JPH07116606B2 - Diamond coated carbon material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a carbon member whose surface is coated with diamond. The diamond-coated carbon member is a speaker diaphragm, a fusion reactor wall material, and a friction resistant material. It can be used for high strength carbon fiber materials, integrated circuit boards, etc.

[Prior Art] Diamond has been conventionally synthesized in a thermodynamic equilibrium state under high temperature and high pressure, but recently, a synthetic method from a vapor phase (Chemical Vapor Deposit) which positively utilizes a non-equilibrium state.
It has been confirmed that diamond can be synthesized by the so-called CVD method.

By forming a diamond film on the surface of ceramics or a metal material by this method, it is possible to improve wear resistance, corrosion resistance and the like.

However, the synthesis temperature of the diamond film by the CVD method is usually 7
Since the temperature is 00 ° C or higher, there is a problem that the base material is limited.

Further, the condition for vapor-phase growth of a diamond film having good crystallinity is that it is well known that hydrocarbon diluted with 10 times or more of hydrogen is used and gas is excited by plasma or hot filament. JP-A-58-135117, JP-A-SHO
Details are shown in Japanese Patent Laid-Open No. 58-110494, Japanese Patent Laid-Open No. 59-3098, and the like.

Since the base material temperature is as high as 700 to 1200 ° C, although the base material such as refractory metal and ceramics is limited, by forming the diamond film on the base material using the above-mentioned CVD method, wear resistance, It is possible to improve corrosion resistance and high specific elasticity.

In addition, graphite, which is a carbon material, is widely used as a fusion reactor limiter material because it is a low-mass material and can withstand high heat flux, but graphite itself is a basic material because of its large chemical sputtering at high temperatures. As a material, it has been attempted to coat it with silicon carbide or titanium carbide. (Starfire-A Commercial Tokamakfusion P
owerplant Study, ANL-FPP-80-1) Therefore, it is possible to improve the characteristics by coating the graphite film with a diamond film having advantageous characteristics in terms of lower spattering property, lower mass property and the like.

[Problems to be Solved by the Invention] However, in the low-pressure vapor phase synthesis of diamond, carbon is essentially generated by thermal decomposition of hydrocarbons, and carbon substances other than diamond are re-gasified in the deposited substances. This is a method of growing only diamond by slowing the rate of conversion or precipitation to an extremely low level.

That is, it is considered that hydrocarbons are decomposed, precipitated, and etched on the surface of the base material.

In addition, since the diamond production atmosphere with good crystallinity is a strong hydrogen plasma and active hydrogen gas atmosphere, when a carbon material other than diamond is used as the base material, it is preferentially etched, and diamond nucleation is extremely difficult. Becomes unstable. Therefore, it has been impossible to stably form a diamond film having good crystallinity on a carbon substrate.

In view of the above circumstances, the present invention has good crystallinity in the carbon member,
Moreover, it is intended to provide a diamond-coated carbon member which does not peel off stably.

[Means for Solving the Problems] When an attempt is made to directly form a diamond film on a carbon member as described above, a strong reducing atmosphere usually contains hydrogen gas, so that the carbon member of the base material and the active member are activated. Hydrogen gas (for example, atomic hydrogen) reacts and becomes hydrocarbon. Therefore, the base material is apparently etched, and in a strong reducing atmosphere, the base material disappears within a few minutes. Moreover, the surface of the substrate is unstable even if it does not disappear.

Therefore, the inventors of the present invention have conducted extensive studies, and the carbon substrate surface is not impaired in a reducing atmosphere, or even if it is impaired, the effect is minor to the extent that it does not affect the formation of diamond nuclei, The present inventors were able to complete the present invention by finding that it should be formed via the intermediate layer.

That is, according to the present invention, in coating a diamond film on a carbon member, a diamond-coated carbon member has a silicon carbide film on a surface in contact with the carbon member, and the diamond film is formed thereon. It is about.

Further, it is preferable that at least the coating layer in contact with the diamond film is a silicon carbide film. This silicon carbide may be crystalline or amorphous.

Although it depends on the field of use of this diamond-coated carbon member, for example, when it is used as a diaphragm for a speaker, the Young's modulus is generally E and the specific gravity is And when Since the larger the material of, the better the conversion characteristics in the high frequency range, the thinner the intermediate layer of silicon carbide or the like having a higher density than that of diamond is better. Also, when used as a fusion reactor material, diamond, which is a low-mass material, is preferable to silicon carbide in terms of preventing a decrease in fusion reactor plasma temperature, and the silicon carbide film has a strong dispersion such as a diamond film. Considering the case of being sputtered by, it is preferable that the silicon carbide film having a mass higher than that of diamond is thin.

And, the range of 0.1 to 50 μm is preferable.

[Operation] As described above, the surface of the carbon member is once coated with the silicon carbide film or the like, and then the diamond film is synthesized on the upper surface of the coating film by the vapor phase growth method. Therefore, generally, the diamond film is formed without directly exposing the surface of the carbon member to the reducing atmosphere containing hydrogen gas and hydrogen gas produced by decomposition of raw material gas such as hydrocarbon and organic compound.

Further, since the vapor phase synthesis of diamond is generally carried out in a reducing atmosphere, the effect of the present invention can be obtained by using any vapor phase synthesis method of diamond.

[Examples] Examples of the diamond-coated carbon member according to the present invention will be specifically described with reference to comparative examples.

First, make a graphite material that is fired to have a purity of 99.9%, cut it into a size of 20 × 20 × 5 mm, and then
The graphite material obtained by final polishing with a No. 0 diamond powder was used as a substrate. Also, after polishing the base material surface after coating the intermediate layer with diamond powder No. 1000,
Diamond synthesis was performed.

As the diamond synthesizing method, microwave plasma CVD method and hot filament CVD method combined with DC plasma were used as chemical methods. In the latter case, Ta wire was used for the filament.

[Example 1] The above graphite base material was placed in a reaction vessel, and Si was placed in the reaction vessel.
When mixed gas plasma CVD of 10% by volume of Cl _4, 10% by volume of CH ₄ , and 80% by volume of H ₂ was performed, a 1 μm silicon carbide film was coated on the graphite substrate at a substrate temperature of 800 ° C. Then, the graphite substrate coated with the silicon carbide film was again subjected to H ₂ 99 vol%, CH _{2 by the} microwave plasma CVD apparatus shown in FIG.
_When plasma CVD was performed for 1 hour at a pressure of 50 Torr with a mixed gas of 41 vol%, a 2 μm diamond film was formed on the surface of the graphite substrate coated with the silicon carbide film.

This silicon carbide film did not show any peaks in X-ray diffraction, but ESCA (Electron Spectroscopy)
for Chemical Analysis) and Auger electron spectroscopy (Auger
Electron Spectroscopy) confirmed that it was an amorphous film composed of silicon and carbon, having a bond of silicon carbide.

Further, it was confirmed that the diamond film was a crystalline film whose peak was confirmed by X-ray diffraction.

Example 2 A silicon carbide film-covered graphite base material was prepared in the same manner as in Example 1, and this was used in combination with DC plasma CVD as shown in FIG.
In the equipment, pressure 50 Torr, filament temperature 2400 ° C, substrate surface temperature 8 by mixed gas consisting of 99% by volume of H _{2 and} 1% by volume of CH ₄
50 ℃, 8mm distance between filament and substrate, DC plasma 5A / c
Diamond coating is performed for 1 hour under the condition of cooling m ² substrate,
A μm diamond film was formed. As with Example 1, the silicon carbide film and the diamond film were found to be amorphous in the former and diamond in the latter for good crystallinity.

[Comparative Example 1] An experiment was conducted for 1 hour in the same manner as in Example 1 except that a diamond film was directly synthesized on the graphite base material without any coating layer such as a silicon carbide film.

Regarding diamond, no peak was observed by X-ray diffraction, and it was confirmed by electron beam diffraction that a diamond peak partially existed.

In addition, the weight of the graphite base material is 80% before and after the treatment.
It was also confirmed that the number was decreasing.

[Comparative Example 2] Under the same conditions as in Comparative Example 1, an experiment was conducted by increasing the time by 1 hour, and the graphite base material initially set disappeared.

[Effects of the Invention] As is clear from the above description, when a diamond film is coated on the surface of a carbon member, an intermediate layer such as a silicon carbide film is interposed so that a strong hydrogen plasma under diamond formation is obtained. As a result, the carbon member is not directly exposed to hydrogen or active hydrogen. As a result, the diamond-coated carbon member of the present invention (1) has a diamond film formed on a carbon member having a complicated shape depending on the purpose of use. You can

(2) Fields that require lubricity and wear resistance as a carbon member that combines the characteristics of diamond, fields that require a low dielectric constant as an integrated circuit board through which high frequencies flow, and high specific elastic modulus as a diaphragm for speakers and the like. Areas that require
Further, it can be used in fields requiring low mass and low chemical sputtering characteristics such as fusion reactor materials.

[Brief description of drawings]

The drawings are explanatory views of a diamond synthesizing apparatus used in Examples and Comparative Examples of the present invention. FIG. 1 is a microwave plasma.
CVD device, FIG. 2 is an explanatory view of a hot filament CVD device combined with DC plasma. 1 ... Substrate, 2 ... Quartz reaction tube, 3 ... Vacuum exhaust port, 4
...... Supply gas inlet, 5 …… Magnetron, 6 …… Waveguide, 7 …… Plunger, 8 …… Generated plasma, 9 ……
Filament, 10 ... Water-coolable support, 11 ... Cooling water, 12 ... AC power supply, 13 ... DC power supply, 14 ... Insulation seal.

Continuation of front page (56) Reference JP-A-63-153275 (JP, A) JP-A-62-196371 (JP, A) JP-B-62-10301 (JP, B2)

Claims (1)

[Claims] 1. A diamond-coated carbon member, which comprises coating a carbon member with diamond, having a silicon carbide film on a surface in contact with the carbon member, and forming a diamond film on the silicon carbide film.