Preparation method of carbon nanotube-olefinic carbon composite material

Abstract

The invention provides a preparation method of a carbon nanotube-olefinic carbon composite material, which comprises the following steps: an olefinic carbon material, an additive and a catalyst are mixed and placed in reaction equipment, a carbon source is introduced for growth of a carbon nanotube, and the additive is carbon nitride or a reaction precursor for synthesis of carbon nitride; the growth procedure comprises a medium-temperature heating stage, a high-temperature heating stage and a high-temperature growth stage, and in the medium-temperature heating stage, the room temperature is heated to 500-600 DEG C; in the high-temperature heating stage, the temperature is increased to 750-900 DEG C from 500-600 DEG C; the temperature of the high-temperature growth stage is 750-900 DEG C, and the growth time is 10-50 minutes. The catalyst is a compound or a mixture containing free copper ions, and the carbon nanotubes can be prepared on an olefinic carbon material through catalytic growth by accurately controlling the dispersion uniformity of the copper ions. Copper with general catalytic capability on the growth of the carbon nanotubes theoretically is selected as a catalyst, and the high-yield and high-catalytic-capability growth of the actual carbon nanotubes is realized.

Description

Technical Field

[0001] The present invention relates to the technical fields of carbon nanotube material preparation, composite material preparation, and graphene defect repair, and particularly relates to a preparation method of a carbon nanotube-graphene-carbon composite material. Background Art

[0002] Graphene and carbon nanotubes are two highly representative members of the carbon family. Graphene is a single-layer hexagonal honeycomb quasi-two-dimensional carbon material in which carbon atoms are bonded in a sp2 hybridization manner, while carbon nanotubes can be regarded as one-dimensional nanomaterials with a hollow tubular structure formed by curling graphene in a certain direction. Both of them are widely used in the fields of energy, aerospace, thermal management, etc. due to their excellent physical, chemical, and mechanical properties. In addition, the vast carbon family also includes single materials such as graphite and carbon black, as well as composite materials composed of any two or more of them.

[0003] In the design of composite materials, the arbitrary combination of different dimensions of zero-dimensional, one-dimensional, and two-dimensional materials can be used as an effective strategy for constructing three-dimensional framework composite materials. The introduction and combination of different dimensional materials can effectively improve the agglomeration and re-packing problems of themselves and other phase materials. For example, 1) introducing zero-dimensional carbon black SP nanoparticles into two-dimensional graphene powder can effectively inhibit the agglomeration and re-stacking of graphene sheets by virtue of the "Blocking effect" of the nanoparticles; 2) introducing one-dimensional carbon nanotubes into graphene can also effectively improve the problems of easy agglomeration and stacking and difficult dispersion of graphene and carbon nanotubes themselves.

[0004] The traditional and commonly used method for composite materials is the physical mixing method, which relies on the mechanical stirring shear force to make the materials mix evenly. For example, in SCI literature such as "Porous graphene oxide / carbon nanotube hybrid films as interlayer for lithium-sulfur batteries", "Enhanced Electrical Networks of Stretchable Conductors with Small Fraction of Carbon Nanotube / Graphene Hybrid Fillers", "Graphene / carbon nanotube hybrid as a multi-functional interfacial reinforcement for carbon fiber-reinforced composites", and Chinese patent "CN116332168A, A preparation method and application of a graphene-carbon nanotube composite material", graphene and carbon nanotubes are only mixed by simple mechanical stirring. Not only is the mixing and dispersion effect limited, the material interface bonding problem is prominent, and the performance is restricted, but also different types of modifiers, dispersants, stabilizers, viscosity reducers, emulsifiers, etc. need to be introduced during the dispersion of graphene and carbon nanotubes. The introduction of these additives will inevitably have a significant negative effect on the subsequent actual application and performance. However, the direct in-situ growth by chemical vapor deposition (CVD) can avoid the above problems, and the obtained composite material has far better uniformity and performance than the traditional physical mixing method.

[0005] Benefiting from its high carbonophilic catalytic ability, the carbon solubility of typical Ni at 1000 °C is 1.3% atom. Alloys composed of iron, cobalt, nickel and any of the remaining metals with these three elements have become commonly used catalysts for the growth and preparation of carbon nanotubes. For example, SCI documents such as "Large Scale CVD Synthesis of Single-Walled Carbon Nanotubes", "Large-scale synthesis of single-wall carbon nanotubes by catalytic chemical vapor deposition CCVD method", "Roles of Metal-Support Interaction in Growth of Single- and Double-Walled Carbon Nanotubes Studied with Diameter-Controlled Iron Particles Supported on MgO", "The Use of Diatomite as a Catalyst Carrier for the Synthesis of Carbon Nanotubes" have achieved the growth of carbon nanotubes by loading catalysts such as iron and nickel on different carriers. However, due to their strong carbonophilic ability, it is difficult to completely remove the catalysts and the formed metal carbides after growth. In addition, the effective catalytic introduction of such catalysts inevitably introduces foreign impurities such as carriers, and a large number of processes are required for pickling, etching, fumigation and secondary treatment for purification in the later stage. Copper (Cu), due to its weak metal-carbon interaction and a carbon solubility of only 0.04% atom at 1000 °C, is considered a CNT growth catalyst with very weak catalytic ability.

[0006] Finally, in the Chinese patent "CN114068927A, Graphene-Carbon Nanotube Composite Material and Its Preparation Method", the growth and preparation of carbon nanotubes on graphene powder were successfully carried out using a fluidized bed device, but there are problems such as high growth temperature, low carbon nanotube growth density and yield, complex process, large amount of catalyst used, impurity residue, and the need for secondary treatment. Summary of the Invention

[0007] In view of the above-mentioned problems, the present invention innovatively introduces a carbon nitride-supported and dispersed copper catalyst into the preparation process of carbon nanotubes and graphene-carbon nanotube composite materials. The first aspect of the present invention provides a method for preparing a carbon nanotube-graphene composite material, and the specific scheme includes the following steps: Mix the carbonaceous material, additive, and catalyst, then place them into a reaction device. Introduce an inert gas, hydrogen, and a carbon source, and grow carbon nanotubes according to the growth procedure. The additive is carbon nitride or a reaction precursor for synthesizing carbon nitride. The growth procedure includes a medium-temperature heating stage, a high-temperature heating stage, and a high-temperature growth stage. The medium-temperature heating stage is to heat from room temperature to 500 - 600 °C; the high-temperature heating stage is to heat from 500 - 600 °C to 750 - 950 °C; the temperature in the high-temperature growth stage is 750 - 950 °C, and the growth time is 10 - 50 min.

[0008] Graphitic carbon nitride g-C3N4 can uniformly load and disperse metal catalysts, especially copper. At the same time, the nitrogen element introduced by g-C3N4 can not only effectively facilitate the anchoring of metal ions on the surface of inert graphene, but also, during the high-temperature growth process of carbon nanotubes, carbon nitride will decompose to produce nitrogen-containing active substances, which can effectively improve the catalytic activity of the catalyst, promote the diffusion and migration of carbon atoms, and inhibit the generation of amorphous carbon, thereby realizing the growth of carbon nanotubes and their graphene composites with high yield, high purity, no residual dispersion carrier, low catalyst residue, and no need for secondary pickling, fumigation, and etching treatment, and can achieve a certain degree of defect repair of the graphene substrate.

[0009] The reaction precursor for synthesizing carbon nitride can also achieve the above effect of uniformly loading and dispersing metal catalysts. Further, the reaction precursor for synthesizing carbon nitride is one or more of cyanamide, dicyandiamide, urea, thiourea, melamine, cyanuric acid, melamine, cyanuric amide, cyanuric diamide. The above reaction precursors can form supramolecular structure compounds with metals. The construction of supramolecules can uniformly disperse and anchor metal ions on the supramolecular framework, avoiding the agglomeration of ions and the formation of large ion clusters. The construction of supramolecular structure compounds can achieve primary dispersion and anchoring, and then in-situ thermal polycondensation into carbon nitride to achieve secondary dispersion and anchoring, with better catalyst dispersion and anchoring effect.

[0010] Control the temperature in the high-temperature growth stage at 750 - 900 °C. If the temperature is too low, the cracking efficiency of the carbon source and the catalytic activity will decrease, resulting in incomplete growth of carbon nanotubes on the carbonaceous material; if the temperature is too high, it will cause evaporation loss of the catalyst and almost no carbon nanotubes will be generated.

[0011] Further, in the high-temperature heating stage, the volume of hydrogen gas introduced accounts for 0.5% - 2.5% of the total volume of hydrogen gas and inert gas. In this stage, the amount of hydrogen gas should be neither too much nor too little. Excessive hydrogen gas will promote the agglomeration and growth of metal oxidants and cause etching damage to the graphene-carbon material. Too little hydrogen gas or no hydrogen gas added may lead to partial inactivation of the catalyst, resulting in messy growth of carbon nanotubes. Because the additive will decompose and release carbon- and nitrogen-containing fragments in this stage, the addition of an appropriate amount of hydrogen gas can ensure the etching and removal of the fragments attached to the catalyst surface without etching the graphene-carbon material itself.

[0012] Further, in the high-temperature growth stage, the volume of hydrogen gas introduced accounts for 4% - 20% of the total volume of hydrogen gas and inert gas. During the high-temperature growth process of carbon nanotubes, within a certain range, hydrogen gas plays a positive role in promoting the cracking of the carbon source and the formation of sp 2 carbon. However, when it exceeds the critical value, hydrogen gas will act as an etchant to etch the carbon nanotubes and the graphene-carbon material, playing a reverse role.

[0013] Further, when the additive is a reaction precursor for synthesizing carbon nitride, the growth program further includes a polycondensation stage. The temperature of the polycondensation stage is 500 - 600 °C, and the polycondensation time is 10 - 50 min. The setting of the polycondensation stage is for the synthesis of carbon nitride.

[0014] Further, the carbon source is one or more of gaseous olefins, gaseous alkynes, liquid alcohols, liquid ketones, and liquid benzenes; furthermore, the carbon source is one or more of ethylene, acetylene, methanol, ethanol, acetone, benzene, and toluene.

[0015] The applicant has found that, different from the traditional understanding, by precisely controlling the dispersion uniformity of copper ions, carbon nanotubes can be catalytically grown on the graphene-carbon material, and carbon nitride g-C3N4 can uniformly load and disperse copper.

[0016] Further, the catalyst is a compound or mixture containing free copper ions; furthermore, the catalyst includes one or more of copper chloride, copper sulfate, copper nitrate, copper acetate, and the metal organic complex copper acetylacetonate.

[0017] Further, the graphene-carbon material is a material with any morphology and shape combined in a sp 2 hybridization manner, such as graphene, flake graphite, expanded graphite, and worm graphite; or the graphene-carbon material is a material with any morphology and shape combined in a sp 3 hybridization manner, such as carbon black and Ketjen black.

[0018] Innovative points and beneficial effects: Innovatively introduce a carbon nitride-supported dispersed catalyst into the growth process of carbon nanotubes. Metal ions exist in the form of metal-N x -C bonding states within the carbon nitride framework, enabling the monodisperse anchoring of metal ions, avoiding premature agglomeration of the catalyst and the disordered formation of large-sized nanoparticles, which would otherwise lead to the loss of the catalytic activity of the catalyst. Heat the graphitic carbon nitride loaded with single-atom metal until the growth temperature of the carbon nanotubes. During the heating process, the structure of the carbon nitride begins to decompose, and the single-atom metal catalysts uniformly dispersed and anchored on the framework start to be released and polymerized in an orderly manner into nanoparticles of a certain uniform size, thus ensuring the formation of carbon nanotubes with a uniform tube diameter and morphology. Secondly, after high-temperature growth, the carbon nitride will completely decompose without leaving any impurities, with high purity, and there is no need for acid washing and etching to remove catalyst dispersion carriers such as silica, alumina, magnesia, and diatomaceous earth as in other methods. On the one hand, the nitrogen-containing active substances released during the decomposition process can inhibit the formation of amorphous carbon, ensuring the high-purity synthesis of carbon nanotubes. On the other hand, the nitrogen-containing substances can also promote the migration and diffusion of carbon atoms on the surface of the catalyst, maintaining the activity of the catalyst and achieving the high-yield synthesis of carbon nanotubes.

[0019] Using the polycondensation reaction of the reaction precursor for synthesizing carbon nitride to obtain carbon nitride can also achieve the effect of uniformly loading and dispersing the catalyst. Among them, the reaction precursor can form a supramolecular structure compound with the metal catalyst to achieve primary dispersion anchoring, and then in-situ thermally polycondense into carbon nitride to achieve secondary dispersion anchoring, with a better catalyst dispersion and anchoring effect.

[0020] Benefiting from the above supramolecular construction and anchoring dispersion, carbon nitride single-atom anchoring and dispersion, and the decomposition of carbon nitride to release nitrogen-containing substances to inhibit amorphous carbon, promote the diffusion and migration of carbon atoms, and maintain catalytic activity, the amount of catalyst used is extremely small, and there is no need for a cumbersome fumigation and etching process to remove the metal catalyst.

[0021] The applicant found that by precisely controlling the degree of uniform dispersion of copper ions, carbon nanotubes can be catalytically grown and prepared on the carbonaceous material. Copper, which is generally considered to have average catalytic ability for the growth of carbon nanotubes in theory, was selected as the catalyst and achieved the high-yield and high-catalytic-ability growth of actual carbon nanotubes. Selecting copper with an extremely low carbon solubility not only does not cause pore etching on the graphene sheets, but also, due to the high catalytic cracking ability of copper for olefins, alkanes, etc., the carbon active substances catalytically cracked and released can, on the one hand, be used for the growth of the carbon nanotubes themselves, and on the other hand, can effectively repair and reduce the structural defects introduced by the preparation method of the reduced graphene oxide (RGO) itself, killing two birds with one stone.

[0022] The growth process of carbon nanotubes is simple, and the parameters that need to be regulated are only the temperature and the flow rate of hydrogen. The regulation process is simple, and the growth of carbon nanotubes on the carbonaceous material can be achieved.

[0023] The synthesis process is simple and universal, with wide availability of raw materials, not limited to specific professional synthesis production equipment, and enabling large-scale industrial production. Description of the Drawings

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0025] Figure 1 SEM images of carbon nanotube-ene carbon composites prepared in Example 1 at different magnifications Figure 2 TGA characterization diagram of the carbon nanotube-ene carbon composite prepared in Example 1 Figure 3 TGA characterization diagram of the reduced graphene oxide raw material used in Example 1 Figure 4 TGA characterization diagram of TUBALL single-walled carbon nanotubes from OCSiAl Figure 5 Raman characterization result diagram of the carbon nanotube-reduced graphene oxide composite prepared in Example 1 Figure 6 SEM images of carbon nanotube-ene carbon composites prepared in Example 2 at different magnifications Figure 7 SEM images of carbon nanotube-ene carbon composites prepared in Example 3 at different magnifications Figure 8 SEM images of carbon nanotube-ene carbon composites prepared in Example 4 at different magnifications Figure 9 SEM images of carbon nanotube-ene carbon composites prepared in Example 5 at different magnifications Figure 10 SEM images of carbon nanotube-ene carbon composites prepared in Example 6 at different magnifications Figure 11 SEM images of carbon nanotube-ene carbon composites prepared in Example 7 at different magnifications Figure 12 SEM images of carbon nanotube-ene carbon composites prepared in Example 8 at different magnifications Figure 13 SEM images of carbon nanotube-ene carbon composites prepared in Example 9 at different magnifications Figure 14SEM images of the carbon nanotube-ene carbon composites prepared in Example 10 at different magnifications Figure 15 SEM images of the carbon nanotube-ene carbon composites prepared in Example 11 at different magnifications Figure 16 SEM images of the carbon nanotube-ene carbon composites prepared in Example 12 at different magnifications Figure 17 SEM images of the carbon nanotube-ene carbon composites prepared in Example 13 at different magnifications Figure 18 SEM images of the carbon nanotube-ene carbon composites prepared in Example 14 at different magnifications Figure 19 SEM images of the carbon nanotube-ene carbon composites prepared in Example 15 at different magnifications Figure 20 SEM images of the carbon nanotube-ene carbon composites prepared in Example 16 at different magnifications Figure 21 SEM images of the carbon nanotube-ene carbon composites prepared in Example 17 at different magnifications Figure 22 SEM images of the carbon nanotube-ene carbon composites prepared in Example 18 at different magnifications Figure 23 SEM images of the carbon nanotube-ene carbon composites prepared in Example 19 at different magnifications Figure 24 SEM images of the carbon nanotube-ene carbon composites prepared in Example 20 at different magnifications Figure 25 SEM images of the carbon nanotube-ene carbon composites prepared in Example 21 at different magnifications Figure 26 SEM images of the carbon nanotube-ene carbon composites prepared in Example 22 at different magnifications Figure 27 SEM images of the carbon nanotube-ene carbon composites prepared in Example 23 at different magnifications Figure 28 SEM images of the carbon nanotube-ene carbon composites prepared in Example 24 at different magnifications Figure 29 SEM images of the carbon nanotube-ene carbon composites prepared in Example 25 at different magnifications Figure 30 SEM images of the carbon nanotube-ene carbon composites prepared in Example 26 at different magnifications Figure 31SEM images of the carbon nanotube-ene carbon composites prepared in Example 27 at different magnifications Figure 32 SEM images of the carbon nanotube-ene carbon composites prepared in Example 28 at different magnifications Figure 33 SEM images of the carbon nanotube-ene carbon composites prepared in Example 29 at different magnifications Figure 34 SEM images of the carbon nanotube-ene carbon composites prepared in Example 30 at different magnifications Figure 35 SEM images of the carbon nanotube-ene carbon composites prepared in Example 31 at different magnifications Figure 36 TGA characterization diagram of the sample prepared in Comparative Example 1 Figure 37 SEM images of the sample prepared in Comparative Example 1 at different magnifications Figure 38 SEM images of the carbon nanotube-ene carbon composites prepared in Comparative Example 2 at different magnifications Figure 39 SEM images of the carbon nanotube-ene carbon composites prepared in Comparative Example 3 at different magnifications Figure 40 SEM images of the carbon nanotube-ene carbon composites prepared in Comparative Example 4 at different magnifications Figure 41 SEM images of the carbon nanotube-ene carbon composites prepared in Comparative Example 5 at different magnifications Figure 42 SEM images of the sample prepared in Comparative Example 6 at different magnifications Figure 43 SEM images of the carbon nanotube-ene carbon composites prepared in Comparative Example 7 at different magnifications Detailed implementation manners

[0026] Next, the technical solutions in the embodiments will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the embodiments to be described below are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0027] The statistical method for the yield of carbon nanotubes in the embodiments of the present invention is as follows: The weighed mass of the pre-growth carbon-ene material is denoted as W1, the weighed amount of the copper compound catalyst is denoted as W2, the mass fraction of copper element in the copper compound catalyst is a, and the mass of the obtained carbon nanotube-carbon-ene composite powder after growth is denoted as W3. Then the calculation formula for the yield is: (W3 - W1 - (W2 * a)) / a The reason for calculating the carbon nanotube yield in this way is that the additive will completely decompose at high temperature, so its mass is not included in the finally obtained carbon nanotube-carbon-ene composite powder. And the copper element-containing compound catalyst will also decompose at high temperature, leaving only copper to catalyze the growth of carbon nanotubes. Example 1

[0028] In this example, the additive is a reaction precursor for synthesizing carbon nitride, and the reaction precursor is specifically urea. And an indirect mixing method is used to mix the additive, the catalyst and the carbon-ene material.

[0029] A preparation method of a carbon nanotube-carbon-ene composite material includes the following steps: S1. First, weigh 0.6 g of urea and 0.0031 g of copper acetate monohydrate (the mass fraction of copper element in copper acetate monohydrate is 31.83%, so the actual content of copper in 0.0031 g of copper acetate monohydrate is 0.001 g), disperse them in absolute ethanol to construct a urea-supramolecular powder by ethanol assistance, and then stir and mix the obtained urea-supramolecular powder with 0.1 g of graphene powder evenly; S2. Fill the powder into a container and place it in a reaction device to grow according to a set program. After the growth is completed, cool it to room temperature and take it out. Specifically: load the powder in step S1 into a crucible and push it into a quartz tube furnace to grow according to a set program. The growth program is more specific as follows: introduce 100 sccm of hydrogen and 300 sccm of argon, raise the temperature to 550 °C and keep it at the same gas flow for 30 min. Then change the hydrogen flow rate to 5 sccm and the argon flow rate to 400 sccm, and raise the temperature to 850 °C. After the temperature reaches 850 °C, continue to keep it for growth for 30 min. During this period, the introduced gas is 20 sccm of ethylene, 40 sccm of hydrogen and 400 sccm of argon. After the growth is completed, cool it naturally to room temperature and take it out. Only a proper amount of inert gas is needed for protection during this period. The 550 °C heat preservation stage in this example is the stage for the additive to thermally polycondense to form carbon nitride. The carbon nitride generated in this stage has rich "nitrogen pots", that is, periodic holes composed of six nitrogen atoms in the plane, which provide rich active trapping sites for capturing metal ions, achieving the effects of uniform dispersion, anchoring and protection.

[0030] The scanning electron microscope image of the carbon nanotube-carbon-ene composite material prepared in Example 1 is as Figure 1As shown, it can be seen that carbon nanotubes grow densely and evenly on graphene, forming a carbon nanotube-graphene composite architecture material. The yield of carbon nanotubes under this process is shown in Table 1 as 148.65 / g催化剂 .

[0031] The carbon nanotube-reduced graphene oxide composite material of Example 1 was subjected to thermogravimetric analysis at a heating rate of 5 °C per minute from room temperature to 800 °C in an atmospheric environment at normal pressure. The TGA characterization results are as Figure 2 shown. Under the same conditions, the TGA characterization results of the raw material graphene oxide are as Figure 3 shown. The TGA characterization results of high-level single-walled carbon nanotubes (TUBALL of OCSiAl Company in Russia) internationally are as Figure 4 shown. The DTG curve has only one mass loss peak and no other loss peaks, indicating that the graphene-carbon nanotube composite material is a high-purity mixed phase and there are no impurity carbons with low decomposition temperatures; in the TG curve, the measured initial temperature of weight loss is 536.1 °C, proving that the composite material begins to thermally decompose at a temperature of 536.1 °C. There is no fluctuation in the TG curve in the range of 150 °C to 500 °C, and no metal oxidation reaction occurs. In addition, there is a slight mass increase peak near 790 °C in the TG curve, which is mainly due to the decomposition and ablation of the carbon nanotube-reduced graphene oxide composite material at this temperature, and the result of the catalyst being oxidized due to the loss of the carbon nanotube coating protection. This test proves the high-temperature stability of the carbon nanotube-reduced graphene oxide composite material and its catalyst in Example 1, mainly due to the use of a low catalyst dosage and the protection of the carbon nanotube tip shell layer, which is extremely beneficial for applications in scenarios around 500 °C.

[0032] It is also noted that the final residual mass of the carbon nanotube-reduced graphene oxide composite material after the ablation test TGA in an atmospheric environment is 6.18%. After removing the 3.8% intrinsic residue, i.e., ash, of the raw material graphene, the actual residue of the composite material is 2.38%. The final residual mass of high-level single-walled carbon nanotubes internationally after the ablation test TGA under the same conditions is 3.26%. It can be seen that fewer impurities are introduced during the preparation of the carbon nanotube-reduced graphene oxide composite material.

[0033] The carbon nanotube-reduced graphene oxide composite material of Example 1 was subjected to ICP testing, and the measured copper element content was 0.5217% of the total mass of the carbon nanotube-graphene composite material. Thus, it can be seen that the residual amount of catalytic metal in the composite material is small.

[0034] The Raman characterization result picture of the carbon nanotube-reduced graphene oxide composite material of Example 1 is as Figure 5As shown, it can be seen that the D peak at 1352.3 cm -1 , the G peak at 1580 cm -1 , and the 2D peak at 2687.2 cm -1 are observed. Compared with the raw material reduced graphene oxide, it can be found that for the carbon nanotube-reduced graphene oxide composite material after growing carbon nanotubes under the conditions of Example 1, the I D / I G decreases from 0.998 to 0.743, indicating that some extrinsic defects or structural defects of the reduced graphene oxide have been repaired to a certain extent. Example 2

[0035] In this example, different from Example 1, the additive, catalyst and ene-carbon material are mixed by the direct mixing method.

[0036] S1: Directly mix 0.1 g of graphene powder, 0.6 g of urea and an ethanol solution containing 0.0031 g of copper acetate monohydrate simultaneously, stir, and dry to volatilize ethanol; S2: The steps are the same as S2 in Example 1.

[0037] The scanning electron microscope image of the carbon nanotube-ene-carbon composite material prepared in Example 2 is as Figure 6 shown. It can be seen that carbon nanotubes grow densely and uniformly on graphene, forming a carbon nanotube-graphene composite architecture material. It can be known from Table 1 that the yield of carbon nanotubes under this growth condition is 126.47 / g催化剂 . Example 3

[0038] Different from Example 1, the ene-carbon material graphene, the additive carbon nitride, and the catalyst copper acetate monohydrate are mixed in an indirect mixing manner.

[0039] S1: First, prepare carbon nitride loaded with copper catalyst: First, weigh 0.6 g of urea and 0.0031 g of copper acetate monohydrate, disperse them in absolute ethanol for ethanol-assisted construction of supramolecular powder, place the constructed supramolecular powder in a tube furnace, heat it to 550 °C under an inert atmosphere and keep it warm for 30 min, then naturally cool it to room temperature under an inert atmosphere, take it out and crush it into powder, and finally obtain carbon nitride loaded with copper catalyst obtained by thermal polycondensation treatment of the supramolecular powder; Stir and mix the constructed carbon nitride loaded with copper catalyst and 0.1 g of reduced graphene oxide powder evenly; S2. Fill the powder into a container and place it in a reaction device to grow according to a set program. After the growth is completed, cool it to room temperature and take it out. Specifically: Load the powder in step S1 into a crucible and push it into a quartz tube furnace to grow according to a set program. The growth program is more specific as follows: Introduce 100 sccm of hydrogen and 300 sccm of argon. When the temperature rises to 550 °C, immediately change the hydrogen flow rate to 5 sccm and the argon flow rate to 400 sccm, and continue to heat up to 850 °C. After the temperature reaches 850 °C, continue to hold the temperature for growth for 30 min. During this period, the atmosphere introduced is 20 sccm of ethylene, 40 sccm of hydrogen, and 400 sccm of argon. After the growth is completed, cool it naturally to room temperature in an inert atmosphere and take it out.

[0040] The scanning electron microscope image of the carbon nanotube-graphene-carbon composite material prepared in Example 3 is as Figure 7 shown. It can be seen that carbon nanotubes grow densely and uniformly on graphene, forming a carbon nanotube-graphene composite architecture material. The yield of carbon nanotubes is statistically shown in Table 1 under this process as 115.6 / g催化剂 . Example 4

[0041] Different from Example 3, the graphene-carbon material graphene, the additive carbon nitride, and the catalyst copper acetate monohydrate are mixed in a direct mixing manner.

[0042] S1. Mix the graphene-carbon material graphene, the additive carbon nitride, and the catalyst copper acetate monohydrate in a certain proportion and manner. Specifically, it is a direct mixing method: Directly mix and stir 0.1 g of reduced graphene oxide powder, 0.1 g of carbon nitride, and an ethanol solution containing 0.0031 g of copper acetate monohydrate at the same time and dry to volatilize ethanol; S2. Fill the powder into a container and place it in a reaction device to grow according to a set program. After the growth is completed, cool it to room temperature and take it out. Specifically: Load the powder in step S1 into a crucible and push it into a quartz tube furnace to grow according to a set program. The growth program is more specific as follows: Introduce 100 sccm of hydrogen and 300 sccm of argon. When the temperature rises to 550 °C, immediately change the hydrogen flow rate to 5 sccm and the argon flow rate to 400 sccm, and continue to heat up to 850 °C. After the temperature reaches 850 °C, continue to hold the temperature for growth for 30 min. During this period, the atmosphere introduced is 20 sccm of ethylene, 40 sccm of hydrogen, and 400 sccm of argon. After the growth is completed, cool it naturally to room temperature in an inert atmosphere and take it out.

[0043] The scanning electron microscope image of the carbon nanotube-graphene-carbon composite material prepared in Example 3 is as Figure 8As shown, it can be seen that carbon nanotubes grow densely and uniformly on graphene, forming a carbon nanotube-graphene composite architecture material. The yield of carbon nanotubes under this process is shown in Table 1 as 100.08 / g催化剂 . Examples 5-6

[0044] What is different between Examples 5-6 and Examples 1-2 respectively is that the additive used is a reaction precursor for synthesizing carbon nitride, and the reaction precursor is specifically 0.5 g of cyanamide. The other steps of Example 5 are the same as those of Example 1, and the other steps of Example 6 are the same as those of Example 2.

[0045] Example 5 uses the indirect mixing method for mixing; Example 6 uses the direct mixing method for mixing.

[0046] Scanning electron microscope pictures of the carbon nanotube-graphene composite materials prepared in Examples 5-6 are as Figure 9 - 10 shown. Examples 7-8

[0047] What is different between Examples 7-8 and Examples 1-2 respectively is that the additive used is a reaction precursor for synthesizing carbon nitride, and the reaction precursor is specifically 0.45 g of dicyandiamide. The other steps of Example 7 are the same as those of Example 1, and the other steps of Example 8 are the same as those of Example 2.

[0048] Example 7 uses the indirect mixing method for mixing; Example 8 uses the direct mixing method for mixing.

[0049] Scanning electron microscope pictures of the carbon nanotube-graphene composite materials prepared in Examples 7-8 are as Figure 11 - 12 shown.

[0050] From Examples 1-8, it can be known that the efficiency of growing carbon nanotubes by the indirect mixing method is better than that of direct mixing: The applicant speculates that this is because under the direct mixing method, the catalyst cannot be fully and effectively loaded on the additive, but a part of it is directly mixed into the graphene sheets, and this part will aggregate into large nanoparticles during the heating growth process, losing catalytic activity, and the effective usage ratio of the catalyst is relatively reduced, thus also resulting in a relatively reduced growth efficiency of carbon nanotubes. However, it should be noted that the carbon nanotube yields of both the direct mixing and indirect mixing methods can reach 100 g / g催化剂 above, which still has obvious advantages compared with the dispersion method of silica-supported catalyst. Example 9

[0051] What is different between Example 9 and Example 1 is that the additive used is a reaction precursor for synthesizing carbon nitride, and the reaction precursor is specifically 0.6 g of thiourea.

[0052] S1. Example 9 uses the indirect mixing method for mixing; S2. It is the same as step S2 in Example 1.

[0053] The scanning electron microscope image of the carbon nanotube-ene carbon composite material prepared in Example 9 is as Figure 13 shown. Example 10

[0054] The difference between Example 10 and Example 1 is that the additive used is a reaction precursor for synthesizing carbon nitride, and the reaction precursor is specifically 0.3 g of melamine.

[0055] S1. Example 10 uses the indirect mixing method for mixing; S2. It is the same as step S2 in Example 1.

[0056] The scanning electron microscope image of the carbon nanotube-ene carbon composite material prepared in Example 10 is as Figure 14 shown. Example 11

[0057] The difference between Example 11 and Example 1 is that the additive used is a reaction precursor for synthesizing carbon nitride, and the reaction precursor is specifically 0.3 g of cyanuric acid.

[0058] S1. Example 11 uses the indirect mixing method for mixing; S2. It is the same as step S2 in Example 1.

[0059] The scanning electron microscope image of the carbon nanotube-ene carbon composite material prepared in Example 11 is as Figure 15 shown. Example 12

[0060] The difference between Example 12 and Example 1 is that the additive used is a reaction precursor for synthesizing carbon nitride, and the reaction precursor is specifically 0.4 g of cyanuric amide.

[0061] S1. Example 12 uses the indirect mixing method for mixing; S2. It is the same as step S2 in Example 1.

[0062] The scanning electron microscope image of the carbon nanotube-ene carbon composite material prepared in Example 12 is as Figure 16 shown. Example 13

[0063] The difference between Example 13 and Example 1 is that the additive used is a reaction precursor for synthesizing carbon nitride, and the reaction precursor is specifically 0.45 g of cyanuryl diamide.

[0064] S1. In Example 13, indirect mixing method is adopted for mixing; S2. It is consistent with step S2 in Example 1.

[0065] The scanning electron microscope image of the carbon nanotube-ene carbon composite material prepared in Example 13 is as Figure 17 shown. Example 14

[0066] The difference between Example 14 and Example 1 is that the additive used is the reaction precursor for synthesizing carbon nitride, and the reaction precursor is specifically 0.2 g of melamine.

[0067] S1. In Example 14, indirect mixing method is adopted for mixing; S2. It is consistent with step S2 in Example 1.

[0068] The scanning electron microscope image of the carbon nanotube-ene carbon composite material prepared in Example 14 is as Figure 18 shown.

[0069] From Examples 1-14, we can obtain that according to different additives, the ratio of the ene carbon material to the additive also varies. Generally speaking, the ratio of the ene carbon material to the additive is 1:1 - 20, preferably 1:1 - 9. Example 15

[0070] The difference from Example 1 is that the catalyst used is copper nitrate trihydrate, and its weighing amount is 0.0038 g (the mass fraction of copper element in copper nitrate trihydrate is 37.81%, so the actual content of copper in 0.0038 g of copper nitrate trihydrate is 0.001 g), and other steps are consistent with those in Example 1.

[0071] S1. In Example 15, indirect mixing is adopted for mixing: S2. It is consistent with step S2 in Example 1.

[0072] The scanning electron microscope image of the carbon nanotube-ene carbon composite material prepared in Example 15 is as Figure 19 shown. Example 16

[0073] The difference from Example 10 is that the catalyst used is copper chloride dihydrate, and its weighing amount is 0.0027 g, and other steps are consistent with those in Example 10.

[0074] S1. Example 16 uses an indirect mixing method for mixing: First, weigh 0.3 g of melamine and 0.0027 g of copper chloride dihydrate and disperse them in absolute ethanol to assist in constructing a melamine-copper supramolecular powder through ethanol, and then stir and mix the obtained melamine-copper supramolecular powder with 0.1 g of graphene powder evenly; S2. It is the same as step S2 in Example 1.

[0075] The scanning electron microscope image of the carbon nanotube-ene carbon composite material prepared in Example 16 is as Figure 20 shown. Example 17

[0076] Different from Example 13, the catalyst used is copper acetylacetonate, and its weighed amount is 0.0041 g, and other steps are the same as those in Example 13.

[0077] S1. Example 17 uses an indirect mixing method for mixing: S2. It is the same as step S2 in Example 1.

[0078] The scanning electron microscope image of the carbon nanotube-ene carbon composite material prepared in Example 17 is as Figure 21 shown.

[0079] From Example 1 and Examples 15-17, we can see that different catalysts can also catalyze the growth of carbon nanotubes on the ene carbon material. Therefore, it can be known that the effective element in the catalyst is copper. Example 18

[0080] A preparation method of a carbon nanotube-ene carbon composite material includes the following steps: S1. The same as Example 1; S2. Change the high-temperature growth temperature from 850 to 800 °C, and the rest is the same as Example 1.

[0081] The scanning electron microscope image of the carbon nanotubes and their ene carbon composite material prepared in Example 18 is as Figure 22 shown. From Figure 22 it can be seen that when the growth temperature drops to 800 °C, the growth density of the carbon nanotubes becomes lower and the yield in Table 1 drops to 65.82. This is due to the incomplete cracking of the carbon source. For the carbon source ethylene, its optimal cracking temperature is 850 °C, and for other carbon source materials, their optimal cracking temperatures are between 750 and 900 °C. Example 19

[0082] A preparation method of carbon nanotubes and their ene carbon composite material includes the following steps: S1. The same as Example 1; S2. Change the carbon source type to ethanol. Add ethanol to the bubbling device and keep it at a constant temperature of 40°C. The ethanol vapor is carried out by 20 sccm of inert gas. The rest is the same as in Example 1.

[0083] The scanning electron microscope images of the carbon nanotubes and their graphene-carbon composites prepared in Example 19 are respectively as Figure 23 shown. It can be seen that the carbon nanotubes grow uniformly on the graphene sheets and the size distribution is relatively uniform. The yield in Table 1 is 95.47, which has a large gap compared with Example 1. This is mainly due to the different carbon-containing active substances decomposed from different carbon sources at high temperatures and their different effective usage amounts. That is, at 850°C, the amount of carbon active substances decomposed from ethanol that can be provided to the catalyst for the effective growth of carbon nanotubes is less than that decomposed from ethylene. However, this example also proves that other carbon sources such as ethanol are also applicable to the growth of carbon nanotubes under this mechanism. Example 20

[0084] A method for preparing carbon nanotubes and their graphene-carbon composites, comprising the following steps: S1. The same as in Example 19; S2. Change the high-temperature growth temperature from 850°C to 900°C. The rest is the same as in Example 1.

[0085] The scanning electron microscope images of the carbon nanotubes and their graphene-carbon composites prepared in Example 20 are respectively as Figure 24 shown. Compared with the pyrolysis temperature of 850°C, more carbon active substances are decomposed from ethanol at 900°C, and thus the yield of carbon nanotubes is higher, reaching 121.54. This further shows that for different carbon source materials, the optimal pyrolysis temperature is also different, and the optimal pyrolysis temperature is between 750 and 900°C.

[0086] Example 21 A method for preparing carbon nanotube-graphene-carbon composites, comprising the following steps: S1. The same as in Example 1; S2. Change the temperature in the polycondensation stage from 550 to 600°C. The rest is the same as in Example 1.

[0087] The scanning electron microscope images of the carbon nanotubes and their graphene-carbon composites prepared in Example 21 are respectively as Figure 25 shown. It can be seen from Table 1 that the yield is 127.21. Examples 22 - 27

[0088] A method for preparing carbon nanotubes and their graphene-carbon composites, comprising the following steps: S1. The same as in Example 1; S2. Change the flow rate of hydrogen in the growth stage at 850 °C to 20 sccm, 30 sccm, 50 sccm, 60 sccm, 70 sccm, and 80 sccm respectively, and the rest is the same as in Example 1; Scanning electron microscope images of the carbon nanotubes and their graphene-carbon composites prepared in Examples 22-27 are respectively as Figure 26 - 31 shown. It can be seen that the carbon nanotubes grow uniformly on the graphene, with uniform sizes and no obvious differences in morphology. From Table 1, it can be seen that as the amount of hydrogen added increases, the yield of carbon nanotubes first increases and then decreases. That is, when the hydrogen amount increases from 20 sccm to 40 sccm, the yield increases from 118.74 at 20 sccm to 148.65 g / g催化剂 , and when the hydrogen amount continues to increase to 80 sccm, the yield decreases from 148.65 g / g催化剂 at 40 sccm to 119.04 / g催化剂 at 80 sccm. It can be seen that within a certain range, hydrogen plays a positive role in promoting the cracking of the carbon source and the formation of sp2 carbon, while when it exceeds the critical value, hydrogen will act as an etchant to etch the carbon nanotubes and graphene, playing a reverse role. Example 28

[0089] A method for preparing a carbon nanotube and its graphene-carbon composite, comprising the following steps: S1. The same as in Example 1; S2. The flow rate of hydrogen in the high-temperature heating stage from 550 °C to 850 °C is 100 sccm, and the rest is the same as in Example 1; Example 29

[0090] A method for preparing a carbon nanotube and its graphene-carbon composite, comprising the following steps: S1. The same as in Example 1; S2. The flow rate of hydrogen in the high-temperature heating stage from 550 °C to 850 °C is 0 sccm, and the rest is the same as in Example 1; Example 30

[0091] A method for preparing a carbon nanotube and its graphene-carbon composite, comprising the following steps: S1. The same as in Example 1; S2. Change the flow rate of hydrogen in the high-temperature heating stage from 550 °C to 850 °C to 20 sccm, and the rest is the same as in Example 1; Example 31

[0092] A method for preparing a carbon nanotube and its graphene-carbon composite, comprising the following steps: S1. The same as in Example 1; S2. Change the hydrogen flow rate during the high-temperature heating stage from 550 °C to 850 °C to 10 sccm, and the rest is the same as in Example 1; Scanning electron microscope images of the carbon nanotubes and their graphene-carbon composites prepared in Examples 28-31 are respectively as Figure 32 - 35 shown.

[0093] As can be seen from Examples 28 and 30, excessive hydrogen introduction will lead to a decrease in the yield of carbon nanotubes, because the introduction of excessive hydrogen etches the graphene-carbon material itself.

[0094] As can be seen from Example 29, if no hydrogen is introduced, the growth uniformity of carbon nanotubes will deteriorate, and the yield of carbon nanotubes will also decrease. This is because the additive decomposes to release carbon- and nitrogen-containing fragments at this stage, and these carbon- and nitrogen-containing fragments adhere to the metal catalyst to form a carbon shell covering the metal catalyst, resulting in partial inactivation of the catalyst. Comparative Example 1

[0095] A method for preparing a carbon nanotube-graphene-carbon composite, comprising the following steps: S1. Except that urea is not added in step S1, that is, 0.0031 g of the catalyst copper acetate monohydrate is directly dissolved in an appropriate amount of ethanol and stirred and mixed with graphene for drying, and the rest of the steps and parameters are the same as in Example 1; S2. The same as in Example 1; Compared with Example 1, the difference between Comparative Example 1 and it is that urea is not added. From Figure 36 it can be seen that the DTG curve in the TGA result of Comparative Example 1 without adding urea has two obvious mass loss peaks. The one at 525.6 °C corresponds to the decomposition loss peak of sp 3 amorphous carbon, and the sp 2 main decomposition loss peak at 563.1 °C. In addition, its TG curve has an obvious 2.39% mass increase after 200 °C, which is mainly attributed to the oxidation of the copper catalyst. More intuitively, from Figure 37 the SEM picture of Comparative Example 1 in Figure 1 it can be seen that almost no obvious carbon nanotube structure is generated on the graphene. The catalyst is not protected by the carbon tube tip sheath and is in an exposed state, and it is easily oxidized in the high-temperature atmospheric atmosphere during the TGA test. Although the yield of Comparative Example 1 in Table 1 is 137.66, which is not much different from 148.65 of Example 1, combining the SEM comparison in Figure 36 Figure 37 with 3The formation of amorphous carbon, due to the lack of urea as an additive, on the one hand, loses the dispersion and anchoring of the catalyst. During the heating and growth process, the catalyst metal ions directly change from ionic clusters to large-sized nanoparticles step by step, losing the ability to catalyze the growth of carbon nanotubes. On the other hand, due to the lack of additive urea, there are no effective nitrogen-containing fragments in the atmosphere to act as amorphous carbon inhibitors to protect the activity of the catalyst and act as growth promoters to promote the migration and diffusion of carbon atoms on the catalyst surface, thereby improving the yield. Comparative Example 2

[0096] Using silica as a dispersant to load and disperse the catalyst for growth, the specific steps are as follows: S1: First, weigh 0.025 g of nanoscale silica particles with a particle size of 15 nm, then weigh 0.0031 g of copper acetate monohydrate, disperse the two in anhydrous ethanol, and stir and mix the mixture with 0.1 g of graphene powder and dry it; S2: Fill the powder into a container and place it in a reaction device to grow according to a set program. After the growth is completed, cool it to room temperature and take it out. Specifically: Load the powder in step S1 into a crucible and push it into a quartz tube furnace to grow according to a set program. The growth program is more specific as follows: Pass 300 sccm of argon gas to raise the temperature to 700 °C. After the temperature reaches 700 °C, change the gas to 5 sccm of hydrogen and 400 sccm of argon and raise the temperature to 850 °C. After the temperature reaches 850 °C, keep it warm for 5 min. After 5 min, pass 20 sccm of ethylene, 40 sccm of hydrogen, and 400 sccm of argon and continue to keep it warm and grow for 30 min. After the growth is completed, cool it naturally to room temperature in an inert atmosphere and take it out. Comparative Example 3

[0097] Using silica as a dispersant to load and disperse the catalyst for growth, the specific steps are as follows: S1: Change the weighed amount of nanoscale silica to 0.05 g, and the rest is the same as Comparative Example 2; S2: The same as Comparative Example 2; Comparative Example 4

[0098] Using silica as a dispersant to load and disperse the catalyst for growth, the specific steps are as follows: S1: Change the weighed amount of nanoscale silica to 0.1 g, and the rest is the same as Comparative Example 2; S2: The same as Comparative Example 2; Comparative Example 5

[0099] Using silica as a dispersant to load and disperse the catalyst for growth, the specific steps are as follows: S1: Change the weighed amount of nanoscale silica to 0.2 g, and the rest is the same as Comparative Example 2; S2: Consistent with Comparative Example 2; Scanning electron microscope images of the carbon nanotube-graphene composite materials prepared in Comparative Examples 2-5 are respectively as Figure 38 - 41 shown. It can be seen that as long as the dispersion uniformity of copper ions is controlled, the silica nanoparticle-supported dispersion catalyst can also effectively grow carbon nanotubes. However, the morphology of the carbon nanotubes grown by silica dispersion is relatively disordered, and the size distribution is chaotic. Moreover, even with the increase in the amount of silica added, the dispersion performance is not effectively improved, but instead the tube diameter becomes thicker. This is attributed to the fact that with the increase in the amount of silica nanoparticles, the probability of their agglomeration becomes greater, resulting in the catalyst also agglomerating into large particles, thereby generating short tubes with large diameters. In addition, this silica dispersion strategy also brings an obvious problem, that is, the introduction of silica will become an impurity, and after the growth is completed, it is necessary to perform secondary treatment of pickling and etching to remove silica to obtain the final graphene-carbon nanotube composite material, which is time-consuming and laborious and the effect is not good. Comparative Example 6

[0100] A preparation method of a carbon nanotube-graphene composite material includes the following steps: S1. Change the catalyst to ferric chloride hexahydrate, and the weighed amount is 0.0048 g, and the rest is the same as in Example 1; S2. The same as in Example 1; The scanning electron microscope image of the carbon nanotube-graphene composite material prepared in Comparative Example 6 is shown in Figure 42. Comparative Example 7

[0101] A preparation method of a carbon nanotube-graphene composite material includes the following steps: S1. Change the catalyst to ferric chloride hexahydrate and copper acetate monohydrate, and the ratio of the two is 1:3, that is, weigh 0.0012 g of ferric chloride hexahydrate and 0.0024 g of copper acetate monohydrate, and the rest is the same as in Example 1; S2. The same as in Example 1; The scanning electron microscope image of the carbon nanotube-graphene composite material prepared in Comparative Example 7 is as Figure 43 shown.

[0102] The carbon nanotube yield results corresponding to Examples 1-31 and Comparative Examples 1-7 are shown in Table 1:

[0103] As described above, the specific implementation manners of the present invention are provided, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A preparation method of a carbon nanotube-graphite carbon composite material, characterized in that, It includes the following steps: Mix the ene-carbon material, additive, and catalyst, then place them into a reaction device, introduce an inert gas, hydrogen, and a carbon source, and grow carbon nanotubes according to the growth procedure. The additive is carbon nitride or a reaction precursor for synthesizing carbon nitride; The growth procedure includes a medium-temperature heating stage, a high-temperature heating stage, and a high-temperature growth stage. The medium-temperature heating stage is to heat from room temperature to 500-600 °C; the high-temperature heating stage is to heat from 500-600 °C to 750-900 °C; the temperature in the high-temperature growth stage is 750-900 °C, and the growth time is 10-50 min.

2. A method for preparing the carbon nanotube-graphite carbon composite material as described in claim 1, characterized in that, The carbon source is one or more of gaseous olefins, gaseous alkynes, liquid alcohols, liquid ketones, and liquid benzenes.

3. A method for preparing a carbon nanotube-graphite carbon composite material as described in claim 2, characterized in that, The carbon source is one or more of ethylene, acetylene, methanol, ethanol, acetone, benzene, and toluene.

4. A method for preparing a carbon nanotube-graphite carbon composite material as described in claim 1, characterized in that, The catalyst is a compound or mixture containing free copper ions.

5. A method for preparing a carbon nanotube-graphite carbon composite material as described in claim 4, characterized in that, The catalyst includes one or more of copper chloride, copper sulfate, copper nitrate, copper acetate, and the metal organic complex copper acetylacetonate.

6. A method for preparing a carbon nanotube-graphite carbon composite material as described in claim 1, characterized in that, The additive is a reaction precursor for synthesizing carbon nitride. The growth procedure further includes a polycondensation stage. The temperature in the polycondensation stage is 500-600 °C, and the polycondensation time is 10-50 min.

7. A method for preparing a carbon nanotube-graphite carbon composite material according to any one of claims 1-6, characterized in that, In the high-temperature heating stage, the volume of hydrogen introduced accounts for 0.5%-2.5% of the total volume of hydrogen and the inert gas.

8. A method for preparing a carbon nanotube-graphite carbon composite material according to any one of claims 1-6, characterized in that, In the high-temperature growth stage, the volume of hydrogen introduced accounts for 4%-20% of the total volume of hydrogen and the inert gas.

9. A carbon nanotube-ene carbon composite material, characterized in that, The carbon nanotube-ene-carbon composite material is prepared by using the preparation method according to any one of claims 1-8.

10. Use of the carbon nanotube-ene-carbon composite material according to claim 9 in the fields of energy, sensing, thermal management, catalysis, and mechanical reinforcement.

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