TW200418721A - A method for growing arrays of carbon nanotubes - Google Patents

Abstract

The present invention pertains to a method for growing arrays of carbon nanotubes on a surface of a metal substrate. The method includes selecting a metal substrate having a smooth surface, oxidizing the metal substrate so as to form an oxide layer on the smooth surface of the metal substrate, depositing a catalyst layer on the oxide layer, and exposing the catalyst layer to a carbon source gas, thereby forming the arrays of carbon nanotubes extending from the metal substrate, following the formation of carbon nanotubes a by-product, such as hydregon gas is produced and reduces the oxide layer.

Description

200418721 V. Description of the invention (1) [Technical field to which the invention belongs] This Sanming is about a method for preparing a nano carbon tube, especially a method for preparing a nano carbon tube array on a common metal substrate. [Prior technology] 'In 1991, a researcher at Japan NE c company I ijima accidentally discovered a nano carbon tube. P56 (1991), because of the excellent characteristics of carbon nanotubes, their potential applications have been receiving widespread attention, especially in the electronics field. Due to the extremely small diameter of carbon nanotubes, from 3 Ϊ i ΐ to more than a dozen nanometers, they can shoot rabbits from their large tasks under the action of a small electric field, so they can be used as field emission cathodes. And, people have carried out various researches in nanomaterials and their application fields :: Lao Guo carbon tube array preparation methods and their applications IX, S, 232, 706 disclosed a field emission device, this development

Ming used the CVD (chemical broad-phase dream, native sacrifice robe) to grow the vertical on a porous silicon substrate; the soil, carbon nanotube array, and its package · ^ ^ ^ ^ Porous layer formed by electrochemical surname engraving method :. : Multi-metal catalyst, finally pass in the carbon and chlorine gas, on: accumulated on the substrate, a height of several hundred ^ / grown on the substrate of Tai \ Kongshixi to obtain a vertical substrate, which is porous, wafer, and; the difference is far superior, The field-emission display of the dot matrix addressing car: electrodes that are capable of carrying large currents and are rushing for high-power traveling waves. In other applications, such as the cathode of the electronic temple, the cathode also needs to have excellent conductivity and can be used. Bear

I ^ ΗΙΙΗ 200418721, invention description (2) An electrode carrying a larger current. In order to make full use of the excellent conductivity of carbon nanotubes, it is necessary to connect them with good conductors, so metal is still the best choice. Because metal materials have a greater influence on the CVD method, metals are likely to alloy with catalysts' or because they have a catalytic effect, they strongly decompose carbon and hydrogen to form carbon deposits, resulting in the inability to grow nano carbon tubes normally. /

Ch. Emmenegger et al. Proposed a method for growing nano-carbon carbon arrays on silicon or metal aluminum substrates, published on Applied Surface

Science 162-163 (2000), 452-456, the method includes the following steps:

1. Apply a 1 ^ (1 ^ 〇3) 3 film on the surface of the silicon or silicon substrate with a thickness of 5 1 Onm; 2. Place the substrate in a reaction furnace and heat it to the carbon nanotube synthesis temperature in a vacuum environment; 3 5 minutes of nitrogen gas flow at a flow rate of 丨 ⑽ "/! ^^; 4 2% of ethylene ethylene gas and 98 ml / min nitrogen gas flow at 0.5 bar for 0.5 to 3 hours; As a result, the nano carbon tube array grows on the catalyst growth point, and the diameter of the nano carbon tube depends on the diameter of the catalyst particles, and the height is 10-15 micrometers.

The above method can grow a nano carbon tube array on a metal aluminum substrate. Although aluminum is a commonly used catalyst support, it is not suitable for field emission cathodes. Moreover, the method has limited choice of substrate materials. Only aluminum and its properties can be selected. Similar limited metal materials have not been able to solve the aforementioned problem of growing carbon nanotubes on ordinary metal substrates. In view of this, there is provided a method for growing nanometers on a common metal substrate.

200418721 V. Description of the invention (3) The method of carbon tube array is really necessary [Content] It is to provide a method suitable for growing carbon nanotubes on a common metal substrate. Another object of the present invention is to provide a field emission cathode In order to achieve the above purpose, the preparation method provided by the present invention is: gold: base metallized the metal substrate, ☆ its surface: formed into two layers of oxygen: supply layer, a catalyst layer is formed on the surface of the lice lip; the catalyst is introduced into the furnace ^ The occurrence of chemical counter-employment makes the body of the two lice too long, and at the same time generates a reducing gas to reduce the oxide layer. Compared to the prior art, the present invention has the following advantages: The present invention has the following advantages: • It is separated from the metal substrate by an oxide layer, so as to avoid the negative effect of the reverse metal substrate on the catalyst and the reaction to generate nano ::. In the production of hydrogen, the oxide layer can be reduced, which can make the carbon nanotubes and metal substrates on the public and private metal substrates to increase the electrical depletion of the carbon nanotubes and the metal substrate. [Embodiment] Please refer to the first figure for details. Inventing a nano carbon tube preparation drawing, which includes the following steps: Step 1 of providing a metal substrate is to provide a metal substrate. The support substrate for growing the nano-carbon camp provided in this step, the metal substrate can be a metal substrate, an alloy sheet, or a metal pole can be formed on the surface of a substrate of other materials. The alloy material does not have special 22, / wool needs to grow at the temperature of the nano carbon tube (generally about 700 t ~ 1〇 {) 〇 ^}, 'only

I surface, page 7, 200418721 V. Description of the invention (4) The following conditions are sufficient: a) no glare occurs; ^ 2 substrates of other materials used are co-soluble; the substrates are compatible; to the growth temperature range Within, its coefficient of thermal expansion and selected use. S Swelling or cracking due to hydrogen absorption during the growth process can be used. If a metal sheet or alloy sheet is directly selected, only a is required. Most metal materials can meet the above conditions, such as, = u, stainless steel. And other alloys. The other poles are required to have one surface and two surfaces: ', which can form a metal or alloy electromagnetron sputtering method on the surface. The method of setting the flatness and opening) to form the electrode includes electroplating, and an array of ordered carbon nanotubes is used for this purpose. One method is to use mechanical abrasion or electrochemical polishing on the surface; = =. Thousands of degrees, in order to meet the needs of growing carbon nanotube arrays by ordinary CVD method. It is to beautify the metal substrate and generate an oxide layer. The gold provided in step 1 [ίΐΐ ΐ: Table: "It is an oxide layer. The thickness of the oxide layer is less than 1 and heated to -4 in air. A simpler method is to form an oxide layer. The surface of the metal substrate is Y series 3 A catalyst layer is formed on the oxide layer. That is, 200418721 formed in step 2.

5. Description of the invention (5) A catalyst layer is formed on the oxide layer on the surface of the metal substrate. Currently, the commonly used catalysts for growing carbon nanotube arrays by CVD are metal iron, cobalt, nickel, and their oxides. The methods for forming the catalyst layer include electron beam evaporation and other electrochemical methods. The thickness of the catalyst layer only needs to be 1 nm to 0 nm. Step 4 is an annealing treatment of the catalyst layer. The metal substrate with the metal catalyst layer formed in step 3 is annealed so that the catalyst layer is formed into nano-sized catalyst particles. If the catalyst is a metal, the oxidation reaction is accompanied by an oxidation reaction during the annealing process to oxidize the metal to a metal oxide. . The particle size obtained by annealing will determine the diameter of the carbon nanotubes to be grown in the future.

Step 5 is a CVD method for growing a carbon nanotube array and reducing the oxide layer to a metal. Growing a carbon nanotube array on the above metal substrate by a CVD method,

At the same time, the surface oxide layer of the metal substrate formed in step 2 is reduced to metal. The growth conditions of the CVD method are basically the same as the conditions for growing carbon nanotubes on a porous silicon substrate. A carbon source gas, such as ethylene or acetylene, is introduced at a certain temperature (for example, 70 0 ° C to 100 ° C). ) Under the reaction, nano-carbon is grown on the catalyst particles. During the reaction, the carbon source gas releases hydrogen to reduce the surface oxide layer of the metal substrate to metal, so that the nano-carbon tube directly contacts the metal substrate. Specific embodiments illustrate the process of the method of the invention. Please refer to the second figure. In this example, the younger brother Chu Yiyue used a stainless steel 10 as the metal substrate. It is a high-visibility alloy with a melting point of more than 1,000. And it will not absorb hydrogen during the reaction and 4 TO expands or cracks in this life. The size can be determined according to specific requirements. Without money, the surface of the milk must be certain to meet the needs of growing carbon nanotube arrays. In general, the better the flatness,

200418721 V. Description of the invention (6) The better the order of the obtained carbon nanotubes), the smoothness of the surface can be achieved by means of mechanical light and electrochemical light. Next, as shown in the third figure, the non-recording steel 10 is heated in air to 500 ° C, and an oxidation reaction occurs. After a period of time, a surface of the stainless steel 10 is formed with a metal oxide layer 12 whose thickness and oxidation are The reaction time is related. The longer the time is, the thicker the thickness is. The thickness of the metal oxide layer 12 can be less than 1 micrometer, and it is preferably 10 to 100 nanometers. As shown in the fourth figure, a catalyst layer 14 is formed on the metal oxide layer 12 by an electron beam evaporation method. The catalyst layer 1 4 is generally metallic iron,

The thickness of the catalyst layer 14 is cobalt, nickel or an oxide thereof, and the thickness is about 1 to 10 nm. Thus, the catalyst layer 14 is connected to the stainless steel 10 through the metal oxide layer 12 so that the catalyst layer 14 is spaced from the stainless steel 10. Preferably, the catalyst layer 14 is further placed in the air and annealed at a temperature of 300 ° C for a period of time so that the catalyst layer 14 is oxidized and shrunk into nano-sized catalyst particles. Finally, the carbon source gas ethylene was passed in, and a nano carbon official array 16 was grown on the catalyst layer 4 by a CVD method. The catalyst layer 14 and the stainless steel 10 were separated by a metal oxide layer 12. Therefore, During the reaction, stainless steel ι 〇 = will affect the catalytic effect of the catalyst, and nano carbon tubes can grow smoothly. Ethylene cracking reaction produces nano carbon tubes, and hydrogen is released at the same time.

The reduction reaction of the metal oxide layer 12 on the surface of the steel If will eventually oxidize the metal to metal, so that the carbon nanotube 16 is in direct contact with the stainless steel, as shown in the fifth figure. The silicon substrate and then in the second embodiment of the present invention, a silicon substrate is first provided with a surface for polishing treatment so as to have a certain flatness;

Page 10 200418721 V. Description of the invention

A metal or alloy layer is formed on the surface of the sheet by an electroplating method as an eighth substrate; then, the read metal substrate is subjected to the aforementioned steps 2, + metal step, and step 5 to generate a nano carbon tube on the metal substrate. ^ Vermiculite, step 4 can be replaced with other non-metallic materials such as glass and quartz. The k silicon substrate is also a method for preparing a nano carbon tube provided by the present invention, which can be combined with, or an alloy as a metal substrate, and is not limited to the methods of oxidizing and forming a catalyst layer of the two kinds of two-way metal metal substrates described above. Middle: The enumerated formulas are not limited to the carbon source gases and catalysts used for growing the carbon nanotubes. The ordinary source gases and catalysts known to those skilled in the art can be used. . In summary, the present invention has indeed met the requirements for an invention patent, and a patent declaration was submitted in accordance with the law. However, the above is only a preferred embodiment of the present invention, and it cannot be used to limit the scope of patent application in this case. All equivalent modifications or changes made by those skilled in the art of the case with the aid of the spirit of the present invention shall be covered by the scope of the following patent applications.

200418721 Brief description of the diagram The first diagram is a flowchart of a method for preparing a carbon nanotube of the present invention. The second figure is a schematic view of a substrate used in the method for preparing a carbon nanotube of the present invention. The third figure is a schematic diagram of forming an oxide layer on the surface of the substrate used. The fourth diagram is a schematic diagram of forming a catalyst layer on an oxide layer. The fifth figure is a schematic view of a nano carbon tube array obtained by using the method for preparing a nano carbon tube according to the present invention. [Description of Symbols of Main Components] Stainless Steel Catalyst Layer 10 14 Metal Oxide Layer Nano Carbon Tube Array 12 16

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Claims (1)

200418721 VI. Application Patent Scope 1. A method for preparing nano carbon tubes, comprising the steps of: providing a metal substrate; oxidizing the metal substrate to form an oxide layer on the surface thereof; forming a catalyst layer on the surface of the oxide layer; passing in carbon The hydrogen gas undergoes a chemical reaction under the action of the catalyst, so that the carbon nanotubes grow from the catalyst layer, and a reducing gas is generated to reduce the oxide layer. 2. The method for preparing a nano carbon tube according to item 1 of the scope of patent application, wherein the metal substrate includes Ta, Ni, Ag, Fe, Cu. 3. The method for preparing a nano carbon tube according to item 1 of the scope of patent application, wherein the metal substrate comprises a metal alloy. 4. The method for preparing a nano carbon tube as described in item 3 of the patent application scope, wherein the alloy includes stainless steel. 5. The method for preparing a nano carbon tube as described in item 1 of the scope of patent application, wherein the thickness of the oxide layer is 1000 nanometers. 6. The method for preparing a nano carbon tube according to item 1 of the scope of patent application, wherein the catalyst layer comprises a metal catalyst or an oxide thereof. 7. The method for preparing a nano carbon tube according to item 6 of the scope of patent application, wherein the metal catalyst comprises iron, cobalt, nickel or an alloy thereof. 8. The method for preparing a nano carbon tube according to item 1 of the scope of the patent application, wherein the thickness of the catalyst layer is 1 to 10 nanometers. 9. The method for preparing a nano carbon tube according to item 1 of the scope of patent application, wherein the reducing gas is hydrogen. 1 0. A method for preparing a nano-carbon tube field emission cathode, comprising the steps of: Page 13 200418721 6. Application for Patent Example 5 Provide a cathode substrate; form a metal electrode on the surface of the cathode substrate; oxidize the metal electrode to form an oxide layer on its surface, form an oxide layer on the surface of the oxide layer, and pass in a hydrocarbon gas, and A chemical reaction occurs under the action of the catalyst, so that the carbon nanotubes grow from the catalytic sword layer, and a reducing gas is generated to transport the emulsified layer. 11. The method for preparing a nano-carbon tube field emission cathode as described in item 10 of the scope of patent application, wherein the cathode substrate includes glass, stone or quartz. 1 2 · The method for preparing a nano-carbon tube field emission cathode as described in item 10 of the scope of patent application, wherein the metal electrode includes Ta, Ni, Ag, Fe, 1 3 · As the item of scope of patent application 10 The method for preparing a field emission cathode of a carbon nanotube is described, wherein the metal electrode comprises a metal alloy. 14. The method for preparing a nano-carbon tube field emission cathode as described in item 13 of the scope of patent application, wherein the alloy includes stainless steel. 15 · The method for preparing a nano rabbit official field emission cathode as described in item 1 q of the scope of patent application, wherein the thickness of the oxide layer is 1000 nm. 16. The method for preparing a nano-carbon tube field emission cathode as described in item 10 of the scope of patent application, wherein the catalyst layer comprises a gold catalyst or an oxide thereof. 17 · The method for preparing a nano-carbon tube field emission cathode as described in item 16 of the scope of patent application, wherein the metal catalyst includes iron, cobalt, nickel or an alloy thereof 200418721 VI. Application for patent scope 1 8. The method for preparing the nano carbon tube field emission cathode described in item 10 of the scope of patent application, wherein the thickness of the catalyst layer is 1 to 10 nanometers. 19. The method for preparing a nano-carbon tube field emission cathode according to item 10 of the scope of the patent application, wherein the reducing gas is hydrogen. Page 15