JPH0718013B2 - Method for producing glassy carbon coating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] Glassy carbon has high strength and hardness, is excellent in gas and liquid impermeability, and is chemically and thermally stable.
Moreover, it has a considerable electric conductivity and thermal conductivity. The present invention relates to a method for producing a glassy carbon coating body coated with such glassy carbon. Such coatings are expected to be used in a wide range of industrial fields such as chemical plants, electronics, nuclear power, and aerospace.

[Prior art and its problems] Conventionally, as a glassy carbon material, a thermosetting resin such as a furfuryl alcohol resin or a phenol resin is molded into a desired final product shape, and is carbonized by firing in an inert atmosphere. The method was adopted (reference: Toshinori Ishikawa et al., "New Carbon Industry," published by Modern Editor, 1980). However, in this method, the shrinkage of the product is considerably large when firing and carbonized, so that the size and thickness of the intended product are limited, and it is difficult to produce a product having a complicated shape. Further, in order to prevent cracks from entering the product, it is necessary to slow down the rate of temperature rise during firing, which causes a problem of poor productivity. When the glassy carbon material is used, it is not always necessary that the entire product is that, and in many cases, only the surface having a certain thickness needs to be covered with the glassy carbon material.

From such a viewpoint, a slurry is prepared by mixing a pitch-like compound obtained by incompletely thermally decomposing an organic polymer with an aromatic solvent, and coating the slurry on a carbon or ceramics base material in an inert atmosphere. There is known a method for producing a glassy carbon coated body which comprises firing at a temperature (Japanese Patent Publication No. 52-3968).
No. 4).

With this method, the above-mentioned problems of the glassy carbon material-coated product production can be overcome to some extent, but it is difficult to thicken the glassy carbon coating layer, and the above-mentioned coating and firing operations are repeated to thicken it. If this is done, cracking will occur, so that a coating layer having a sufficient thickness cannot be obtained.

It is an object of the present invention to provide a method for producing a glassy carbon coated body that eliminates the above-mentioned drawbacks.

[Means for solving problems]

The present inventors are investigating the conditions for firing a molded product such as carbon or ceramics coated with the slurry in an inert atmosphere, and by heating in an oxidizing atmosphere before the firing, We have found that the drawbacks are resolved.
Further, it has been found that the firing in such an oxidizing atmosphere significantly reduces the loss of carbon during firing, that is, improves the carbon yield.

That is, the present invention is characterized in that a film of an incomplete thermal decomposition product of an organic polymer is formed on a molded body of carbon, metal or ceramics, heated in an oxidizing atmosphere, and then fired in an inert atmosphere. It is a method for producing a glassy carbon coated body. Hereinafter, the present invention will be described in detail.

In the present invention, the carbon, metal or ceramics material is not particularly limited, but it is preferable that the surface on which the glassy carbon film is to be formed is rough to some extent. That is, if the material has pores, the open porosity is 5 to 50%, preferably 8 to 20%, and if it is a smooth material, # 30 to
Surface-polish with # 2000, preferably # 300 to # 800 abrasives.

The organic polymer is not particularly limited, but the carbon content is 30% by weight.
The above are preferable, for example, polyvinyl chloride, polyvinyl alcohol, polyvinyl acetate, and alkylphenol.

Pitch-like substances (hereinafter abbreviated as PC) obtained by appropriately thermally decomposing these organic polymers have a carbon content of 80% by weight or more, and since they are soluble in organic solvents such as benzene and chloroform, they can be easily applied by a coating method. A film can be formed. Especially when the glassy carbon coating is used for semiconductor jigs, susceptors, etc., PC in which polyvinyl chloride is thermally decomposed from the viewpoint of impurities is particularly preferable. The thermal decomposition is performed by heating at 200 to 500 ° C for 30 minutes or more in an inert atmosphere such as argon.

The PC may be dissolved in a solvent at a concentration of 200 to 800 g / l and applied to a carbon, metal or ceramic compact. From the viewpoint of solubility and volatility, the solvent is preferably an aliphatic chlorine-based solvent such as trichlene. The method of application is ultrasonic impregnation, brush coating, spraying, dipping and the like. It is preferable to dry at a relatively low temperature (about 50 to 100 ° C.) after coating.

Then, the coated body is heated in an oxidizing atmosphere. The oxidizing atmosphere is a gas having an oxidizing action such as oxygen or ozone. Air oxidation at a temperature of 150 to 350 ° C is convenient. When heating in air, if the temperature is lower than 150 ° C., it takes a long time to oxidize, which is not practical, and if it exceeds 350 ° C., the decarboxylation reaction becomes remarkable and the carbon yield decreases, which is not preferable. When ozone is used, 1% of ozone is mixed with air and heated at 50 ° C. at which temperature. The heating time must be adjusted depending on the shape of the molded product and the thickness of the coating film, but usually 5 to 20 hours is appropriate.

The reason why the carbonization yield at the time of firing is improved by heating in an oxidizing atmosphere in this way is that intermolecular or intramolecular crosslinking is caused by the oxidation of the coating surface of PC. It is thought that this is because PC becomes difficult to melt during the firing process and is carbonized without going through the molten state.

In the present invention, calcination means 600 to 1300 ° C. at which temperature 3
It is to heat for 0 minutes or more, which causes PC to be carbonized. In addition, when the slurry is applied thickly or when the dissolved concentration of PC is increased, it is preferable to slightly slow the temperature rising rate during firing in order to prevent generation of bubbles.

〔Example〕

 Hereinafter, the present invention will be specifically described with reference to examples.

Example 1 A vinyl chloride resin (SS-110 type manufactured by Denki Kagaku Kogyo Co., Ltd.) was placed in a heating furnace and heated at 390 ° C. for 9 hours under an argon gas atmosphere.
Heated for 0 minutes. The obtained PC was dissolved in trichlene at a concentration of 800 g / l to prepare a coating mother liquor. Material to be applied is open porosity
A 15% graphite and alumina plate (100 mm x 100 mm x 10 mm) was used and applied by ultrasonic impregnation.

Put the coated body in a heating furnace, and let the atmosphere be air, and
The temperature was raised up to 0 ° C. at 5 ° C./min, between 150 and 270 ° C. at a rate of 0.08 ° C./min, and heated at 270 ° C. for 5 hours. Next, the atmosphere was replaced with argon, and 15 ℃ / min up to 350 ℃, 2 ℃ / min from 350 ℃ to 550 ℃, 15 ℃ / m from 550 ℃ to 1000 ℃.
Firing was performed by raising the temperature at an in-rate and maintaining it at 1000 ° C. for 30 minutes.

The coating amount T and the carbonization yield R were calculated by the following formulas.

Here, W ₀ is the weight of the molded body before coating, W ₁ is the weight of the molded body after applying and drying PC, W ₂ is the weight of the molded body after firing, A
Is the surface area of the molded body.

The baked product is an optical microscope (magnification 100x) and SEM (magnification max.
It was observed in detail at 5000 times) to check for cracks and peeling.

As a result, a good glassy carbon-coated surface was obtained as shown in the table, and the carbonization yield was high, which was satisfactory.

Example 2 The surface of a glassy carbon coating produced in the same manner and under the same conditions as in Example 1 was polished with a # 1000 silicon carbide abrasive, and then again applied in the PC coating, drying and oxidizing atmosphere of Example 1. Was heated and baked in an inert atmosphere. The coating amount and the carbonization yield were determined by the same method as in Example 1, and the observation under an optical microscope and SEM was performed. As a result, as shown in the table, a good coated surface was obtained and the carbonization yield was high, which was satisfactory.

Example 3 When the coated body was placed in a heating furnace and heated, the atmosphere was changed to air, and about 1% ozone was added to the atmosphere. The heating temperature and time were 50 ° C. and 10 hours, respectively. A glassy carbon coating was produced under the same method and conditions as in Example 1.

The coating amount and the carbonization yield were determined by the same method as in Example 1,
An optical microscope and SEM observation were performed. As a result, as shown in the table, a good coated surface was obtained and the carbon yield was high, which was satisfactory.

Comparative Example The coated body was baked in an inert atmosphere without heating in an oxidizing atmosphere. Other than that, it performed according to Example 1. As a result, as shown in the table, many cracks were observed on the coated surface, and the carbonization yield of the coated surface was poor.

[Effect] When the glassy carbon coating is produced by the method of the present invention, the coating has a good surface condition without cracks, and the carbonization yield is high, so that the coating amount can be increased. .

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinyo Sato 3-5-1, Asahimachi, Machida, Tokyo Denka Kagaku Kogyo Co., Ltd. Central Research Laboratory (72) Inventor Kazumi Nozawa 3 Asahimachi, Machida, Tokyo Susumu Ogawa, Examiner, Central Research Laboratory, Denka Kagaku Kogyo Co., Ltd. (56) References JP-A-58-69792 (JP, A) JP-B-52-39684 (JP, B2)

Claims (1)

[Claims] 1. A carbon, metal or ceramic molded body is formed with a film of an incomplete thermal decomposition product of an organic polymer, heated in an oxidizing atmosphere, and then fired in an inert atmosphere. A method for producing a glassy carbon coated body.