Preparation method of few-walled carbon nanotubes
By leveraging the synergistic effect of iron-cobalt-nickel catalysts and nitrogen-containing promoters, combined with ultrasonic cleaning and high-temperature calcination, the growth defect problem in the preparation of oligowalled carbon nanotubes was solved, achieving efficient and controllable synthesis of oligowalled carbon nanotubes and improving the uniformity and quality of the products.
Patent Information
- Application Number
- CN202511077931.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-01
- Publication Date
- 2025-11-04
AI Technical Summary
Existing technologies for the large-scale preparation of oligowalled carbon nanotubes suffer from problems such as uneven catalyst particle size, excessively wide layer distribution, insufficient substrate compatibility, and high-temperature mismatch, leading to growth defects and product contamination.
By employing an iron-cobalt-nickel catalyst system combined with a nitrogen-containing promoter, and by using ultrasonic cleaning and high-temperature calcination to treat the substrate, the surface hydroxyl density is controlled. A controllable oxide layer is formed through hydrogen flow rate and slow cooling process, which refines the catalyst particles and inhibits the formation of amorphous carbon, thus achieving the efficient and controllable synthesis of oligowalled carbon nanotubes.
It effectively removes contaminants from the substrate surface, enhances the thermal stability of the substrate, improves the adhesion of the catalyst, significantly reduces the structural defect rate, and achieves efficient and controllable synthesis of oligowalled carbon nanotubes with improved tube diameter uniformity.
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Figure CN120887409A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of carbon nanotubes, and particularly relates to a preparation method of few-walled carbon nanotubes. BACKGROUND
[0002] Few-walled carbon nanotubes (FWCNTs, 2-5 layers) have great potential in the fields of nano-electronic devices, composite materials and energy storage due to their unique electrical, mechanical and thermal properties. However, there are still three major technical bottlenecks in the large-scale preparation of few-walled carbon nanotubes. The existing chemical vapor deposition method generally has the problem of wide layer distribution: the catalyst particle size is uneven in the fixed substrate method, resulting in uncontrollable tube diameter and layer number, and the metal catalyst is easy to alloy with the silicon-based substrate at high temperature, damaging the growth interface.
[0003] The sublimation rate of ferrocene in the process of the floating catalyst method fluctuates, causing the concentration of the gas-phase catalyst to drift, resulting in the mixing of single-walled, few-walled and multi-walled carbon nanotubes in the product. At the same time, the existing substrate has poor adaptability and is easy to mismatch at high temperature, and the difference in the thermal expansion coefficient of the metal foil during the cooling stage of the chemical vapor deposition method causes the nanotube film to peel off. SUMMARY
[0004] Therefore, the application provides a preparation method of few-walled carbon nanotubes to solve the above problems.
[0005] To achieve the above purpose, the application provides the following technical scheme: A preparation method of few-walled carbon nanotubes, comprising the following steps: (1) Selecting a substrate, placing the substrate in an organic solvent, ultrasonic cleaning, blowing dry with a nitrogen gun, placing the dried substrate with the front face upwards in a crucible and in a muffle furnace, calcining at 300-400 DEG C for 2-4 h, cooling to 100-200 DEG C, introducing air and naturally cooling to room temperature to obtain a pretreated substrate; (2) Placing the catalyst precursor and the promoter in the pretreated substrate and placing them in the constant temperature zone of a tube furnace, introducing argon to replace the air; (3) Introducing a mixed gas into the constant temperature zone of the tube furnace, preheating the carbon source gas and introducing it into the tube furnace, maintaining the temperature at 750-950 DEG C for 40-60 min, and stopping the delivery of the carbon source gas; (4) Continuing to introduce the mixed gas into the constant temperature zone of the tube furnace for 5-10 min, cooling to 200-300 DEG C, introducing argon and cooling to room temperature, taking out the substrate, and collecting the crude product; (5) the crude product is treated by air oxidation at a temperature of 300-400℃ for 1-2h, then washed by hydrochloric acid in a water bath at 60-80℃ for 2-6h, washed by deionized water until neutral, and dried to obtain oligowall carbon nanotubes.
[0006] Further, the substrate in the step (1) comprises at least one of a single crystal silicon wafer, a quartz wafer and an alumina ceramic wafer, and the organic solvent comprises at least one of ethanol, acetone and isopropyl ketone.
[0007] Further, the ultrasonic cleaning in the step (1) is performed at a frequency of 80-100kHz and a power of 400-800W for 20-30min.
[0008] Further, the catalyst precursor in the step (2) comprises at least one of ferrocene, acetylacetone iron, ferric nitrate, cobalt nitrate and nickel nitrate; and the promoter comprises at least one of pyrimidine, pyridine, pyrazine, quinoline, acetonitrile, propylene cyanide, triethylamine, cyclohexylamine, dimethylformamide, melamine and aniline.
[0009] Further, the argon gas is introduced at a flow rate of 200-500sccm for 10-20min.
[0010] Further, the mixed gas in the step (3) is argon and hydrogen, wherein the hydrogen accounts for 20%-50%, and the mixed gas is introduced at a flow rate of 500-1500sccm.
[0011] Further, the temperature increasing rate in the step (3) is 5-10℃ / min.
[0012] Further, the carbon source gas in the step (3) is at least one of ethylene, acetylene and propylene, the preheating temperature of the carbon source gas is 400-500℃, and the flow rate is 100-300sccm.
[0013] Further, the mixed gas in the step (4) is purged at a flow rate of 200-500sccm, the temperature decreasing rate is 3-5℃ / min, and the argon gas is introduced at a flow rate of 200-500sccm.
[0014] Further, the hydrochloric acid in the step (4) has a mass fraction of 8%-10%, and the oligowall carbon nanotubes have a tube diameter of 3-8nm.
[0015] Compared with the prior art, the present application has the following beneficial effects: The present application adopts an iron-cobalt-nickel catalyst system matched with a nitrogen-containing promoter, and processes a substrate to prepare oligowall carbon nanotubes. Ultrasonic cleaning can effectively remove organic matter and particulate pollutants on the surface of the substrate, avoiding growth defects. High-temperature calcination further cleans the surface and enhances the thermal stability of the substrate, providing a uniform interface for catalyst loading. During the cooling process, air can be introduced to form a controllable oxidation layer, which can effectively improve the adhesion of the catalyst. The surface hydroxyl density is controlled by adjusting the pretreatment temperature on the substrate.
[0016] The catalyst precursor decomposes into nanoparticles at high temperature, and the nitrogen-containing promoter is used to replace sulfide, while hydrogen flow is actively inhibited. The nitrogen-containing promoter can effectively inhibit amorphous carbon and promote the formation of van der Waals forces between oligowall carbon nanotubes. Slow cooling after the reaction significantly reduces the structural defect rate of oligowall carbon nanotubes. Through synergistic regulation of catalyst particle size and promoter, the nitrogen-containing promoter refines the catalyst particles, directly reduces the tube diameter of oligowall carbon nanotubes, controls the carbon diffusion rate through the hydrogen-carbon ratio, and inhibits multi-layer growth, thereby realizing efficient and controllable synthesis of oligowall carbon nanotubes. BRIEF DESCRIPTION OF DRAWINGS
[0017] The present application will be further described below in conjunction with the drawings and examples.
[0018] Figure 1 The transmission electron microscope characterization of the oligowall carbon nanotubes prepared for Example 1 of the present application is intended; Figure 2 The transmission electron microscope characterization of the oligowall carbon nanotubes prepared for Example 2 of the present application is intended; Figure 3 The transmission electron microscope characterization of the oligowall carbon nanotubes prepared for Example 3 of the present application is intended. DETAILED DESCRIPTION
[0019] The technical solutions in the embodiments of the present application will be described below in a clear and complete manner. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.
[0020] In the description of the present application, it should be understood that the terms "open hole", "upper", "lower", "thickness", "top", "middle", "length", "inner", "periphery" and the like indicate the orientation or positional relationship, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the components or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.
[0021] The present application provides a preparation method of oligowall carbon nanotubes, comprising the following steps: (1) selecting a substrate, placing the substrate in an organic solvent, ultrasonic cleaning for 20-30 min under the condition of frequency 80-100 kHz, power 400-800 W, blowing dry with nitrogen gun, placing the dried substrate with the front side up in a crucible and in a muffle furnace, calcining for 2-4 h by increasing the temperature to 300-400 ℃, decreasing the temperature to 100-200 ℃, passing in air and naturally cooling to room temperature, obtaining a pretreated substrate; (2) placing the catalyst precursor and the promoter into the pretreated substrate, and placing in the constant temperature zone of a tube furnace, passing in argon at a flow rate of 200-500 seem for 10-20 min to replace air; (3) passing in argon-hydrogen mixed gas into the constant temperature zone of the tube furnace at a flow rate of 500-1500 seem, wherein the hydrogen accounts for 20%-50%, increasing the temperature to 750-950 ℃ at a temperature increasing rate of 5-10 ℃ / min, preheating the carbon source gas to 400-500 ℃ and then passing in the tube furnace at a flow rate of 100-300 seem, maintaining the reaction for 40-60 min at the temperature of 750-950 ℃, and stopping the delivery of the carbon source gas; (4) continuing to pass in argon-hydrogen mixed gas into the constant temperature zone of the tube furnace at a flow rate of 200-500 seem for 5-10 min, decreasing the temperature to 200-300 ℃ at a temperature decreasing rate of 3-5 ℃ / min, then passing in argon at a flow rate of 200-500 seem and cooling to room temperature, taking out the substrate, and collecting the crude product; (5) air-oxidizing the crude product at a temperature of 300-400 ℃ for 1-2 h, then washing with hydrochloric acid with a mass fraction of 8%-10% under the condition of a water bath at 60-80 ℃ for 2-6 h, washing with deionized water until neutral, drying, and obtaining oligowall carbon nanotubes with a tube diameter of 3-8 nm.
[0022] The substrate includes at least one of a single crystal silicon wafer, a quartz wafer, and an alumina ceramic wafer; the organic solvent includes at least one of ethanol, acetone, and isopropyl ketone; the catalyst precursor includes at least one of ferrocene, acetylacetone iron, iron nitrate, cobalt nitrate, and nickel nitrate; the promoter includes at least one of pyrimidine, pyridine, pyrazine, quinoline, acetonitrile, propylene cyanide, triethylamine, cyclohexylamine, dimethylformamide, melamine, and aniline; and the carbon source gas is at least one of ethylene, acetylene, and propylene.
[0023] The technical solutions provided by the present application are described in detail below in conjunction with the examples, but they should not be understood as limiting the scope of protection of the present application.
[0024] Example 1 The preparation method of the oligowall carbon nanotubes of the present example includes the following steps: (1) Select a single crystal silicon wafer, place the single crystal silicon wafer in ethanol, ultrasonically clean it for 20 minutes at a frequency of 80kHz and a power of 400W, blow it dry with a nitrogen gun, place the dried single crystal silicon wafer neatly in a crucible with the front side facing up and place it in a muffle furnace, heat it to 300℃ and calcine it for 2 hours, cool it down to 100℃, introduce air and cool it naturally to room temperature to obtain a pretreated single crystal silicon wafer; (2) Place ferrocene and pyrimidine into a pretreated single crystal silicon wafer and place it in the constant temperature zone of a tube furnace. Introduce argon gas at a flow rate of 200 sccm and maintain for 10 min to replace the air. (3) Introduce an argon-hydrogen mixture into the constant temperature zone of the tubular furnace at a flow rate of 500 sccm, with hydrogen accounting for 20%, and heat it to 750°C at a heating rate of 5°C / min. After preheating the ethylene to 400°C, introduce it into the tubular furnace at a flow rate of 100 sccm. Maintain the reaction at 750°C for 40 min, and then stop supplying ethylene. (4) Continue to purge the tube furnace with argon-hydrogen mixed gas at a flow rate of 200 sccm for 5 min, cool it down to 200℃ at a cooling rate of 3℃ / min, then purge with argon at a flow rate of 200 sccm and cool it to room temperature, take out the single crystal silicon wafer and collect the crude product. (5) The crude product was oxidized in air at 300°C for 1 hour, then washed with 8% hydrochloric acid in a water bath at 60°C for 2 hours, washed with deionized water until neutral, and dried to obtain oligowalled carbon nanotubes.
[0025] The generated oligowalled carbon nanotube powder was subjected to transmission electron microscopy (TEM) to characterize the diameter of the product. The diameters of the product were 5.789 nm and 6.249 nm. The test results are shown in [Figure number missing]. Figure 1 .
[0026] Example 2 The method for preparing oligowalled carbon nanotubes in this embodiment includes the following steps: (1) Select a quartz sheet, place the quartz sheet in acetone, ultrasonically clean it for 25 minutes at a frequency of 90kHz and a power of 600W, dry it with a nitrogen gun, place the dried quartz sheet neatly in a crucible with the front side facing up and place it in a muffle furnace, heat it to 350℃ and calcine it for 3 hours, cool it down to 150℃, introduce air and cool it naturally to room temperature to obtain a pretreated quartz sheet. (2) Place acetylacetone iron and acetonitrile into a pretreated quartz plate and place it in the constant temperature zone of a tube furnace. Introduce argon gas at a flow rate of 350 sccm and maintain for 15 min to replace the air. (3) argon-hydrogen mixed gas with hydrogen accounting for 35% at a flow rate of 1000 seem is introduced into the constant temperature zone of the tube furnace, the temperature is raised to 850°C at a rate of 8°C / min, acetylene is preheated to 450°C and introduced into the tube furnace at a flow rate of 200 seem, the temperature is maintained at 850°C for 50 min, and the acetylene is stopped; (4) argon-hydrogen mixed gas is continuously introduced into the constant temperature zone of the tube furnace at a flow rate of 350 seem for 7 min, the temperature is lowered to 250°C at a rate of 4°C / min, argon is introduced at a flow rate of 350 seem, and the temperature is lowered to room temperature, the quartz sheet is taken out, and the crude product is collected; (5) the crude product is air-oxidized at a temperature of 350°C for 1.5 h, then washed with 9% hydrochloric acid at a water bath temperature of 70°C for 4 h, washed with deionized water until neutral, dried, and obtained oligowall carbon nanotubes.
[0027] The generated oligowall carbon nanotube powder is subjected to transmission electron microscopy (TEM), and the diameter of the product is characterized by TEM, the diameter of the product is 6.496 nm and 7.864 nm, and the test results are shown in Figure 2 .
[0028] Example 3 The preparation method of oligowall carbon nanotubes in this example includes the following steps: (1) select an alumina ceramic sheet, clean the alumina ceramic sheet in isopropyl alcohol under the condition of a frequency of 100 kHz and a power of 800 W for 30 min, dry the alumina ceramic sheet with a nitrogen gun, place the dried alumina ceramic sheet with the front side facing up in a crucible and in a muffle furnace, heat to 400°C and calcine for 4 h, lower the temperature to 200°C, introduce air and cool to room temperature naturally, and obtain a pretreated alumina ceramic sheet; (2) put iron nitrate and triethylamine into the pretreated alumina ceramic sheet, and place it in the constant temperature zone of the tube furnace, introduce argon at a flow rate of 500 seem for 20 min to displace air; (3) argon-hydrogen propylene with hydrogen accounting for 50% at a flow rate of 1500 seem is introduced into the constant temperature zone of the tube furnace, the temperature is raised to 950°C at a rate of 10°C / min, the carbon source gas is preheated to 500°C and introduced into the tube furnace at a flow rate of 300 seem, the temperature is maintained at 950°C for 60 min, and the carbon source gas is stopped; (4) continue to introduce propylene at a flow rate of 500 seem into the constant temperature zone of the tube furnace for 10 min, lower the temperature to 300°C at a rate of 5°C / min, introduce argon at a flow rate of 500 seem and cool to room temperature, take out the alumina ceramic sheet, and collect the crude product; (5) The crude product is treated with air oxidation at a temperature of 400 DEG C for 2h, then washed with 10% hydrochloric acid at 80 DEG C for 6h, washed with deionized water until neutral, dried, to obtain the few-walled carbon nanotubes.
[0029] The few-walled carbon nanotube powder is subjected to transmission electron microscopy (TEM), and the diameter of the product is characterized by TEM, and the diameter of the product is 6.997nm, and the test results are shown in Figure 3 .
[0030] As can be seen from examples 1-3, the preparation method of the few-walled carbon nanotubes of the present application uses an iron-cobalt-nickel catalyst system in combination with a nitrogen-containing promoter, and the substrate is treated, to prepare the few-walled carbon nanotubes. Ultrasonic cleaning can effectively remove organic matter and particulate contaminants on the surface of the substrate, avoiding growth defects. High-temperature calcination further cleans the surface and enhances the thermal stability of the substrate, providing a uniform interface for catalyst loading. The air inlet during the cooling process can form a controllable oxidation layer, which can effectively improve the adhesion of the catalyst. The surface hydroxyl density is controlled by adjusting the pretreatment temperature on the substrate.
[0031] The catalyst precursor is decomposed into nanoparticles at high temperature, and the nitrogen-containing promoter is used to replace sulfide, while hydrogen flow is actively inhibited. The nitrogen-containing promoter can effectively inhibit amorphous carbon and promote the formation of van der Waals forces between the layers of the few-walled carbon nanotubes. Slow cooling after the reaction significantly reduces the structural defect rate of the few-walled carbon nanotubes. Through synergistic regulation of catalyst particle size and promoter, the nitrogen-containing promoter refines the catalyst particles, directly reducing the tube diameter of the few-walled carbon nanotubes, and the hydrogen-carbon ratio controls the carbon diffusion rate, inhibiting multi-layer growth, thereby achieving efficient and controllable synthesis of the few-walled carbon nanotubes.
[0032] In the description of the present specification, the description of the terms "one embodiment", "example", "specific example" and the like means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.
[0033] The above shows and describes the basic principles, main features and advantages of the present application. It should be understood by those skilled in the art that the present application is not limited by the above examples, and the above examples and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application.
Claims
1. A method for preparing oligowalled carbon nanotubes, characterized in that, Includes the following steps: (1) Select a substrate, place the substrate in an organic solvent, clean it with ultrasonic waves, dry it with a nitrogen gun, place the dried substrate face up neatly in a crucible and place it in a muffle furnace, heat it to 300~400℃ and calcine for 2~4 hours, cool it down to 100~200℃, introduce air and cool it naturally to room temperature to obtain a pretreated substrate. (2) Place the catalyst precursor and accelerator into the pretreated substrate and place it in the constant temperature zone of the tube furnace, and purge the air with argon gas. (3) Introduce mixed gas into the constant temperature zone of the tube furnace, raise the temperature to 750~950℃, preheat the carbon source gas and then introduce it into the tube furnace, keep the temperature at 750~950℃ to maintain the reaction for 40~60 minutes, and then stop supplying the carbon source gas. (4) Continue to purge the tube furnace with mixed gas for 5-10 minutes, cool it to 200-300°C, then purge with argon and cool it to room temperature, remove the substrate and collect the crude product. (5) The crude product is oxidized in air at 300-400℃ for 1-2 hours, then washed with hydrochloric acid in a water bath at 60-80℃ for 2-6 hours, washed with deionized water until neutral, and dried to obtain oligowalled carbon nanotubes.
2. The method for preparing oligowalled carbon nanotubes according to claim 1, characterized in that: The substrate in step (1) includes at least one of monocrystalline silicon wafers, quartz wafers, and alumina ceramic wafers, and the organic solvent includes at least one of ethanol, acetone, and isoacetone.
3. The method for preparing oligowalled carbon nanotubes according to claim 1, characterized in that: The ultrasonic cleaning conditions in step (1) are a frequency of 80~100kHz, a power of 400~800W, and a cleaning time of 20~30min.
4. The method for preparing oligowalled carbon nanotubes according to claim 1, characterized in that: The catalyst precursor in step (2) includes at least one of ferrocene, ferric acetylacetone, ferric nitrate, cobalt nitrate, and nickel nitrate; the promoter includes at least one of pyrimidine, pyridine, pyrazine, quinoline, acetonitrile, acrylonitrile, triethylamine, cyclohexylamine, dimethylformamide, melamine, and aniline.
5. The method for preparing oligowalled carbon nanotubes according to claim 1, characterized in that: In step (2), the argon gas flow rate is 200~500 sccm and the holding time is 10~20 min.
6. The method for preparing oligowalled carbon nanotubes according to claim 1, characterized in that: The mixed gas in step (3) is argon and hydrogen, with hydrogen accounting for 20% to 50% and the flow rate of the mixed gas being 500 to 1500 sccm.
7. The method for preparing oligowalled carbon nanotubes according to claim 1, characterized in that: The heating rate in step (3) is 5~10℃ / min.
8. The method for preparing oligowalled carbon nanotubes according to claim 1, characterized in that: The carbon source gas in step (3) is at least one of ethylene, acetylene, and propylene. The preheating temperature of the carbon source gas is 400~500℃ and the flow rate is 100~300sccm.
9. The method for preparing oligowalled carbon nanotubes according to claim 1, characterized in that: In step (4), the mixed gas purging flow rate is 200~500 sccm, the cooling rate is 3~5℃ / min, and the argon gas inlet flow rate is 200~500 sccm.
10. The method for preparing oligowalled carbon nanotubes according to claim 1, characterized in that: The hydrochloric acid in step (4) has a mass fraction of 8% to 10%, and the diameter of the oligowalled carbon nanotubes is 3 to 8 nm.