JP3156981B2 - Method of forming carbonaceous coating by electrolytic method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a carbonaceous coating by a novel electrolytic method. More specifically, the present invention forms a diamond thin film, a diamond-like carbon thin film or an amorphous carbon or a graphite thin film on a conductive material surface by electrolyzing an organic compound, with good adhesion and extremely easily at low cost. It concerns an industrial process.

[0002]

2. Description of the Related Art Conventionally, diamond is extremely hard and has high wear resistance. For industrial use, cutting tools made of non-ferrous and non-metal materials, wear-resistant tools requiring high wear resistance, Used for wear-resistant members.
Examples of the diamond material used for these diamond tools and wear-resistant members include natural or synthetic single-crystal diamond and sintered polycrystalline diamond.

Further, in recent years, a technique for synthesizing a diamond thin film by a vapor phase synthesis method has remarkably developed, and a diamond thin film is formed on a base material surface by the vapor phase synthesis method, and is used for various diamond tools and wear-resistant members. Attempts have been made to use it.

[0004] As this gas phase synthesis method, for example, a chemical vapor deposition method is used in which a raw material gas containing a carbon source is plasma-decomposed, or a diamond thin film is deposited on the surface of a substrate by utilizing an uneven reaction. (CVD method), an ionization vapor deposition method of forming a film-like diamond on a substrate surface using a hot cathode PIG gun, a cold cathode PIG gun, a sputter gun, or the like is known. In particular, the method of depositing a diamond thin film on a substrate surface by the CVD method has attracted recent attention because it does not require much high temperature, is easy to continuously operate, and is industrially advantageous as compared with other methods. Is taking a bath.

Various methods have been proposed for forming a diamond thin film by the CVD method. For example, a method of activating a raw material gas containing 2 to 30 mol% of carbon monoxide and hydrogen gas to obtain a super thin film is proposed. A method of contacting with a hard alloy and the like are disclosed (JP-A-1-201476).
No.). However, in such a method of forming a diamond thin film by the CVD method, a relatively low temperature may be used as compared with other vapor phase synthesis methods, but it is still 800 to 800.
Since a base material temperature of 1000 ° C is required, base materials such as low-melting copper alloys, magnesium alloys, and aluminum cannot be used. It is unavoidable that the type of the base material is limited, for example, it is difficult to form a thin film and is unsuitable as a base material. Generally, non-iron based high melting point groups such as cemented carbide, silicon, tungsten, molybdenum, titanium alloy, etc. Wood is used. Further, the production cost is high due to the complexity of the diamond thin film forming apparatus, and furthermore, there are disadvantages such as a narrow range of film forming conditions, which are not always satisfactory as an industrial method.

On the other hand, a material coated with amorphous carbon or a graphite thin film has excellent corrosion resistance and lubricating properties and is useful as an industrial material. As a method of forming such an amorphous carbon or graphite thin film on a base material, a CVD method is known. For example, in forming a diamond thin film by the CVD method, the base material temperature is lowered, and By increasing the concentration of the source, an amorphous carbon or graphite thin film is formed on the substrate. However, such a method of forming an amorphous carbon or graphite thin film by the CVD method has a complicated apparatus and limits the coating area similarly to the above-described method of forming a diamond thin film by the CVD method. It has disadvantages such as unavoidable, and cannot be said to be an industrial method.

[0007]

SUMMARY OF THE INVENTION Under such circumstances, the present invention provides not only iron-based materials but also base materials.
A conductive material can be used irrespective of its melting point, and does not require a complicated device such as a CVD method. It is inexpensive using a simple device and a diamond thin film, a diamond-like carbon thin film or an amorphous material. The purpose of the present invention is to provide an industrial method for forming a carbonaceous coating such as carbon or a graphite thin film on a substrate surface with good adhesion.

[0008]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventor has found that an aqueous solution containing an organic compound or a liquid organic compound is added with an electrolyte or an electrolyte obtained by adding specific particles to an electrolyte. By dipping the material to be coated as a cathode therein and the counter electrode material as an anode and performing DC electrolysis or modulation electrolysis by pulse, a carbonaceous coating is easily formed on the surface of the cathode material with good adhesion. And, by appropriately selecting the electrolysis conditions, it has been found that a diamond thin film, a diamond-like carbon thin film or amorphous carbon or a graphite thin film can be arbitrarily formed as the carbonaceous coating, and based on this finding, the present invention has been completed. Reached.

That is, the present invention relates to an aqueous solution containing an organic compound or a liquid organic compound to which an electrolyte or an electrolyte is added with at least one kind of particles selected from ultrafine carbon particles and fullerene particles. An object of the present invention is to provide a method for forming a carbonaceous coating, comprising: immersing a material to be coated and a counter electrode material; and performing DC electrolysis or pulsed modulation electrolysis using the former as a cathode and the latter as an anode.

[0010] The electrolytic solution used in the method of the present invention comprises:
An organic compound-containing aqueous solution or a liquid organic compound to which an electrolyte or at least one particle selected from ultrafine carbon (including cluster carbon) and fullerene (C ₆₀ , C _70, etc.) particles is added to an electrolyte. In addition, as the electrolyte, for example, acidic substances such as sulfuric acid, hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide, sodium carbonate, potassium carbonate, sodium chloride, potassium chloride, sodium acetate,
And alkali metal salts such as potassium acetate.

On the other hand, examples of the organic compound include monohydric lower alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol and n-propyl alcohol, dihydric alcohols such as ethylene glycol and propylene glycol, formaldehyde, acetaldehyde and the like. Aldehydes, ketones such as acetone and methyl ethyl ketone, ethers such as dimethyl ether, methyl ethyl ether and diethyl ether, diamines such as ethylene diamine, and organic carboxylate salts such as sodium acetate and potassium acetate. Species may be used, or two or more may be used in combination.

In the present invention, the electrolytic solution may be used in the form of an aqueous solution or an organic solution in which the electrolyte is dissolved in a liquid organic compound. When the electrolytic solution is an aqueous solution, the content of each component is usually in the range of 5 to 30% by weight when using an acidic oxide as an electrolyte, and when using an alkali metal hydroxide or salt. Usually, it is selected in the range of 0.1 to 10% by weight. The content of the organic compound is usually selected in the range of 0.5 to 20% by weight. Further, when ultrafine carbon or fullerene particles are used, the amount of addition is 0.5 to 10 g / L with respect to the electrolyte.
Is selected in the range.

On the other hand, when the electrolytic solution is an organic solution using a liquid organic compound as a solvent, the content of the electrolyte is usually 0.5 to
It is selected in the range of 20% by weight. When ultrafine carbon or fullerene particles are used, the amount of addition is selected in the range of 0.5 to 10 g / L with respect to the electrolyte.

The anode material used in the method of the present invention is not particularly limited as long as it has conductivity and is not affected by the electrolyte. For example, a carbon material or ferrite is preferably used. On the other hand, a material to be coated is used for the cathode. The material to be coated is not particularly limited as long as it has conductivity and is not corroded by the electrolytic solution and can withstand the cathode temperature at the time of electrolysis. For example, steel, stainless steel, copper alloy, Magnesium alloy, aluminum, cemented carbide, silicon, tungsten, molybdenum, titanium alloy and the like are used.

When a diamond thin film is formed as the carbonaceous coating, it is desirable to use a high melting point material such as a cemented carbide, silicon, tungsten, molybdenum or titanium alloy for the cathode.

In the method of the present invention, first, an anode 2 and a cathode 1 made of a material to be coated are immersed in an electrolytic solution as shown in FIG. A DC voltage or a pulse voltage is applied in between to perform DC electrolysis or pulse modulated electrolysis. At this time, as the voltage is increased, an electrolytic region, an unstable region and an arc discharge region appear sequentially, and in the unstable region, a reaction between the organic compound and the generated hydrogen occurs by heat and plasma on the surface of the cathode material. An amorphous carbon or graphite thin film is formed on the surface of the cathode material, while in the arc discharge region, the reaction between the organic compound and the generated hydrogen usually occurs by arc discharge on the surface of the cathode material, and diamond is formed on the surface of the cathode material. A thin film is formed. In the intermediate region between the unstable region and the arc discharge region, a diamond-like carbon thin film made of diamond and carbon such as graphite is formed on the surface of the cathode material. In addition, when using ultrafine carbon or fullerene alone or in combination of two or more, it is often intended to form a film having excellent lubrication and corrosion resistance,
For that purpose, it is performed in an electrolytic region or an unstable region.

FIG. 2 is a graph (a) showing the relationship between the current and the voltage, the relationship between the current and the time, the relationship between the temperature and the voltage of the cathode surface, and the relationship between the temperature and the time of the cathode surface.
(B), (c) and (d). In addition, FIG. 3 shows the heating states of the cathode material surface in the electrolytic region, the unstable region and the arc discharge region in this case with explanatory diagrams (a), (b) and (c), respectively.

In the electrolysis according to the method of the present invention, the voltage at which the arc discharge region appears may be up to several hundred volts, so that the method of the present invention is advantageous for industrial implementation. In addition, by adjusting the electrolysis condition region, a diamond thin film, a diamond-like carbon thin film in which carbon such as diamond and graphite are finely mixed, or an amorphous carbon or graphite thin film can be appropriately formed on the surface of a material to be coated. .

[0019]

According to the method of the present invention, a diamond thin film, a diamond-like carbon thin film, an amorphous carbon or a graphite thin film, or an ultra-thin film is formed on the surface of a conductive material very easily and at low cost by an electrolytic method. A conductive film can be formed with good adhesion. Materials provided with a diamond thin film or a diamond-like carbon thin film are:
For example, it is useful as a cutting tool made of a non-ferrous material or a non-metal material, or as a wear-resistant tool or a wear-resistant member required to have high wear resistance.On the other hand, a material provided with amorphous carbon or a graphite thin film is, for example, It is useful as a corrosion-resistant member or a member requiring lubricity.

[0020]

Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

Example 1 DC electrolysis was performed using an aqueous solution containing 1% by weight of sodium hydroxide and 5% by weight of ethylenediamine as an electrolytic solution, a carbon plate as an anode, and a stainless steel plate as a cathode. FIG. 4 shows a current-voltage curve at this time.

The tendency shown in FIG. 4 is the same when ethyl alcohol, acetaldehyde, acetone, ethylene glycol and potassium acetate are used in a concentration of 5% by weight instead of ethylenediamine.

FIG. 5 shows the temperature of the stainless steel plate of the cathode when each of the cathodes was maintained at each potential of 20 V, 40 V, 60 V, 80 V and 140 V for 5 minutes.

Further, the coating film formed at each potential was analyzed by XPS (X-ray Ph
The C / S spectrum was evaluated at 20 V and 60 V as a result of evaluation by T.Electron Spectroscopy.
However, at 80 V and 140 V, the spectrum of graphite and the spectrum of diamond-like carbon in which graphite and diamond were mixed were in agreement.

When a tungsten plate and a molybdenum plate are used as the cathode, the C / S
The spectrum was similar to that of the stainless steel plate. Further, the coating formed in the 180V arc discharge region was consistent with the spectrum of diamond.

Example 2 1 g / L of ultrafine particles containing 15 to 20% by weight of fullerene was added to an electrolyte consisting of an aqueous solution containing 1% by weight of sodium hydroxide and 5% by weight of ethylenediamine.
Was subjected to DC electrolysis at 10 V for 10 minutes in the same manner as in Example 1 except that a graphite plate was used as an anode and a copper plate was used as a cathode. A film was formed. This film was excellent in adhesion without any peeling by cellophane tape, and exhibited a coefficient of friction with steel of 0.02 to 0.03.

Example 3 1% by weight of potassium hydroxide and 5% by weight of ethylenediamine
Fullerene (C
₆₀ ) was added at a rate of 1 g / L, and silver was coated on the alumina ceramics by a silver mirror reaction. 30
V, a 2 μm thick fullerene film was formed by electrolysis for 20 minutes, and the superconducting characteristics were measured.
c) 18K was obtained.

Example 4 An aqueous solution containing 20% by weight of sulfuric acid and 3% by weight of ethylene glycol, which are typical acidic oxides, was prepared.

Next, the electrolytic solution was electrolyzed under the conditions of a DC voltage of 40 V and a current density of 2 A / dm ² using a graphite plate as an anode, the above aqueous solution as an anode, and an aluminum plate as a cathode. A carbon film was formed. Furthermore, using the same electrolyte solution and the pulse power supply by 100A / dm ² of current density and Duty30~
Upon electrolysis at 80%, a dense and smooth coating having a black color of 0.5 to 1.0 μm in thickness was formed. The coefficient of friction of this film was measured using a diamond needle (R = 120 °) and was 0.2, which was much smaller than 0.5 of the aluminum plate.

Example 5 An electrolytic solution comprising an aqueous solution containing sodium hydroxide, potassium hydroxide and 5% by weight of ethylenediamine and having a temperature of 50 ° C. and a pH of 13 was used, a graphite plate was used as an anode, and a magnesium alloy plate was used as a cathode. And DC voltage 60V,
Electrolysis is performed at a current density of 2 A / dm ² for 30 minutes.
A carbon film having a thickness of 2 μm was formed on the magnesium alloy plate of the cathode. The magnesium plate coated with the carbon film was immersed in a 5% by weight aqueous solution of sodium chloride and subjected to a corrosion resistance test. As a result, no rust was generated for 20 days.

On the other hand, when a magnesium alloy plate having no carbon film was subjected to the same corrosion resistance test as above, hydrogen gas was generated from the surface one hour after immersion, and rust was generated.

EXAMPLE 6 1 g / L fullerene (C ₆₀ ) was added to the electrolyte solution of Example 5.
Example 5 was repeated, except that the electrolysis conditions were DC voltage 40 V, current density 1 A / dm ² , and 15 minutes.
In the same manner as in the above, a carbon film having a thickness of 2 μm was formed on the anode plate. The corrosion resistance of the magnesium plate coated with the carbon film was the same as in Example 4.

Example 7 An electrolytic solution obtained by adding sodium chloride to ethylene glycol at a ratio of 5% by weight based on the total weight was used, a graphite plate was used as an anode, and a steel press die (S) was used as a cathode.
DC electrolysis was performed using KD11) to form a diamond-like carbon film having a thickness of 1 to 2 μm on the surface of the steel stamped material of the cathode.

The press die having the diamond-like carbon film formed in this way had a life five times longer than the press die having no coating.

It should be noted that a diamond-like carbon film could be similarly formed by using an electrolytic solution to which potassium acetate was added at a ratio of 5% by weight instead of sodium chloride.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the method of the present invention.

FIG. 2 shows the relationship between current and voltage in the electrolysis of the present invention (a), the relationship between current and time (b), the relationship between cathode temperature and voltage (c), and the relationship between cathode temperature and time (d). A graph showing.

FIG. 3 is an explanatory diagram showing a heating state of a cathode surface in an electrolysis region (a), an unstable region (b), and an arc discharge region (c) in the electrolysis of the present invention.

FIG. 4 is a graph showing a relationship between a DC voltage and a current density in the first embodiment.

FIG. 5 is a graph showing a relationship between a DC voltage and a cathode temperature in Example 1.

[Explanation of symbols]

 1 Cathode (material to be coated) 2 Anode

Claims (4)

(57) [Claims] 1. An electrolyte is added to an organic compound-containing aqueous solution or a liquid organic compound, a material to be coated and a counter electrode material are immersed therein, and DC electrolysis or pulsed modulation electrolysis is performed using the former as a cathode and the latter as an anode. A method for forming a carbonaceous coating, comprising: 2. An organic compound-containing aqueous solution or a liquid organic compound to which an electrolyte is added with at least one particle selected from ultrafine carbon particles and fullerene particles, and a material to be coated therein and a counter electrode. A method for forming a carbonaceous coating, comprising immersing a material and subjecting the former to a cathode and the latter to an anode to perform DC electrolysis or pulse-based modulation electrolysis. 3. The method of claim 1 wherein the carbonaceous coating comprises a diamond film or diamond-like carbon. 4. The method according to claim 1, wherein the carbonaceous coating comprises amorphous carbon or graphite.