JP4456442B2 - Method for producing carbon nitride - Google Patents

Description

The present invention relates to a method for producing carbon nitride (sometimes referred to as nitrogen carbide), and more particularly, to a method for producing high-performance carbon nitride (CN _x ) easily and inexpensively.

Since carbon nitride (CN _x ) can be used for abrasives due to its rigidity, and for electronic devices (for example, fields called nanoelectronics) due to its semiconductivity, carbon nitride (CN _x ) Various manufacturing methods have been studied.
As such a method for producing carbon nitride (CN _x ), ion implantation, sputtering, plasma synthesis, and the like are already known.

  For example, Patent Document 1 states that “a pair of graphite electrodes is housed in a vacuum vessel, and a pinch plasma is generated in a state where nitrogen gas is allowed to flow through the gap between the pair of electrodes. It is disclosed that a carbon nitride compound film is formed on a substrate regardless of the material of the substrate by “a method for producing a carbon nitride compound characterized by being formed on top” (see Patent Document 1).

  Patent Document 2 states that “a raw material gas 7 containing a cyanide compound such as brominated cyanide and iodine cyanide is activated by turning it into a plasma 10 and placed in the plasma or downstream of the gasified gas 20. The carbon nitride film 21 is synthesized on the base 5 biased to a negative voltage, which is a self-bias by the high frequency 16 and / or a bias by the DC voltage 6. Alternatively, the ratio of hydrogen atoms in the source gas is 5 % Or less, or a part or all of the moisture content is supplied into the reaction tanks 1 and 2 through the moisture absorbents 8 and 8. The source gas is provided downstream of the rare gas 11 and the nitrogen-containing gas plasma. Further, the ratio of the flow rate of the cyanide gas to the total gas flow rate is 1 to 100%, and the flow rate ratio of nitrogen gas and rare gas is 0 to 80%. Discloses the synthesizing carbon nitride film on the substrate (see Patent Document 2).

  Further, Non-Patent Document 1 discloses that carbon nitride having a small particle diameter is generated in graphite by injecting nitrogen atoms into the graphite (at room temperature).

JP 2001-59156 A (Claim 1, paragraph number 0009) JP 2002-38269 A (Solution means in summary) Kazuhiro Yamamoto, Yoshinori Koga, Kiyoshi Yase, Shuzo Fujiwara, Masaaki Kubota (Kazuhiro Yamamoto, Yoshiri Kaga, Kiyoshi Yase, Shuzo Fujiwara and Masaaki Kubota) of Cubic Phase Carbon Nitride Solid by Low Energy Nitrogen Implantation into Graphite, European Journal of Applied Physics 36, L230-L233, 1997 (Jpn. J. Appl. Ph. L. Part 2, No. 2B, 15 February 997)

However, in the conventional carbon nitride manufacturing methods as shown in Patent Document 1, Patent Document 2, and Non-Patent Document 1, thin-film carbon nitride can be obtained (Patent Document 1, Patent Document 2), or other than carbon nitride. In a state of being supported in the matrix (that is, a part of what is physically integrated is carbon nitride, but the other part (part other than the part) is not carbon nitride.) In the invention disclosed in Document 1, carbon nitride having a small particle size is supported in a graphite matrix other than carbon nitride.) Although carbon nitride is obtained, it is possible to obtain a powder of carbon nitride. Can not.
In particular, when carbon nitride is used for the above-mentioned uses (electronic devices such as abrasives and semiconductors), etc., carbon nitride of powder (powder) that is not supported in a matrix other than carbon nitride (ie, Since one powder constituting the powder is made of carbon nitride), it is easier to use and handle, so a method for producing carbon nitride of such powder is required.

  Therefore, in the present invention, carbon nitride of a powder (powder) that is not in a state of being supported in a matrix other than carbon nitride (that is, the entire powder of one powder constituting the powder contains carbon nitride (inevitable impurities). It is an object of the present invention to provide a manufacturing method of

  The method for producing carbon nitride of the present invention (hereinafter referred to as “the present method”) comprises bringing a carbon-containing material containing carbon into contact with nitrogen plasma generated by radiating a predetermined microwave to nitrogen gas. This is a method for producing carbon nitride.

In addition, the method includes the following aspects (1) to (9).
(1) Before generating the nitrogen plasma, a predetermined microwave is emitted to the argon gas to generate the argon plasma, and the nitrogen gas is replaced with the nitrogen gas to generate the nitrogen plasma. The above manufacturing method.
(2) The manufacturing method according to (1), wherein a spark discharge that assists generation of the argon plasma is generated in the argon gas when the argon plasma is generated.
(3) The said manufacturing method which produces a spark discharge from the surface of the said carbon containing material in the said nitrogen plasma.
(4) The said manufacturing method whose said carbon containing material is formed with a graphite.
(5) The said manufacturing method whose said carbon containing material is formed with a rod-shaped member.
(6) The said manufacturing method which converts flowing nitrogen gas into the said nitrogen plasma, and the volume velocity of nitrogen gas is 0.1-3.0 liter / (min * mm < ² >).
(7) The manufacturing method according to (6), wherein a collecting member that collects the produced carbon nitride by adhering to the surface is disposed on the downstream side of the flowing nitrogen gas.
(8) The said manufacturing method which arrange | positions the collection member which makes the produced carbon nitride adhere to the surface, and is arrange | positioned under the said carbon containing material.
(9) The said manufacturing method whose said predetermined microwave is a frequency of 0.8-100 GHz.

  Then, the present invention provides powdery carbon nitride in which the whole of one powder constituting the powder is formed of carbon nitride and inevitable impurities, and the average particle size is 1 micrometer or less.

The method for producing carbon nitride of the present invention (hereinafter referred to as “the present method”) comprises bringing a carbon-containing material containing carbon into contact with nitrogen plasma generated by radiating a predetermined microwave to nitrogen gas. This is a method for producing carbon nitride.
Nitrogen plasma (atomic form) is generated by radiating a predetermined microwave to nitrogen gas. Since generating a nitrogen plasma by radiating a microwave to nitrogen gas is a known technique, a detailed description is omitted here.
By bringing the carbon-containing material into contact with the nitrogen plasma generated in this manner, in this method, carbon nitride (that is, powder) of powder (powder) that is not supported in a matrix other than carbon nitride is used. The whole powder of the constituent 1 is formed of carbon nitride and inevitable impurities).
The carbon nitride produced by this method can be used as an abrasive due to its hardness as in the case of conventional carbon nitride, and it can be used as an abrasive due to its semiconductivity (for example, called nanoelectronics). Field).

Before generating the nitrogen plasma, a predetermined microwave is emitted to the argon gas to generate the argon plasma, and the nitrogen gas is replaced with the nitrogen gas to generate the nitrogen plasma (hereinafter referred to as “argon”). It may be referred to as “a plasma pre-generation method”.
Before the nitrogen plasma is generated in this way, a predetermined microwave is radiated to the argon gas to generate the argon plasma, and then the nitrogen gas is replaced with the nitrogen gas, so that the nitrogen plasma can be generated stably. Therefore, the present method can be carried out easily and stably.

In the case of the argon plasma pre-generation method, a spark discharge that assists the generation of the argon plasma may be generated in the argon gas when the argon plasma is generated.
By doing this, the energy necessary for the generation of the argon plasma can be given to the argon gas by spark discharge, so that the argon plasma can be generated easily and stably, making the method easier and more stable. Can be implemented.
The method for generating a spark discharge in the argon gas when the argon plasma is generated may be any method and is not limited in any way. For example, the discharge may be performed by temporarily applying a high voltage to the electrode. (For example, “igniter” or the like) can be exemplified.

A spark discharge may be generated from the surface of the carbon-containing material in the nitrogen plasma.
Thus, by generating spark discharge from the surface of the carbon-containing material in nitrogen plasma, carbon nitride can be produced stably and smoothly.
The spark discharge from the surface of the carbon-containing material in the nitrogen plasma may be formed by any method, but is not limited in any way. For example, a predetermined discharge radiated to nitrogen gas to form the nitrogen plasma is possible. You may make by adjusting the output, frequency, etc. of a microwave (especially the predetermined microwave radiated | emitted near the surface of a carbon containing material).
The reason why the production of carbon nitride can be stabilized by generating a spark discharge from the surface of the carbon-containing material in the nitrogen plasma is not necessarily clear, but such a spark discharge is not a fine carbon nitride. It is presumed that the nucleation is promoted (that is, the spark discharge gives the energy required for nucleation) (the generated nuclei are then grown to become the final carbon nitride).

  The carbon-containing material is not particularly limited as long as it contains carbon, and any carbon-containing material may be used without limitation. In order to prevent or reduce and to produce carbon nitride stably and smoothly, a higher carbon content is preferable. In particular, if the carbon-containing material is formed of graphite, it is preferable because these impurities can be prevented or reduced, and stable production can be achieved.

The carbon-containing material may be formed of a rod-shaped member.
Here, the rod-shaped member refers to a member having a portion extending along a line segment, and carbon nitride can be stably and smoothly manufactured by using a carbon-containing material formed by the rod-shaped member.
The reason why carbon nitride can be produced stably and smoothly by using a carbon-containing material formed by a rod-shaped member is not necessarily clear, but is emitted to nitrogen gas to form nitrogen plasma. This is considered to be based on some interaction between the predetermined microwave and the carbon-containing material as the rod-shaped member.

The flowing nitrogen gas is converted into the nitrogen plasma, and the volume velocity of the nitrogen gas may be 0.1 to 3.0 liters / (min · mm ² ) (hereinafter referred to as “flowing nitrogen”). Law ").
By converting the flowing nitrogen gas into nitrogen plasma (that is, generating nitrogen plasma using the flowing nitrogen gas), sufficient nitrogen can be provided to generate carbon nitride. Can be manufactured stably and smoothly. And by setting the volume velocity of nitrogen gas to 0.1 to 3.0 liters / (min · mm ² ), it is possible to give nitrogen required to produce carbon nitride, and the volume velocity is within this range. Can change the x of the produced carbon nitride (CN _x ) within the range of about 0.1 to 2 (of course, increasing the volume velocity will increase x. X decreases if the volume velocity is decreased.) Here, x is theoretically 1.33 (C ₃ N ₄ ), but x is preferably larger than 0.8 in order to sufficiently increase the hardness of carbon nitride (x> 0.8). , More preferably larger than 0.9 (x> 0.9) (x is 1.33 or less). In order to make x larger than 0.8 (x> 0.8), the volume velocity may be usually 1.0 liter / (min · mm ² ) or more.
The volume velocity is a volume perpendicular to the direction in which the nitrogen gas flows, and the volume (0 ° C., 1 atm) of the nitrogen gas flowing per unit area (mm ² ) unit time (1 minute) of the surface. Volume flow liter in standard state).

In the case of the flowing nitrogen method, a collecting member for collecting the collected carbon nitride on the surface and collecting it may be disposed on the downstream side of the flowing nitrogen gas.
Since the carbon nitride produced by this method is usually a fine powder (usually having an average particle size of 1 nanometer to 1 micrometer), it can be transported by flowing nitrogen gas to generate a nitrogen plasma. For this reason, if the collecting member is disposed on the downstream side of the flowing nitrogen gas (downstream side of the carbon-containing material), the generated carbon nitride can be attached and collected on the surface of the collecting member.
Further, if the temperature of the surface of the collecting member is kept at a predetermined temperature (for example, 20 to 1000 ° C.), the carbon nitride attached to the surface can be annealed, and the crystallinity of the carbon nitride is improved. Can do.

A collecting member for collecting and collecting the generated carbon nitride on the surface may be arranged below the carbon-containing material.
By doing so, the carbon nitride produced by the present method is moved downward by gravity, so that the carbon nitride can be attached to the surface of the collecting member disposed below the carbon-containing material and collected.
Also in this case, if the temperature of the surface of the collecting member is kept at a predetermined temperature (for example, 20 to 1000 ° C.), the carbon nitride adhering to the surface can be annealed, and the crystallinity of the carbon nitride Can be improved.

The predetermined microwave radiated to the nitrogen gas in order to form the nitrogen plasma is not limited as long as the nitrogen plasma can be stably formed and the carbon nitride can be manufactured stably and smoothly (for example, frequency and output). Although not limited at all, for example, the following may be generally used.
If the predetermined microwave frequency is too low, nitrogen plasma can be stably formed and carbon nitride cannot be produced stably and smoothly. If it is too high, a large amount of energy and equipment are required to generate microwaves. Therefore, it is preferable that the both conditions are satisfied, so that the lower limit is preferably 0.8 GHz or more, more preferably 1.5 GHz or more, and most preferably 2.0 GHz or more, and the upper limit is preferable. Is 100 GHz or less, and most preferably 20 GHz or less.
If the predetermined microwave output is too small, nitrogen plasma can be stably formed and carbon nitride cannot be produced stably and smoothly. If it is too large, a large amount of energy and equipment are required to generate microwaves. Therefore, it is preferable that the both conditions be satisfied, and it is considered that the yield of carbon nitride (which increases substantially in proportion to the output) even within the range where both conditions are satisfied. The larger the output, the better.

The carbon nitride produced by this method (hereinafter referred to as “the present carbon nitride”) is a carbon nitride (that is, a powder) that is not supported in a matrix other than carbon nitride (that is, a powder). The whole powder of 1 is formed by carbon nitride and inevitable impurities), and like conventional carbon nitride, it is hard as an abrasive, and it is semiconducting so as to be an electronic device (eg, nanoelectronics). Field). The carbon nitride usually has an average particle size of 1 nanometer to 1 micrometer. The ratio of carbon nitride to the whole of the one powder (w1 is the mass of carbon nitride contained in the whole of the one powder, and w2 is the mass of unavoidable impurities contained in the whole of the one powder. / (W1 + w2)) is usually 0.5 or more, preferably 0.7 or more, more preferably 0.9 or more, and most preferably 0.95 or more. (Of course, it is 1 or less.) Needless to say, the entire powder constituting the powder may be formed of only carbon nitride.
In the present invention, “the whole of one powder constituting the powder is formed of carbon nitride and inevitable impurities” means that all of the powder constituting the powder is composed of carbon nitride and inevitable impurities. It is not required to be formed, and it is sufficient that at least one powder constituting the powder is formed by carbon nitride and unavoidable impurities (that is, the whole is formed by carbon nitride and unavoidable impurities). For example, the powder may include the powder or particles of the carbon-containing material used in the present method. The ratio of carbon nitride to the entire powder (calculated as m1 / m2 where m2 is the total mass of the powder and m1 is the mass of the carbon nitride contained in the entire powder) is usually. 0.5 or more, preferably 0.7 or more, more preferably 0.9 or more, and most preferably 0.95 or more (of course, 1 or less).
Further, as described above, _x of the produced carbon nitride (CN _x ) is preferably set to be larger than 0.8 in order to improve the use performance by sufficiently increasing the hardness of the carbon nitride (x > 0.8), more preferably greater than 0.9 (x> 0.9) (wherein x is 1.33 or less).

  Examples are given below in order to specifically describe the present invention. However, the present invention is not limited by these examples.

FIG. 1 is a schematic view showing a production apparatus (hereinafter referred to as “the present apparatus”) 11 for carrying out the carbon nitride production method (the present process) of the present invention. 2 is a cross-sectional view showing a state of a waveguide 59 and a reactor 21 which will be described later (showing a cross section by a plane including the axis of a right cylinder formed by the reactor 21. In FIG. 3 is a cross-sectional view taken along the line JJ of FIG. The apparatus 11 will be described with reference to FIGS. 1 to 3. 1 and 2, the vertical upward direction is indicated by an arrow A, and the vertical downward direction is indicated by an arrow B.
Roughly speaking, the present apparatus 11 includes a reactor 21 having a hollow cylindrical shape with a lid and a bottom, an electrode 23 (carbon-containing material according to the present invention) supported on the upper end of the reactor 21, and a reactor 21. Igniter 25 that causes spark discharge inside, argon gas introduction part 30 for introducing argon gas into reactor 21, and nitrogen gas introduction part 40 for introducing nitrogen gas into reactor 21 (note that argon gas Argon gas and nitrogen gas from the introduction part 30 and the nitrogen gas introduction part 40 are led to the internal space 21c of the reactor 21 through the conduit 22.) and microwave irradiation for irradiating the inside of the reactor 21 with microwaves And a substrate 61 (collecting member according to the present invention) disposed below the reactor 21.

The reactor 21 is formed by a hollow right cylindrical glass tube (in this case, the internal space 21c of the reactor 21 has a right cylindrical shape with a diameter of 8.03 mm and a height of 152.7 mm). The upper end 21a of the tube is closed, but the lower end 21b of the tube is open (the internal space 21c of the reactor 21 communicates with the outside 71 via the lower end 21b) (without lid). bottom). A rod-shaped electrode 23, which will be described in detail later, is supported by the upper end 21a of the reactor 21 so as to penetrate therethrough. The axis of the rod-shaped electrode 23 (the electrode 23 has a right cylinder shape, which is the axis of the right cylinder) is the axis of the right cylinder formed by the reactor 21 (hereinafter referred to as “reactor 21 axis”). The electrode 23 is supported by the upper end 21a of the reactor 21.
Here, the reactor 21 is supported by a support stand (not shown) so that the axis of the reactor 21 is substantially oriented in the vertical direction.
Moreover, the reactor 21 has the 1st nozzle 21n1 to which the conduit | pipe 22 is connected, and the 2nd nozzle 21n2 in which the discharge electrode 25a of the igniter 25 is inserted. The first nozzle 21n1 guides the argon gas and nitrogen gas from the conduit 22 to the internal space 21c of the reactor 21. The second nozzle 21n2 positions the tip of the discharge electrode 25a into the internal space 21c of the reactor 21, and both between the discharge electrode 25a and the electrode 23 and between the electrode 23 and the waveguide 59. The outer wall 59a of the waveguide 59 is grounded, and the igniter 25 can apply a high voltage between the discharge electrode 25a of the igniter 25 and the ground. Therefore, when the igniter 25 applies a high voltage between the discharge electrode 25a and the ground, the discharge electrode 25a discharges to the waveguide 59 via the electrode 23).

The electrode 23 which is a carbon-containing material is formed by cutting graphite into a shape of a right cylinder (diameter: 3.0 mm × height: 100 mm), and the upper end of the electrode 23 is positioned outside the reactor 21. In addition, the lower end of the electrode 23 is located in the internal space 21 c of the reactor 21. Here, the distance between the lower end of the electrode 23 and the lower end 21b of the reactor 21 (distance C in FIG. 1) is set to 36.6 mm. Here, the distance between the first nozzle 21n1 and the lower end of the electrode 23 (distance E in FIG. 1) is 58.4 mm, and the distance between the second nozzle 21n2 and the lower end of the electrode 23 ( In FIG. 1, the distance F) is 58.9 mm.
A DC voltage of 0 to ± 3 KV can be freely applied between the electrode 23 and the substrate 61 by a power supply device not shown here, but the voltage is applied here. (That is, the electrode 23 is not electrically connected to anything and is neutral).

  As described above, the igniter 25 can apply a regular pulse voltage between the discharge electrode 25a of the igniter 25 and the ground, and freely changes the pulse voltage cycle and the applied voltage. be able to.

  Here, the argon gas introduction unit 30 includes an argon gas cylinder 31 filled with high-pressure argon gas, an argon gas valve 33 that controls an argon gas flow rate from the argon gas cylinder 31, and an argon gas from the argon gas cylinder 31 to the reactor 21. An argon gas flow meter 35 for measuring the flow rate and a conduit 22 for introducing argon gas from the argon gas flow meter 35 to the reactor 21 are included. Therefore, by operating the argon gas valve 33, the argon gas flow rate introduced into the reactor 21 from the argon gas cylinder 31 can be freely changed while being measured by the argon gas flow meter 35 (the argon gas valve 33 allows the argon gas flow rate to be reduced). The introduction of argon gas from the gas cylinder 31 to the reactor 21 can be interrupted).

  Similarly, the nitrogen gas introduction unit 40 includes a nitrogen gas cylinder 41 filled with high-pressure nitrogen gas, a nitrogen gas valve 43 that controls the flow rate of nitrogen gas from the nitrogen gas cylinder 41, and the nitrogen gas cylinder 41 to the reactor 21. A nitrogen gas flow meter 45 for measuring the nitrogen gas flow rate, and a conduit 22 for introducing the nitrogen gas from the nitrogen gas flow meter 45 to the reactor 21. Therefore, by operating the nitrogen gas valve 43, the nitrogen gas flow rate introduced into the reactor 21 from the nitrogen gas cylinder 41 can be freely changed while being measured by the nitrogen gas flow meter 45 (the nitrogen gas valve 43 allows the nitrogen gas flow rate to be changed). It is also possible to intermittently introduce nitrogen gas from the gas cylinder 41 into the reactor 21).

The microwave irradiation unit 50 includes a microwave power source 51 that generates a microwave of 2.45 GHz, an isolator 53, a power monitor 55, a matching unit 57, and between these devices and from the matching unit 57 to the reactor 21. And a waveguide 59 for guiding the microwave between them.
The microwave power source 51 constantly generates a microwave having a frequency of 2.45 GHz, and the generated microwave is guided to the isolator 53 through the waveguide 59.
In the isolator 53, the first attenuation factor associated with the passage of the microwave from one of the two terminals of the isolator 53 to the other is accompanied by the passage of the microwave from the other of the two terminals to the one of the two terminals. It is designed to be extremely large compared to the second attenuation rate, thereby allowing the traveling wave to pass well while reducing the passage of the reflected wave. Here, the microwave (traveling wave) is successfully passed from the microwave power source 51 to the power monitor 55 (second attenuation factor), while the microwave (reflected wave) is passed from the power monitor 55 to the microwave power source 51. Decrease (the first attenuation factor).

The power monitor 55 measures the output of the microwave (traveling wave) from the isolator 53 to the matching unit 57 and the output of the microwave (reflected wave) from the matching unit 57 to the isolator 53.
The matching unit 57 matches the impedance between one end side of the matching unit 57 (side on which the power monitor 55 is attached) and the other end side (side on which the reactor 21 is attached) of the matching unit 57. The output of the microwave (traveling wave) from the microwave power source 51 to the reactor 21 and the microwave (reflection) from the reactor 21 toward the microwave power source 51 are determined by the impedance matching. The ratio of the output to the wave changes. That is, the output of the microwave irradiated to the reactor 21 can be changed by adjusting the impedance matching by the matching unit 57.

  As described above, between the microwave power source 51 and the isolator 53, between the isolator 53 and the power monitor 55, between the power monitor 55 and the matching device 57, and between the matching device 57 and the reactor 21 ( With respect to the outer surface), the microwave can move freely by the waveguide 59. Here, as shown in FIGS. 2 and 3, the waveguide 59 has a hollow inner space 59b (the microwave passes through the inner space. The direction in which the microwave travels (arrows in FIGS. 2 and 3). The section perpendicular to K.) is substantially rectangular (one side of the substantially rectangular shape is indicated by an arrow N in FIG. 2, and the other side is indicated by an arrow M in FIG. 3). The cross-sectional shape of the internal space 59b perpendicular to the direction in which the microwave travels (arrow K) has almost the same size and shape at all positions) and the outer wall provided so as to surround the internal space 59b 59a (made of aluminum and electrically grounded). The outer wall 59a is provided with a fitting hole 59c (in particular, see FIGS. 2 and 3) in which the reactor 21 is loosely fitted with a small gap, and the fitting hole 59c has a fitting hole 59c. The reactor 21 is loosely fitted and penetrated. The electrode 23 exists in the part of the reactor 21 that passes through the internal space 59b. Therefore, the microwave radiated from the matching device 57 passes through the internal space 59b of the waveguide 59 and the reaction in which the electrode 23 exists. Radiated to the portion of the vessel 21.

  Here, the substrate 61 is a plate-like member in which both main surfaces formed of silicon are planar, and here, the substrate 61 is supported below the reactor 21 so that the main surfaces are horizontal. Although not shown here, a heater for heating the substrate 61 from the lower surface of both main surfaces of the substrate 61 is provided. With this heater (not shown), the upper surface 61a of both main surfaces of the substrate 61 can be brought to an arbitrary temperature of 20 ° C. to 1000 ° C. Here, the upper surface 61 a of the substrate 61 is kept at about 800 ° C. by the heat generated by the nitrogen plasma 81. Here, the distance (the distance D in FIG. 1) between the upper surface 61a of both main surfaces of the substrate 61 and the lower end 21b of the reactor 21 is 10 mm here. Thus, there is a sufficient gap between the upper surface 61a of both main surfaces of the substrate 61 and the lower end 21b of the reactor 21, and the internal space 21c of the reactor 21 is at atmospheric pressure (normal pressure: 1 atm). ).

A method for producing carbon nitride using the apparatus 11 shown in FIG. 1 will be described (hereinafter, it will be described separately in the first to sixth steps. 1 procedure to 6 procedures).
First, the argon gas valve 33 is operated to continuously introduce argon gas from the argon gas cylinder 31 to the reactor 21 at a volume flow rate of 10 liters (standard state, ie, 0 ° C., converted to 1 atm) / min. (The flow rate is measured by an argon gas flow meter 35).
Secondly, after the microwave power source 51 is started, the matching unit 57 is adjusted so that the microwave output continuously irradiated to the reactor 21 is set to 300 W (the output is measured by the power monitor 55). .)

Third, the igniter 25 is activated and regularly between the discharge electrode 25a and the electrode 23 and between the electrode 23 and the waveguide 59 (in this case, 1 in about 1/120 second). The spark discharge is frequently generated. As a result, argon plasma is generated in the internal space 21 c of the reactor 21.
Fourth, by adjusting the matching unit 57 again, the output of the microwave continuously irradiated to the reactor 21 is set to 500 W (the output is measured by the power monitor 55).

Fifth, the nitrogen gas valve 43 is gradually opened while the argon gas valve 33 is closed. Eventually, the gas introduced into the reactor 21 is 0 liters of argon gas (standard condition, that is, converted to 0 ° C. and 1 atm) / minute (that is, the introduction of argon gas is stopped), and nitrogen gas. Is 10 liters (standard state, that is, converted to 0 ° C. and 1 atm) / minute (the flow rate is measured by the nitrogen gas flow meter 45). The flow rate of nitrogen gas is 2.4 liters (standard state, that is, 0 ° C.) per cross-sectional area of the internal space 21c of the reactor 21 (area of a cross section perpendicular to the direction in which nitrogen gas flows in the internal space 21c). 1 atm conversion) / (min · mm ² ).
The operation of gradually opening the nitrogen gas valve 43 while closing the argon gas valve 33 is performed over approximately 0.5 minutes. During this operation, the total amount of gas introduced into the reactor 21 (that is, argon gas and nitrogen) The total amount with gas) was kept at 10 liters (standard state) / min. As a result, nitrogen plasma is generated in the internal space 21 c of the reactor 21.
Sixth, the matching unit 57 is adjusted again so that the reflected wave is minimized so that a spark discharge is generated at the lower end of the electrode 23. The spark discharge occurs intermittently, but the state where the spark discharge is intermittently maintained is maintained for about 15 minutes. According to the power monitor 55, the output when the spark discharge is intermittently occurring is approximately 600W.

By continuing the nitrogen plasma formed in the internal space 21c of the reactor 21 by the fifth and the spark discharge generated by the sixth, carbon nitride powder is gradually deposited on the upper surface 61a of the substrate 61.
The carbon nitride powder obtained in this way does not appear to be carbon nitride in other parts (parts other than the part of the grains) of which part of the grains is carbon nitride like conventional carbon nitride. However, all the powder was carbon nitride (in this case, impurities other than carbon nitride were not substantially contained. The ratio of carbon nitride to the whole of one powder (nitriding contained in the whole of one powder) When the mass of carbon is w1 and the mass of inevitable impurities contained in the whole is w2, w1 / (w1 + w2)) is about 1. Carbon nitride is not supported in the matrix and is an independent carbon nitride powder.) In the powder thus obtained, the whole of one powder constituting the powder is formed of carbon nitride and unavoidable impurities (not substantially contained here). The carbon nitride portion was not present in the graphite as shown in Fig. 1, and it was obtained as an independent powder formed only by carbon nitride (including unavoidable impurities). Further, the ratio of carbon nitride to the whole obtained powder (calculated as m1 / m2 where m2 is the total mass of the powder and m1 is the mass of carbon nitride contained in the whole). Was about 1.

The obtained carbon nitride was observed with a scanning electron microscope (SEM).
As a scanning electron microscope (SEM), model number JSM-890 manufactured by JEOL Ltd. was used.
The upper surface 61a portion of the substrate 61 on which carbon nitride was deposited was cut into 3 × 5 mm, and the cut sample was held on a sample table with a conductive tape (carbon tape). Then, platinum vapor deposition was performed on the sample surface (vapor deposition apparatus: JEOL, model number JUC-5000), and the platinum vapor deposited sample (sample stage) was introduced into the analyzer.
The operation of the electron beam source was started (acceleration voltage 10 kV), axis alignment and astigmatism correction were performed, the focus was adjusted at a magnification of 250,000 times, and then the magnification was adjusted to 200000 times for observation and photographing.
A scanning electron microscope (SEM) photograph taken in this manner is shown in FIG. As shown in FIG. 4, it was revealed that the obtained carbon nitride powder had a particle size (average particle size) of about 80 nanometers.

The obtained carbon nitride was analyzed by X-ray photoelectron spectroscopy (XPS).
As X-ray photoelectron spectroscopy (XPS), model number AXIS-HS (excitation X-ray: MgKα ray (acceleration voltage 15 kV, current 10 mA)) manufactured by Shimadzu / KRATPS was used.
A portion of the upper surface 61a of the substrate 61 on which carbon nitride was deposited was cut into 5 × 5 mm, and the cut sample was held on a sample table with a conductive tape (carbon tape). A sample (sample stage) was introduced into the analyzer.
The operation of the X-ray source (MgKα) was started (acceleration voltage 15 kV, current 10 mA), and test analysis was performed to check whether the sample was charged. When the sample was charged, electrons were supplied to the sample with a neutralizing gun, and charge correction was performed under appropriate neutralization conditions (conditions that provide the best peak position, width, height, and contrast).
The conditions in the qualitative analysis are as follows. That is, the analysis energy range is 0 to 1154 eV, the pass energy is 80 eV (low resolution), the energy step is 1 eV, and the analysis area is about 0.7 × 0.3 mm. After analysis under such measurement conditions, element identification was performed from the obtained spectrum.
The conditions in the state analysis are as follows. That is, switching to a monochromatic X-ray source (acceleration voltage 15 kV, current 5 mA), analysis energy range C1s: 280-300 eV, N1s: 390-410 eV, O1s: 523-543 eV, pass energy: 40 eV (medium resolution), energy step : 0.05 eV, integration number: 50 times, analysis area: about 0.7 × 0.3 mm. After analysis under such measurement conditions, the binding state was identified from the obtained spectrum.
The results of X-ray photoelectron spectroscopy (XPS) obtained as described above are shown in FIG. It became clear that both N1s and C1s are mainly sp ³ type hybrid bonds. When the obtained carbon nitride was represented by the chemical formula CN _x , x was about 1 (x = about 1.0>0.9> 0.8, and x was 1.33 or less. ).

As described above, the method for producing carbon nitride CN _x shown in the present embodiment is introduced into nitrogen gas (introduced into the internal space 21c of the reactor 21 by the nitrogen gas introduction unit 40 in the fifth procedure). Nitrogen plasma (nitrogen plasma generated in the internal space 21c of the reactor 21) generated by radiating a predetermined microwave (radiated by the microwave irradiation unit 50 by the second procedure and the fourth procedure). The electrode 23 which is a carbon-containing material containing carbon is brought into contact.
Here, before the nitrogen plasma is generated, argon gas (introduced into the internal space 21c of the reactor 21 by the argon gas introduction unit 30 by the first procedure) is introduced into a predetermined microwave (by the second procedure). Are emitted by the microwave irradiation unit 50) to generate argon plasma (argon plasma generated in the internal space 21c of the reactor 21), and the argon gas is replaced with the nitrogen gas (first). The nitrogen plasma is generated in 5 steps).
Furthermore, a spark discharge that assists the generation of the argon plasma is generated in the argon gas when the argon plasma is generated by the third procedure.

In addition, in the sixth procedure, spark discharge is generated from the surface of the electrode 23 as the carbon-containing material in the nitrogen plasma.
The electrode 23 as the carbon-containing material is a graphite rod-shaped member (as described above, a member having a portion extending along a line segment that is an axis of the right circular cylinder formed by the electrode 23. Here, it is a member composed of only a portion extending along the line segment). Then, a nitrogen plasma is formed with the line segment (the axis of the right circular cylinder formed by the electrode 23) of the portion extending along the line segment of the rod-shaped member forming the electrode 23 which is the carbon-containing material. Therefore, an angle formed by a predetermined microwave radiation direction (indicated by an arrow K in FIGS. 2 and 3) radiated to the nitrogen gas (a straight line parallel to the radiation direction (a straight line parallel to the arrow K)). ) In parallel with the line segment (the axis of the right circular cylinder formed by the electrode 23), and the smaller one of the two angles formed by the parallel line and the line segment. The angle is about 90 degrees.
Here, the flowing nitrogen gas continuously introduced into the internal space 21c of the reactor 21 by the nitrogen gas introduction unit 40 is converted into the nitrogen plasma, and the volume velocity of the nitrogen gas is set to 0. 0. 1 to 3.0 liters / (min · mm ² ) (specifically, 2.4 liters (standard state, ie, 0 ° C., converted to 1 atm) / (min · mm ² )).

In addition, a substrate 61 as a collecting member is disposed on the downstream side of the flowing nitrogen gas with respect to the electrode 23 as a carbon-containing material in order to collect and collect the generated carbon nitride on the upper surface 61a. (Nitrogen gas circulates in the internal space 21c of the reactor 21 from the upper side to the lower side, and a substrate 61, which is a collecting member, is disposed below the electrode 23, which is a carbon-containing material. ).
A substrate 61 serving as a collecting member is disposed below the electrode 23 serving as a carbon-containing material in order to collect the generated carbon nitride by attaching it to the upper surface 61a.

The predetermined microwave radiated to nitrogen gas to form nitrogen plasma has a frequency of 0.8 to 100 GHz (specifically, 2.45 GHz).
In addition, the carbon nitride CN _x obtained by the manufacturing method of this example is formed of carbon nitride and unavoidable impurities as a whole of one powder constituting the powder, and has an average particle size of 1 nanometer to 1 Micrometer (specifically, approximately 80 nanometers).

It is the schematic which shows the manufacturing apparatus (this apparatus) for enforcing the manufacturing method (this method) of the carbon nitride of this invention. It is sectional drawing which shows the state of a waveguide and a reactor. It is JJ sectional drawing of FIG. It is a scanning electron microscope (SEM) photograph of the carbon nitride powder obtained by this method. It is a graph which shows the X-ray photoelectron spectroscopy (XPS) analysis result of the carbon nitride obtained by this method.

Explanation of symbols

11 Apparatus 21 Reactor 21a Upper end 21b Lower end 21c Internal space 21n1 First nozzle 21n2 Second nozzle 22 Conduit 23 Electrode 25 Igniter 25a Discharge electrode 30 Argon gas introduction part 31 Argon gas cylinder 33 Argon gas valve 35 Argon gas flow meter 40 Nitrogen gas Introduction part 41 Nitrogen gas cylinder 43 Nitrogen gas valve 45 Nitrogen gas flow meter 50 Microwave irradiation part 51 Microwave power supply 53 Isolator 55 Power monitor 57 Matching device 59 Waveguide 59a Outer wall 59b Internal space 59c Insertion hole 61 Substrate 61a Upper surface 61a
71 External 81 Nitrogen plasma

Claims (7)

    A method for producing powdery carbon nitride, comprising bringing a carbon-containing material containing carbon into contact with nitrogen plasma generated at atmospheric pressure by radiating a microwave to nitrogen gas.     The manufacturing method according to claim 1, wherein the microwave has a frequency of 0.8 to 100 GHz.     The manufacturing method of Claim 1 or 2 which produces a spark discharge from the surface of the said carbon containing material in the said nitrogen plasma. The flowing nitrogen gas is converted into the nitrogen plasma,
The manufacturing method of any one of Claims 1-3 whose volume velocity of nitrogen gas is 0.1-3.0 liter / (min * mm < ² >).     The manufacturing method according to claim 4, wherein a collecting member that collects the produced carbon nitride by adhering to the surface is disposed downstream of the flowing nitrogen gas.     The manufacturing method according to claim 1, wherein a collecting member that collects the produced carbon nitride by attaching to the surface is disposed below the carbon-containing material.     Powdered carbon nitride produced by the production method according to claim 1.