JP7565533B2 - Method for producing a composite having a metal film formed on a substrate and the composite - Google Patents

Description

The present invention relates to a method for easily forming a metal film having excellent peel resistance on a substrate, and a composite in which a metal film having excellent peel resistance is formed on a substrate.

The technology of forming a metal film on a substrate has been used in a variety of technical fields. For example, a circuit board is manufactured by attaching copper foil to a substrate with an adhesive and then etching the copper foil to form a circuit. However, if the adhesive has low affinity with the substrate or copper foil, there is a risk that the metal film will peel off when using an adhesive.

Sputtering is a technique for forming a metal film on a substrate without using adhesives. Sputtering involves introducing an inert gas such as Ar gas into a vacuum, applying a negative voltage to a target made of the film-forming material to generate a glow discharge, ionizing the inert gas atoms, which collide with the surface of the target at high speed to violently eject particles of the film-forming material that make up the target, which then adhere to the surface of the substrate to form a metal film. However, sputtering is expensive to implement, and must be performed in a vacuum, making it difficult to apply to large structures or to perform in situ.

For example, the surface of concrete used in port facilities and offshore airport facilities is coated with a titanium film to protect it from corrosion by seawater, and an anticorrosive current is supplied to the reinforcing steel bars inside (Patent Document 1, etc.). However, it is practically impossible to coat the surface of the huge concrete that makes up the facility with metal by sputtering. Therefore, to coat concrete building materials with metal, a thermal spraying method is generally used (Patent Document 2, etc.).

In addition, sewage may contain Thiobacillus bacteria that oxidize hydrogen sulfide, sulfur, and thiosulfate ions to produce sulfuric acid, which can cause corrosion of concrete sewer pipes and the like. For this reason, a corrosion-resistant Hume pipe containing an inorganic powder carrying antibacterial metal ions has been proposed (Patent Document 3). However, simply mixing antibacterial metal ions into the raw cement may not fully exert the antibacterial properties, and increasing the proportion of antibacterial metal ions may result in a decrease in strength. Therefore, it is desirable to coat the surfaces of sewer pipes and the like with antibacterial metal.

Japanese Patent Application Publication No. 4-314880 Japanese Unexamined Patent Publication No. 1-119576 Japanese Patent Application Publication No. 9-60768

As mentioned above, the thermal spraying method is generally used to coat concrete building materials with metal. However, concrete building materials are porous, and the sprayed metal does not easily penetrate into the pores. Therefore, it must be said that the peel resistance of the metal film formed by the thermal spraying method is low for concrete building materials.
Therefore, an object of the present invention is to provide a method for simply forming a metal film having excellent peeling resistance on a substrate, and a composite produced by the present invention and having a metal film having high peeling resistance on its surface.

The present inventors have conducted extensive research to solve the above problems. As a result, although it was expected that a metal oxide film would be formed by applying a metal chelate complex solution to a substrate and then heat-treating the substrate, they unexpectedly found that the formed film had a metallic luster and that, upon analysis, the film was composed almost entirely of metal, leading to the completion of the present invention.
The present invention will now be described.

[1] A method for producing a composite in which a metal film is formed on a substrate, comprising the steps of:
applying a metal chelate complex solution containing a metal component having a smaller ionization tendency than Cd and a chelating agent to the substrate; and
the step of heat treating the portion of the substrate having the metal chelate complex solution applied thereto.
[2] The method according to the above [1], wherein the metal chelate complex solution further contains a surfactant.
[3] The method according to the above [1] or [2], wherein the substrate is a hardened cement body.
[4] The method according to any one of the above [1] to [3], wherein the metal component is Cu or Ni.
[5] The method according to any one of the above [1] to [4], wherein the chelating agent is an aminocarboxylic acid chelating agent.
[6] The method according to the above [5], wherein the aminocarboxylic acid chelating agent is at least one selected from the group consisting of ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid, and nitrilotriacetic acid.
[7] A substrate and a metal film layer,
The substrate is a hardened cement body,
the ionization tendency of the metal component constituting the metal film layer is smaller than that of Cd;
A composite, characterized in that the metal component is present on the substrate side relative to the interface between the substrate and the metal film layer.

According to the method of the present invention, it is possible to easily form a metal film on the surface of a substrate, and it is possible to treat large substrates such as concrete building materials, and also to perform in situ treatment. In addition, since the method of the present invention uses a metal chelate complex solution instead of molten metal as in the thermal spraying method, it is also possible to fill the pores of a porous substrate with metal, and therefore a metal film with excellent peel resistance can be formed on the surface of a porous substrate. Therefore, the composite of the present invention is extremely useful industrially as a building material with excellent corrosion resistance.

The graph shows the results of XRD analysis of metal films obtained by applying a Cu-chelate complex solution onto each substrate and heating it with a hydrogen flame. 1 is an enlarged photograph of a cross section of a mortar base material having a Cu film formed on the surface thereof, observed with a scanning electron microscope (SEM) and an energy dispersive X-ray analyzer (EDX). This shows the results of XRD analysis of a metal film obtained by applying a Pd-chelate complex solution onto a single crystal Si substrate and heating it with a hydrogen flame. The graph shows the results of XRD analysis of metal films obtained by applying a Cu-chelate complex solution onto each substrate and heating it with an acetylene flame. This shows the results of XRD analysis of a metal film obtained by applying an Al-chelate complex solution onto an aluminum alloy substrate and heating it with a hydrogen flame. This shows the results of XRD analysis of a metal film obtained by applying a Ti-chelate complex solution onto a SUS substrate and heating it with a hydrogen flame. This shows the results of XRD analysis of a metal film obtained by applying an Fe-chelate complex solution onto an aluminum alloy substrate and heating it with a hydrogen flame. This shows the results of XRD analysis of a metal film obtained by applying a Cu-chelate complex solution onto an aluminum alloy substrate and heating it with a gas burner. This shows the results of XRD analysis of a metal film obtained by applying a Cu-chelate complex solution onto an aluminum alloy substrate and heating it with a laser.

The present invention relates to a method for producing a composite in which a metal film is formed on a substrate. The method for producing a composite according to the present invention includes a step of applying a metal chelate complex solution containing a metal component having a smaller ionization tendency than Cd and a chelating agent to a substrate, and a step of heat treating the portion of the substrate to which the metal chelate complex solution is applied. Below, the method of the present invention will be described step by step, but the present invention is not limited to the following specific examples.

1. Coating Step In this step, a metal chelate complex solution containing a metal component having a smaller ionization tendency than Cd and a chelating agent is coated onto a substrate.

Ionization tendency is a relative index that indicates the ease with which an element becomes ions, mainly in an aqueous solution; the smaller the ionization tendency, the larger the standard electrode potential E° value. The E° of Cd is -0.4025 V, and in the present invention, metal components with E° values higher than this are used. Examples of metal components with lower ionization tendency than Cd include, in order of increasing ionization tendency, Co, Ni, Sn, Pb, Sb, Bi, Cu, Hg, Ag, Pd, Ir, Pt, and Au. The E° of Co is -0.277 V.

The metal film formed on the surface of the substrate can be used as an electrode. For example, if a metal film is formed on the surface of a hardened cement body and a voltage is applied, the metal film acts as a corrosion-resistant coating. Furthermore, the metal element can be selected based on its usefulness. For example, Ni and Cu have antibacterial properties, and Cu is more preferable from the standpoint of cost. Only one type of metal element may be used, or two or more types may be used in combination.

The chelating agent is not particularly limited as long as it can form a chelate with the metal component to improve its solubility, and examples of the chelating agent include ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid, ethylenediaminediacetic acid, 1,2-diaminopropanetetraacetic acid, 1,3-diaminopropanetetraacetic acid, hexamethylenediaminetetraacetic acid, 1,2-cyclohexanediaminetetraacetic acid, diaminopropanoltetraacetic acid, hydroxyethylenediaminetriacetic acid, glycol ether diaminetetraacetic acid, ethylenediaminedi(o-hydroxyphenyl)acetic acid, iminodiacetic acid, hydroxyethyliminodiacetic acid, nitrilotriacetic acid, methylglycinediacetic acid, ethylenediamine ... Examples of the chelating agents that can be used include aminocarboxylic acid chelating agents such as propionic acid, nitrilotripropionic acid, ethylenediaminedisuccinic acid, 1,3-diaminopropanedisuccinic acid, glutamic acid-N,N-diacetic acid, and aspartic acid-N,N-diacetic acid; phosphonic acid chelating agents such as hydroxyethylidene diphosphonic acid, nitrilotrismethylenephosphonic acid, ethylenediaminetetramethylenephosphonic acid, diethylenetriaminepentamethylenephosphonic acid, 2-phosphono-1,2,4-butanetricarboxylic acid, phosphonohydroxyacetic acid, and hydroxyethyldimethylenephosphonic acid; and hydroxycarboxylic acid chelating agents such as gluconic acid, citric acid, tartaric acid, and malic acid.

The chelating agent is preferably water-soluble. Only one type of chelating agent may be used, or two or more types may be used in combination. Among these, it is preferable to use an aminocarboxylic acid-based chelating agent, since it is easily thermally decomposed in the subsequent heat treatment process. Preferred aminocarboxylic acid-based chelating agents include ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid, and nitrilotriacetic acid, and ethylenediaminetetraacetic acid is more preferable. These chelating agents are inexpensive and easy to obtain, and the metal chelate complex solutions formed from these chelating agents stably dissolve metal components, making it easy to prepare clear metal chelate complex solutions.

From the viewpoint of cost and ease of handling, the solvent for the metal chelate complex solution is preferably water or a mixed solvent of a water-miscible organic solvent and water. Examples of water-miscible organic solvents include alcohol-based solvents such as methanol, ethanol, and isopropanol. The solvent for the metal chelate complex solution preferably contains at least water, and for example, the concentration of water in the solvent is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more or 95% by mass or more. From the viewpoint of low environmental load, it is particularly preferable to use substantially only water as the solvent, and therefore the metal chelate complex solution is preferably an aqueous metal chelate complex solution.

The content of the metal component in the metal chelate complex solution is preferably adjusted so that it is sufficiently dissolved by the chelating agent. For example, it can be 0.1 mass% or more and 15 mass% or less, and 10 mass% or less is preferable. The content of the chelating agent in the metal chelate complex solution is preferably equal to or more than the theoretical amount of chelate coordination with the metal component, and is preferably 1.0 times or more and 1.5 times or less per mole of the metal ion amount of the metal component. The concentration of the metal chelate complex in the metal chelate complex solution can be, for example, 1 mass% or more and 60 mass% or less, and 10 mass% or more and 40 mass% or less is preferable.

The metal chelate complex solution may contain additives in addition to the metal element and the chelating agent. Examples of additives include, but are not limited to, surfactants and viscosity modifiers.

The surfactant reduces the surface tension of the metal chelate complex solution. For example, if the substrate is porous and the metal chelate complex solution contains a surfactant, the metal chelate complex solution can more easily penetrate into the pores, resulting in the metal being present in the pores and increasing the peel resistance of the metal film layer to the substrate.

As the surfactant, nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants can be used without any particular restriction, but nonionic surfactants are preferred due to their affinity to porous substrates such as hardened cement bodies. There are no particular restrictions on the nonionic surfactant, but examples include acetylene-based surfactants, polyalkylene glycol-type nonionic surfactants, and silicone-based surfactants.

Viscosity adjusters are primarily used to increase the viscosity of the metal chelate complex solution to prevent dripping, and examples of such agents include polysaccharides, polymers such as polyethylene glycol and acrylic polymers, and amides.

The metal chelate complex solution can be prepared by dissolving at least a metal compound containing a metal element and a chelating agent in a solvent. Alternatively, the metal chelate complex solution may be prepared by dissolving a chelate complex of a metal element in a solvent.

Metal compounds containing metal elements can include oxides, hydroxides, halide salts such as chlorides and bromides, carbonates, nitrates, sulfates, phosphates, borates, silicates, etc. Among these, it is preferable to use metal oxides, metal hydroxides, metal carbonates, and metal nitrates. By preparing a metal chelate complex solution using these metal compounds, it is possible to prevent unnecessary elements from being mixed into the metal film formed by the coating process and heat treatment process.

As the chelating agent used in preparing the metal chelate complex solution, the free acid type of the chelating agent described above or its salt can be used. As the salt of the chelating agent, it is preferable to use an ammonium salt or an amine salt. If such a chelating agent is used, the ammonium ion or amine component is easily decomposed during the heat treatment process, and it is possible to prevent unwanted elements from being mixed into the metal film.

When the valence of the chelating agent is not equal to the valence of the metal ion to be chelated, a cation or anion may be added so that the metal chelate complex is electrically neutral. Examples of the cation include ammonium ions and quaternary ammonium cations. Examples of the anion include nitrate ions and halide ions such as chloride ions and bromide ions, but nitrate ions are preferred because they are less likely to remain in the metal film.

The temperature when preparing the metal chelate complex solution is not particularly limited as long as it is above the melting point and below the boiling point of the solvent, but is preferably 20°C or higher, more preferably 35°C or higher, even more preferably 50°C or higher, and preferably 80°C or lower, more preferably 70°C or lower. If the chelating agent or metal chelate complex does not dissolve completely, it is preferable to add ammonia, amine, etc. to completely dissolve them.

When the metal chelate complex is used as a raw material for the metal chelate complex solution, the metal chelate complex is precipitated as a solid from the metal chelate complex solution prepared as described above, and this is used as a raw material for the metal chelate complex solution. The precipitation of the metal chelate complex can be carried out by adding a poor solvent to the metal chelate complex solution, or by heating, concentrating, or cooling the metal chelate complex solution, and further treatments such as filtration, drying, washing, and recrystallization may be carried out as necessary.

The substrate to which the metal chelate complex solution is applied is not particularly limited as long as it has sufficient heat resistance so that it will not be altered or deformed even when heated in the subsequent heat treatment process, and is preferably composed mainly of inorganic materials. From this perspective, hardened cement, minerals, ceramics, and metals are preferably used as substrates. The substrate may be real estate such as a structure, or may be a clay pipe or building material. Examples of substrates for real estate include the walls and ceilings of structures such as tunnels, underground shopping malls, and ports, the walls and ceilings of buildings such as buildings, roads, bridges, and cliffs.

Cement is mainly composed of calcium oxide (CaO), silicon dioxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), and iron (III) oxide (Fe ₂ O ₃ ). Portland cement contains tricalcium silicate (alite, 3CaO·SiO ₂ ), dicalcium silicate (belite, 2CaO·SiO ₂ ), calcium aluminate (aluminate, 3CaO·Al ₂ O ₃ ), calcium aluminoferrite (ferrite, 4CaO·Al ₂ O ₃ ·Fe ₂ O ₃ ), and calcium sulfate (gypsum, CaSO ₃ ·2H ₂ O). Cement hardens by chemical reactions in which calcium oxide becomes calcium hydroxide and other components become hydrates. In addition to Portland cement, there are also blended cements that are made by mixing Portland cement with blast furnace slag, fly ash, or siliceous admixtures. Mortar is made by mixing fine aggregate sand, cement, and water and hardening it, while concrete is a hardened product made by solidifying sand, gravel, water, etc. with cement. As mentioned above, cement hardens through the hydration reaction, and water that is not involved in the reaction evaporates, so general hardened cement bodies are porous.

As described above, hardened cement bodies are hardened by hydration and therefore tend to deteriorate when exposed to water, particularly seawater, and because they contain calcium hydroxide, they also tend to deteriorate when exposed to acid. However, according to the method of the present invention, part or all of the surface of the hardened cement body substrate can be coated with a metal film, thereby increasing the resistance of the hardened cement body.

Minerals include limestone such as marble, silica, and Oya stone. Ceramics include metal oxides such as alumina, zirconia, barium titanate, and silica; metal hydroxides such as hydroxyapatite; metal carbides such as silicon carbide; and metal nitrides such as silicon nitride. Metals constituting the substrate include metals other than those that form metal films. For example, iron; iron alloys such as carbon steel, stainless steel, chromium molybdenum steel, and manganese molybdenum steel; aluminum alloys such as duralumin; and nickel alloys such as Hastelloy and Monel.

The method of applying the metal chelate complex solution to the substrate is not particularly limited, and can be, for example, application using a brush or roller as in the case of painting with paint, or spray application. Depending on the size of the substrate, application by the dipping method or spin coating method is also possible.

The metal chelate complex solution may be applied to the entire surface of the substrate, or to only a portion of the surface. Two or more types of metal chelate complex solutions may be used and applied to different portions of the substrate to enhance the design of the applied portions. Furthermore, depending on the desired thickness of the metal film, it is possible to increase the thickness of the metal chelate complex coating by repeating the application and drying of the metal chelate complex solution multiple times, or by applying a thick layer of a highly viscous metal chelate complex solution.

The drying conditions after applying the metal chelate complex solution to the substrate surface may be adjusted as appropriate, mainly depending on the solvent of the metal complex chelate solution. For example, the substrate may be heated at 40°C or higher and 80°C or lower for 5 minutes or longer and 1 hour or shorter. Alternatively, the substrate may be left at room temperature until the coating film is dry.

2. Heat Treatment Step In this step, the portion of the substrate coated with the metal chelate complex solution is heat treated to form a metal film. More specifically, the portion coated with the metal chelate complex solution is heated to thermally decompose and remove organic components such as chelating agents and surfactants, and a metal film is formed instead of a metal oxide film, probably because the metal components used in the present invention have a relatively low ionization tendency.

The temperature of this step is adjusted within a range in which the organic components are thermally decomposed. For example, it can be 1000°C or higher and 3500°C or lower. The temperature is preferably 1200°C or higher, and more preferably 1300°C or higher. For example, a flame obtained by burning a combustible gas can be used for heating. There is no particular limitation on the combustible gas, and for example, hydrogen, acetylene, propane, butane, etc. can be used. The inventors initially thought that heating with a hydrogen flame, which has reducing properties, was necessary to form a metal film, but according to the method of the present invention, it is possible to form a metal film with an acetylene flame or a butane flame. In addition, the heat treatment time should be appropriately adjusted. For example, if the formation of a metal film is observed, the heat treatment should be stopped to prevent oxidation to a metal oxide. The formation of a metal film can be confirmed by discoloration from metal ions or the appearance of a luster unique to metals.

The heat treatment may be performed using a laser instead of a flame. A laser is a light having directionality (straightness), monochromaticity, and coherence, and by irradiating a target with a laser, the surface temperature of the target can be rapidly increased, making it possible to process the target. In the present invention, the reaction is caused to proceed by irradiating the part coated with the metal chelate complex solution with laser light and adjusting the surface temperature to the above range. The laser to be used may be appropriately selected within a range in which a metal film can be formed, and for example, a YAG laser or a _CO2 laser that is commonly used for laser processing can be used.

The laser irradiation conditions may be adjusted so that a metal film is formed on the area where the metal chelate complex solution is applied. For example, the higher the energy of the irradiated laser, the shorter the heat treatment time can be, but it is not preferable to use a laser with such high energy that it damages the formed metal film. Specifically, it is preferable to use a relatively long wavelength, such as 1.06 μm or 10.6 μm, a relatively low energy laser with a pulse rate of 0.01 msec or more and 1 msec or less, and a pulse rate of 1 pps or more and 100 pps or less. The laser irradiation time may be until the coated surface acquires a metallic luster.

The substrate is preferably placed in the flame or at the end of the flame. The distance from the burner that forms the flame to the substrate may be adjusted, for example, in the range of 30 mm or more and 300 mm or less. In the heat treatment process, the substrate is preferably burned with a flame while the substrate and/or the burner are moved at a relative speed (relative speed to each other) of 10 mm/sec or more and 200 mm/sec or less, which makes it easier to form a metal film on the substrate surface in a suitable manner while preventing damage or deterioration of the substrate. When the substrate and/or the burner are moved in this way, the process of burning the substrate with a flame may be performed only once or may be performed multiple times. In the latter case, for example, it is convenient to burn the substrate with a flame while moving the substrate and/or the burner back and forth. When a laser is used, for example, it is preferable to adjust the distance between the focusing system of the laser processing machine and the coating surface so that the amount of energy and the irradiation area applied to the coating surface are appropriate.

As described above, a composite having a metal film formed on a substrate can be obtained. According to the manufacturing method of the present invention, a metal film can be easily formed on a substrate by applying a metal chelate complex solution to the substrate and applying a flame or laser to heat-treat the substrate. That is, the composite of the present invention includes a substrate and a metal film layer, and at least a part of the substrate is covered with the metal film layer. The metal film thus formed can be formed in a thin film shape, so that the cost of applying and forming the metal can be reduced. The thickness of the metal film is not particularly limited, but can be, for example, 0.5 μm or more and 100 μm or less. According to the manufacturing method of the present invention, a metal film can be easily formed on a substrate in situ, even if the substrate is a civil engineering structure or a building that cannot be easily moved.

As mentioned above, the cement hardened body is generally porous because it is hardened by chemical reactions such as hydration reactions and contains sand and gravel with relatively large particle sizes to improve strength. Examples of cement hardened bodies include hardened cement itself, mortar, which is a hardened mixture of cement and sand, and concrete, which is a hardened mixture containing gravel with relatively large particle sizes. All of these are porous. In contrast, for example, a thermal spraying method using molten metal cannot fill the pores of the cement hardened body with metal, and the formed metal film has poor peeling resistance. However, the method of the present invention uses a liquid metal chelate complex solution, which can penetrate the metal chelate complex solution into the pores, and as a result, a metal film with excellent peeling resistance can be formed. If the metal chelate complex solution contains a surfactant and has reduced surface tension, the solution can penetrate into smaller pores more easily.

Specifically, in the composite of the present invention, in which the substrate is a hardened cement body, the metal component is present closer to the substrate than to the interface between the substrate and the metal film, and therefore the metal film has high resistance to peeling. The interface between the substrate and the metal film refers to, for example, the average line at a reference length of 100 μm when the composite is cut in a direction perpendicular to the planar direction of the metal film and the cross section is observed at a magnification of 1000 times or more and 10,000 times or less using a scanning electron microscope or the like. The average line here refers to a line obtained by replacing the filtered waviness curve for the roughness curve with a straight line using the least squares method (JIS B 0601-1994).

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

Example 1: Formation of Cu Coating (1) Preparation of Metal Chelate Solution Ethylenediaminetetraacetic acid (30.1 g) was placed in a 100 mL beaker, and distilled water was added to make the total amount 80 g. 25% aqueous ammonia (14.0 g) and copper oxide (8.2 g) were then added, and the mixture was heated under reflux and stirred for 5 hours to completely dissolve it. The resulting solution was diluted with distilled water to adjust the concentration of EDTA.Cu.( _NH4 ) ₂ to 40 mass%. A nonionic surfactant (Olfine ^(R) EXP.4300, manufactured by Nissin Chemical Industry Co., Ltd.) was then added to make the concentration 0.1 mass%.

(2) Formation of Cu Coating Film A coating film was formed by repeatedly dropping the above EDTA.Cu.( _NH4 ) ₂ aqueous solution onto the substrate shown in Table 1 and then drying at 65°C for 20 minutes. The blasting treatment was performed using alumina particles ("White Alundum #60" manufactured by Fuji Manufacturing Co., Ltd., particle size: 212-250 μm) as an abrasive.

Using a spray gun ("6P-II" manufactured by Sulzer Metco), hydrogen was supplied at a rate of 32.5 L/min and oxygen at a rate of 43.0 L/min, and the spray gun was moved at a speed of 50 mm/s from a distance of 18 cm, scanning the front surface of the substrate once to heat the coating. As a result, the color of the substrate surface changed from the blue color characteristic of Cu ²⁺ ions to reddish brown.

The obtained coating was analyzed by X-ray diffraction. The results are shown in Figure 1. When the XRD results shown in Figure 1 were compared with the ICDD powder diffraction database, a Cu cubic crystal peak (00-004-0836) was clearly observed, which revealed that a Cu film was formed on all of the substrates.
Moreover, an enlarged photograph of the cross section of the mortar base material on which a Cu film was formed was observed using a scanning electron microscope (SEM) and an energy dispersive X-ray analyzer (EDX) is shown in Fig. 2. As can be seen from the enlarged photograph in Fig. 2, the Cu film is in close contact with the uneven surface of the mortar base material along the unevenness.

Example 2: Formation of Pd coating (1) Preparation of metal chelate solution Distilled water was added to palladium dichloride ethylenediaminetetraacetate to dissolve it, thereby obtaining a 15 mass % EDTA.Pd.Cl2 _aqueous solution.

(2) Formation of Pd coating A total of 0.4 g of the above _EDTA.Pd.Cl2 aqueous solution was dropped onto a 3 cm x 3 cm single crystal Si substrate, followed by drying at 65°C for 20 minutes, to form a coating, which was then heated under the same conditions as in Example 1(2). The results of the XRD analysis of the coating are shown in Figure 3.
When the XRD analysis results shown in FIG. 3 were compared with the ICDD powder diffraction database, the peaks of Pd cubic crystals (00-087-0641 and 00-005-0681) were clearly observed, which revealed that a Pd film was formed on the substrate.

Example 3: Formation of Cu coating A coating was formed on a substrate in the same manner as in Example 1, except that acetylene gas was used instead of hydrogen gas supplied to the spray gun. The results of XRD analysis of the substrate surface are shown in FIG.
As shown in the results in FIG. 4, even when the combustible gas supplied to the spray gun was changed from hydrogen to acetylene gas, a Cu coating could be formed on the substrate.
The inventors had suspected that the reason why a Cu coating rather than a copper oxide coating could be formed on the substrate in Example 1 was due to the reducing action of hydrogen used as the combustible gas, but it was a surprising result that a Cu coating could be formed even when acetylene gas was used.

Example 4: Formation of Ni coating (1) Preparation of metal chelate solution Ethylenediaminetetraacetic acid (22.9 g) was placed in a 100 mL beaker, and distilled water was added to make the total amount 80 g. 25% ammonia water (10.7 g) and nickel (5.9 g) were then added, and the mixture was heated under reflux and stirred for 5 hours to completely dissolve the solution. The resulting solution was diluted with distilled water to adjust the concentration of EDTA.Ni.( _NH4 ) ₂ to 30 mass%.

(2) Formation of Ni coating The above EDTA.Ni.( _NH4 ) ₂ aqueous solution (0.5 g) was sprayed onto an aluminum alloy (A5052) substrate measuring 50 mm x 50 mm x 10 mm, followed by drying at 65°C for 20 minutes. This operation was repeated four times to form a coating film.
The coating was then heated in the same manner as in Example 1(2), except that the distance between the spray gun and the substrate was 130 mm or 180 mm and the number of scans was 3. The results of the XRD analysis of the coating are shown in FIG.
When the XRD analysis results shown in Figure 5 were compared with the ICDD powder diffraction database, no peaks corresponding to Ni crystals were observed. However, when the powder obtained by peeling off the coating was analyzed by XRD, a peak (00-004-0850) corresponding to Ni cubic crystals was observed. The reason why no peaks corresponding to Ni crystals were observed in the coating is thought to be that the substrate was slightly tilted during XRD measurement, causing the peak to shift overall.
Furthermore, the XRD analysis showed peaks (01-089-7130 and 01-073-1519) corresponding to NiO cubic crystals, but since the intensity was smaller than that of the Ni cubic crystal peaks, it was believed that these were derived from the passive film.

Comparative Example 1
A coating film was formed by dropping a 30% by mass _EDTA.Ti.NH4 aqueous solution onto a blast-treated SUS substrate and drying it in air at 65°C for 20 minutes twice. The total amount of the 30% by mass _EDTA.Ti.NH4 aqueous solution used was about 1 g.
Using a spray gun ("6P-II" manufactured by Sulzer Metco), hydrogen was supplied at a rate of 32.5 L/min and oxygen at a rate of 43.0 L/min, and the spray gun was moved at a speed of 50 mm/s from a distance of 18 cm or 13 cm to scan the front surface of the substrate twice to heat the coating. The results of the XRD analysis of the coating are shown in Figure 6.
As shown in Figure 6, the XRD analysis results showed that in addition to Fe (ICDD: 01-071-4649) and _FeOx derived from the SUS substrate, the only peaks observed were those of rutile-type _TiO2 (ICDD: 01-077-0442), and no Ti peaks (ICDD: 00-044-1294) were observed. Since Ti has a relatively high ionization tendency, it is believed that even titanium oxide was oxidized by the heat treatment.

Comparative Example 2
A blast-treated aluminum alloy (A5052) substrate measuring 5 cm x 5 cm x 1 cm was preheated at 100° C. using an electric furnace, and then a process of spray-coating a 30 mass % Fe-EDTA aqueous solution and drying at 65° C. or 100° C. was repeated three times. The number of times of spray coating was 6, 4, and 2, respectively.
Using a spray gun ("6P-II" manufactured by Sulzer Metco), hydrogen was supplied at a flow rate of 32.5 L/min and oxygen at a flow rate of 43.0 L/min, and the spray gun was moved at a speed of 50 mm/s from a distance of 18 cm or 13 cm, scanning the front surface of the substrate once vertically and once horizontally to heat the coating. When the coating was analyzed by XRD, it was found that the aluminum alloy substrate and αFe (ICDD: 03-065-4899) overlapped, and the presence or absence of a peak for Fe could not be identified, so the coating was peeled off and the obtained powder was subjected to XRD analysis. The results are shown in FIG. 7.
As shown in Fig. 7, although a slight peak of αFe (ICDD: 03-065-4899) was observed, the high intensity peaks were those of _{Fe3O4 cubic} crystals (ICDD: 01-086-1352), _Fe2O3 triclinic crystals (ICDD: 01-072-0469), and FeO _cubic crystals (ICDD: 01-089-0686). Thus, even though it was Fe, the obtained coating was mainly composed of iron oxide, and it was not possible to form an Fe film.

Example 5: Formation of Cu Coating - Use of Gas Burner (1) Preparation of Metal Chelate Solution Ethylenediaminetetraacetic acid (30.1 g) was placed in a 100 mL beaker, and distilled water was added to make the total amount 80 g. 25% ammonia water (14.0 g) and copper oxide (8.2 g) were then added, and the mixture was heated under reflux and stirred for 5 hours to completely dissolve it. The resulting solution was diluted with distilled water to adjust the concentration of EDTA.Cu.( _NH4 ) ₂ to 40 mass%. A nonionic surfactant (Olfine ^(R) EXP.4300, manufactured by Nissin Chemical Industry Co., Ltd.) was then added to make the concentration 0.1 mass%.

(2) Formation of Cu Coating A coating was formed by dropping 0.5 g of the above EDTA.Cu.( _NH4 ) ₂ aqueous solution onto a polycrystalline alumina substrate (50 mm x 50 mm x 1 mm) and drying at 65°C for 20 minutes. Using a commercially available gas burner ("Cassette Gas Torch Burner" manufactured by Iwatani Corporation, fuel: butane gas, flame temperature: 1,300°C), the flame was manually scanned up, down, left and right on the coating for 1 minute and 30 seconds. As a result, the color of the substrate surface changed from the blue color characteristic of Cu2 ⁺ ions to reddish brown.
The resulting coating was analyzed by X-ray diffraction. The results are shown in Figure 8. When the XRD results shown in Figure 8 were collated with the ICDD powder diffraction database, a Cu cubic crystal peak (00-004-0836) was clearly observed, making it clear that a Cu film had been formed on all of the substrates. In addition, peaks for the oxides CuO (00-048-1548) and Cu ₂ O (00-005-0667) were also clearly observed, suggesting that a portion of the generated copper had been oxidized.

Example 6: Formation of Cu Coating - Use of Laser (1) Preparation of Metal Chelate Solution Ethylenediaminetetraacetic acid (30.1 g) was placed in a 100 mL beaker, and distilled water was added to make the total amount 80 g. 25% aqueous ammonia (14.0 g) and copper oxide (8.2 g) were then added, and the mixture was heated under reflux and stirred for 5 hours to completely dissolve it. The resulting solution was diluted with distilled water to adjust the concentration of EDTA.Cu.( _NH4 ) ₂ to 40% by mass. A nonionic surfactant (Olfine ^(R) EXP.4300, manufactured by Nissin Chemical Industry Co., Ltd.) was then added to make the concentration 0.1% by mass.

(2) Formation of Cu Coating The above EDTA.Cu.( _NH4 ) ₂ aqueous solution was dropped on a polycrystalline alumina substrate (2.5cm x 5.0cm x 0.25cm) in an amount of 0.25g, and then dried at 65°C for 20 minutes to form a coating. Using a pen-type YAG laser processing machine ("PSL-P30 laser processing machine" manufactured by Nippon Welding Co., Ltd., oscillation wavelength: 1.06μm), the laser was manually scanned linearly up, down, left and right on the coating for 10 minutes under the conditions of pulse width: 0.3msec, pulse number per second: 20pps. As a result, the color of the substrate surface changed from the blue color specific to Cu2 ⁺ ions to reddish brown.
The obtained coating was analyzed by X-ray diffraction. The results are shown in Figure 9. When the XRD results shown in Figure 9 were compared with the ICDD powder diffraction database, a Cu cubic crystal peak (00-004-0836) was clearly observed, which revealed that a Cu film was formed on the substrate.

The method of the present invention makes it possible to easily produce metal-coated composites with excellent corrosion resistance and antibacterial properties that can be used for concrete building materials in tunnels, underground shopping malls, ports, and other places where deterioration due to moisture and seawater is a concern, and for sewer pipes where deterioration due to moisture as well as acids produced by microorganisms is a concern.

Claims (7)

A method for producing a composite having a Cu film formed on a surface of a hardened cement body, comprising the steps of:
applying an aqueous solution of a metal chelate complex containing Cu, an aminocarboxylic acid chelating agent, and a surfactant to the hardened cement body ; and
The method comprises a step of heat treating the portion of the surface of the hardened cement body on which the aqueous solution of the metal chelate complex is applied. The method according to claim 1, wherein the aminocarboxylic acid chelating agent is at least one selected from ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid, and nitrilotriacetic acid. The method according to claim 1 or 2, wherein the Cu content in the aqueous metal chelate complex solution is 0.1% by mass or more and 15% by mass or less. The method according to any one of claims 1 to 3, wherein the aqueous metal chelate complex solution further contains a viscosity modifier. The method according to any one of claims 1 to 4, wherein the hardened cement body is concrete. The method according to any one of claims 1 to 5, wherein the metal chelate complex aqueous solution on the surface of the hardened cement body is heat-treated at 1000°C or more and 3500°C or less. A composite including a substrate and a Cu layer,
The substrate is a concrete building material ,
A metal component of the Cu layer is present on the substrate side relative to an interface between the substrate and the Cu layer,
The interface is a composite that is cut in a direction perpendicular to the planar direction of the Cu layer , and the cross section is observed at a magnification of 1,000 times or more and 10,000 times or less using a scanning electron microscope , and the interface is an average line obtained by replacing a filtered waviness curve for a roughness curve with a straight line by the least squares method in accordance with JIS B 0601-1994 over a reference length of 100 μm.

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