Carbon nanotube aerogel and preparation method thereof

Abstract

The invention discloses carbon nanotube aerogel and a preparation method thereof, and belongs to the field of carbon-based aerogel materials. According to the carbon nanotube aerogel, a three-dimensional porous network is mainly formed by a carbon nanotube with a high length-diameter ratio and glassy carbon consolidation nodes generated in situ; the glassy carbon is mainly distributed at lap joints of the carbon nanotubes. The method comprises the following steps: depositing carbon nanotubes by using a carbon source in the presence of a catalyst to form a three-dimensional aerogel network; the reaction temperature is 600-1200 DEG C, the feeding rate of the carbon source and the catalyst solution is controlled to be 0.1-10 mL / min, and the reaction time is 5-48 hours. The carbon nanotube aerogel prepared by the preparation method disclosed by the invention has high strength and high elastic deformation capability. The carbon nanotube network provides excellent reversible elasticity, and can realize large-amplitude reversible compression strain exceeding 50% or even 90%; and the glassy carbon consolidation node obviously improves the node bonding strength, so that the overall compression strength of the material can reach the MPa level, and the bottleneck that the existing carbon nanotube aerogel only has the kPa-level strength is broken through.

Description

Technical Field

[0001] This invention belongs to the field of carbon-based aerogel materials, specifically relating to a carbon nanotube aerogel based on glass carbon solidified nodes and its preparation method. Background Technology

[0002] Carbon aerogels are widely used in aerospace, energy storage, and electromagnetic protection due to their extremely low density, high porosity, and excellent thermal insulation properties. Currently, most mainstream carbon aerogel materials are derived from the carbonization of organic precursors such as phenolic resins, and the products are typically glassy carbon frameworks. These materials possess high modulus and strength, with compressive strengths reaching tens of megapascals and maintaining good mechanical stability even in high-temperature, oxygen-free environments. However, while glassy carbon exhibits high strength, it is inherently brittle, with an elastic strain range of only about 1% to 3%. The lack of effective microscopic energy dissipation mechanisms results in extremely poor toughness and a susceptibility to brittle fracture.

[0003] On the other hand, carbon aerogels, with carbon nanotubes as building blocks, exhibit excellent reversible deformation capabilities due to their ultra-high aspect ratio and flexibility, with reversible compressive strain exceeding 90% under external loads. However, the mechanical strength of these aerogels is generally low (typically less than 200 kPa), mainly due to insufficient bonding force between the overlapping nodes of carbon nanotubes. Under external loads, these nodes are prone to slippage and failure, resulting in insufficient overall load-bearing capacity. Existing carbon nanotube aerogels primarily rely on the physical entanglement and van der Waals force bonding between carbon nanotubes. Their nodes lack effective consolidation and reinforcement measures, leading to easy slippage and failure under external loads. The overall mechanical strength is only in the kPa range, making it difficult to meet the requirements for high load-bearing capacity and high stability under extreme service environments. Especially in aerospace thermal protection and high-performance structural applications, the limitations of insufficient strength in existing carbon nanotube aerogel materials are extremely prominent.

[0004] In summary, existing carbon aerogel materials generally face a dilemma: systems based on glassy carbon frameworks possess high strength but lack toughness; while systems based on carbon nanotubes, although exhibiting high deformability, suffer from insufficient strength, especially with the nodal slip problem remaining unresolved. Therefore, a new construction method is urgently needed that can significantly enhance mechanical strength through nodal consolidation while maintaining the large deformability of carbon nanotubes, thereby obtaining carbon aerogels that combine structural stability and high deformability. Summary of the Invention

[0005] This invention addresses the problems of insufficient node strength, overall mechanical properties only in the kPa range, and difficulty in meeting the requirements for high load-bearing capacity and high toughness in existing carbon nanotube aerogels or carbon nanotube sponges. It proposes a carbon nanotube aerogel based on glassy carbon-bonded nodes and its preparation method. This invention fully utilizes the high aspect ratio of carbon nanotubes to endow the aerogel with significant elastic deformation capabilities. Simultaneously, by introducing in-situ consolidation and reinforcement of glassy carbon at the carbon nanotube overlapping nodes, the strength and stability of the overlapping nodes are enhanced, fundamentally and effectively suppressing node slippage and interfacial failure. This achieves a dual improvement in mechanical strength and toughness, thereby enhancing the overall load-bearing capacity. This invention not only relies on the physical entanglement of carbon nanotubes but also forms a stable glassy carbon-bonded structure at the node locations through chemical deposition and structure induction, enabling the overall strength of the material to reach the MPa range, significantly superior to the mechanical level of traditional carbon nanotube aerogels.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A carbon nanotube aerogel is disclosed, comprising a three-dimensional porous network mainly composed of high aspect ratio carbon nanotubes and in-situ generated glassy carbon-bonded nodes. The glassy carbon is primarily distributed at the overlapping nodes of the carbon nanotubes, with a small amount distributed on the surface of the carbon nanotubes. It plays a role in fixing and strengthening the bonds between carbon nanotubes at the nanoscale, thereby effectively preventing node slippage under external loads. The aspect ratio of the carbon nanotubes is 500~100000.

[0008] A method for preparing the above-mentioned carbon nanotube aerogel, the method comprising: a process flow with chemical vapor deposition (CVD) as the core: carbon nanotubes are deposited using a carbon source under the condition of a catalyst to form a three-dimensional aerogel network; the reaction temperature is 600℃~1200℃, the feed rate of the carbon source and catalyst solution is controlled at 0.1~40 mL / min, and the reaction time is 5min~48h, so as to obtain carbon nanotube networks with different thicknesses and structures.

[0009] Carbon nanotube aerogels are synthesized via chemical vapor deposition (CVD). For example, ferrocene and 1,2-dichlorobenzene are used as catalyst and carbon source (i.e., the catalyst is dissolved in the carbon source). A solution of ferrocene and dichlorobenzene (0.06 g: 1 mL) is injected into the quartz tube of a CVD tubular furnace using a precision injection pump. The preheating zone is set to 200 °C, where the carbon source and catalyst are vaporized and then carried into the reaction zone by carrier gases Ar / H2 (980 and 420 mL / min, respectively), with the reaction zone temperature set to 860 °C. The vapor phases of ferrocene and dichlorobenzene form short, open-cell carbon nanotube structures in the reaction zone. Under the flow of the carrier gas, these short carbon nanotubes randomly deposit on a substrate (quartz plate) in the reaction zone and continue to grow after deposition. Subsequently, short carbon nanotubes formed in the vapor phase deposit on top of the earlier-grown carbon nanotubes. As the reaction time increases, these carbon nanotubes deposited on the quartz plate interweave to form an aerogel structure.

[0010] Furthermore, the carbon source is a carbon-containing organic compound.

[0011] Furthermore, the carbon-containing organic compound is one or more of acetylene, methane, benzene, dichlorobenzene, and toluene.

[0012] Furthermore, the catalyst is one or more of an iron-based catalyst, a cobalt-based catalyst, or a nickel-based catalyst.

[0013] Furthermore, the molar ratio of the carbon source to the catalyst is 10~1000:1 to accommodate different deposition rates and structural requirements.

[0014] Furthermore, the ratio of the catalyst to the carbon source is 0.01~1 g / mL.

[0015] Furthermore, the reaction temperature is 750℃~950℃.

[0016] Furthermore, the feed rate is 0.5 ~ 30 mL / min, which can be adjusted according to the capacity of the tubular furnace.

[0017] The advantages of this invention over the prior art are as follows:

[0018] This invention achieves amorphous carbon deposition at the junctions of carbon nanotubes by comprehensively controlling the carbon source concentration, catalyst ratio, feed rate, and deposition time during the deposition process. Under the action of catalysts such as iron, cobalt, or nickel, and with the help of the lattice-induced effect of the carbon nanotubes themselves, the deposited amorphous carbon undergoes further structural evolution, gradually transforming from a disordered state to a glassy carbon state, thereby forming a stable and dense solidified structure at the junctions.

[0019] The carbon nanotube aerogel prepared by this invention possesses both high strength and high elastic deformation capability. The carbon nanotube network provides excellent reversible elasticity, enabling large-amplitude reversible compressive strain exceeding 50% or even 90%; the glassy carbon solidified nodes significantly improve the node bonding strength, allowing the overall compressive strength of the material to reach the MPa level, thus breaking through the bottleneck of existing carbon nanotube aerogels with strength only at the kPa level.

[0020] In summary, this invention solves the technical problems of insufficient node strength and low overall strength in existing carbon nanotube aerogels by introducing glassy carbon consolidation structures at the overlapping nodes, achieving a leap from the kPa level to the MPa level while maintaining the material's high toughness and large deformation capacity. This innovative construction method not only reveals the decisive role of node reinforcement in the mechanical properties of carbon nanotube aerogels at the scientific research level, but also provides a novel solution for the engineering application of this type of material in extreme environments.

[0021] This invention effectively solves the problems of insufficient node strength and limited overall load-bearing capacity in existing carbon nanotube foams and carbon nanotube aerogels by introducing an in-situ solidified structure of glassy carbon at the lap joints of carbon nanotube aerogels. Unlike traditional methods that rely on the physical entanglement of carbon nanotubes and van der Waals forces to maintain the network, this invention, through controlling the carbon source concentration, catalyst ratio, and deposition conditions during the deposition process, preferentially deposits amorphous carbon at the carbon nanotube intersections. Under the induction of the carbon nanotube lattice and the action of the catalyst, it gradually transforms into a glassy carbon structure, thereby forming a stable and dense solidified interface at the node locations. This construction method significantly improves the node bonding strength, allowing the intrinsic mechanical properties of carbon nanotubes to be fully utilized. The overall compressive strength of the material is increased from the kPa level of traditional carbon nanotube foams to the MPa level, achieving a significant breakthrough. Attached Figure Description

[0022] Figure 1 SEM image of glassy carbon solidified at the lap joint of carbon nanotubes.

[0023] Figure 2 The diagram shows the microscopic characterization of the nodes, which indicates that the structure is a glassy carbon structure containing both ordered and disordered parts.

[0024] Figure 3 Image of a carbon nanotube aerogel;

[0025] Figure 4 This is a curve showing the compressive stress-strain of carbon nanotube aerogel. Detailed Implementation

[0026] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0027] Glassy carbon is a type of amorphous carbon material. Its structure combines some graphitization and amorphous characteristics, exhibiting high strength and high modulus. Unlike graphite, glassy carbon does not have a distinct layered, slippery structure, but rather presents a three-dimensional cross-linked network, thus exhibiting high mechanical strength. Carbon nanotube aerogels are three-dimensional porous network materials formed by the self-assembly of carbon nanotubes through van der Waals forces and entanglement. This material possesses extremely low density, high porosity, and excellent elastic deformation capacity. Factors affecting the mechanical properties of carbon nanotube aerogels: The mechanical properties of carbon nanotube aerogels are mainly determined by two aspects: firstly, the intrinsic mechanical properties of individual carbon nanotubes; and secondly, the strength and stability of the lap joints in the carbon nanotube lap network. Node slippage, failure, or insufficient interfacial bonding are often the main reasons for insufficient overall aerogel strength. The technical solution proposed in this invention addresses the node problem in carbon nanotube aerogels by achieving node reinforcement and stabilization through glassy carbon consolidation.

[0028] Example 1: Preparation of glassy carbon nanotube aerogels with solidified nodes using chemical vapor deposition (CVD). Specifically, ferrocene was dissolved in dichlorobenzene to obtain a solution with a concentration of 0.06 g / mL. After being magnetically stirred until homogeneous, the solution was continuously injected into a high-temperature quartz tube reactor at a rate of 2 mL / min using a syringe pump. The reactor temperature was controlled at 900 °C, and argon (500 mL / min) and hydrogen (100 mL / min) were introduced as the reaction atmosphere. Under these conditions, the carbon source underwent pyrolysis and deposition to form a three-dimensional carbon nanotube network structure, with preferential deposition of amorphous carbon at the network intersections. Figure 1 As the reaction time was extended to 12 hours, under the induction of the iron catalyst and the carbon nanotube lattice, the deposited amorphous carbon gradually transformed into a glassy carbon structure. Figure 2 This process forms a dense, solidified layer in the node region. After cooling, the resulting bulk material is collected and vacuum-dried to obtain the target carbon nanotube aerogel. Testing showed that the carbon nanotube aerogel prepared in this embodiment (…) Figure 3 The compressive strength reaches 13.7 MPa. Figure 4 The pressure is much higher than that of similar carbon nanotube aerogels (generally less than 200 kPa).

[0029] Example 2: Preparation of glassy carbon nanotube aerogels with solidified nodes using chemical vapor deposition (CVD). Specifically, ferrocene was dissolved in dichlorobenzene to obtain a solution with a concentration of 0.06 g / mL. After being magnetically stirred until homogeneous, the solution was continuously injected into a high-temperature quartz tube reactor at a rate of 1 mL / min using a syringe pump. The reactor temperature was controlled at 900 °C, and argon (500 mL / min) and hydrogen (100 mL / min) were introduced as the reaction atmosphere. Under these conditions, the carbon source underwent pyrolysis and deposition to form a three-dimensional carbon nanotube network structure, with preferential deposition of amorphous carbon at the network intersection nodes. As the reaction time was extended to 8 hours, under the induction of the iron catalyst and the carbon nanotube lattice, the deposited amorphous carbon gradually transformed into a glassy carbon structure, thereby forming a uniform and dense solidified layer in the node region.

[0030] After cooling, the resulting bulk material was collected and vacuum dried at 80 °C for 12 hours to obtain the target carbon nanotube aerogel. The obtained sample appeared as a black bulk material with a uniform pore structure and a continuous carbon nanotube network. The compressive strength of the carbon nanotube aerogel prepared in this example reached 8.2 MPa, which is lower than 13.7 MPa in Example 1, but still much higher than that of carbon nanotube aerogels without node consolidation (generally less than 200 kPa).

[0031] The results indicate that the feed rate and reaction time have a significant impact on the amount of glassy carbon deposited at the nodes and the structural evolution. Reducing the feed rate and shortening the deposition time leads to a decrease in the degree of node consolidation, thereby reducing the overall compressive strength. However, the material still maintains good structural integrity and high strength characteristics, verifying the strengthening mechanism of the glassy carbon consolidated nodes in this invention.

[0032] In Example 3, the deposition and structural evolution of nodal glassy carbon were further regulated by changing the carbon source composition and reaction conditions. Specifically, ferrocene was dissolved in a mixed solvent of xylene and dichlorobenzene (volume ratio 1:3) to prepare a catalyst solution with a concentration of 0.04 g / mL. After being magnetically stirred until homogeneous, the solution was continuously injected into a high-temperature quartz tube reactor at a rate of 1.5 mL / min using a syringe pump. The reactor temperature was controlled at 950 °C, and argon (400 mL / min) and hydrogen (200 mL / min) were introduced as the reaction atmosphere. Under these conditions, the aromatic mixed carbon source underwent pyrolysis, and the generated carbon was deposited under catalyst induction to form a continuous three-dimensional carbon nanotube network. Furthermore, because the aromatic carbon source more readily generates amorphous carbon, it exhibited a significant preferential deposition phenomenon at the network's intersection nodes. As the reaction time is extended to 10 hours, under the localized induction effect of the iron catalyst and the carbon nanotube lattice, the deposited amorphous carbon gradually undergoes structural rearrangement, transforming from a disordered amorphous phase to a glassy carbon phase with a short-range ordered structure, resulting in the formation of a uniform and dense solidified layer at the node positions.

[0033] After the reaction, the quartz tube was naturally cooled to room temperature, and the resulting bulk sample was collected and vacuum dried at 80 °C for 12 hours to obtain a carbon nanotube aerogel with a complete appearance and uniform structure. Mechanical testing of the obtained sample showed that the compressive strength of this carbon nanotube aerogel reached 10.5 MPa, significantly higher than that of traditional carbon nanotube aerogels without consolidated nodes (generally less than 200 kPa), and higher than Example 2 (8.2 MPa), but slightly lower than Example 1 (13.7 MPa) which had a longer deposition time and higher feed rate. This result indicates that by controlling the carbon source composition, hydrogen ratio, and reaction temperature, the amount and density of glassy carbon generated can be effectively controlled, thereby achieving a controllable enhancement of the node consolidation effect.

[0034] In Example 4, the universality of the "glassy carbon solidified node" strategy in this invention was further verified by changing the carbon source type and using a nickel-based catalyst. Specifically, nickel nitrate hexahydrate was dissolved in a mixed solvent of xylene and dichlorobenzene (volume ratio 1:4) to prepare a catalyst solution with a concentration of 0.02 g / mL. After complete dissolution by magnetic stirring, the solution was continuously injected into a preheated high-temperature quartz tube reactor at a rate of 0.8 mL / min using a syringe pump. The reactor temperature was set to 850°C, and argon (600 mL / min) was introduced as a carrier gas, hydrogen (50 mL / min) as a reducing auxiliary atmosphere, and methane (80 mL / min) as a gaseous carbon source.

[0035] In this reaction environment, methane undergoes cracking at high temperature and with the aid of a nickel-based catalyst. The resulting carbon atoms continuously grow epitaxially along the catalyst particles to form carbon nanotubes, gradually constructing a three-dimensional porous aerogel network. Compared to liquid carbon sources, methane cracking is more likely to produce slightly supersaturated carbon deposition, resulting in a significant enrichment trend of amorphous carbon at the carbon nanotube intersection nodes. During the 6-hour deposition process, the continuously deposited amorphous carbon at the nodes gradually transforms from a disordered structure to a short-range ordered structure of glassy carbon under the dual induction of the nickel catalyst and the carbon nanotube lattice, thus forming a continuous and stable solidified layer in the node region.

[0036] After the reaction, the system was naturally cooled to room temperature, and the resulting bulk aerogel sample was collected and vacuum dried at 80 °C for 10 hours to remove residual gas and solvent adsorbed in the pores. The resulting sample was a lightweight black bulk with a uniformly distributed three-dimensional carbon nanotube network structure and dense consolidation features at the nodes. Compressive strength tests using a universal testing machine showed that the carbon nanotube aerogel obtained in this example achieved a compressive strength of 6.4 MPa. Compared to Example 1 (13.7 MPa) and Example 3 (10.5 MPa), this strength is slightly lower, but significantly higher than that of traditional carbon nanotube aerogels without consolidation nodes (typically less than 200 kPa). This fully demonstrates that glassy carbon consolidation nodes can still be effectively formed under a methane gas source and nickel-based catalytic system, but the degree of node consolidation is slightly weaker than in a liquid carbon source system due to limitations in deposition rate and reaction time. This embodiment further illustrates that the nodal glass carbon consolidation strategy of the present invention has good process compatibility. It is applicable not only to aromatic liquid carbon source systems but also to gaseous carbon source systems. Different degrees of nodal enhancement effects can be achieved by adjusting the carbon source type, catalyst system, and deposition rate, thereby obtaining carbon nanotube aerogel materials with different strength levels.

Claims

1. A carbon nanotube aerogel, characterized by: The carbon nanotube aerogel is mainly composed of high aspect ratio carbon nanotubes and in-situ generated glass carbon consolidation nodes to form a three-dimensional porous network; and the glass carbon is mainly distributed at the overlapping nodes of the carbon nanotubes.

2. A method of making the carbon nanotube aerogel of claim 1, characterized by: The method is: carbon nanotubes are deposited under the condition of a catalyst by using a carbon source to form a three-dimensional aerogel network; the reaction temperature is 600-1200 DEG C, the feeding rate of the carbon source and the catalyst solution is controlled to be 0.1-40 mL / min, and the reaction time is 5 min-48 h.

3. The method for preparing a carbon nanotube aerogel according to claim 2, characterized in that: The carbon source is a carbon-containing organic compound.

4. The method for preparing a carbon nanotube aerogel according to claim 3, characterized in that: The carbon-containing organic compound is one or more of acetylene, methane, benzene, dichlorobenzene and toluene.

5. The method for preparing a carbon nanotube aerogel according to claim 2, characterized in that: The catalyst is one or more of an iron-based catalyst, a cobalt-based catalyst or a nickel-based catalyst.

6. The method for preparing a carbon nanotube aerogel according to claim 2, characterized in that: The molar ratio of the carbon source to the catalyst is 10-1000:

1.

7. The method for preparing carbon nanotube aerogel according to claim 2, characterized in that: The ratio of the catalyst to the carbon source is 0.01-1 g / mL.

8. The method for preparing a carbon nanotube aerogel according to claim 2, characterized in that: The reaction temperature is 750-950 DEG C.

9. The method for preparing a carbon nanotube aerogel according to claim 2, characterized in that: The feeding rate is 0.5-30 mL / min.

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