Use method of nitrogen-containing heterocyclic ring additive and olefinic carbon composite material prepared by using nitrogen-containing heterocyclic ring additive

Abstract

The invention discloses a using method of a nitrogen-containing heterocyclic ring additive and an olefinic carbon composite material obtained by adopting the method, and relates to the fields of carbon nanotube preparation, material composite modification, olefinic carbon composite material preparation and graphene defect repair. The additive is g-C3N4 or a reaction precursor for synthesizing the g-C3N4; the additive is used for growing carbon nanotubes on an olefinic carbon material. The preparation method of the olefinic carbon composite material comprises the following steps: S1, mixing an olefinic carbon material, an additive and a catalyst according to a certain proportion in a manner; and S2, filling a container with the powder, placing the container in reaction equipment for growth according to a set program, and cooling to room temperature after the growth is finished to obtain the final carbon nanotube-olefinic carbon composite powder material. The obtained olefinic carbon material is applied to the fields of energy, sensing, thermal management, catalysis and mechanical enhancement. The preparation process is simple, the growth efficiency is high, batch and large-scale production can be realized, and the nitrogen-containing heterocyclic ring additive is innovatively applied to preparation of the carbon nanotube-olefinic carbon composite material.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon nanotube material preparation, and in particular to a method for using a nitrogen-containing heterocyclic additive to grow carbon nanotubes on the surface of an olefinic carbon material and an olefinic carbon composite material prepared using the nitrogen-containing heterocyclic additive. Background Art

[0002] Graphene and carbon nanotubes are two highly representative members of the carbon family. Graphene is a single-layer, hexagonal honeycomb-like, quasi-two-dimensional carbon material composed of carbon atoms bonded in an sp2 hybridized pattern, while carbon nanotubes can be considered hollow, tubular, one-dimensional nanomaterials formed by graphene curled in a specific direction. Both are widely used in energy, aerospace, thermal management, and other fields due to their excellent physical, chemical, and mechanical properties. Furthermore, the broader carbon family also includes single materials such as graphite and carbon black, as well as composites composed of any two or more of these materials.

[0003] In the design of composite materials, any combination of zero-dimensional, one-dimensional and two-dimensional materials of different dimensions can be used as a strategy to effectively construct three-dimensional structural composite materials. The introduction of materials of different dimensions can effectively improve the agglomeration and restacking problems of themselves and other phase materials. For example, 1) the introduction of zero-dimensional carbon black SP nanoparticles into two-dimensional graphene powder can effectively inhibit the agglomeration and restacking problems of graphene sheets by virtue of the "Blocking effect" of its nanoparticles; 2) the introduction of one-dimensional carbon nanotubes into graphene can also effectively improve the problems of easy agglomeration and stacking of graphene and carbon nanotubes themselves and difficult dispersion.

[0004] The traditional and commonly used method for composite materials is physical mixing, which relies on mechanical stirring and shearing force to mix the materials evenly. For example, SCI papers "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 "CN 116332168A, A preparation method and application of graphene-carbon nanotube composite materials", only uses simple mechanical stirring to mix graphene and carbon nanotubes. 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 into the dispersion of graphene and carbon nanotubes. The introduction of these additives will inevitably have a significant negative effect on the subsequent practical application and performance. However, direct in-situ growth through chemical vapor deposition (CVD) can avoid the above problems, and the uniformity and performance of the resulting composite material far exceed those of traditional physical mixing methods.

[0005] Thanks to its high affinity for carbon, typical nickel dissolves only 1.3% carbon atoms at 1000°C. Iron, cobalt, nickel, and alloys of other metals with any of these three elements are currently common catalysts for carbon nanotube growth. For example, SCI papers 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," and "The Use of Diatomite as a Catalyst Carrier for the Synthesis of Carbon Nanotubes" demonstrate the growth of carbon nanotubes by loading catalysts such as iron and nickel onto various supports. However, due to their strong affinity for carbon, these catalysts can be difficult to remove after growth, along with the resulting metal carbides. In addition, the effective catalytic introduction of such catalysts usually requires the use of magnesium oxide, aluminum oxide, silicon dioxide, zeolite, diatom mud, etc. as carriers for loading and dispersion, which inevitably introduces foreign impurities such as carriers, and later requires a large number of processes for pickling, etching, fumigation and secondary purification.

[0006] Copper (Cu) was once considered a weak CNT growth catalyst due to its weak metal-carbon interaction and a solubility of only 0.04% atom of carbon at 1000°C.

[0007] Chinese patent "CN 114068927 A, Graphene Carbon Nanotube Composite Material and Preparation Method Thereof" successfully grew and prepared carbon nanotubes on graphene powder using fluidized bed equipment. However, there were problems such as high growth temperature, low carbon nanotube growth density and yield, complex process, high catalyst dosage, residual impurities, and the need for secondary treatment. Summary of the Invention

[0008] In response to the above-mentioned problems, the present invention innovatively introduces the construction of supramolecular-metal catalysts and carbon nitride g-C3N4 loaded dispersed catalysts into the preparation process of carbon nanotubes and graphene-carbon nanotube composites to achieve uniformly dispersed loading of the catalyst.

[0009] The carbon nitride g-C3N4 generated by a substance that can generate carbon nitride, or the carbon nitride g-C3N4 itself, as an effective metal atom dispersant, can evenly load and disperse the catalyst. At the same time, the nitrogen element introduced by these additives can not only effectively facilitate the anchoring of metal atoms on the surface of inert carbon materials such as graphene, but also the nitrogen-containing active substances generated by the decomposition of carbon nitride during high-temperature growth can effectively improve the catalytic activity of the catalyst, promote the diffusion and migration of carbon atoms, and inhibit the production of amorphous carbon, thereby achieving high yield, high purity, no dispersed carrier residue, low catalyst residue, and the growth of carbon nanotubes and their graphene composites without the need for secondary pickling, fumigation and etching treatment, and can achieve a certain degree of defect repair on the graphene substrate.

[0010] The specific solution provided by the present invention is a method for using a nitrogen-containing heterocyclic additive, wherein the additive is g-C3N4 or a reaction precursor for synthesizing g-C3N4, and the additive is applied to the process of growing carbon nanotubes on the surface of graphene; during the growth process of the carbon nanotubes, the additive, catalyst and olefinic carbon material are mixed, and the additive uniformly disperses and anchors the catalyst. After heat treatment, the catalyst causes the carbon nanotubes to grow on the surface of the olefinic carbon material according to the top growth mode.

[0011] In a further technical solution, the additive is g-C3N4. Carbon nitride has abundant "nitrogen pots," i.e., periodic holes composed of six nitrogen atoms within a plane, which provide abundant active trapping sites for capturing metal ions, achieving uniform dispersion, anchoring, and protection.

[0012] In another technical solution of the present invention, the additive is a reaction precursor for synthesizing g-C3N4. Similar to the above principle, other reaction precursors for synthesizing g-C3N4 also have good dispersion and anchoring effects on metal ions. The reaction precursors for synthesizing g-C3N4 and metal ions construct a supramolecular architecture, which can achieve primary dispersion and anchoring, and then in-situ thermal polycondensation into carbon nitride to achieve secondary dispersion and anchoring.

[0013] In a further technical solution, the reaction precursor is cyanamide, dicyandiamide, urea, thiourea, cyanuric acid, melamine, cyanuramide, cyanuric diamide or melemamine.

[0014] In a further technical solution, the olefinic carbon material is a material in which carbon atoms are bonded in an sp2 hybridization manner or in an sp3 hybridization manner.

[0015] In a further technical solution, the olefinic carbon material is a material formed by carbon atoms being bonded in an sp2 hybrid manner.

[0016] In a further technical solution, the carbon-olefin material is graphene, carbon fiber, flake graphite, expanded graphite or worm graphite. Preferably, the carbon-olefin material is graphene.

[0017] In another technical solution of the present invention, the olefinic carbon material is a material formed by combining in an sp3 hybrid manner.

[0018] In a further technical solution, the olefinic carbon material is any one of carbon black and Ketjen black.

[0019] In a further technical solution, the catalyst is a metal catalyst with low carbon solubility, wherein the solubility of carbon in the catalyst is S ≤ 0.1% atom at 1000°C. In this application, the carbon nanotubes grow in a tip-up growth mode. This tip-up growth mode is primarily dependent on the interaction between the catalyst and graphene, requiring a catalyst with very weak carbon affinity and carbon solubility.

[0020] In a further technical solution, the metal catalyst is a solvent-soluble compound containing free copper ions. The solubility of carbon in copper at 1000°C is only 0.04% atom, so the binding force of graphene on the copper catalyst is far less than the driving force for carbon nanotube growth, causing the copper catalyst to migrate along the direction of carbon nanotube growth. Therefore, choosing a compound containing free copper ions as the catalyst can achieve the desired effect of this solution.

[0021] In a further technical solution, the metal catalyst includes any one or more of copper chloride and its hydrate, copper sulfate and its hydrate, copper nitrate and its hydrate, copper acetate and its hydrate, and a metal organic complex copper acetylacetonate.

[0022] Another object of the present invention is to provide an olefin-carbon composite material, which is prepared by using the above-mentioned additives.

[0023] In a further technical solution, the olefin-carbon composite material can be applied in the fields of energy, sensing, thermal management, catalysis, and mechanical reinforcement.

[0024] Innovations and beneficial effects: The innovative approach of combining supramolecular metal catalyst construction with carbon nitride-loaded dispersed catalysts is introduced into the carbon nanotube growth process. First, a supramolecular structure is constructed using metal salts and organic additives. Free metal ions and organic additives form a supramolecular compound through hydrogen bonding. This supramolecular construction allows the metal ions acting as catalysts to be evenly dispersed and anchored within the supramolecular framework, preventing ion aggregation and the formation of large ion clusters. If g-C3N4 is used as a precursor for the synthesis of these catalysts, the constructed supramolecular structure can be subjected to a high-temperature thermal polycondensation process to form catalyst-loaded carbon nitride. Alternatively, g-C3N4 can be used directly to form catalyst-loaded carbon nitride. Carbon nitride, a commonly used metal single-atom catalyst support, can achieve monodisperse anchoring of metal atoms, protecting copper atoms and preventing premature agglomeration and the disordered formation of large nanoparticles, which can lead to a loss of catalytic activity. The graphite phase carbon nitride loaded with single-atom catalyst metal is further heated until it reaches the growth temperature of carbon nanotubes. After exceeding a certain temperature, its structure begins to decompose, and the single-atom copper evenly dispersed and anchored on the skeleton begins to be released and aggregated in an orderly manner into nanoparticles of a certain uniform size, thereby ensuring the generation of carbon nanotubes with uniform tube diameter and morphology.

[0025] Secondly, after high-temperature growth, carbon nitride completely decomposes, leaving no impurities and maintaining high purity. This eliminates the need for acid washing and etching to remove catalyst dispersion supports such as silica, alumina, magnesium oxide, and diatom mud, as is required in conventional methods. The nitrogen-containing active substances released during the decomposition process not only inhibit the formation of amorphous carbon, ensuring high-purity synthesis of carbon nanotubes, but also promote the migration and diffusion of carbon atoms on the catalyst surface, maintaining catalyst activity and achieving high-yield synthesis of carbon nanotubes. Furthermore, thanks to the aforementioned supramolecular anchoring and dispersion, the carbon nitride is anchored and dispersed by single atoms. The decomposition of carbon nitride releases nitrogen-containing substances, which inhibit amorphous carbon, promote the diffusion and migration of carbon atoms, and maintain catalytic activity. Consequently, the catalyst dosage required is extremely low, only 1%wt, eliminating the need for cumbersome fumigation and etching processes to remove the metal catalyst. Finally, the synthesis process is simple and universal, with a wide range of raw materials available. It is not limited by specialized synthesis production equipment and can achieve large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 This is the SEM image corresponding to Example 1.

[0028] Figure 2 This is the transmission electron microscope (TEM) characterization result picture corresponding to Example 1; Figure 3 This is the SEM image corresponding to Example 2; Figure 4 This is the SEM image corresponding to Example 3; Figure 5 This is the SEM image corresponding to Example 4; Figure 6 This is the SEM image corresponding to Example 5; Figure 7 This is the SEM image corresponding to Example 6; Figure 8 This is the SEM image corresponding to Example 7; Figure 9 This is the SEM image corresponding to Example 8; Figure 10 This is the SEM image corresponding to Example 9; Figure 11 This is the SEM image corresponding to Example 10; Figure 12 This is the SEM image corresponding to Example 11; Figure 13 This is the SEM image corresponding to Example 12; Figure 14 This is the SEM image corresponding to Example 13; Figure 15 This is the SEM image corresponding to Example 14; Figure 16 This is the SEM image corresponding to Example 15; Figure 17 This is the SEM image corresponding to Example 16; Figure 18 This is the SEM image corresponding to Example 17; Figure 19 This is the SEM image corresponding to Comparative Example 1; Figure 20 This is the SEM picture corresponding to Comparative Example 2. DETAILED DESCRIPTION

[0029] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments. Obviously, the embodiments described below are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention. DETAILED DESCRIPTION

[0030] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments. Obviously, the embodiments described below are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention. Example 1

[0031] In this embodiment, the additive is a reaction precursor for synthesizing carbon nitride, and the reaction precursor is specifically urea. indirect Mixing is performed by mixing.

[0032] A method for preparing a carbon nanotube-olefin carbon composite material comprises the following steps: S1. First weigh 0.6 g of urea and 0.0031 g of copper acetate monohydrate were dispersed in anhydrous ethanol for ethanol-assisted construction of urea - supramolecular powder, and then the obtained urea - supramolecular powder was stirred and mixed with 0.1 g of graphene powder; S2. Fill the powder into a container and place it in a reaction device to grow according to the 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 the set program. The growth program is more specific as follows: introduce 100sccm of hydrogen and 300sccm of argon, raise the temperature to 550°C and keep it warm for 30 minutes at the same atmosphere flow rate, then change the hydrogen introduction rate to 5sccm and the argon introduction rate to 400sccm, raise the temperature to 850°C, and continue to keep warm and grow for 30 minutes after the temperature reaches 850°C. During this period, the atmosphere introduced is 20sccm of ethylene, 40sccm of hydrogen and 400sccm of argon. After the growth is completed, naturally cool it to room temperature and take it out. During this period, you only need to pass an appropriate amount of inert atmosphere for protection. The 550°C insulation stage in step 2 of this embodiment is the stage where the additive is thermally condensed to generate carbon nitride. The carbon nitride generated in this stage has abundant "nitrogen pots", that is, periodic holes composed of six nitrogen atoms in the plane, which provide abundant active trapping sites for capturing metal ions, thereby achieving the effect of uniform dispersion, anchoring and protection.

[0033] The scanning electron microscope images of the carbon nanotubes and their olefin-carbon composite materials prepared in Example 1 are as follows: Figure 1 As shown, from Figure 1The uniform growth of carbon nanotubes on the graphene is clearly visible, with catalyst particles visible on some tubes and stretched and deformed catalyst within the tubes. The presence of catalyst at the tips of the carbon nanotubes and the appearance of catalyst droplets as they grow indicate that the copper-catalyzed carbon nanotube growth process follows the VLS (vapor-liquid-solid) growth mechanism, with the catalyst particles moving in the direction of the carbon nanotube growth during growth. Figure 1 It can be seen that the carbon nanotubes grow densely and evenly on the graphene, forming a carbon nanotube-graphene composite structure material. The yield of carbon nanotubes after multiple growth statistics is shown in Table 1, which is 148.65g / g催化剂 The yield of carbon nanotubes is calculated as follows: the weighed mass of the olefinic carbon material before growth is W1, the weighed amount of the copper-containing compound catalyst is W2, the mass proportion of the copper element in the copper-containing compound catalyst is a, and the mass of the carbon nanotube-olefinic carbon composite powder obtained after growth is W3. The yield calculation formula is: (W3-W1-(W2*a)) / a.

[0034] The results of TEM characterization of carbon nanotubes and their olefin-carbon composites prepared in Example 1 are shown in the figure below: Figure 2 As shown, from Figure 2 From a, we can see that the carbon nanotubes are evenly embedded in the graphene sheets. Figure 2 In b, it can be seen that the carbon nanotubes are multi-walled carbon nanotubes, which are in the shape of bamboo nodes. They can be seen as a series of stacked cones that are seamlessly connected. The outer wall thickness is uniform, and the inner wall thickness gradually tapers from the bottom to the tip. The cavity boundary structure is obvious and clear. Figure 2 c Under high-resolution transmission, parallel lattice fringes arranged at a certain angle to the growth axis can be clearly seen. Example 2

[0035] A method for preparing a carbon nanotube-olefin carbon composite material, comprising the following steps: The carbon material graphene, the additive carbon nitride and the catalyst copper acetate monohydrate are mixed in an indirect mixing manner.

[0036] S1. First, prepare carbon nitride loaded with copper catalyst: first weigh 0.6g of urea and 0.0031g of copper acetate monohydrate and disperse them in anhydrous ethanol to perform ethanol-assisted construction of supramolecular powder, place the constructed supramolecular powder in a tube furnace under an inert atmosphere, heat it to 550°C and keep it warm for 30 minutes, then naturally cool it to room temperature under an inert atmosphere, take it out and crush it into powder, finally heat the supramolecular powder to obtain carbon nitride loaded with copper catalyst; stir and mix the constructed carbon nitride loaded with copper catalyst with 0.1g of reduced graphene oxide powder; S2. Fill the powder into a container and place it in a reaction device to grow according to the 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 the set program. The growth program is more specific as follows: introduce 100sccm of hydrogen and 300sccm of argon. When the temperature reaches 550°C, immediately change the hydrogen introduction amount to 5sccm and the argon introduction amount to 400sccm. Continue to heat it to 850°C. After the temperature reaches 850°C, continue to keep it warm and grow for 30 minutes. During this period, the atmosphere introduced is 20sccm of ethylene, 40sccm of hydrogen and 400sccm of argon. After the growth is completed, naturally cool it to room temperature under an inert atmosphere and take it out. During this period, only an appropriate amount of inert atmosphere needs to be passed for protection.

[0037] The scanning electron microscope image of the carbon nanotube-olefin carbon composite material prepared in Example 2 is as follows: Figure 3 As shown in Table 1, it can be seen that carbon nanotubes grow densely and evenly on graphene, forming a carbon nanotube-graphene composite structure material. The yield of carbon nanotubes under this process is 115.6 / g催化剂 .

[0038] The construction of supramolecular compounds can evenly disperse and anchor metal ions on the supramolecular skeleton, avoiding the formation of large ion clusters caused by ion agglomeration. The construction of supramolecular structure compounds can achieve primary dispersion anchoring of the catalyst, and then form carbon fluoride loaded with metal single atoms through in-situ heat shrinkage to achieve secondary dispersion anchoring of the catalyst. The double dispersion anchoring achieves uniform anchoring and dispersion of the catalyst. The degree of uniform dispersion of the catalyst directly affects the size of the catalyst, and thus affects the morphology, size, diameter and yield of the catalytically grown carbon tubes. Carbon nitride can be regarded as highly nitrogen-doped graphene. As a two-dimensional layered material, its layers are also very easy to self-stack through π-π interactions. In Example 3, uniformly dispersed carbon nitride anchored with copper atoms was first prepared by constructing a supramolecular structure, which was then added to reduced graphene oxide powder for carbon nanotube growth. Despite the primary dispersion and anchoring achieved by the supramolecular structure and the secondary dispersion and anchoring achieved by in situ generation of the carbon nitride, the urea-catalyst supramolecular structure lost the auxiliary dispersion provided by the reduced graphene oxide during thermal shrinkage to form the carbon nitride. Consequently, the resulting dispersed carbon nitride anchored with copper atoms exhibited severe agglomeration and hardening. Despite being ground prior to addition to the reduced graphene oxide for growth, the carbon nitride was unable to achieve uniform coating on the graphene oxide powder, resulting in uneven aggregation areas. This resulted in uneven size distribution of the grown carbon nanotubes and a lower yield compared to Example 1. Example 3

[0039] In this embodiment, the additive is a reaction precursor for synthesizing carbon nitride, and the reaction precursor is specifically cyanamide.

[0040] S1: the carbon material is graphene, and the addition amount is 0.1 g; the additive is cyanamide, and the addition amount is 0.5 g; the catalyst is copper acetate monohydrate, and the addition amount is 0.0031 g; the remaining steps are consistent with Example 1.

[0041] S2: The specific operations are the same as those in Example 1.

[0042] The scanning electron microscope images of the carbon nanotubes and their olefin-carbon composite materials prepared in Example 3 are as follows: Figure 4 As shown, from Figure 4 As can be seen in the graphene, the surface of the graphene is evenly covered with filamentous strips, indicating that carbon nanotubes have successfully grown on the graphene surface. In addition, there are bright white spots at the top of the carbon nanotubes, proving that the metal catalyst is not fixed on the substrate, but is lifted up as the carbon nanotubes grow. Therefore, the use of metal catalysts with low carbon solubility allows carbon nanotubes to follow the top catalytic growth mode on the graphene surface. The yield of carbon nanotubes after multiple growth statistics is shown in Table 1 as 132.54g / g催化剂 . Example 4

[0043] In this embodiment, the additive is a reaction precursor for synthesizing carbon nitride, and the reaction precursor is specifically dicyandiamide.

[0044] S1: the carbon material is graphene, and the addition amount is 0.1 g; the additive is dicyandiamide, and the addition amount is 0.45 g; the catalyst is copper acetate monohydrate, and the addition amount is 0.0031 g; the remaining steps are consistent with Example 1.

[0045] S2: The specific operations are the same as those in Example 1.

[0046] The scanning electron microscope images of the carbon nanotubes and their olefin-carbon composite materials prepared in Example 4 are as follows: Figure 5 As shown, from Figure 5 The morphology of the material shows that carbon nanotubes have been successfully grown on the graphene surface. The growth of carbon nanotubes is relatively dense. At the same time, the ends of the carbon nanotubes also contain metal catalysts, which proves that they follow the top growth mode. The yield of carbon nanotubes after multiple growth statistics is shown in Table 1, which is 136.82g / g催化剂 . Example 5

[0047] In this embodiment, the additive is a reaction precursor for synthesizing carbon nitride, and the reaction precursor is specifically thiourea.

[0048] S1: the carbon material is graphene, and the addition amount is 0.1 g; the additive is thiourea, and the addition amount is 0.6 g; the catalyst is copper acetate monohydrate, and the addition amount is 0.0031 g; the remaining steps are consistent with Example 1.

[0049] S2: The specific operations are the same as those in Example 1.

[0050] The morphology of the sample obtained in this example was observed using a scanning electron microscope. Figure 6 As shown in Table 1, similar to Example 3 and Example 4, relatively dense carbon nanotubes grow on the surface of graphene. The yield of carbon nanotubes after multiple growth statistics is 139.74 g / cm2. g催化剂 . Example 6

[0051] In this embodiment, the additive is a reaction precursor for synthesizing carbon nitride, and the reaction precursor is specifically melamine.

[0052] S1: the carbon material is graphene, and the addition amount is 0.1 g; the additive is melamine, and the addition amount is 0.3 g; the catalyst is copper acetate monohydrate, and the addition amount is 0.0031 g; the remaining steps are consistent with Example 1.

[0053] S2: The specific operations are the same as those in Example 1.

[0054] The scanning electron microscope images of the carbon nanotubes and their olefin-carbon composite materials prepared in Example 6 are as follows: Figure 7 As shown in Table 1, carbon nanotubes can also be successfully grown on the graphene surface. The yield of carbon nanotubes after multiple growth statistics is 141.27g / g催化剂 . Example 7

[0055] In this embodiment, the additive is a reaction precursor for synthesizing carbon nitride, and the reaction precursor is specifically cyanuric acid.

[0056] S1: the carbon material is graphene, and the addition amount is 0.1 g; the additive is cyanuric acid, and the addition amount is 0.3 g; the catalyst is copper acetate monohydrate, and the addition amount is 0.0031 g; the remaining steps are consistent with Example 1.

[0057] S2: The specific operations are the same as those in Example 1.

[0058] The yield of carbon nanotubes after multiple growth statistics is shown in Table 1, which is 128.64 g / g催化剂 .

[0059] The scanning electron microscope images of the carbon nanotubes and their olefin-carbon composite materials prepared in Example 7 are as follows: Figure 8 As shown, carbon nanotubes were successfully grown on the graphene surface. Example 8

[0060] In this embodiment, the additive is a reaction precursor for synthesizing carbon nitride, and the reaction precursor is specifically cyanuric acid amide.

[0061] S1: the carbon material is graphene, and the addition amount is 0.1 g; the additive is cyanuric acid amide, and the addition amount is 0.4 g; the catalyst is copper acetate monohydrate, and the addition amount is 0.0031 g; the remaining steps are consistent with Example 1.

[0062] S2: The specific operations are the same as those in Example 1.

[0063] The yield of carbon nanotubes after multiple growth statistics is shown in Table 1, which is 136.56 g / g催化剂 .

[0064] The scanning electron microscope images of the carbon nanotubes and their olefin-carbon composite materials prepared in Example 8 are as follows: Figure 9 As shown, carbon nanotubes were successfully grown on the graphene surface.

[0065] Example 9 In this embodiment, the additive is a reaction precursor for synthesizing carbon nitride, and the reaction precursor is specifically cyanamide.

[0066] S1: the carbon material is graphene, and the addition amount is 0.1 g; the additive is cyanamide, and the addition amount is 0.45 g; the catalyst is copper acetate monohydrate, and the addition amount is 0.0031 g; the remaining steps are consistent with Example 1.

[0067] S2: The specific operations are the same as those in Example 1.

[0068] The yield of carbon nanotubes after multiple growth statistics is shown in Table 1, which is 127.87 g / g催化剂 .

[0069] The scanning electron microscope images of the carbon nanotubes and their olefin-carbon composite materials prepared in Example 9 are as follows: Figure 10 As shown, carbon nanotubes were successfully grown on the graphene surface.

[0070] Example 10 In this embodiment, the additive is a reaction precursor for synthesizing carbon nitride, and the reaction precursor is specifically meleamine.

[0071] S1: the carbon material is graphene, and the addition amount is 0.1 g; the additive is melamine, and the addition amount is 0.2 g; the catalyst is copper acetate monohydrate, and the addition amount is 0.0031 g; the remaining steps are consistent with Example 1.

[0072] S2: The specific operations are the same as those in Example 1.

[0073] The yield of carbon nanotubes after multiple growth statistics is shown in Table 1, which is 127.94 g / g催化剂 .

[0074] Example 10: The scanning electron microscope images of the carbon nanotubes and their olefin-carbon composite materials prepared are as follows: Figure 11 As shown, carbon nanotubes were successfully grown on the graphene surface.

[0075] Examples 1-10 respectively used g-C3N4 or different reaction precursors for synthesizing g-C3N4, and all of them can grow carbon nanotubes on the surface of graphene. The yield of growing carbon nanotubes using the reaction precursor for synthesizing g-C3N4 as an additive is generally higher than that of directly adding g-C3N4. The applicant believes that the precursor can achieve primary dispersion and anchoring of the metal catalyst during the polycondensation reaction, and then thermally polycondense into carbon nitride in situ to achieve secondary dispersion and anchoring. The catalyst dispersion and anchoring effect is the best. Therefore, by adding the reaction precursor, an olefin-carbon composite material with better growth effect and higher yield can be obtained.

[0076] Example 11 In this embodiment, the additive is a reaction precursor for synthesizing carbon nitride, and the reaction precursor is specifically melamine.

[0077] S1: the carbon material is graphene, and the addition amount is 0.1 g; the additive is melamine, and the addition amount is 0.3 g; the catalyst is copper chloride dihydrate, and the addition amount is 0.0027 g; the remaining steps are consistent with Example 1.

[0078] S2: The specific operations are the same as those in Example 1.

[0079] The scanning electron microscope images of the carbon nanotubes and their olefin-carbon composite materials prepared in Example 11 are as follows: Figure 12 As shown, from Figure 12 It can be clearly seen that carbon nanotubes grow evenly on graphene. A carbon nanotube-graphene composite structure material is formed. The yield of carbon nanotubes after multiple growth statistics is shown in Table 1, which is 141.75g / g催化剂 .

[0080] Example 12 In this embodiment, the additive is a reaction precursor for synthesizing carbon nitride, the reaction precursor is specifically melamine, and the catalyst is copper sulfate monohydrate.

[0081] S1: The carbonene material is graphene, and the addition amount is 0.1 g; the additive is melamine, and the addition amount is 0.3 g; the catalyst is copper sulfate monohydrate, and the addition amount is 0.0028 g; the carbonene material, the additive and the catalyst are mixed in water, and then the water is evaporated to dryness.

[0082] S2: The specific operations are the same as those in Example 1.

[0083] The scanning electron microscope images of the carbon nanotubes and their olefin-carbon composite materials prepared in Example 12 are as follows: Figure 13 As shown in Table 1, the carbon nanotubes grow relatively uniformly on the graphene, but the tube diameter is a little larger and the growth density is low. The yield of carbon nanotubes after multiple growth statistics is 96.76g / g催化剂 .

[0084] Example 13 In this embodiment, the additive is carbon nitride, and the catalyst is copper nitrate trihydrate.

[0085] S1: the carbon material is graphene, and the addition amount is 0.1 g; the additive is carbon nitride, and the addition amount is 0.1 g; the catalyst is copper nitrate trihydrate, and the addition amount is 0.0038 g; the remaining steps are consistent with Example 1.

[0086] S2: The specific operations are the same as those in Example 1.

[0087] The scanning electron microscope images of the carbon nanotubes and their olefin-carbon composite materials prepared in Example 13 are as follows: Figure 14 As shown in Table 1, the carbon nanotubes grow relatively evenly on the graphene with a moderate growth density. The yield of carbon nanotubes after multiple growth statistics is 124.68 g / g催化剂 .

[0088] Examples 1 and 11-13 each employed different metal catalysts, all containing copper ions. Copper (Cu) exhibits weak metal-carbon interactions and a solubility of only 0.04% atom at 1000°C. Nitrogen carbide or synthetic carbon nitride precursors act as organic ligands to bond with copper ions to form supramolecular compounds. The supramolecular structure allows copper ions to be evenly dispersed and anchored on the supramolecular framework, avoiding ion aggregation and the formation of large ion clusters. The yield of Example 12 was poor, which the applicant believes is due to the insolubility of copper sulfate in ethanol. Therefore, water was used for dispersion. However, when copper sulfate is dissolved in water, some copper ions undergo hydrolysis and complexation to form Cu(OH)2 precipitates, consuming some copper ions and leading to the formation of large copper particles during the subsequent heat treatment process, which in turn affects the yield and carbon nanotube growth morphology. Furthermore, due to the hydrophobicity of graphene, the ionic solution dissolved in water cannot infiltrate and adhere to the graphene surface, but instead aggregates into large clusters, further reducing the carbon nanotube yield.

[0089] Example 14 In this embodiment, the olefinic carbon material is flake graphite.

[0090] S1: the carbon material is flake graphite, added in an amount of 0.1 g; the additive is carbon nitride, added in an amount of 0.1 g; the catalyst is copper nitrate trihydrate, added in an amount of 0.0038 g; the remaining steps are consistent with Example 1.

[0091] S2: The specific operations are the same as those in Example 1.

[0092] Example 14: The scanning electron microscope images of the carbon nanotubes and their olefin-carbon composite materials prepared are as follows: Figure 15 As shown, carbon nanotubes were successfully grown on the graphene surface.

[0093] Example 15 In this embodiment, the olefinic carbon material is expanded graphite.

[0094] S1: the carbon material is expanded graphite, added in an amount of 0.1 g; the additive is dicyandiamide, added in an amount of 0.3 g; the catalyst is copper nitrate trihydrate, added in an amount of 0.0038 g; the remaining steps are consistent with Example 1.

[0095] S2: The specific operations are the same as those in Example 1.

[0096] Example 15: The scanning electron microscope images of the carbon nanotubes and their olefin-carbon composite materials prepared are as follows: Figure 16 As shown, carbon nanotubes were successfully grown on the graphene surface.

[0097] Example 16 In this embodiment, the olefinic carbon material is carbon black.

[0098] S1: the carbon material is carbon black, the addition amount is 0.1 g; the additive is melamine, the addition amount is 0.3 g; the catalyst is copper chloride dihydrate, the addition amount is 0.0027 g; the remaining steps are consistent with Example 1.

[0099] S2: The specific operations are the same as those in Example 1.

[0100] Example 16: The scanning electron microscope images of the carbon nanotubes and their olefin-carbon composite materials prepared are as follows: Figure 17 As shown, carbon nanotubes were successfully grown on the graphene surface.

[0101] Example 17 S1: the carbon material is carbon fiber, and the addition amount is 0.1 g; the additive is urea, and the addition amount is 0.6 g; the catalyst is copper nitrate trihydrate, and the addition amount is 0.0038 g; the remaining steps are consistent with Example 1.

[0102] S2: The specific operations are the same as those in Example 1.

[0103] Example 17: The scanning electron microscope images of the carbon nanotubes and their olefin-carbon composite materials prepared are as follows: Figure 18 As shown, carbon nanotubes were successfully grown on the graphene surface.

[0104] Example 1 and Examples 14-17 respectively use different olefinic carbon materials as growth substrates. Figure 15-18 The corresponding SEM clearly shows that carbon nanotubes are grown on different olefinic carbon materials, indicating the universality of the process we proposed for growing carbon nanotubes on olefinic carbon materials to prepare composite materials.

[0105] Comparative Example 1 A method for preparing carbon nanotubes and olefin-carbon composite materials thereof comprises the following steps: S1. Except that no additive is used in step S1, ie, 0.0027 g of catalyst copper acetate monohydrate is directly dissolved in an appropriate amount of ethanol and the graphene is stirred and mixed and dried, and the remaining steps and parameters are consistent with Example 2; S2 is the same as Example 2; Compared with Example 2, the difference between Comparative Example 1 and Example 2 is that no additives are added. Figure 19 The SEM image of Comparative Example 1 shows that there is almost no obvious carbon nanotube structure formed on the graphene. The catalyst is not protected by the carbon tube tip sheath and is in an exposed state. It is easily oxidized in the high temperature atmosphere. The yield of Comparative Example 1 is 11.141g / g催化剂 Due to the lack of carbon nitride as an additive, on the one hand, the catalyst loses its dispersion anchoring. During the heating growth process, the catalyst metal ions directly change step by step from ion clusters to large-sized nanoparticles, losing the ability to catalyze the growth of carbon tubes. On the other hand, due to the lack of additives, 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 a growth promoter to promote the migration and diffusion of carbon atoms on the catalyst surface, thereby improving the yield.

[0106] Comparative Example 2 A conventional method is used to support and disperse the catalyst using silicon dioxide as a dispersant for growth. The specific steps are as follows: S1: Weigh 0.1 g of 15 nm nano-silica particles and 0.0027 g of copper chloride dihydrate, disperse them in anhydrous ethanol, and stir the mixture with 0.1 g of graphene powder and dry them. S2: Fill the powder into a container and place it in a reaction device to grow according to the 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 the set program. The growth program is more specific as follows: introduce 300sccm of argon to raise the temperature to 700°C. After the temperature reaches 700°C, change the introduced gas to 5sccm of hydrogen and 400sccm of argon and raise the temperature to 850°C. After the temperature reaches 850°C, keep it warm for 5 minutes. After 5 minutes, introduce 20sccm of ethylene, 40sccm of hydrogen and 400sccm of argon and continue to keep warm and grow for 30 minutes. After the growth is completed, cool it naturally to room temperature and take it out. During this period, you only need to pass an appropriate amount of inert atmosphere for protection.

[0107] The scanning electron microscope images of the carbon nanotubes and their olefin-carbon composites prepared in Comparative Example 2 are as follows: Figure 20 As shown, it can be seen that the traditional strategy of using silica nanoparticles to load dispersed catalysts can also effectively grow carbon nanotubes. However, the carbon nanotubes grown by silica dispersion have a relatively messy morphology and a chaotic size distribution. Even with the increase in the amount of silica added, the dispersion performance has not been effectively improved, but the tube diameter has become thicker. This is attributed to the fact that with the increase in the amount of silica nanoparticles, the probability of their agglomeration becomes increasingly greater, causing the catalyst to agglomerate into large particles, thereby generating short tubes with large diameters. In addition, this traditional strategy also brings an obvious problem that the introduction of silica will become an impurity. After the growth is completed, a secondary treatment of pickling and etching is required to remove the silica in order to obtain the final graphene-carbon nanotube composite material, which is time-consuming and labor-intensive and has poor results.

[0108] In summary, the present invention innovatively introduces supramolecular construction and carbon nitride-loaded dispersed catalysts into the preparation process of carbon nanotubes and graphene-carbon nanotube composites. It can significantly improve the dispersion of the catalyst, and the nitrogen element thus introduced can effectively facilitate the anchoring of metal atoms on the surface of inert graphene. In addition, the nitrogen-containing active substances produced by the decomposition of carbon nitride during high-temperature growth can effectively improve the catalytic activity of the catalyst, promote the diffusion and migration of carbon atoms, and inhibit the production of amorphous carbon, thereby achieving high yield, high purity, no dispersed carrier residue, low catalyst residue, and the growth of carbon nanotubes and their graphene composites without the need for secondary pickling, fumigation and etching, and can achieve a certain degree of defect repair on the graphene substrate. The synthesis route provided by this scheme is simple and universal, and the raw materials are widely available, economical, and not limited to professional and specific synthesis production equipment, and can achieve large-scale industrialized mass production.

[0109] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0110] The carbon nanotube yields corresponding to Examples 1-17 and Comparative Examples 1-2 are shown in the following table: Table 1: Yield of carbon nanotubes after multiple growth statistics in various examples

[0111] The above description is a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and such modifications or substitutions are intended to be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A method for using a nitrogen-containing heterocyclic additive, characterized in that: The additive is g-C3N4 or a reaction precursor for synthesizing g-C3N4, and the additive is applied in the process of growing carbon nanotubes on the surface of an olefinic carbon material; during the growth process of the carbon nanotubes, the additive, the catalyst and the olefinic carbon material are mixed and added, and the additive uniformly disperses and anchors the catalyst, and after heat treatment, the carbon nanotubes are grown on the surface of the olefinic carbon material.

2. The method for using a nitrogen-containing heterocyclic additive according to claim 1, characterized in that: The catalyst enables the carbon nanotubes to grow on the surface of the olefinic carbon material in a tip growth mode.

3. The method for using a nitrogen-containing heterocyclic additive according to claim 1, characterized in that: The additive is g-C3N4.

4. The method for using a nitrogen-containing heterocyclic additive according to claim 1, characterized in that: The additive is a reaction precursor for synthesizing g-C3N4.

5. The method for using a nitrogen-containing heterocyclic additive according to claim 4, characterized in that: The reaction precursor is one or more of cyanamide, dicyandiamide, urea, thiourea, cyanuric acid, melamine, cyanuramide, cyanuric diamide or melem.

6. The method for using a nitrogen-containing heterocyclic additive according to claim 5, characterized in that: The olefinic carbon material has carbon atoms in the form of sp 2 Hybrid combination or sp 3 Materials formed by hybrid combination.

7. The method for using a nitrogen-containing heterocyclic additive according to claim 6, characterized in that: The olefinic carbon material has carbon atoms in the form of sp 2 Materials formed by hybrid combination.

8. A practical method for producing nitrogen-containing heterocyclic additives according to claim 7, characterized in that: The olefinic carbon material is graphene, carbon fiber, flake graphite, expanded graphite or worm graphite.

9. The method for using a nitrogen-containing heterocyclic additive according to claim 6, characterized in that: The olefinic carbon material is sp 3 Materials formed by hybrid combination.

10. The method for using a nitrogen-containing heterocyclic additive according to claim 9, characterized in that: The olefinic carbon material is any one of carbon black and Ketjen black.

11. The method for using a nitrogen-containing heterocyclic additive according to claim 1, characterized in that: The catalyst is a metal catalyst with low solubility for carbon. At 1000° C., the solubility of carbon in the catalyst is S≤0.1% atom.

12. The method for using a nitrogen-containing heterocyclic additive according to claim 10, characterized in that: The metal catalyst is a compound that can be dissolved in a solvent and contains free copper ions.

13. The method for using a nitrogen-containing heterocyclic additive according to claim 10, characterized in that: The metal catalyst includes any one or more of copper sulfate and its hydrate, copper nitrate and its hydrate, copper chloride and its hydrate, copper acetate and its hydrate, and metal organic complex copper acetylacetonate.

14. An olefin-carbon composite material, characterized in that: The olefin-carbon composite material is prepared by using the additives described in claims 1-13.

15. An application of an olefin-carbon composite material, characterized in that: The olefin-carbon composite material prepared according to claim 14 can be applied in the fields of energy, sensing, thermal management, catalysis, and mechanical reinforcement.

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