CN107381538A - A kind of preparation method of CNT - Google Patents

Abstract

The invention provides a kind of preparation method of CNT, comprise the following steps：Metal net mask is placed in the cavity of PECVD device on negative plate, two blocks of catalyst metals plates of superposition are placed above the metal net mask；The cavity of the PEVCD equipment is heated and is passed through reacting gas thereto, switches on power, catalyst granules is obtained after reaction；Carbon source and carrier gas will be passed through after the cavity heating of PEVCD equipment, switch on power, CNT is obtained after reaction.The application catalyst metal particles and CNT are completed in same PECVD cavitys, and can realize continuous preparation, improve the efficiency of CNT preparation；On the other hand, low temperature preparation enable CNT be applied to many non-refractories field.

Description

A kind of preparation method of carbon nanotube

technical field

The invention relates to the technical field of carbon nanotubes, in particular to a low-temperature preparation method of carbon nanotubes.

Background technique

Carbon nanotubes have excellent mechanical, electrical, optical and field emission properties. Therefore, since the discovery of carbon nanotubes in 1991, the preparation, performance and application of carbon nanotubes have received extensive attention. At present, the preparation methods of carbon nanotubes mainly include arc discharge method, laser evaporation method and chemical vapor deposition method. Among them, the arc discharge method is to use the reaction gas ionization under high temperature conditions to evaporate the surface of the graphite electrode to obtain carbon nanotubes. The reaction is violent and it is difficult to control the structure of the generated carbon nanotubes; Focusing on the target material mixed with metal catalyst and graphite under high temperature conditions, the process of generating carbon nanotubes through evaporation and catalysis; the chemical vapor deposition method uses metal catalyst particles as templates, and pyrolyzes them at 600-1200 °C Gaseous hydrocarbons form carbon nanotubes. The reaction process of preparing carbon nanotubes by chemical vapor deposition is easy to control and low in cost, and is suitable for mass synthesis.

However, the traditional thermal chemical vapor deposition reaction temperature is too high and the conditions are harsh, which limits the application of carbon nanotubes in the fields of temperature-sensitive materials such as microelectronic materials and polymer materials. In addition, at present, in the process of preparing carbon nanotubes, the catalyst powder used in the thermal chemical vapor deposition method is usually pre-prepared. Due to the van der Waals force between the nano-powders, agglomeration often occurs, which affects the carbon nanotubes. Preparation efficiency and morphology of nanotubes. How to reduce the cost of carbon nanotube preparation and simplify the preparation process is a key issue in the preparation, research and application of carbon nanotubes.

Contents of the invention

The technical problem solved by the invention is to provide a low-temperature preparation method of carbon nanotubes.

In view of this, the application provides a method for preparing carbon nanotubes, comprising the following steps:

A), the metal mesh cover is placed on the negative electrode plate in the cavity of the PECVD equipment, and two superimposed catalyst metal plates are placed above the metal mesh cover;

B), heating the cavity of the PEVCD device and passing a reaction gas into it, turning on the power supply, and obtaining catalyst metal particles after the reaction;

C), heating the cavity of the PEVCD device, feeding carbon source and carrier gas, turning on the power supply, and obtaining carbon nanotubes after reaction.

Preferably, the distance between the two catalyst metal plates is 1-5 cm, the material of the catalyst metal plates is iron, cobalt, nickel or composite metal materials, and hollow patterns are arranged on the surfaces of the catalyst metal plates.

Preferably, the reaction gas in step A) is selected from one or both of hydrogen and argon, the flow rate of the reaction gas is 50-100 sccm, and the power of the power supply is 500-1000W.

Preferably, the particle diameter of the catalyst metal particles is 1-50 nm.

Preferably, the carbon source in step C) includes one or more of methane, ethanol, acetylene and n-butane, and the flow rate of the carbon source is 5-50 sccm.

Preferably, the carrier gas is selected from one or more of hydrogen, nitrogen and argon, and the flow rate of the carrier gas is 100-150 sccm.

Preferably, the reaction temperature in step C) is 350-500° C., the power of the power supply is 10-100 W, and the reaction time is 10-100 min.

Preferably, the metal mesh cover is a cylindrical stainless steel mesh cover or a cylindrical copper mesh cover.

The application provides a method for preparing arrayed carbon nanotubes. Firstly, a metal mesh cover is placed on the negative electrode plate in the cavity of a PEVCD device, and two superimposed catalyst metal plates are placed above the metal mesh cover, and then the cavity Heating and passing reaction gas into it, turning on the power supply, the electric field excites the reaction gas in the chamber to make it into plasma, and by controlling the air pressure in the chamber, a hollow cathode effect is generated between the metal plates, and the high energy in the hollow cathode effect area is used The high-density plasma bombards the thin metal plate, sputters out nano-catalyst metal particles, continues to heat up to the reaction temperature, passes the carbon source and carrier gas into the chamber, turns on the power, and grows carbon nano-particles by using the nanoparticles produced by the decomposition of the catalyst metal particles. Tube. In the process of free growth of carbon nanotubes in this application, an auxiliary metal mesh cover is used to effectively improve the activity of the plasma, decompose the carbon source gas more effectively, and realize the low temperature preparation of carbon nanotubes at 350-500°C, so that The in-situ preparation of arrayed carbon nanotube films on the surface of high-temperature resistant electronic devices has become feasible, broadening its application prospects.

Description of drawings

Fig. 1 is the schematic diagram of the PECVD equipment that the present invention adopts and metal mesh cover device;

Fig. 2 is the scanning electron micrograph of the carbon nanotube prepared in embodiment 1 of the present invention;

Fig. 3 is the transmission electron micrograph of the carbon nanotube prepared in embodiment 1 of the present invention;

Fig. 4 is the scanning electron micrograph of the carbon nanotube prepared in Example 2 of the present invention;

Fig. 5 is the transmission electron micrograph of the carbon nanotube prepared in embodiment 2 of the present invention;

6 is a scanning electron micrograph of carbon nanotubes prepared in Example 3 of the present invention;

FIG. 7 is a transmission electron micrograph of carbon nanotubes prepared in Example 3 of the present invention.

detailed description

In order to further understand the present invention, the preferred embodiments of the present invention are described below in conjunction with examples, but it should be understood that these descriptions are only to further illustrate the features and advantages of the present invention, rather than limiting the claims of the present invention.

The embodiment of the present invention discloses a method for preparing an arrayed carbon nanotube film, comprising the following steps:

A), the metal mesh cover is placed on the negative electrode plate in the cavity of the PECVD equipment, and two superimposed catalyst metal plates are placed above the metal mesh cover;

B), heating the cavity of the PEVCD device and passing reaction gas into it, turning on the power supply, and obtaining catalyst particles after the reaction;

C), heating the cavity of the PEVCD device, feeding carbon source and carrier gas, turning on the power supply, and obtaining carbon nanotubes after reaction.

The present application provides a method for preparing carbon nanotubes. The carbon nanotubes prepared in the present application are actually free-growing carbon nanotubes without a substrate. The catalyst metal particles sputtered by the present application fall on the cathode plate, and it is difficult to effectively combine with the surface, so the carbon nanotubes of the present application exist in the form of particles. The method realizes the low-temperature preparation of the nanotube thin film by utilizing the auxiliary effect of the metal mesh cover.

The preparation method of carbon nanotubes of the present application includes two steps of preparation of nano-catalyst metal particles and preparation of low-temperature carbon nanotubes, and the two steps are continuously completed in the same PECVD reaction chamber.

In this application, the preparation of nano-catalyst metal particles is first carried out. As shown in FIG. 1 , FIG. 1 is a schematic diagram of a PECVD device for preparing carbon nanotubes of the present invention. In the present application, firstly, the metal mesh cover is placed on the negative electrode plate in the cavity of the PECVD equipment, and two catalyst metal plates stacked in sequence are placed above the metal mesh cover. The PECVD chamber described in the present application is the reaction chamber of the PECVD equipment, and the PECVD equipment is equipment well known to those skilled in the art, and the present application has no particular limitation. The PECVD equipment used in the present application is preferably as shown in Figure 1, The setting of the metal mesh cover and the two catalyst metal plates in the PECVD reaction chamber is specifically: the metal mesh cover is placed on the lower plate, and the top of the metal mesh cover and the direct contact with the metal mesh cover are provided with successively superimposed Two catalyst metal plates, the metal mesh cover and the catalyst thin plate are both arranged between the upper pole plate and the lower pole plate. The metal mesh cover in this application may be a cylindrical stainless steel mesh cover or a cylindrical copper mesh cover. The surface of the catalyst sheet described in this application is provided with a hollow pattern to increase the number of catalyst particles sputtered onto the cathode plate. The hollow pattern can be circular or other shapes, and this application has no special limitation. The distance between the two catalyst metal plates in the present application is preferably 1-5 cm. The catalyst metal plate is preferably iron, cobalt, nickel or a composite metal material, and the catalyst metal plate in this application is preferably the same metal material.

In the process of preparing catalyst nanoparticles, the cavity of the PECVD equipment is first heated and the reaction gas is introduced into the PECVD cavity. After reaching the predetermined temperature, the power is turned on, and the electric field excites the reaction gas in the cavity to turn it into plasma. By controlling the gas pressure in the PECVD cavity, a hollow cathode effect is generated between the two catalyst plates. The high-energy and high-density plasma in the hollow cathode effect area is used to bombard the thin metal plate, and the nano-metal particles are sputtered. The distance between the two catalyst sheets is used to control the plasma density generated between the metal plates. Under a certain reaction pressure and power, a high-density plasma is obtained to bombard the metal surface and sputter nano-metal particles. In this process, the metal mesh cover is used to conduct the function of the cathode plate and the catalytic metal plate, so that a hollow cathode effect can be generated between the metal plates. In the above process, the reaction gas is preferably one or both of argon and hydrogen. By controlling the electric field power and selecting a suitable reaction gas, catalyst particles with different particle sizes can be obtained, and the size range is 1-50nm. . The flow rate of the reaction gas is preferably 50-100 sccm. In an embodiment, the reaction gas is preferably hydrogen and argon, the flow rate of the argon gas is preferably 50-80 sccm, and the flow rate of the hydrogen gas is preferably 20-50 sccm . The power of the power supply is preferably 500-1000W, for example, the power of the power supply is preferably 600-800W. The temperature at which the power is turned on is preferably 300-400°C. According to the present invention, the PECVD apparatus is preferably evacuated to 10- ⁴ Pa before the cavity of the PECVD apparatus is heated.

This application generates nano-catalyst particles by stimulating sputtering in the PECVD vacuum chamber, so that the size of the nano-catalyst particles is relatively uniform, and sputtering along different directions reduces the agglomeration of nanoparticles, while avoiding the influence of oxidation on the properties of nano-catalyst metal particles .

After the catalyst metal particles are prepared, the present application continues to prepare carbon nanotubes in the PECVD chamber. This process realizes the low-temperature preparation of carbon nanotubes by using a metal mesh device. The specific process is: continue to heat the chamber of the PECVD equipment, then pass in carbon source gas and carrier gas, turn on the power supply, and obtain carbon nanotubes after reaction. During this process, the metal mesh cover increases the temperature of the reaction area on the one hand, and on the other hand, it can absorb high-energy particles, reduce the etching effect, and facilitate the free growth of carbon nanotubes. The present application has no special restrictions on the carbon source and carrier gas, which are well known to those skilled in the art. The carbon source is preferably selected from one or more of methane, ethanol, acetylene and n-butane , the example, the carbon source is preferably selected from acetylene, the carrier gas is preferably selected from one or more of argon, nitrogen and hydrogen, for example, the carrier gas is preferably selected from argon and hydrogen mixed gas or a mixed gas of argon, hydrogen and nitrogen. As the carrier gas, argon and hydrogen mainly play two roles. On the one hand, the pressure in the reaction chamber is controlled by the introduction of the carrier gas, so that the plasma field is easily excited; on the other hand, the introduction of the carrier gas effectively dilutes the carbon source. Gas is beneficial to the growth of carbon nanotubes, because when the proportion of carbon source gas in the reaction chamber is high, the reaction preparation tends to generate amorphous carbon instead of carbon nanotubes. In the process of preparing carbon nanotubes, it is better to control the proportion of carbon source gas to 5%-20%.

The carbon source gas fed into the PECVD equipment used in this application during the preparation process is preferably 5 sccm-50 sccm, and in an embodiment, the flow rate of the carbon source is preferably 10-20 sccm. The flow rate of the carrier gas is preferably 100 to 150 sccm. For example, the flow rate of argon in the carrier gas is preferably 50 to 80 sccm, the flow rate of hydrogen is preferably 60 to 70 sccm, and the flow rate of nitrogen is preferably 5 to 10 sccm . The reaction time is preferably 10-100 min, for example, the reaction time is preferably 30-60 min; the reaction temperature is preferably 350-500°C, and the power supply is preferably 10-100W, for example, the power The power is preferably 30-60W.

The present application can control the shape and size of the prepared catalyst by adjusting the corresponding reaction parameters, such as reaction temperature, power supply, gas flow rate and reaction time, and then can affect the shape, structure and size of carbon nanotubes. The invention can realize the preparation of carbon nanotubes under the condition of lower than 500°C, and the prepared carbon nanotubes are all multi-walled carbon nanotubes.

As common knowledge in the field, although the preparation equipment used in this example is radio frequency PECVD, the equipment used in this preparation method is also applicable to similar equipment such as direct current PECVD. Compared with the method of preparing carbon nanotubes by traditional thermal chemical vapor deposition and plasma enhanced chemical vapor deposition, the present invention has the advantage of preparing catalyst particles using the electric field of PECVD without additional catalyst; the composition of catalyst particles can be selected by selecting different materials metal plate to control. By controlling the power of the electric field, the size of the catalyst particles can also be effectively controlled. At the same time, since the entire catalyst preparation process is completed in a vacuum, problems such as oxidation and pollution encountered in the catalyst transfer process of the traditional process are avoided, and the agglomeration of catalyst particles can also be avoided to a certain extent.

The metal mesh cover technology adopted in the present invention can effectively reduce the reaction temperature for generating carbon nanotubes, and realize the preparation of carbon nanotubes under the condition of 350-500°C. The method reduces the energy consumed for preparing carbon nanotubes. At the same time, realizing the low-temperature preparation of carbon nanotubes can help to combine with other technologies, such as realizing the composite of carbon nanotubes and some low-temperature alloys or polymer materials, which greatly expands the application field of carbon nanotubes.

In order to further understand the present invention, the preparation method of the arrayed carbon nanotube film provided by the present invention will be described in detail below in conjunction with the examples, and the protection scope of the present invention is not limited by the following examples.

Example 1

A method for preparing carbon nanotubes at 400°C, the method comprising the following steps:

Step 1: Utilize a metal mesh cover made of 316 stainless steel, and place two catalyst metal sheets on the top of the metal mesh cover. The thin plates used in this embodiment are 316 stainless steel sheets, and the distance between the two plates is 1cm. Place the metal mesh cover on PECVD bottom plate.

Step 2: After the reaction chamber is evacuated to 10- ⁴ Pa, argon and hydrogen are introduced into the chamber with flow rates of 60sccm and 30sccm respectively; after heating to 350°C, turn on the power, set the power to 600W, and the sputtering time The time is 10 minutes; the electric field excites the argon and hydrogen in the cavity to generate plasma; by controlling the gas pressure in the cavity, a hollow cathode effect is generated between the catalyst metal plates, and a plasma enrichment zone is generated between the metal sheets, and the high-energy The high-density plasma continuously bombards the metal sheet, causing nano-catalyst metal particles to be sputtered from the surface of the metal sheet;

Step 3: On the basis of step 2, continue heating to make the temperature of the lower plate reach 400°C; at the same time, introduce carbon source gas (acetylene) and carrier gas (argon and hydrogen) into the cavity, and the gas flow rates are respectively 10sccm, 60sccm, 30sccm, the power of the power supply is adjusted to 50W, and the response time is 30min;

Step 4: After the reaction is over, turn off the power supply, stop heating, continue to feed argon and hydrogen, turn off the carbon source, and cool to room temperature with the furnace to obtain carbon nanotubes.

In this embodiment, carbon nanotubes with different lengths can be obtained by controlling the length of the reaction time. In the preparation process of metal catalysts, the main function of argon ions and hydrogen ions is to bombard the metal plate to form catalyst particles; during the growth of carbon nanotubes, argon ions and hydrogen ions can effectively inhibit the production of amorphous carbon and promote the continuous growth of carbon nanotubes. grow. The SEM and TEM photos of the carbon nanotubes prepared in this example are shown in Fig. 2 and Fig. 3, respectively.

Example 2

A method for preparing carbon nanotubes at 500°C, the method comprising the following steps:

Step 1: In this embodiment, a Ni plate and a 316 stainless steel plate are used as catalyst plates, and the distance between the two plates is 1 cm, and the rest of the settings are the same as step 1 in Example 1.

Step 2: After the reaction chamber is evacuated to 10- ⁴ Pa, argon gas and hydrogen gas are introduced into the chamber at a flow rate of 50 sccm and 20 sccm respectively; after heating to 300°C, turn on the power supply and set the power to 500W; The argon ions and hydrogen ions continuously bombard the catalyst metal plate, thereby sputtering catalyst particles; in this embodiment, the content of Ni element in the catalyst particles is increased by using the Ni plate.

Step 3: Heating to make the temperature of the lower plate reach 500°C; at the same time, feed carbon source gas (acetylene) and carrier gas (argon and hydrogen) into the cavity, and the gas flow rates are 5 sccm, 50 sccm, and 20 sccm respectively; The power is adjusted to 30W, and the response time is 30min.

Step 4: Same as Step 4 of Example 1.

Embodiment 2 has three changes relative to Embodiment 1: the one is to adopt Ni metal plate, the purpose is to improve the content of Ni element in the catalyst particle, utilize its activity to promote the growth of carbon nanotube; At the same time, the temperature and power during sputtering are reduced, thereby reducing the preparation cost and improving efficiency; the third is to change the growth temperature of carbon nanotubes, reduce the flow rate and reaction power of carbon source gas, and try to adjust the parameters. Obtain carbon nanotubes with fewer impurities and faster growth rates. The SEM and TEM photos of the carbon nanotubes prepared in this example are shown in Fig. 4 and Fig. 5, respectively.

Example 3

A method for preparing nitrogen-doped carbon nanotubes under the condition of 500°C. The preparation method comprises the following steps:

Step 1: the conditions of the process for preparing catalyst particles are the same as step 1 in Example 2;

Step 2: same as step 2 in Example 2;

Step 3: Heating to make the temperature of the lower plate reach 500°C; at the same time, feed acetylene, argon, hydrogen and nitrogen into the cavity, and the gas flow rates are 5sccm, 50sccm, 20sccm, 5sccm respectively; the power of the power supply is adjusted to 30W, The reaction time is 30 minutes.

Step 4: Same as Step 4 of Example 1.

The main difference between this example and Example 1 is that N ₂ is introduced as an auxiliary gas during the growth of carbon nanotubes to investigate the influence of N doping on the growth of carbon nanotubes. The SEM and TEM photos of the carbon nanotubes prepared in this example are shown in Fig. 6 and Fig. 7, respectively.

The descriptions of the above embodiments are only used to help understand the method and core idea of the present invention. It should be pointed out that for those skilled in the art, without departing from the principles of the present invention, some improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention will not be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (8)

1. A preparation method for carbon nanotubes, comprising the following steps: A), the metal mesh cover is placed on the negative electrode plate in the cavity of the PECVD equipment, and two superimposed catalyst metal plates are placed above the metal mesh cover; B), heating the cavity of the PEVCD device and passing a reaction gas into it, turning on the power supply, and obtaining catalyst metal particles after the reaction; C), heating the cavity of the PEVCD device, feeding carbon source and carrier gas, turning on the power supply, and obtaining carbon nanotubes after reaction. 2. preparation method according to claim 1, is characterized in that, the distance between described two catalyst metal plates is 1～5cm, and the material of described catalyst metal plate is iron, cobalt, nickel or composite metal material, The surface of the catalyst metal plate is provided with a hollow pattern. 3. The preparation method according to claim 1, wherein the reaction gas in step A) is selected from one or both of hydrogen and argon, and the flow rate of the reaction gas is 50 to 100 sccm, so The power of the power supply is 500-1000W. 4. The preparation method according to claim 1, characterized in that, the particle diameter of the catalyst metal particles is 1-50 nm. 5. preparation method according to claim 1, is characterized in that, step C) described carbon source comprises one or more in methane, ethanol, acetylene and n-butane, and the flow rate of described carbon source is 5～ 50 sccm. 6. The preparation method according to claim 1, wherein the carrier gas is selected from one or more of hydrogen, nitrogen and argon, and the flow rate of the carrier gas is 100-150 sccm. 7. The preparation method according to claim 1, characterized in that the reaction temperature in step C) is 350-500°C, the power of the power supply is 10-100W, and the reaction time is 10-100min . 8. The preparation method according to claim 1, characterized in that, the metal mesh cover is a cylindrical stainless steel mesh cover or a cylindrical copper mesh cover.