Graphene coated inorganic nonmetal powder composite material and preparation method thereof

Abstract

The invention discloses a method for preparing graphene coated inorganic nonmetal powder through chemical vapor deposition and a composite material prepared by the method. According to the method, graphene directly grows on the surface of inorganic non-metal powder through chemical vapor deposition to obtain the graphene-coated inorganic non-metal powder composite material, a metal catalyst and / or a non-metal catalyst are / is adopted in vapor deposition, the metal catalyst is fixed in a low-temperature area of a reactor for chemical vapor deposition, and the non-metal catalyst is fixed in a low-temperature area of the reactor for chemical vapor deposition. The temperature of the low-temperature region is lower than the melting point of the metal catalyst. According to the method, the catalyst (including the non-metal catalyst and / or the metal catalyst) is introduced into vapor deposition, high-quality graphene can be grown on the surface of the non-metal powder under the catalytic action of the catalyst, amorphous carbon and other impurity phases in the composite material are reduced, meanwhile, the use amount of hydrogen can be reduced, and the production safety can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of powder surface treatment, and particularly relates to a method for preparing graphene-coated inorganic non-metallic powders by chemical vapor deposition and a composite material prepared by this method. Background Art

[0002] Graphene has excellent electrical and thermal conductivity. When used for surface modification of inorganic non-metallic powders, it endows them with special surface properties, which can effectively broaden the application scenarios of inorganic non-metallic powders. At present, for the preparation methods of graphene-coated inorganic non-metallic powders, mainly including mechanical mixing method, solution mixing method, in-situ growth method, etc. Among them, growing graphene on the surface of inorganic non-metallic powders by chemical vapor deposition can achieve the tight combination of graphene and powders, and the prepared graphene-coated inorganic non-metallic powders have excellent thermal conductivity and mechanical properties. However, the catalytic cracking activities of common inorganic non-metallic powders are all poor, unable to effectively catalyze the cracking of carbon sources on the powder surface, and amorphous carbon and other impurity phases are easily generated during the cracking process. Therefore, in order to ensure the efficient growth and deposition quality of the graphene layer, a relatively high hydrogen flow rate needs to be introduced during the chemical vapor deposition process. Hydrogen is a high-risk gas and is extremely prone to explosion, which severely limits the industrialized and batch preparation of graphene-coated inorganic non-metallic powders by chemical vapor deposition. Summary of the Invention

[0003] To solve the above problems, the present invention provides a method for preparing graphene-coated inorganic non-metallic powders by chemical vapor deposition and a composite material prepared by this method.

[0004] The present invention provides a method for preparing graphene-coated inorganic non-metallic powders by chemical vapor deposition. Graphene-coated inorganic non-metallic powder composites are obtained by directly growing graphene on the surface of inorganic non-metallic powders through chemical vapor deposition. The vapor deposition uses a metal catalyst and / or a non-metal catalyst. The metal catalyst is fixed in the low-temperature region of the reactor for the chemical vapor deposition, and the temperature of the low-temperature region is lower than the melting point of the metal catalyst.

[0005] According to an embodiment of the present invention, the inorganic non-metallic powder is one or more of silicon powder, alumina powder, ceramic powder, boron nitride powder, aluminum nitride powder, magnesium oxide powder, silicon carbide powder, and silicon nitride powder.

[0006] According to another embodiment of the present invention, the metal catalyst is one or more of platinum, palladium, rhodium, copper, iron, nickel, and cobalt.

[0007] According to another embodiment of the present invention, the metal catalyst is a foil or foam.

[0008] According to another embodiment of the present invention, the non-metallic catalyst is mixed with the inorganic non-metallic powder.

[0009] According to another embodiment of the present invention, the non-metallic catalyst is a porous γ-alumina, magnesia, or zirconia powder.

[0010] According to another embodiment of the present invention, the particle size of the inorganic non-metallic powder is 1 nm to 100 μm; the particle size of the non-metallic catalyst is ≥40 μm, and the particle size of the non-metallic catalyst is greater than the particle size of the inorganic non-metallic powder.

[0011] According to another embodiment of the present invention, the chemical vapor deposition is carried out in a tubular furnace or a fluidized bed reactor.

[0012] According to another embodiment of the present invention, the fluidized bed reactor is a bubbling bed, a turbulent bed, or a fast fluidized bed.

[0013] According to another embodiment of the present invention, in the mixed gas of the carbon source precursor and hydrogen introduced for the chemical vapor deposition, the flow rate ratio of the carbon source precursor to hydrogen is 1:(1 - 30), and the temperature of the chemical vapor deposition is 600 - 1100 °C.

[0014] According to another embodiment of the present invention, the temperature of the low-temperature region is more than 10 °C lower than the melting point of the metal catalyst; preferably, the temperature of the low-temperature region is 400 °C to 1000 °C.

[0015] The present invention also provides a composite material prepared by the above method.

[0016] According to another embodiment of the present invention, in the composite material, the intensity ratio I D / I G of the D peak and the G peak in the Raman spectrum is between 0.45 and 0.7.

[0017] In the method of the present invention, a catalyst (including a non-metallic catalyst and / or a metal catalyst) is introduced in the chemical vapor deposition. By using the catalytic action of the catalyst, high-quality graphene can be grown on the surface of the non-metallic powder, reducing impurity phases such as amorphous carbon in the composite material. At the same time, the amount of hydrogen used can be reduced to improve production safety. In addition, the metal catalyst is fixed in the low-temperature region of the reactor for chemical vapor deposition. After the gaseous carbon source enters the reactor, it immediately contacts the metal catalyst, thereby rapidly cracking and reaching the non-metallic powder with the gas flow for deposition, effectively enhancing the reaction rate; the non-metallic catalyst is a porous powder with a high specific surface area. When mixed with the non-metallic powder, it can effectively promote the cracking and deposition of the carbon source on the surface of the non-metallic powder. Further, by setting its particle size to be larger than that of the non-metallic powder, the required product can be obtained by simple screening after the reaction is completed, and the process is simple and fast.

[0018] In the method of the present invention, graphene is in-situ grown on the surface of non-metallic powders, enhancing the interfacial bonding between graphene and inorganic non-metallic powders. Moreover, the in-situ grown graphene in the obtained composite material basically does not change the morphological structure of the matrix (inorganic non-metallic powders) itself, fully adapting to the subsequent use processes of traditional inorganic non-metallic powders. Additionally, as a coating shell, graphene can significantly improve the electrical and thermal conductivity of inorganic non-metallic powders. Furthermore, the raw materials used in the chemical vapor deposition method are gaseous, making it easy to control the reaction process and the composition of the products, reducing the generation of toxic and harmful substances, and being environmentally friendly. The preparation method of the present invention is simple, efficient, and low-cost, facilitating industrial production. Description of the Drawings

[0019] Figure 1 It is the field emission scanning electron microscope photograph of the composite material prepared in Example 1.

[0020] Figure 2 It is the Raman spectrum of the composite material prepared in Example 1.

[0021] Figure 3 It is the thermogravimetric curve of the composite material prepared in Example 1. Detailed Embodiments

[0022] The present invention will be described in detail below in conjunction with the specific embodiments.

[0023] In the method for preparing graphene-coated inorganic non-metallic powders by chemical vapor deposition of the present invention, graphene-coated inorganic non-metallic powder composites are obtained by directly growing graphene on the surface of inorganic non-metallic powders through chemical vapor deposition. The vapor deposition uses a metal catalyst and / or a non-metal catalyst, and the metal catalyst is fixed in the low-temperature region of the reactor for chemical vapor deposition. The temperature of the low-temperature region is lower than the melting point of the metal catalyst.

[0024] In an alternative embodiment, the temperature of the low-temperature region is 10 °C or more lower than the melting point temperature of the metal catalyst used. Specifically in the vapor deposition apparatus, the "low-temperature region" can be, for example, when the vapor deposition uses a tubular furnace, the low-temperature regions are the regions on both sides of the constant-temperature zone; when the vapor deposition uses a fluidized bed reactor, the low-temperature regions are the regions on both the upper and lower sides of the constant-temperature zone, and the temperature is about 400 - 1000 °C, specifically can be 400 °C, 450 °C, 500 °C, 550 °C, 600 °C, 700 °C, 800 °C, 900 °C, 1000 °C.

[0025] In the method of the present invention, using a catalyst in the vapor deposition can reduce the amount of hydrogen used and obtain high-quality graphene-coated materials. That is, this method can not only obtain composite materials with a low content of amorphous carbon impurities, but also reduce the amount of hydrogen used, improve the production safety, so that the production of composite materials can be industrialized and batch-produced.

[0026] When the method of the present invention uses a metal catalyst, the metal catalyst is placed in a low-temperature region to avoid the influence of the metal catalyst on the composite material and prevent the introduction of impurities into the composite material. In addition, the gas inlet of the gaseous carbon source in the tubular furnace or fluidized bed is located in the low-temperature region. After the carbon source enters from the inlet, it can come into contact with the metal catalyst fixed in the low-temperature region, thus being rapidly catalytically cracked and further reaching the non-metal powder with the gas flow for deposition, effectively improving the reaction rate.

[0027] The metal catalyst can be a noble metal catalyst such as platinum, palladium, rhodium, etc., or a transition metal catalyst such as copper, iron, nickel, cobalt, etc. The form of the metal catalyst can be foil or foam.

[0028] The non-metal catalyst can be selected from γ-aluminum oxide, magnesium oxide, zirconium oxide powder with a porous structure. Since the melting point of the non-metal catalyst is very high, the non-metal catalyst can be uniformly mixed with the matrix non-metal powder in the CVD reactor and will not deteriorate during the chemical vapor deposition process to introduce impurities into the composite material. At the same time, the porous structure endows the non-metal catalyst with a high specific surface area, which can adsorb and crack carbon species during the chemical vapor deposition process and nucleate and grow graphene on the surface of the matrix, realizing the growth and coating of graphene on the surface of the non-metal heat-conducting powder at a lower temperature, which can not only improve the growth quality of graphene but also reduce the reaction temperature and improve production efficiency.

[0029] In an alternative embodiment, the particle size of the non-metal catalyst is larger than that of the inorganic non-metal powder. After preparation, the target product can be obtained by simple screening. At the same time, adding the large-particle-size non-metal catalyst to the small-particle-size matrix non-metal powder can make the small-particle-size powder surround the large-particle-size powder, playing a role in dispersing the matrix inorganic non-metal powder and being more conducive to the coating of graphene on the matrix. Preferably, the particle size of the inorganic non-metal powder is 1 nm to 100 μm, the particle size of the non-metal catalyst is ≥40 μm, and the particle size of the non-metal catalyst is larger than that of the inorganic non-metal powder.

[0030] The dosage of the catalyst (including metal catalyst and / or non-metal catalyst) can be adjusted as needed, and the mass of the catalyst is 0.1% to 50% of the mass of the inorganic non-metal powder.

[0031] The inorganic non-metal powder as the matrix can be one or more of silicon powder, aluminum oxide powder, ceramic powder, boron nitride powder, aluminum nitride powder, magnesium oxide powder, silicon carbide powder, silicon nitride powder.

[0032] Chemical vapor deposition can be carried out in any suitable device, for example, in a tubular furnace or a fluidized bed reactor.

[0033] The carbon source for chemical vapor deposition can be selected from hydrocarbon substances such as methane, acetylene, ethylene, propylene, methanol or natural gas. The amount of carbon source introduced can be adjusted as needed. By adjusting the type and amount of carbon source introduced, the formation and coating of graphene can be controlled.

[0034] In the deposition stage, the reactor can be heated to a set temperature under a protective atmosphere of argon or nitrogen, and then the protective gas alone or a mixed gas of the protective gas and hydrogen is introduced, and the temperature is maintained for 5 min - 60 min, where the total gas flow rate is 0.01 - 50 L / min. Through the action of the catalyst, a graphene layer is formed on the surface of the non-metallic powder. By adjusting the reaction temperature and time, the thickness and uniformity of the graphene coating can be controlled.

[0035] Preferably, fluidized bed chemical vapor deposition (FBCVD) is used for chemical vapor deposition. Through the unique environment of the fluidized bed reactor, uniform coating of graphene on the surface of non-metallic powder can be achieved in large-scale production, and a non-metallic composite powder material with high thermal conductivity can be obtained. This method not only improves the thermal conductivity of the material, but also broadens the application range of graphene. In addition, the matrix non-metallic powder is micro-nano particles and is extremely easy to agglomerate. Under the blowing action of the gas flow in the fluidized bed, the large-particle non-metallic catalyst can play a role in crushing and dispersing, effectively dispersing the matrix non-metallic powder.

[0036] The fluidized bed reactor is a bubbling bed, a turbulent bed or a fast fluidized bed.

[0037] The method of the present invention can reduce the usage amount of hydrogen in the chemical vapor deposition process. Optionally, the flow rate ratio of the carbon source precursor to hydrogen in the mixed gas of the carbon source precursor and hydrogen introduced in the chemical vapor deposition is 1:(1 - 30), specifically, it can be 1:1, 1:3, 1:5, 1:10, 1:15, 1:20, 1:25, 1:30. At the same time, the method of the present invention can obtain a composite material containing high-quality graphene at a lower temperature. Optionally, the temperature of the chemical vapor deposition is 600 - 1100 °C, specifically, it can be 600 °C, 700 °C, 800 °C, 900 °C, 1000 °C, 1100 °C.

[0038] In the composite material obtained by the method of the present invention, the intensity ratio I D / I G of the D peak and the G peak in the Raman spectrum is between 0.55 and 0.7.

[0039] The present invention will be further described below through specific examples. However, these examples are merely exemplary and do not impose any limitation on the protection scope of the present invention. In the following examples and comparative examples, the reagents, materials, and instruments used can be obtained commercially without special instructions.

[0040] Example 1

[0041] 120 g of alumina powder with an average particle size of 40 μm was placed in a tubular furnace, and a copper foil was placed in the low-temperature region (about 550 °C) of the tubular furnace. Under an argon protection atmosphere, the reaction furnace cavity was slowly heated to 800 °C. According to the hydrogen-methane flow ratio of 10:1 and argon as the carrier gas, a mixed gas was introduced to start depositing graphene, and the deposition time for growing graphene was 15 minutes. After the growth was completed, the temperature was lowered to 450 °C under an argon and hydrogen protection atmosphere, and then to room temperature under an argon protection atmosphere. Then, the graphene / alumina powder was taken out.

[0042] The microscopic morphology of the prepared graphene / alumina powder composite is as Figure 1 shown. It can be seen from the field emission scanning electron microscope photos that graphene uniformly and tightly coats the surface of spherical alumina powder, maintaining the spherical morphology of spherical alumina. It can be proved that by using the above chemical vapor deposition method, a graphene / alumina powder composite with graphene uniformly and completely coating the surface of spherical alumina powder can be prepared.

[0043] Figure 2 is the Raman spectrum curve of the prepared graphene / alumina powder composite. It can be seen from the Raman spectrum that obvious graphene characteristic peaks are observed, and the presence of D peak, G peak, and 2D peak is observed. Among them, the ratio of I D to I G is 0.65, indicating that there are fewer defects inside the graphene layer and it has a high growth quality.

[0044] Figure 3 is the thermogravimetric curve of the prepared graphene / alumina powder composite heated to 1000 °C in an air atmosphere. It can be seen from the figure that the weight percentage of graphene in the composite is about 1%. At the same time, the weight loss temperature of the composite filler is higher than 650 °C, much higher than the weight loss temperature of general amorphous carbon in air, verifying the growth of high-quality graphene layers.

[0045] Example 2

[0046] Place 120 g of alumina powder with an average particle size of 40 μm in a tubular furnace. Place nickel foam in the low-temperature region (about 900 °C) of the tubular furnace. Slowly heat the reaction furnace cavity to 1100 °C under an argon protective atmosphere. According to the flow rate ratio of hydrogen to methane of 10:1 and using argon as the carrier gas, introduce the mixed gas to start depositing graphene, and the deposition time for growing graphene is 15 minutes. After growth is completed, cool down to 450 °C under an argon and hydrogen protective atmosphere, and then cool down to room temperature under an argon protective atmosphere, and then take out the graphene / alumina powder.

[0047] Example 3

[0048] Mix 120 g of alumina powder with an average particle size of 40 μm evenly with 6 g of porous γ-alumina powder with an average particle size of 150 μm, place it in a tubular furnace, and slowly heat the reaction furnace cavity to 1100 °C under an argon protective atmosphere. According to the flow rate ratio of hydrogen to methane of 10:1 and using argon as the carrier gas, introduce the mixed gas to start depositing graphene, and the deposition time for growing graphene is 15 minutes. After growth is completed, cool down to 450 °C under an argon and hydrogen protective atmosphere, and then cool down to room temperature under an argon protective atmosphere, and then take out the powder and screen it to obtain graphene / alumina powder.

[0049] Example 4

[0050] Perform chemical vapor deposition using a fluidized bed reactor. Fix the copper foil in the low-temperature region (about 550 °C) above the fluidized bed inlet. Place 120 g of alumina powder with an average particle size of 40 μm in the fluidized bed and slowly heat the reaction furnace cavity to 800 °C under an argon protective atmosphere. According to the flow rate ratio of hydrogen to acetylene of 20:1 and using argon as the carrier gas, introduce the mixed gas to start depositing graphene, and the deposition time is 5 minutes. After growth is completed, cool down to 450 °C under an argon and hydrogen protective atmosphere, and then cool down to room temperature under an argon protective atmosphere, and then take out the powder and screen it to obtain graphene / alumina powder.

[0051] Example 5

[0052] Perform chemical vapor deposition using a fluidized bed reactor. Fix the nickel foam in the low-temperature region (about 550 °C) above the fluidized bed inlet. Place 120 g of alumina powder with an average particle size of 40 μm in the fluidized bed and slowly heat the reaction furnace cavity to 800 °C under an argon protective atmosphere. According to the flow rate ratio of hydrogen to acetylene of 20:1 and using argon as the carrier gas, introduce the mixed gas to start depositing graphene, and the deposition time is 5 minutes. After growth is completed, cool down to 450 °C under an argon and hydrogen protective atmosphere, and then cool down to room temperature under an argon protective atmosphere, and then take out the powder and screen it to obtain graphene / alumina powder.

[0053] Example 6

[0054] Gas phase deposition was carried out using a fluidized bed reactor with γ-aluminum oxide as the catalyst. 120 g of alumina powder with an average particle size of 40 μm was mixed evenly with porous γ-aluminum oxide. 6 g of spherical γ-aluminum oxide powder with an average particle size of 150 μm was placed in the fluidized bed. The reaction furnace cavity was slowly heated to 1100 °C under an argon protection atmosphere. According to the flow ratio of hydrogen to acetylene of 20:1 and argon as the carrier gas, the mixed gas was introduced to start depositing graphene, and the deposition time was 10 minutes. After the growth was completed, the temperature was lowered to 450 °C under an argon and hydrogen protection atmosphere, and then to room temperature under an argon protection atmosphere, and the graphene / alumina powder was taken out.

[0055] Examples 7 - 10

[0056] In these 4 examples, gas phase deposition was carried out using a fluidized bed reactor. The substrate, catalyst, carbon source, flow ratio of hydrogen to carbon source, reaction temperature, and reaction time are shown in Table 1, and other reaction conditions are the same as those in Example 4. Graphene / alumina powder was prepared respectively.

[0057] Comparative Example 1

[0058] 120 g of alumina powder with an average particle size of 40 μm was placed in a tubular furnace. The reaction furnace cavity was slowly heated to 1200 °C under an argon protection atmosphere. According to the flow ratio of hydrogen to methane of 40:1 and argon as the carrier gas, the mixed gas was introduced to start depositing graphene, and the deposition time for growing graphene was 30 minutes. After the growth was completed, the temperature was lowered to 450 °C under an argon and hydrogen protection atmosphere, and then to room temperature under an argon protection atmosphere, and the graphene / alumina powder was taken out.

[0059] Since the scanning electron microscope photos, Raman spectra, and thermogravimetric curves of the graphene / thermal conductive powder composites prepared in Examples 2 - 10 are similar to those in Example 1, they will not be elaborated here.

[0060] Table 1 shows the preparation conditions and product parameters of Examples 1 - 10 and Comparative Example 1.

[0061] Table 1

[0062]

[0063] It can be seen from the data in the table that Examples 1 - 10 can still prepare composites with high-quality graphene even when the gas phase deposition temperature and the amount of hydrogen used are lower than those in Comparative Example 1.

[0064] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of this specification. These embodiments are selected and specifically described in this specification to better explain the principles and practical applications of the present invention, so that those skilled in the art can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A method for preparing graphene-coated inorganic non-metallic powder by chemical vapor deposition, characterized in that, A graphene-coated inorganic non-metallic powder composite material is obtained by directly growing graphene on the surface of inorganic non-metallic powder through chemical vapor deposition. The vapor deposition uses a metal catalyst and / or a non-metal catalyst. The metal catalyst is fixed in the low-temperature region of the reactor for the chemical vapor deposition, and the temperature of the low-temperature region is lower than the melting point of the metal catalyst.

2. The method according to claim 1, wherein The inorganic non-metallic powder is one or more of silicon powder, alumina powder, ceramic powder, boron nitride powder, aluminum nitride powder, magnesium oxide powder, silicon carbide powder, and silicon nitride powder.

3. The method according to claim 1, characterized in that, The metal catalyst is one or more of platinum, palladium, rhodium, copper, iron, nickel, and cobalt.

4. The method according to claim 3, wherein The metal catalyst is a foil or foam.

5. The method according to claim 1, characterized in that The non-metal catalyst is mixed with the inorganic non-metallic powder.

6. The method according to claim 1, wherein The non-metal catalyst is one or more of porous γ-alumina powder, magnesium oxide powder, and zirconia powder.

7. The method according to claim 5 or 6, characterized in that, The particle size of the inorganic non-metallic powder is 1 nm to 100 μm; the particle size of the non-metal catalyst is ≥40 μm, and the particle size of the non-metal catalyst is greater than the particle size of the inorganic non-metallic powder.

8. The method according to claim 1, wherein The vapor deposition is carried out in a tubular furnace or a fluidized bed reactor.

9. The method according to claim 8, characterized in that, The fluidized bed reactor is a bubbling bed, a turbulent bed, or a fast fluidized bed.

10. The method according to any one of claims 1-9, characterized in that, In the mixed gas of the carbon source precursor and hydrogen introduced in the vapor deposition, the flow ratio of the carbon source precursor to hydrogen is 1:(1 - 30), and the temperature of the vapor deposition is 600 - 1100 °C.

11. The method according to claim 1, wherein The temperature of the low-temperature region is more than 10 °C lower than the melting point of the metal catalyst; preferably, the temperature of the low-temperature region is 400 °C to 1000 °C.

12. A composite material, characterized in that, Prepared by the preparation method according to any one of claims 1 - 11.

13. The composite material according to claim 12, wherein, The intensity ratio I D / I G of the D peak and the G peak in the Raman spectrum of graphene in the composite material is between 0.45 and 0.7.

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