JPH11209875A - Carbon made reaction furnace and production of pyrolytic boron nitride formed body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a pyrolytic boron nitride formed body free from contamination and to prolong the service life of a reaction furnace by coating at least a part of the surface of a reaction vessel and a heating heater, which constitute a carbon made reaction furnace for carrying out CVD method with a pyrolytic boron nitride film. SOLUTION: The reaction furnace 10 arranged in a water cooling chamber 17 is constituted so that the carbon made heating heater 12 and a carbon made core bar 21 at the center are provided in a carbon made reactor 11 provided with a heat insulating material 16 and if necessary, a partition heat insulating material 13 for uniformly heating is arranged between the heater 12 and the core bar 21. Boron halide and ammonia are introduced into the reactor 11 through a gas introducing pipe 14 and allowed to react with each other under a condition of about 2000 deg.C and 0.1-10 Torr to CVD-form the pyrolytic baron nitride formed body 20. In such a case, the pyrolytic boron nitride film having 10 μm to 6 mm film thickness is formed on a part of or the whole surface of the reactor 11 and/or the heater 12 by CVD method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in a CVD reactor for producing a pyrolytic boron nitride (hereinafter sometimes abbreviated as PBN) molded body by a CVD method (chemical vapor deposition method). The present invention relates to a carbon reactor.

[0002]

2. Description of the Related Art Conventionally, a PBN compact has been produced in a carbon-made reaction furnace, for example, placed in a water-cooled chamber under high temperature and reduced pressure by boron halide (for example, boron trichloride, boron trifluoride) and ammonia. Is industrially manufactured by the CVD method.

[0003] This carbon reactor is made of graphite because the reaction conditions by the CVD method are about 2000 ° C, high temperature of 0.1 to 10 Torr and reduced pressure. Therefore, the corrosion of graphite proceeds due to the slight corrosion of oxygen or ammonia gas in the reaction atmosphere.
Then, the fine particles of CO gas and graphite generated by the corrosion are taken into the PBN molded product as a product, which has an adverse effect on the quality characteristics of the PBN molded product, and lowers the product yield. Furthermore, the life of the reactor is shortened due to wear and cracking of the carbon reactor,
This leads to lower productivity and higher costs.

[0004]

DISCLOSURE OF THE INVENTION The present invention has been made to solve such problems, and it is hard to be attacked by impurity oxygen or NH ₃ gas, and the product is produced by CO gas or graphite fine particles generated by corrosion. An object of the present invention is to provide a carbon reactor having a long life while preventing a PBN molded body from being contaminated.

[0005]

Means for Solving the Problems In order to solve the above-mentioned problems, the invention described in claim 1 of the present invention provides a carbon reactor for producing a pyrolytic boron nitride molded body by a CVD method. A carbon reactor characterized in that the entire surface of a reaction vessel and / or the entire surface of a heater for a carbon reactor or a part of these surfaces is coated with a pyrolytic boron nitride film. .

As described above, in a carbon reactor used to form a PBN molded body by the CVD method, at least the entire surface of a reaction vessel and / or the entire surface of a heater for constituting a carbon reactor. By coating a part of the surface of
During the VD reaction, the erosion caused by the reaction vessel and graphite, which is the material of the heater, reacting with the impurity oxygen gas or NH ₃ gas in the reaction gas is reduced, and the generation of CO gas and graphite fine particles due to the erosion is almost eliminated. The contamination of the PBN compact by these is also reduced,
The purity and yield of the N compact can be improved, and the durability of the carbon reactor at high temperatures can be improved.
The productivity and cost reduction of the BN compact can be improved.

In the second aspect, the pyrolytic boron nitride film is formed by a CVD method, and its thickness is set to 10 μm to 6 mm. Here, if the formation reaction of the PBN film covering the surface of at least the reaction vessel and / or the heater for constituting the carbon-made reaction furnace is carried out by the CVD method, the content of impurities is extremely small, the high-temperature corrosion resistance is excellent, and the heat resistance is high. There is almost no generation of stress, and a dense and uniform PBN coating film can be formed on the carbon regardless of the shape of the reaction vessel or the heater.
When the thickness of the PBN coating film is less than 10 μm, carbon, which is a material of the reactor, is partially exposed and the corrosion prevention effect may be reduced. On the other hand, when the thickness is 6 mm, it is sufficient. Since the PBN film and the PBN film are anisotropic, thermal stress is easily generated and cracks are easily generated. Therefore,
In order to avoid such disadvantages, the thickness is preferably 10 μm to 6 mm, and more preferably 200 μm to 2 mm.

Next, in the invention described in claim 3 of the present invention, the material of the carbon reactor is made of isotropic graphite, anisotropic graphite or carbon fiber. As described above, if graphite is selected as the material for the carbon reactor, it may be either isotropic or anisotropic. By coating it with PBN, it can be used as a carbon reactor material having excellent corrosion resistance and heat resistance. Can be used. In addition, carbon fiber has an advantage in that there is a degree of freedom in molding, and a reactor shape suitable for the shape of the PBN molded body can be designed. Further, the carbon fiber may form a carbon reactor as a composite matrix such as carbon fiber reinforced graphite, or may be used as a heat insulating material for holding a water cooling chamber.

In the invention according to claim 4 of the present invention, the carbon reactor is used for a CVD reactor for producing a pyrolytic boron nitride molded body by a reaction between boron halide and ammonia. . As described above, the carbon reactor of the present invention is installed in a CVD reactor for manufacturing a PBN molded body, a mandrel is placed in a reaction vessel constituting the reactor, and PBN is placed on the mandrel by the CVD reaction. If deposited, since at least the reaction vessel and the heater are covered with PBN of the same material as the molded body, there is no erosion of carbon due to corrosion of slight oxygen or ammonia gas in the reaction atmosphere, and CO generated by this corrosion is eliminated. Fine particles of gas or carbon are hardly taken into the PBN molded article as a product, so that the quality of the PBN molded article can be remarkably improved, and productivity and yield can be improved.

Next, according to a fifth aspect of the present invention, there is provided a method for manufacturing a PBN molded body, comprising a core for producing the molded body in a carbon reactor installed in a CVD reactor. Before disposing the gold, at least the entire surface of the reaction vessel and / or the entire surface of the heating heater constituting the carbon reactor and / or a part of these surfaces are covered with PB.
N is coated by a CVD reaction, and thereafter, a mandrel is arranged in the reaction vessel, and PBN is deposited on the mandrel by the CVD reaction to obtain a formed body, which is a method for manufacturing a PBN formed body. .

According to this method, PBN is coated on the entire surface of the reaction vessel and / or the entire surface of the heater or a part of these surfaces by the CVD reaction, and PBN is deposited on the mandrel by the CVD reaction. The method for manufacturing a PBN compact can be carried out in the same carbon reactor, which has a great effect on the effective use of a CVD reactor, reduction of molding cost, improvement of productivity, and the like. Especially,
According to this method, not only the reaction vessel and the heater but also the PBN
The PBN film can be coated on the entire area of the carbon reactor in which the corrosive gas comes into contact during the molding reaction, so that the quality and yield of the resulting PBN molded body can be remarkably improved.

Further, according to a sixth aspect of the present invention, there is provided a method for producing a pyrolytic boron nitride molded article, comprising:
A mandrel for manufacturing the molded body is arranged in a carbon reactor installed in a CVD reactor, and at least the entire surface of a reaction vessel and / or the entire surface of a heater for constituting the carbon reactor. Alternatively, pyrolytic boron nitride is coated on a part of these surfaces by a CVD reaction, or subsequently, pyrolytic boron nitride is deposited on a mandrel by a CVD reaction to obtain a molded body. This is a method for producing a boron molded body.

According to this method, PBN is coated on the entire surface of the reaction vessel and / or the entire surface of the heater or a part of these surfaces by the CVD reaction, and PBN is deposited on the mandrel by the CVD reaction. Since the method for producing a PBN compact can be carried out simultaneously or successively, the effective use of the CVD reactor, the reduction of the molding cost, and the improvement of the productivity accompanying the shortening of the production time can be achieved.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail, but the present invention is not limited to these embodiments. The present inventors have conducted various studies on the prevention of corrosion of a carbon reactor used particularly when manufacturing a PBN compact by the CVD method. The present invention has been completed by conceiving that it is only necessary to cover the portion with PBN of the same material as the molded body to be produced.

First, an example of a carbon reactor for a CVD reactor of the present invention is shown in FIG. 1 as a schematic longitudinal sectional view. In FIG. 1, a carbon reactor 10 is disposed in a vertical cylindrical water-cooling chamber 17 having a gas exhaust pipe 15 and a gas inlet pipe 14 at the top and bottom, and a carbon reactor having an inner surface coated with PBN. It is composed of 11, a heat insulating material 16 surrounding it, and a heater 12. Reaction vessel 11
Inside, a molding mandrel 21 made of carbon is placed substantially at the center, and this is surrounded by a heater 12 made of carbon so that heating can be performed.

The partition 13 is formed by covering the entire surface of the heater 12 with P
When coated with BN, it is not necessary to use it. However, when not coated, the core metal 21 and the heater 12 are used to prevent corrosion of the heater which becomes high in temperature, prevent diffusion of contaminants, and equalize the temperature.
It is desirable to provide between them. In this example, the gas introduction pipe 14 is of a double pipe type in which two kinds of raw material gases are separately introduced and mixed at the upper part of the gas introduction pipe. The shape, mounting position and the like of the gas introduction pipe are appropriately designed in consideration of the above.

The production of a PBN molded body by a CVD reaction is as follows.
C is placed on the surface of the mandrel 21 disposed at the center of the reaction vessel 11.
The PBN thin film generated by the VD reaction is deposited and deposited to a predetermined thickness to produce a PBN molded body 20. on the other hand,
The raw material gas for the CVD reaction enters the reaction vessel 11 through the gas introduction pipe 14, undergoes a thermal decomposition reaction by the heater 12 to deposit PBN, and is then discharged out of the system through the discharge pipe 15.

The most important feature of the present invention is that the CV
In a carbon reactor for producing a PBN compact by the method D, at least the entire surface of the reaction vessel and / or the entire heater surface or a part of the surface constituting the carbon reactor is formed by a PBN thin film. It is covered.

When the entire surface of the reaction vessel is coated with PBN, the inside structure of the carbon reaction furnace is different from that of FIG. 1 described above, and a space through which a CVD reaction gas flows is provided outside the reaction vessel. The outer surface of the reaction vessel can also be coated with PBN.

The material of the carbon reactor 10 is such that the reaction conditions for PBN generation by the CVD method are about 2000.degree.
Because of the high temperature of 10T0rr and the reduced pressure, graphite is preferable among carbonaceous materials, and examples thereof include isotropic graphite, anisotropic graphite, carbon fiber, and carbon fiber reinforced graphite.

As described above, if graphite is selected as the material of the carbon reactor, it may be either isotropic or anisotropic, has excellent heat resistance, has strength and workability, and has PBN.
It is suitable for both a reaction vessel and a heater as a molding reactor material. Carbon fibers have the advantage that they have a high degree of freedom in molding and can be designed in a reactor shape suitable for the shape of the PBN compact. Further, the carbon fibers may form the reactor as a composite matrix such as carbon fiber reinforced graphite. Also,
A molded body of carbon fiber is preferably used as the heat insulating material 16.

The material of the mandrel 21 is also graphite from the viewpoints of heat resistance, workability, mold release and the like. Mandrel 2
The heater 12 for heating the reaction region 1 and its surroundings is, for example, a heater surrounding a mandrel and processed into a cylindrical shape located inside the reaction vessel, for example, having a heater pattern in a zigzag shape. Pyrolytic graphite, silicon carbide, etc., by high temperature method.
Pyrolytic graphite is preferred from the viewpoint of adhesion to the BN coating material and little impurities.

Next, pyrolytic boron nitride (PBN) was selected as the material of the coating layer covering the entire surface or a part of the reaction vessel and the heater for heating. As described above, by contaminating carbon, which is a contaminant for a PBN product, with PBN of the same material as the product, oxygen present in trace amounts of boron halide and NH ₃ , which are raw material gases for producing a PBN molded product, is reduced. Corrosion of carbon progresses due to the reaction with NH _3, and CO gas and carbon fine particles generated by this corrosion are taken into the PBN molded product, causing a decrease in the yield and quality deterioration of the PBN molded product. It is possible to effectively prevent a reduction in the life of the reaction vessel and the heater for heating, which are caused by exhaustion of the gas and generation of cracks.
Also, since there is almost no difference in the linear thermal expansion coefficient between carbon and PBN, it is extremely rare that defects such as peeling, cracking, and chipping occur at the joint surface, and this is an important option in combination with the corrosion resistance of PBN at high temperatures. is there.

The thickness of the PBN coating layer is set to 10
μm to 6 mm. The thickness of the PBN coating film is 10 μm
If it is less than 6 mm, carbon may be partially exposed and the corrosion prevention effect may be reduced. On the other hand, if it exceeds 6 mm, cracks easily occur in the PBN film due to thermal stress due to anisotropy of the PBN film. The range is good, and preferably 200 μm to 2 mm.

Next, a method for manufacturing a carbon reactor and a method for manufacturing a PBN compact according to the present invention will be described.
Both the PBN coating method of the reaction vessel and the heater of the present invention and the method of manufacturing a PBN molded body are well known in the art.
The law was adopted. First, for example, for the inner surface of the reaction vessel illustrated in FIG. 1, a graphite heater having a heater pattern is energized and heated to 1950 ° C.
Heating and reducing the pressure to 0.1 Torr, a predetermined amount of a boron trichloride gas and an ammonia gas are flowed, and a CVD reaction is performed for several hours. The PBN coating of 200 μm to 2 mm is applied to the inner surface of the graphite reaction vessel and the entire surface of the graphite heater. A PBN coating reaction vessel and a PBN coating heater are manufactured by forming a coating film. In this case, the PBN is coated not only on the reaction vessel and the heater, but also on the entire area where the gas comes into contact and the temperature rises, thereby further preventing corrosion.

Next, a graphite mandrel was placed in the PBN-coated carbon reactor, and the inside of the reactor was heated to 1950 ° C. and 0.1 Torr, and the pressure was reduced.
A predetermined amount of a boron trichloride gas and an ammonia gas are flowed, a CVD reaction is performed for several hours, and a PBN film is deposited and deposited on the surface of the mandrel to a predetermined thickness to produce a PBN molded body.

As described above, before the mandrel for manufacturing the molded body is placed in the carbon reaction furnace installed in the CVD reactor, at least the carbon reaction vessel constituting the carbon reaction furnace is placed. PBN is applied to the entire surface and / or the entire surface of the heater for heating or a part of these surfaces.
Another feature of the present invention is a method for producing a PBN molded body, which comprises coating by a VD reaction, thereafter placing a mandrel in the reaction vessel, and depositing and depositing PBN on the mandrel by a CVD reaction to obtain a molded body. One.

According to this method, the whole surface of the carbon reaction vessel and / or the whole surface of the heating heater or a part of these surfaces is coated with PBN by the CVD reaction, and the PBN is coated on the mandrel by the CVD reaction. Can be carried out using the same carbon reactor as in the method of manufacturing a compact by depositing the same, which has a great effect on the effective use of the CVD reactor, reduction of the molding cost, improvement of productivity, etc. .

[0029]

EXAMPLES The present invention will now be described specifically with reference to examples of the present invention, but the present invention is not limited to these examples. (Example) Outer diameter 200 mm, thickness 5 mm, height 300 m
m is heated to 1950 ° C. and 0.1 Torr by applying a current to the graphite heater having a cylindrical graphite reaction vessel and a heater pattern provided inside thereof.
Boron trichloride gas 1SLM, ammonia gas 2SL
A CVD reaction was performed at a flow rate of M for 2 hours to form a PBN coating film of about 200 μm (0.2 mm) on the inner surface of the graphite reaction vessel and the entire surface of the graphite heater.

Next, a graphite mandrel was installed at approximately the center of the PBN-coated graphite reaction vessel and the heater, heated to 1950 ° C. and 0.1 Torr, and decompressed to remove boron trichloride gas at 1 SLM. Then, a CVD reaction was performed with ammonia gas at a flow rate of 2 SLM for 6 hours, and a PBN film was deposited and deposited on the surface of the mandrel to produce a PBN molded body. Although the molding reaction of this PBN molded body was repeated for 50 batches or more, no wear or cracks were observed on the surfaces of the PBN-coated graphite reactor and the heater due to corrosion, and carbon contamination by CO gas, graphite Almost no contamination by fine particles was observed.

(Comparative Example) A carbon reactor without PBN coating was used, and a graphite mandrel was installed almost at the center of a graphite reactor and heater.
When a PBN film was deposited by the method D and a PBN molded body was repeatedly produced, at the time when 10 batch reactions were performed, the graphite surface of the reaction vessel and the heater was consumed, making it impossible to continue using the same. Was.

The present invention is not limited to the above embodiment. The above embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and has the same effect. Within the technical scope of

For example, in the above description, the case where the reaction vessel and the heater are covered with PBN by the CVD method has been mainly shown, but the present invention is not limited to this, and other members constituting the carbon reactor may be used. Any material that comes into contact with the reaction gas may be coated with PBN.

In the above embodiments and examples, after covering the reaction vessel and the heater with PBN by the CVD method, the reaction is stopped once and a mandrel is disposed.
Although the reaction is restarted to form a molded body, the present invention is not limited to this. At the same time, a mandrel is arranged and the reaction vessel and heater are coated with PBN by the CVD method, or the reaction is stopped. PBN on the mandrel without doing
May be precipitated to produce a molded article.

[0035]

According to the present invention, in a carbon reactor, at least the whole surface or a part of the reaction vessel and / or the heater constituting the carbon reactor is made of PBN which is made of the same material as the molded body to be manufactured. The corrosion resistance at high temperature of the carbon reactor is significantly improved,
Corrosion due to impure oxygen or NH ₃ gas in the reaction gas is almost eliminated, and foreign substances can be prevented from being mixed into the PBN compact. Therefore, the carbon reactor is
Can be used stably for a long time in the production of N molded bodies,
The process can be operated stably, and the purity of the PBN compact can be improved, the productivity can be increased, and the product yield can be improved. In addition, since the coating reaction of the reaction vessel and the heater with the PBN and the molding reaction of the PBN molded body can be performed using the same carbon reactor, the production cost of the PBN molded body can be reduced, the energy cost can be reduced, and the productivity can be reduced. Can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view showing an example of a carbon reactor of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Carbon reactor, 11 ... Reaction vessel, 12 ... Heater, 13 ... Heat insulation material of partition walls, 14 ... Gas introduction pipe, 15 ... Gas discharge pipe, 16 ... Heat insulation material, 17 ... Water cooling chamber, 20 ... PBN molding Body, 21 ... down payment.

Claims (6)

[Claims] 1. A carbon reactor for producing a pyrolytic boron nitride molded body by a CVD method, wherein at least the entire surface of a reaction vessel and / or the entire heater surface or a surface thereof constituting the carbon reactor. Characterized in that a part of the carbon reactor is coated with a pyrolytic boron nitride film. 2. The carbon reactor according to claim 1, wherein the pyrolytic boron nitride film is formed by a CVD method, and has a thickness of 10 μm to 6 mm. 3. The carbon reactor according to claim 1, wherein the material of the carbon reactor is isotropic graphite, anisotropic graphite or carbon fiber. 4. The carbon reactor according to claim 1, wherein the carbon reactor is used for a CVD reactor for producing a pyrolytic boron nitride molded body by a reaction between boron halide and ammonia. A carbon reactor according to any one of the preceding claims. 5. A method for producing a pyrolytic boron nitride molded body, wherein at least a carbon-made mandrel for producing the molded body is placed in a carbon-made reactor installed in a CVD reactor. Pyrolytic boron nitride is coated on the entire surface of the reaction vessel constituting the reaction furnace and / or the entire surface of the heater or a part of these surfaces by a CVD reaction, and then a mandrel is placed in the reaction vessel. A method for producing a pyrolytic boron nitride molded body, comprising depositing pyrolytic boron nitride on a mandrel by a CVD reaction to obtain a molded body. 6. A method for producing a pyrolytic boron nitride molded body, wherein a mandrel for producing the molded body is arranged in a carbon reactor installed in a CVD reactor, and at least a carbon reactor is provided. The whole surface of the reaction vessel and / or the whole surface of the heater for heating or a part of these surfaces is coated with pyrolytic boron nitride by a CVD reaction, or at the same time, thereafter, the pyrolytic boron nitride is coated on the mandrel by CVD. A method for producing a pyrolytic boron nitride molded body, wherein the molded body is obtained by depositing by reaction.