JP6082935B2 - Manufacturing method of conductive material - Google Patents

Description

  The present invention relates to a method for producing a conductive material having excellent electrical conductivity that can be suitably used as an electrode used in, for example, a battery, an ozone water generator, an electrolyzer, and the like.

  Electrodes used for batteries, electrolyzers and the like are required to have high corrosion resistance that does not deteriorate for a long time even in a corrosive electrolytic solution as well as high conductivity. Conventionally, platinum has been used as an electrode having high conductivity and corrosion resistance. However, since the cost is high, development of a technique for using titanium, which is relatively inexpensive and excellent in corrosion resistance, for the electrode has been advanced. However, since titanium easily oxidizes and its surface tends to become almost insulating titanium oxide, there is a problem that it is limited to application to electrodes that require high conductivity, and there is a problem of technology for improving conductivity. Development is desired.

  On the other hand, in Patent Document 1, a titanium oxide layer is formed on the surface of a titanium material, a noble metal layer such as Au, Pt, Pd, etc. is formed on the surface by a PVD method, and then the surface treatment of the electrode titanium material to be heat-treated. A method is disclosed. In Patent Document 2, in order to firmly bond and hold an electrode active substance on the surface of a conductive substrate made of titanium or a titanium alloy, the surface of the conductive substrate is made porous by electrolytic oxidation in an electrolyte solution. An electrode manufacturing method is disclosed in which an electrode active material such as a platinum group metal is formed in a layer on the surface of a conductive substrate. Patent Document 3 discloses a method for producing porous titanium foam in which a titanium carbonitride layer is formed on the surface of a porous skeleton by carbonitriding porous titanium foam. In Patent Document 4, as a method for producing titanium nitride powder applied as a raw material for cermet, a mixture of titanium oxide powder and carbon powder is heated in nitrogen gas at a temperature of 1350 ° C. or higher and below the melting point of titanium. A method is disclosed. In Patent Document 5, as a method for producing titanium nitride powder applied as a raw material for cermet, titanium oxide and carbon powder are mixed, kneaded with a binder, granulated into granulated pellets, and then 1500 to 1800 degrees in a nitrogen stream. And a method of obtaining a titanium carbonitride powder by pulverizing with a pulverizer. In Patent Document 6, as a technique for modifying the surface of a titanium-based material, the titanium-based material is accommodated in a heating furnace and heat-treated at 600 to 900 ° C. in a carbon dioxide atmosphere. And a method of forming a carbon diffusion layer has been proposed. Patent Document 7 discloses a method of manufacturing an electron source that can be used for a field emission display, a step of forming an aluminum anodic oxide film on at least a substrate, a hydrocarbon as a source gas, and a temperature lower than the decomposition temperature of the source gas. A technique of depositing a carbonaceous material in close contact with the bottom of the pores of the aluminum anodic oxide film by vapor phase carbonization, and further forming a fibrous carbonaceous material inside the pores. Is disclosed.

JP 2009-228123 A JP 2009-197284 A JP 2006-348330 A Japanese Unexamined Patent Publication No. 1-96005 JP-A-8-333107 JP 2003-73799 A JP 2003-31115 A

  In Patent Document 1, since a special and expensive PVD apparatus is required, there are cases where the cost burden is large and the introduction of the equipment is difficult. Further, the processing steps are complicated, the number of steps is large, and the production efficiency is poor. In addition, since it is necessary to use a noble metal such as Au or Pt as a material, the cost of the product after the surface treatment is increased, and the surface of the noble metal layer is smooth, resulting in a small surface area. There was a risk that a significant improvement in conductivity could not be expected. In Patent Document 2, since the electrode active substance is deeply and complicatedly penetrated into the porous pores of the conductive substrate and fixed on the substrate surface to be firmly bonded and held by the anchor effect, the electrode surface area is small. There was a risk of becoming. Furthermore, since it is necessary to ensure the target amount of electrode active substance by repeating the process of applying, drying and firing the metal salt solution to the substrate surface several times to several tens of times, the process is complicated and the production efficiency is poor. was there. In addition, since it is necessary to use an expensive platinum group metal or the like as a material, there is a problem that the cost of the manufactured electrode is increased. In Patent Document 3, in the process of forming porous titanium, in addition to titanium powder, various materials such as a binder, a plasticizer, a foaming agent, and a foaming agent are required, and foaming slurry is formed, dried, degreased, Since it includes sintering and the like, it becomes complicated and complicated. Since it is necessary to perform carbonitriding after forming the porous titanium, the entire manufacturing process is complicated and complicated, and the production efficiency is poor. Patent Documents 4 and 5 are techniques for producing titanium nitride or titanium carbonitride powder as a raw material for cermet, but it is necessary to heat treatment at a relatively high temperature in order to nitride or carbonitride titanium oxide powder. In addition, high costs are required for heating equipment, and in the case of small and medium-sized enterprises, there are cases where it is difficult to introduce the equipment due to a heavy burden. Furthermore, when titanium nitride powder or titanium carbonitride powder is applied as an electrode, it is necessary to separately sinter the powder and form it into a predetermined shape or fix it to a substrate. The shape and performance are likely to be limited, and it is inferior in practicality as an electrode material for batteries, electrolyzers, and the like, and its production efficiency is also poor. In the surface treatment method for titanium-based material disclosed in Patent Document 6, an attempt is made to improve the wear resistance of the titanium-based material. However, simply forming a diffusion layer of oxygen or carbon on the titanium surface has a large conductivity. There was a possibility that improvement could not be expected and it could not be put into practical use as an electrode material for batteries, electrolyzers and the like that require electrical conductivity. The method of manufacturing an electron source disclosed in Patent Document 7 aims at an electron source that can be driven at a low voltage used in a field emission display, but does not modify the anodic oxide film itself, and uses a carbon-based material as an anode. Since it is deposited in the pores of the oxide film by the vapor phase carbonization method, it is necessary to perform an etching process in a subsequent process to expose the electron source on the surface, which may involve a large number of processes and may be expensive.

  The present invention has been made in view of the above-described conventional problems, and one object thereof is conductivity that can produce a conductive material excellent in electrical conductivity simply and at low cost with only extremely simple equipment. It is to provide a method for manufacturing a material.

In order to solve the above-described problems, the present invention provides a processing object 10 having a surface having a porous structure of a metal oxide, at least one of carbon powder, iron, nickel, cobalt, iron alloy, nickel alloy, and cobalt alloy. Between 800 ° C. and 1100 ° C. in a nitrogen gas atmosphere (S) in a state of being embedded in a carbon source powder 12 having an average particle size of about several μm to several hundred μm . Heat-treating at a temperature, replacing the metal oxide having a porous structure with a metal nitride, metal carbide, or metal carbonitride to obtain a conductive material that retains the porous structure of the object to be treated. It is comprised from the manufacturing method of the electrically-conductive material to do. The object to be treated is, for example, a metal surface that has been anodized, a metal surface that has been oxidized and made porous, or a metal oxide powder that is entirely porous A structure or the like may be used.

  Further, by mixing a metal oxide powder such as an aluminum oxide powder or a titanium oxide powder with the carbon source powder 12 in which the object to be treated 10 is buried, the heat treatment is performed, so that the surface of the porous metal oxide is made of aluminum. Alternatively, the metal constituting the oxide powder such as titanium may be diffused. For example, it is expected that when the noble metal oxide powder such as iridium oxide is added to the carbon source powder 12, the electric conductivity of the conductive material can be further increased.

  Moreover, it is good also as forming the process target object 10 which the surface consists of a porous structure of a metal oxide by anodizing the metal base material.

  Further, the metal oxide of the object to be processed 10 may be any one of titanium oxide, zirconium oxide, and aluminum oxide.

  According to the method for producing a conductive material of the present invention, the object to be processed having a porous structure with a metal oxide surface is treated with at least one of carbon powder, iron, nickel, cobalt, an iron alloy, a nickel alloy, and a cobalt alloy. And heat treatment in a nitrogen gas atmosphere in a state of being buried in a carbon source powder containing seed powder, and replacing the metal oxide having a porous structure with metal nitride, metal carbide or metal carbonitride Then, since the conductive material is converted into a conductive material that retains the porous structure of the object to be treated, a metal nitride, metal carbide, or metal carbonitride can be obtained in a state in which the porous structure is retained. It has excellent corrosion resistance and can be applied to, for example, electrodes, ozone water generators, electrodes of electrolyzers, semiconductor substrates, and the like. Further, the treatment can be performed without being influenced by the shape, and the conductive material can be manufactured at low cost with simple equipment and simple operation.

  Further, by adopting a configuration in which the heating temperature is set between 800 ° C. and 1100 ° C., heat treatment can be performed at a temperature at which the metal oxide of the object to be treated does not melt, and the original porous structure is maintained and metal nitriding is performed. Product, metal carbide and metal carbonitride.

  Further, by mixing a metal source powder such as an aluminum oxide powder or a titanium oxide powder with a carbon source powder for burying the object to be treated, and by performing the heat treatment, aluminum or titanium is formed on the surface of the porous metal oxide. The electrode performance of the conductive material can be expected to improve by diffusing the metal constituting the oxide powder. Furthermore, it is possible to satisfactorily prevent the carbon source powder from being sintered during the heat treatment.

  In addition, by subjecting the metal base material to an anodized film treatment, a surface of the object to be processed having a porous structure of metal oxide is formed, so a thick oxide film of a micrometer order or more, that is, a porous structure having a large surface area. As a result of easily forming the metal oxide film, a conductive material having high conductivity and excellent electrode performance can be easily produced. Furthermore, the shape of the target conductive material is not easily limited, and the conductive material can be mass-produced and manufactured at low cost.

  In addition, since the metal oxide to be treated is any one of titanium oxide, zirconium oxide, and aluminum oxide, for example, a conductive material that can be used practically as an electrode of a battery, an ozone water generator, an electrolyzer, or a semiconductor substrate. Sex material can be provided.

  Since it is a conductive material having a porous structure of conductive metal nitride, metal carbide or metal carbonitride obtained on the surface, it has high corrosion resistance and at the same time has a porous structure and a surface area. High conductivity can be exhibited because of the large. As a result, it can be used as an electrode that requires high conductivity and corrosion resistance.

It is the schematic of the manufacturing method of the electroconductive material which concerns on embodiment of this invention. It is a SEM (scanning electron microscope) image of the surface of the electroconductive material of Example 1, and the comparative material of Comparative Examples 2 and 3. 2 is an X-ray diffraction pattern of the surfaces of the conductive material of Example 1 and the comparative materials of Comparative Examples 1, 2, and 3. FIG. It is an EPMA (X-ray macroanalyzer) analysis image of Examples 1 and 2. It is a table | surface of the measurement result of the surface electrical resistivity of the electroconductive material of Examples 1-4 and the comparative material of Comparative Examples 1, 2, and 4. FIG. It is a graph of the result of the electrode reaction characteristic test of the surface of Example 1 and Comparative Examples 1 and 5. It is the schematic diagram explaining the growth process of the oxide film by the metal anodic oxide film process.

Embodiments of a method for producing a conductive material of the present invention will be described below with reference to the accompanying drawings. The method for producing a conductive material according to the present invention is a method for improving the conductivity by modifying the surface of a porous structure material. Conductive metal nitrides and metal carbides are maintained while maintaining the porous structure. Or it can convert into metal carbonitride and can obtain the electroconductive material excellent in electroconductivity and corrosion resistance. FIG. 1 shows an embodiment of a method for producing a conductive material of the present invention. In the present embodiment, as shown in FIG. 1, the method for producing a conductive material includes a nitrogen gas in a state in which a processing object 10 whose surface is made of a metal oxide porous structure is buried in a carbon source powder 12. (N ₂ ) Conductive material in which the metal oxide having a porous structure is replaced with a metal nitride, metal carbide or metal carbonitride by heat treatment in an atmosphere to increase the electrical conductivity of the porous structure Get.

  The processing object 10 is made of a metal material whose surface is formed with a porous structure of a metal oxide. In the present embodiment, the object to be treated 10 is specifically made of, for example, a surface of a metal base material of titanium, zirconia, or aluminum that has been subjected to an anodic oxide film treatment with a predetermined thickness. That is, the surface of the object to be processed is almost composed of an insulating metal oxide. Prior to being embedded in a carbon source powder and heat-treated in a nitrogen atmosphere, electricity is allowed to flow in the electrolyte solution using the metal as an anode, so that the pore diameter is several tens of nanometers or more on the metal surface. An anodized film treatment step for forming an anodized film of about several μm is included. Therefore, unlike the surface of a thin oxide film Fa of about several tens of angstroms formed by leaving a metal such as titanium or aluminum Bs in the air (see FIG. 7A), the object to be treated has a surface on the surface of the metal material Bs. It has a porous oxide film Fx (see FIG. 7D) having a porous structure and a large film thickness. As shown in FIG. 7, for example, in the treatment of an anodic oxide film of aluminum, (a) a barrier film Fb0 grows on the surface of aluminum Bs with time, and (b) a film with a thickness of 150 to 250 angstroms. The pore Por is generated. When the film formation further proceeds, (c) dissolution and generation of the film occur simultaneously in the pore portion, the pore Por develops on the aluminum substrate Bs side, and (d) the diameter of the pore Por is about 100 on the upper layer side. A two-layer aluminum oxide film Fx of a porous film Fp of about angstroms and a dense barrier layer Fb on the lower layer side is formed with a predetermined thickness. In FIG. 7, Lv is a reference plane of the original aluminum substrate. In this embodiment, as will be described later, the pore walls of the metal oxide constituting the anodized film are reduced, nitrided, carbonized, or carbonitrided, and the porous walls are retained with the metal nitride, metal, while maintaining the porous structure. Converted to carbide or metal carbonitride. It should be noted that other metals and alloys such as titanium and zirconia may be used as an object to be processed by forming an oxide film having a porous structure by the same anodizing treatment. In the anodic oxide film treatment, for example, a metal oxide having a thick porous structure of 1 to several hundred μm or more can be easily formed on the metal surface. In the anodic film treatment, a fine porous structure having a pore diameter of about several tens of nm to several μm can be easily formed.

  In FIG. 1, the shape of the processing object 10 is formed in a plate shape, for example, but may be a rod shape, a net or lattice shape, or any other shape. Further, the object to be treated 10 is not limited to a metal that has been subjected to an anodic oxide film treatment, and may be any metal that has a metal oxide having a porous structure on at least the surface. For example, a metal oxide powder may be sintered and the entire object including the surface may be made of a metal oxide having a porous structure.

  The carbon source powder 12 functions as a means for nitriding, carbonizing, or carbonitriding after reduction of a porous structure metal oxide that is an object to be treated when heated. Furthermore, the carbon source powder can also function as an oxidation inhibiting means that can exert an oxidation inhibiting action on the surface. The carbon source powder is a carbon source that supplies carbon during the heat treatment. A metal oxide having a porous structure, while carbon source powder (carbon) is present on the surface of the object to be treated and heated, so that carbon reacts with surrounding oxygen to generate carbon monoxide or carbon dioxide. This reduces the oxygen partial pressure around and contributes to reduction of metal oxides and suppression of oxidation. As a result, the carbon source powder functions as a nitriding promotion means for promoting the reaction between the reduced metal oxide surface and nitrogen in a nitrogen gas atmosphere to form a metal nitride or metal carbonitride. Furthermore, the carbon source powder can also be an element for diffusing carbon into the porous structure metal oxide of the object to be processed to form a metal carbide or metal carbonitride. That is, the carbon source powder can be said to be a carbonization promoting means for promoting the reaction between the metal oxide surface to be reduced and carbon to form a metal carbide or metal carbonitride. In the present embodiment, since the carbon source is in the form of powder, the carbon source is sufficiently brought into contact with or close to the surface of the metal oxide in accordance with various shapes and sizes of the object to be treated. The surface reduction, oxidation inhibition, and carbon diffusion are effectively realized. At the same time, in the carbon source powder, a gap is formed between the powder particles, so that the reaction between the metal oxide surface and nitrogen in the atmosphere can be maintained.

  Specific examples of the carbon source powder include a mixed powder containing at least two types of powders, such as carbon powder and iron or iron alloy powder containing iron as a main component. Carbon powder consists of carbon materials which have carbon as a main component, such as activated carbon powder, graphite powder, and charcoal powder, for example. Iron alloys include, for example, carbon steel containing carbon in iron, cast iron with a higher carbon content than carbon steel, other iron-based alloys containing carbon, stainless steel containing chromium, nickel, etc. in addition to iron / carbon Etc. It consists of special steel (alloy steel) containing other arbitrary alloy elements. As for the iron alloy containing carbon, for example, carbon contains 0.01 to 6.7% by weight, preferably about 0.01 to 2% by weight. Instead of iron or iron alloy powder, the same iron group element nickel, cobalt powder, or nickel alloy, cobalt alloy powder, which is an alloy mainly composed of iron group element, is mixed with carbon powder. The carbon source powder may be constituted. Since nickel and cobalt have properties similar to iron, the same effects as described above such as reduction of metal oxide can be expected by mixing with carbon powder. As the carbon source powder, a powder that is difficult to sinter between powders at the time of heating and does not inhibit the reaction between the object to be processed embedded in the powder and nitrogen is suitable. It is preferable that the carbon source powder maintain a powder gap that allows gas or the like (nitrogen, carbon monoxide, carbon dioxide) to pass through even if processing proceeds.

  Suitably, the carbon source powder may be constituted by mixing carbon powder and iron-containing powder containing carbon such as iron powder or carbon steel (hereinafter collectively referred to as steel powder). It has been experimentally found that the treatment effect of the treatment object is higher when carbon powder and steel powder are mixed at a predetermined ratio than when only carbon powder is used as the carbon source powder. The reason for this is not known in detail, but the formation of free carbon is noticeable due to the contact between the carbon powder and iron, and the oxygen partial pressure is reduced by the carbon monoxide and carbon dioxide produced by the reaction with oxygen, and the associated treatment. It is considered that the reduction of the object and the diffusion of carbon to the object to be treated are promoted. Furthermore, since iron powder alone is easy to sinter during heating, mixing with carbon powder that is difficult to sinter helps to prevent sintering. That is, it is considered that the mixed powder of the carbon powder and the steel powder can provide a highly reactive carbon source and a sintering preventing function at the same time, and can efficiently achieve reduction and carbon diffusion. Furthermore, since the reactivity is high, the metal oxide reforming process can be effectively realized even at a relatively low temperature as compared with the carbon powder alone. Although the mixing ratio of carbon powder and steel powder may be arbitrary, for example, it is good to mix in the range of 3: 7-7: 3 by volume ratio.

  The average particle diameter of the carbon source powder is set, for example, on the order of several micrometers to several hundreds of micrometers. If the particle size of the carbon source powder is extremely small, the powder easily sinters during heating, and the reaction between the porous structure of the object to be treated in the powder and nitrogen is suppressed, and the production of the conductive material is hindered. Therefore, it becomes difficult to take out the object after processing. On the other hand, when the particle size of the carbon source powder is too large, functions such as reduction, oxidation inhibition, carbonization, and nitriding on the surface of the object to be processed are reduced, and processing efficiency is lowered. In addition, when mixing 2 or more types of powder like the mixed powder of carbon powder and steel powder, it is good to arrange a particle size.

  Furthermore, in this embodiment, the carbon source powder is mixed with aluminum oxide (alumina) powder. The aluminum oxide powder functions as a sintering inhibitor for the carbon source powder. When processing is performed using a carbon source powder in which only carbon powder and steel powder are mixed, the powder may be slightly sintered, and the surface may be damaged when the processed object is taken out. By adding the aluminum oxide powder to the carbon source powder, it becomes easy to take out after the treatment, and the quality as the conductive material can be maintained. At the same time, the aluminum oxide mixed with the carbon source powder is converted into aluminum by the reducing action caused by the carbon powder and the steel powder, and is reduced and diffused to the surface of the porous structure of the object to be treated. Thereby, the oxide of the element to be added to the surface portion of the object to be treated is mixed with the carbon source powder in advance, so that both prevention of sintering and improvement of conductivity can be achieved. The amount of aluminum oxide powder is set, for example, at a volume ratio of about several tens of percent of the total volume of carbon powder and steel powder. For example, in the examples described later, the carbon source powder has a composition in which carbon powder: steel powder: aluminum oxide powder is mixed at a volume ratio of 4: 6: 3. Thereby, in the porous structure of the conductive material finally obtained, in addition to the formation of metal nitride, metal carbide or metal carbonitride, diffusion of aluminum can be caused, and the electrode of the conductive material As a result, improvement in performance can be expected. As the carbon source powder, in addition to the aluminum oxide powder, for example, a titanium oxide powder, an iridium oxide powder, or the like, a metal oxide powder that is desired to be diffused into the object to be treated after reduction also serves to prevent sintering. May be mixed. Further, the metal oxide powder mixed with the carbon source powder may be, for example, a metal oxide powder different from the porous structure metal oxide of the object to be processed, or the same metal oxide powder. Only one kind of metal oxide powder or a plurality of kinds of metal oxide powders may be mixed.

  As shown in FIG. 1, the carbon source powder 12 is set in such an amount as to completely cover and bury the entire processing object 10, for example. For example, the carbon source powder 12 is filled in a heat-resistant container 14 having a large volume so that the processing object 10 can be completely accommodated. In FIG. 1, the container 14 is closed with, for example, a lid 15, but nitrogen gas can enter the container 14 even when the container 14 is closed. The lid 15 is for preventing the carbon source powder 12 from being scattered or sucked into the vacuum pump when the inside of the closed space S in which the container 14 is disposed is evacuated by a vacuum pump. The lid 15 is made of, for example, a heat-resistant porcelain, but may be formed of paper or the like that burns away during heating and opens the container. The lid 15 is not always necessary. For example, the carbon source powder 12 is disposed so as to be in direct contact with the entire surface of the processing object 10 and is set so as to cover the surface of the processing object with a certain thickness. In addition, for example, the processing object 10 may be disposed so as to contact the bottom surface of the container 14, and the carbon source powder may be filled and buried from above. In addition, the carbon source powder 12 is not limited to a mode in which the entire processing target 10 is buried. For example, when only a part of the processing target 10 is to be surface-treated, only a part of the carbon source powder 12 may be buried. In addition, the carbon source powder is not limited to being filled in the container, and may be piled up and processed on a flat plate or the like so as to bury the processing object 10.

As shown in FIG. 1, the nitrogen gas atmosphere is formed by filling the closed space S with nitrogen gas N ₂ . The nitrogen gas atmosphere is nitrogen supply source means for supplying a nitrogen source for forming a metal nitride or a metal carbonitride instead of a metal oxide having a porous structure as an object to be processed. In FIG. 1, the closed space S is constituted by, for example, a furnace space of the heating furnace 16, that is, a heat treatment chamber 17. The processing chamber 17 is provided with an opening / closing door (not shown), for example, and a processing object can be taken in and out. In the present embodiment, the nitrogen gas atmosphere is generated by flowing the nitrogen gas N ₂ from the gas cylinder 18 through the supply pipe into the closed space S at a predetermined flow rate from one end side, and connecting the exhaust pipe from the other end side of the closed space S. It is held while flowing through. Note that the nitrogen gas atmosphere may be held in the closed space S without flowing nitrogen gas from the exhaust pipe. When the nitrogen gas atmosphere is formed in the closed space S, for example, the air in the closed space S is first removed by the vacuum pump 20 and then nitrogen gas N ₂ is introduced into the closed space S from the gas cylinder 18. A nitrogen gas atmosphere with a high nitrogen concentration is formed. In FIG. 1, valves 22, 23, and 24 are installed in the nitrogen supply pipe, the exhaust pipe, and the connection pipe between the vacuum pump 20 and the supply pipe, respectively. The valves 22, 23, and 24 are appropriately opened and closed to switch between evacuation of the closed space S by the vacuum pump 20 and supply and exhaust of nitrogen in the closed space S.

  As the heating means, a heating furnace 16 having a closed space S in the furnace is used. In the heating furnace 16, for example, a heating element 19 is disposed around the heat treatment chamber 17, and the inside of the treatment chamber 17 can be stably maintained at a high temperature for a long time. The heating temperature is set, for example, between 500 ° C. and less than the temperature at which the metal oxide melts, preferably between 800 ° C. and 1100 ° C. When the heating temperature is too low, the reduction of the metal oxide of the object to be treated by the carbon source powder and the nitriding, carbonizing or carbonitriding reaction hardly occur. On the other hand, if the heating temperature is too high, the carbon source powder is melted, and the porous structure of the object to be processed may be destroyed to reduce the surface area. The heating time is arbitrary, and the longer the heating time, the more the reduction of the metal oxide to be treated and the formation of metal nitride, metal carbide or metal carbonitride are promoted. For example, as shown in Example 1 and FIG. 2 described later, when the heating temperature is 1000 ° C. and the heating time is set to 1 hour, the reduction of the metal oxide and the diffusion of nitrogen, carbon, and aluminum can be sufficiently performed. A conductive material having a porous structure can be obtained.

  As described above, in the method for producing a conductive material according to the present invention, heat treatment is performed in a nitrogen atmosphere in a state in which a treatment target having a porous structure of metal oxide is embedded in a carbon source powder. In this way, while reducing the metal oxide having a porous structure by acting carbon derived from the carbon source powder, the metal nitride is reacted with nitrogen or carbon to maintain the porous structure while maintaining the porous structure, Promotes the formation of metal carbides or metal carbonitrides. As a result, a conductive material having a large surface area and excellent electrical conductivity can be obtained. For example, when the object to be treated 10 is titanium or zirconium having an anodic oxide film formed on the surface, the porous structure in which the titanium oxide or zirconium oxide of the oxide film is converted into titanium carbonitride, zirconium carbonitride, or the like by the above treatment. The surface can be modified from an insulating metal oxide to a highly conductive one. In this way, without using a special device, it is possible to produce a conductive material that is excellent in electrical conductivity at a low cost and with a simple operation using only an extremely simple facility or device such as an anodizing device or a heating furnace. Can be manufactured. Conductive materials can be used for electrodes, semiconductor substrates, etc. in highly corrosive solutions such as batteries, ozone water generators, electrolyzers, etc., and at the same time convert metal oxides into carbonitrides. Therefore, during use as an electrode or the like, corrosion deterioration and other reaction changes on the surface of the material itself that lower the electrode performance are unlikely to occur, and the life can be extended.

  Next, specific examples of the method for producing a conductive material and the conductive material of the present invention will be described.

<Embodiment 1> The thickness of the coating on the surface is obtained by immersing the plate-shaped piece of titanium with a vertical and horizontal size of 10 mm × 10 mm and a thickness of 1 mm as an anode in an electrolyte solution and applying electricity to treat the anode. A processing object 10 having an anodic oxide film having a thickness of about 10 μm and a pore diameter of about several μm was obtained. As the carbon source powder 12, a mixed powder obtained by mixing graphite powder, carbon steel powder (containing about 0.8% by weight of carbon) and aluminum oxide powder in a volume ratio of 6: 4: 3 was used. . As shown in FIG. 1, the carbon source powder 12 is filled in the container 14, and the processing object 10 made of a titanium plate material in which the anodized film is formed in the carbon source powder 12 is completely buried, and the heating furnace 16 Arranged in the processing chamber 17. Then, after the lid 15 is attached to the container 14 and the carbon source powder is not scattered in the space, the inside of the processing chamber 17 is depressurized by the vacuum pump 20 and then nitrogen gas (purity 4N (99.99% or more)) Into the processing chamber 17. The closed space S is made a nitrogen gas atmosphere by evacuating the processing chamber 17 and inflowing nitrogen gas several times. While flowing the nitrogen gas N ₂ from one end side of the processing chamber, while maintaining the nitrogen gas atmosphere while the outflow of nitrogen gas N ₂ is from the other end, and heating the heating furnace 16 to 1000 ° C., 1 hour Then, the heating furnace was naturally cooled, and the treated conductive material EX1 was taken out. The obtained conductive material EX1 was subjected to surface SEM (scanning electron microscope) observation, EPMA (X-ray microanalyzer) analysis, X-ray diffraction, surface electrical resistivity measurement, and electrode reaction characteristic test (FIG. 2, FIG. 3, FIG. 4, FIG. 5, and FIG. In addition, a corrosion resistance test was performed by immersing the conductive material obtained after the treatment in an aqueous solution containing hydrofluoric acid.

  <Example 2> Processing was performed under the same conditions as in Example 1 except that the heating temperature was set to 800 ° C. The conductive material EX2 obtained after the treatment was subjected to EPMA analysis and surface electrical resistivity measurement (see FIGS. 4 and 5).

  <Example 3> Processing was performed under the same conditions as in Example 1 except that the heating temperature was set to 900 ° C. For the conductive material EX3 obtained after the treatment, the surface electrical resistivity was measured (see FIG. 5).

  <Example 4> Processing was performed under the same conditions as in Example 1 except that the heating temperature was set to 1100 ° C. The surface electrical resistivity was measured for the conductive material EX4 obtained after the treatment (see FIG. 5).

  <Comparative example 1> About the comparative material TE1 which is untreated titanium at the time of purchase, the surface X-ray diffraction, the measurement of surface electrical resistivity, and the electrode reaction characteristic test were done (refer FIG.3, FIG.4, FIG.6). .

  <Comparative Example 2> A comparative material TE2 which is titanium having an anodized film of about 10 μm formed on the surface by immersing titanium in the electrolyte solution as an anode and applying electricity to treat the anodized film. X-ray diffraction and surface electrical resistivity were measured (FIGS. 2, 3, and 5).

  <Comparative Example 3> Treated under the same conditions as in Example 1 except that a treatment object obtained by treating titanium with an anodized film was not embedded in the carbon source powder and heat-treated in a nitrogen atmosphere. The obtained comparative material TE3 was subjected to SEM observation and surface X-ray diffraction (see FIGS. 2 and 3).

  <Comparative Example 4> Surface electrical resistivity was measured for platinum TE4 (see FIG. 5).

  <Comparative Example 5> Treatment was performed under the same conditions as in Example 1 except that ordinary titanium on which an anodized film was not formed was buried in a carbon source powder and heat-treated in a nitrogen atmosphere. An electrode reaction characteristic test was performed on the comparative material TE5 obtained after the treatment (see FIG. 6).

  As shown in the SEM image of FIG. 2, the porous structure is also retained in the conductive material EX1 of Example 1 as compared with the comparative material TE2 of Comparative Example 2. Furthermore, in the conductive material EX1, it can be seen that the contrast of the pore wall portion of the porous structure is different, and a plurality of reaction phases that are considered to be titanium nitride, titanium carbide, or titanium carbonitride are formed. Note that, in the comparative material TE3 of Comparative Example 3, the porous structure was maintained, but no reaction phase that was considered to be titanium nitride was observed.

  As shown in FIG. 3, in the X-ray diffraction, for the conductive material EX1 of Example 1, the diffraction angle corresponding to titanium carbonitride Ti (C, N) (the angle 2θ formed by the X-ray incident direction and the reflection direction) ), A strong diffraction intensity peak was observed, confirming the formation of titanium carbonitride Ti (C, N). On the other hand, in the comparative material TE3 of Comparative Example 3, a strong diffraction intensity peak is observed at a diffraction angle corresponding to titanium oxide TiO2 (angle 2θ formed by the incident direction of X-rays and the reflection direction). And almost the same result. Therefore, from the results of FIG. 2 and FIG. 3, in the conductive material EX1, the metal oxide (titanium oxide) on the surface of the object to be processed retained the porous structure by being buried in the carbon source powder and processed. It can be confirmed that it can be replaced with metal carbonitride (titanium carbonitride) in the state.

  In the EPMA analysis, each element of oxygen, nitrogen, carbon, and aluminum was analyzed. As shown in FIG. 4, it can be seen that nitrogen and carbon are present on the surfaces of the conductive material EX1 of Example 1 and the conductive material EX2 of Example 2. In addition, aluminum is also present in the conductive materials EX1, EX2, and the aluminum oxide in the powder is reduced by the carbon powder and the carbon steel powder in the carbon source powder, and the aluminum is diffused in the porous structure. It can also be confirmed. Comparing the conductive material EX1 and the conductive material EX2, it can be seen that the conductive material EX1 has less oxygen distribution and more nitrogen, carbon, and aluminum. Thereby, the one where the temperature of heat processing is higher accelerates | stimulates the reduction | restoration of the metal oxide (titanium oxide) of the porous structure of a process target object, formation of metal carbonitride (titanium carbonitride), and the spreading | diffusion of aluminum. It can be said that it is possible.

  As shown in FIG. 5, in the table of the measurement results of the surface electrical resistivity, the conductive materials EX1 to EX4 of Examples 1 to 4 have a significantly smaller surface electrical resistivity than the comparative material TE2 of Comparative Example 2. It is about the same as titanium TE1 and platinum TE4. Note that the surface electrical resistivity in the table of FIG. 5 is a numerical value measured with a limiter voltage of 90V. Thereby, it can confirm that the electroconductive material obtained with the manufacturing method of this invention has high electrical conductivity.

  In the electrode reaction characteristic test, an electron transfer reaction between hexacyanoiron (III) ions and hexacyanoiron (II) ions that generate a reaction at a relatively low potential was used. A solution prepared by adding 1 mol / l (100 times concentration) sodium hydroxide to a solution prepared by adjusting potassium hexacyanoferrate (III) and potassium hexacyanoferrate (II) to a concentration of 0.01 mol / l prepare. In this solution, a nickel plate is used as an anode as an electrode, and a conductive material EX1 of Example 1 and comparative materials TE1 and TE5 of Comparative Example 1 and Comparative Example 5 are set as a cathode, respectively, and a voltage is applied and flows at that time. The current value was measured. The voltage was measured while changing by 0.1 V from 1.6 to 2.0 V. The result is the graph of FIG. As shown in FIG. 6, it can be seen that the conductive material EX1 having a porous surface has a larger current flowing at the same voltage than those of the comparative materials TE1 and TE5 having no porous structure. . In the comparative material TE5, a titanium carbonitride layer is formed on the titanium surface, but since it is not a porous structure, the surface area becomes relatively small and the electrode performance is inferior. Thereby, it turns out that the electroconductive material excellent in electrode performance was able to be obtained in the present Example.

  Further, the conductive material EX1 of Example 1 was immersed in an aqueous solution containing highly corrosive hydrofluoric acid to conduct a corrosion resistance test. It was confirmed that the conductive material EX1 hardly deteriorates even in an aqueous solution containing hydrofluoric acid and exhibits excellent corrosion resistance. Thereby, the conductive material can be used for a long time even in an electrolytic solution having high corrosiveness, and can be practically used as an electrode of a battery, an ozone water generator, or an electrolyzer.

  The manufacturing method of the conductive material of the present invention described above is not limited to the configurations of the above-described embodiments and examples, and any method is possible without departing from the essence of the present invention described in the claims. Modifications may be made.

  The method for producing a conductive material of the present invention can be applied to a material requiring high conductivity such as an electrode or a semiconductor substrate.

10 Processing object 12 Carbon source powder 16 Heating furnace 17 Processing chamber 18 Gas cylinder S Closed space (nitrogen gas atmosphere)

Claims (4)

The average particle size of the object to be processed having a porous structure of metal oxide on the surface, including carbon powder and at least one powder of iron, nickel, cobalt, iron alloy, nickel alloy, and cobalt alloy is several μm. In a state of being embedded in a carbon source powder having a micrometer order of about several hundred μm , heat treatment is performed at a temperature between 800 ° C. and 1100 ° C. in a nitrogen gas atmosphere. A method for producing a conductive material, comprising replacing a metal nitride, metal carbide or metal carbonitride to obtain a conductive material having a porous structure of the object to be treated. By mixing the metal source powder such as aluminum oxide powder and titanium oxide powder with the carbon source powder for burying the object to be treated, and by performing the heat treatment, the surface of the porous metal oxide such as aluminum or titanium is mixed. method for producing a conductive material according to claim 1, wherein the diffusing metal of the oxide powder. The method for producing a conductive material according to claim 1 or 2 , wherein the metal base material is subjected to an anodic oxide film treatment to form an object to be treated having a porous structure of metal oxide on the surface. The method for producing a conductive material according to any one of claims 1 to 3 , wherein the metal oxide to be treated is any one of titanium oxide, zirconium oxide, and aluminum oxide.