Method for forming film made of groups of nano-particles of metal or metal oxide having catalyst action on both surfaces of substrate

Abstract

To provide a method for forming a film made of groups of metal nano-particles in which a surface of a fine particle exhibiting a catalytic action is directly exposed to an ambient, adjacent fine particles join together and a surface of the group of fine particles exhibits a catalytic action, the group of the fine particles is laminated with less than 10 of fine particles overlapping one another, the film usable over a long term and exhibiting the catalytic action is formed on both surfaces of the film.SOLUTION: Groups of nano-particles of a metal having a catalytic action fill uneven portions of both surfaces of a substrate and cover both surfaces of the substrate, and furthermore, some of the groups of the nano-particles of the metal that fills the uneven portions on both surfaces of the substrate are in contact with the groups of some metal nano-particles covering both surfaces of the substrate, and the contacted nano-particles are metallic bonded at the contact site. Thereby, the groups of metal-bonded metal nano-particles is bonded to both surfaces of the substrate as a thin film having a thickness thinner than 0.1 μm, and a film having catalytic action is formed on both surfaces of the substrate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for forming a film consisting of a collection of nanoparticles of catalytic metal or metal oxide on both surfaces of a substrate to a thickness of less than 0.1 μm. Note that, since a thin film with a thickness of 250 μm or less is called a film in JIS packaging terms, in this invention, a catalytic film with a thickness of less than 0.1 μm is also referred to as a film. Specifically, crystals of a metal compound, which precipitates through the thermal decomposition of a catalytic metal or metal oxide, are crushed to a size of around 20 nm, and a collection of these microcrystals is dispersed in a liquid organic compound with a viscosity of less than 1 mPa·sec at 20°C to create a suspension. A substrate is then immersed in the suspension. Because the microcrystals are two orders of magnitude smaller than the width of the irregularities on the substrate's surface and have almost no mass, the suspension dispersed in the low-viscosity organic compound penetrates into the irregularities on the substrate's surface and adheres to both surfaces of the substrate and to the irregularities on both surfaces. Then, when the metal compound is thermally decomposed to precipitate a metal, the fine crystals of the metal compound are thermally decomposed, and a collection of granular nanoparticles of catalytic metal having a size of about 10 nm is simultaneously precipitated on both surfaces of the substrate and the irregularities on both surfaces, and the nanoparticle collections are laminated. At this time, since the metal nanoparticles are free of impurities and in an active state, the nanoparticles are metallically bonded at the contact points, and the metallically bonded collections of metal nanoparticles fill the irregularities on both surfaces of the substrate and also fill both surfaces of the substrate. Furthermore, some of the metal nanoparticle collections that fill the irregularities on both surfaces of the substrate come into contact with some of the metal nanoparticle collections that fill both surfaces of the substrate and are metallically bonded at the contact points. As a result, a film consisting of the metallically bonded collections of metal nanoparticles is bonded to both surfaces of the substrate with a thickness less than 0.1 μm, and a film consisting of the catalytic metal nanoparticle collection is formed on both surfaces of the substrate. On the other hand, when a metal compound precipitates a metal oxide by thermal decomposition, a flat substrate is used as the substrate, the substrate is immersed in the suspension, and after removal, the substrate is sandwiched between two flat plates, the entire surface of the upper flat plate is evenly compressed, and the temperature is raised to the thermal decomposition temperature of the metal compound to thermally decompose the fine crystals of the metal compound. During this process, clusters of catalytic metal oxide nanoparticles, ranging in size from about 10 nm to granular, are simultaneously precipitated on both surfaces of the plate-like substrate and on the irregularities on both surfaces. Furthermore, compressive stress is applied to the clusters of metal oxide nanoparticles, causing adjacent clusters of metal oxide nanoparticles to be friction-welded together, the clusters of joined metal oxide nanoparticles filling the irregularities on both surfaces of the substrate and filling both surfaces of the substrate, and further, some clusters of metal oxide nanoparticles that have filled the irregularities on both surfaces of the substrate come into contact with some clusters of metal oxide nanoparticles that have filled both surfaces of the substrate, and the metal oxide nanoparticles are friction-welded together at the contact sites. As a result, a film made of clusters of metal oxide nanoparticles joined by friction welding is bonded to both surfaces of the substrate with a thickness of less than 0.1 μm, and a film made of clusters of catalytic metal oxide nanoparticles is formed on both surfaces of the substrate. The film has granular nanoparticles with a large specific surface area on the surface of the film. of The surface is made up of granular nanoparticles of similar size joined together by metallic bonding or friction welding at the contact points, meaning that more than 50% of the nanoparticle surface is directly exposed to the outside world. As a result, the collection of nanoparticles that form the film's surface efficiently exerts the inherent catalytic activity based on the material that makes up the nanoparticles. Furthermore, by bonding a film made up of a collection of nanoparticles to the surface of a substrate made of a material that suits the environment to which the catalytic film will be exposed, the catalytic film can be used for long periods of time in a variety of environments. [Background technology]

[0002] One method for forming a catalytic coating on a substrate is to use a catalytic paint to form a coating on the substrate. Patent Document 1, for example, describes a method for forming a coating on a wall or roof using a catalytic paint, in which a laminate consisting of a first layer in which photocatalytic microparticles are thermally welded to the surface of a thermoplastic resin balloon, a second layer made of colloidal silica, and a third layer in which metal particles are thermally welded to the surface of a thermoplastic resin balloon is used. In other words, the first layer is a dirt-proof layer, the second layer is a heat-insulating layer, and the third layer is an antistatic layer. However, because the thermoplastic resin balloon is brought into contact with photocatalytic microparticles, the photocatalytic action of the microparticles causes the thermoplastic resin to decompose, causing the catalytic microparticles to fall off the balloon surface and gradually losing the photocatalytic function of the coating. Also, because the photocatalytic microparticles are bonded to the surface of the thermoplastic resin balloon, most of the microparticles' surface is buried in the surface of the thermoplastic resin balloon, reducing the efficiency of the microparticles' catalytic action. Patent Document 2 describes a paint in which photocatalytic particles, each having tungsten oxide microparticles attached to the surface of a white pigment particle, are dispersed in an inorganic binder. Tungsten oxide has the property of turning yellow when it absorbs light with an excitation wavelength of 450 nm, so using tungsten oxide microparticles as a paint component poses the problem of the paint film turning yellow. For this reason, Patent Document 2 adheres tungsten oxide microparticles to white pigment particles, thereby alleviating the yellow color of the tungsten oxide microparticles with the white pigment. An inorganic binder is used because using an organic binder would decompose organic compounds due to the photocatalytic action of tungsten oxide. However, since the white pigment is dispersed in an inorganic binder, the surfaces of the tungsten oxide fine particles are covered with the inorganic binder, which does not transmit ultraviolet light, and therefore the photocatalytic function of the tungsten oxide is not exhibited. As explained above, in a laminate formed using a coating material in which photocatalytic microparticles are dispersed, it is not possible to form a laminate in which most of the surfaces of the catalytic microparticles are directly exposed to the outside world and are bonded to the surface of an organic material. In other words, it is essential that the photocatalytic microparticles appear on the surface of the laminate. These requirements are well known, but the above-mentioned patent documents do not meet them.

[0003] Another conventional paint that provides catalytic action is a paint that disperses fine particles with catalytic action that promotes the combustion of harmful exhaust gases emitted from automobiles and fine particles contained in the exhaust gas. For example, Patent Document 3 describes that a porous filter is coated with a paint containing an exhaust purification catalyst that burns fine particles and harmful gases emitted from automobile diesel engines. That is, La is used as a catalyst for burning fine particles. x Ba 1-x The document describes a method in which a complex oxide with a perovskite structure consisting of FeO3 is used, and alumina powder carrying platinum is used as a catalyst for burning harmful gas components, and these are physically mixed with ceramic powder and a solvent to create a paint, which is then applied to a porous filter. However, simply applying a coating to a porous filter does not allow the complex oxide and platinum that provide catalytic activity to appear on the surface of the coating film, and the catalytic activity of the complex oxide and platinum is not exerted. As such, it is a well-known requirement that a substance that provides catalytic activity must appear on the surface of the laminate, even for a catalyst that promotes combustion, but Patent Document 3 does not satisfy this requirement. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-148026 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-106897 [Patent Document 3] Japanese Patent Application Laid-Open No. 2009-291753 Summary of the Invention [Problem to be solved by the invention]

[0005] When the surface of a catalytic substance is directly exposed to the outside world, the catalytic substance exerts its catalytic effect. Furthermore, because microparticles have a large specific surface area per unit mass, if most of the surface of the microparticles is directly exposed to the outside world, the collection of microparticles will efficiently exert their catalytic effect. However, as seen in the aforementioned patent documents, it is not easy to directly expose catalytic microparticles to the outside world. In other words, if catalytic microparticles are dispersed in a binder, the microparticles are covered by the binder and are not directly exposed to the outside world. Furthermore, even if catalytic microparticles are bonded to the surface of a balloon by heat fusion of a thermoplastic resin as described in Patent Document 1, the microparticles are buried in the heat-melted resin and bonded to the resin, preventing the microparticles from exerting their catalytic effect. Furthermore, since the fine particles exert their catalytic action by directly exposing most of their surface to the outside world, if the fine particles can be limited to the area near the surface exposed to the outside world, the amount of fine particles made of expensive noble metals that exert catalytic action can be reduced. Furthermore, if a collection of catalytic microparticles directly exposed to the outside world is not affected by chemicals, waste gases or corrosive gases, does not deteriorate thermally even in high-temperature environments, and has a certain level of mechanical strength against vibration and impact acceleration, the catalytic action of the microparticles will be maintained for a long period of time. The problems that the present invention aims to solve are explained below. First, more than 50% of the surface of the catalytic microparticles is directly exposed to the outside world. Second, clusters of microparticles are stacked one on top of another, and adjacent microparticles are bonded to each other, and the surface of the joined clusters of microparticles exhibits catalytic action. Third, if the clusters of microparticles are stacked with less than 10 microparticles overlapping each other, the amount of microparticle raw material used can be reduced. Fourth, a film that exhibits catalytic action can be used continuously for a long period of time in various environments. Fifth, a film that exhibits catalytic action can be formed by an extremely simple process. These five problems are the problems that the present invention aims to solve. [Means for solving the problem]

[0006] A method for forming a film on both surfaces of a substrate, the film being made of a collection of catalytic metal nanoparticles, is bonded to both surfaces of the substrate, so that the surfaces of the metal nanoparticles on the surface of the film are directly exposed to the outside world, and the film acts as a film that exhibits catalytic action, comprising the steps of: A metal compound having both a first property of being dispersed in methanol in a molecular state but not being dissolved in methanol and a second property of precipitating a metal having catalytic activity upon thermal decomposition is dispersed in methanol in a molecular state to prepare a methanol dispersion of the metal compound, thereafter the methanol is evaporated from the methanol dispersion of the metal compound to precipitate a cluster of crystals of the metal compound, the cluster of crystals of the metal compound is further filled into a container, and a flat plate covering the entire surface of the cluster of crystals of the metal compound is placed on top of the cluster of crystals of the metal compound, thereafter a compressive load is applied evenly over the entire surface of the flat plate. etc. and crushing the crystals of the metal compound in the container; further, repeatedly applying impact acceleration in three directions, front-to-back, left-to-right, and up-to-down, to the container to rearrange the group of crushed crystals of the metal compound in the container; thereafter, applying the compressive load evenly again to the entire surface of the flat plate to further crush the crystals of the metal compound; further, repeatedly applying the impact acceleration in the three directions to the container again; such a pair of processes consisting of applying the compressive load and applying the impact acceleration are repeated, and when the limit of the micronization of the crystals of the metal compound is reached, applying a compressive load to the flat plate will not crush the crystals, and a repulsive force will be generated from the flat plate. For this reason, a first step of stopping the pair of treatments when the repulsive force is generated and forming a collection of microcrystals of the metal compound in the container; a second step of converting a volume of the liquid organic compound in the container that is greater than the volume occupied by the cluster of fine crystals in the container into a weight, measuring the organic compound corresponding to the converted weight, mixing the weighed organic compound into the container, and stirring the organic compound to prepare a suspension in which the cluster of fine crystals of the metal compound is dispersed in the organic compound, the liquid organic compound having a first property of having a viscosity of 0.7-0.9 mPa·sec at 20°C, a second property of the crystals of the metal compound being dissolved and not dispersed in a molecular state, and a third property of having a boiling point lower than the thermal decomposition temperature of the metal compound; The substrate to which the cluster of metal nanoparticles is to be bonded is entirely immersed in the suspension in the container, and then the substrate is immersed in the suspension. Medium The substrate is then removed from the substrate, moved into a heat treatment device that thermally decomposes the metal compound, and heated to a temperature at which the metal compound is thermally decomposed. As a result, first, the organic compound is vaporized, and then the microcrystals are thermally decomposed. At this time, clusters of catalytic metal nanoparticles are simultaneously precipitated on both surfaces of the substrate and on the irregularities on both surfaces, and the clusters of metal nanoparticles are stacked. Next, the stacked clusters of metal nanoparticles are Applicable a third step in which the nanoparticles are metallically bonded at the contact points, and a collection of the metallically bonded metal nanoparticles fills in the irregularities on both surfaces of the substrate and covers both surfaces of the substrate; and further, a portion of the collection of metal nanoparticles that has filled in the irregularities on both surfaces of the substrate comes into contact with a portion of the collection of metal nanoparticles that has covered both surfaces of the substrate, and the contacting nanoparticles are metallically bonded at the contact points, so that the collection of metallically bonded metal nanoparticles is bonded to both surfaces of the substrate as a film having a thickness of less than 0.1 μm; A method for continuously carrying out all of the above three steps involves bonding a film consisting of a collection of catalytic metal nanoparticles to both surfaces of a substrate, so that the surfaces of the metal nanoparticles on the surface of the film are directly exposed to the outside world, and the film acts as a film that exhibits catalytic activity, forming the film on both surfaces of the substrate.

[0007] In other words, this method involves the sequential execution of the following three extremely simple steps, resulting in a film less than 0.1 μm thick, consisting of a cluster of catalytic metal nanoparticles, bonded to both surfaces of a substrate. Because the surface of the nanoparticles formed on the film is directly exposed to the outside world at more than 50% of its surface, the clusters of nanoparticles on the film surface efficiently exert their catalytic activity. Furthermore, because the clusters of metal nanoparticles are composed of a stack of fewer than 10 nanoparticles, the amount of metal compound used as raw material is small. Therefore, even expensive metal compounds made from precious metals can be used in extremely small amounts, resulting in inexpensive film formation. This is due to the extremely low viscosity of the organic compound, which allows the suspension adsorbed to the substrate surface to an extremely thin thickness of 0.15-0.20 μm. The first step is to crush the metal compound crystals to their limit size. For this purpose, the following three processes are carried out consecutively. First, the metal compound is dispersed in methanol, the most commonly used solvent. Next, the methanol is evaporated from the methanol dispersion. Next, a pair of processes is repeated: a process of applying a compressive load to a collection of fine crystals of the metal compound filled in a container, and a process of applying impact acceleration in three directions to the container. As a result, a collection of metal compound crystals crushed to their limit size is created. Next, the phenomena occurring in the three treatments and the effects of the three treatments will be explained. When a metal compound that precipitates metals upon thermal decomposition is dispersed in methanol, the most commonly used solvent, the metal compound disperses in the methanol in a molecular state. In contrast, when a metal compound dissolves in methanol, the metals that make up the metal compound become metal ions and dissolve in the methanol, and the dissolved metal compound cannot return to the metal compound before dissolution. Therefore, when methanol is evaporated from a methanol solution of a metal compound, crystals of the metal compound before dissolution do not precipitate. Therefore, a metal compound that does not dissolve in methanol and disperses in a molecular state is used. In other words, when methanol is evaporated from a methanol dispersion of a metal compound, the metal compound before dispersion precipitates as crystals of the metal compound smaller than 100 nm. Next, when the methanol is evaporated from the methanol dispersion of metal compounds, clusters of metal compound crystals smaller than 100 nm precipitate simultaneously. In other words, in the methanol dispersion of metal compounds, the metal compounds are in a molecular state and uniformly dispersed in the methanol. Therefore, when the methanol is evaporated, the metal compounds before dispersion precipitate simultaneously as granular crystals smaller than 100 nm. These crystals are a cluster of crystals formed by the accumulation of single molecules of the metal compounds, since the metal compounds dispersed in the methanol in a molecular state precipitated as crystals. Therefore, when stress is applied to the crystals, they are easily crushed into fine crystals. On the other hand, the finer the crystals, the more difficult it is to apply stress to them, and there is a limit to how fine the crystals can be. The evaporated methanol is recovered in a recovery machine and reused. Furthermore, a compressive load is applied uniformly via the flat plate to the collection of metal compound crystals confined within the container. At this time, the larger the crystal size, the easier it is to crush. Therefore, the larger the crystals are crushed first, and the crushing of the crystals progresses as the compressive load is applied. Meanwhile, new voids are formed within the crystal collection as a result of the crushing, and the crystals move to fill the voids while the compressive load is applied. After the applied compressive load is stopped, impact acceleration is repeatedly applied to the container in three directions: front-to-back, left-to-right, and up-to-down. At this time, the crystals do not scatter because they are confined within the container by the flat plate, but instead move to fill the voids, and the collection of crystals is rearranged within the container. After the applied impact acceleration is stopped, a compressive load is again applied uniformly via the flat plate to the collection of crystals. At this time, the aforementioned crushing of the crystals progresses for the collection of finer crystals. After this, impact acceleration is again repeatedly applied to the container in three directions to promote the rearrangement of the collection of finer crystals. This pair of processes, consisting of applying a compressive load and applying impact acceleration in three directions, is repeated. However, as the crystals become finer, it becomes more difficult to apply stress to them even with a compressive load, and there is a limit to how fine the crystals can be. When the limit of crystal refinement is reached, applying a compressive load to the plate does not crush the crystals, and a repulsive force is generated on the plate. At this point, the pair of processes is stopped. As a result, the crystal size becomes approximately 20 nm, nearly one-fifth of the size at the time of crystal precipitation. Note that when metal compound crystals precipitate, there is variation in the size of the crystals, and the size of the voids created by crushing also varies. Therefore, the size of the crushed crystals is not uniform but varies. Furthermore, the compressive load applied to the plate is equivalent to 10–100 kg weight, depending on the size of the container. The impact acceleration applied to the container is 0.3–1.0 G, depending on the size of the container. The second step is to create a suspension by dispersing a cluster of crushed microcrystals of a metal compound in a liquid organic compound. To do this, a liquid organic compound that combines three properties is mixed into the container containing the cluster of microcrystals. The organic compound must have the first property of having a viscosity of 0.7-0.9 mPa·sec at 20°C, the second property of dissolving the metal compound crystals and forming a molecular state that prevents dispersion, and the third property of having a boiling point lower than the thermal decomposition temperature of the metal compound. Next, the phenomenon that occurs in the treatment in the second step will be explained. The viscosity of the organic compound at 20°C is low at 0.7-0.9 mPa·sec., and the size of the crushed microcrystals of the metal compound is two orders of magnitude smaller than the width of the unevenness on the surface of the base material. Furthermore, the microcrystals have almost no mass, so the entire base material is suspended. Medium When the substrate is immersed in water, the suspension penetrates into the unevenness of the surface and is adsorbed to both surfaces of the substrate to a thickness of 0.15-0.20 μm. The organic compound, which has a volume greater than the volume occupied by the cluster of microcrystals, is converted into a weight value, and the organic compound containing the converted weight is mixed into the container, so that the cluster of microcrystals is easily dispersed in the organic compound. Meanwhile, the microcrystals are not dispersed in the organic compound in a molecular state, but are dispersed in a solid state. The third step is to bond the metal nanoparticles to both surfaces of the substrate as a film with a thickness of less than 0.1 μm. The phenomenon that occurs during this third step and the effects of the treatment are explained below. First, the substrate is immersed entirely in the suspension. Medium The substrate is then removed from the container and transferred to a heat treatment device where the metal compound is thermally decomposed. As described above, the suspension is adsorbed to both surfaces of the substrate immersed in the suspension to a thickness of 0.15-0.20 μm. Meanwhile, because the size of the crushed microcrystals of the metal compound is two orders of magnitude smaller than the width of the irregularities on the substrate surface, the organic compound has low viscosity, and the crushed microcrystals of the metal compound have almost no mass, the suspension penetrates into the irregularities on the substrate surface and is adsorbed to the irregularities. Next, the substrate is heated to a temperature at which the metal compound thermally decomposes. First, the organic compound evaporates from the suspension. Next, when the temperature reaches the thermal decomposition temperature of the metal compound, the crushed crystals of the metal compound decompose into inorganic or organic molecules and metal molecules, which absorb the heat of vaporization and vaporize. At this time, the water and impurities of organic matter and hydroxides present in the suspension also evaporate. The moment the inorganic or organic molecules evaporate, the metal molecules form granular metal nanoparticles approximately 10 nm in size. These catalytic metal nanoparticles precipitate simultaneously on the surface of the substrate and on the surface irregularities, forming layers on both surfaces of the substrate and on the surface irregularities. The metal nanoparticles precipitate in an active state as genuine metal nanoparticles without any impurities, and the layered metal nanoparticles form metallic bonds where they come into contact with each other. As a result, the metal-bonded metal granular nanoparticle clusters fill the irregularities on both surfaces of the substrate, and also fill both surfaces of the substrate. Furthermore, some of the metal granular nanoparticle clusters that fill the irregularities on both surfaces of the substrate come into contact with some of the metal granular nanoparticle clusters that fill both surfaces of the substrate, forming a metal bond at the contact sites. As a result, the metal-bonded metal granular nanoparticle clusters form a film with a thickness less than 0.1 μm, and the film is bonded to both surfaces of the substrate. Note that because some of the metal-bonded metal nanoparticle clusters penetrate all of the irregularities on the substrate surface, an anchor effect acts on the metal-bonded metal nanoparticle clusters, bonding them to the substrate surface with a certain degree of mechanical strength. Furthermore, because the granular nanoparticles formed on the surface of the film are metal-bonded at the contact sites between the granular nanoparticles, more than 50% of the nanoparticle surface is directly exposed to the outside world. This allows the nanoparticle clusters to efficiently exert catalytic activity. Furthermore, because the film is made up of a stack of fewer than 10 granular metal nanoparticles, the amount of metal compound used as raw material is small. Therefore, even if the metal compound is an expensive compound made from a noble metal, the amount used is extremely small, making film formation inexpensive.This is because the viscosity of the organic compound is extremely low, so the thickness of the suspension adsorbed on the surface of the substrate is extremely thin, at 0.15-0.20 μm. The three processes described above are all extremely simple, and the materials used are general-purpose industrial materials and general-purpose industrial solvents. As a result, according to the present invention, the five problems described in paragraph 5 are solved, and a film having catalytic activity can be formed over the entire surface of a substrate. Furthermore, clusters of metallically bonded granular metal nanoparticles fill both surfaces of the substrate. However, because nanoparticles of similar size form metallic bonds at contact points, more than 50% of the surface of the nanoparticle clusters is directly exposed to the outside world. This allows the surface of the metallically bonded nanoparticle clusters to efficiently exert the inherent catalytic activity based on the material that makes up the nanoparticles. Furthermore, some of the metallically bonded nanoparticle clusters penetrate the unevenness of the substrate, and these metallically bonded nanoparticle clusters form metallic bonds at contact points with the metallically bonded nanoparticle clusters on the surface of the substrate, creating an anchoring effect on the metallically bonded nanoparticle clusters. Clusters of metallically bonded nanoparticles with a thickness of less than 0.1 μm do not easily peel off from the surface of the substrate due to the anchoring effect. On the other hand, even when the substrate is composed of a two-dimensional planar shape such as a plate, sheet, flat filter, or woven wire mesh or sheet, the entire substrate can be immersed in the suspension. The suspension has a low viscosity and extremely fine metal compound crystals of approximately 20 nm, allowing the suspension to penetrate the irregularities on the substrate surface and adsorb to the entire substrate surface. This allows a collection of metal-bonded metal nanoparticles to form a catalytic film on both surfaces of the substrate or on the entire substrate surface. Furthermore, even when the substrate is composed of a three-dimensional structure with internal cavities, such as a honeycomb structure, porous filter structure, or honeycomb filter structure, the entire substrate can be immersed in the suspension. The suspension has a low viscosity and extremely fine metal compound crystals of approximately 20 nm, allowing the suspension to penetrate the irregularities on the substrate surface and adsorb to the entire substrate surface. This allows a catalytic film to be formed on the entire substrate surface. On the other hand, the substrate can be immersed in the suspension regardless of its material, so the material of the substrate is not limited.

[0008] The method of forming a film of catalytic metal nanoparticles on both surfaces of a substrate as described in paragraph 6 comprises: The metal compound that precipitates a metal upon thermal decomposition described in paragraph 6 is an inorganic metal compound that is composed of an inorganic salt having a metal complex ion in which an inorganic molecule or an inorganic ion acts as a ligand and is coordinately bonded to a metal ion, Also, The organic compound described in paragraph 6 is a saturated chain hydrocarbon having 9 to 11 carbon atoms, and the inorganic metal compound is used as the metal compound that precipitates a metal upon thermal decomposition described in paragraph 6; In addition, A method for forming a film consisting of a collection of catalytic metal nanoparticles on both surfaces of a substrate, using a chain saturated hydrocarbon as the organic compound described in paragraph 6 and forming a film consisting of a collection of catalytic metal nanoparticles on both surfaces of a substrate according to the method described in paragraph 6.

[0009] In other words, when an inorganic metal compound consisting of an inorganic salt in which molecules or ions of an inorganic substance act as ligands and have metal complex ions coordinated to metal ions is heat-treated in a reducing atmosphere, the coordinate bond is first broken and the compound decomposes into the inorganic substance and the metal. Further heating causes the inorganic substance to absorb the heat of vaporization and vaporize. Depending on the molecular weight of the inorganic substance, vaporization of the inorganic substance is completed in the temperature range of 180-220°C, and the metal precipitates. Also, Inorganic metal compounds include The inorganic metal compound disperses in methanol at a molecular level of nearly 10% by weight, but is insoluble in methanol. Therefore, the inorganic metal compound is a metal compound that combines the properties of the suspension manufacturing method described in paragraph 6. That is, among the ions that make up an inorganic metal compound, the metal ion located at the center of the molecule is the largest, and the distance between the metal ion and the ligand is the longest. When this inorganic metal compound is heat-treated in a reducing atmosphere, the coordinate bond between the metal ion and the ligand is first broken, causing decomposition into the metal and the inorganic substance. As the temperature rises further, the inorganic substance absorbs the heat of vaporization and vaporizes, and once the vaporization of the inorganic substance is complete, the metal precipitates, completing the thermal decomposition. The temperature at which the metal precipitates is the lowest of the temperatures at which metal precipitates during thermal decomposition of a metal compound. Therefore, the cost of the heat treatment is low. Furthermore, inorganic metal compounds made of inorganic salts containing metal complex ions disperse in methanol in a molecular state at nearly 10% by weight, and do not dissolve in methanol. For this reason, inorganic metal compounds, 6 The metal compounds can be used as the metal compounds that precipitate metals by thermal decomposition as described in the paragraph. In other words, a metal complex ion in which an inorganic molecule or an inorganic ion acts as a ligand and forms a coordinate bond with a metal ion is formed when the molecular weight of the ligand is small Therefore, it is easier to synthesize than other metal complex ions. Examples of such metal complex ions include ammine metal complex ions, in which ammonia (NH3) acts as a ligand and forms a coordinate bond with the metal ion; aqua metal complex ions, in which water (H2O) acts as a ligand and forms a coordinate bond with the metal ion; and hydroxyl groups (OH) - is a ligand that forms a coordinate bond with a metal ion, and chloride ion Cl - or chloride ion Cl -and chlorometal complex ions, in which ammonia (NH3) acts as a ligand and is coordinated to a metal ion. Furthermore, inorganic metal compounds made of inorganic salts such as chlorides, sulfates, and nitrates with such metal complex ions are easy to synthesize, and the molecular weight of the inorganic salt is small Therefore, the vaporization of inorganic compounds is completed and metals are precipitated in the temperature range of 180-220°C. This temperature at which metals are precipitated is the lowest temperature at which metals are precipitated by thermal decomposition of metal compounds. These inorganic metal compounds are common industrial chemicals. On the other hand, there are liquid organic compounds that have all three of the properties described in paragraph 6: saturated chain hydrocarbons with 9-11 carbon atoms. These organic compounds are general-purpose industrial organic solvents. Nonane CH3(CH2)7CH3, which has nine carbon atoms, has a viscosity of 0.714 mPa·s at 20°C, a boiling point of 151°C, and possesses the three properties of dissolving inorganic metal compounds and preventing dispersion in a molecular state. Its melting point is also low at -51°C. Decane, CH3(CH2)8CH3, which has 10 carbon atoms, has a viscosity of 0.920 mPa·s at 20°C, a boiling point of 174°C, and possesses the three properties of dissolving inorganic metal compounds and preventing dispersion in a molecular state. It also has a low melting point of -30°C. Furthermore, undecane CH3(CH2)9CH3, which has 11 carbon atoms, has a viscosity of 0.812 mPa·s at 25°C, a boiling point of 196°C, and possesses the three properties of dissolving inorganic metal compounds and preventing dispersion in a molecular state. Its melting point is -26°C. As explained above, inorganic metal compounds made of inorganic salts containing metal complex ions are metal compounds that have both of the properties described in paragraph 6. Furthermore, saturated chain hydrocarbons with 9-11 carbon atoms are organic compounds that have all three of the properties described in paragraph 6.

[0010] The method of forming a film of catalytic metal nanoparticles on both surfaces of a substrate as described in paragraph 6 comprises: The metal compound that precipitates a metal upon thermal decomposition described in paragraph 6 is a metal octylate compound, Also, The organic compound described in paragraph 6 is a saturated chain hydrocarbon having 9 to 11 carbon atoms, and the metal octylate compound is used as the metal compound described in paragraph 6 that precipitates a metal upon thermal decomposition; Also, A method for forming a film consisting of a collection of catalytic metal nanoparticles on both surfaces of a substrate, using the chain saturated hydrocarbon as the organic compound described in paragraph 6 and following the method described in paragraph 6.

[0011] In other words, when metal octylate compounds are heat-treated at 290°C in an air atmosphere, they precipitate metal. Furthermore, they disperse in a molecular state at nearly 10% by weight in methanol and are insoluble in methanol. Therefore, metal octylate compounds are metal compounds that combine the two properties required for the method of producing the suspension described in paragraph 6. That is, among the ions constituting the metal octylate compound, the metal ion is the largest. Therefore, in a metal octylate compound in which the oxygen ion constituting the carboxyl group of octylic acid is covalently bonded to a metal ion, the distance between the oxygen ion constituting the carboxyl group and the metal ion is longer than the distance between other ions. When a metal octylate compound with this molecular structure is heat-treated in an air atmosphere, the bond between the oxygen ion constituting the carboxyl group and the metal ion is first broken above the boiling point of octylic acid, 228°C, resulting in separation into octylic acid and the metal. Furthermore, because octylic acid is a saturated fatty acid and does not have an unsaturated structure in which carbon atoms are in excess of hydrogen atoms, the octylic acid absorbs the heat of vaporization and vaporizes, and the metal precipitates at 290°C, when vaporization is complete. Furthermore, when a metal octylate compound is heat-treated in a nitrogen atmosphere, the metal precipitates at 330°C. In other words, the carboxylate anion (R-COO) of a carboxylic acid consisting of saturated fatty acid -), but metal carboxylate compounds that are covalently bonded to metal ions precipitate the metal through thermal decomposition. These metal carboxylate compounds include metal octylate compounds, metal laurate compounds, and metal stearates compounds, in order of decreasing thermal decomposition temperature at which they precipitate the metal. Therefore, when metal octylate compounds, which have the lowest thermal decomposition temperature, are used, 6 The suspension described in paragraph 1 can be produced inexpensively. Note that, like the metal octylate compound, the metal laurate compound and the metal stearate compound are dispersed in methanol at a molecular level of nearly 10% by weight, and are not dissolved in methanol. That is, the boiling point of lauric acid is 296° C., and the thermal decomposition temperature of metal laurate compound is 360° C. However, the thermal decomposition temperatures of metal laurate compound and metal stearate compound are higher than the thermal decomposition temperature of metal octylate compound, and therefore it is desirable to use metal octylate compound as a raw material for depositing metal. Compared with metal carboxylate compounds made from saturated fatty acids, metal carboxylate compounds made from unsaturated fatty acids have an excess of carbon atoms relative to hydrogen atoms, and therefore, upon thermal decomposition, metal oxides are precipitated simultaneously; for example, in the case of copper oleate, cuprous oxide (CuO) and cupric oxide (CuO). This requires the cost of reducing the cuprous oxide and cupric oxide to copper. In particular, the cost of copper oxide is high because it must be oxidized to cupric oxide in an atmosphere richer in oxygen than air and then further reduced to copper in a reducing atmosphere. Furthermore, metal octylate compounds are inexpensive industrial chemicals that can be easily synthesized. That is, when octylic acid is reacted with a strong alkali, an alkali metal octylate compound is produced. Then, when the alkali metal octylate compound is reacted with an inorganic metal compound, metal octylate compounds composed of various metals are produced. In addition, octylic acid is a commonly used organic acid. Therefore, metal octylate compounds are the cheapest organometallic compounds. For this reason, their thermal decomposition temperature is higher than that of the complexes composed of inorganic metal compounds described in paragraphs 8-9, but Made of inorganic metal compounds It is a metal compound that is cheaper than a complex. As explained above, metal octylate compounds are metal compounds that combine two properties in the method for producing the suspension described in paragraph 6, and also serve as an inexpensive raw material for metal microparticles. In addition, the chain saturated hydrocarbons with 9-11 carbon atoms described in paragraph 9 are organic compounds that have a boiling point lower than the thermal decomposition temperature of the metal octylate compound and possess the three properties described in paragraph 6.

[0012] A method for forming a film on both surfaces of a substrate, the film being made of an aggregate of catalytic metal oxide nanoparticles, is bonded to both surfaces of the substrate, so that the surfaces of the metal oxide nanoparticles on the surface of the film are directly exposed to the outside world, and the film acts as a film that exhibits catalytic activity, comprising the steps of: A metal compound having both a first property of being dispersed in methanol in a molecular state but not dissolving in methanol and a second property of precipitating a metal oxide having catalytic activity upon thermal decomposition is dispersed in methanol in a molecular state to prepare a methanol dispersion of the metal compound, then methanol is evaporated from the methanol dispersion of the metal compound to precipitate a cluster of crystals of the metal compound, the cluster of crystals of the metal compound is filled into a container, and a flat plate covering the entire surface of the cluster of crystals of the metal compound is placed on top of the cluster of crystals of the metal compound, then a compressive load is applied evenly to the entire surface of the flat plate to precipitate the cluster of crystals of the metal compound in the container. the crystals of the metal compound are crushed; further, impact acceleration is repeatedly applied to the container in three directions, i.e., front-to-back, left-to-right, and up-to-down, to rearrange the group of crushed crystals of the metal compound in the container; thereafter, the compressive load is applied evenly again to the entire surface of the plate to further crush the crystals of the metal compound; further, the impact acceleration in the three directions is repeatedly applied to the container again; these paired processes consisting of the process of applying the compressive load and the process of applying the impact acceleration are repeated until the limit of the micronization of the crystals of the metal compound is reached, and even if a compressive load is applied to the plate, the crystals are not crushed and a repulsive force is generated from the plate. For this reason, a first step of stopping the pair of treatments at the time when the repulsive force is generated and forming a collection of microcrystals of the metal compound in the container; a second step of converting a volume of the liquid organic compound in the container that is greater than the volume occupied by the cluster of fine crystals in the container into a weight, the organic compound being a liquid having a first property of having a viscosity of 0.7-0.9 mPa·sec at 20°C, a second property of the crystals of the metal compound being dissolved and not dispersed in a molecular state, and a third property of having a boiling point lower than the thermal decomposition temperature of the metal compound, the organic compound being a liquid having a volume greater than the volume occupied by the cluster of fine crystals in the container, the organic compound having the converted weight, mixing the weighed organic compound into the container, and stirring the organic compound to prepare a suspension in which the cluster of fine crystals is dispersed in the organic compound; A substrate made of a flat plate to which a collection of metal oxide nanoparticles is to be bonded is entirely immersed in the suspension in the container, and then the substrate is immersed in the suspension. Medium The substrate is taken out from the oven, and the entire substrate is sandwiched between two flat plates of the same shape that are larger than the substrate. The substrate sandwiched between the two flat plates is then moved into a heat treatment device that thermally decomposes the metal compound. The entire surface of one of the two flat plates is uniformly compressed, and the temperature is raised to a temperature at which the metal compound is thermally decomposed. This first vaporizes the organic compound, and then Metal Compounds a third step in which the microcrystals are thermally decomposed, during which clusters of catalytic metal oxide nanoparticles are simultaneously precipitated on both surfaces of the substrate and on the irregularities on both surfaces, resulting in a stack of the clusters of metal oxide nanoparticles; a compressive stress is then applied to the clusters of metal oxide nanoparticles, causing the nanoparticles to be joined by friction welding at the contact points, with the joined clusters of metal oxide nanoparticles filling the irregularities on both surfaces of the substrate and covering both surfaces; and a portion of the clusters of metal oxide nanoparticles that have filled the irregularities on both surfaces of the substrate come into contact with a portion of the clusters of metal oxide nanoparticles that have covered both surfaces of the substrate, causing the contacting nanoparticles to be joined by frictional heat at the contact points; and as a result, the clusters of metal oxide nanoparticles joined by friction welding are joined to both surfaces of the substrate as a film having a thickness of less than 0.1 μm; A method for continuously carrying out all of the above three steps involves bonding a film consisting of a collection of catalytic metal oxide nanoparticles to both surfaces of a substrate, so that the surfaces of the metal oxide nanoparticles on the surface of the film are directly exposed to the outside world, and the film acts as a film that exhibits catalytic activity, forming the film on both surfaces of the substrate.

[0013] In other words, this method involves the sequential execution of the following three extremely simple steps, resulting in a film less than 0.1 μm thick, consisting of a cluster of catalytic metal oxide nanoparticles, bonded to both surfaces of a substrate. Because the surface of the nanoparticles formed on the film is directly exposed to the outside world over more than 50% of the surface area, the clusters of nanoparticles on the film surface efficiently exert their catalytic activity. Furthermore, because the clusters of metal oxide nanoparticles joined by friction welding consist of a layer of fewer than 10 nanoparticles, the amount of metal compound used as raw material is small. Therefore, even if the metal compound is expensive, only a very small amount is used, resulting in inexpensive film formation. This is due to the extremely low viscosity of the organic compound, which allows the suspension to adsorb to the surface of the substrate to an extremely thin thickness of 0.15-0.20 μm. The first step is to crush the metal compound crystals to their limit size. For this purpose, the following three processes are carried out consecutively. First, the metal compound is dispersed in methanol, the most commonly used solvent. Next, the methanol is evaporated from the methanol dispersion. Next, a pair of processes is repeated: a process of applying a compressive load to a collection of fine crystals of the metal compound filled in a container, and a process of applying impact acceleration in three directions to the container. As a result, a collection of metal compound crystals crushed to their limit size is created. Next, the phenomena occurring in the three treatments and the effects of the three treatments will be explained. When a metal compound that precipitates metal oxides upon thermal decomposition is dispersed in methanol, the most commonly used solvent, the metal compound disperses in the methanol in a molecular state. In contrast, when a metal compound dissolves in methanol, the metals that make up the metal compound become metal ions and dissolve in the methanol, and the dissolved metal compound cannot return to the metal compound before dissolution. Therefore, when methanol is evaporated from a methanol solution of a metal compound, crystals of the metal compound before dissolution do not precipitate. Therefore, a metal compound that does not dissolve in methanol and disperses in a molecular state is used. In other words, when methanol is evaporated from a methanol dispersion of a metal compound, the metal compound before dispersion precipitates as crystals of the metal compound smaller than 100 nm. Next, when the methanol is evaporated from the methanol dispersion of metal compounds, clusters of metal compound crystals smaller than 100 nm precipitate simultaneously. In other words, in the methanol dispersion of metal compounds, the metal compounds are in a molecular state and uniformly dispersed in the methanol. Therefore, when the methanol is evaporated, the metal compounds before dispersion precipitate simultaneously as granular crystals smaller than 100 nm. These crystals are a cluster of crystals formed by the accumulation of single molecules of the metal compounds, since the metal compounds dispersed in the methanol in a molecular state precipitated as crystals. Therefore, when stress is applied to the crystals, they are easily crushed into fine crystals. On the other hand, the finer the crystals, the more difficult it is to apply stress to them, and there is a limit to how fine the crystals can be. The evaporated methanol is recovered in a recovery machine and reused. Furthermore, a compressive load is applied to the collection of metal compound crystals confined within the container via a flat plate. In this case, the larger the crystal size, the easier it is to crush. Therefore, the larger the crystals are crushed first, and the crushing of the crystals progresses while the compressive load is applied. Meanwhile, new voids are formed in the crystal collection as a result of the crushing, and the crystals move to fill the voids while the compressive load is applied. After the compressive load is stopped, impact acceleration is repeatedly applied to the container in three directions: front-to-back, left-to-right, and up-to-down. During this process, the crystals do not scatter because they are confined within the container by the flat plate, but instead move to fill the voids, and the collection of crystals is rearranged within the container. Furthermore, after the impact acceleration is stopped, a compressive load is again applied to the collection of crystals via the flat plate. During this process, the aforementioned crushing of the crystals progresses for the collection of finer crystals. After this, impact acceleration is again repeatedly applied to the container in three directions, and the rearrangement of the collection of finer crystals progresses. This pair of processes consisting of the process of applying a compressive load and the process of applying impact acceleration in three directions is repeated. On the other hand, the finer the crystals, the more difficult it becomes to apply stress to them, even when compressive load is applied, and there is a limit to how fine the crystals can be. When the limit of crystal miniaturization is reached, applying a compressive load to the plate does not crush the crystals, and a repulsive force is generated on the plate. At this point, the pair of processes is stopped. As a result, the size of the crystals becomes approximately 20 nm, nearly one-fifth of the size at the time of crystal precipitation. Note that when metal compound crystals precipitate, there is variation in the size of the crystals, and the size of the voids created by crushing also varies. Therefore, the size of the crushed crystals is not uniform but varies. Furthermore, the compressive load applied to the plate is equivalent to 10-100 kg weight, depending on the size of the container. Furthermore, the impact acceleration applied to the container is 0.3-1.0 G, depending on the size of the container. The second step is to create a suspension by dispersing a cluster of crushed microcrystals of a metal compound in a liquid organic compound. To do this, a liquid organic compound that combines three properties is mixed into the container containing the cluster of microcrystals. The organic compound must have the first property of having a viscosity of 0.7-0.9 mPa·sec at 20°C, the second property of dissolving the metal compound crystals and forming a molecular state that prevents dispersion, and the third property of having a boiling point lower than the thermal decomposition temperature of the metal compound. Next, the phenomenon that occurs in the treatment in the second step will be explained. The viscosity of the organic compound at 20°C is low at 0.7-0.9 mPa·sec, and the size of the crushed microcrystals of the metal compound is two orders of magnitude smaller than the width of the unevenness on the surface of the substrate, and the microcrystals have almost no mass. Therefore, the entire substrate, which bonds clusters of nanoparticles of metal oxides with catalytic properties to the surface, can be dissolved in a suspension. Medium When the substrate is immersed in water, the suspension penetrates into the unevenness of the surface and is adsorbed to both surfaces of the substrate to a thickness of 0.15-0.20 μm. The organic compound, which has a volume greater than the volume occupied by the cluster of microcrystals, is converted into a weight value, and the organic compound of this converted weight is mixed into the container, so that the cluster of microcrystals is easily dispersed in the organic compound. Meanwhile, the microcrystals are not dispersed in the organic compound in a molecular state, but are dispersed in a solid state. The third step involves friction welding the friction-welded metal oxide nanoparticle clusters to both surfaces of a substrate as a film with a thickness less than 0.1 μm. First, the entire substrate is immersed in the suspension. As mentioned above, the suspension is adsorbed to both surfaces of the immersed substrate to a thickness of 0.15-0.20 μm. Meanwhile, because the size of the crushed microcrystals of the metal compound is two orders of magnitude smaller than the width of the irregularities on the substrate surface, the organic compound has low viscosity, and the crushed microcrystals of the metal compound have almost no mass, the suspension penetrates into the irregularities on the substrate surface and is adsorbed to the irregularities. Next, the substrate is dissolved in the above-mentioned suspension. Medium The substrate is then taken out from the mold and the entire substrate is sandwiched between two flat plates of the same shape but larger than the substrate. After this, the substrate sandwiched between the two flat plates is moved into a heat treatment device that thermally decomposes the metal compound, and the entire surface of one of the two flat plates is uniformly heated. etc. The suspension is compressed to a temperature at which the metal compound thermally decomposes, and the temperature is raised to the temperature at which the metal compound thermally decomposes. This causes the organic compound to vaporize first. Next, when the temperature reaches the temperature at which the metal compound thermally decomposes, the microcrystals first decompose into organic molecules and metal oxide molecules, and the organic molecules absorb the heat of vaporization and vaporize. At this time, the moisture and organic matter and hydroxides present in the suspension as impurities also vaporize. The moment the organic molecules complete their vaporization, a cluster of metal oxide molecules forms granular metal oxide nanoparticles with a size of about 10 nm. These catalytic metal oxide nanoparticles precipitate simultaneously on the surface of the substrate and on the surface irregularities, and the clusters of metal oxide nanoparticles are layered on both surfaces of the substrate and on the surface irregularities. Next, compressive stress is applied to the clusters of granular metal oxide nanoparticles, causing them to bond by friction welding at the contact points. The clusters of granular metal oxide nanoparticles fill the irregularities on both surfaces of the substrate, filling both surfaces. Furthermore, some of the clusters of metal oxide nanoparticles that have filled the irregularities on both surfaces of the substrate come into contact with some of the clusters of metal oxide nanoparticles that have filled both surfaces of the substrate, and the contacting nanoparticles are bonded by friction heat at the contact points. As a result, the clusters of granular metal oxide nanoparticles bonded by friction welding are bonded to both surfaces of the substrate as a film with a thickness of less than 0.1 μm. Furthermore, because the granular nanoparticles formed on the surface of the film are bonded by friction welding at the contact points, more than 50% of the nanoparticle surface is directly exposed to the outside world. This allows the clusters of nanoparticles to efficiently exert their catalytic action. Furthermore, the granular nanoparticles of metal oxides joined by friction welding are composed of layers of fewer than 10 nanoparticles, so the amount of metal compound used as raw material is small. Therefore, even if the metal compound is expensive, only a very small amount is used, so film formation can be done at low cost. This is because the viscosity of the organic compound is extremely low, so the thickness of the suspension adsorbed on the surface of the substrate is extremely thin, at 0.15-0.20 μm. The three processes described above are all extremely simple, and the materials used are general-purpose industrial materials and general-purpose industrial solvents. As a result, according to the present invention, the five problems described in paragraph 5 are solved, and a film having catalytic activity can be formed over the entire surface of a substrate. The granular metal oxide nanoparticle clusters bonded by friction welding fill both surfaces of the substrate. However, because the surfaces of the metal oxide nanoparticle clusters are made up of similarly sized nanoparticles that are bonded by friction welding at the contact points, more than 50% of the nanoparticle surface is directly exposed to the outside world. This allows the surface of the bonded nanoparticle clusters to efficiently exhibit the inherent catalytic activity of the nanoparticles' constituent materials. Furthermore, some of the nanoparticle clusters bonded by friction welding penetrate into the unevenness of the substrate. The clusters of nanoparticles that have penetrated into the unevenness are then bonded by friction welding at the contact points with the clusters of nanoparticles on the surface of the substrate, creating an anchoring effect on the clusters of nanoparticles. Clusters of nanoparticles bonded by friction welding with a thickness of less than 0.1 μm do not easily peel off from the surface of the substrate due to the anchoring effect. On the other hand, when the substrate is a flat plate or sheet, the aggregate of metal oxide nanoparticles is uniformly distributed over the entire surface of the laminated substrate. etc. Since the suspension can be compressed to a small size, the collection of metal oxide nanoparticles is compressed and the nanoparticles are joined by friction welding at the contact points, forming a catalytic film on both surfaces of the substrate. On the other hand, the substrate can be immersed in the suspension regardless of its material, so the material of the substrate is not limited.

[0014] The method of forming a film of catalytic metal oxide nanoparticles on both surfaces of a substrate as described in paragraph 12 comprises: The metal compound that precipitates a metal oxide upon thermal decomposition as described in paragraph 12 is a complex consisting of a carboxylic acid metal compound in which an oxygen ion constituting a carboxyl group of a carboxylic acid is coordinately bonded to a metal ion, Also,The organic compound described in paragraph 12 is a chain saturated hydrocarbon having 9 to 11 carbon atoms, and a complex of the carboxylic acid metal compound is used as the metal compound described in paragraph 12 that precipitates a metal oxide by thermal decomposition, In addition, A method for forming a film consisting of a collection of catalytic metal oxide nanoparticles on both surfaces of a substrate, using a chain saturated hydrocarbon as the organic compound described in paragraph 12 and forming a film consisting of a collection of catalytic metal oxide nanoparticles on both surfaces of a substrate according to the method described in paragraph 12.

[0015] That is, when a complex of a metal carboxylate compound is heat-treated in an air atmosphere at a temperature of 180-330°C, it precipitates a metal oxide. Furthermore, it disperses in a molecular state in methanol and is insoluble in methanol. Therefore, the complex of a metal carboxylate compound is a metal compound that combines the two properties in the method for producing a suspension described in paragraph 12. That is, the carboxylate anion of carboxylic acid (R-COO - A complex consisting of a carboxylate metal compound in which a ligand approaches and coordinates with a metal ion is formed by combining a carboxylate anion (R-COO) with the metal ion, which is the largest ion. - ) approach each other and form a coordinate bond, shortening the distance between them. This allows the carboxylate anion (R-COO - ) is at the longest distance from the ion covalently bonded to the opposite side of the metal ion. When the boiling point of the carboxylic acid is exceeded, the carboxylate anion (R-COO - The bond between the metal ion and the covalent ion on the other side of the metal ion is first broken, and the carboxylic acid decomposes into a metal oxide, which is a compound of the metal ion and oxygen ion, and a carboxylic acid. If the temperature is further increased, the carboxylic acid absorbs the heat of vaporization and vaporizes. The vaporization of the carboxylic acid progresses depending on the molecular weight of the carboxylic acid and the number of carboxylic acids in the coordinate bond. Once vaporization is complete, the metal oxide precipitates, completing the thermal decomposition. Metal carboxylate compounds with these molecular structural characteristics include metal acetate compounds, metal caprylate compounds, metal benzoate compounds, and metal naphthenate compounds. Complexes consisting of these metal carboxylate compounds undergo thermal decomposition in an air atmosphere at 180-330°C depending on the boiling point of the carboxylic acid. That is, the boiling point of acetic acid is 118°C, that of caprylic acid is 237°C, and that of benzoic acid is 249°C. On the other hand, naphthenic acid is a mixture of saturated fatty acids with a five-membered ring, and has the general formula C n H 2n-1 It is represented by COOH and its main component is CH with a boiling point of 268°C and a molecular weight of 170. 17 The metal naphthenate compounds are composed of COOH. Therefore, the thermal decomposition temperature of metal naphthenate compounds is as high as 330°C among complexes composed of metal carboxylate compounds. Therefore, metal acetate compounds, metal caprylate compounds, metal benzoate compounds, and metal naphthenate compounds can be used as metal compounds that combine the two properties described in paragraph 12. On the other hand, among metal acetate compounds, there are metal acetate compounds that dissolve in methanol. There are also metal acetate compounds that precipitate amorphous metal oxides upon thermal decomposition. The composition of the amorphous metal oxides is not constant. These metal acetate compounds cannot be used as raw materials for metal oxide microparticles. Furthermore, among metal acetate compounds or metal caprylate compounds, there are metal acetate compounds or metal caprylate compounds that precipitate amorphous metal oxides upon thermal decomposition. These metal acetate compounds or metal caprylate compounds cannot be used as raw materials for metal oxide microparticles. Furthermore, among metal acetate compounds, metal caprylate compounds, and metal benzoate compounds, oxygen ions approach and coordinate with metal ions to form binuclear complex salts, but these metal acetate compounds, metal caprylate compounds, and metal benzoate compounds are unstable substances during thermal decomposition and are difficult to handle during thermal decomposition. Among these metal carboxylate compounds, metal naphthenate compounds are used as raw materials for metal oxide microparticles. Therefore, depending on the substance of the metal oxide precipitated by thermal decomposition, a complex made of a metal carboxylate compound is used as a raw material for the fine crystals of the metal carboxylate compound. Furthermore, complexes of metal carboxylate compounds are inexpensive industrial chemicals that can be easily synthesized. That is, when a carboxylic acid is reacted with a strong alkali, an alkali metal carboxylate compound is produced. Then, when the alkali metal carboxylate compound is reacted with an inorganic metal compound, complexes of metal carboxylate compounds composed of various metals are synthesized. Furthermore, the raw material, carboxylic acid, is an inexpensive organic acid. Therefore, it is the cheapest organometallic compound among organometallic compounds. As explained above, a complex consisting of a metal carboxylate compound is a metal compound that precipitates a metal oxide by thermal decomposition in the manufacturing method for producing the suspension described in paragraph 12, and also serves as an inexpensive raw material for metal oxide microparticles. In addition, the chain saturated hydrocarbons with 9-11 carbon atoms described in paragraph 9 have boiling points lower than the thermal decomposition temperature of complexes made of carboxylic acid metal compounds, and are organic compounds that combine the three properties described in paragraph 12. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a cross-sectional view that schematically illustrates the structure of a film in which clusters of palladium nanoparticles are stacked and bonded to both surfaces of a flat polyacetal resin plate. [Figure 2] This is a schematic diagram illustrating a cross section of three layers of film stacked and bonded to a honeycomb ceramic. DETAILED DESCRIPTION OF THE INVENTION

[0017] Embodiment 1 This section describes the catalytic action exerted by metals or metal oxides and catalytic devices using them. Note that because there are a wide variety of catalytic actions exerted by a single type of metal or a single type of metal oxide and catalytic devices using them, only a representative catalytic device will be described here. First, we will explain the catalytic action of platinum group metals. The most well-known platinum group metal catalysts oxidize hydrocarbons (HC) contained in automobile exhaust gases to water and carbon dioxide (CO2), oxidize carbon monoxide (CO) to carbon dioxide, and oxidize nitrogen oxides (NO).x There is a three-way catalytic converter that reduces CO₂ to nitrogen. The first embodiment of the present invention is an embodiment in which catalytic action is simultaneously exerted by the aggregation of nanoparticles of three types of metals consisting of palladium, platinum, and rhodium. For this purpose, an inorganic metal compound consisting of a metal complex that precipitates palladium, platinum, or rhodium by thermal decomposition is used as the metal compound that precipitates palladium, platinum, or rhodium by thermal decomposition, 6 paragraphs and Three types of suspensions are prepared according to the method described in paragraph 8. In addition, a honeycomb ceramic having a large number of elongated through holes formed therein is prepared, and the honeycomb ceramic is used as the substrate described in paragraph 8. Next, the honeycomb ceramic is immersed in each suspension, the depth of the immersion decreasing with each subsequent immersion. The honeycomb ceramic is then pulled out and heated to a temperature at which the inorganic metal compound thermally decomposes. This results in a film less than 0.1 μm thick, consisting of clusters of metal-bonded palladium nanoparticles, platinum nanoparticles, and rhodium nanoparticles, bonded to the surface of three different locations within the through-holes of the honeycomb ceramic. As a result, the honeycomb ceramic simultaneously exhibits catalytic activity due to the clusters of nanoparticles of the three different platinum group metals. In other words, in the three regions of the honeycomb ceramic, only the suspension adsorbs to the surface of the honeycomb ceramic in the region immersed in the suspension in which the inorganic compound of the palladium complex is dispersed, and when the inorganic compound is thermally decomposed, clusters of metallically bonded palladium nanoparticles are formed on the surface of the honeycomb ceramic, and the surface of this region exhibits catalytic action due to the clusters of palladium nanoparticles. Furthermore, the clusters of palladium nanoparticles precipitated on the uneven surface of the honeycomb ceramic provide an anchor effect, so that the clusters of palladium nanoparticles are bonded to the honeycomb ceramic with a certain strength. Next, at the site immersed in the suspension of the platinum complex inorganic compound, the suspension of the platinum complex inorganic compound adsorbs onto the surface where the suspension of the palladium complex inorganic compound is adsorbed. When the inorganic compound is thermally decomposed, clusters of metal-bonded platinum nanoparticles are formed on the surface of the clusters of metal-bonded palladium nanoparticles. Clusters of metal-bonded platinum nanoparticles are formed on the surface of this site, resulting in the catalytic action of the platinum nanoparticles. Furthermore, since nanoparticles made of genuine metals are precipitated in an active state, palladium nanoparticles that come into contact with platinum nanoparticles form a metallic bond with the platinum nanoparticles. Therefore, all clusters of nanoparticles of the two types of metals are metallically bonded. Furthermore, the clusters of palladium nanoparticles precipitated on the uneven surface of the honeycomb ceramic provide an anchoring effect, so the clusters of nanoparticles of the two types of metals are bonded to the honeycomb ceramic with a certain strength. Furthermore, at the site immersed in the suspension in which the inorganic compound of a rhodium complex is dispersed, the suspension in which the inorganic compound of a platinum complex is dispersed is adsorbed onto the surface to which the suspension in which the inorganic compound of a palladium complex is adsorbed, and further, the suspension in which the inorganic compound of a rhodium complex is adsorbed. Therefore, when the inorganic compound is thermally decomposed, clusters of metallic-bonded platinum nanoparticles are formed on the surface of the clusters of metallic-bonded palladium nanoparticles, and further clusters of metallic-bonded rhodium nanoparticles are formed. Since clusters of metallic-bonded rhodium nanoparticles are formed on the surface of this site, the catalytic action of the rhodium nanoparticles is exerted. Note that, since nanoparticles made of genuine metals are precipitated in an active state, nanoparticles in which palladium nanoparticles come into contact with platinum nanoparticles are metallically bonded to the platinum nanoparticles. Furthermore, nanoparticles in which platinum nanoparticles come into contact with rhodium nanoparticles are metallically bonded to the rhodium nanoparticles. Therefore, all clusters of nanoparticles of three types of metals are metallically bonded. In addition, the clusters of palladium nanoparticles deposited on the uneven surface of the honeycomb ceramic provide an anchoring effect, so the clusters of nanoparticles of the three types of metals are bonded to the honeycomb ceramic with a certain strength. On the other hand, an inorganic metal compound consisting of a ruthenium complex that precipitates ruthenium by thermal decomposition is used as the metal compound that precipitates ruthenium by thermal decomposition, 6 paragraphs and A first suspension is prepared according to the method described in paragraph 8. An inorganic metal compound consisting of a metal complex that precipitates palladium or platinum upon thermal decomposition is used as the metal compound that precipitates palladium or platinum upon thermal decomposition, 6 paragraphs and A second suspension is prepared according to the method described in paragraph 8. One end of the honeycomb ceramic is then immersed in the first suspension up to one-third of the length of the honeycomb ceramic, and the other end of the honeycomb ceramic is then immersed in the second suspension up to two-thirds of the length of the honeycomb ceramic. The temperature is then raised to a temperature at which the inorganic metal compound thermally decomposes. As a result, films less than 0.1 μm thick consisting of clusters of metallically bonded ruthenium nanoparticles and clusters of palladium or platinum nanoparticles are bonded to different portions of the honeycomb ceramic surface. When the portion of the honeycomb ceramic where the clusters of ruthenium nanoparticles are bonded is placed upstream of a three-way catalytic converter, the clusters of ruthenium nanoparticles oxidize carbon monoxide in the exhaust gas to carbon dioxide. Therefore, the area where the clusters of palladium nanoparticles or clusters of platinum nanoparticles located downstream are joined does not experience the poisoning phenomenon in which catalytic activity is lost due to the adsorption of carbon monoxide gas, and the catalytic function of the clusters of palladium nanoparticles or clusters of platinum nanoparticles can be efficiently exerted. Ruthenium, a platinum group metal, exhibits catalytic activity when hydrogenating C=C double bonds and C-C triple bonds to C-C single bonds, and when hydrogenating aromatic hydrocarbons to reduce them to saturated hydrocarbons. In the next embodiment of the present invention, an inorganic metal compound comprising a ruthenium complex that precipitates ruthenium by thermal decomposition is used as the metal compound that precipitates ruthenium by thermal decomposition, 6 paragraphs andA suspension is prepared according to the method described in paragraph 8. The honeycomb ceramic is immersed in the suspension, removed, and then heated to a temperature at which the inorganic metal compound thermally decomposes. This results in a film of ruthenium nanoparticles less than 0.1 μm thick being bonded to the surface of the honeycomb ceramic. The honeycomb ceramic is then heated, and a liquid consisting of various hydrocarbons is atomized and passed through the elongated through-holes in the honeycomb ceramic. The honeycomb ceramic acts as a microreactor device, hydrogenating the hydrocarbons into lower molecular weight hydrocarbons. Secondly, the catalytic action of silver will be explained. For example, the catalytic action of silver is the catalytic action of oxidizing carbon monoxide to carbon dioxide. In an embodiment of the present invention, an inorganic metal compound made of a silver complex that precipitates silver by thermal decomposition is used as the metal compound that precipitates silver by thermal decomposition. 6 paragraphs and A suspension is prepared according to the method described in paragraph 8. A collection of tobacco leaves is placed in a wire mesh container, which is immersed in the suspension and agitated to agitate the tobacco leaves within the suspension. The container is then removed. The temperature is then raised to a temperature at which the inorganic metal compound thermally decomposes, and a collection of silver nanoparticles is bonded to the surface of the tobacco leaves as a film less than 0.1 μm thick. In other words, the tobacco leaves are used as the substrate described in paragraph 8. The tobacco leaves are then processed into cigarettes. Smokers who smoke these cigarettes avoid inhaling toxic carbon monoxide, as carbon monoxide gas generated during tobacco combustion is oxidized to carbon dioxide by the catalytic action of the silver. The collection of silver nanoparticles is then separated from the cigarette butt and ash, and the silver nanoparticles are reused. In addition, an inorganic metal compound comprising a silver complex that precipitates silver by thermal decomposition is used as the metal compound that precipitates silver by thermal decomposition, 6 paragraphs andA suspension is prepared according to the method described in paragraph 8. A cloth (fabric) is immersed in the suspension, removed, and heated to the thermal decomposition temperature of the inorganic metal compound. Ag nanoparticles are bonded to the surface of the cloth (fabric) as a film less than 0.1 μm thick. This cloth (fabric) possesses antibacterial properties due to the silver nanoparticles, making it suitable for use in a variety of antibacterial clothing, gauze, masks, and other products. The cloth (fabric) is heated to 180-220°C, the temperature at which the inorganic metal compound thermally decomposes. However, due to the low temperature and the reducing atmosphere, the synthetic resins that make up the cloth (fabric) are not thermally decomposed, and the natural fibers that make up the cloth (fabric) do not self-ignite. Thirdly, the catalytic action of copper will be explained. For example, the catalytic action of copper is used in the synthesis of methanol, which is expected to see increasing demand as a fuel in the future. In an embodiment of the present invention, an inorganic metal compound consisting of a copper complex is used as the metal compound from which copper precipitates by thermal decomposition, 6 paragraphs and A suspension is prepared according to the method described in paragraph 8. The honeycomb ceramic is immersed in the suspension and then removed. The temperature is then raised to a temperature at which the inorganic metal compound thermally decomposes. This results in a cluster of copper nanoparticles being bonded to the surface of the honeycomb ceramic as a film less than 0.1 μm thick. When a mixed gas consisting of carbon monoxide and hydrogen, pressurized to 5-10 MPa and heated to around 300°C, is passed through the elongated through-holes in the honeycomb ceramic, the honeycomb ceramic functions as a microreactor device for synthesizing methanol. Fourth, the catalytic action of titanium oxide (TiO2) will be explained. Titanium oxide exhibits, for example, photocatalytic action. In an embodiment of the present invention, titanium benzoate is used as the metal compound that precipitates titanium oxide by thermal decomposition. 12 paragraphs andA suspension is prepared according to the method described in paragraph 14. An indoor curtain fabric is immersed in the suspension. After lifting the curtain, the curtain is sandwiched between two flat plates larger than the curtain. A compressive load is evenly applied to the upper plate, and the temperature is raised to 310°C, the temperature at which titanium benzoate thermally decomposes. This bonds titanium oxide nanoparticles to both surfaces of the curtain fabric, forming a film less than 0.1 μm thick. Therefore, the curtain fabric carrying the titanium oxide nanoparticles decomposes polymer gases and VOC gases that cause indoor odors. Although the curtain fabric is heated to 310°C, the surface of the curtain fabric is isolated from the atmosphere by the titanium benzoate microcrystals, and the temperature rises to 310°C in an enclosed area, preventing the synthetic resin that makes up the curtain fabric from thermally decomposing. Alternatively, after immersing a plate in the suspension, the plate is sandwiched between two larger plates, a compressive load is evenly applied to the upper plate, and the temperature is raised to 310°C, at which point the titanium benzoate thermally decomposes. This bonds titanium oxide nanoparticles to the plate's surface as a film less than 0.1 μm thick. When this plate is used as an interior material, the titanium oxide nanoparticles decompose polymer gases and VOC gases, which are the source of indoor odors. Fifth, we will explain the catalytic action of vanadium oxide (VO). Vanadium oxide is used as a catalyst for oxidizing sulfur disulfide (SiO) during the production of sulfuric acid by a catalytic process. In an embodiment of the present invention, vanadium naphthenate is used as a metal compound that precipitates vanadium oxide through thermal decomposition. 12 paragraphs and A suspension is prepared according to the method described in paragraph 14. MediumMultiple flat plates are immersed in the desulfurization tower at a distance from each other, and each plate is then removed. Each plate is then sandwiched between two larger plates, a compressive load is applied to the upper plate, and the temperature is raised to 330°C, at which point vanadium naphthenate thermally decomposes. This results in clusters of vanadium oxide nanoparticles being bonded to both surfaces of each plate as a film less than 0.1 μm thick. These multiple plates are fixed at a distance from each other in a desulfurization tower. When exhaust gas passes through the multiple plates, the clusters of vanadium oxide nanoparticles on the surfaces of the plates adsorb sulfur disulfide contained in the exhaust gas, which is then oxidized with oxygen and water in the exhaust gas to form dilute sulfuric acid, which acts as a microreactor device that removes and recovers sulfur dioxide. Sixth, the catalytic action of nickel will be explained. Nickel is used as a catalyst in such steam reforming reactions, for example, when alkenes, nitriles, heavy oils, fats and oils are reacted with steam at about 300°C in the presence of a nickel catalyst to produce a synthesis gas of carbon monoxide gas and hydrogen gas, or a synthesis gas of carbon dioxide gas and hydrogen gas. In an embodiment of the present invention, nickel octoate is used as a metal compound that precipitates nickel by thermal decomposition, 6 paragraphs and 10 paragraphs A suspension is prepared according to the method described in 2. The honeycomb ceramic described above is immersed in this suspension, and then removed from the suspension. The temperature is then raised to 290°C, at which point nickel octoate thermally decomposes. This causes a cluster of nickel nanoparticles to be bonded to the surface of the honeycomb ceramic as a film thinner than 0.1 μm. The honeycomb ceramic is then heated, and finely divided alkenes, nitriles, heavy oils, or fats and oils are passed through the elongated through-holes of the honeycomb ceramic together with high-temperature steam. The honeycomb ceramic then functions as a microreactor device that generates the synthesis gas described above. Seventh, we will explain the catalytic action of cobalt. For example, cobalt can be used in the Fischer-Tropsch synthesis, where a synthesis gas consisting of carbon monoxide and hydrogen is reacted in the presence of a cobalt catalyst to synthesize a liquid fuel consisting of straight-chain hydrocarbons. In an embodiment of the present invention, cobalt octylate is used as a metal compound that precipitates cobalt through thermal decomposition, 6 paragraphs and 10 paragraphsA suspension is prepared according to the method described in 2. Medium The honeycomb ceramic is immersed in the above-mentioned water, then pulled out, and then heated to 290°C, at which point the cobalt octoate thermally decomposes. This bonds a cluster of cobalt nanoparticles to the surface of the honeycomb ceramic as a film less than 0.1 μm thick. When a synthesis gas consisting of carbon monoxide and hydrogen pressurized to 10 atmospheres at 250°C is passed through the elongated through-holes of the honeycomb ceramic, the honeycomb ceramic functions as a microreactor device in which the above-mentioned liquid fuel is synthesized.

[0018] Embodiment 2 Among the metal compounds according to the present invention that precipitate a metal upon thermal decomposition, metal compounds that thermally decompose at relatively low temperatures include inorganic metal compounds having metal complex ions in which ligands composed of inorganic molecules or inorganic ions are coordinately bonded to metal ions, as described in paragraph 9. Here, we will explain an embodiment of a palladium compound that precipitates palladium upon thermal decomposition, which is used in catalysts in various fields, such as catalysts for purifying automobile exhaust gases and catalysts used in synthesizing acetaldehyde from ethylene. In order for a palladium compound to be used as a raw material for precipitating palladium by thermal decomposition, it must possess both the properties of being insoluble in methanol, dispersing in a molecular state in methanol, and precipitating palladium by thermal decomposition. Palladium chloride, palladium sulfate, and palladium nitrate dissolve in methanol, while palladium acetate and palladium bromide do not disperse in a molecular state in methanol. These low-molecular-weight inorganic palladium compounds are not suitable as raw materials for precipitating palladium by thermal decomposition. On the other hand, among the chemical reactions producing palladium from palladium compounds, thermal decomposition is the simplest. In other words, palladium precipitates simply by heating the palladium compound. Furthermore, if the thermal decomposition temperature of the palladium compound is low, the processing temperature for producing catalytic palladium nanoparticles is low, and a film composed of an aggregate of palladium nanoparticles can be formed inexpensively. Among inorganic palladium compounds, inorganic palladium compounds in which inorganic molecules or inorganic ions serve as ligands and have palladium complex ions coordinately bonded to a palladium ion located at the center of the molecular structure have the lowest thermal decomposition temperature in a reducing atmosphere among palladium compounds containing palladium complex ions, due to the small molecular weight of the inorganic material to which the ligands and palladium complex ions are bonded. Furthermore, such inorganic palladium compounds are easier to synthesize than organic palladium compounds, which are compounds of organic acids and palladium, and are therefore the least expensive palladium complex salts. In other words, the palladium ion is the largest molecule in inorganic palladium compounds. The covalent bond radius of the palladium atom is 117 pm, while that of the nitrogen atom is 54 pm, that of the hydrogen atom is 32 pm, and that of the oxygen atom is 63 pm. Therefore, in the molecular structure of inorganic palladium compounds, the distance between the coordinate bond between the ligand and the palladium ion is the longest. Therefore, upon heat treatment in a reducing atmosphere, the coordinate bond is first broken, resulting in decomposition into palladium and the inorganic substance. The low-molecular-weight inorganic substance easily vaporizes, and palladium precipitates immediately thereafter. Among these complexes containing palladium complex ions, there are ammine complexes in which ammonia (NH3) acts as a ligand and is coordinately bonded to the palladium ion, and chloride ions (Cl). - The chloro complex in which Br acts as a ligand and is coordinated to the palladium ion, and the bromide ion Br -In the case of bromo complexes in which the ligands are coordinated to palladium ions, all of the ligands are low molecular weight substances, and inorganic compounds in which these complexes are combined with low molecular weight inorganic substances are easier to synthesize and can be produced at low cost compared to other palladium complex salts. Furthermore, when such inorganic palladium compounds in which palladium complex ions are combined with inorganic substances are heat treated in a reducing atmosphere such as ammonia gas or hydrogen gas, the coordinate bond is first broken, and palladium precipitates at a relatively low temperature of around 200°C. Furthermore, they can be dispersed in methanol to a dispersion concentration of nearly 10% by weight. Such palladium complex salts include the ammine complexes dichlorodiamminepalladium [Pd(NH3)2]Cl2, dibromodiamminepalladium [Pd(NH3)2]Br2, tetraamminepalladium chloride [Pd(NH3)4]Cl2, tetraamminepalladium bromide [Pd(NH3)4]Br2, tetraamminepalladium nitrate [Pd(NH3)4](NO3)2, tetraamminepalladium sulfate [Pd(NH3)4](SO4)2, and tetraamminepalladium acetate [Pd(NH3)4](CH3COO)2; the chloro complexes ammonium tetrachloropalladate (NH4)2[PdCl4] and ammonium hexachloropalladium (NH4)2[PdCl6]; and the bromine complex ammonium tetrabromopalladate (NH4)2[PdBr4]. Inorganic platinum compounds containing platinum complex ions that precipitate platinum upon thermal decomposition include the ammine complexes diammineplatinum chloride [Pt(NH3)2]Cl2, tetraammineplatinum chloride [Pt(NH3)4]Cl2, tetraammineplatinum acetate [Pt(NH3)4](CH3COO)2, tetraammineplatinum sulfate [Pt(NH3)4](SO4)2, and pentaamminechloroplatinum chloride [PtCl(NH3)5]Cl3, as well as the chloro complexes ammonium tetrachloroplatinate (NH4)2 [PtCl4] and diammineplatinum dichloro [PtCl2(NH3)2], and the bromo complex ammonium hexabromoplatinate (NH4)2 [PdBr6]. Because the ligands and inorganic compounds in these platinum complexes are low molecular weight substances, platinum precipitates at relatively low temperatures of around 200°C in a reducing atmosphere. Furthermore, inorganic rhodium compounds containing rhodium complex ions that precipitate rhodium at relatively low temperatures of around 200°C in a reducing atmosphere include ammine complexes such as pentaamminechlororhodium chloride [RhCl(NH3)5]Cl2, hexaamminerhodium chloride [Rh(NH3)6]Cl3, and hexaamminerhodium nitrate [Rh(NH3)6](NO3)3, as well as rhodium complex salts such as the chloro complex ammonium hexachlororhodate (NH4)3[RhCl6]. Furthermore, inorganic ruthenium compounds containing ruthenium complex ions that precipitate ruthenium at relatively low temperatures of around 200°C in a reducing atmosphere include ruthenium salts such as ammine complexes hexaammineruthenium chloride [Ru(NH3)6]Cl3, hexaammineruthenium sulfate [Ru(NH3)6](SO4)3, hexaammineruthenium nitrate [Ru(NH3)6](NO3)3, and chloropentaammineruthenium chloride [Ru(NH3)5Cl]Cl2. Diamine silver chloride [Ag(NH3)2]Cl is an ammine complex, which is an inorganic silver compound containing silver complex ions that precipitate silver, a copper-group metal, at relatively low temperatures of around 200°C in a reducing atmosphere. Tetraamine copper sulfate [Cu(NH3)4]SO4 is an ammine complex, which is an inorganic copper compound containing copper complex ions that precipitate copper upon thermal decomposition. As explained above, the metal compounds that precipitate metals at relatively low heat treatment temperatures in the present invention include inorganic metal compounds having metal complex ions in which ligands consisting of inorganic molecules or inorganic ions are coordinately bonded to metal ions.

[0019] Embodiment 3 The metal compound which precipitates a metal by thermal decomposition in the present invention is a compound which requires a higher heat treatment temperature than the inorganic metal compound having a metal complex ion, but is easy to synthesize and less expensive. 10 There are metal octylate compounds described in paragraph 1. Here, the metal is cobalt, and the description will start with an embodiment of the cobalt compound. In order for a cobalt compound to be used as a raw material for the suspension of the present invention, it must have both the property of dispersing in a molecular state in methanol and the property of precipitating cobalt by thermal decomposition. Cobalt chloride dissolves in methanol, cobalt nitrate dissolves in water, cobalt sulfate dissolves in methanol, and cobalt acetate dissolves in water. For this reason, these low-molecular-weight inorganic cobalt compounds do not disperse in a molecular state in methanol. Inorganic cobalt compounds containing the cobalt complex ions described in paragraph 18 include hexaamminecobalt chloride [Co(NH3)6]Cl3, hexaamminecobalt nitrate [Co(NH3)6](NO3)3, and pentaamminechlorocobalt chloride [CoCl(NH3)5]Cl2. These inorganic cobalt compounds precipitate cobalt at around 200°C in a reducing atmosphere. Next, we will explain organic cobalt compounds. Organic cobalt compounds precipitate cobalt through thermal decomposition. Among the chemical reactions that produce cobalt from organic cobalt compounds, thermal decomposition is the simplest chemical reaction. In other words, cobalt precipitates simply by raising the temperature of the organic cobalt compound. Furthermore, if organic cobalt compounds are easy to synthesize, they can be produced inexpensively. An organic cobalt compound that combines these properties is a cobalt carboxylate compound. In other words, among the ions that make up the cobalt carboxylate compound, the cobalt ion Co, which is located in the center of the molecule, 3+ Therefore, the cobalt ion Co 3+ and oxygen ions O that form the carboxyl group - When covalently bonded to a cobalt ion, Co 3+ and oxygen ions O -The distance between the cobalt ion and the oxygen ion is the longest. This is because the covalent bond radius of the cobalt atom is 103 pm, the cobalt ion's covalent bond radius is 57 pm, and the carbon atom's covalent bond radius is 75 pm. Therefore, in cobalt carboxylate compounds, in which a cobalt ion is covalently bonded to an oxygen ion constituting a carboxyl group, the bond between the cobalt ion and the oxygen ion constituting the carboxyl group, which has the longest bond distance, breaks first at the boiling point of the carboxylic acid, separating the cobalt and the carboxylic acid. If the temperature is further increased, if the carboxylic acid is a saturated fatty acid, the carboxylic acid absorbs the heat of vaporization and vaporizes, and the cobalt precipitates after the carboxylic acid has completely vaporized. Examples of such cobalt carboxylate compounds include cobalt octylate, cobalt laurate, and cobalt stearate. Many of these cobalt carboxylate compounds are inexpensive industrial chemicals commercially available as metal soaps. Cobalt carboxylate compounds are also easy to synthesize. Specifically, when a carboxylic acid is reacted in a strong alkaline solution such as sodium hydroxide, an alkali metal carboxylate compound is produced. When this alkali metal carboxylate compound is reacted with an inorganic cobalt compound such as cobalt chloride, a cobalt carboxylate compound is produced. Furthermore, cobalt carboxylate compounds composed of saturated fatty acids will thermally decompose at low temperatures if the saturated fatty acid has a low boiling point, reducing the cost of the heat treatment required to precipitate cobalt. For saturated fatty acids with long chain structures, the longer the chain, i.e., the higher the molecular weight of the saturated fatty acid, the higher the boiling point of the saturated fatty acid. Incidentally, the boiling point of lauric acid, which has a molecular weight of 200.3, at atmospheric pressure is 296°C, while the boiling point of stearic acid, which has a molecular weight of 284.5, at atmospheric pressure is 361°C. Furthermore, when the saturated fatty acid has a branched chain structure, its chain length is shorter than that of a linear saturated fatty acid, resulting in an even lower boiling point. As a result, cobalt carboxylate compounds made from branched saturated fatty acids undergo thermal decomposition at low temperatures. Furthermore, because branched saturated fatty acids are polar, cobalt carboxylate compounds made from branched saturated fatty acids are also polar and disperse at relatively high rates in polar organic solvents such as methanol. Octylic acid is an example of such a branched saturated fatty acid. Its structural formula is CH3(CH2)3CH(C2H5)COOH, where CH is branched into the alkanes CH3(CH2)3 and C2H5, with the carboxyl group COOH attached to CH. The boiling point of octylic acid at atmospheric pressure is 228°C, 68°C lower than that of lauric acid. Therefore, cobalt octylate, with its low thermal decomposition temperature, is desirable as a raw material for cobalt precipitation. Cobalt octylate undergoes complete thermal decomposition at 290°C in an air atmosphere, resulting in the precipitation of cobalt, which is dispersed in a molecular state in methanol up to 10% by weight.

[0020] Embodiment 4 In the present invention, a suitable metal compound for precipitating a metal oxide by heat treatment is a complex of a metal carboxylate compound in which the oxygen ion constituting the carboxyl group of the carboxylic acid is coordinately bonded to the metal ion, as described in paragraph 15. Here, the metal oxide is titanium oxide (TiO2), and the titanium compound will be described first. In order for a titanium compound to be used as a raw material for the suspension of the present invention, it must possess both the property of dispersing in a molecular state in methanol and the property of precipitating titanium oxide through thermal decomposition. Titanium chloride reacts with methanol. Titanium oxide does not disperse in methanol. Therefore, these low-molecular-weight inorganic titanium compounds do not disperse in a molecular state in methanol. In addition, the titanium complex ion [TiCl4O] explained in paragraph 18 2- However, the coordinate bond is not stable, so titanium does not precipitate during thermal decomposition. Next, we will explain about organotitanium compounds. Organotitanium compounds must have the property of precipitating titanium dioxide (TiO2) through thermal decomposition. Of the chemical reactions by which titanium oxide is produced from organotitanium compounds, the simplest is the thermal decomposition reaction. In other words, simply by raising the temperature of the organotitanium compound, titanium oxide precipitates through thermal decomposition. Furthermore, if organotitanium compounds are easy to synthesize, they can be produced inexpensively. An organotitanium compound that combines these properties is a titanium carboxylate compound. In other words, as explained in paragraph 19, among the substances that make up titanium carboxylate compounds, the substance with the largest covalent bond radius is the titanium ion Ti 4+ On the other hand, titanium ions Ti 4+ and oxygen ions O that form the carboxyl group - In titanium carboxylate compounds in which titanium ions are covalently bonded, the distance between the titanium ion and the oxygen ion is maximized, and titanium is precipitated by thermal decomposition as explained in paragraph 19. Therefore, titanium carboxylate compounds that precipitate titanium oxide by thermal decomposition are those in which the titanium ion Ti 4+ Oxygen ions O - approaches to form a coordinate bond, and oxygen ions O - is titanium ion Ti 4+ The bond distance with the ion bonded on the other side must be the longest. In other words, oxygen ion O - is titanium ion Ti 4+ Since the bond with the ion on the other side of the titanium ion is the longest, this bond is first broken and the titanium ion decomposes into an oxygen ion bonded to the titanium ion, i.e., titanium oxide TiO2, and a carboxylic acid. Titanium carboxylate compounds with such molecular structure characteristics include the oxygen ion O that constitutes the carboxyl group. - is the ligand and forms the titanium ion Ti 4+ There are titanium carboxylate compounds that approach and form coordinate bonds with the Furthermore, among organic titanium compounds, titanium carboxylate compounds are easy to synthesize, as explained in paragraph 19, and have a relatively low thermal decomposition temperature if the boiling point of the organic acid is low. Therefore, complexes made from metal carboxylate compounds in which the oxygen ions that make up the carboxyl group act as ligands and approach metal ions to form coordinate bonds are inexpensive industrial chemicals, and the heat treatment costs are also low. Therefore, titanium carboxylate compounds in which the oxygen ions that make up the carboxyl group are coordinately bonded to titanium ions are inexpensive industrial chemicals that precipitate titanium oxide upon thermal decomposition. Examples of such titanium carboxylate compounds include titanium acetate, titanium caprylate, titanium benzoate, and titanium naphthenate. However, titanium carboxylate compounds, except for titanium benzoate, do not precipitate titanium oxide upon thermal decomposition because their coordinate bonds are unstable. Because the boiling point of benzoic acid is 249°C, titanium benzoate will thermally decompose at 310°C in the air and precipitate titanium oxide. On the other hand, among vanadium carboxylate compounds, except for vanadium naphthenate, their coordinate bonds are unstable and therefore will not precipitate vanadium oxide upon thermal decomposition. Meanwhile, naphthenic acid is a mixture of saturated fatty acids with a five-membered ring, and has the general formula C n H 2n-1 COOH, the boiling point of the main component is 268°C, and the molecular weight is 170. 17 Vanadium naphthenate is composed of COOH. Therefore, it thermally decomposes at 330°C in the air, and vanadium oxide precipitates. A carboxylic acid metal compound in which the oxygen ions constituting the carboxyl group of a carboxylic acid function as ligands and are coordinately bonded to a metal ion is a complex made of an organic metal compound. On the other hand, the complex described in paragraph 18 is a complex made of an inorganic metal compound in which inorganic molecules or inorganic ions function as ligands and have a metal complex ion that is coordinately bonded to a metal ion. Furthermore, because the inorganic substance that bonds to the ligand and the metal complex ion has a smaller molecular weight than the carboxylic acid, the thermal decomposition temperature of the complex made of an inorganic metal compound is lower than that of a carboxylic acid metal compound. The liquid organic compound used as the raw material for the suspension in the present invention is an organic compound that combines the three properties described in paragraph 6, and includes a chain saturated hydrocarbon having 9 to 11 carbon atoms described in paragraph 9. Examples of such a chain saturated hydrocarbon include nonane CH3(CH2)7CH3, decane CH3(CH2)8CH3, and undecane CH3(CH2)9CH3, as described in paragraph 9.

[0021] Example 1 In this example, 105 g (equivalent to 0.5 moles) of diaminedichloropalladium (a product of Tokuriki Honten Co., Ltd.) was dispersed in methanol at a concentration of 10 wt %. The methanol was then evaporated, precipitating diaminedichloropalladium crystals. The diaminedichloropalladium crystals were placed in a shallow container, and a flat plate covering the entire crystal cluster was placed over the cluster. Nine 2 kg weights were then placed at equal intervals on the plate's surface. The weights were then removed from the plate's surface, and the container was secured to the vibrator's vibration table. An impact acceleration of 0.3 G was applied to the container in three directions: up / down, front / back, and left / right. This pair of processes, consisting of placing the weights and applying the impact acceleration, was repeated three times. Furthermore, 100 cc of decane (a product of Fujifilm Wako Pure Chemical Industries, Ltd.) was added to the crushed crystal mass in the container, and the decane was stirred to prepare a first suspension. The density of diaminedichloropalladium was 2.5 g / cm. 3 Therefore, 100g of diaminedichloropalladium has 42cm 3 The volume is equivalent to

[0022] Example 2 In this example, 93 g (equivalent to 0.3 moles) of hexaammineruthenium chloride (a product of Fujifilm Wako Pure Chemical Industries, Ltd.) was dispersed in methanol at a concentration of 10 wt %, after which the methanol was evaporated to precipitate hexaammineruthenium chloride crystals. As in Example 1, the collection of crystals was spread in a shallow container, and a pair of treatments consisting of placing a weight on the container and applying impact acceleration were repeated three times. Furthermore, 90 cc of decane was added to the collection of crushed crystals in the container, and the decane was stirred to prepare a second suspension.

[0023] Example 3 In this example, 90 g (equivalent to 0.3 moles) of diamine platinum chloride (a product of Mitsuwa Chemical Co., Ltd.) was dispersed in methanol at a concentration of 10 wt %. The methanol was then evaporated to precipitate diamine platinum chloride crystals. As in Example 1, the collected crystals were placed in a shallow container, and a pair of treatments consisting of placing a weight on the container and applying impact acceleration were repeated three times. Furthermore, 90 cc of decane was added to the crushed collected crystals in the container, and the decane was stirred to prepare a third suspension.

[0024] Example 4 In this example, 93 g (equivalent to 0.3 moles) of hexaamminerhodium chloride (a product of Mitsuwa Chemical Co., Ltd.) was dispersed in methanol at a concentration of 10 wt %, and then the methanol was evaporated to precipitate hexaamminerhodium chloride crystals. As in Example 1, the cluster of crystals was spread in a shallow container, and a pair of treatments consisting of placing a weight on the cluster and applying impact acceleration were repeated three times. Furthermore, 90 cc of decane was added to the cluster of crushed crystals in the container, and the decane was stirred to prepare a fourth suspension.

[0025] Example 5 In this example, 90 g (equivalent to 0.5 moles) of diamine silver chloride (a product of Tanaka Kikinzoku Kogyo Co., Ltd.) was dispersed in methanol at a concentration of 10 wt %. The methanol was then evaporated to precipitate diamine silver chloride crystals. As in Example 1, the cluster of crystals was placed in a shallow container, and a pair of treatments consisting of placing a weight on the cluster and applying impact acceleration were repeated three times. Furthermore, 90 cc of decane was added to the cluster of crushed crystals in the container, and the decane was stirred to prepare a fifth suspension.

[0026] Example 6 In this example, 100 g (equivalent to 0.4 moles) of tetraammine copper dinitrate (a product of Wako Pure Chemical Industries, Ltd.) was dispersed in methanol at a concentration of 10 wt %. The methanol was then evaporated to precipitate tetraammine copper dinitrate crystals. As in Example 1, the collected crystals were placed in a shallow container, and a pair of treatments consisting of placing a weight on the container and applying impact acceleration were repeated three times. Furthermore, 100 cc of decane was added to the crushed collected crystals in the container, and the decane was stirred to prepare a sixth suspension.

[0027] Example 7 In this example, 106 g (equivalent to 0.2 moles) of titanium tetrabenzoate (a product of Mitsuwa Chemical Co., Ltd.) was dispersed in methanol at a concentration of 10 wt %. The methanol was then evaporated to precipitate titanium tetrabenzoate crystals. As in Example 1, the collected crystals were placed in a shallow container, and a pair of treatments consisting of placing a weight on the container and applying impact acceleration were repeated three times. Furthermore, 100 cc of decane was added to the crushed crystals in the container, and the decane was stirred to prepare a seventh suspension.

[0028] Example 8 In this example, 111 g (equivalent to 0.15 moles) of vanadium naphthenate (a product of Kishida Chemical Co., Ltd.) was dispersed in methanol at a concentration of 10 wt %. The methanol was then evaporated to precipitate vanadium naphthenate crystals. As in Example 1, the cluster of crystals was placed in a shallow container, and a pair of treatments consisting of placing a weight on the cluster and applying impact acceleration were repeated three times. Furthermore, 110 cc of decane was added to the cluster of crushed crystals in the container, and the decane was stirred to prepare an eighth suspension.

[0029] Example 9 In this example, synthetic resin, one of the most commonly used substrates, is used as the substrate. A thin flat plate of synthetic resin is immersed in each of the suspensions prepared in Examples 1-8. After that, each of the metal compounds used in Examples 1-8 is thermally decomposed, and the granular nanoparticles of metal or metal oxide, each about 10 nm in size, precipitated by the thermal decomposition of the metal compound are joined together by metallic bonding or friction welding. A film consisting of a collection of metallically bonded nanoparticles, or a film consisting of a collection of metal oxide nanoparticles joined by friction welding, is bonded to both surfaces of the flat plate of synthetic resin. Among the metal compounds used in Examples 1-8, the metal compound with the highest thermal decomposition temperature was vanadium naphthenate used in Example 8, which completed its thermal decomposition in the air at 330°C, precipitating vanadium oxide VO. Meanwhile, the onset temperatures of thermal decomposition in the air at which synthetic resins begin to change in weight are, for example, 230°C for polyvinyl alcohol resin, 250°C for polyvinyl chloride resin, 300°C for acrylic resin, 300°C for triacetate resin, 320°C for polystyrene resin, 380°C for polypropylene resin, 400°C for low-density polyethylene resin, 440°C for polyethylene terephthalate (PET) resin, 480°C for polyethersulfone (PES) resin, 480°C for polytetrafluoroethylene (PTFE) resin, and 500°C for polycarbonate resin. Thermal decomposition is an irreversible reaction, and once thermal decomposition begins, the polymeric material undergoes irreversible changes and cannot be restored to its original state. The thermal decomposition of synthetic resins, a polymeric material, differs significantly between oxygen and nitrogen atmospheres. Specifically, thermal decomposition in oxygen atmospheres involves heat generation due to oxidation. This heat generation accelerates the thermal decomposition of polymers made of easily oxidized organic substances, and the flammable gases produced during the thermal decomposition process can self-ignite. In contrast, thermal decomposition in nitrogen atmospheres does not involve oxidation, but occurs via endothermic reactions, resulting in no heat generation. Therefore, the temperature at which polymers begin to decompose is significantly delayed and shifted to a higher temperature compared to oxygen atmospheres. For example, the thermal decomposition of high-density polyethylene resin begins at approximately 250°C in air, but shifts to approximately 400°C in nitrogen atmospheres, a temperature shift of 150°C higher. The onset and end temperatures of thermal decomposition of synthetic resins in a nitrogen atmosphere are as follows: Polyacetal resin (POM) begins at 280°C and ends at 420°C. Polystyrene resin (PS) begins at 350°C and ends around 460°C. Polyethylene terephthalate resin (PET) begins at 425°C and ends around 480°C. Polypropylene resin (PP) begins at 370°C and ends around 500°C. High-density polyethylene resin (HDPE) begins at 400°C and ends around 520°C. Polytetrafluoroethylene resin (PTFE) begins at 490°C and ends around 640°C. In addition, polyvinyl chloride resin (PVC) releases non-flammable but harmful hydrogen chloride gas (HCl) in an endothermic reaction that begins at around 220°C, progresses rapidly around 260°C, and continues up to 360°C. After this, endothermic thermal decomposition of the polymer begins at around 420°C, producing benzene with an ignition point of 498°C, and the process ends at around 550°C, leaving behind 10% solid residue (ash).The thermal decomposition reaction of novolac phenolic resin begins with the elimination of plasticizer at around 260°C and continues until around 360°C, after which endothermic thermal decomposition of the polymer begins at 390°C, producing liquid monomers such as phenol with an ignition point of 715°C and cresol with an ignition point of 626°C, and the process ends at around 700°C, leaving behind 65% solid residue (ash). Therefore, even when PP resin, HDPE resin, or PTFE resin is heated in a nitrogen atmosphere, the resin undergoes thermal decomposition to produce hydrocarbon gases such as propane, ethane, and toluene. If these flammable gases are transferred to the atmosphere and heated above their ignition point, they will self-ignite and become the starting point for a fire. Furthermore, PVC resin produces benzene through thermal decomposition, and if the resin is transferred to the atmosphere and heated above 498°C, the benzene will self-ignite. Furthermore, novolac phenolic resin produces cresol through thermal decomposition, and if the resin is transferred to the atmosphere and heated above 626°C, the cresol will self-ignite. In contrast, the substrate of the present invention is covered with an airtight coating made of laminated microcrystals of the metal compound, each about 20 nm in size, before the metal compound begins to thermally decompose. Therefore, the thermal decomposition of polymers made of synthetic resins differs from that in a nitrogen atmosphere. That is, because the nitrogen atmosphere is an open atmosphere, the flammable gases generated by the thermal decomposition gradually vaporize into the nitrogen atmosphere. As the temperature rises, the thermal decomposition, which sequentially generates flammable gases, progresses, and the flammable gases are gradually released into the nitrogen atmosphere. In contrast, in the polymer material covered with an airtight coating made of laminated microcrystals of the present invention, when the thermal decomposition of the metal compound begins, the metal compound decomposes into inorganic or organic molecules and metal or metal oxide molecules. Immediately after the inorganic or organic molecules are completely vaporized, the metal or metal oxide molecules aggregate, depositing a cluster of granular metal or metal oxide nanoparticles about 10 nm in size. Therefore, polymeric materials are covered with aggregates of inorganic or organic molecules and aggregates of metal or metal oxide molecules, and then with aggregates of granular metal or metal oxide nanoparticles, continuously insulating them from the outside world. Therefore, when a polymeric material begins to pyrolyze, the first gas produced by pyrolysis is confined within an extremely narrow region on the surface of the polymeric material, where its partial pressure increases until it reaches saturation pressure at that temperature, at which point pyrolysis ceases. Therefore, to proceed with pyrolysis, more thermal energy must be applied to the polymer than pyrolysis in an open atmosphere. Furthermore, one mole of gas produced occupies a volume of 22.4 liters. Therefore, once a very small amount of flammable gas is produced, the partial pressure within the narrow region reaches saturation pressure at that temperature, resulting in a much smaller amount of gas produced than in a nitrogen gas atmosphere. Furthermore, because the initial gas is confined, the second and subsequent gases produced by pyrolysis require even greater thermal energy to proceed. As a result, the synthetic resin covered with the airtight coating of the present invention, in which the microcrystals are laminated, undergoes a thermal decomposition reaction at a temperature significantly higher than the thermal decomposition temperature in a nitrogen atmosphere.Therefore, the substrate made of synthetic resin in the present invention does not undergo thermal decomposition, and the physical properties of the synthetic resin remain almost the same as before the temperature rise. In this example, polyacetal resin, one of the most commonly used thermoplastic synthetic resins, was used as a representative synthetic resin. A 1 mm thick, 10 cm x 10 cm plate made of polyacetal resin was immersed in each of the suspensions prepared in Examples 1-8. Furthermore, the samples immersed in the suspensions of Examples 1, 3, and 5 were heated to 180°C in an ammonia atmosphere. The samples immersed in the suspensions of Examples 2 and 4 were heated to 220°C in a hydrogen atmosphere. The sample immersed in the suspension of Example 6 was heated to 200°C in an ammonia atmosphere. After being left at each temperature for 5 minutes, they were cooled to room temperature. The sample immersed in the suspension of Example 7 was heated to 310°C in air. The sample immersed in the suspension of Example 8 was heated to 330°C in air. After being left at each temperature for 1 minute, they were cooled to room temperature. The substrates thus immersed in the suspensions of Examples 1-8 were further heat-treated to prepare Samples 1-8. First, for samples 1-8, the bonding strength between the film formed on the sample surface and the plate material was measured based on the adhesive strength test method specified in JIS Z0237. Samples 1-6 withstood a load of 800 g, and samples 7 and 8 withstood a load of 1000 g. This shows that the film formed on the plate material does not peel off even under the various physical stresses applied when it functions as a catalyst, and remains bonded to the plate material for a long period of time. Next, the surface of Sample 1-8 and a cross section cut at the center of Sample 1-8 were observed using an electron microscope. An ultra-low accelerating voltage SEM owned by JFE Techno-Research Corporation was used as the electron microscope. This equipment allows surface observation at ultra-low accelerating voltages starting from 100 volts, and allows direct surface observation without forming a conductive coating. First, secondary electron beams between 900 and 1000 volts were extracted from the reflected electron beams from the surfaces of specimens 1 to 8 and image processing was performed. The surfaces of specimens 1 to 8 were all formed by an aggregation of granular particles with a size of about 10 nm, and more than 50% of the surface of each particle was directly exposed to the outside world, with the granular particles bonding together at the contact points. Next, the energy between 900-1000 volts of the electron beam reflected from the surface of sample 1-8 was extracted and image processing was performed, and differences in material were observed based on the shade of the image. Sample 1-6 was composed of the same atoms, as no shade was observed. Samples 7 and 8 were composed of multiple atoms, as shades were observed. Furthermore, the energy and intensity of characteristic X-rays from the surface of samples 1-8 were image-processed to analyze the type and distribution of elements that make up the granular microparticles. Palladium atoms were present in sample 1, ruthenium atoms in sample 2, platinum atoms in sample 3, rhodium atoms in sample 4, silver atoms in sample 5, and copper atoms in sample 6, all of which were evenly distributed, with no particularly unevenly distributed areas observed. Titanium atoms and oxygen atoms were present in close proximity to each other in sample 7, with the two types of atoms not unevenly distributed. Furthermore, vanadium atoms and oxygen atoms were present in close proximity to each other in sample 8, with the two types of atoms not unevenly distributed. Therefore, samples 1-6 are granular metal microparticles approximately 10 nm in size, consisting of a single metal. Next, EBSP analysis was added to the ultra-low accelerating voltage SEM function to analyze the crystal structure of Samples 7 and 8. As a result, titanium oxide (TiO2) was formed in Sample 7, and vanadium oxide in Sample 8. Therefore, Sample 7 is made up of granular fine particles of titanium oxide with a size of approximately 10 nm, while Sample 8 is made up of granular fine particles of vanadium oxide (V2O5) with a size of approximately 10 nm. Furthermore, secondary electron beams between 900-1000 volts were extracted from the reflected electron beams from the cross-sections of Samples 1-8 and image processing was performed. The cross-sections of Samples 1-8 all showed granular particles approximately 10 nm in size filling in the unevenness of the substrate surface, and a film consisting of a collection of approximately five granular particles stacked together and joined together was composed of a film with a thickness of approximately 50 nm. This film consisting of a collection of particles is represented by the film made of palladium particles in Sample 1, and is schematically illustrated in Figure 1. 1 is a polyacetal resin plate and 2 are palladium particles. From the above results, both surfaces of sample 1 exhibit catalytic action for palladium microparticles. Both surfaces of sample 2 exhibit catalytic action for ruthenium microparticles. Both surfaces of sample 3 exhibit catalytic action for platinum microparticles. Both surfaces of sample 4 exhibit catalytic action for rhodium microparticles. Both surfaces of sample 5 exhibit catalytic action for silver microparticles. Both surfaces of sample 6 exhibit catalytic action for copper microparticles. Both surfaces of sample 7 exhibit catalytic action for titanium oxide microparticles. Both surfaces of sample 8 exhibit catalytic action for vanadium oxide microparticles.

[0030] Example 10 This example relates to the embodiment in which catalytic action is simultaneously exerted by an assembly of nanoparticles of three types of metals consisting of palladium, platinum, and rhodium, which was first explained in the first embodiment in paragraph 17. A honeycomb ceramic was used as the substrate, and the honeycomb ceramic was immersed in Suspension 2, Suspension 1, and Suspension 3 to successively shallower depths, allowing each suspension to be adsorbed onto the surface of the honeycomb ceramic. The temperature was then raised to the temperature at which the metal compounds thermally decompose, forming a film of nanoparticles of three different metals bonded to each other on the surface of three different internal through-holes. The honeycomb ceramic used was a catalyst carrier ceramic (Honeyceram, a product of NGK Insulators, Ltd.) used in three-way catalytic converters for automobiles. This Honeyceram has a cell wall thickness of 6 mils (1 mil is 1 / 1000 of an inch) and 400 cells per square inch. First, the entire honeycomb ceramic is immersed in a container filled with suspension 2. After leaving it at room temperature for 5 minutes, the honeycomb ceramic immersed in suspension 2 is placed in a container filled with suspension 1, and suspension 1 is allowed to adsorb to 1 / 3 of the height of the honeycomb ceramic, which is the height at which suspension 2 is not adsorbed on the surface of the honeycomb ceramic. After leaving it at room temperature for 5 minutes, the honeycomb ceramic immersed in suspension 1 is immersed in a container filled with suspension 3, and suspension 3 is allowed to adsorb to 1 / 3 of the height of the honeycomb ceramic, which is the height at which suspension 1 is not adsorbed on the surface of the honeycomb ceramic. Thereafter, the honeycomb ceramic is heated to 200°C in an ammonia atmosphere, left for 5 minutes, and then cooled to room temperature to prepare sample 9. Next, Sample 9 was cut vertically into sections at the areas where only Suspension 2 was adsorbed, the areas where Suspension 1 was adsorbed on Suspension 2, and the areas where Suspension 3 was adsorbed on Suspension 1, and the inner walls of the cells at each cut surface were observed by SEM in the same manner as in Example 9. On the inner wall of the cell where only suspension 2 was adsorbed, a first film was formed, consisting of a collection of approximately five ruthenium nanoparticles, each approximately 10 nm in size, stacked and bonded together. On the inner wall of the cell where suspension 1 was adsorbed on suspension 2, a second film was formed, consisting of a collection of approximately five palladium nanoparticles, each approximately 10 nm in size, stacked and bonded together. On the inner wall of the cell where suspension 3 was adsorbed on suspension 1, a third film was formed, consisting of a collection of approximately five platinum nanoparticles, each approximately 10 nm in size, stacked and bonded together, on the first and second films. More than 50% of the film surface was directly exposed to the outside world for each nanoparticle, and the nanoparticles were bonded together at the contact points. Figure 2 shows a schematic cross-section of three films stacked and bonded together. 3 is the cell surface, 4 is the first film, 5 is the second film, and 6 is the third film. From the above results, it was found that the through-holes inside the honeycomb ceramic consisted of areas that exhibited the catalytic action of ruthenium, areas that exhibited the catalytic action of palladium, and areas that exhibited the catalytic action of platinum, and films that exhibited different catalytic actions were formed in three different locations.

[0031] The above-described examples are merely a partial list of examples of the present invention. That is, the inorganic metal compounds of Examples 1-6 are merely examples of inorganic metal compounds containing metal complex ions that precipitate catalytic metals by thermal decomposition. Similarly, the inorganic metal compounds of Examples 7 and 8 are merely examples of titanium tetrabenzoate or vanadium naphthenate that precipitate catalytic metal oxides by thermal decomposition. Although not shown in the examples, it is easy to prepare a suspension using copper octylate, nickel octylate, or cobalt octylate, and by thermally decomposing copper octylate, nickel octylate, or cobalt octylate, a film can be formed from copper nanoparticles, nickel nanoparticles, or cobalt nanoparticles. Furthermore, the substrates onto which the suspension is adsorbed are not limited to the synthetic resin plates and honeycomb ceramics shown in the examples. Substrates or parts processed into various shapes and structures, such as honeycombs made of metal foil or alloy foil, planar filters, and porous filters, can also be made to adsorb the suspension simply by immersing them in the suspension. When the substrate or part is heated to a temperature at which the metal compound thermally decomposes, a catalytic film is formed on the substrate or part. Therefore, according to the present invention, the surface of a film consisting of a collection of metal nanoparticles bonded by metallurgy, or the surface of a film consisting of a collection of metal oxide nanoparticles joined by friction welding, is made up of granular nanoparticles with a size of around 10 nm bonded or joined together, so that more than 50% of the surface of the nanoparticles is directly exposed to the outside world, and the film can efficiently exhibit the inherent catalytic action based on the material that makes up the nanoparticles. [Explanation of symbols]

[0032] 1 Polyacetal resin plate 2 Palladium nanoparticles 3 Honeycomb ceramic cell 4 First film 5 Second film 6 Third film

Claims

1. A method for forming a film on both surfaces of a substrate, the film being made of a collection of catalytic metal nanoparticles, is bonded to both surfaces of the substrate, so that the surfaces of the metal nanoparticles on the surface of the film are directly exposed to the outside world, and the film acts as a film that exhibits catalytic action, comprising the steps of: A metal compound having a first property of being dispersed in methanol in a molecular state but not being dissolved in methanol, and a second property of precipitating a metal having catalytic activity upon thermal decomposition, is dispersed in methanol in a molecular state to prepare a methanol dispersion of the metal compound, then methanol is evaporated from the methanol dispersion of the metal compound to precipitate a cluster of crystals of the metal compound, then the cluster of crystals of the metal compound is filled into a container, and a flat plate that covers the entire surface of the cluster of crystals of the metal compound is placed on top of the cluster of crystals of the metal compound, then a compressive load is applied evenly to the entire surface of the flat plate to crush the crystals of the metal compound in the container, and then the container is pressed in three directions, i.e., front-back, left-right, and up-down. a first step in which impact acceleration is repeatedly applied to rearrange the cluster of crushed crystals of the metal compound in the container, after which the compressive load is applied evenly to the entire surface of the plate again to further crush the crystals of the metal compound, and the three-directional impact acceleration is again repeatedly applied to the container; the pair of processes consisting of the process of applying the compressive load and the process of applying the impact acceleration are repeated, and when the crystals of the metal compound can be made finer, applying a compressive load to the plate will not crush the crystals, and a repulsive force will be generated from the plate; therefore, the pair of processes is stopped at the point in time when the repulsive force is generated, and a cluster of fine crystals of the metal compound is created in the container; a second step of removing the plate from the container, and then converting into weight an amount of a liquid organic compound having a volume greater than the volume occupied by the cluster of fine crystals in the container, the liquid organic compound having a first property of having a viscosity of 0.7-0.9 mPa·sec at 20°C, a second property of the crystals of the metal compound being dissolved and not dispersed in a molecular state, and a third property of having a boiling point lower than the thermal decomposition temperature of the metal compound, the organic compound having a volume greater than the volume occupied by the cluster of fine crystals in the container, the organic compound having the converted weight, mixing the weighed organic compound into the container, and stirring the organic compound to prepare a suspension in which the cluster of fine crystals of the metal compound is dispersed in the organic compound; The entire substrate to which the clusters of metal nanoparticles are bonded is immersed in the suspension in the container, and then the substrate is removed from the suspension and moved into a heat treatment device that thermally decomposes the metal compound. The substrate is heated to a temperature at which the metal compound is thermally decomposed. As a result, first the organic compound is vaporized, and then the microcrystals are thermally decomposed. At this time, clusters of metal nanoparticles having catalytic action are simultaneously precipitated on both surfaces of the substrate and on the irregularities on both surfaces, and the clusters of metal nanoparticles are stacked. Then, the stacked clusters of metal nanoparticles are a third step in which the nanoparticles are metallically bonded to each other at contact sites, and a group of metallically bonded metal nanoparticles fills in the irregularities on both surfaces of the substrate and covers both surfaces of the substrate; and a group of some of the metal nanoparticles that have filled in the irregularities on both surfaces of the substrate come into contact with a group of some of the metal nanoparticles that have covered both surfaces of the substrate, and the contacting nanoparticles are metallically bonded to each other at contact sites, so that the group of metallically bonded metal nanoparticles is bonded to both surfaces of the substrate as a film having a thickness of less than 0.1 μm; A method for continuously carrying out all of the above-mentioned three steps involves bonding a film consisting of a collection of catalytic metal nanoparticles to both surfaces of a substrate, so that the surfaces of the metal nanoparticles on the surface of the film are directly exposed to the outside world, and the film acts as a film that exhibits catalytic activity, forming the film on both surfaces of the substrate.

2. The method for forming a film consisting of an assembly of catalytic metal nanoparticles on both surfaces of a substrate according to claim 1 comprises the steps of: A method for forming a film consisting of an aggregation of catalytic metal nanoparticles on both surfaces of a substrate, the method comprising: using the metal compound that precipitates a metal by thermal decomposition as set forth in claim 1, which is an inorganic metal compound composed of an inorganic salt having a metal complex ion in which an inorganic molecule or an inorganic ion acts as a ligand and is coordinately bonded to a metal ion; and using the organic compound as set forth in claim 1, which is a chain saturated hydrocarbon having 9 to 11 carbon atoms; and using the inorganic metal compound as the metal compound that precipitates a metal by thermal decomposition as set forth in claim 1, and using the chain saturated hydrocarbon as the organic compound as set forth in claim 1, and forming a film consisting of an aggregation of catalytic metal nanoparticles on both surfaces of a substrate according to the method set forth in claim 1.

3. The method for forming a film consisting of an assembly of catalytic metal nanoparticles on both surfaces of a substrate according to claim 1 comprises the steps of: A method for forming a film composed of an aggregation of catalytic metal nanoparticles on both surfaces of a substrate, the method comprising: using the metal compound that precipitates a metal upon thermal decomposition as set forth in claim 1 as a metal octylate compound; and using the organic compound as set forth in claim 1 as a chain saturated hydrocarbon having 9 to 11 carbon atoms; and using the metal octylate compound as the metal compound that precipitates a metal upon thermal decomposition as set forth in claim 1; and using the chain saturated hydrocarbon as the organic compound as set forth in claim 1; and forming a film composed of an aggregation of catalytic metal nanoparticles on both surfaces of a substrate according to the method set forth in claim 1.

4. A method for forming a film on both surfaces of a substrate, the film being made of an aggregate of catalytic metal oxide nanoparticles, is bonded to both surfaces of the substrate, so that the surfaces of the metal oxide nanoparticles on the surface of the film are directly exposed to the outside world, and the film acts as a film that exhibits catalytic activity, comprising the steps of: A metal compound having a first property of being dispersed in methanol in a molecular state but not being dissolved in methanol, and a second property of precipitating a metal oxide having catalytic activity upon thermal decomposition, is dispersed in methanol in a molecular state to prepare a methanol dispersion of the metal compound, then methanol is evaporated from the methanol dispersion of the metal compound to precipitate a cluster of crystals of the metal compound, then the cluster of crystals of the metal compound is filled into a container, and a flat plate that covers the entire surface of the cluster of crystals of the metal compound is placed on top of the cluster of crystals of the metal compound, then a compressive load is evenly applied to the entire surface of the flat plate to crush the crystals of the metal compound in the container, and then the container is pressed against the container in three directions, i.e., front-back, left-right, and up-down. and then applying the impact acceleration in three directions to the container repeatedly, thereby rearranging the cluster of crushed crystals of the metal compound in the container; thereafter, applying the compressive load evenly to the entire surface of the plate again to further crush the crystals of the metal compound; and then repeatedly applying the impact acceleration in three directions to the container again; and when the limit of the reduction in the crystal size of the metal compound is reached, applying the compressive load to the plate will not crush the crystals, and a repulsive force will be generated from the plate; therefore, at the point when the repulsive force is generated, the pair of processes will be stopped, and a cluster of fine crystals of the metal compound will be created in the container; a second step of converting a volume of the liquid organic compound that is greater than the volume occupied by the cluster of fine crystals in the container into a weight, measuring the organic compound having the converted weight, mixing the weighed organic compound into the container, and stirring the organic compound to prepare a suspension in which the cluster of fine crystals is dispersed in the organic compound, the liquid organic compound having a first property of having a viscosity of 0.7-0.9 mPa·sec at 20°C, a second property of the crystals of the metal compound being dissolved and not dispersed in a molecular state, and a third property of having a boiling point lower than the thermal decomposition temperature of the metal compound; A substrate consisting of a flat plate to which clusters of metal oxide nanoparticles are bonded is immersed in its entirety in the suspension in the container, and then the substrate is removed from the suspension and the entire substrate is sandwiched between two flat plates of the same shape but larger than the substrate. The substrate sandwiched between the two flat plates is then moved into a heat treatment device for thermally decomposing the metal compound, and the entire surface of one of the two flat plates is uniformly compressed and heated to a temperature at which the metal compound is thermally decomposed. As a result, first the organic compound is vaporized, and then the fine crystals are thermally decomposed. At this time, clusters of catalytic metal oxide nanoparticles are precipitated simultaneously on both surfaces of the substrate and on the irregularities on both surfaces, forming nanoparticles of the metal oxide. a third step in which the particle clusters are stacked, a compressive stress is applied to the stacked clusters of metal oxide nanoparticles, and the nanoparticles are joined by friction welding at the contact points, and the joined clusters of metal oxide nanoparticles fill in the irregularities on both surfaces of the substrate and cover both surfaces of the substrate, and further, a portion of the clusters of metal oxide nanoparticles that have filled in the irregularities on both surfaces of the substrate come into contact with a portion of the clusters of metal oxide nanoparticles that have covered both surfaces of the substrate, and the contacting nanoparticles are joined by friction heat at the contact points, and as a result, the clusters of metal oxide nanoparticles joined by friction welding are joined to both surfaces of the substrate as a film having a thickness of less than 0.1 μm; A method for continuously carrying out all of the above-mentioned three steps involves bonding a film consisting of a collection of catalytic metal oxide nanoparticles to both surfaces of a substrate, so that the surfaces of the metal oxide nanoparticles on the surface of the film are directly exposed to the outside world, and the film acts as a film that exhibits catalytic activity, forming the film on both surfaces of the substrate.

5. The method for forming a film consisting of an assembly of catalytic metal oxide nanoparticles on both surfaces of a substrate according to claim 4 comprises the steps of: A method for forming a film composed of an aggregation of catalytic metal oxide nanoparticles on both surfaces of a substrate, the method comprising: using a complex composed of a metal carboxylic acid compound as the metal compound that precipitates a metal oxide by thermal decomposition according to claim 4, in which an oxygen ion constituting a carboxyl group of the carboxylic acid is coordinately bonded to a metal ion; and using a chain saturated hydrocarbon as the organic compound according to claim 4; and forming a film composed of an aggregation of catalytic metal oxide nanoparticles on both surfaces of a substrate according to the method according to claim 4.

Images