JP5546276B2 - CVD device for carbon nanotube formation - Google Patents

Description

  The present invention relates to a CVD apparatus for forming carbon nanotubes.

  Carbon nanotubes can be produced by an arc discharge method in which an arc discharge is generated between a cathode and an anode using carbon to produce carbon nanotubes, or a carbon beam mixed with a catalyst is irradiated with a laser beam to generate carbon nanotubes. There are a laser evaporation method in which carbon nanotubes are produced by evaporating and reacting with a catalyst, and a chemical vapor deposition method in which carbon nanotubes are produced through a catalyst in which hydrocarbons are decomposed at a high temperature and adhered to a substrate.

  Further, there is a chemical vapor deposition method (for example, see Patent Document 1) in which substrates are sequentially supplied to continuously generate carbon nanotubes.

JP 2005-053709 A

  By the way, in the apparatus for continuously generating the carbon nanotubes, if the steps such as pretreatment, CVD, and cooling are continuously performed, the length and orientation of the carbon nanotubes on the substrate surface vary, and the uniformity is increased. There was a problem of being inferior.

  Accordingly, an object of the present invention is to provide a CVD apparatus for forming carbon nanotubes that can generate homogeneous carbon nanotubes over the entire substrate even when the substrates are continuously supplied.

In order to solve the above-described problems, a CVD apparatus for forming carbon nanotubes according to the present invention guides a substrate on which metal catalyst particles for producing carbon nanotubes are attached, and supplies carbon by a source material gas containing carbon and heats it by a thermal CVD method. A reaction chamber in which nanotubes can be formed, a preheating chamber on the upper side of a moving path for moving the substrate to the reaction chamber, and a preheating chamber for heating the led substrate by a heating element disposed above, and a substrate; A CVD apparatus comprising a catalyst atomization chamber for heating and atomizing metal catalyst particles adhering to a predetermined temperature, and an exhaust chamber provided between the catalyst atomization chamber and the reaction chamber. And
The lower part of the substrate in the reaction chamber is partitioned into a plurality of spaces by partition walls, and gas supply ports capable of supplying a source gas containing carbon are provided in the bottom wall portions of these spaces, respectively, and these gas supply ports The supply amount of the raw material gas supplied from is increased stepwise for each space according to the growth of the carbon nanotubes ,
Further, an exhaust pipe for exhausting the air in the reaction chamber from above and reducing the pressure is provided .

  According to the configuration of the CVD apparatus, the reaction chamber in which the raw material gas is introduced into the metal catalyst particles attached to the surface of the substrate to grow carbon nanotubes is partitioned into a plurality of spaces, and the substrate is moved to these spaces. Since the supply amount of the source gas is increased from the upper side to the lower side in the direction, it is possible to supply the source gas in an amount corresponding to the degree of growth of the carbon nanotube, and accordingly, according to the growth of the carbon nanotube. Thus, it is possible to prevent the raw material gas from reaching the metal catalyst particles and the growth of the carbon nanotubes from being lowered. That is, since variation in the length and orientation of the carbon nanotubes can be prevented, homogeneous carbon nanotubes can be obtained.

  In addition, by disposing an exhaust chamber between the reaction chamber and the catalyst atomization chamber, it is possible to completely block between the two chambers, so that treatment in each chamber, that is, atomization of metal catalyst particles and raw material gas Can be reliably heated.

It is sectional drawing which shows schematic structure of the CVD apparatus for carbon nanotube formation in embodiment of this invention. It is a top view of the board | substrate in the same CVD apparatus. It is a top view of the spacer in the CVD apparatus. It is a top view of the protection sheet in the CVD apparatus. It is a graph which shows the temperature state in the board | substrate in the same CVD apparatus.

Hereinafter, a carbon nanotube forming CVD apparatus according to an embodiment of the present invention will be described based on specific examples.
In this embodiment, a carbon nanotube forming CVD apparatus using a thermal CVD apparatus will be described.

In this example, as shown in FIG. 2, as a substrate K for forming carbon nanotubes, a stainless steel thin plate material, that is, a stainless steel foil (in the case of a foil material, a thickness of about 20 to 300 μm is used, In addition, in the case of a thin steel plate, one having a thickness of about 300 μm to several mm is used. In addition, as this stainless steel foil, a long one having a predetermined width, that is, a strip-like one is used. Used. Therefore, this stainless steel foil is wound around a roll, and when forming the carbon nanotubes, the carbon nanotubes are continuously formed by being pulled out from this roll. It is intended to be wound on a roll. That is, a stainless steel foil is pulled out from one unwinding roll, carbon nanotubes are formed (generated) on the surface of the pulled-out stainless steel foil, and then the stainless steel foil on which the carbon nanotubes are formed is wound on the other winding roll. Has been. Here, the stainless steel foil will be described. Actually, a film of silicon dioxide (SiO ₂ ) is formed on both surfaces by a roll coater method or a PLD (Pulsed Laser Deposition) method, and carbon nanotubes are formed. For example, iron particles are applied (attached) as metal catalyst particles C for growing carbon nanotubes on the formation surface (the lower surface in this embodiment). The metal catalyst particles C are applied to the surface of the stainless steel foil in a shape that matches the product shape, for example, a rectangular region and at predetermined intervals.

  Hereinafter, a CVD apparatus for forming carbon nanotubes on the surface of the above-described strip-shaped stainless steel foil (hereinafter, mainly referred to as a substrate) by a thermal CVD method will be described. In the following description, the direction in which the stainless steel foil is drawn is referred to as the front-rear direction, the front side is also referred to as the lower side, and the rear side is also referred to as the upper side.

  By the way, in this CVD apparatus, as shown in FIG. 3 and FIG. 4, in order to protect the carbon nanotube formed on the lower surface of the substrate in addition to the stainless steel foil as the substrate, the strip-shaped spacer S and the strip-shaped spacer The protective sheet P is overlapped and wound around a roll. The spacer S is formed with a rectangular hole Sa that can accommodate the rectangular region, and the thickness thereof is higher than the height of the carbon nanotube to be formed.

  That is, a CVD apparatus described later includes a substrate movement path through which the substrate moves, a protection member movement path through which a spacer and a protection sheet (hereinafter collectively referred to as a protection sheet or the like) move below the substrate movement path. Will be provided. Since the carbon nanotubes are formed on the lower surface of the substrate, the substrate movement path is arranged on the upper side and the protective member movement path is arranged on the lower side.

Hereinafter, the CVD apparatus will be described in detail with reference to the drawings.
As shown in FIG. 1, the CVD apparatus includes a heating furnace 1 in which a vacuum vessel 3 is provided as an elongated processing space for forming carbon nanotubes in a furnace body 2. The inside of the vacuum vessel 3 is partitioned into a plurality of, for example, five rooms by partition walls 4 arranged at predetermined intervals, and the substrate and the protection are also provided before and after the vacuum vessel 3 in the furnace body 2. A space chamber for disposing a roll for winding a sheet or the like is provided.

  That is, in the furnace body 2, the substrate supply chamber 11 in which the unwinding roll 21 on which the stainless steel foil, that is, the substrate K is wound, is disposed, and the substrate K drawn from the unwinding roll 21 is guided and preheated. A preheating chamber 12, a catalyst atomizing chamber 13 for guiding the substrate K preheated in the preheating chamber 12 to heat and atomize the metal catalyst particles applied to the surface, and a catalyst atomizing chamber 13 on the lower side An exhaust chamber 14 disposed, a substrate K disposed on the lower side of the exhaust chamber 14 and in which the metal catalyst particles are atomized in the catalyst atomization chamber 13 and a raw material gas (described later) are guided to heat the metal catalyst particles. A reaction chamber 15 for growing and forming carbon nanotubes thereon, and a substrate K on which the carbon nanotubes are formed in the reaction chamber 15 are guided and cooled by, for example, a cooling roll 16a. And a substrate recovery chamber (also referred to as a product recovery chamber) 17 in which a winding roll 22 for winding the substrate K cooled in the post-processing chamber 16 is disposed. . In addition, except for the substrate supply chamber 11 and the product recovery chamber 17, that is, at least the preheating chamber 12, the catalyst atomization chamber 13, the exhaust chamber 14, the reaction chamber 15, and the post-treatment chamber 16 are provided in the vacuum vessel 3. .

  In the substrate supply chamber 11, a spacer roll 23 and a protective sheet roll 24 around which the spacer S and the protective sheet P are wound are disposed in addition to the unwinding roll 21 of the substrate K. In the substrate recovery chamber 17, since the spacer S and the protective sheet P are taken up together with the substrate K, only the take-up roll 22 for the substrate K described above is disposed.

  In addition, at the place where the substrate K, the spacer S, and the protective sheet P (hereinafter collectively referred to as the substrate etc. K ′) are introduced into the vacuum vessel 3, the substrate etc. K ′ is maintained while keeping the airtightness in the vacuum vessel 3. An introduction member 25 comprising a pair of upper and lower introduction rollers 25a capable of guiding the substrate is disposed, and the substrate etc. K 'is kept at the outlet position of the substrate etc. K' in the vacuum vessel 3 while maintaining the airtightness in the vacuum vessel 3. A lead-out member 26 comprising a pair of upper and lower lead-out rollers 26a that can be guided is disposed. A guide roller 27 and a protective sheet P ′ for guiding the substrate K to the upper substrate movement path M1 are guided to the lower protection member movement path M2 at the front portion in the vacuum vessel 3. Further, guide rollers 29 and 30 for guiding the substrate K and the protective sheet P ′ between the two guide rollers 26a are arranged at the rear of the vacuum vessel 3. ing.

  By the way, the preheating chamber 12, the catalyst atomization chamber 13, and the reaction chamber 15 only need to have a space that allows the substrate K to pass therethrough and perform predetermined processing. 32 and 33 are provided, and the space below the bottom wall portions 31, 32, and 33 of the chambers 12, 13, and 15 is a passage space portion through which a protective sheet or the like P 'can pass. In addition, the board | substrate K which passes each chamber 12-15 moves in the horizontal surface.

Since the preheating chamber 12, the catalyst atomization chamber 13 and the reaction chamber 15 are heated, heating means are arranged respectively.
That is, in the space provided between the upper wall portion 3a of the vacuum vessel 3 and the upper wall portion 2a of the furnace body 2, a plurality of columnar shapes (bar-like shapes) are formed according to the chambers 12, 13, and 15, respectively. Heating devices 41a, 42a, 43a that generate heat by emitting electrical resistance and emit infrared rays, a power source that supplies electricity to these heating members 41a, 42a, 43a, and a temperature control unit thereof, 42, 43 are arranged, and quartz windows 44, 45, 46 through which infrared rays radiated from the heating elements 41a, 42a, 43a can pass are arranged on the upper walls of the chambers 12, 13, 15 respectively. Has been.

  Although it does not specifically limit as said heat generating body 41a, 42a, 43a, For example, a non-metallic resistance heat generating body is used, for example, silicon carbide, molybdenum silicide, lanthanum chromite, zirconia, graphite etc. are used. In addition, infrared reflectors 47, 48, and 49 are disposed above the heating elements 41a, 42a, and 43a, respectively, so that the infrared rays emitted upward are reflected to the chambers 12, 13, and 15, respectively. Yes.

  Next, the preheating chamber 12 and the catalyst atomization chamber 13 will be briefly described. In the preheating chamber 12, the guided substrate K is heated to a predetermined temperature (for example, about 300 ° C.) by the heating element 41a disposed above. Then preheating is performed. Further, an inert gas supply pipe 51 capable of supplying an inert gas [for example, helium gas (He)] N is connected to the bottom wall portion 32 of the catalyst atomization chamber 12, and the atmosphere of the inert gas Under the heating element 42a, the metal catalyst particles (here, iron particles are used) are atomized by being heated to a high temperature of about 700 to 900 ° C., for example.

Next, the reaction chamber 15 will be described in detail.
In the reaction chamber 15, a raw material gas containing carbon (also referred to as a reaction gas, for example, acetylene gas, ethane gas, or ethylene gas is used) G is supplied from below, but in this embodiment, the supply gas is supplied. The amount is changing by location. For example, the supply amount is increased sequentially from the upper side to the lower side in three stages.

  That is, two partition members 61 having a predetermined height are provided at a predetermined interval on the bottom wall portion 33 of the reaction chamber 15, and the interior thereof includes the first reaction space portion 15 a, the second reaction space portion 15 b, and the first reaction space portion 15. Source gas supply pipes 52, 53, and 54 for supplying source gases are connected to the bottom wall 33 corresponding to each of the spaces 15a to 15c. (In other words, a connection port for the source gas is provided). The amount of source gas supplied to each source gas supply pipe 52, 53, 54 is automatically controlled by a control device (not shown), and the heating elements 41a, 42a, 43a are also automatically controlled. The temperature is controlled. FIG. 5 shows the temperature distribution of the substrate K in each of the chambers 12, 13, 15 [(A) to (D) indicate positions corresponding to the positions in the vacuum vessel 3 shown in FIG. 1]. deep.

  In the reaction chamber 15, carbon nanotubes are formed (generated) by thermal CVD, but when the carbon nanotubes are formed, the inside is maintained in a predetermined vacuum degree (negative pressure state). In an appropriate place of the reaction chamber 15, for example, the partition wall 4 is connected to an exhaust pipe 55 for discharging the air in the reaction chamber 15 to make a predetermined reduced pressure (under vacuum). Of course, an exhaust device (not shown) such as a vacuum pump is connected to the exhaust pipe 55. The reduced pressure value (degree of vacuum) of the reaction chamber 15 is maintained in the range of several Pa to 1000 Pa. For example, it is maintained at several tens Pa to several hundred Pa. The lower limit of the reduced pressure range of several Pa is a limit value for maintaining the carbon nanotube formation rate (deposition rate), and the upper limit of 1000 Pa is a limit value in terms of soot and tar suppression. is there.

  Further, the exhaust chamber 14 is configured such that the internal air is always discharged in order to prevent the raw material gas G in the reaction chamber 15 from flowing into the catalyst atomization chamber 13. An exhaust pipe 56 connected to a vacuum pump (not shown) is inserted into the chamber 14 from the vacuum vessel 3 and the bottom wall portions 3 b and 2 b of the furnace body 2. In order to prevent the raw material gas G from flowing into the catalyst atomization chamber 13, the flow rate of the inert gas N supplied into the catalyst atomization chamber 13 is increased and the pressure is set higher than that in the reaction chamber 15. In addition, the raw material gas leaked from the reaction chamber 15 is discharged from the exhaust chamber 14 without flowing into the catalyst atomization chamber 13 by maintaining the height higher.

  In the vacuum vessel 3, five chambers are formed by the partition walls 4. Naturally, each partition wall 4 has a communication opening (also referred to as a slit) 4 a through which the substrate K can pass. Is formed.

  By the way, stainless steel is used as a constituent material of the vacuum vessel 3. That is, since the walls of the chambers 12 to 15 are made of stainless steel, radiation heat from infrared rays is blocked, so that conventional heat insulating materials such as ceramic fibers and glass fibers are not necessary. Mixing and accumulation can be suppressed.

  Further, as the substrate K, a stainless steel foil rolled into a coil shape and rolled to a thickness of 20 to 300 μm or less is used. In such a substrate K, a residual tensile force in the coil winding direction is used. Since the stress exists, the substrate K warps due to the release of the residual stress during atomization of the metal catalyst particles and thermal CVD. In order to prevent the occurrence of such warping, a mechanism for applying tension in the coil winding direction, specifically, tension is generated between the unwinding roll 21 and the winding roll 22 (for example, both rolls The tension is generated by varying the rotation speed of the motor.Specifically, the tension may be generated by one motor, and the other motor may exhibit a brake function.) The substrate K may be pulled. Further, a weight may be provided on the winding roll 22 side and pulled.

Next, a method for forming carbon nanotubes using the CVD apparatus will be described.
First, the substrate K is pulled out from the unwinding roll 21, and inserted into the communication openings 4a of the partition walls 4 in the preheating chamber 12, the catalyst atomization chamber 13, the exhaust chamber 14, the reaction chamber 15, and the post-treatment chamber 16, that is, The leading end is wound around the winding roll 22 along the substrate movement path M1. At this time, tension is applied to the substrate K so that the substrate K becomes a straight horizontal plane.

  As with the substrate K, the spacer S and the protection sheet P are guided along the protection member moving path M2 from the leading roller 25a to the leading roller 26a, and then wound around the winding roller 22. Make it.

  Thereafter, the reaction chamber 15 is maintained in a range of, for example, several Pa to 1,000 Pa, specifically, several tens Pa to several hundred Pa as described above under a predetermined reduced pressure by the exhaust device via the exhaust pipe 55. Is done. Along with this, air is also discharged in the exhaust chamber 14 and maintained under reduced pressure together with the catalyst atomization chamber 13, and the inert gas N is supplied to the catalyst atomization chamber 13 to be inert. Under a gas atmosphere.

Then, each of the chambers 12, 13, and 15 is heated to a preset temperature by the heating elements 41a, 42a, and 43a, respectively.
In this state, each roll is rotated to slowly move the substrate etc. K ′ from the lower side to the upper side.

  That is, the substrate K having the lower surface coated with iron particles as metal catalyst particles C is preheated in the preheating chamber 12 and then moved to the catalyst atomization chamber 13 where it is heated to a predetermined temperature, for example, 800 ° C. Atomization (miniaturization) is performed.

When atomization is performed, the substrate is moved to the reaction chamber 15 via the exhaust chamber 14, where, for example, acetylene gas (C ₂ H ₂ ) is supplied as the source gas G to perform a predetermined reaction, thereby causing a substrate. Carbon nanotubes CNT are generated (grown) on the iron particles, which are the metal catalyst particles C attached to the lower surface of K (see FIG. 2).

  By the way, the reaction chamber 15 is divided into three reaction spaces, and in the first first reaction space 15a, the raw material gas is supplied with a small supply amount to generate carbon nanotubes. When the gas moves to the second reaction space 15b, the raw material gas is supplied in a larger amount, the carbon nanotubes are further grown, and when the carbon nanotube is moved to the third reaction space 15c, a larger amount of the raw material gas is obtained. Is supplied to further grow the carbon nanotubes.

  Thus, since the supply amount of the source gas G is increased in three stages, even if it becomes difficult for the source gas to reach the surface of the substrate K as the carbon nanotube grows, it is sufficient in each place. Since the raw material gas can be supplied, and the carbon nanotubes can be formed efficiently and uniformly, a good quality product can be obtained.

Thereafter, the substrate K on which the carbon nanotubes are formed is moved into the post-processing chamber 16 and cooled by the cooling roll 16a.
When the cooling is completed, the substrate K is moved into the product collection chamber 17 with the spacer S and the protective sheet P moved from below by the guide roller 26a. Of course, the carbon nanotubes formed on the surface of the substrate K are inserted into the holes Sa formed in the spacer S, and the surface is covered with the protective sheet P to be completely protected. Then, the substrate K protected by the protective sheet P ′ or the like is taken up by the take-up roll 22 and collected as a product. When all the substrates K on which the carbon nanotubes are formed are taken up by the take-up roll 17, they are taken out to the outside.

  According to the configuration of the thermal CVD apparatus, the reaction chamber in which the raw material gas is introduced into the metal catalyst particles attached to the surface of the substrate and the carbon nanotubes are grown is partitioned into a plurality of reaction spaces, and in these reaction spaces, Since the supply amount of the source gas is increased from the upper side to the lower side in the movement direction of the substrate, an amount of the source gas corresponding to the growth degree of the carbon nanotube can be supplied. According to the growth, it is possible to prevent the raw material gas from reaching the metal catalyst particles so that the growth of the carbon nanotube is reduced. That is, since variation in the length and orientation of the carbon nanotubes can be prevented, homogeneous carbon nanotubes can be obtained.

  Also, by disposing an exhaust chamber between the reaction chamber and the catalyst atomization chamber, it is possible to completely block between the two chambers, so that processing in each chamber, that is, atomization of metal catalyst particles and raw material gas Can be reliably heated.

  Further, according to the configuration of the thermal CVD apparatus, when the substrate is introduced into the reaction chamber and the raw material gas is introduced to form carbon nanotubes on the surface, the substrate wound on the unwinding roll is wound on the winding roll. Since the carbon nanotubes are formed on the surface of the substrate in the middle, the carbon nanotubes can be continuously formed on the substrate, and therefore, compared with the case of forming the carbon nanotubes in batch mode. Thus, carbon nanotubes can be formed efficiently.

  Further, since the heating element is disposed on the upper surface side opposite to the carbon nanotube formation surface of the substrate, the reaction of the raw material gas is performed smoothly. This is because the heating element directly warms the substrate and gas is supplied from the surface opposite to the heating element, so that the gas is supplied first to the substrate and gas decomposition occurs in the vicinity of the substrate. When the gas passes through the heating element, soot is easily generated in the vicinity of the gas and the temperature changes from a high temperature to a low temperature, and at the same time, carbon supplied to the substrate is reduced.

By the way, in the said Example, although the reaction chamber was divided into three, it is not limited to three, For example, you may divide into two or four or more.
Moreover, in the said Example, although each heat generating body was arrange | positioned on the outer side of each chamber, ie, the outer side of the vacuum vessel, you may arrange | position each inside.

K substrate S spacer P protective sheet 1 heating furnace 2 furnace body 3 vacuum vessel 4 partition wall 11 substrate supply chamber 12 preheating chamber 13 catalyst atomization chamber 14 exhaust chamber 15 reaction chamber 15a first reaction space portion 15b second reaction space portion 15c Third reaction space 16 Post-processing chamber 17 Substrate recovery chamber 21 Unwinding roll 22 Winding roll 23 Spacer roll 24 Sheet rolls 41 to 43 Heating devices 41a to 43a Heating elements 52 to 54 Source gas supply pipe 55 Exhaust pipe 61 Partition material

Claims (1)

A reaction chamber in which carbon nanotubes can be formed by a thermal CVD method that guides a substrate on which metal catalyst particles for producing carbon nanotubes are adhered and supplies and heats a source gas containing carbon, and a movement path for moving the substrate into the reaction chamber On the upper side, a preheating chamber for heating the led substrate by a heating element disposed above to preheat, and metal catalyst particles attached to the substrate for heating to a predetermined temperature for atomization A CVD apparatus comprising a catalyst atomization chamber and an exhaust chamber provided between the catalyst atomization chamber and the reaction chamber ,
The lower part of the substrate in the reaction chamber is partitioned into a plurality of spaces by partition walls, and gas supply ports capable of supplying a source gas containing carbon are provided in the bottom wall portions of these spaces, respectively, and these gas supply ports The supply amount of the raw material gas supplied from is increased stepwise for each space according to the growth of the carbon nanotubes ,
Furthermore, a CVD apparatus for forming carbon nanotubes is provided, wherein an exhaust pipe for exhausting the air in the reaction chamber from above and reducing the pressure is provided .

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