JP2006169554A - Carbonaceous film and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a carbonaceous film having a specific structure, and to provide a carbonaceous film having regular holes. <P>SOLUTION: In the method for producing a carbonaceous film, carbonate ions are electrolyzed as potential variation wave shapes (e.g., rectangular waves, sine waves, triangular waves) are controlled in a molten salt comprising a carbonate with a metallic material as the cathode, so as to form a carbonaceous film on the surface of the cathode. Alternatively, in the method for producing a carbonaceous film, carbonate ions are electrolyzed in a molten salt comprising a carbonate with a metallic material as the cathode in such a manner that potential is controlled to 0.7 to 1.2 V, electrolytic time is controlled to 20 to 150 hr, and electric quantity is controlled to 300 to 3,000 C/cm<SP>2</SP>to the area of the cathode, so as to form a carbonaceous film on the surface of the cathode. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a carbonaceous film having a particle deposition structure, a mesostructured carbonaceous film having regularly arranged holes of a unique shape, and a method for producing these carbonaceous films on a cathode surface by electrolysis of a molten salt. About.

  A carbon film formed on an aluminum foil is used as an electrode material for capacitors and capacitors. Moreover, the carbon film formed on the copper foil is used as a lithium ion secondary battery negative electrode material. As described above, the carbon film formed on the metal thin plate is widely used as an electrode material for energy storage devices.

  As a conventional manufacturing method for forming a carbon film on a thin metal plate, there is a method of applying a carbon material on a thin metal plate by a doctor blade method or the like, and a method of adhering a carbon material to a thin metal plate after forming the carbon material in a sheet shape beforehand. Are known.

  However, in the conventional manufacturing method, since a carbon film cannot be directly formed on a metal thin plate, productivity is not good because the carbon film is formed through several steps. Further, since the carbon material is pasted with a large amount of dispersion medium / binder, it is necessary to devise a process for processing a material with low fluidity (see, for example, Patent Document 1). In addition, the carbon material used as an electrode cannot be effectively used because it is covered with a binder, and it is essential to have a conductive agent to improve the electrical contact between the carbon material and the metal sheet. Has become a problem.

In order to solve this problem, a method of coating the cathode aluminum plate with carbon using a cathode reduction reaction of carbonate ions in molten chloride is known. However, there has been a demand for a technology for integrally forming carbon and a thin metal plate with higher performance and improved productivity.
JP 2004-51447 A

  An object of this invention is to provide the manufacturing method of the carbonaceous film which has a peculiar structure, and the carbonaceous film which has a regular hole.

  As a result of intensive studies in view of the above-mentioned problems of the prior art, the present inventor has (1) potential fluctuation when forming a carbonaceous film on the surface of the metal material of the cathode by electrolyzing carbonate ions in the molten salt. By performing electrolysis while controlling the waveform, it is possible to produce a carbonaceous film having a carbonaceous particle deposition structure, and (2) by performing electrolysis for a long time at a constant potential, a hemispherical inverted cone at the lower end The present inventors have found that a mesostructured carbonaceous film having regularly arranged trapezoidal holes can be produced.

That is, the present invention relates to the following production method and carbonaceous film.
Item 1. A method for producing a carbonaceous film in which carbonate ions are electrolyzed in a molten salt containing carbonate using a metal material as a cathode and a carbonaceous film is formed on the surface of the cathode, and the electrolysis is performed while controlling the potential fluctuation waveform. A method for producing a carbonaceous film characterized by the following.
Item 2. Item 2. The method for producing a carbonaceous film according to Item 1, wherein the electrolytic potential waveform is at least one waveform selected from the group consisting of a rectangular wave shape, a triangular wave shape, and a sine wave shape.
Item 3. Item 3. The method for producing a carbonaceous film according to Item 1 or 2, wherein the average potential of electrolysis is 0.7 to 1.2 V based on the cathode limit potential.
Item 4. A method for producing a carbonaceous film in which carbonate ions are electrolyzed in a molten salt containing a carbonate using a metal material as a cathode to form a carbonaceous film on the cathode surface, and the electrolytic potential applied to the electrode is a constant potential. The carbon is characterized in that the set potential is 0.7 to 1.2 V on the basis of the cathode limit potential, the electrolysis time is 20 to 150 hours, and the amount of electricity is 300 to 3000 C / cm ² with respect to the area of the cathode. A method for producing a porous coating.
Item 5. Item 5. The method for producing a carbonaceous film according to any one of Items 1 to 4, wherein the carbonate concentration relative to the molten salt excluding carbonate is 0.001 to 5 mol%.
Item 6. Item 6. The method for producing a carbonaceous film according to any one of Items 1 to 5, wherein the carbonate is at least one selected from potassium carbonate, lithium carbonate, sodium carbonate, and barium carbonate.
Item 7. Item 1. The cathode metal material is at least one metal selected from the group consisting of titanium, zirconium, stainless steel, vanadium, niobium, tantalum, molybdenum, tungsten, chromium, platinum, cobalt, nickel, copper, gold, and aluminum. The manufacturing method of the carbonaceous membrane | film | coat in any one of -6.
Item 8. A carbonaceous film formed on a metal plate, the carbonaceous film having a dense thin film of carbon covering the surface of the metal substrate on a surface in contact with the metal, and the dense thin film from the metal surface A carbonaceous film having a thickness of 0.005 to 10 μm and having a carbonaceous particle deposition structure on the dense thin film.
Item 9. A carbonaceous film formed on a metal plate, having a dense thin film of carbon covering the surface of the metal substrate on the surface of the carbonaceous film in contact with the metal, and a height from the metal surface of 0.005 to 10 μm The carbonaceous particles gather on the dense thin film to form a mesostructure, and the inverted frustoconical holes are regularly arranged in the mesostructure, and the lower ends of the holes are hemispherical, A carbonaceous film having a maximum diameter of 1 to 200 μm and a thickness from the surface of the carbonaceous film contacting the metal to the bottom of the inverted frustoconical hole of 0.005 to 50 μm.

  As described above, the carbonaceous film of the present invention is a carbonaceous film formed on a metal plate, and a carbon thin film covering the surface of the metal substrate is formed on the surface of the carbonaceous film in contact with the metal. And the height from the metal surface of the dense thin film is 0.005 to 10 μm, and has a carbonaceous particle deposition structure on the dense thin film. In this specification, this carbonaceous film may be referred to as a carbonaceous film 1. The carbonaceous film 1 electrolyzes carbonate ions in a molten salt containing carbonate using a metal material as a cathode and forms a carbonaceous film on the cathode surface while performing an electrolysis while controlling a potential fluctuation waveform. Can be manufactured. In the present specification, this manufacturing method may be referred to as manufacturing method 1.

  Furthermore, another carbonaceous film of the present invention is a carbonaceous film formed on a metal plate, and has a dense carbon thin film covering the surface of the metal substrate on the surface of the carbonaceous film in contact with the metal. The height from the metal surface is 0.005 to 10 μm, carbonaceous particles gather on the dense thin film to form a mesostructure, and the inverted frustoconical holes are regularly arranged in the mesostructure, The lower end of the hole is hemispherical, the maximum diameter of the hole is 1 to 200 μm, and the thickness from the surface of the carbonaceous film in contact with the metal to the bottom of the inverted frustoconical hole is 0.005 to 50 μm. In the present specification, this carbonaceous film may be referred to as a carbonaceous film 2. The carbonaceous film 2 uses a metal material as a cathode to electrolyze carbonate ions in a molten salt containing carbonate, and when the carbonaceous film is formed on the cathode surface, the electrolytic potential applied to the electrode is a constant potential. It can be produced by setting the electrolysis time to 20 to 150 hours. In this specification, this manufacturing method may be referred to as manufacturing method 2.

1. Carbonaceous film 1 and manufacturing method 1
In the production method 1 of the present invention, the fluctuation waveform of the potential applied to the electrode is controlled in the electrolysis of carbonate ions in the molten salt containing carbonate. Such a process can usually be carried out in an electrolytic bath. Control of the potential fluctuation waveform refers to changing the potential applied to the electrode during electrolysis, and is different from constant potential control in which the potential is kept constant.

  The carbonate is a raw material for the carbonaceous film formed on the cathode by electrolysis. Carbonates are usually used in the form of molten salts. As the carbonate, alkali metal carbonates such as sodium carbonate, lithium carbonate and potassium carbonate, alkaline earth metal carbonates such as barium carbonate and the like are usually used alone or in combination of two or more. Preferred carbonates are sodium carbonate, lithium carbonate, potassium carbonate, and barium carbonate, and a more preferred carbonate is potassium carbonate.

These carbonates are electrolyzed in the molten salt. As the molten salt, alkali metal halides, hydroxides, alkaline earth metal halides, hydroxides, and the like are usually used alone or in combination of two or more. Alkali metal halides include lithium, sodium, potassium, rubidium, cesium fluoride, chloride, bromide and iodide. Alkaline earth metal halides include magnesium, calcium, strontium, barium fluoride, chloride, bromide, and iodide. Preferred molten salts are alkali metal chlorides, alkali metal fluorides, alkali metal bromides, and alkali metal iodides, and more preferred are alkali metal chlorides. Among the alkali metal chlorides, the alkali metal chloride molten salts shown below are particularly preferable.
Lithium chloride: potassium chloride = 35 to 100 mol%: 65 to 0 mol%, preferably 55 to 65 mol%: 45 to 35 mol%.
Lithium chloride: potassium chloride = 30 to 70 mol%: 70 to 30 mol%, preferably 45 to 55 mol%: 55 to 45 mol%.
Lithium chloride: potassium chloride: cesium chloride = 57.5: 13.3: 29.2 mol%.

  The concentration of the carbonate with respect to the molten salt excluding the carbonate is usually 0.001 to 5 mol%, preferably 0.1 to 1.5 mol%, more preferably 0.2 to 1 mol%. If the carbonate concentration is low, a dense carbonaceous film tends to be obtained.

  In addition to the above-mentioned salts, additives used for molten salt electrolysis, such as dissolution aids and electrolytic aids, may be added to the molten salt as necessary. What is necessary is just to set suitably according to electrolysis conditions, such as a composition, electrolysis temperature, a current density, and the amount of electricity supply.

  On the other hand, an anode and a cathode are essential as electrodes, and a reference electrode can be used as necessary. As the anode, an anode material usually used in molten salt electrolysis can be used. For example, glassy carbon, graphite, conductive ceramics and the like. The shape and size of the anode are not particularly limited.

  As the cathode, at least one metal selected from the group consisting of Group 4A, Group 5A, Group 6A, Group 7A, Group 8, Group 1B, Group 2B, and Group 3B can be used. Preferred are aluminum, copper, titanium, zirconium, stainless steel, vanadium, niobium, tantalum, molybdenum, tungsten, chromium, platinum, cobalt, nickel, gold, and more preferred are aluminum, copper, and nickel. The shape and size of the cathode are not particularly limited, but when a metal having a complex shape with irregularities is used as the cathode, a metal having a carbonaceous film shaped along the irregularities can be obtained. Therefore, when it is used as a metal integrated with a carbonaceous film formed on the cathode surface, it is desirable to have a shape and size suitable for the purpose of use from the point of electrolysis. If necessary, the cathode surface can be subjected to pretreatment such as degreasing, chemical polishing (for example, sodium hydroxide aqueous solution treatment), mechanical polishing, etc. before electrolysis.

The reference electrode is useful for accurately grasping the potential. Therefore, by using the reference electrode and accurately grasping the potential, it becomes possible to more accurately control the carbonaceous film formation speed, film shape, and the like. As the reference electrode material, a reference electrode material usually used in molten salt electrolysis can be used. For example, an Ag ⁺ / Ag electrode can be used.

  The average potential applied to the electrode is usually 0.7 to 1.2 V, preferably 0.8 to 1.1 V, based on the cathode limit potential. The cathode limit potential indicates the deposition metal and ions in the bath when an alkali metal or alkaline earth metal in the molten salt is deposited by applying a large current using a nickel wire as an electrode. Equilibrium potential. When the average potential is within this range, impurities such as Li contained in the carbonaceous film are reduced, and a more uniform carbonaceous film can be obtained. As the potential waveform in the potential fluctuation waveform control, a rectangular wave shape, a triangular wave shape, a sine wave shape, or the like can be usually used alone or in combination of two or more. Further, the difference between the lowest potential and the highest potential in electrolysis is usually 0.01 to 0.6 V, preferably 0.1 to 0.5 V, and more preferably 0.1 to 0.4 V. One period (frequency) of the waveform is usually 0.01 to 300 sec (100 to 0.0033 Hz), preferably 1 to 100 sec (1 to 0.01 Hz).

  The electrolysis temperature is not particularly limited, and can be appropriately set according to the melting point of the molten salt, the formation state of the carbonaceous film, and the like. Usually, it is 250-700 degreeC, Preferably it is 400-500 degreeC. Electrolysis is usually performed under atmospheric pressure, but it can also be performed under pressure and reduced pressure. As the electrolysis atmosphere, nitrogen, argon, neon, carbon dioxide, or the like is usually used. The electrolysis time may be appropriately set according to the type or concentration of the molten salt, temperature, energization amount, etc., and is usually 0.1 to 100 hours, preferably 5 to 50 hours.

  If necessary, preliminary electrolysis (preliminary electrolysis) can be performed before electrolysis while controlling the potential fluctuation waveform. Preliminary electrolysis provides effects such as improved adhesion between the metal plate and the carbonaceous film and improved denseness of the dense thin film. The preliminary electrolysis may be constant potential electrolysis or potential fluctuation electrolysis. The constant potential in the constant potential electrolysis and the average potential in the variable potential electrolysis should be smaller than the average potential in the subsequent main electrolysis, but preferably 0.05 to 0.3 V lower. For example, the constant potential and the average potential in the preliminary electrolysis are preferably 0.4 to 1.15 V, more preferably 0.4 to 0.9 V, and even more preferably 0.7 to 0.8 V. The electrolysis time in the preliminary electrolysis is usually 1 to 1800 seconds, preferably 5 to 600 seconds.

  Hereinafter, an example of the production method 1 of the present invention will be described with reference to FIG.

  A holder (3) is installed in the electric furnace (1), and a high-purity alumina crucible (2) as an electrolytic cell is installed in the holder. The holder is provided with an introduction pipe (4) for introducing atmospheric gas such as argon, and (5) an exhaust pipe for discharging, and the atmospheric gas is circulated through these pipes. In the crucible, a molten salt obtained by melting an alkali metal halide or the like is used as a solvent (6). A thermocouple (7) is provided in the crucible, and the temperature of the solvent is measured with this thermocouple, and the temperature of the electric furnace is adjusted as necessary to adjust the temperature of the solvent. In a state where the atmospheric gas is circulated, a carbonate such as potassium carbonate as a raw material for the carbonaceous film is added to the solvent to obtain a molten salt. Next, an electrochemical measurement device (11) is connected to the anode (8), cathode (9) and reference electrode (10) provided in the crucible, and electrolysis is performed by controlling the potential, current, etc., and carbon is applied to the cathode surface. A pellicle is formed. When the carbonaceous film formed on the cathode surface is heat-treated, moisture and the like are eliminated, and the homogeneity is further improved.

The carbonaceous film 1 of the present invention can be produced by the production method 1, and is a carbonaceous film formed on a metal plate, and covers the surface of the metal substrate on the surface of the carbonaceous film that contacts the metal. The dense thin film has a height from the metal surface of 0.005 to 10 μm, and has a carbonaceous particle deposition structure on the dense thin film. The carbonaceous film 1 can be obtained by the production method 1 described above. The metal plate is a cathode material of production method 1. The carbonaceous film 1 has a dense thin film in which carbonaceous particles are dense on the surface in contact with the metal plate, and the thin film is usually 0.005 to 10 μm, preferably 0.05 to 5 μm from the surface in contact with the metal plate. Has a height of about. The carbonaceous particle deposition structure is a shape in which carbonaceous particles are gathered to form a little lump such as a fish egg (for example, octopus, which is a gathering of eggs) or a dumpling. The carbonaceous film obtained by conventional constant potential short-time electrolysis has a bulky dendritic structure formed by agglomeration of carbonaceous particles on a slightly dense thin film, and the dendritic film The structure was a film having a relatively low carbonaceous density as compared with the carbonaceous particle deposition structure of the film of the present invention. The density of the volume structure of carbonaceous particles is usually 0.23 to 1.6 g / cm ³ , preferably 0.4 to 1.3 g / cm ³ . The density of the dense thin film is usually, 1.1 to 2.2 g / cm ^3, preferably 1.4~2.2 g / cm ^3. The thickness of the entire carbonaceous film 1 is not particularly limited, but is usually 1 to 500 μm, preferably 5 to 200 μm, and more preferably 10 to 100 μm.

  Since the carbonaceous film 1 is excellent in adhesion to the metal plate, it is particularly useful in the field where the carbonaceous film is used integrally with the metal plate. For example, it is useful for preventing metal corrosion, improving slidability, improving wear resistance, and improving lubricity.

2. Carbonaceous film 2 and manufacturing method 2
In the production method 2 of the present invention, in the production of a carbonaceous film for forming a carbonaceous film on the surface of the cathode, when a carbonate ion is electrolyzed in a molten salt containing a carbonate using a metal material as a cathode, it is applied to the electrode. The electrolysis potential is constant, the set potential is 0.7 to 1.2 V based on the cathode limit potential, the electrolysis time is 20 to 150 hours, and the amount of electricity is 300 to 3000 C / cm ² with respect to the area of the cathode. It is characterized by being. Such a process can usually be carried out in an electrolytic bath. The constant potential means that the potential applied to the electrode during electrolysis is made constant.

  The carbonate is a raw material for the carbonaceous film formed on the cathode by electrolysis. Carbonates are usually used in the form of molten salts. As the carbonate, alkali metal carbonates such as sodium carbonate, lithium carbonate and potassium carbonate, and alkaline earth metal carbonates such as barium carbonate are usually used alone or in combination of two or more. Preferred carbonates are sodium carbonate, lithium carbonate, potassium carbonate, and barium carbonate, and a more preferred carbonate is potassium carbonate.

These carbonates are electrolyzed in the molten salt. As the molten salt, alkali metal halides, hydroxides, alkaline earth metal halides, hydroxides, and the like are usually used alone or in combination of two or more. Alkali metal halides include lithium, sodium, potassium, rubidium, cesium fluoride, chloride, bromide and iodide. Alkaline earth metal halides include magnesium, calcium, strontium, barium fluoride, chloride, bromide, and iodide. Preferred molten salts are alkali metal chlorides, alkali metal fluorides, alkali metal bromides, and alkali metal iodides, and more preferred are alkali metal chlorides. Among the alkali metal chlorides, the alkali metal chloride molten salts shown below are particularly preferable.
Lithium chloride: potassium chloride = 35 to 100 mol%: 65 to 0 mol%, preferably 55 to 65 mol%: 45 to 35 mol%.
Lithium chloride: potassium chloride = 30 to 70 mol%: 70 to 30 mol%, preferably 45 to 55 mol%: 55 to 45 mol%.
Lithium chloride: potassium chloride: cesium chloride = 57.5: 13.3: 29.2 mol%.

  The carbonate concentration relative to the molten salt excluding carbonate is usually 0.001 to 5 mol%, preferably 0.05 to 1.5 mol%, more preferably 0.1 to 1 mol%. If the carbonate concentration is low, a dense carbonaceous film tends to be obtained.

  In addition to the above-mentioned salts, additives used for molten salt electrolysis, such as dissolution aids and electrolytic aids, may be added to the molten salt as necessary. What is necessary is just to set suitably according to electrolysis conditions, such as a composition, electrolysis temperature, a current density, and the amount of electricity supply.

  On the other hand, an anode and a cathode are essential as electrodes, and a reference electrode can be used as necessary. As the anode, an anode material usually used in molten salt electrolysis can be used. For example, glassy carbon, graphite, conductive ceramics and the like. The shape and size of the anode are not particularly limited.

  As the cathode, at least one metal selected from the group consisting of Group 4A, Group 5A, Group 6A, Group 7A, Group 8, Group 1B, Group 2B, and Group 3B can be used. Preferably, aluminum, copper, titanium, zirconium, stainless steel, vanadium, niobium, tantalum, molybdenum, tungsten, chromium, platinum, cobalt, nickel, gold, etc., more preferably aluminum, copper, nickel, and more preferably Is copper. The shape and size of the cathode are not particularly limited, but when a metal having a complex shape with irregularities is used as the cathode, a metal having a carbonaceous film shaped along the irregularities can be obtained. Therefore, when it is used as a metal integrated with a carbonaceous film formed on the cathode surface, it is desirable to have a shape and size suitable for the purpose of use from the point of electrolysis. If necessary, the cathode surface can be subjected to pretreatment such as degreasing, chemical polishing (for example, sodium hydroxide aqueous solution treatment), mechanical polishing, etc. before electrolysis.

The reference electrode is useful for accurately grasping the potential. Therefore, by using the reference electrode and accurately grasping the potential, it becomes possible to more accurately control the carbonaceous film formation speed, film shape, and the like. As the reference electrode material, a reference electrode material usually used in molten salt electrolysis can be used. For example, an Ag ⁺ / Ag electrode can be used.

  The potential applied to the electrode is constant, and is usually 0.75 to 1.2 V, preferably 0.85 to 1.1 V, based on the cathode limit potential. When the potential is within this range, impurities such as Li contained in the carbonaceous film are reduced, and a more uniform carbonaceous film can be obtained.

Further, the energization amount of electricity during the electrolysis of the area of the cathode, usually 300~3000C / cm ^2, preferably 700~1500C / cm ^2.

  The electrolysis temperature is not particularly limited, and can be appropriately set according to the melting point of the molten salt, the formation state of the carbonaceous film, and the like. Usually, it is 250-700 degreeC, Preferably it is 400-500 degreeC. Electrolysis is usually performed under atmospheric pressure, but it can also be performed under pressure and reduced pressure. As the electrolysis atmosphere, nitrogen, argon, neon, carbon dioxide, or the like is usually used. The electrolysis time is important and can be appropriately changed according to the type or concentration of the molten salt, temperature, amount of energization, etc., but is usually 20 to 150 hours, preferably 40 to 100 hours. If the electrolysis time is too long, the hole of the carbonaceous film 2 to be obtained (a hole having a hemispherical inverted frustoconical shape) may be small.

  If necessary, preliminary electrolysis (preliminary electrolysis) can be performed before electrolysis while controlling the potential fluctuation waveform. Preliminary electrolysis provides effects such as improved adhesion between the metal plate and the carbonaceous film and improved denseness of the dense thin film. The preliminary electrolysis may be constant potential electrolysis or potential fluctuation electrolysis. The constant potential in the constant potential electrolysis and the average potential in the variable potential electrolysis should be smaller than the average potential in the subsequent main electrolysis, but preferably 0.05 to 0.3 V lower. For example, the constant potential and the average potential in the preliminary electrolysis are preferably 0.4 to 1.15 V, more preferably 0.4 to 0.9 V, and even more preferably 0.7 to 0.8 V. The electrolysis time in the preliminary electrolysis is usually 1 to 1800 seconds, preferably 5 to 600 seconds.

  Hereinafter, an example of the production method 2 of the present invention will be described with reference to FIG.

  A holder (3) is installed in the electric furnace (1), and a high-purity alumina crucible (2) as an electrolytic cell is installed in the holder. The holder is provided with an introduction pipe (4) for introducing atmospheric gas such as argon, and (5) an exhaust pipe for discharging, and the atmospheric gas is circulated through these pipes. In the crucible, a molten salt obtained by melting an alkali metal halide or the like is used as a solvent (6). A thermocouple (7) is provided in the crucible, and the temperature of the solvent is measured with this thermocouple, and the temperature of the electric furnace is adjusted as necessary to adjust the temperature of the solvent. In a state where the atmospheric gas is circulated, a carbonate such as potassium carbonate as a raw material for the carbonaceous film is added to the solvent to obtain a molten salt. Next, an electrochemical measurement device (11) is connected to the anode (8), cathode (9) and reference electrode (10) provided in the crucible, and the electrolysis is performed for a long time by controlling the potential to be constant. A carbonaceous film is formed. When the carbonaceous film formed on the cathode surface is baked, moisture and the like are eliminated and the homogeneity is further improved.

The carbonaceous film 2 of the present invention can be produced by the production method 2 described above, and is a carbonaceous film formed on a metal plate, and covers the surface of the metal substrate on the surface in contact with the metal of the carbonaceous film. A dense carbon thin film, the height from the metal surface is 0.005 to 10 μm, and carbonaceous particles gather on the dense thin film to form a mesostructure, and the mesostructure has an inverted frustoconical shape. Are regularly arranged, the lower end of the hole is hemispherical, the maximum diameter of the hole is 1 to 200 μm, and the surface of the carbonaceous film contacting the metal to the bottom of the inverted frustoconical hole The thickness is 0.005 to 50 μm (the upper part of FIG. 7). Here, the mesostructure refers to a carbonaceous film having the above-mentioned holes formed by porous carbon particles. The metal plate is a cathode material of production method 2. The carbonaceous film 2 has a dense thin film in which carbonaceous particles are dense on the surface in contact with the metal plate, and the thin film is usually 0.005 to 10 μm, preferably 0.05 to 5 μm from the surface in contact with the metal plate. Has a height of about. In the carbonaceous film 2, the above holes are regularly arranged in the mesostructure on the thin film. Also, the bottom of the hole may penetrate the mesostructure and reach the thin film. The hole has a shape in which the upper surface of the truncated cone is hemispherical and is turned upside down so that the hemispherical portion faces the thin film side (the lower stage in FIG. 7). Therefore, the maximum diameter of the hole gradually increases from the bottom to the top of the hole. Therefore, when this hole is cut from top to bottom (thin film side), the cut surface is similar to the shape of the alphabet U or the shape of the V-shaped valley. The maximum diameter is usually 1 to 200 μm, preferably 30 to 150 μm, more preferably 50 to 100 μm. The depth of the hole is 1 to 300 μm, preferably 20 to 150 μm. There are usually 10 to 1000, preferably 50 to 300, holes per 1 mm ² . The thickness of the carbonaceous film 2 is usually 10 to 500 μm, preferably 150 to 300 μm.

  Since the carbonaceous film 2 has excellent adhesion to the metal plate and has unique holes, it is particularly useful as a field where the carbonaceous film is used integrally with the metal plate, an array for producing nanoparticles, and the like. For example, a high-density magnetic recording medium, a high-intensity electroluminescent element, or the like can be formed by embedding a ferromagnetic material, a metal, a semiconductor, or the like in the hole, as in the case of producing nanoparticles using a nanohole array using porous alumina. It is also useful for preventing metal corrosion, improving slidability, improving wear resistance, and improving lubricity.

  The carbonaceous film 1 of the present invention has a significant increase in specific surface area and electric double layer capacity compared to conventional carbonaceous films. Moreover, since the carbonaceous film 2 of the present invention has regularly aligned holes, it can be used as a nanohole array.

  The carbonaceous films 1 and 2 of the present invention can be used for applications where conventional carbonaceous films have been used. For example, catalysts, electrodes, heating elements, structures, gaskets, heat insulators, heat sinks, corrosion-resistant sealing materials, brushes for electric machines, X-ray or neutron monochromators, reactor moderators, battery separators, metal corrosion prevention It is useful as such. The carbonaceous film 1 is particularly useful for catalysts and electrodes, and the carbonaceous film 2 is particularly useful for electrodes, structures, and heat sinks.

  Further, according to the production method 1 of the present invention, the carbonaceous film 1 having a carbonaceous particle deposition structure can be produced, and according to the production method 2, the carbonaceous film 2 having a structure in which unique holes are regularly arranged. Can be manufactured. Furthermore, according to the production methods 1 and 2 of the present invention, it is possible to form a carbonaceous film excellent in adhesion, smoothness, and homogeneity on a metal surface having a complicated shape such as unevenness.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by these Examples.

Example 1
In an electrolytic bath, 300 g of a mixture of LiCl (58.5 mol%) and KCl (41.5 mol%) mixed in an eutectic composition was vacuum dried at 200 ° C., and then melted at 450 ° C. in an argon atmosphere. did. The solvent K ₂ CO ₃ was added in an amount of 0.50 mole% and the resulting melt was molten salt for electrolysis. A 50 μm thick aluminum foil whose surface was chemically polished with a 5N NaOH aqueous solution was used as the cathode, glassy carbon was used as the anode, and an Ag ⁺ / Ag electrode was used as the reference electrode. While maintaining 450 ° C., the minimum potential based on Li ⁺ / Li was 0.80 V, the maximum potential was 1.00 V, the potential was swept at 10 mV / sec, and electrolysis was performed for 18 hours. After the electrolysis, the cathode was lifted from the molten salt, and the carbonaceous film obtained on the cathode surface was washed with distilled water and then with ethanol to obtain an aluminum foil having a carbonaceous film. The cross section obtained by cutting the obtained aluminum foil was observed with a scanning electron microscope. In addition, at the time of manufacture by electrolysis, the substrate was covered with a carbonaceous film, and there was no peeling. The observation results are shown in FIG. The upper photograph in FIG. 2 is a photograph showing a cross section of the carbonaceous film. Aggregates of particulate carbon are present in a fish egg shape at a height of about 100 μm on a dense thin film with a thickness of several μm. The lower part of FIG. 2 is an enlarged photograph of an aggregate of particulate carbon existing in the upper part of the thin film, and many particles having a size of about 1 to 2 μm are seen.

Example 2
A carbonaceous film was produced in the same manner as in Example 1 except that the minimum potential was 0.90 V, the maximum potential was 1.10 V, and the electrolysis time was 19.4 hours. The cross section obtained by peeling was observed with a scanning electron microscope. . In addition, at the time of manufacture by electrolysis, the substrate was covered with a carbonaceous film, and there was no peeling. The observation results are shown in FIG. In the upper part of FIG. 3, unlike the upper part of FIG. 2, the white part of the upper half is the substrate side, and the slightly white part of the lower half is the grown carbonaceous film part. Aggregates of particulate carbon existed in the shape of fish eggs at a height of about 100 μm on a dense thin film with a thickness of several μm. The lower part of FIG. 3 is an enlarged photograph of the aggregate of particulate carbon existing on the upper part of the dense thin film, and many particles having a size of about 0.5 to 1 μm were observed.

Example 3
Example 1 except that a 1.0 mm thick aluminum plate surface-treated with # 600 abrasive paper was used as the cathode, the K ₂ CO ₃ concentration was 0.20 mol%, the maximum potential was 1.2 V, and the electrolysis time was 18.7 hours. A carbonaceous film was produced in the same manner as described above, and the cross section was observed with a scanning electron microscope. The observation results are shown in FIG. In the upper part of FIG. 4, the carbonaceous film is peeled off from the substrate, which is peeled off when the aluminum plate is bent 180 ° for microscopic photography, and the substrate is covered with the carbonaceous film during production by electrolysis. There was no peeling. A dense thin film having a thickness of less than 10 μm was observed. The lower part of FIG. 4 is an enlarged photograph of the aggregate of particulate carbon existing on the upper part of the dense thin film, and many particles having a size of about several hundred nm were observed.

Example 4
A 1.0 mm thick aluminum plate surface-treated with # 600 abrasive paper was used as the cathode, the K ₂ CO ₃ concentration was 0.20 mol%, the minimum potential was 0.75 V, the maximum potential was 1.2 V, and the electrolysis time was 17.7 hours. A carbonaceous film was produced in the same manner as in Example 1 except that the surface was observed with a scanning electron microscope. The observation results are shown in FIG. In the upper part of FIG. 5, the carbonaceous film is peeled off from the substrate, which is peeled off when the aluminum plate is bent 180 ° for microscopic photography, and the substrate is covered with the carbonaceous film during production by electrolysis. There was no peeling. A dense thin film having a thickness of about 5 μm was observed. The lower part of FIG. 5 is an enlarged photograph of the aggregate of particulate carbon existing on the upper part of the dense thin film, and many particles having a size of about several μm were observed.

Example 5
A 1.0 mm thick aluminum plate surface-treated with # 600 abrasive paper was used as the cathode, the K ₂ CO ₃ concentration was 0.20 mol%, the minimum potential was 0.72 V, the maximum potential was 1.2 V, and the electrolysis time was 17.2 hours. A carbonaceous film was produced in the same manner as in Example 1 except that the cross section was observed with a scanning electron microscope. The observation results are shown in FIG. In the upper part of FIG. 6, the carbonaceous film is peeled off from the substrate, but this is peeled off when the aluminum plate is bent 180 ° for microscopic photography, and the substrate is covered with the carbonaceous film during the production by electrolysis. There was no peeling. A dense thin film having a thickness of about 10 μm was observed. The lower part of FIG. 5 is an enlarged photograph of an aggregate of particulate carbon existing on the upper part of the dense thin film, and many particles having a size of about 1 μm were observed.

Example 6
Example 1 except that a 1.0 mm thick copper plate surface-treated with # 600 abrasive paper was used as the cathode, the K ₂ CO ₃ concentration was 0.20 mol%, and the electrolysis time was 90 hours as the cathode. A carbonaceous film was produced in the same manner as described above, and the surface was observed with a scanning electron microscope. The observation results are shown in FIGS. In the upper part of FIG. 7, it was observed that a unique carbonaceous film having regularly arranged holes was formed on the substrate. In the lower part of FIG. 7, it was observed that the thickness of the dense thin film was several tens of μm. It was also observed that there were many holes with a diameter of about 50 to 80 μm and a depth of about 100 μm.

Comparative Example 1
A carbonaceous film was produced in the same manner as in Example 6 except that the potential was 1.00 V and the electrolysis time was 24.0 hours, and the cross section was observed with a scanning electron microscope. The observation results are shown in FIG. It was observed that carbonaceous particles were irregularly aggregated on a thin film having a thickness of about 5 μm, and particle aggregates having a bulky structure were present sparsely.

  The carbonaceous film obtained by the present invention can be used for applications where a conventional carbonaceous film has been used. For example, as electrodes, heating elements, structures, gaskets, heat insulators, heat sinks, corrosion-resistant sealing materials, brushes for electric machines, X-ray or neutron monochromators, moderators for reactors, battery separators, metal corrosion prevention, etc. Useful.

It is the schematic of a molten salt electrolysis apparatus. It is a cross-sectional photograph (upper stage) and carbon particles (lower stage) of the carbonaceous film obtained in Example 1. It is a cross-sectional photograph (upper stage) and carbon particles (lower stage) of the carbonaceous film obtained in Example 2. It is the surface photograph (upper stage) and carbon particle (lower stage) of the carbonaceous membrane | film | coat obtained in Example 3. FIG. It is the surface photograph (upper stage) and carbon particle (lower stage) of the carbonaceous membrane | film | coat obtained in Example 4. FIG. It is the surface photograph (upper stage) and carbon particle (lower stage) of the carbonaceous membrane | film | coat obtained in Example 5. FIG. It is the surface photograph (upper stage) of the carbonaceous film obtained in Example 6, and the cross-sectional photograph (lower stage) of this carbonaceous film. It is the surface photograph (upper stage) of the carbonaceous membrane | film | coat obtained in Example 6, and the surface photograph further expanded (lower stage). Sectional photographs (upper and lower stages) of the carbonaceous film obtained in Example 6. In the upper photo, the lower part of the photo is the surface in contact with the metal plate. In the lower photograph, the upper left of the photograph is the surface in contact with the metal plate. 4 is a cross-sectional photograph of a carbonaceous film obtained in Comparative Example 2.

Explanation of symbols

1 Electric furnace 2 Crucible 3 Holder 4 Introduction pipe 5 Exhaust pipe 6 Solvent 7 Thermocouple 8 Anode 9 Cathode 10 Reference electrode 11 Electrochemical measuring device

Claims (9)

A method for producing a carbonaceous film in which carbonate ions are electrolyzed in a molten salt containing carbonate using a metal material as a cathode and a carbonaceous film is formed on the surface of the cathode, and the electrolysis is performed while controlling the potential fluctuation waveform. A method for producing a carbonaceous film characterized by the following. The method for producing a carbonaceous film according to claim 1, wherein the waveform of the electrolytic potential is at least one waveform selected from the group consisting of a rectangular wave shape, a triangular wave shape, and a sine wave shape. The method for producing a carbonaceous film according to claim 1 or 2, wherein an average potential of electrolysis is 0.7 to 1.2 V on the basis of a cathode limit potential. A method for producing a carbonaceous film in which carbonate ions are electrolyzed in a molten salt containing a carbonate using a metal material as a cathode to form a carbonaceous film on the cathode surface, and the electrolytic potential applied to the electrode is a constant potential. The carbon is characterized in that the set potential is 0.7 to 1.2 V on the basis of the cathode limit potential, the electrolysis time is 20 to 150 hours, and the amount of electricity is 300 to 3000 C / cm ² with respect to the area of the cathode. A method for producing a porous coating. The method for producing a carbonaceous film according to any one of claims 1 to 4, wherein the concentration of the carbonate with respect to the molten salt excluding the carbonate is 0.001 to 5 mol%. The method for producing a carbonaceous film according to any one of claims 1 to 5, wherein the carbonate is at least one of potassium carbonate, lithium carbonate, sodium carbonate, and barium carbonate. The metal material of the cathode is at least one metal selected from the group consisting of titanium, zirconium, stainless steel, vanadium, niobium, tantalum, molybdenum, tungsten, chromium, platinum, cobalt, nickel, copper, gold and aluminum. The manufacturing method of the carbonaceous membrane | film | coat in any one of 1-6. A carbonaceous film formed on a metal plate, the carbonaceous film having a dense thin film of carbon covering the surface of the metal substrate on a surface in contact with the metal, and the dense thin film from the metal surface A carbonaceous film having a thickness of 0.005 to 10 μm and having a carbonaceous particle deposition structure on the dense thin film. A carbonaceous film formed on a metal plate, having a dense thin film of carbon covering the surface of the metal substrate on the surface of the carbonaceous film in contact with the metal, and a height from the metal surface of 0.005 to 10 μm The carbonaceous particles gather on the dense thin film to form a mesostructure, and the inverted frustoconical holes are regularly arranged in the mesostructure, and the lower ends of the holes are hemispherical, A carbonaceous film having a maximum diameter of 1 to 200 μm and a thickness from the surface of the carbonaceous film contacting the metal to the bottom of the inverted frustoconical hole of 0.005 to 50 μm.

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