A method for large-scale growth of graphene on non-metallic particle surfaces

Abstract

The present application relates to graphene material and its preparation technology, specifically to a method for growing graphene on the surface of non-metallic particles on a large scale, which is suitable for large-scale preparation of graphene-coated non-metallic powder material. The present application uses a two-step method to grow graphene uniformly on the surface of a large number of non-metallic particles: first, mix a large number of non-metallic particles with a carbon source, and form a bulk composite material of non-metallic particles and carbon through low-temperature carbonization; then, pass current to the above bulk composite material using electrodes to heat it to a higher temperature, convert the carbon into graphene, until graphene-coated non-metallic particles are obtained, which are separated from each other, and the high-temperature heating process stops spontaneously. The present application can grow a graphene layer on the surface of a large number of non-metallic particles, the method is easy to scale up, and has the characteristics of good uniformity of graphene coating and high particle separation degree; at the same time, by taking advantage of the large resistance of graphene-coated non-metallic particles which are separated from each other, the high-temperature heating process stops spontaneously.

Description

TECHNICAL FIELD

[0001] The present application relates to graphene material and its chemical vapor deposition (CVD) preparation technology, in particular to a method for growing graphene on the surface of non-metallic particles on a large scale, which is suitable for growing graphene on the surface of a large number of non-metallic particles on a large scale. BACKGROUND

[0002] Developing controllable preparation method of high-quality graphene is the basis for realizing its application. Among them, the CVD method has the outstanding advantages of simple and easy operation, high quality of obtained graphene, realization of large-area growth and preparation on various substrates. However, there are a series of problems in growing graphene on the surface of non-metallic particles by using typical CVD method. Mainly including low growth quality, uneven growth and difficult to scale up. In order to fundamentally solve these problems, it is necessary to develop a CVD method for growing high-quality graphene on the surface of non-metallic particles on a large scale. The difficulty lies in that the catalytic activity of the surface of non-metallic substrate is much lower than that of metal, which is difficult to effectively decompose the carbon source. Although the methods such as metal catalytic assistance, high-temperature growth or plasma enhancement can obtain high-quality graphene, there are still problems of uneven growth and poor controllability in the interior of particle accumulation body. Therefore, how to grow graphene on the surface of non-metallic particles on a large scale has important significance and will promote the application of graphene in the fields of energy, transportation and composite materials. SUMMARY

[0003] The purpose of the present application is to provide a method for growing graphene on the surface of non-metallic particles on a large scale, which can grow graphene uniformly on a large number of non-metallic particles.

[0004] The technical scheme of the present application is:

[0005] A method for growing graphene on the surface of non-metallic particles on a large scale, which grows graphene on the surface of non-metallic particles by using two-step process, the growth reaction process has the characteristics of self-limitation, realizes scale-up, and the specific process is as follows:

[0006] Firstly, a large number of non-metallic particles are mixed with carbon source to form a block composite material of non-metallic particles and carbon by low-temperature carbonization, in which the carbon material forms a conductive network connected to each other, and the non-metallic particles are separated by the carbon material;

[0007] Then, the block composite material is heated by high-temperature heating with electric current through electrodes to convert the carbon into graphene until the graphene-coated non-metallic particles are obtained, and the high-temperature heating process stops spontaneously.

[0008] The method for growing graphene on the surface of non-metallic particles on a large scale, the typical temperature of low-temperature carbonization is between 400-800℃, and the typical temperature of high-temperature heating is between 800-1500℃.

[0009] The atmosphere during the low-temperature carbonization and high-temperature heating process is a reducing, inert or weakly oxidizing atmosphere.

[0010] The power supply mode is constant-voltage direct current, direct current pulse or constant-voltage alternating current.

[0011] The non-metallic particles include, but are not limited to, silicon, silicon oxide, aluminum oxide, silicon nitride, boron nitride, silicon carbide, silicate or a composite material thereof, and the typical particle size range of the non-metallic particles is 4-400 mesh.

[0012] The carbon source used includes, but is not limited to, one or more than two of alkane, alkene, alkyne, alcohol, fat, ether, phenol, aldehyde, carboxylic acid, polymer of the above-mentioned substances and biomass materials.

[0013] The method for growing graphene on the surface of non-metallic particles adjusts the degree of high-temperature heating process by changing the pressure of the electrode pair on the composite block material, so as to obtain graphene from multiple layers to single layer.

[0014] The method for growing graphene on the surface of non-metallic particles realizes in-situ thinning of graphene by changing the intensity and interval of the pulse current, so as to obtain graphene from multiple layers to single layer.

[0015] During the high-temperature heating process, additional carbon source or catalyst is added to improve the growth quality of graphene, the additional carbon source is alkane, alkene or alcohol, and the catalyst is transition metal nickel, copper or platinum.

[0016] The design idea of the present application is:

[0017] The graphene is grown on the surface of non-metallic particles by adopting a two-step method, first, a composite block material in which non-metallic particles are distributed inside carbon material is formed by fully mixing and low-temperature carbonization, so as to realize uniform coating of the carbon material precursor on the non-metallic particles and form a conductive network connected to each other, and then, the composite block material is heated to a higher temperature by power supply, so as to convert the carbon material into graphene, and when graphene-coated non-metallic particles are formed, the high-temperature heating process is spontaneously stopped due to the excessive resistance of the conductive network. The atmosphere during the low-temperature carbonization and high-temperature heating process is a reducing, inert or weakly oxidizing atmosphere; in order to accelerate the conversion reaction or reduce the number of layers of graphene, a reducing or weakly oxidizing atmosphere is preferred.

[0018] The characteristics and beneficial effects of the present application are:

[0019] 1. This invention achieves the growth of a uniformly coated graphene layer on the surface of a large number of non-metallic particles by fully mixing non-metallic particles with a carbon source, carbonizing them, and then converting them into graphene. Moreover, the separation between particles is high, which avoids the problems of uneven growth and particle agglomeration on the surface and inside of a large number of particle stacks when using methods such as chemical vapor deposition. The method is easy to scale up and has the characteristics of good graphene coating uniformity and high particle separation.

[0020] 2. This invention utilizes the high resistance of the graphene-coated non-metallic particles that are separated from each other to achieve the effect of spontaneously stopping the high-temperature heating process when electricity is applied; at the same time, this process can be adjusted by changing the electrode pressure and the reaction atmosphere. Attached Figure Description

[0021] Figure 1 This is a diagram of the few-layer graphene-coated alumina powder obtained in Example 1.

[0022] Figure 2 This is a diagram of the multilayer graphene-coated silicon oxide powder obtained in Example 2.

[0023] Figure 3 This is a diagram of the single-layer graphene-coated alumina powder obtained in Example 3.

[0024] Figure 4 This is a diagram of the multilayer graphene-coated silicon oxide powder obtained in Example 4. Detailed Implementation

[0025] In its specific implementation, this invention employs a two-step method to uniformly grow graphene on the surface of a large number of non-metallic particles: First, a large number of non-metallic particles are mixed with a carbon source, and low-temperature carbonization is used to form a bulk composite material of non-metallic particles and carbon; then, electrodes are used to electrically heat the above bulk composite material to a higher temperature, converting the carbon into graphene, until mutually separated graphene-coated non-metallic particles are obtained, while the high-temperature heating process spontaneously stops. In this invention, "a large number of non-metallic particles" means that the amount of non-metallic particles used in a single step reaches the kilogram level or above.

[0026] The present invention will be further described in detail below through embodiments.

[0027] Example 1

[0028] This invention employs a horizontal reactor to grow graphene. Electrodes are connected to both ends of the horizontal reactor, communicating with the reactor's internal cavity. The non-metallic particles are alumina (100 mesh), weighing 10 kg. First, the alumina particles are mixed uniformly with a 4% polypropylene carbonate ether solution at a 1:1 volume ratio and thoroughly dried in an oven at 120°C. Then, the mixture is placed in the reactor and carbonized for 30 minutes at 800°C under a hydrogen atmosphere (500 sccm flow rate) to obtain a composite bulk material of particles and carbon. After cooling to room temperature, electrodes are connected, and hydrogen (500 sccm flow rate) is introduced. The mixture is then heated again with a direct current of 100 volts until the furnace temperature reaches 1500°C. After approximately 2 hours, the furnace temperature begins to decrease spontaneously. At this point, the power is stopped, and the mixture is allowed to cool to room temperature with the furnace, yielding alumina powder coated with a few layers (2-4 layers in this example) of graphene. See [link to relevant documentation]. Figure 1 .Depend on Figure 1 It can be seen that graphene forms a uniform coating layer on the surface of alumina powder.

[0029] Example 2

[0030] The difference from Example 1 is that silicon oxide particles (80 mesh) were used. When the composite bulk material of silicon oxide particles and carbon was reheated with an electric current at 80 volts and an argon atmosphere (flow rate 200 sccm), the furnace temperature was raised to 1100°C. After about one hour, the furnace temperature began to decrease spontaneously. At this point, the power was stopped, and the furnace was allowed to cool to room temperature, resulting in multi-layered (4-10 layers in this example) graphene-coated silicon oxide powder. See [link to example]. Figure 2 .Depend on Figure 2 It can be seen that graphene forms a uniform coating layer on the surface of silicon oxide powder.

[0031] Example 3

[0032] The difference from Example 1 is that when the composite block material of alumina particles and carbon is reheated by electric current, the composite block material is placed vertically between the two electrodes, and a weight is placed on the upper electrode to apply a pressure of 1 MPa to the composite block material. Electric heating is continued until the furnace temperature reaches 1300°C. After about 3 hours, the furnace temperature begins to decrease spontaneously. At this point, the power is stopped, and the material is allowed to cool to room temperature with the furnace, resulting in alumina powder coated with a single layer of graphene. (See...) Figure 3 .Depend on Figure 3 It can be seen that graphene forms a uniform coating layer on the surface of alumina powder.

[0033] Example 4

[0034] The difference from Example 2 is that when the composite bulk material of silicon oxide particles and carbon is reheated, an argon atmosphere (flow rate 500 sccm) is used. A copper tube (purity >99.9 wt%) is placed upstream of the composite bulk material. Heating is continued until the furnace temperature reaches 1100°C. The argon gas flow carries copper vapors to the composite bulk material, utilizing the catalytic effect of copper in the atmosphere to improve the growth quality of graphene. After approximately one hour, the furnace temperature begins to decrease spontaneously. At this point, the power is stopped, and the furnace is allowed to cool to room temperature, resulting in multilayered (4-10 layers in this example) graphene-coated silicon oxide powder. See [link to example]. Figure 4 .Depend on Figure 4 It can be seen that graphene forms a uniform coating layer on the surface of silicon oxide powder.

[0035] The results of the embodiments show that the two-step method of the present invention can grow graphene on a large scale on the surface of a large number of non-metallic particles. By fully mixing non-metallic particles with a carbon source, carbonizing them, and then converting them into graphene, a uniformly coated graphene layer can be grown on the surface of a large number of non-metallic particles. The method is easy to scale up and has high uniformity. At the same time, taking advantage of the high resistance of the non-metallic particles coated with mutually separated graphene, the high-temperature heating process can be spontaneously stopped. In addition, the number of graphene layers can be controlled by changing the electrode pressure and the reaction atmosphere.

Claims

1. A method for large-scale growth of graphene on the surface of non-metallic particles, characterized in that, Graphene is grown on the surface of non-metallic particles using a two-step process. The growth reaction is self-limiting, enabling large-scale scaling. The specific process is as follows: First, a large number of non-metallic particles are mixed with a carbon source, which is polypropylene carbonate. The mixture is then carbonized at low temperature to form a bulk composite material of non-metallic particles and carbon. The carbon material forms an interconnected conductive network, and the non-metallic particles are separated by carbon material. Then, the above bulk composite material is heated at high temperature by applying electricity through electrodes to convert carbon into graphene until non-metallic particles coated with graphene that are separated from each other are obtained, and the high-temperature heating process stops spontaneously. The typical temperature for low-temperature carbonization is between 400 and 800°C, while the typical temperature for high-temperature heating is between 800 and 1500°C. The atmosphere used in the low-temperature carbonization and high-temperature heating processes is a reducing, inert, or weakly oxidizing atmosphere.

2. The method for large-scale growth of graphene on the surface of non-metallic particles according to claim 1, characterized in that, The power supply method is constant voltage DC, DC pulse, or constant voltage AC.

3. The method for large-scale growth of graphene on the surface of non-metallic particles according to claim 1, characterized in that, Non-metallic particles include silicon, silicon oxide, aluminum oxide, silicon nitride, boron nitride, silicon carbide, silicates or their composites, and the typical particle size range of non-metallic particles is 4 to 400 mesh.

4. The method for large-scale growth of graphene on the surface of non-metallic particles according to claim 1 or 2, characterized in that, This method adjusts the degree of high-temperature heating by changing the pressure of the electrodes on the composite bulk material, thereby obtaining graphene from multilayer to single-layer.

5. The method for large-scale growth of graphene on the surface of non-metallic particles according to claim 1 or 2, characterized in that, This method achieves in-situ thinning of graphene by changing the intensity and interval of the pulse current, thereby obtaining graphene from multilayer to single layer.

6. The method for large-scale growth of graphene on the surface of non-metallic particles according to claim 1, characterized in that, During the high-temperature heating process, the addition of additional carbon sources or catalysts can improve the growth quality of graphene. Additional carbon sources refer to alkanes, alkenes, or alcohols, while catalysts refer to transition metals such as nickel, copper, or platinum.

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