0049] Next, the properties of the graphene thermal conductivity composite material V2 were analyzed, and the results are recorded in Table 1. 《Example 3》

[0050] Three kilograms of carrier particles (magnesium oxide, with an average particle size of 17,000 nm) were placed into the reaction chamber of a fluidized bed reactor (self-made equipment). Then, nitrogen (inert gas) was introduced into the reaction chamber at a flow rate of 15 liters per minute (L / min) to suspend or flow the carrier particles and thus fluidize them; while introducing nitrogen (inert gas), the internal temperature of the reaction chamber was raised to 750°C at a heating rate of 15 (°C / min).

[0051] Next, after the internal temperature of the reaction chamber reaches 750°C, 0.4 liters / minute (L / min) of carbon source gas (acetylene) and 0.15 liters / minute (L / min) of reducing gas (ammonia) are introduced into the reaction chamber of the fluidized bed reactor to react, so that graphene is deposited on the surface of the carrier particles to obtain graphene thermal conductivity composite material V3. The reaction time is 30 minutes.

[0052] After the reaction is completed, the supply of acetylene and ammonia is stopped, and a large amount of nitrogen is introduced into the reaction chamber so that the graphene thermal conductivity composite material V3 leaves the reaction chamber with the flow of nitrogen and enters the collector connected to the fluidized bed reactor, and the obtained graphene thermal conductivity composite material V3 can be collected.

[0053] Next, the properties of the graphene thermal conductivity composite material V3 were analyzed, and the results are recorded in Table 1. 《Example 4》

[0054] 3 kg of carrier particles (alumina, with an average particle size of 20,000 nm) were placed into the reaction chamber of a fluidized bed reactor (self-made equipment). Then, nitrogen (inert gas) was introduced into the reaction chamber at a flow rate of 12 liters / minute (L / min) to suspend or flow the carrier particles and thus fluidize them; while introducing nitrogen (inert gas), the internal temperature of the reaction chamber was raised to 950°C at a heating rate of 15 (°C / min).

[0055] Next, after the internal temperature of the reaction chamber reaches 950°C, 0.4 liters / minute (L / min) of carbon source gas (acetylene) and 0.6 liters / minute (L / min) of reducing gas (ammonia) are introduced into the reaction chamber of the fluidized bed reactor to react, so that graphene is deposited on the surface of the carrier particles to obtain graphene thermal conductivity composite material V4. The reaction time is 120 minutes.

[0056] After the reaction is completed, the supply of acetylene and ammonia is stopped, and a large amount of nitrogen is introduced into the reaction chamber so that the graphene thermal conductivity composite material V4 leaves the reaction chamber with the flow of nitrogen and enters the collector connected to the fluidized bed reactor, and the obtained graphene thermal conductivity composite material V4 can be collected.

[0057] Next, the properties of the graphene thermal conductivity composite material V4 were analyzed, and the results are recorded in Table 1. 《Example 5》

[0058] 1 kg of carrier particles (zinc oxide, average particle size 25000 nm) were placed into the reaction chamber of a fluidized bed reactor (self-made equipment). Then, nitrogen (inert gas) was introduced into the reaction chamber at a flow rate of 21 liters / minute (L / min) to suspend or flow the carrier particles and thus fluidize them; while introducing nitrogen (inert gas), the internal temperature of the reaction chamber was raised to 950°C at a heating rate of 15 (°C / min).

[0059] Next, after the internal temperature of the reaction chamber reaches 950°C, 0.35 liters / minute (L / min) of carbon source gas (acetylene) and 0.5 liters / minute (L / min) of reducing gas (ammonia) are introduced into the reaction chamber of the fluidized bed reactor to react, so that graphene is deposited on the surface of the carrier particles to obtain graphene thermal conductivity composite material V5. The reaction time is 50 minutes.

[0060] After the reaction is completed, the supply of acetylene and ammonia is stopped, and a large amount of nitrogen is introduced into the reaction chamber so that the graphene thermal conductivity composite material V5 leaves the reaction chamber with the flow of nitrogen and enters the collector connected to the fluidized bed reactor, and the obtained graphene thermal conductivity composite material V5 can be collected.

[0061] Next, the properties of the graphene thermal conductivity composite material V5 were analyzed, and the results are recorded in Table 1.

[0062] The aforementioned characteristic analysis includes visual color change, surface resistance measurement of graphene thermal conductivity composite material by surface resistivity meter and measurement of thermal conductivity coefficient by transient planar heat source method.

[0063] Visual observation of color changes can provide a preliminary judgment on whether a thin film is attached to the powder surface. Due to the high transparency of graphene, when the number of graphene layers is less than two, its appearance is almost transparent. Then, its color turns black as the number of layers increases. Therefore, the color change of the powder surface can be used as a preliminary judgment basis.

[0064] Both graphene with multiple layers and amorphous carbon powder have a black appearance and cannot be identified by visual means alone. However, the thermal conductivity and electrical conductivity of graphene are similar, both of which are conducted by highly conjugated π electrons. Therefore, the surface resistance of the material can be measured by a surface resistance meter to determine whether the molecular bonding mode of the surface-layered film is SP2 hybrid.

[0065] The transient plane heat source method can directly measure powder samples according to ISO 22007-2.2, and then calculate the thermal conductivity of the powder through the equipment.

[0066] Table 1 Comparative Example 1 Comparative Example 2 Example 1 Example 2 Example 3 Example 4 Example 5 Carrier microparticles type Alumina Silicon dioxide Silicon dioxide Silicon magnesium oxide Alumina Zinc oxide Average particle size (nm) 20000 45000 45000 200 17000 20000 25000 weight 1 1 1 0.5 3 3 1 inert gases type Nitrogen Nitrogen Nitrogen Argon Nitrogen Nitrogen Nitrogen Flow rate (L / min) 18 15 7 14 15 12 twenty one Process temperature (°C) 500 850 750 850 750 950 950 Heating rate (°C / min) 15 15 15 15 15 15 15 carbon source gas type Acetylene methane methane Ethane Acetylene Acetylene Acetylene Flow rate (L / min) 0.3 0.5 0.3 0.45 0.4 0.4 0.35 reducing gas type ammonia - hydrogen ammonia ammonia ammonia ammonia Flow rate (L / min) 0.3 0 0.3 0.15 0.15 0.6 0.5 reaction time 20 60 80 100 30 120 50 Graphene thermal conductivity composite materials C1 C2 V1 V2 V3 V4 V5 Feature Analysis color White black Light gray Light gray Light gray Light gray Light gray Surface resistivity (Ω / £) 10 9 10 7 <10 3 <10 3 <10 3 <10 3 <10 3 Thermal conductivity (W / mK) 38 51 71 70 74 78 76 Deposition thickness (nm) 0 4.9 6.7 5.5 5.3 7.6 6.1

[0067] As shown in Figure 1, in Comparative Example 1, the process temperature was not within the range of 550°C to 1350°C. The carbon source gas (acetylene) and the reducing gas (ammonia) could not effectively undergo chemical vapor deposition. The product after the reaction was off-white in color, with a surface resistivity of 10 9 Ω / £ and a thermal conductivity similar to that of alumina.

[0068] In Comparative Example 2, only carbon source gas (methane) was used for the reaction, and no reducing gas was added in proportion. As a result, only amorphous carbon was deposited on the carrier particles, instead of graphene composed of carbon atoms SP2. The product after the reaction was black and the surface resistance was 10 7 Ω / £.

[0069] The graphene thermal conductive composite materials in Examples 1 to 5 are all light gray in appearance, with a surface resistivity of 10 3 Ω / £ and a thermal conductivity of over 70 W / mK.

[0070] As is well known, graphene materials have excellent thermal conductivity in a plane, but no obvious advantage in the vertical direction. The graphene thermal conductivity composite material prepared by the method of the present invention can achieve planar conduction along the surface of the carrier by attaching graphene to the surface of the carrier powder, and at the same time conduction in a straight direction by the three-dimensional shape of the carrier, so as to achieve planar thermal conduction in the XYZ directions.

[0071] Furthermore, in the obtained graphene thermal conductivity composite material, a graph is plotted with the deposition time t (min) as the X-axis and the deposition thickness H (nm) of the graphene as the Y-axis, and the relationship curve shown in Figure 5 can be obtained; further, through the results of quadratic regression analysis, the relationship between the deposition thickness H (nm) of the graphene and the deposition time t (min) can be obtained as formula (1): H=(t 2- 45t + 3188) / 10000 (1)

[0072] In formula (1), t represents the time (min) for chemical vapor deposition reaction to be carried out in the graphene deposition step; H represents the thickness (nm) of graphene deposited on the surface of the carrier particles.

[0073] Furthermore, in the obtained graphene thermal conductivity composite material, a graph is plotted with the graphene deposition thickness H (nm) as the X-axis and the thermal conductivity coefficient k (W / mK) of the graphene thermal conductivity composite material as the Y-axis. The relationship curve shown in Figure 6 can be obtained. Through further quadratic regression analysis, the relationship between the graphene deposition thickness H (nm) and the thermal conductivity coefficient k (W / mK) of the graphene thermal conductivity composite material can be obtained as formula (2): k=58.192H 0.1436(2)

[0074] In formula (2), k represents the thermal conductivity coefficient (W / mK) of the graphene thermally conductive composite material; H represents the thickness (nm) of the graphene deposited on the surface of the carrier microparticles. Comparative Examples 3 to 4 and Examples 6 to 9 are further provided below to illustrate the effect of the graphene thermally conductive composite material of the present invention on improving the thermal conductivity of polymer materials. 《Comparative Example 3》

[0075] Epoxy resin and alumina (average particle size of 20 μm) were mixed in the weight ratio shown in Table 2 to uniformly disperse the alumina in the epoxy resin, thereby obtaining an insulating and thermally conductive composition M1.

[0076] Next, the thermal conductivity of the insulating and thermally conductive composition M1 was analyzed according to ASTM E1530-19, and the results are recorded in Table 2. (Comparative Example 4)

[0077] Epoxy resin, alumina (average particle size of 20 μm), and graphene (average particle size of 10 nm) were mixed in the weight ratios shown in Table 2, so that the alumina and graphene were uniformly dispersed in the epoxy resin to obtain an insulating and thermally conductive composition M2.

[0078] Next, the thermal conductivity of the insulating and thermally conductive composition M2 was analyzed according to ASTM E1530-19, and the results are recorded in Table 2. (Examples 6 to 10)

[0079] Epoxy resin and the graphene thermal conductive composite material V4 obtained in Example 4 of the present invention are mixed in the weight ratio shown in Table 2 to uniformly disperse the graphene thermal conductive composite material V4 in the epoxy resin to obtain insulating and thermally conductive compositions T1 to T5.

[0080] Next, the volume resistance was tested according to ASTM D257, the standard for testing the DC resistance or conductivity of insulating materials, and an evaluation was performed using test method D4496. Furthermore, the thermal conductivity of the insulating and thermally conductive compositions T1 to T5 was analyzed according to ASTM E1530-19, and the results are recorded in Table 2. Table 2 Comparative Example 1 Comparative Example 2 Example 6 Example 7 Example 8 Example 9 Epoxy resin (w / w%) 10 15 10 10 10 10 Alumina (w / w%) 90 82 87 80 60 40 Graphene (w / w%) 0 3 0 0 0 0 Graphene thermal conductivity composite material V4 (w / w%) 0 0 3 10 30 50 Thermally conductive composition M1 M2 T1 T2 T3 T4 Volume resistance (Ω˙cm) 3.55*10 15 1.5*10 15 2.15*10 15 1.84*10 15 1.28*10 15 7.94*10 14 Viscosity (cP) 100,000 180,000 130,000 210,000 230,000 240,000 Thermal conductivity (W / mK) 3 3.9 5.3 5.45 5.75 7.05

[0081] As shown in Figures 2 to 4, taking the commercially available insulating and thermally conductive epoxy resin M1 as a reference, the total solid content is 90% (w / w%). Graphene thermally conductive composite material V4 is used to partially replace it. Since the target product is an insulating and thermally conductive epoxy resin, the volume resistivity needs to be controlled above 10 14 Ω·cm. Therefore, the maximum addition amount is limited to 50% (w / w%). This is the upper limit of the volume resistivity due to insulation requirements, and the upper limit of the total amount of non-graphene thermally conductive composite material V4 that can be added.

[0082] In Comparative Example 3, since the density of graphene powder is low (about 0.01), when graphene is directly added to 3% (w / w%), the viscosity increases sharply. If graphene powder is added further, the powder will not be able to enter the colloid and will be discharged. Therefore, only the total solids content of 85% is used for comparison.

[0083] In Table 2, Comparative Example 2 and Example 6 are both 3% graphene / graphene thermal conductivity composite materials V4, and their thermal conductivity is increased from 3.9 W / mK to 5.3 W / mK, an increase of about 35%. If Comparative Example 2 is compared with Example 9, the thermal conductivity can be increased by about 80%.

[0084] However, the above description is only a preferred embodiment of the present invention and should not be construed as limiting the scope of the present invention. All simple equivalent changes and modifications made in accordance with the scope of the patent application and the description of the invention shall still fall within the scope of the patent of the present invention. [Simplified Explanation of the Diagram]

[0085] Figure 1 is a comparison graph showing the thermal conductivity and surface resistivity obtained from Comparative Examples 1 and 2 and Examples 1 to 5. Figure 2 is a comparison graph showing the bulk resistivity obtained from Comparative Examples 1 and 2 and Examples 5 to 9. Figure 3 is a comparison graph showing the viscosity obtained from Comparative Examples 1 and 2 and Examples 6 to 9. Figure 4 is a comparison graph showing the thermal conductivity obtained from Comparative Examples 1 and 2 and Examples 6 to 9. Figure 5 is a graph showing the relationship between the thickness (nm) of graphene deposited on the surface of the carrier particles and the time (min) of the chemical vapor deposition reaction in the graphene deposition step. Figure 6 is a graph showing the relationship between the thickness (nm) of graphene deposited on the surface of the carrier particles and the thermal conductivity k (W / mK) of the graphene thermal conductivity composite material.

Claims

1. A method for preparing a graphene thermally conductive composite material, comprising: a carrier particle treatment step, wherein the carrier particles are placed in a fluidized bed reactor and an inert gas with a specific flow rate is introduced to fluidize the carrier particles; a graphene deposition step, wherein a process gas consisting of a carbon source gas and a reducing gas is introduced while a chemical vapor deposition reaction is performed at an internal temperature of 550°C to 1350°C in the fluidized bed reactor, so that graphene is deposited on the surface of the carrier particles, and a graphene thermally conductive composite material is obtained after a deposition time; wherein the average particle size of the carrier particles is between 200 nm and 200 µm; the specific flow rate is between 0.5 L / min and 500 L / min; the volume ratio of the carbon source gas to the reducing gas is between 1:0.33 and 1:3; the chemical vapor deposition reaction time is between 1 minute and 300 minutes; and the thermal conductivity of the graphene thermally conductive composite material is above 70 W / mK.

2. The method for preparing the graphene thermally conductive composite material as described in claim 1, wherein the carrier particles are selected from at least one of alumina, silicon dioxide, magnesium oxide, magnesium hydroxide, aluminum hydroxide, aluminum nitride, silicon, and zinc oxide.

3. The method for preparing the graphene thermally conductive composite material as described in claim 1, wherein the flow rate of the carbon source gas is between 0.01 L / min and 100 L / min.

4. The method for preparing the graphene thermally conductive composite material as described in claim 1, wherein the carbon source gas is selected from at least one of methane, ethane, ethylene, acetylene, methanol, and ethanol.

5. The method for preparing the graphene thermally conductive composite material as described in claim 1, wherein the flow rate of the reducing gas is between 0.01 L / min and 100 L / min.

6. The method for preparing the graphene thermally conductive composite material as described in claim 1, wherein the reducing gas is selected from at least one of hydrogen, ammonia, methane, hydrogen sulfide and carbon monoxide.

7. The method for preparing the graphene thermally conductive composite material as claimed in claim 1, wherein in the obtained graphene thermally conductive composite material, the graphene deposition thickness H (nm) and deposition time t (min) conform to the following relationship (1): H=(t2 - 45t + 3188) / 10000 (1) In equation (1), t represents the time (min) for carrying out the chemical vapor deposition reaction in the graphene deposition step; H represents the thickness (nm) of graphene deposited on the surface of the carrier particles.

8. The method for preparing the graphene thermally conductive composite material as described in claim 1, wherein the graphene deposition thickness H (nm) and the thermal conductivity k (W / mK) of the graphene thermally conductive composite material are related by equation (2): k = 58.192H0.1436 (2) In equation (2), k represents the thermal conductivity (W / mK) of the graphene thermally conductive composite material; H represents the thickness (nm) of the graphene deposited on the surface of the carrier microparticles.

9. A thermally conductive composition comprising at least: 5.0 wt% to 15.0 wt% epoxy resin; Alumina ranging from 30.0 wt% to 90.0 wt%; And 3.0 wt% to 60.0 wt% of a graphene thermally conductive composite material, wherein the graphene thermally conductive composite material is prepared by the preparation method described in any one of claims 1 to 8.

10. The thermally conductive composition as claimed in claim 9, wherein the thermal conductivity of the thermally conductive composition is 5.0 W / mK or higher.

11. The thermally conductive composition as claimed in claim 9, wherein the volume resistivity (Ω·cm) of the thermally conductive composition is 3.0 × 10¹⁴ or more.

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