TWI385269B - Method of making carbon nanotube - Google Patents

Description

Method for preparing nano carbon tube

The invention relates to a preparation method of a nano material, in particular to a preparation method of a carbon nanotube.

Carbon Nanotube (CNT) is a new type of carbon material discovered by Japanese researcher Iijima in the product of arc discharge in 1991. See "Helical Microtubules of Graphitic Carbon", S. Iijima, Nature, vol. 354, p56 (1991). The carbon nanotubes have excellent comprehensive mechanical properties such as high elastic modulus, high Young's modulus and low density, as well as excellent electrical properties, thermal properties and adsorption properties. The nanocarbon tubes may exhibit metallic or semiconducting properties as the carbon nanotubes are spirally changed. Due to the excellent properties of carbon nanotubes, it is expected to play an important role in the fields of nanoelectronics, materials science, biology, and chemistry.

At present, the method for preparing a carbon nanotube is mainly a chemical vapor deposition (CVD) method. Chemical vapor deposition mainly uses a transition metal or its oxide as a catalyst to decompose a carbon-containing source gas at a relatively low temperature and grow a carbon nanotube on the substrate provided.

When the carbon nanotube is applied to a field emission display, an electron gun, a high-power traveling wave tube, etc., the field emission plane shows that the address of the lattice requires an electrode having good conductivity and capable of carrying a large current; the electron gun, high power The cathode of a device such as a traveling wave tube also requires a substrate capable of carrying a large current, and for these applications, the metal substrate is the best material.

At present, since the growth of the carbon nanotubes mostly uses a transition metal as a catalyst, since the transition metal catalyst is easily alloyed with other metals, The catalyst is inactivated, resulting in the inability to grow the carbon nanotubes. Therefore, the growth of the carbon nanotubes is mostly based on materials such as ruthenium, ruthenium dioxide, and glass, and it is impossible to grow the carbon nanotubes on the metal substrate.

Ch. Emmenegger discloses a method of forming a carbon nanotube array on a metal substrate, see "Carbon nanotube synthesized on metallic substrate", Ch. Emmenegger, Applied Surface Science, vol. 162-163, P452-456 (2000) . They applied Fe(NO ₃ ) ₃ coating to form nano-scale iron oxide (Fe ₂ O ₃ ) particles by heat treatment by coating iron nitrate (Fe(NO ₃ ) ₃ ) on the aluminum substrate to nanometer-scale Fe. _{The 2} O ₃ particles are catalysts, and then a mixture of acetylene carbon source gas and shielding gas is introduced to grow the carbon nanotube array. However, due to the poor conductivity of Fe ₂ O ₃ , the electrical contact between the carbon nanotubes and the metal substrate is poor, which limits the application of the carbon nanotubes as an electronic device. Moreover, the method requires heat treatment to treat the transition layer into a nano-sized particle catalyst, and the process step of growing the carbon nanotubes on the metal substrate is increased, so that the cost is high.

In view of this, it is possible to provide a carbon nanotube directly grown on a metal substrate without adding a transition layer or a catalyst between the metal substrate and the carbon nanotube, which is simple in process and low in cost, and is suitable for mass production of carbon nanotubes. The preparation method is really necessary.

A method for preparing a carbon nanotube, comprising the steps of: providing a copper substrate, polishing a surface of the copper substrate; placing the polished copper substrate in a heating furnace, introducing a protective gas, and heating to 400 °C-800 ° C; carbon source gas is introduced into the heating furnace, and the carbon nanotubes are grown at 400 ° C - 800 ° C.

Compared with the prior art, the preparation method of the carbon nanotube provided by the technical solution can directly grow the carbon nanotube on the metal copper, and does not need to add a transition layer between the metal copper and the carbon nanotube, and the process is simple. , low cost, suitable for mass production.

Hereinafter, a method for preparing a carbon nanotube provided by the present technical solution will be described in detail with reference to the accompanying drawings and specific embodiments.

Referring to FIG. 1 , an embodiment of the present technical solution provides a method for preparing a carbon nanotube, and specifically includes the following steps: Step 1: providing a copper substrate, and polishing the surface of the copper substrate.

The polishing process includes the following steps: First, the surface of the copper substrate is repeatedly rubbed in the first direction for 3 minutes to 5 minutes using a 600-800 mesh sandpaper. Then, the powder generated on the surface of the copper substrate by friction is removed.

Next, the surface of the copper substrate is repeatedly rubbed in the second direction using a 1000 mesh-1300 mesh paper for 5 minutes to 8 minutes. Then, the powder generated on the surface of the copper substrate by friction is removed.

Finally, the surface of the copper substrate is repeatedly rubbed in the first direction for 10 minutes to 15 minutes using a 1500 mesh-2000 mesh paper. Then, the powder generated on the surface of the copper substrate by friction is removed.

Forming an angle α between the first direction and the second direction, 0∘<α 90 ∘, preferably, α is 90 ∘. The above method of removing the powder generated by the friction of the surface of the copper substrate is a method of wind blowing, and a hair dryer or the like can be used.

The specific shape of the copper substrate is not limited, and preferably, the copper substrate is In the shape of a rectangular parallelepiped, the copper substrate has a thickness of 0.5 cm to 5 cm, and the surface for growing the carbon nanotubes has an area of 4 cm 2 to 100 cm 2 .

The purpose of the above-mentioned polishing treatment on the surface of the copper substrate is as follows: one is to make the surface of the copper substrate as flat and smooth as possible, which is favorable for the growth of the carbon nanotubes; and second, in the process of polishing the surface of the copper substrate with sandpaper. Since the sandpaper rubs the copper substrate in different directions and the sandpaper is fine, fine mesh scratches or grooves are formed on the surface of the copper substrate.

Step 2: The polished copper substrate is placed in a reaction furnace, and after passing through a shielding gas, it is heated to 400 ° C - 800 ° C.

The polished copper substrate is placed in a reaction boat, which is generally a quartz boat, and the reaction boat is loaded into a reaction furnace, which may be a box furnace or a tube furnace, etc. For example, a tubular heating furnace is preferably provided. The reaction vessel is placed in the center of the tubular heating furnace, and after passing through a shielding gas, it is heated to a temperature of from 400 ° C to 800 ° C, preferably to 700 ° C.

During the above heating process, the mesh scratches or grooves on the surface of the copper substrate further form copper particles of uniform size, which provide nucleation for the growth of the carbon nanotubes and act as a catalyst. The diameter of the copper particles is from 1 nm to 10 nm, and the density of the copper particles is related to the angle between the rubbing time and the rubbing direction of the sandpaper during polishing. The more the number of rubbing, the smaller the angle between the rubbing directions, and the copper. The greater the density of the particles.

Step 3: The reaction gas is introduced into the heating furnace, and the carbon nanotubes are grown at a temperature of 400 ° C to 800 ° C for a period of time.

a reaction gas formed by introducing a mixed gas of a carbon source gas and a shielding gas into the heating furnace, wherein the carbon source gas is a hydrocarbon, which may be acetylene, ethylene, etc., since the carbon source gas first needs to be cracked during the reaction, and acetylene Pyrolysis temperature The degree is low, so in the present embodiment, acetylene is preferably a carbon source gas. The shielding gas is an inert gas or nitrogen, and this embodiment is preferably nitrogen. The carbon nanotubes were grown at a temperature of 400 ° C to 800 ° C for 5 minutes to 30 minutes. Since the copper substrate is formed with copper particles of uniform size, the copper particles provide a nucleus for the growth of the carbon nanotubes during the growth of the carbon nanotubes, that is, the copper particles act as a catalyst to allow the carbon nanotubes to grow. After cooling, the copper substrate was taken out, and a plurality of carbon nanotubes were formed on the surface of the copper substrate.

Referring to FIG. 2 and FIG. 3, the carbon nanotubes prepared in this embodiment are randomly arranged on the surface of the copper substrate, and one end of the carbon nanotube is connected to the copper substrate, and the diameter of the carbon nanotube is 5 M-20 nm.

The preparation method of the carbon nanotube provided by the technical solution can directly grow the carbon nanotube on the metal copper, and does not need to add a transition layer between the metal copper and the carbon nanotube, the process is simple, the cost is low, and the method is suitable. Mass production.

By adopting the method of the technical solution, the carbon nanotubes can be formed directly on the electrodes of the electronic devices such as the field emission display, the electron gun, the high-power traveling wave tube, etc., thereby avoiding the preparation of the carbon nanotubes first, and then attaching the carbon nanotubes to the A complex process on the applied device.

In summary, the present invention has indeed met the requirements of the invention patent, and has filed a patent application according to law. However, the above description is only a preferred embodiment of the present invention, and it is not possible to limit the scope of the patent application of the present invention. Equivalent modifications or variations made by persons skilled in the art in light of the spirit of the invention are intended to be included within the scope of the following claims.

1 is a flow chart of a method for preparing a carbon nanotube according to an embodiment of the present technical solution.

2 is a scanning electron micrograph of a carbon nanotube prepared by an embodiment of the present technical solution.

3 is a transmission electron micrograph of a carbon nanotube prepared by an embodiment of the present technical solution.

Claims (11)

A method for preparing a carbon nanotube, comprising the steps of: providing a copper substrate, polishing a surface of the copper substrate; placing the polished copper substrate in a reaction furnace, introducing a protective gas, and heating to 400 ° C - 800 ° C; and a mixture of carbon source gas and shielding gas is introduced into the heating furnace, and the carbon nanotubes are grown at 400 ° C - 800 ° C. The method for preparing a carbon nanotube according to claim 1, wherein the step of polishing the surface of the copper substrate comprises the following steps: repeating the first direction by using a 600-800 mesh sandpaper. Rubbing the surface of the copper substrate for 3 minutes to 5 minutes; repeatedly rubbing the surface of the copper substrate in the second direction with a 1000 mesh to 1300 mesh sandpaper for 5 minutes to 8 minutes; and repeatedly rubbing the first direction with a 1500 mesh to 2000 mesh sandpaper The surface of the copper substrate is 10 minutes to 15 minutes. The method for preparing a carbon nanotube according to claim 2, wherein an angle α, 0∘<α is formed between the first direction and the second direction. 90∘. The method for preparing a carbon nanotube according to claim 2, wherein the step of polishing the surface of the copper substrate further comprises the step of removing the surface of the copper substrate by friction to generate a powder. The method for producing a carbon nanotube according to claim 4, wherein the step of removing the powder generated by the friction on the surface of the copper substrate is a step of applying a wind. The method for preparing a carbon nanotube according to claim 1, wherein the copper substrate is a rectangular parallelepiped. The method for preparing a carbon nanotube according to claim 6, wherein the copper substrate has a thickness of 0.5 cm to 5 cm. The method for preparing a carbon nanotube according to claim 1, wherein the reactor is a box furnace or a tube furnace. The method for preparing a carbon nanotube according to claim 1, wherein the shielding gas is an inert gas or nitrogen. The method for producing a carbon nanotube according to claim 1, wherein the carbon source gas is acetylene or ethylene. The method for preparing a carbon nanotube according to claim 1, wherein the carbon nanotube has a growth time of 5 minutes to 30 minutes.