JPH06345569A - Pulse cvi device - Google Patents

Abstract

PURPOSE:To provide an industrial compact pulse CVI device capable of efficiently filling the same or different materials in various porous substrates or coating the substrate. CONSTITUTION:A reaction furnace consists of a reaction chamber 12 provided with a gas inlet part 11 at its end and having an internal storage space 16 for setting a substrate 17 to be treated and a means 13 for heating the periphery of the chamber 12, and the furnace is connected to a raw gas introducing line and an exhaust line to constitute a pulse CVI device. The chamber 12 is formed with a graphite material 19 coated with a gas-impermeable silicon carbide 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a carbonaceous or ceramics-based porous substrate filled with the same or different substances.
A pulsed CVI device for coating.

[0002]

2. Description of the Related Art Conventionally, as a chemical means for coating a substrate surface of a certain kind with the same or different substance, a CVD (Chemic) method utilizing a reduction reaction, a substitution reaction, a disproportionation reaction, etc.
al Vapor Deposition) method is used. However, the coating layer formed by applying the CVD method has a clear separation at the interface with the base material, and when used in a heated state, a delamination phenomenon easily occurs due to thermal shock or mutual thermal expansion difference. There is.

In order to eliminate such drawbacks, a low pressure CVD is used as an improved means for preventing the delamination phenomenon and densifying the material by filling the base material structure with a coating material.
Methods and pulsed CVI methods have been developed. Low pressure CVD
The method is a method in which the pressure in the reaction system is reduced to several tens to several Torr to eliminate the gas present in the tissue pores of the substrate, and then the CVD operation is performed. According to this low pressure CVD, the linear flow velocity of the raw material gas is increased and the partial gas concentration difference is eliminated, and the gas boundary layer on the substrate is thinned to form a uniform coating film. For the purpose of depositing and filling the coating substance to the inside of the structure of the material, no significant improvement effect is observed.

On the other hand, pulse CVI (Pulse Chemica)
The Vapor Infiltration) method is a process in which the raw material gas is brought into contact with the heated base material in a gas state in an intermittently repeated process under a short cycle of pressure reduction and pressure increase, so that the coating substance can be smoothly introduced into the tissue of the base material. It becomes possible to fill.
Therefore, various porous substrates are packed with solid phase deposits,
A method for producing a filled porous body that is filled and densified (Japanese Patent Laid-Open No. 62-
No. 205278) and a method for forming a strong oxidation resistant SiC coating layer on a carbon fiber reinforced carbon material (Japanese Patent Laid-Open No. 4-42878).

However, when the pulse CVI method is industrially applied, there remains a problem to be solved in the device structure. That is, the pulse CVI device basically has a structure in which a source gas introduction system including a source vaporizer and an exhaust gas system including a vacuum pump are combined in an airtight reaction furnace provided with a heating means, and a conventional reaction system is used. The furnace material is made of quartz or a heat resistant alloy such as Inconel. However, since a quartz reactor is easily damaged and it is difficult to manufacture and process a large-scale furnace, there are many problems in designing an industrial furnace. On the other hand, metal reactors have poor corrosion resistance,
There is a problem in terms of durability life because the material undergoes fatigue and deformation due to pulse operation under high temperature.

In general, when the pulse CVI method is applied, it is necessary to repeat the pulse of the raw material gas introduction-precipitation reaction-vacuum exhaustion 5000 to 10000 times.
As the reactor becomes larger and the internal volume of the reaction system increases, it is necessary to take measures such as increasing the amount of raw material gas, lengthening the exhaust time, increasing the capacity of the exhaust pump, increasing the amount of exhaust gas, and at the same time increasing the pulse interval. Control becomes difficult. For this reason, it is preferable to make the reactor type compact and design the reactor form so that the internal volume of the reaction system does not become much larger than the substrate size. However, the degree of freedom in the furnace design is severely restricted in the case of quartz and metal materials, which have poor workability.

In order to solve such problems, the inventors of the present invention have made a reaction made of dense graphite having a gas introducing portion at an end and a storage space for setting a substrate to be treated formed therein. A reaction furnace main body comprising a chamber and a heat generating means for heating the periphery of the reaction chamber is housed and installed in a metal closed system container to constitute a reaction furnace, and the reaction furnace is constituted by a source gas introduction series and exhaust gas. A pulse CVI device having a structure connected in series has already been proposed (Japanese Patent Application No. 4-238978).
issue).

[0008]

According to the above-mentioned prior art, since the reaction furnace is composed of a dense graphite material having excellent heat resistance, corrosion resistance, heat shock resistance, workability, etc., the storage space for the substrate to be treated can be made small. It is possible to secure a stable durable life over a long period of time. However, since the carbonaceous material is essentially porous, the resin component is carbonized after impregnating the inside of the tissue with the thermosetting resin, or the surface of the graphite material is coated with a carbon coating to modify the surface texture. However, there is a limit to the airtightness of the material. For this reason, the wall thickness of the graphite material that constitutes the reactor is 5
Unless it is designed to be 0 mm or more, there is a drawback that the efficient pulse CVI operation cannot be stably continued. Besides,
Due to the fact that the graphite material itself is easily oxidized, it is an essential requirement to house the reactor body in a metal closed system container, and there is a limit to the miniaturization of the device.

The present invention is a further improvement of the above-mentioned prior art, and its purpose is to provide an industrially-advanced compact structure capable of efficiently filling and coating various porous substrates with the same or different substances. It is to provide a pulse CVI device.

[0010]

A pulse CVI device according to the present invention for achieving the above object is provided with a gas introducing portion at an end thereof and has a storage space for setting a substrate to be treated therein. In a device configuration in which a reaction chamber and a reaction furnace serving as a heat generating means for heating the periphery of the reaction chamber are connected to a source gas introduction series and an exhaust gas series, the reaction chamber is coated with a gas-impermeable silicon carbide. The structural feature is that it is formed of a given graphite material.

FIG. 1 is an overall configuration diagram illustrating a pulse CVI device according to the present invention. A source gas introduction series and an exhaust gas series are connected to a reaction furnace 1. The raw material gas introduction line includes, for example, a reducing gas supply line 2 and a carrier gas supply line 3
Enters the raw material vaporizer 4 and is introduced as a raw material mixed gas from the reservoir tank 5 into the reaction furnace 1 via the supply valve 6. The exhaust gas series is, for example, an exhaust valve 7
From the vacuum tank 8 through the trap 9, exhaust pump 10
It consists of a route leading to. The pulse CVI operation is
This is performed by setting the substrate to be treated in the storage space of the reaction furnace 1 and controlling the opening and closing of the supply valve 6 and the exhaust valve 7 while operating the raw material gas introduction series and the exhaust gas series.

As shown in the enlarged sectional view of FIG. 2, the reaction furnace 1 of the present invention is provided with a gas introducing portion 11 for introducing a raw material mixed gas at an end portion thereof, for setting a substrate to be treated therein. The reaction chamber 12 has a storage space 16 formed therein, and a heating means 13 for heating the periphery of the reaction chamber 12. The gas introduction part 11 can be formed of graphite or a metal material. However, when it is formed of a metal material, a water cooling jacket 14 is interposed at a portion in contact with the reaction chamber 12 to prevent deterioration of the metal portion due to overheating. A rod-shaped or coil-shaped resistance heating element is used for the heating means 13, and the outer surface thereof is preferably the heat insulating material 1.
Encapsulate with 5. The reaction furnace 1 may be designed so as to be housed and installed in a metal closed container in order to uniformly heat the whole, but the outer surface is closed for the purpose of preventing the oxidation damage of the reaction chamber 12 as in the prior art. I don't need it,
It is not a mandatory structural requirement.

The storage space 16 formed in the reaction chamber 12 has a vertical gap of about 10 mm when the plate-shaped substrate 17 to be treated is set therein, and the internal volume thereof is equal to the volume of the substrate 17 to be treated. It is preferable to set it within 10 times. Therefore, when using the plate-shaped substrate to be treated 17, the reaction chamber 12 and the accommodation space 1
It is preferable to design 6 in the shape shown in FIG. 3 (perspective view).

The main structural feature of the present invention resides in that the reaction chamber 12 is formed of a graphite material 19 coated with a gas-impermeable silicon carbide coating 18 in the above apparatus structure. In order to form the silicon carbide coating 18 on the surface of the graphite material, the graphite material 19 is preliminarily processed into the shape of a reaction chamber and placed in a closed reaction container kept at atmospheric pressure, and the halogenated organic material is heated in the system while being heated. A CVD method is used in which a silicon compound is filled with hydrogen gas while being entrained and brought into gas phase contact.
Examples of the halogenated organosilicon compound include trichloromethylsilane (CH ₃ SiCl ₃ ), trichlorophenylsilane (C
₆ H ₅ SiCl ₃ ), dichloromethylsilane (CH ₃ SiHCl ₂ ), dichlorodimethylsilane [(CH ₃ ) ₂ SiCl ₂ ], chlorotrimethylsilane [(CH ₃ ) ₃ SiCl], etc. are used, and the heating temperature is 90
It is set to 0 to 1100 ° C. Under this condition, the graphite material 19
A dense silicon carbide coating 18 having an amorphous or fine polycrystalline structure is formed on the entire surface of the layer.

A particularly preferable material for the reaction chamber is a graphite material as a base material having a coefficient of thermal expansion of 3.5 to 4.5 × 10 ^−6.
/ ° C. isotropic graphite material is used, and a silicon carbide film having a thickness of 20 μm or more is formed on the surface thereof by a CVD method to have a gas permeability of 0.001 × 10 ⁻³ cm / s (N ₂ gas) or less. The material is converted into a material, and by forming this material, an efficient pulse CVI operation can be performed even if the thickness of the reaction chamber is about 20 mm.

[0016]

In the pulse CVI apparatus of the present invention, the reaction chamber is made of a silicon carbide coated graphite material having excellent heat resistance, corrosion resistance, oxidation resistance and thermal shock resistance, and having a high gas impermeability. Therefore, in addition to exhibiting a stable durable life for a long period of time, the degree of reduced pressure in the system can be kept extremely low even if the thickness of the reaction chamber is about 20 mm. Therefore, it is ensured that the severe pulse CVI operation that applies the cycle of rapid heating and lowering and depressurization in the temperature range exceeding 1000 ° C. smoothly proceeds.

Further, since the graphite material as the base material of the reaction chamber is extremely easy to process, the storage space of the base material to be treated is designed to have a desired shape and size by preprocessing it before coating with silicon carbide. The inside volume of the storage space is one of the substrates to be processed which is suitable for efficient pulse CVI operation.
It becomes easy to form within 0 times. Furthermore, since the reaction chamber itself has sufficient oxidation resistance, it is not always necessary to have a structure in which the entire reaction furnace is housed and installed in a metal closed system container, and it is possible to make the apparatus structure compact. it can.

[0018]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples.

EXAMPLE An isotropic graphite material having a coefficient of thermal expansion of 3.5 to 4.5 × 10 ⁻⁶ / ° C. has a wall thickness of 20 mm and a storage space has a width of 350 m.
It is processed to have a rectangular cross section with m, height 30 mm, and depth 350 mm, and this is set in a CVD reaction vessel to 1000
Trichloromethylsilane (CH ₃ Si
A mixed reaction gas of Cl ₃ ) and H ₂ (molar ratio 5: 100) was introduced to form a silicon carbide film having a film thickness of 20 μm on the entire surface.
The graphite material coated with silicon carbide has a gas permeability of 0.001 × 1.
It was 0 ⁻³ cm / s (N ₂ gas) and showed a high gas impermeability.

A reaction furnace having a structure shown in FIG. 2 was prepared using the reaction chamber made of the graphite material coated with silicon carbide in this manner. In the reaction furnace, a plurality of silicon carbide heating elements were arranged as heating means 13 on the upper and lower surfaces of the reaction chamber 12, and the surroundings were covered with a heat insulating material 15. A thermistor was used for the power supply. The gas introduction part 11 was made of stainless steel, and an annular water cooling jacket 14 was provided between the gas introduction part 11 and the reaction chamber 12. This reactor is connected to a source gas introduction series and an exhaust gas series as shown in FIG.
I device was configured.

A graphite plate substrate having a side of 300 mm and a thickness of 10 mm was set in the storage space 16 using the above-mentioned pulse CVI device, heated to 1000 ° C. and then held for 2 hours. Then, the graphite plate base material was coated with silicon carbide under the following pulse CVI conditions. First, vacuum tank 8
The reaction chamber was reduced to below 2Torr by immediately trichloromethyl silane (CH ₃ SiCl ₃₎ and a mixed gas of H ₂ (C
A H ₃ SiCl ₃ / H ₂ molar ratio of 0.05) was introduced and maintained at 720 Torr. The raw material gas flow rate was 10 l / min, the 1 pulse time was set to 20 seconds, and the CVI operation of 1000 pulses was continued.

As a result, a uniform silicon carbide coating film having a thickness of 5 μm and having good peel resistance was formed on the surface of the graphite plate. The above-mentioned pulse CVI operation was repeated 50 times, but no abnormal phenomena such as material oxidation, cracking, breakage, and deformation were observed in the reaction chamber.

Comparative Example Porosity of 15% or less obtained by impregnating a tissue with a phenol resin and carbonizing, gas permeability of 0.01 × 10 ⁻³ cm / s (N ₂ ga
The graphite material of s) was processed to prepare a reaction chamber having the same size as that of the example. A reaction furnace was formed in this reaction chamber in the same manner as in the example, and the entire reaction furnace was housed and installed in a closed stainless steel container equipped with an argon gas introduction mechanism. When a pulsed CVI device having such a structure was used and a pulsed CVI operation was performed under the same conditions as in the examples, no normal formation of a silicon carbide film was observed on the graphite plate surface. Next, when a pulse CVI operation was performed under the same conditions using a reactor having a reaction chamber with a wall thickness of 100 mm made of the same graphite material, a silicon carbide coating having the same structure as that of the example was formed.

[0024]

As described above, according to the present invention, by using a gas-impermeable silicon carbide-coated graphite material as the material of the reaction chamber, it is possible to perform the pulse CVI treatment extremely efficiently and for a long period of time. A compact structure pulse CVI device that exhibits stable durability is provided. Therefore, by using this apparatus, it becomes possible to industrially carry out the pulse CVI operation of filling and coating a porous substrate such as a carbonaceous type or a ceramic type with the same or different substances.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram illustrating a pulse CVI device according to the present invention.

FIG. 2 is an enlarged sectional view showing a reaction furnace according to the present invention.

3 is a perspective view showing a reaction chamber portion of FIG. 2. FIG.

[Explanation of symbols]

 1 Reactor 2 Reducing Gas Supply Line 3 Carrier Gas Supply Line 4 Raw Material Vaporizer 5 Reservoir Tank 6 Supply Valve 7 Exhaust Valve 8 Vacuum Tank 9 Trap 10 Exhaust Pump 11 Gas Inlet 12 Reaction Chamber 13 Exothermic Means 14 Water Cooling Jacket 15 Reaction Chamber 16 Storage space 17 Base material 18 Silicon carbide coating 19 Graphite material

Claims (2)

[Claims] 1. A reaction furnace comprising a reaction chamber having a gas introduction portion at an end thereof and having a storage space for setting a substrate to be treated therein, and a heat generating means for heating the periphery of the reaction chamber. In a device configuration for connecting a source gas introduction system and an exhaust gas system, wherein the reaction chamber is formed of a graphite material coated with a gas impermeable silicon carbide. 2. A graphite material coated with an impermeable silicon carbide is formed on the surface of an isotropic graphite material having a thermal expansion coefficient of 3.5 to 4.5 × 10 ⁻⁶ / ° C. by a CVD method. Gas permeability of 0.001 × 10 ^-3 cm / with a silicon carbide coating with a thickness of 20 μm or more
The pulse CV according to claim 1, comprising a material of s (N ₂ gas) or less.
I device.