JPS61247611A - Manufacture of carbon material coated with thermal cracking carbon - Google Patents

Abstract

PURPOSE:To prepare the titled carbon material having coated film of high density thermal cracking carbon formed on the surface of a base material with high adhesion by feeding gas contg. raw material to form turbulent flow on a carbon base material heated at a specified temp. CONSTITUTION:A reaction chamber 10 is evacuated by opening a valve 8 by driving an exhaust pump 9. A carbon base material 5 (e.g. pitch coke base artificial graphite) is heated by a heater 6 at 1000-1200 deg.C, and the gas 11 contg. the raw materials [e.g. gaseous mixture of propane with N2 (carrier gas)] is ejected by opening a valve 1 and a three way cock 2 toward a tubulent flow-generating nozzle 3 side to the surface of the carbon base material 5 so as to generate turbulent flow. Thus, film of thermal cracking carbon having high density and high adhesion to the base material 5 is formed on the surface of the carbon base material 5. Obtd. carbon material coated with thermal cracking carbon is useful in the field of application where resistance to frequent repetition of cold/heat is required.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for producing a pyrolytic carbon-coated carbon material.

(Conventional technology) Methane, ethane, propane on heated substrate.

The technology to precipitate pyrolytic carbon by contacting gases containing hydrocarbons such as acetylene and benzene was developed in Japanese Patent Publication No. 38-195.
As is widely known from publications such as Publication No. 97, a wide range of applications have been researched or put into practical use, including space industry materials such as rocket nozzles, throats, and cones, mechanical materials such as gaskets, and various jig materials such as crucibles. ing.

The thermal expansion coefficient of a carbon base material such as artificial graphite is 4 to 5x r
o-'/℃o The thermal expansion coefficient of the coating plane of pyrolytic carbon deposited on this carbon substrate is 1.5 x 10-'/'
Due to the difference in thermal expansion coefficient between the two, the pyrolytic carbon was peeled off from the carbon base material and used for the various uses mentioned above.

(Problem to be solved by the invention) On the other hand, when pyrolytic carbon is used as a coating on a carbon material, it is essential to improve the adhesion to the carbon base material. Conventional pyrolytic carbon obtained by flowing a hydrocarbon-containing gas over a material has anisotropy and is oriented such that the C axis is perpendicular to the surface of the carbon substrate.

Adhesion is not good due to the difference in thermal expansion coefficient between the carbon base material and pyrolytic carbon. In particular, when the pyrolytic carbon film has a thickness of 100 μm or more, most of the film peels off from the carbon base material. Even if the thickness of the coating is kept to 20 to 30 μm, there is a problem that, for example, when a crucible having a curved surface is coated, the coating peels off from the curved surface after heating and cooling several times.

An object of the present invention is to provide a method for producing a pyrolytic carbon-coated carbon material that solves the above-mentioned problems and forms a high-density pyrolytic carbon film with good adhesion to a carbon substrate.

(Means for Solving the Problems) The inventors have developed a system in which hydrocarbon gas as a raw material is heated in a laminar flow state at
Although a pyrolytic carbon film with anisotropy is produced by pouring it onto a carbon substrate heated to ~1200°C, the hydrocarbon grows into a flat polymer with hexagonal network surfaces in the gas phase. Therefore, if the boundary layer where the flat polymer diffuses toward the surface of the carbon substrate is disturbed, the orientation will disappear and the pyrolytic carbon will have low anisotropy and good adhesion to the carbon substrate. The present invention was completed by discovering that a film could be obtained.

The present invention involves the production of a pyrolytic carbon-coated carbon material by supplying a raw material-containing gas to a carbon base material heated to 1000 to 1200°C in a turbulent flow to form a pyrolytic carbon film on the surface of the carbon base material. A first coating of pyrolytic carbon is formed on the surface of the carbon substrate by supplying a raw material-containing gas in a turbulent flow to a carbon substrate heated to 1000 to 1200°C. A method for producing a pyrolytic carbon-coated carbon material, comprising supplying the thick phase-containing gas in a laminar flow state while heating the pyrolytic carbon, and forming a second pyrolytic carbon film on the pyrolytic carbon first film. .

The carbon base material used in the present invention is not particularly limited, but artificial graphite is preferred. The raw material-containing gas is a gas containing raw materials that form pyrolytic carbon, and the raw materials are preferably hydrocarbons such as methane, ethane, propane, and benzene, and nitrogen, hydrogen,
It is preferable to supply the reaction system with a carrier gas such as argon.

As shown in FIG. 1, when a raw material-containing gas is caused to flow in a straight line as indicated by arrow A over a stationary carbon base material 5.

The gas velocity on the surface of the carbon base material 5 becomes zero, and the carbon base material 5
A boundary layer B is formed near the surface where the gas velocity is slow and stagnant. This is the 6 laminar flow state of the present invention.On the other hand, the 5 turbulent flow state means that the raw material supply gas is flown into the carbon substrate 5 as shown by arrow C in FIG.
1 to prevent the formation of the boundary layer C in FIG. As a method for creating a turbulent flow state, a gas introduction nozzle is provided near the carbon base material and gas is blown onto the carbon base material. Methods include installing a jig near the carbon base material to block laminar flow and making it turbulent (for example, packing granular graphite around the carbon base material), or vibrating the carbon base material itself twice, but there are no particular restrictions. do not have.

When coating the carbon substrate with pyrolytic carbon by supplying the raw material-containing gas in a turbulent flow on the surface of the carbon substrate, the temperature of the carbon substrate is limited to 1000 to 1200°C.
The rate at which a pyrolytic carbon film is formed is several microns per hour.
This is because if the temperature exceeds 1200° C., the effect of creating a turbulent flow state becomes ineffective, that is, the anisotropy of the generated pyrolytic carbon begins to increase.

The conventional technique is to simply supply the raw material-containing gas in a laminar flow state, and the precipitated pyrolytic carbon is easily peeled off from the carbon base material. According to the first invention of the present application, the raw material-containing gas is supplied to the carbon substrate at 1000 to 1200°C in a turbulent state.

As described above, the orientation of the generated pyrolytic carbon is inhibited, and an isotropic, high-density pyrolytic carbon film is formed on the carbon substrate with good adhesion.

The second invention of the present application is the pyrolytic carbon coating (
A raw material-containing gas is supplied in a laminar flow state onto the carbon base material on which a first film) is formed, and a conventional pyrolysis film having anisotropy is applied onto the first film of pyrolytic carbon. This method uses carbon as the second coating. In this case, the temperature of the carbon base material is 1000 to 1200°C or 2000 to 220°C.
It is preferable to use ot because high-density pyrolytic carbon can be obtained.

In the present invention, pyrolytic carbon is deposited using a known CVD apparatus. There are many restrictions on the method of heating the carbon base material, the method of adjusting the pressure inside the device, etc.

(Example) Next, the present invention will be explained in detail.

Example 1 FIG. 3 shows the pyrolytic carbon coating apparatus used in this example.

The exhaust pump 9 is operated and the valve 8 is opened to drain the inside of the reaction chamber 10.
The pressure was reduced to 50 Torr, and the reaction chamber 5 was heated by the heater 6.
Carbon base material 5 of pitch coke-based artificial graphite in 1100
℃, and connect valve 1 and three-way cock 2 to turbulence generating nozzle 3.
A mixed gas 11 consisting of 20 volumes of propane and 80 volumes of nitrogen (carrier gas) is supplied at a rate of 800 per minute.
The mixed gas 11 was ejected from the plurality of holes 3' onto the surface of the carbon substrate 5 at a flow rate of 1.0 ml to create a turbulent flow, and was allowed to react for 1 hour. In the plan view, 7 is a chamber for removing by-products such as tar and soot, and 12 is an exhaust gas. The pyrolytic carbon coating coated on the carbon substrate has a density of 201 g/cm3. Crystallite size. is aoX, and when the cross section is observed with a polarizing microscope, it is C
No columnar structure oriented in the axial direction was observed, showing isotropy, and the thickness of the film was 150 μm.

Comparative Example 1 Pyrolytic carbon was coated under the same conditions as in Example 1, except that the three-way cock 2 was opened to the nozzle 4 on the laminar flow generation side to cause the mixed gas to flow in a laminar flow state. The density of the pyrolytic carbon coating is 2.13 g/cm".

Although the Lc was 30X, a columnar structure was observed under a polarizing microscope, the thickness of the film was 100 μm, and many arcuate peeled portions with a diameter of about 5 nm were observed.

Comparative Example 2 The reaction was carried out under the same conditions as in Comparative Example 1 except that the temperature of the carbon substrate was 2000°C in Comparative Example 1, and the density was 2.20 g.
/cm'', Lc 300

Example 2 After forming a first film of pyrolytic carbon with a thickness of 150 μm by the method of Example 1, the same conditions as in Comparative Example 1 were carried out by immediately opening the three-way cock 2 toward the laminar flow generation nozzle at the same temperature. The same pyrolytic carbon with good orientation as in Comparative Example 1 with a film thickness of 100 μm was formed as a second film on the first film of pyrolytic carbon. No arc-shaped peeling portion was observed.

Example 3 After forming a first coating of pyrolytic carbon with a thickness of 150 μm by the method of Example 1, the temperature of the carbon substrate was raised to 2000°C, and at the same time, the three-way cock 2 was opened to the laminar flow generation nozzle side for comparison. The reaction was carried out under the same conditions as in Example 2, and pyrolytic carbon having the same density and Lc as Comparative Example 2 with a film thickness of 80 μm was formed as a second film on the first film of pyrolytic carbon. In cross-sectional observation, no arc-shaped peeling portion was observed.

The pyrolytic carbon-coated carbon materials obtained in the above Examples and Comparative Examples were placed in an electric furnace and heated at a rate of 500°C per hour to 150°C.
After being held at 0° C. for 1 hour, it was put into water at 15° C. and rapidly cooled. As a result, the pyrolytic carbon film of the comparative example was completely peeled off from the carbon substrate.

No peeling was observed in any of the samples of Example 91, indicating strong bonding between the carbon base material and the first coating of pyrolytic carbon, and between the first coating and the second coating of pyrolytic carbon.

(Effects of the Invention) According to the present invention, it is possible to coat a carbon base material with high-density pyrolytic carbon that has excellent adhesion to the carbon base material, and the resulting pyrolytic carbon-coated carbon material This makes it possible to apply the method to applications that require a lot of repetition.

[Brief explanation of drawings]

FIGS. 1 and 2 are schematic diagrams showing a state in which a raw material-containing gas is supplied to a carbon base material, and FIG. 3 is a block diagram schematically showing a pyrolytic carbon coating apparatus used in an example of the present invention. Explanation of symbols 1... Valve 2... Three-way cock 3
...Turbulent flow generation nozzle 4...Laminar flow generation nozzle 5
...Carbon base material 6...Heater 7...
・By-product removal chamber 8... Valve 9... Exhaust pump 10... Reaction chamber 11... Hydrocarbon-containing gas 12... Exhaust gas hand 1-' Amendment (voluntary) June 12, 1985 □

Claims (1)

[Claims] 1. A method characterized by supplying a raw material-containing gas to a carbon base material heated to 1000 to 1200°C in a turbulent state to form a pyrolytic carbon film on the surface of the carbon base material. Pyrolytic carbon coated carbon material. 2. A first coating of pyrolytic carbon is formed on the surface of the carbon substrate by supplying the raw material-containing gas in a turbulent flow to the carbon substrate heated to 1000 to 1200°C, and then the carbon substrate is A pyrolytic carbon-coated carbon material, characterized in that the raw material-containing gas is supplied in a laminar flow state while being heated, and a second pyrolytic carbon film is formed on the pyrolytic carbon first film. manufacturing method.