JP2013006708A - Method for producing carbon nanotube film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a carbon nanotube film having excellent reproducibility, capable of spinning stably a carbon nanotube.SOLUTION: A metal catalyst is deposited on the surface of a planar substrate, and then the atmosphere of the substrate is changed as shown in Fig.1, to thereby produce a carbon nanotube film on the surface of the substrate. Namely, the atmosphere of the substrate is replaced with hydrogen gas, and the temperature of the substrate and its atmosphere is raised up to 500°C which is a metal catalyst activation temperature, and kept at the temperature for 3 minutes. Successively, the temperature of the substrate and its atmosphere is lowered to 200-500°C, and hydrocarbon gas is introduced into the atmosphere of the substrate. Then, after keeping the temperature of the substrate and its atmosphere as it is for 0-3 minutes, the temperature of the substrate and its atmosphere is raised up to 700°C which is a CNT synthesis temperature. The temperature of the substrate and its atmosphere is kept at 700°C for 10 minutes, while introducing the hydrocarbon gas therein, to thereby form a carbon nanotube film.

Description

  The present invention relates to a method for producing a carbon nanotube film made of carbon nanotubes, and more particularly, to a method for producing a carbon nanotube film capable of spinning carbon nanotubes constituting the carbon nanotube film in a rope shape.

  Conventionally, it has been proposed that a carbon nanotube film made of carbon nanotubes is formed on the surface of a substrate, and a part of the carbon nanotube film is pulled out by tweezers to spin the carbon nanotubes in a rope shape (for example, patents) References 1 and 2). Here, in patent document 1, after annealing the board | substrate with which the metal catalyst was vapor-deposited at 300-400 degreeC for 10 hours, the board | substrate is heated in inert gas at 500-700 degreeC, and hydrocarbon gas is introduce | transduced further. Thus, a carbon nanotube film is manufactured. Further, in Patent Document 2, a carbon nanotube film is manufactured by heating a substrate on which a metal catalyst film is formed at 700 ° C. in an inert gas and further introducing a hydrocarbon gas.

JP 2004-107196 A Japanese Patent No. 4512750

  However, none of the methods described in the above patent documents has reproducibility. In other words, in the experiment conducted by the applicant of the present application, the carbon nanotube film produced under the conditions described in the above patent documents could not be spun or could not be spun. Therefore, the present invention has been made for the purpose of providing a method for producing a carbon nanotube film that has good reproducibility and can stably spin carbon nanotubes.

  The carbon nanotube film manufacturing method of the present invention made to achieve the above object includes a first step of depositing a metal catalyst on a substrate, and the substrate after the metal catalyst is deposited in an inert atmosphere or a reducing atmosphere. A second step of activating and aggregating the metal catalyst by heating, a third step of depositing amorphous carbon on the surface of the activated and agglomerated metal catalyst and the substrate, and depositing the amorphous carbon And a fourth step of forming carbon nanotubes on the substrate by vapor phase synthesis.

  In the method of the present invention thus configured, the metal catalyst is deposited on the substrate in the first step, and the substrate after the metal catalyst deposition is heated in an inert atmosphere or a reducing atmosphere in the second step. By doing so, the metal catalyst is activated and aggregated. Here, the deposition of the metal catalyst in the first step can be performed by various known methods such as sputtering and vapor deposition. The second step can be performed by heating the substrate after the metal catalyst deposition in a known inert atmosphere or reducing atmosphere such as a hydrogen gas atmosphere or a helium gas atmosphere. The conditions are preferably set so that the agglomerated metal catalyst has a diameter of several nanometers.

  The applicant of the present invention forms carbon nanotubes after depositing amorphous carbon (third step) instead of forming carbon nanotubes directly on the surface of the activated and aggregated metal catalyst and the substrate. I found a good thing. Thus, carbon nanotubes are stabilized from the obtained carbon nanotube film by forming carbon nanotubes by vapor phase synthesis (CVD) on the substrate on which amorphous carbon has been deposited (fourth step). Can be spun into a rope. Moreover, good reproducibility was found in such experiments.

  In the second step, the substrate after the metal catalyst deposition is heated to a metal catalyst activation temperature or higher in an inert atmosphere or a reducing atmosphere, and in the third step, the substrate after the heating is heated. The substrate is held at a temperature lower than the metal catalyst activation temperature in an atmosphere containing a carbon source gas. In the fourth step, the substrate is held at a temperature higher than the metal catalyst activation temperature in an atmosphere containing a carbon source gas. Is preferred. That is, in the third step, by maintaining the heated substrate at a temperature lower than the metal catalyst activation temperature in an atmosphere containing a carbon source gas, amorphous carbon is satisfactorily formed on the surface of the substrate and the metal catalyst. Can be deposited. Thus, although the principle of depositing amorphous carbon below the metal catalyst activation temperature is unknown, the experiment showed good reproducibility.

  In that case, in the third step, it is more preferable to maintain the heated substrate at 200 ° C. or higher and the metal catalyst activation temperature or lower in an atmosphere containing a carbon source gas. Even more preferably, in the third step, after the end of the second step, the temperature of the substrate is lowered below the metal catalyst activation temperature, and then the carbon source gas is introduced into the atmosphere of the substrate. By doing so, amorphous carbon can be deposited more favorably on the surface of the substrate and the metal catalyst.

  In the third step, it is preferable to hold the substrate at the metal catalyst activation temperature or lower for 0 to 180 seconds. Even when the temperature is kept below the metal catalyst activation temperature for 0 second, it is considered that the deposition of amorphous carbon occurs while the substrate is heated from that state to a temperature suitable for the vapor phase synthesis method.

It is explanatory drawing showing the outline | summary of the carbon nanotube film | membrane manufacturing process of this invention application. It is explanatory drawing which represents the manufacturing process typically. It is explanatory drawing showing the manufacturing process of the carbon nanotube film | membrane of 1st Example. It is a photograph showing the spinning result from the carbon nanotube film. It is explanatory drawing showing the manufacturing process of the carbon nanotube film | membrane of 2nd Example. It is an electron micrograph showing deposition of amorphous carbon in a reference example. It is explanatory drawing showing the manufacturing process of the carbon nanotube film | membrane in a comparative example.

[Outline of Embodiment]
Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram showing an outline of a carbon nanotube film manufacturing process as an embodiment to which the present invention is applied. Moreover, FIG. 2 is explanatory drawing which represents the manufacturing process typically.

  In the present embodiment, first, a flat substrate 1 is prepared as illustrated in FIG. 2A, and a metal catalyst 3 is deposited on the surface of the substrate 1 as illustrated in FIG. 1 step). Subsequently, the atmosphere of the substrate 1 was changed as shown in FIG. 1 to manufacture a carbon nanotube film 10 (see FIG. 2) on the surface of the substrate 1.

  That is, as shown in FIG. 1, the atmosphere of the substrate 1 was replaced with hydrogen gas, and the temperature of the substrate 1 and the atmosphere was raised to 500 ° C. as the metal catalyst activation temperature and held at that temperature for 3 minutes. By this step (second step), it is presumed that the metal catalyst 3 deposited on the substrate 1 is activated and aggregated into particles having a diameter of several nm as illustrated in FIG. 2C. .

  Subsequently, the temperature of the substrate 1 and its atmosphere was lowered to 200 to 500 ° C., and a hydrocarbon gas (an example of a carbon source gas) was introduced into the atmosphere of the substrate 1. And after hold | maintaining the board | substrate 1 and its atmosphere at the temperature for 0 to 3 minutes, the board | substrate 1 and its atmosphere were heated up to 700 degreeC as CNT synthesis | combination temperature (temperature suitable for a gaseous-phase synthesis method). As shown in FIG. 2D, the surface of the substrate 1 on which the agglomerated metal catalyst 3 and the metal catalyst 3 are deposited (upper surface) is formed by this low temperature holding and temperature rising step (third step). ), It is presumed that amorphous carbon 5 is deposited. The validity of this estimation has been verified as will be described later.

  Subsequently, the substrate 1 and its atmosphere were held at 700 ° C. for 10 minutes while introducing hydrocarbon gas. By this step (fourth step), as illustrated in FIG. 2E, the carbon nanotubes 7 are formed on the surface of the substrate 1 by the vapor-phase synthesis method and are erected to form a carbon nanotube film composed of a large number of carbon nanotubes 7. 10 was formed. Finally, the atmosphere of the substrate 1 after the carbon nanotube film 10 was formed was replaced with hydrogen gas, and after the substrate 1 and the atmosphere were cooled to room temperature, the substrate 1 on which the carbon nanotube film 10 was formed could be taken out. .

Specific examples will be described below.
[First embodiment]
A silicon substrate with a 30-nm thermal oxide film (a SUMCO 6-inch silicon (100) wafer cut into a 20 mm square) with a 15 nm alumina film formed by sputtering is used as the substrate. A metal catalyst was formed by sputtering at 5 nm. This substrate was placed in a reduced pressure CVD apparatus (BlackMagic manufactured by Ixtron), and after evacuation, hydrogen was introduced, the temperature was raised to 500 ° C. at a pressure of 9.6 hPa, and this temperature was maintained for 3 minutes. Next, the substrate temperature was lowered to 400 ° C., acetylene gas (an example of a carbon source gas and a hydrocarbon gas) was introduced into the hydrogen gas atmosphere, and the pressure was maintained at 8.5 hPa for 0 second. Subsequently, the carbon nanotubes were synthesized by raising the temperature to 700 ° C., which is the CNT synthesis temperature, at a heating rate of 300 ° C./min and holding for 10 minutes. The synthesis was stopped by stopping the acetylene gas, and the energization to the heater of the CVD apparatus was stopped to cool. FIG. 3 shows the relationship between time, temperature, and processing atmosphere in the manufacturing process of the first embodiment.

  The spinnability of the carbon nanotube film 10 of the first example obtained by the above steps was good. That is, as shown in FIG. 4, when the carbon nanotubes 7 (see FIG. 2) are pulled out by contacting the surface of the carbon nanotube film 10 with a pull-out tape 50 having a pattern on a double-sided tape, the fibers are spun into a rope shape. A spun yarn 99 was obtained. Also, good reproducibility was seen in this experiment.

[Second Embodiment]
After the activation of the metal catalyst in the second step, the substrate temperature was lowered to 300 ° C. and acetylene gas was introduced and held for 10 seconds (third step). Other steps are the same as those in the first embodiment. FIG. 5 shows the relationship between time, temperature, and processing atmosphere in the manufacturing process of the second embodiment. The spinnability of the carbon nanotube film thus obtained was good, and good reproducibility was seen in the experiment.

[Third embodiment]
After activation of the metal catalyst in the second step, acetylene gas is introduced while maintaining the substrate temperature at 500 ° C. (third step), and the holding time until the temperature is raised next is changed from 10 seconds to 3 minutes. Carbon nanotubes were synthesized. The spinnability of the carbon nanotube film thus obtained was good, and good reproducibility was seen in the experiment.

[Reference example]
In addition, in order to verify that amorphous carbon is deposited on the substrate surface by the third step of each of the above embodiments, that is, the step of introducing acetylene gas while maintaining the substrate temperature at a low temperature of 300 to 500 ° C. The person conducted the following experiment. That is, after activation of the metal catalyst, acetylene gas was introduced while maintaining the substrate temperature at 350 ° C., and after maintaining for 3 minutes, the substrate was taken out without raising the temperature to the CNT synthesis temperature. The result of observing the substrate with an electron microscope is shown in FIG. As shown in FIG. 6, it can be seen that the surface of the substrate is covered with amorphous carbon.

  From this experiment, it was verified that amorphous carbon was deposited on the substrate surface in the third step of each of the above examples. Next, a carbon nanotube film was produced by a production method as a comparative example not including this third step, and the spinnability was examined.

[First comparative example]
After the activation of the metal catalyst in the second step, the substrate temperature was raised to 600 ° C., acetylene gas was introduced, and held for 10 seconds. Other steps are the same as those in the first embodiment. The spinnability of the carbon nanotube film thus obtained was poor.

[Second Comparative Example]
After activation of the metal catalyst in the second step, the substrate temperature was raised to 700 ° C. as it was, and acetylene gas was introduced to synthesize carbon nanotubes. The spinnability of the carbon nanotube film thus obtained was poor.

[Third comparative example]
Without activating the metal catalyst in the second step, acetylene gas was introduced while maintaining the substrate temperature at 400 ° C., held for 10 seconds, and then heated to 700 ° C. to synthesize carbon nanotubes. The spinnability of the carbon nanotube film thus obtained was poor.

[Fourth Comparative Example]
This is a manufacturing method similar to that of Patent Document 1 described above. That is, after annealing the substrate on which the metal catalyst was deposited at 300 to 400 ° C. for 10 hours, the substrate was heated to 500 to 700 ° C. in an inert gas to further introduce acetylene, thereby producing a carbon nanotube film. . FIG. 7A shows the relationship between time, temperature, and processing atmosphere in the manufacturing process of the fourth comparative example. The carbon nanotube film obtained in this way could not be spun and its characteristics were unstable.

[Fifth Comparative Example]
This is a manufacturing method similar to that of Patent Document 2 described above. That is, the carbon nanotube film was manufactured by heating the substrate on which the metal catalyst was deposited to 700 ° C. in an inert gas and further introducing acetylene. FIG. 7B shows the relationship between time, temperature, and processing atmosphere in the manufacturing process of the fifth comparative example. The carbon nanotube film thus obtained could not be spun.

  As described above, it was found that the carbon nanotube film produced by the method of the present invention can spin carbon nanotubes stably and has good reproducibility. In addition, this invention is not limited to the said embodiment and Example at all, In the range which does not deviate from the summary of this invention, it can implement with a various form. For example, if the type of metal catalyst is changed, the metal catalyst activation temperature may also change. The second step may be performed in an inert atmosphere such as helium gas instead of the reducing atmosphere using hydrogen gas as described above. Furthermore, an appropriate CNT synthesis temperature also changes depending on the carbon source gas used. That is, the first step, the second step, and the fourth step of the embodiment may be replaced with the corresponding steps in the known carbon nanotube film manufacturing method.

DESCRIPTION OF SYMBOLS 1 ... Substrate 3 ... Metal catalyst 5 ... Amorphous carbon 7 ... Carbon nanotube 10 ... Carbon nanotube film 50 ... Drawer tape 99 ... Spinning yarn

Claims (5)

A first step of depositing a metal catalyst on a substrate;
A second step of activating and agglomerating the metal catalyst by heating the substrate after the metal catalyst deposition in an inert atmosphere or a reducing atmosphere;
A third step of depositing amorphous carbon on the surface of the substrate after the activation and aggregation;
A fourth step of forming carbon nanotubes by vapor phase synthesis on the substrate on which the amorphous carbon is deposited;
A method for producing a carbon nanotube film, comprising: In the second step, the substrate after the metal catalyst deposition is heated to a metal catalyst activation temperature or higher in an inert atmosphere or a reducing atmosphere,
In the third step, the heated substrate is maintained at a temperature lower than the metal catalyst activation temperature in an atmosphere containing a carbon source gas,
2. The method of manufacturing a carbon nanotube film according to claim 1, wherein in the fourth step, the substrate is held at a temperature higher than the metal catalyst activation temperature in an atmosphere containing a carbon source gas.   3. The carbon nanotube film according to claim 2, wherein in the third step, the heated substrate is held at 200 ° C. or more and the metal catalyst activation temperature or less in an atmosphere containing a carbon source gas. Production method.   The said 3rd process WHEREIN: After completion | finish of the said 2nd process, after cooling the said board | substrate below the said metal catalyst activation temperature, carbon source gas is introduce | transduced into the atmosphere of the said board | substrate. Of manufacturing a carbon nanotube film.   5. The method of manufacturing a carbon nanotube film according to claim 2, wherein, in the third step, the substrate is held below the metal catalyst activation temperature for 0 to 180 seconds.