CN101857460A - Preparation method of carbon nanotube array for spinning - Google Patents

Abstract

The invention discloses a method for preparing a carbon nanotube array for spinning, which comprises the following steps: firstly preparing an oxide buffer layer on a prefabricated silicon substrate, and then depositing a metal catalyst film on it to form a composite active carbon nanotube Tube array growth catalytic structure; then heat up the reaction furnace to the growth temperature of carbon nanotubes in a protective gas environment; then feed ethylene and carrier gas into the reaction furnace to control the flow rate and ratio, and grow carbon nanotube arrays under normal pressure; after completion Rapidly terminates the growth of carbon nanotube arrays. The invention adopts the application of the ethylene CVD preparation method, prepares the catalyst buffer layer structure through the ion beam assisted deposition method, and combines the control of the thickness of the metal catalyst film and the growth process parameters, and the prepared carbon nanotube array has a small carbon nanotube diameter. The advantages of small number of tube walls, high surface distribution density of carbon tubes on the substrate, and large-area preparation provide the possibility for carbon nanotubes to be used in industrial spinning manufacturing.

Description

Preparation method of carbon nanotube array for spinning

technical field

The invention relates to a method for preparing a large-area spinnable carbon nanotube array, belonging to the field of nanomaterial preparation.

Background technique

Carbon nanotube (CNT) has excellent mechanical properties: its tensile strength reaches 50-200GPa, which is 100 times that of steel, but its density is only 1/6 of steel, and the theoretical Young's modulus of carbon nanotube can reach 1TPa, so it is Called "super fiber". In addition, carbon nanotubes have good electrical conductivity. Due to their special graphite layered structure, they exhibit different electrical properties and electrical conductivity, and have excellent electrical modulation properties. Therefore, the use of carbon nanotubes to construct new mechanical, electrical, and optical functional devices has become an important direction for the development of carbon nanomaterials.

In recent years, people have made rapid progress in the controllable preparation and assembly technology of carbon nanotubes. Among them, carbon nanotube array materials have attracted extensive attention due to their consistent self-assembly orientation characteristics, and progress has been made in the preparation of carbon nanotube array devices and the application of composite materials. In 2002, the research group of Academician Fan Shoushan of my country reported for the first time in the journal Nature that based on the vertical spinnable carbon nanotube array, the solid carbon nanotube array can be continuously spun to process a pure carbon nanotube. Fiber materials have created a new field of research on carbon nanotube material assembly technology [Document 1].

At present, in the preparation of spinnable carbon nanotube arrays, acetylene and ethylene are generally used as carbon source gases [References 1, 2], and metal particles are used as catalysts on silicon wafer substrates by thermal chemical vapor deposition (TCVD). The preparations are called the acetylene CVD method and the ethylene CVD method, respectively. At present, the technology of preparing spinnable carbon nanotube arrays with acetylene gas has made a breakthrough. The research group of Fan Shoushan in my country and the research group of Baughman in the United States have realized the preparation of spinnable carbon nanotube arrays, and further enlarged the growth area of the arrays. , realizing the preparation of large-area high-quality spinnable carbon nanotube arrays. On this basis, carbon nanotube films were processed by dry spinning, and were successively applied to the preparation of carbon nanotube functional devices such as loudspeakers [Document 3], transparent conductive films [Document 4], and artificial muscles [Document 5]. , showing a very broad application prospect of this material. In the preparation of spinnable carbon nanotube arrays by ethylene CVD, Li Qingwen et al. achieved the preparation of ultra-long (greater than 1mm) spinnable carbon nanotube arrays by improving the catalyst structure, and processed high-strength carbon nanotube arrays. Carbon nanotube fiber material [Document 6]. However, so far, there is still no breakthrough in the large-area preparation technology for the preparation of spinnable carbon nanotube arrays by ethylene gas, let alone the realization of the film-drawing technology of carbon nanotube arrays.

In addition, compared with the preparation of spinnable carbon nanotube arrays by acetylene CVD, the catalyst structure used in ethylene CVD growth is more complex and the growth temperature is higher. The lifetime is different from the acetylene CVD array fabrication process. At the same time, the cracking products of ethylene gas and acetylene gas are also very different, which leads to the differences in the number of tube walls, tube diameter, defect density, physical and chemical properties of carbon nanotubes grown by the two carbon source gases. . Therefore, the use of ethylene CVD to grow large-area spinnable carbon nanotube array materials has potential application value in the preparation of carbon nanotube functional devices.

[Document 1]: Jiang, K.L.; Li, Q.Q.; Fan, S.S., Nanotechnology: Spinning continuous carbon nanotube yarns-Carbon nanotubes weave their way into a range of imaginative macroscopic applications. Nature 2002, 419, 801.

[Document 2]: Li, Q.W.; Zhang, X.F.; DePaula, R.F.; Zheng, L.X.; Zhao, Y.H.; Stan, L.; carbonnanotube arrays for fiber spinning. Advanced Materials 2006, 18, 3160.

[Document 3]: Xiao, L.; Chen, Z.; Feng, C.; Liu, L.; Bai, Z.Q.; Wang, Y.; Qian, L.; Zhang, Y.Y.; Li, Q.Q.; Jiang, K.L. ; Fan, S.S., Flexible, Stretchable, Transparent Carbon Nanotube Thin Film Loudspeakers. Nano Letters 2008, 8, 4539.

[Document 4]: Feng, C., Liu, K., Wu, J.S., Liu, L., Cheng, J.S., Zhang, Y.Y., Sun, Y.H., Li, Q.Q., Fan, S.S., Jiang K.L., Flexible, Stretchable , Transparent Conducting Films Made from Superaligned Carbon Nanotubes. Advance Functional Materials 2010, 20, 1.

[Document 5]: Aliev, A.E.; Oh, J.Y.; Kozlov, M.E.; Kuznetsov, A.A.; Fang, S.L.; Fonseca, A.F.; Ovalle, R.; ; Zakhidov, A.A.; Baughman, R.H., Giant-Stroke, Superelastic Carbon Nanotube Aerogel Muscles. Science 2009, 323, 1575.

[Document 6]: Zhang, X.F.; Li, Q.W.; Tu, Y.; Li, Y.A.; Coulter, J.Y.; fibers spun from long carbon-nanotube arrays. Small 2007, 3, 244.

Contents of the invention

In order to further deepen the application of ethylene CVD growth large-area spinnable carbon nanotube array material, the purpose of the present invention is to provide a method for preparing a carbon nanotube array for spinning, so that the obtained carbon nanotube array height and The structure is uniform, and carbon nanotube fibers and carbon nanotube films can be processed.

Above-mentioned purpose of the present invention, the technical scheme that realizes is:

The method for preparing a carbon nanotube array for spinning is characterized in that it includes the following steps: firstly, an oxide buffer layer is prepared on a prefabricated silicon substrate, and then a metal catalyst film is deposited thereon to form a highly active carbon nanotube array growth Composite catalytic structure; then heat up the reaction furnace to the carbon nanotube growth temperature of 700 ℃ ~ 800 ℃ under the protective gas environment; then feed ethylene and carrier gas into the reaction furnace with controlled flow rate and ratio, and conduct carbon nanotube array under normal pressure Growth: After the growth is completed, quickly end the growth of the carbon nanotube array within 1 minute.

Further, in the preparation method of the above-mentioned carbon nanotube array for spinning:

The prefabrication of the silicon substrate in step I refers to forming a silicon dioxide oxide layer with a thickness of 0.1 μm to 1 μm on a silicon wafer with an area larger than 1 cm ² . Prepare an oxide buffer layer with a thickness of 5nm to 100nm and a disordered structure by ion beam assisted evaporation; and prepare a metal catalyst film of iron, cobalt or nickel with a thickness of 0.4nm to 5nm on the surface of the oxide buffer layer by electron beam evaporation .

The protective gas environment used in step II is created by mixing inert gas and H ₂ .

The carbon source gas used in step III is ethylene, and the partial pressure of the carbon source gas ranges from 5% to 40%; the growth mode of the carbon nanotube array is bottom growth under normal pressure.

The method for ending the growth of the carbon nanotube array in step IV refers to reducing the temperature of the carbon nanotube array sample in the reaction furnace, or reducing the carbon source content around the carbon nanotube array sample.

Implement technical scheme of the present invention, compared with the advantage of acetylene CVD preparation method is:

The invention adopts the ethylene CVD method, prepares the catalyst buffer layer structure by the ion beam assisted deposition method, and combines the thickness of the metal catalyst film and the growth process parameters by controlling the carbon nanotube array. The advantages of small number, high surface distribution density of carbon tubes on the substrate, and large-area preparation provide the possibility for carbon nanotubes to be used in industrial spinning manufacturing.

In order to make the preparation method of the carbon nanotube array for spinning in the present invention easier to understand its substantive features and practicability, several specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. But the following descriptions and illustrations about the embodiments do not constitute any limitation to the protection scope of the present invention.

Description of drawings

Fig. 1 is a schematic flow diagram of the method for preparing a large-area spinnable carbon nanotube array of the present invention;

Fig. 2 is the method schematic diagram of catalyst preparation in the preparation method of the present invention;

Fig. 3 is the schematic diagram and scanning electron microscope photo of the carbon nanotube array for spinning prepared by the present invention on a 4-inch silicon wafer substrate;

Fig. 4 is the transmission electron micrograph of carbon nanotube array shown in Fig. 3;

Fig. 5 is the schematic diagram that the carbon nanotube array that the present invention makes is pulled film and obtains carbon nanotube film;

Fig. 6 is a schematic diagram of carbon nanotube fibers obtained by drawing carbon nanotube arrays prepared in the present invention.

Detailed ways

In view of the wall number, tube diameter, defect density and physical and chemical properties of carbon nanotubes grown by ethylene CVD are different from those of acetylene CVD, its application prospect is broad. In order to break through the bottleneck of preparing large-area spinnable carbon nanotube arrays by the ethylene CVD method, the inventive team of the present invention has finally developed the preparation method of the nanotube array for spinning after painstaking research. The preparation method has good repeatability. And it is easy to scale up and implement; the resulting large-area spinnable carbon nanotube array can be used to prepare new materials such as transparent conductive films and high-performance carbon nanotube fibers.

Specifically: the implementation steps of the preparation method of the present invention are shown in the flow diagram of Figure 1, mainly including four steps, which are respectively: first prepare an oxide buffer layer on a prefabricated silicon substrate, and then deposit a metal catalyst on it film to form a catalytic structure for the growth of carbon nanotube arrays with recombination activity; then the reaction furnace is heated up to the carbon nanotube growth temperature of 700°C to 800°C in a protective gas environment; then ethylene and The carrier gas is used to grow the carbon nanotube array under normal pressure; after the growth is completed, the growth of the carbon nanotube array is quickly terminated within 1 minute.

From Fig. 1, step I of the present invention can be further refined into two steps of prefabrication of silicon substrate and preparation of catalytic thin film. Among them, the prefabrication of the silicon substrate refers to generating a silicon dioxide oxide layer with a thickness of 0.1 μm to 1 μm on a silicon wafer with an area greater than ¹ cm (the silicon wafer with a size of 4 inches is used in this embodiment); and the preparation of the catalytic film refers to A thin film of iron, cobalt, nickel or a mixture of the three with a thickness of 0.4nm to 5nm is formed on the silicon substrate prepared above by electron beam evaporation. However, in order to improve the activity and lifespan of the metal catalyst film, the method of the present invention is to introduce oxide buffer layers such as aluminum oxide and magnesium oxide between the metal catalyst film and the silicon substrate, so as to ensure that the array of grown carbon nanotubes has Suitable growth density, degree of orientation and length uniformity properties. Wherein the oxide buffer layer is a dense oxide with a disordered structure prepared by ion beam assisted evaporation (IBAD), and the thickness is between 5nm and 100nm.

After completing the preparation of the metal catalyst thin film on the silicon substrate, the prepared substrate material was placed in a 5-inch diameter quartz reaction tube, and the substrate material was heated to growth in a 4: ₁ Ar/H protective gas environment. temperature (the growth temperature ranges from 700° C. to 800° C., preferably 750° C. in this embodiment). The metal catalyst thin film nucleates uniformly on the surface of the alumina buffer layer under the protective gas environment. After the temperature of the sample is stabilized, ethylene gas with a carbon source gas partial pressure of 5% to 40% is introduced (15% is used in this embodiment, and the carrier gas is 5% hydrogen and 80% argon), and the growth time is 10min. The total gas flow is 2L/min. After the growth is over, the reaction quartz tube is evacuated by a vacuum pump, and the vacuum degree quickly reaches about 1Pa within 10 seconds. Through the exhaust of the vacuum pump, the carbon source gas around the metal catalyst film can be rapidly reduced, so as to achieve the method of rapidly ending the growth of the carbon nanotube array. Finally, the prepared sample was cooled to room temperature under the protection of argon, and the sample was taken out.

As shown in Figure 3, the carbon nanotube array sample prepared by the present invention through atmospheric pressure bottom growth, the carbon nanotube array has a uniform structure, scanning electron microscopy analysis shows that the carbon nanotube array has a super smooth arrangement structure, the array height It is about 400 μm. After taking a small part of the carbon nanotube array and ultrasonically dispersing it in the ethanol solution, the structure of the carbon nanotube in the carbon nanotube array was analyzed in a transmission electron microscope. The analysis results are shown in Figure 4. The diameter of the carbon nanotube in the array is Mainly distributed in 4nm to 7nm, the number of tube walls is 3 to 6 walls.

In the fourth step, the method of quickly ending the growth of the carbon nanotube array, in addition to the above-mentioned vacuuming—the method of rapidly reducing the carbon source gas around the metal catalyst film, can also reduce the temperature of the carbon nanotube array sample in the reaction furnace, In an environment much lower than the growth temperature, the growth reaction will stop immediately, thereby maintaining the growth density, orientation degree and length uniformity of the carbon nanotube array.

By spinning the carbon nanotube array, the experimental results show that the carbon nanotube array prepared by this method has very good continuous spinning properties. Through the method of direct film spinning, carbon nanotube fiber material and carbon nanotube film material with uniform diameter can be obtained (as shown in Fig. 5 and Fig. 6). The spinnable carbon nanotube array prepared by the method can be applied to the preparation of super strong carbon nanotube fibers and carbon nanotube transparent conductive films.

The above are only specific application examples of the present invention, and do not constitute any limitation to the protection scope of the present invention. All technical solutions formed by equivalent transformation or equivalent replacement fall within the protection scope of the present invention.

Claims (7)

1. the preparation method of carbon nano tube array for spinning is characterized in that may further comprise the steps:

I, prepare oxide buffer layer on the ready-formed silicon base, metal refining catalyst film thereon again forms the carbon nano pipe array growth catalytic structure of tool composite reactive;

II, under the shielding gas environment carbon nano tube growth temperature of temperature reaction stove to 700 ℃～800 ℃;

The carbon nano pipe array growth is carried out in III, dominant discharge and ratio feeding ethene and carrier gas in Reaktionsofen under the normal pressure;

IV, wait to grow and in 1 minute, finish rapidly the growth of carbon nano pipe array after finishing.

2. the preparation method of carbon nano tube array for spinning according to claim 1, it is characterized in that: the prefabricated of silicon base described in the step I is meant at area greater than 1cm ²Silicon wafer on generate the silicon-dioxide zone of oxidation of thickness 0.1 μ m～1 μ m.

3. the preparation method of carbon nano tube array for spinning according to claim 1 is characterized in that: adopting the Assisted by Ion Beam method of evaporation to prepare thickness among the step I is the oxide buffer layer that 5nm～100nm has disordered structure; And at oxide buffer layer surface preparation thickness the metal catalytic agent film of 0.4nm～5nm iron, cobalt or nickel by electron-beam vapor deposition method.

4. the preparation method of carbon nano tube array for spinning according to claim 1, it is characterized in that: used shielding gas is rare gas element and H in the Step II ₂Mixed gas.

5. the preparation method of carbon nano tube array for spinning according to claim 1, it is characterized in that: used carbon-source gas is an ethene among the Step II I, the dividing potential drop scope of described carbon-source gas is 5%～40%.

6. the preparation method of carbon nano tube array for spinning according to claim 1 is characterized in that: the growth pattern of carbon nano pipe array described in the Step II I is the growth of normal pressure bottom.

7. the preparation method of carbon nano tube array for spinning according to claim 1, it is characterized in that: the method that finishes the carbon nano pipe array growth described in the step IV refers to and reduces carbon nano pipe array sample temperature in the Reaktionsofen, or reduces the carbon source content around the carbon nano pipe array sample.

Images