METHOD FOR PRODUCING METAL CARBIDE, METAL CARBIDE POWDER, AND METAL CARBIDE INTERMEDIATE DISPERSION

Abstract

To provide a method for producing a metal carbide that is extremely fine but has high fluidity, and a metal carbide powder.SOLUTION: A method of the present invention for producing a metal carbide in powder form using a complexation polymerization method includes: a complexing step of mixing metal hydroxide and alkaline compound to produce a first mixed solution, adding hydrogen peroxide to the first mixed solution to produce a second mixed solution, and then adding an organic acid to the second mixed solution to produce a metal carbide precursor; a carbonizing step of calcining the metal carbide precursor to produce a metal carbide; and a powdering step of crushing the metal carbide to form a metal carbide powder. The metal carbide powder of the present invention has a specific surface area of 1 m2 / g or more by the BET method, and a roundness of 0.78 or greater. A metal carbide intermediate dispersion liquid of the present invention has: a metal compound; an alkaline compound; hydrogen peroxide; and an organic acid. A particle size (D50) of the particles in the metal carbide intermediate dispersion liquid, as measured by particle size distribution measurement using dynamic light scattering, is 1000 nm or smaller.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a metal carbide, a metal carbide powder, and a metal carbide intermediate dispersion. [Background technology]

[0002] Metal carbides such as tantalum carbide and niobium carbide are widely used as additives to tungsten carbide, which is a raw material for cemented carbide cutting tools such as turning tools, tips, cutters, drills, and dies, and good mixing performance with tungsten carbide is required for producing high-quality cemented carbide cutting tools. Patent Document 1 discloses a tantalum carbide powder used as an additive, which has little powder aggregation, is fine and uniform in size, and has a low oxygen content that is stoichiometrically sufficiently bonded to carbon.

[0003] Furthermore, when a metal carbide is formed as a film on the surface of a substrate made of carbon or ceramic, it functions as a protective film that suppresses thermal decomposition of the substrate, for example, protecting the carbon material from oxidation when heated. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-31016 Summary of the Invention [Problem to be solved by the invention]

[0005] However, it was thought that extremely fine particles would have poor fluidity and poor mixability due to aggregation, etc. Furthermore, in a method for producing metal carbides, such as that disclosed in Patent Document 1, in which a mixture of metal oxide and carbon black is heat-treated (calcined) and granulated, the circularity of the produced tantalum carbide powder and tantalum carbide-niobium composite powder is low. Furthermore, a milling process performed after granulation further reduces the circularity. Thus, metal carbides with extremely fine particles and low circularity have poor fluidity, which makes them less compatible with raw materials for cemented carbide cutting tools, such as tungsten carbide. This prevents the formation of a homogeneous cemented carbide material, resulting in inferior performance of cemented carbide tools produced from such raw materials.

[0006] Furthermore, when a film is formed on the surface of a substrate, if the circularity and fluidity are high, a uniform film can be easily formed on the surface of the substrate.

[0007] In view of the above problems, the present invention provides a method for producing a metal carbide having high circularity and high fluidity, a metal carbide powder, and a metal carbide intermediate dispersion liquid. [Means for solving the problem]

[0008] The method for producing a metal carbide of the present invention, which has been made to solve the above-mentioned problems, is a method for producing a powdery metal carbide using a complex polymerization method, and includes a complexing step of mixing a metal hydroxide and an alkaline compound to produce a first mixed liquid, adding hydrogen peroxide to the first mixed liquid to produce a second mixed liquid, and further adding an organic acid to the second mixed liquid to produce a metal carbide precursor; The method is characterized by comprising a carbonization step of producing a metal carbide by firing the metal carbide precursor, and a powderization step of crushing the metal carbide to form a metal carbide powder. For the sake of convenience, the method for producing metal carbide of the present invention, which includes a powdering step of crushing metal carbide to form metal carbide powder, will be described below as the method for producing metal carbide powder of the present invention.

[0009] In the complexing step in the method for producing a metal carbide powder of the present invention, first, a metal hydroxide described below and an alkaline compound are mixed to produce a first mixed liquid.

[0010] The metal hydroxide is preferably a hydroxide of tantalum, niobium, titanium, tungsten, molybdenum, zirconium, etc. In particular, the metal hydroxide is preferably tantalum hydroxide or niobium hydroxide.

[0011] For example, tantalum hydroxide is preferably adjusted by adding water (e.g., pure water) to contain tantalum at a concentration of 1 to 100 g / L in terms of Ta2O5. In this case, a tantalum concentration of 1 g / L or more in terms of Ta2O5 is preferred because it results in a tantalum acid compound hydrate that is highly soluble in water. Considering productivity, 10 g / L or more is more preferred, and 20 g / L or more is even more preferred. On the other hand, a tantalum concentration of 100 g / L or less in terms of Ta2O5 is preferred because it results in a tantalum acid compound hydrate that is highly soluble in water. To more reliably synthesize a tantalum acid compound hydrate that is highly soluble in water, a tantalum concentration of 90 g / L or less is more preferred, 80 g / L or less is even more preferred, and 70 g / L or less is particularly preferred. Similarly, niobium hydroxide is preferably adjusted to contain niobium at a concentration of 1 to 100 g / L in terms of Nb2O5.

[0012] The alkaline compound is preferably one or more compounds selected from ammonia, sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, and organic nitrogen compounds. Examples of organic nitrogen compounds include amine compounds, quaternary ammonium compounds, guanidine compounds, and azole compounds. An amine compound or a quaternary ammonium compound is preferred, and methylamine, dimethylamine, tetramethylammonium hydroxide (TMAH), or tetraethylammonium hydroxide (TEAH) is more preferred. The alkaline compound may also be an alkaline solution in which the alkaline compound is dissolved. The alkaline solution is preferably an alkaline aqueous solution, particularly aqueous ammonia.

[0013] The alkaline compound content in the first mixed solution is preferably more than 0% by mass and less than 50% by mass, and more preferably 0.01% by mass or more and 4% by mass or less. From the viewpoints of reactivity and dispersibility, a high alkaline compound content is desirable. On the other hand, since the alkaline compound is a volatile component, a low content is desirable from the viewpoint of suppressing volatilization during film formation in a subsequent process. Typically, the alkaline compound content may be 0.1% by mass or more, 0.5% by mass or more, 1% by mass or more, 2% by mass or more, 3% by mass or more, 5% by mass or more, 8% by mass or more, or 10% by mass or more. On the other hand, the alkaline compound content may be 30% by mass or less, 25% by mass or less, 20% by mass or less, or 10% by mass or less.

[0014] The alkaline compound content in the first mixed solution can be expressed by the molar ratio of alkaline compound to metal hydroxide. The molar ratio of alkaline compound to metal hydroxide is preferably greater than 0 and less than 100, more preferably 0.001 to 100, even more preferably 0.01 to 50, particularly preferably 0.1 to 30, and even more particularly preferably 4 to 20. Typically, the molar ratio of alkaline compound to metal hydroxide may be 0.005 or greater, 0.05 or greater, or 0.5 or greater. On the other hand, the molar ratio of alkaline compound to metal hydroxide may be 15 or less, 10 or less, 8 or less, 5 or less, 4 or less, 3 or less, 2 or less, 1 or less, 0.5 or less, or 0.1 or less.

[0015] Here, the alkaline compound in the alkaline compound / metal hydroxide molar ratio refers to the content of the alkaline compound in the first mixed solution. When two or more alkaline compounds are contained, the content of the alkaline compound is the total content of these two or more alkaline compounds. On the other hand, the metal hydroxide in the alkaline compound / metal hydroxide molar ratio refers to the content of the metal hydroxide in metal atom equivalent in the first mixed solution. When two or more metal hydroxides are contained, the content of the metal hydroxide in metal atom equivalent is the total content of these two or more metal hydroxides in metal atom equivalent.

[0016] For example, when the metal hydroxide to be mixed is tantalum hydroxide, the molar ratio of alkaline compound / Ta is preferably greater than 0 and less than 100, more preferably 0.001 to 100, even more preferably 0.01 to 50, particularly preferably 0.1 to 30, and even more particularly preferably 4 to 20. Typically, the molar ratio of alkaline compound / Ta may be 0.005 or greater, 0.05 or greater, or 0.5 or greater. On the other hand, the molar ratio of alkaline compound / Ta may be 15 or less, 10 or less, 8 or less, 5 or less, 4 or less, 3 or less, 2 or less, 1 or less, 0.5 or less, or 0.1 or less.

[0017] Furthermore, when the metal hydroxide to be mixed is niobium hydroxide, the molar ratio of alkaline compound / Nb is preferably greater than 0 and less than 100, more preferably 0.001 to 100, even more preferably 0.01 to 50, particularly preferably 0.1 to 30, and even more particularly preferably 4 to 20. Typically, the molar ratio of alkaline compound / Ta may be 0.005 or greater, 0.05 or greater, or 0.5 or greater. On the other hand, the molar ratio of alkaline compound / Nb may be 15 or less, 10 or less, 8 or less, 5 or less, 4 or less, 3 or less, 2 or less, 1 or less, 0.5 or less, or 0.1 or less.

[0018] Furthermore, when the mixed metal hydroxides are niobium hydroxide and tantalum hydroxide, the molar ratio of the alkaline compound to the niobium and tantalum (alkaline compound / (Nb+Ta)) is preferably greater than 0 and less than 100, more preferably 0.001 to 100, even more preferably 0.01 to 50, particularly preferably 0.1 to 30, and even more particularly preferably 4 to 20. Typically, the molar ratio of alkaline compound / (Nb+Ta) may be 0.005 or greater, 0.05 or greater, or 0.5 or greater. On the other hand, the molar ratio of alkaline compound / (Nb+Ta) may be 15 or less, 10 or less, 8 or less, 5 or less, 4 or less, 3 or less, 2 or less, 1 or less, 0.5 or less, or 0.1 or less.

[0019] Furthermore, when the alkaline compound is ammonia, the ammonia content in the first mixed solution is preferably more than 0% by mass and less than 50% by mass, and more preferably 0.01% by mass or more and 4% by mass or less. From the viewpoints of reactivity and dispersibility, a high ammonia content is desirable. On the other hand, since ammonia is a volatile component, a low ammonia content is desirable from the viewpoint of suppressing volatilization during film formation in a subsequent process. Typically, the ammonia content may be 0.1% by mass or more, 0.5% by mass or more, 1% by mass or more, 2% by mass or more, 3% by mass or more, 5% by mass or more, 8% by mass or more, or 10% by mass or more. On the other hand, the ammonia content may be 30% by mass or less, 25% by mass or less, 20% by mass or less, or 10% by mass or less.

[0020] The content of ammonia in the first mixed solution can be expressed by the molar ratio of NH3 / metal hydroxide. The molar ratio of NH3 / metal hydroxide is preferably greater than 0 and less than 100, more preferably 0.001 to 100, even more preferably 0.01 to 50, particularly preferably 0.1 to 30, and even more particularly preferably 4 to 20. Typically, the molar ratio of NH3 / metal hydroxide may be 0.005 or greater, 0.05 or greater, or 0.5 or greater. On the other hand, the molar ratio of NH3 / metal hydroxide may be 15 or less, 10 or less, 8 or less, 5 or less, 4 or less, 3 or less, 2 or less, 1 or less, 0.5 or less, or 0.1 or less.

[0021] When the metal hydroxide to be mixed is tantalum hydroxide, the ammonia content is such that the NH3 / Ta molar ratio is preferably greater than 0 and less than 100, more preferably 0.001 to 100, even more preferably 0.01 to 50, particularly preferably 0.1 to 30, and even more particularly preferably 4 to 20. Typically, the NH3 / Ta molar ratio may be 0.005 or greater, 0.05 or greater, or 0.5 or greater. On the other hand, the NH3 / Ta molar ratio may be 15 or less, 10 or less, 8 or less, 5 or less, 4 or less, 3 or less, 2 or less, 1 or less, 0.5 or less, or 0.1 or less.

[0022] Furthermore, when the metal hydroxide to be mixed is niobium hydroxide, the NH3 / Nb molar ratio is preferably greater than 0 and less than 100, more preferably 0.001 to 100, even more preferably 0.01 to 50, particularly preferably 0.1 to 30, and even more particularly preferably 4 to 20. Typically, the NH3 / Ta molar ratio may be 0.005 or greater, 0.05 or greater, or 0.5 or greater. On the other hand, the NH3 / Nb molar ratio may be 15 or less, 10 or less, 8 or less, 5 or less, 4 or less, 3 or less, 2 or less, 1 or less, 0.5 or less, or 0.1 or less.

[0023] Furthermore, when the mixed metal hydroxides are niobium hydroxide and tantalum hydroxide, the molar ratio of ammonia to niobium and tantalum, NH3 / (Nb+Ta), is preferably greater than 0 and less than 100, more preferably 0.001 to 100, even more preferably 0.01 to 50, particularly preferably 0.1 to 30, and even more particularly preferably 4 to 20. Typically, the molar ratio of NH3 / (Nb+Ta) may be 0.005 or greater, 0.05 or greater, or 0.5 or greater. On the other hand, the molar ratio of NH3 / (Nb+Ta) may be 15 or less, 10 or less, 8 or less, 5 or less, 4 or less, 3 or less, 2 or less, 1 or less, 0.5 or less, or 0.1 or less.

[0024] Examples of the solvent used in the complexing step in the method for producing a metal carbide powder of the present invention include water, organic solvents, and mixed solvents thereof. Examples of organic solvents include alcohol solvents, ketone solvents, ether solvents, ester solvents, aromatic hydrocarbon solvents, and aliphatic hydrocarbon solvents, and these organic solvents may also be mixed with pure water. Examples of alcohol solvents include alcohols having 5 or fewer carbon atoms (methanol, ethanol, n-propanol, isopropyl alcohol, butanol, ethylene glycol, and propylene glycol), acetone, and high-boiling point solvents. It is preferable that the above-mentioned solvents and water are miscible with each other.

[0025] Examples of high-boiling point solvents include polyhydric alcohol-based solvents and glycol-based solvents. Examples of polyhydric alcohol-based solvents include glycerin (boiling point: 290°C), 1,6-hexanediol (boiling point: 250°C), and 1,7-heptanediol (boiling point: 259°C). Examples of glycol-based solvents include ethylene glycol (boiling point: 197.3°C), propylene glycol (boiling point: 188.2°C), diethylene glycol (boiling point: 244.3°C), triethylene glycol (boiling point: 287.4°C), oligoethylene glycol (boiling point: 287°C to 460°C), polyethylene glycol (PEG) (boiling point: 460°C or higher), and polyethylene glycol (PEG)-polypropylene glycol (PPG) copolymer (boiling point: 460°C). Examples of suitable surfactants include anionic fluorine-based surfactants (boiling point: 180°C or higher), diethylene glycol monohexyl ether (boiling point: 260°C or higher), polyoxyalkylene monoalkyl ether (boiling point: 260°C or higher), polyoxyethylene sorbitan monolaurate (boiling point: 321°C or higher), other anionic fluorine-based surfactants (boiling point: 180°C or higher), amphoteric fluorine-based surfactants (boiling point: 180°C or higher), nonionic fluorine-based surfactants (boiling point: 180°C or higher), and amine oxides (boiling point: 180°C or higher). The boiling points mentioned above are those at 1 atmosphere.

[0026] The solvent used in the complexing step in the method for producing a metal carbide powder of the present invention may contain a resin such as a polyolefin compound or a polyvinyl compound, and the resin added to the solvent may be an anionic water-soluble resin and / or a nonionic water-soluble resin.

[0027] Here, the cationic water-soluble resin is a resin that has a positive charge in water at pH=7 and has a functional group such as an amino group, an imino group, a tertiary amine group, a quaternary ammonium group, or a hydrazino group in the polymer. The anionic water-soluble resin is a resin that has a negative charge in water at pH=7 and has a functional group such as a carboxyl group, a sulfonic acid group, a sulfate ester group, or a phosphate ester group in the polymer. The nonionic water-soluble resin is not the cationic water-soluble resin or anionic water-soluble resin described above, and is a resin that has a functional group such as a hydroxyl group, an ether group, or an amide group in the polymer.

[0028] Furthermore, these resins may contain one or more water-soluble homopolymers selected from the group consisting of acrylic polymers, urethane polymers, styrene polymers, olefin polymers, amide polymers, siloxane polymers, epoxy polymers, vinyl chloride polymers, and vinyl acetate polymers, and / or water-soluble copolymers consisting of two or more of these polymers. In particular, it is preferable for the resins to contain one or more water-soluble homopolymers of acrylic polymers, styrene polymers, and olefin polymers, and / or water-soluble copolymers consisting of two or more of these polymers.

[0029] Next, in the complexing step in the method for producing metal carbide powder of the present invention, hydrogen peroxide, which will be described below, is added to the first mixed liquid thus produced to produce a second mixed liquid.

[0030] The content of hydrogen peroxide in the second mixed liquid is preferably more than 0% by mass and not more than 35% by mass, more preferably 0.001% by mass to 30% by mass, even more preferably 0.01% by mass to 25% by mass, and particularly preferably 0.1% by mass to 20% by mass. Typically, the content of hydrogen peroxide may be 0.005% by mass or more, 0.05% by mass or more, 0.5% by mass or more, 1% by mass or more, 2% by mass or more, or 4% by mass or more. On the other hand, the content of hydrogen peroxide may be 10% by mass or less, 5% by mass or less, 3% by mass or less, or 1% by mass or less.

[0031] The content of hydrogen peroxide in the second mixed solution can be expressed by the molar ratio of H2O2 / metal hydroxide. The molar ratio of H2O2 / metal hydroxide between hydrogen peroxide and metal hydroxide is preferably greater than 0 and less than 10, more preferably 0.001 to 3, and even more preferably 0.01 to 1. Typically, the molar ratio of H2O2 / metal hydroxide may be 0.005 or greater, 0.05 or greater, or 0.5 or greater. On the other hand, the molar ratio of H2O2 / metal hydroxide may be 0.8 or less, 0.7 or less, 0.6 or less, or 0.5 or less.

[0032] Here, the H2O2 in the molar ratio of H2O2 / metal hydroxide indicates the content of H2O2 in the second mixed solution. On the other hand, the metal hydroxide in the molar ratio of H2O2 / metal hydroxide indicates the content of the metal hydroxide in terms of metal atoms in the second mixed solution. Furthermore, when two or more metal hydroxides are contained, the content of the metal hydroxide in terms of metal atoms is the total content of these two or more metal hydroxides in terms of metal atoms.

[0033] Specifically, when the metal hydroxide to be mixed is tantalum hydroxide, the molar ratio H2O2 / Ta of hydrogen peroxide to tantalum is preferably greater than 0 and less than 10, more preferably 0.001 to 3, and even more preferably 0.01 to 1. Typically, the molar ratio H2O2 / Ta may be 0.005 or greater, 0.05 or greater, or 0.5 or greater. On the other hand, the molar ratio H2O2 / Ta may be 0.8 or less, 0.7 or less, 0.6 or less, or 0.5 or less.

[0034] Furthermore, when the metal hydroxide to be mixed is niobium hydroxide, the molar ratio H2O2 / Nb of hydrogen peroxide to niobium is preferably more than 0 and not more than 10, more preferably 0.001 to 3, and even more preferably 0.01 to 1. Typically, the molar ratio H2O2 / Nb may be 0.005 or more, 0.05 or more, or 0.5 or more. On the other hand, the molar ratio H2O2 / Nb may be 0.8 or less, 0.7 or less, 0.6 or less, or 0.5 or less.

[0035] Furthermore, when the metal hydroxides to be mixed are niobium hydroxide and tantalum hydroxide, the molar ratio of hydrogen peroxide to niobium and tantalum, HO / (Nb+Ta), is preferably greater than 0 and less than 10, more preferably 0.001 to 3, and even more preferably 0.01 to 1. Typically, the molar ratio HO / (Nb+Ta) may be 0.005 or greater, 0.05 or greater, or 0.5 or greater. On the other hand, the molar ratio HO / (Nb+Ta) may be 0.8 or less, 0.7 or less, 0.6 or less, or 0.5 or less.

[0036] Here, when hydrogen peroxide is added under alkaline conditions, the complexation reaction is more likely to proceed. Therefore, it is advisable to mix a metal hydroxide with an alkaline compound before adding hydrogen peroxide to produce a first mixed liquid, which is an alkaline mixed liquid.

[0037] In the complexing step of the method for producing a metal carbide powder of the present invention, an organic acid described below is added to the second mixed solution to produce a metal carbide precursor.

[0038] Examples of organic acids include carboxylic acids, polyfunctional carboxylic acids, hydroxycarboxylic acids, and amino acids. Examples of carboxylic acids include butyric acid, formic acid, acetic acid, lauric acid, oleic acid, linoleic acid, and benzoic acid. Examples of polyfunctional carboxylic acids include oxalic acid, succinic acid, malonic acid, maleic acid, glutaric acid, and citric acid. Examples of hydroxycarboxylic acids include lactic acid, gluconic acid, tartaric acid, and malic acid. Examples of amino acids include alanine, arginine, aspartic acid, and ethylenediaminetetraacetic acid. Organic acids that do not contain nitrogen atoms are particularly preferred, such as carboxylic acids, polyfunctional carboxylic acids, and hydroxycarboxylic acids, with citric acid, tartaric acid, and lactic acid being more preferred. Polyfunctional carboxylic acids are also more preferred, and citric acid, which is a polyfunctional carboxylic acid that does not contain nitrogen atoms, is most preferred. Organic acids also include various isomers (structural isomers, optical isomers, etc.) of the above-mentioned compounds. Furthermore, one or more organic acids of the above-mentioned compounds may be used.

[0039] The content of the organic acid in the metal carbide precursor is preferably more than 0% by mass and less than 100% by mass, more preferably 1% by mass to 40% by mass, and more preferably 3% by mass to 15% by mass. Typically, the content of the organic acid may be 0.1% by mass or more, 0.5% by mass or more, 2% by mass or more, 5% by mass or more, 8% by mass or more, or 10% by mass or more. On the other hand, the content of the organic acid may be 30% by mass or less, 25% by mass or less, 20% by mass or less, or 10% by mass or less. Here, when the organic acid added to the second mixed liquid is a mixture of two or more organic acids, the content of the organic acid is the total content of the two or more organic acids added.

[0040] The content of organic acid in the metal carbide precursor can be expressed by the molar ratio of organic acid / metal hydroxide. It is preferable to add the organic acid so that the molar ratio of organic acid to metal hydroxide (organic acid / metal hydroxide) is greater than 0 and less than 500. From the viewpoint of the stability of the metal carbide precursor and cost reduction, the molar ratio is more preferably 0.01 to 100, even more preferably 0.1 to 9, and particularly preferably 0.1 to 6. Typically, the molar ratio (organic acid / metal hydroxide) may be 0.005 or more, 0.5 or more, 1 or more, 2 or more, 3 or more, or 5 or more. Alternatively, the molar ratio (organic acid / metal hydroxide) may be 200 or less, 50 or less, 40 or less, 30 or less, 20 or less, 10 or less, 8 or less, or 5 or less.

[0041] Here, the organic acid in the molar ratio: organic acid / metal hydroxide indicates the content of the organic acid in the metal carbide precursor. When two or more organic acids are contained, the content of the organic acid is the total content of these two or more organic acids. On the other hand, the metal hydroxide in the molar ratio: organic acid / metal hydroxide indicates the content of the metal hydroxide in terms of metal atoms in the metal carbide precursor. When two or more metal hydroxides are contained, the content of the metal hydroxide in terms of metal atoms is the total content of these two or more metal hydroxides in terms of metal atoms.

[0042] For example, when the metal hydroxide to be mixed is tantalum hydroxide, the organic acid is preferably added so that the molar ratio of the organic acid to tantalum (organic acid / Ta) is greater than 0 and not greater than 500. From the viewpoints of stability of the metal carbide precursor and cost reduction, the molar ratio is more preferably 0.01 or greater and 100 or less, even more preferably 0.1 or greater and 9 or less, and particularly preferably 0.1 or greater and 6 or less. Typically, the molar ratio (organic acid / Ta) may be 0.005 or greater, 0.5 or greater, 1 or greater, 2 or greater, 3 or greater, or 5 or greater. On the other hand, the molar ratio (organic acid / Ta) may be 200 or less, 50 or less, 40 or less, 30 or less, 20 or less, 10 or less, 8 or less, or 5 or less.

[0043] Furthermore, when the metal hydroxide to be mixed is niobium hydroxide, the organic acid is preferably added so that the molar ratio of the organic acid to niobium (organic acid / Nb) is greater than 0 and not greater than 500. From the viewpoints of stability of the metal carbide precursor and cost reduction, the molar ratio is more preferably 0.01 to 100, even more preferably 0.1 to 9, and particularly preferably 0.1 to 6. Typically, the molar ratio (organic acid / Nb) may be 0.005 or more, 0.5 or more, 1 or more, 2 or more, 3 or more, or 5 or more. On the other hand, the molar ratio (organic acid / Nb) may be 200 or less, 50 or less, 40 or less, 30 or less, 20 or less, 10 or less, 8 or less, or 5 or less.

[0044] Furthermore, when the metal hydroxides to be mixed are niobium hydroxide and tantalum hydroxide, the organic acid is preferably added so that the molar ratio of the organic acid to the niobium and tantalum (organic acid / (Nb+Ta)) is greater than 0 and less than 500. From the viewpoints of stability of the metal carbide precursor and cost reduction, the molar ratio is more preferably 0.01 to 100, even more preferably 0.1 to 9, and particularly preferably 0.1 to 6. Typically, the molar ratio (organic acid / (Nb+Ta)) may be 0.005 or greater, 0.5 or greater, 1 or greater, 2 or greater, 3 or greater, or 5 or greater. On the other hand, the molar ratio (organic acid / (Nb+Ta) may be 200 or less, 50 or less, 40 or less, 30 or less, 20 or less, 10 or less, 8 or less, or 5 or less.

[0045] The complexing step in the method for producing a metal carbide powder of the present invention described above does not require heating and can be carried out at room temperature (25° C.).

[0046] It is presumed that at least a portion of the metal carbide precursor thus produced forms a peroxo complex containing the metal element derived from the metal hydroxide.

[0047] Next, in the carbonization step of the method for producing metal carbide powder of the present invention, the metal carbide precursor is fired to produce the metal carbide. The metal carbide precursor produced by the complexing step in the method for producing metal carbide powder of the present invention is placed in a static furnace and fired in the atmosphere at a firing temperature of 1000°C or higher and 1900°C or lower for a firing time of 1 hour or higher and 12 hours or lower, thereby producing a metal carbide.

[0048] In the powdering step of the method for producing metal carbide powder of the present invention, the metal carbide is crushed to form metal carbide powder. The metal carbide powder of the present invention is obtained by crushing the metal carbide produced in the carbonization step in the method for producing a metal carbide powder of the present invention using a ball mill, jet mill, cutter mill, or the like. The crushed metal carbide powder may be classified using a sieve or the like, and the undersized particles (fine particles) may be used as the metal carbide powder of the present invention. The oversized particles (coarse particles) may be subjected to another crushing step and classified before use. The sieve used for classification is preferably one with openings of 30 to 1000 μm.

[0049] The metal carbide powder (sample) of the present invention formed by the above-described method for producing a metal carbide powder of the present invention can be confirmed to be a carbide from the peaks in the X-ray diffraction pattern obtained by powder X-ray diffraction measurement under the following X-ray diffraction measurement conditions and X-ray diffraction analysis conditions.

[0050] =X-ray diffraction measurement conditions= Equipment: MiniFlex II (Rigaku Corporation) Measurement range (2θ): 5 to 90° Sampling width: 0.02° Scan speed: 2.0° / min ·X-ray: CuKα ray Voltage: 30kV ·Current: 15mA Divergence slit: 1.25° Scattering slit: 1.25° Receiving slit: 0.3 mm

[0051] =X-ray diffraction analysis conditions= Use the Rigaku data analysis software PDXL2. · Smooth the peak with b-spline to clarify the peak top.

[0052] The fluidity of the metal carbide powder of the present invention formed by the above-described method for producing a metal carbide powder of the present invention can be determined as follows: A sample of the metal carbide powder of the present invention is placed in an ABD powder property measuring instrument manufactured by Tsutsui Scientific Instruments Co., Ltd., equipped with a filter with a pore size of 850 μm or 1000 μm, the filter is vibrated for 1 minute, and the sample that passes through the filter is recovered. The amount of the sample recovered is then measured, and the recovery rate is calculated from the formula: recovery rate = recovery amount (g) / 10 g × 100, thereby determining the fluidity of the metal carbide powder of the present invention.

[0053] The metal carbide powder of the present invention can be produced by carrying out each of the steps in the method for producing a metal carbide powder of the present invention described above. The metal carbide powder of the present invention can also be produced by carrying out the following steps in addition to the steps described above.

[0054] The method for producing a metal carbide powder of the present invention may include a drying step of drying the metal carbide precursor. The metal carbide precursor produced in the complexing step can be dried by a drying method described below to remove excess hydrogen peroxide and ammonia contained in the metal carbide precursor.

[0055] By removing excess hydrogen peroxide from the metal carbide precursor, changes in the solution due to the evaporation of hydrogen peroxide can be suppressed, and the precursor can be used more safely and legally. Specifically, if the hydrogen peroxide content in the metal carbide precursor is 6% by mass or less, it is exempt from the Deleterious Substances Control Act, making it easier to use in terms of safety and storage methods. Furthermore, by removing excess ammonia contained in the metal carbide precursor, the precursor can be used more safely and in terms of workability.

[0056] As an example of the drying step in the method for producing a metal carbide powder of the present invention, the heating temperature in the drying step may be less than 100°C. If the heating temperature in the drying step is 25°C or higher but lower than 100°C, excess hydrogen peroxide and ammonia contained in the metal carbide precursor will volatilize, resulting in a white peroxo complex powder. The heating temperature is preferably 90°C or lower. The heating time is preferably 1 hour or higher but 100 hours or lower, and more preferably 5 hours or higher but 20 hours or lower.

[0057] In another example of the drying step in the method for producing metal carbide powder of the present invention, the heating temperature in the drying step may be 100° C. or higher. When the heating temperature in the drying step is 100°C or higher and 200°C or lower, excess hydrogen peroxide and ammonia contained in the metal carbide precursor volatilize, resulting in a greenish-white peroxo complex powder. A heating temperature of 110°C or higher is more preferable. The heating time is preferably 1 hour or higher and 100 hours or lower, and more preferably 5 hours or higher and 20 hours or lower.

[0058] Furthermore, as another example of the drying step in the method for producing a metal carbide powder of the present invention, a white peroxo complex powder can be obtained by vacuum drying without heating. The heating time is preferably 1 hour to 100 hours, and more preferably 5 hours to 20 hours. Note that when vacuum drying is used, excess hydrogen peroxide and ammonia contained in the metal carbide precursor are not removed and remain.

[0059] The method for producing a metal carbide powder of the present invention may further include a crushing step of crushing the metal carbide precursor dried in the drying step. The peroxo complex powder, which is the dried metal carbide precursor obtained by each of the drying steps described above, is pulverized using a ball mill, jet mill, cutter mill, etc. Pulverizing the peroxo complex powder is preferred from the viewpoint that the peroxo complex powder becomes more easily dissolved in pure water in the dissolving step.

[0060] Furthermore, the method for producing a metal carbide of the present invention is a method for producing a metal carbide in the form of a film using a complex polymerization method, and is characterized by comprising: a complexing step of mixing a metal hydroxide and an alkaline compound to produce a first mixed liquid, adding hydrogen peroxide to the first mixed liquid to produce a second mixed liquid, and further adding an organic acid to the second mixed liquid to produce a metal carbide precursor; a dissolving step of dispersing the metal carbide precursor in pure water to produce a metal carbide intermediate; and a carbonization step of applying the metal carbide intermediate onto a substrate and firing it to form a metal carbide film containing metal carbide on the substrate. For convenience of explanation, the method for producing a metal carbide of the present invention, which includes a carbonization step of forming a metal carbide film containing a metal carbide on a substrate, will be described as the method for producing a metal carbide film of the present invention.

[0061] In the complexing step in the method for producing a metal carbide film of the present invention, a metal hydroxide and an alkaline compound are mixed to produce a first mixed liquid, hydrogen peroxide is added to the first mixed liquid to produce a second mixed liquid, and an organic acid is further added to the second mixed liquid to produce a metal carbide precursor.

[0062] The metal carbide precursor produced in the complexing step of the method for producing a metal carbide film of the present invention is preferably in the form of a transparent solution without precipitation, from the viewpoint of forming a uniform film. The particle size of the metal carbide precursor is preferably small, and is preferably 1000 nm or less from the viewpoint of stability over time, more preferably 500 nm or less, and particularly preferably 100 nm or less. Typically, the particle size may be 900 nm or less, 800 nm or less, 700 nm or less, 600 nm or less, 400 nm or less, 300 nm or less, 200 nm or less, 50 nm or less, 30 nm or less, 20 nm or less, 10 nm or less, 6 nm or less, 2 nm or less, 1 nm or less, or 0.6 nm or less. Meanwhile, the particle size of the particles is preferably 1 nm or more, more preferably 2 nm or more, even more preferably 6 nm or more, particularly preferably 10 nm or more, and may even be 100 nm or more, 200 nm or more, 300 nm or more, 400 nm or more, or 500 nm or more. Typically, the particle size is 10 nm or more and 800 nm or less. Typically, the particle size of the metal carbide precursor is 10 nm or more and 800 nm or less. From the viewpoint of forming a thick film, the metal carbide precursor may be in the form of an aqueous dispersion in which the metal carbide precursor is precipitated.

[0063] The particle size of the metal carbide precursor produced in the complexing step in the method for producing a metal carbide film of the present invention is a particle size (D50) measured by particle size distribution measurement using dynamic light scattering.

[0064] Dynamic light scattering is a method for measuring the light scattering intensity from particles undergoing Brownian motion by irradiating a solution such as a suspension with light such as a laser beam. The particle size and distribution are then determined from the temporal fluctuations of this intensity. Specifically, particle size distribution was evaluated using a zeta potential, particle size, and molecular weight measurement system (Otsuka Electronics Co., Ltd.: ELSZ-2000ZS) in accordance with JIS Z 8828:2019 "Particle Size Analysis - Dynamic Light Scattering." If necessary, the sample was diluted 1000 times with pure water. Just before measurement, the sample was filtered through an 11 μm pore filter and ultrasonicated for 3 minutes in an ultrasonic cleaner (AS ONE Corporation: VS-100III) to remove dust and other particles. The liquid temperature of the sample was adjusted to 25°C. The particle size (D50) refers to the median diameter (D50), which is the particle size at 50% of the cumulative distribution curve.

[0065] The complexing step in the method for producing a metal carbide film of the present invention is the same as the complexing step in the method for producing a metal carbide powder of the present invention except for the points mentioned above, and therefore a detailed description thereof will be omitted.

[0066] In the dissolving step in the method for producing a metal carbide film of the present invention, a metal carbide intermediate is produced by dispersing a metal carbide precursor in pure water.

[0067] Pure water is added to the metal carbide precursor obtained in the complexing step in the method for producing a metal carbide film of the present invention, and the mixture is stirred for 10 minutes to produce a metal carbide intermediate. When the metal carbide intermediate of the present invention is applied to a substrate in the carbonization step described below, it is preferable to adjust the content to facilitate application, and it is preferable to adjust the solid content of the metal carbide intermediate of the present invention to be 1% by mass or more and 70% by mass or less. The dissolving step does not require heating and can be carried out at room temperature (25°C).

[0068] The solid content of the metal carbide intermediate of the present invention is preferably adjusted depending on the type and material of the base material, and is more preferably 2% by mass or more and 65% by mass or less, even more preferably 4% by mass or more and 60% by mass or less, particularly preferably 5% by mass or more and 55% by mass or less, and even more particularly preferably 10% by mass or more and 50% by mass or less.

[0069] Furthermore, when tantalum hydroxide is used as the metal hydroxide, the tantalum content in the metal carbide intermediate of the present invention may typically be 5% by mass or more and 30% by mass or less, 5% by mass or more and 25% by mass or less, 5% by mass or more and 20% by mass or less, 5% by mass or more and 15% by mass or less, or 5% by mass or more and 10% by mass or less.

[0070] Here, the tantalum content in the metal carbide intermediate of the present invention is calculated by diluting the intermediate appropriately with dilute hydrochloric acid as needed, and measuring the Ta mass fraction in Ta equivalent terms using ICP optical emission spectrometry (AG-5110 manufactured by Agilent Technologies) in accordance with JIS K0116:2014.

[0071] Furthermore, when niobium hydroxide is used as the metal hydroxide, the niobium content in the metal carbide intermediate of the present invention may typically be 5% by mass or more and 30% by mass or less, 5% by mass or more and 25% by mass or less, 5% by mass or more and 20% by mass or less, 5% by mass or more and 15% by mass or less, or 5% by mass or more and 10% by mass or less.

[0072] The niobium content in the metal carbide intermediate of the present invention can be calculated by measuring the Nb mass fraction in terms of Nb, in the same manner as the tantalum content described above.

[0073] In the dissolving step, if the metal carbide precursor has a suitable solid content when applied to a substrate, there is no need to adjust the solid content by adding pure water to the metal carbide precursor obtained in the complexing step.

[0074] In the carbonization step of the method for producing a metal carbide film of the present invention, a metal carbide intermediate is applied to a substrate and then fired to form a metal carbide film containing the metal carbide on the substrate. Examples of the substrate include crucibles, furnace materials, electrodes, fibers, filtration devices, filters, protective tubes, heater tubes, burner nozzles, and fire-resistant jigs. Examples of materials include carbon, metals, and ceramics, and examples of metals include metal carbides, metal oxides, and metal nitrides.

[0075] Specifically, the metal carbide intermediate obtained in the dissolving step in the method for producing a metal carbide film of the present invention is filtered, for example, with a filter having a pore size of 1 μm, and applied to the surface of a substrate using a brush or the like. The substrate to which the metal carbide intermediate has been applied is then placed in a static furnace and fired in the atmosphere at a firing temperature of 1000°C to 1900°C for a firing time of 1 hour to 12 hours, thereby forming a metal carbide film on the surface of the substrate. Note that, in addition to the method of applying the metal carbide intermediate to the surface of the substrate using a brush or the like, other methods may also be used, such as spraying the metal carbide intermediate onto the surface of the substrate or immersing the substrate in a container containing the metal carbide intermediate.

[0076] The metal carbide film of the present invention can be produced by carrying out each of the steps in the method for producing a metal carbide film of the present invention described above. The metal carbide film of the present invention can also be produced by carrying out the following steps in addition to the steps described above.

[0077] In the method for producing a metal carbide film of the present invention, a drying step of drying the metal carbide precursor produced in the complexing step may be included as a pre-step of the dissolving step of producing a metal carbide intermediate in which the metal carbide precursor is dispersed in pure water. By drying the metal carbide precursor produced by the complexing step using the drying method described above, it is possible to remove excess hydrogen peroxide and ammonia contained in the metal carbide precursor.

[0078] By removing excess hydrogen peroxide from the metal carbide precursor, when pure water is added to the metal carbide precursor in the carbonization step and the resulting metal carbide intermediate is applied to the surface of a substrate, foaming does not occur and the application can be uniform. Furthermore, by removing excess ammonia contained in the metal carbide precursor, it becomes easier to use in terms of safety and workability.

[0079] The drying step in the method for producing a metal carbide film of the present invention is the same as the drying step in the method for producing a metal carbide powder of the present invention described above, and therefore a detailed description thereof will be omitted.

[0080] Furthermore, the method for producing a metal carbide film of the present invention may include a crushing step of crushing the metal carbide precursor dried in the drying step, similar to the method for producing a metal carbide powder of the present invention described above. Note that the crushing step in the method for producing a metal carbide film of the present invention is the same as the crushing step in the method for producing a metal carbide powder of the present invention described above, and therefore a description thereof will be omitted.

[0081] Furthermore, the method for producing a metal carbide precursor of the present invention is a method for producing a metal carbide precursor using a complex polymerization method, and is characterized by comprising a complexation step of mixing a metal hydroxide and an alkaline compound to produce a first mixed liquid, adding hydrogen peroxide to the first mixed liquid to produce a second mixed liquid, and further adding an organic acid to the second mixed liquid to produce a metal carbide precursor.

[0082] The complexing step in the method for producing a metal carbide precursor of the present invention is the same as the complexing step in the method for producing a metal carbide of the present invention described above, and therefore a detailed description thereof will be omitted.

[0083] The method for producing a metal carbide precursor of the present invention may further include a drying step of drying the metal carbide precursor produced in the complexing step. Here, the drying step in the method for producing a metal carbide precursor of the present invention is the same as the drying step in the method for producing a metal carbide of the present invention described above, and therefore a description thereof will be omitted.

[0084] Furthermore, the method for producing a metal carbide intermediate of the present invention is a method for producing a metal carbide intermediate using a complex polymerization method, and is characterized by comprising a complexing step of mixing a metal hydroxide and an alkaline compound to produce a first mixed liquid, adding hydrogen peroxide to the first mixed liquid to produce a second mixed liquid, and further adding an organic acid to the second mixed liquid to produce a metal carbide precursor, and a dissolving step of dispersing the metal carbide precursor in pure water to produce a metal carbide intermediate.

[0085] The complexing step and dissolving step in the method for producing a metal carbide intermediate of the present invention are the same as the complexing step and dissolving step in the method for producing a metal carbide of the present invention described above, and therefore detailed description thereof will be omitted.

[0086] The method for producing a metal carbide intermediate of the present invention may further include a drying step of drying the metal carbide precursor produced in the complexing step. Here, the drying step in the method for producing a metal carbide intermediate of the present invention is the same as the drying step in the method for producing a metal carbide of the present invention described above, and therefore a description thereof will be omitted.

[0087] In the method for producing a metal carbide intermediate of the present invention, the heating temperature in the drying step is preferably less than 100° C., similar to the drying step in the method for producing a metal carbide of the present invention described above.

[0088] In the method for producing a metal carbide intermediate of the present invention, the heating temperature in the drying step is preferably 100° C. or higher, similar to the drying step in the method for producing a metal carbide of the present invention described above.

[0089] Furthermore, the method for producing a metal carbide intermediate of the present invention may be vacuum drying without heating, similar to the drying step in the method for producing a metal carbide of the present invention described above.

[0090] The method for producing a metal carbide intermediate of the present invention is characterized by further comprising a crushing step of crushing the metal carbide precursor dried in the drying step. Here, the crushing step in the method for producing a metal carbide intermediate of the present invention is the same as the crushing step in the method for producing a metal carbide of the present invention described above, and therefore a description thereof will be omitted.

[0091] The metal carbide powder of the present invention has a specific surface area of ​​1 m2 measured by the BET method. 2 / g or more and a circularity of 0.78 or more. The metal carbide powder of the present invention has a specific surface area of ​​1 m2 as measured by the BET method. 2 / g or more and the circularity is 0.78 or more, even if the particles are very fine, they have high fluidity.

[0092] The metal carbide powder of the present invention has a specific surface area of ​​1 m2 as measured by the BET method. 2 When the specific surface area of ​​the metal carbide powder of the present invention is 2 m / g or more, the void ratio in the powder packed bed decreases, and the reactivity with other substances increases when the powder is used as an additive. 2 / g or more is more preferable, and 4m 2 It is more preferable that the saturation rate is 1 / g or more.

[0093] Here, the specific surface area of ​​the metal carbide powder of the present invention as measured by the BET method can be measured using a fully automatic specific surface area measuring device (Macsorb HM-1230 type) in accordance with JIS Z8830.

[0094] Furthermore, the metal carbide powder of the present invention is preferably one having a circularity of 0.78 or more, since this reduces the void ratio in the powder packed bed and increases the reactivity with other substances when used as an additive. The circularity of the metal carbide powder of the present invention is more preferably 0.8 or more, and even more preferably 0.9 or more. On the other hand, there is no particular upper limit to the circularity, and it is sufficient if it is 1 or less.

[0095] Here, the circularity of the metal carbide powder of the present invention is calculated by "circularity = 1 / major axis × minor axis", and the arithmetic mean value of the circularities of multiple particles is taken as "circularity". Here, the "major axis" and "minor axis" are calculated as follows: Using a scanning electron microscope (SEM) (Hitachi High-Technologies Corporation: S-4800), an SEM image of the primary particles of the metal carbide powder of the present invention is measured at a magnification that allows measurement of the primary particles of the metal carbide powder of the present invention. Then, using image analysis software ImageJ, the "major axis" and "minor axis" of 20 randomly selected particles are measured.

[0096] The metal carbide powder of the present invention preferably has a primary particle size of 0.7 μm or less as measured by the BET method and a circularity of 0.78 or more. The metal carbide powder of the present invention has a primary particle size of 0.7 μm or less as measured by the BET method and a circularity of 0.78 or more, and has high fluidity even when it is an extremely fine particle.

[0097] The metal carbide powder of the present invention preferably has a primary particle size of 0.7 μm or less as measured by the BET method, since this reduces the void ratio in the powder packed bed and increases the reactivity with other substances when used as an additive. The primary particle size of the metal carbide powder of the present invention as measured by the BET method is more preferably 0.4 μm or less, and even more preferably 0.2 μm or less.

[0098] Here, the primary particle diameter D of the metal carbide powder of the present invention as determined by the BET method is calculated by the following formula (1).

[0099]

number

[0100] In formula (1), "D" represents the primary particle diameter (μm) of the metal carbide powder of the present invention, and "S" represents the specific surface area (m 2 / g), "ρ" is the density of the metal carbide of the present invention (g / cm 3 For example, the density of tantalum carbide (TaC) is 13.9 (g / cm 3 ), and the density of niobium carbide (NbC) is 8.57 (g / cm3 )

[0101] The metal carbide powder of the present invention preferably contains tantalum carbide, niobium carbide, titanium carbide, tungsten carbide, molybdenum carbide, zirconium carbide, or the like, and more preferably contains tantalum carbide or niobium carbide.

[0102] Furthermore, the metal carbide powder of the present invention preferably has a chlorine content of 100 ppm or less, from the viewpoint of preventing residual hydrogen peroxide in the metal carbide powder of the present invention. The metal carbide powder of the present invention more preferably has a chlorine content of 50 ppm or less, and even more preferably has a chlorine content of 25 ppm or less. In this specification, unless otherwise specified, "ppm" refers to "ppm by mass."

[0103] The chlorine content in the metal carbide powder of the present invention can be measured by combustion ion chromatography. Specifically, an appropriate amount of sample is collected on a ceramic board, and the sample is heated under an argon (Ar) atmosphere at 1000°C for 10 minutes using a combustion ion chromatograph (Nitto Seiko Analytech Co., Ltd.: AQF-2100H), and the amount of chlorine generated is measured, thereby determining the chlorine content in the metal carbide powder of the present invention.

[0104] Furthermore, the metal carbide powder of the present invention preferably has a nitrogen content of 1000 ppm or less, from the viewpoint of preventing the presence of alkaline compounds, such as aqueous ammonia, in the metal carbide powder of the present invention. The metal carbide powder of the present invention more preferably has a nitrogen content of 800 ppm or less, and even more preferably 500 ppm or less. Typically, the nitrogen content of the metal carbide powder may be 500 ppm or less, 250 ppm or less, 100 ppm or less, 50 ppm or less, or 25 ppm or less.

[0105] Here, the nitrogen content in the metal carbide powder of the present invention can be measured by a thermal conductivity method using an oxygen / nitrogen analyzer (ON836 manufactured by LECO Corp.) Specifically, an appropriate amount of sample is sealed in a Ni capsule, and the nitrogen content in the metal carbide powder of the present invention can be determined by the thermal conductivity method using the oxygen / nitrogen analyzer.

[0106] Furthermore, the metal carbide powder of the present invention may contain components (referred to as "other components") other than components derived from metal hydroxides, such as components derived from tantalum or tantalum hydroxide, or components derived from niobium or niobium hydroxide, to the extent that the effects of the metal carbide powder are not impaired. Examples of other components include Li, Mg, Si, Ca, Mn, Ni, Cu, Zn, Sr, and Ba, but are not limited to these. The content of other components in the metal carbide powder of the present invention is preferably less than 5 mass%, more preferably less than 4 mass%, and even more preferably less than 3 mass%, calculated as elements (metal element or non-metal element). It is anticipated that the metal carbide powder of the present invention may contain unintended, unavoidable impurities. The content of unavoidable impurities is preferably less than 0.01 mass%.

[0107] The cemented carbide tool of the present invention is characterized by containing the above-mentioned metal carbide powder of the present invention. The cemented carbide tool of the present invention contains the metal carbide powder of the present invention, and therefore, even if it is an extremely fine particle, it has high fluidity, high mixability with tungsten carbide, and excellent subsequent reactivity, and has the properties required of a cemented carbide tool, such as chipping resistance, plastic deformation resistance, and wear resistance.

[0108] The metal carbide intermediate dispersion liquid of the present invention is characterized in that it contains a metal compound, an alkaline compound, hydrogen peroxide, and an organic acid, and that the particle size (D50) of particles in the metal carbide intermediate dispersion liquid, as determined by particle size distribution measurement using a dynamic light scattering method, is 1000 nm or less.

[0109] The metal compound is preferably a hydroxide, chloride or alkoxide of tantalum, niobium, titanium, zirconium, hafnium, bismuth, molybdenum or tungsten.

[0110] The metal compound is more preferably a metal hydroxide, such as hydroxides of tantalum, niobium, titanium, zirconium, hafnium, bismuth, molybdenum, or tungsten, and is particularly preferably tantalum hydroxide and / or niobium hydroxide.

[0111] The alkaline compound is preferably one or more alkaline compounds selected from ammonia, sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, and organic nitrogen compounds. Examples of the organic nitrogen compounds include amine compounds, quaternary ammonium compounds, guanidine compounds, and azole compounds. An amine compound or a quaternary ammonium compound is preferred, and methylamine, dimethylamine, tetramethylammonium hydroxide (TMAH), or tetraethylammonium hydroxide (TEAH) is more preferred. Ammonia is particularly preferred as the alkaline compound.

[0112] The alkaline compound content in the metal carbide intermediate dispersion of the present invention is preferably more than 0% by mass and less than 50% by mass, and more preferably 0.01% by mass or more and 4% by mass or less. From the viewpoints of reactivity and dispersibility, a high alkaline compound content is desirable. On the other hand, since the alkaline compound is a volatile component, a low content is desirable from the viewpoint of suppressing volatilization during film formation in a subsequent process. Typically, the alkaline compound content may be 0.1% by mass or more, 0.5% by mass or more, 1% by mass or more, 2% by mass or more, 3% by mass or more, 5% by mass or more, 8% by mass or more, or 10% by mass or more. On the other hand, the alkaline compound content may be 30% by mass or less, 25% by mass or less, 20% by mass or less, or 10% by mass or less.

[0113] The content of the alkaline compound in the metal carbide intermediate dispersion of the present invention can be expressed by the molar ratio of alkaline compound to metal compound. The molar ratio of alkaline compound to metal compound is preferably greater than 0 and less than 100, more preferably 0.001 to 100, even more preferably 0.01 to 50, particularly preferably 0.1 to 30, and even more particularly preferably 4 to 20. Typically, the molar ratio of alkaline compound to metal compound may be 0.005 or greater, 0.05 or greater, or 0.5 or greater. On the other hand, the molar ratio of alkaline compound to metal compound may be 15 or less, 10 or less, 8 or less, 5 or less, 4 or less, 3 or less, 2 or less, 1 or less, 0.5 or less, or 0.1 or less.

[0114] Here, the alkaline compound in the alkaline compound / metal compound molar ratio indicates the content of the alkaline compound in the metal carbide intermediate dispersion liquid of the present invention. Furthermore, when two or more types of alkaline compounds are contained in the metal carbide intermediate dispersion liquid of the present invention, the content of the alkaline compound is the total content of these two or more types of alkaline compounds. On the other hand, the metal compound in the alkaline compound / metal compound molar ratio indicates the content of the metal compound in terms of metal atoms in the metal carbide intermediate dispersion liquid of the present invention. Furthermore, when two or more types of metal compounds are contained in the metal carbide intermediate dispersion liquid of the present invention, the content of the metal compound in terms of metal atoms is the total content of these two or more types of metal compounds in terms of metal atoms.

[0115] When the metal compound contained in the metal carbide intermediate dispersion liquid of the present invention is tantalum hydroxide, the molar ratio of alkaline compound / Ta is preferably greater than 0 and not greater than 100, more preferably 0.001 to 100, even more preferably 0.01 to 50, particularly preferably 0.1 to 30, and even more particularly preferably 4 to 20. Typically, the molar ratio of alkaline compound / Ta may be 0.005 or greater, 0.05 or greater, or 0.5 or greater. On the other hand, the molar ratio of alkaline compound / Ta may be 15 or less, 10 or less, 8 or less, 5 or less, 4 or less, 3 or less, 2 or less, 1 or less, 0.5 or less, or 0.1 or less.

[0116] Furthermore, when the metal compound contained in the metal carbide intermediate dispersion liquid of the present invention is niobium hydroxide, the molar ratio of alkaline compound / Nb is preferably greater than 0 and less than 100, more preferably 0.001 to 100, even more preferably 0.01 to 50, particularly preferably 0.1 to 30, and even more particularly preferably 4 to 20. Typically, the molar ratio of alkaline compound / Ta may be 0.005 or greater, 0.05 or greater, or 0.5 or greater. On the other hand, the molar ratio of alkaline compound / Nb may be 15 or less, 10 or less, 8 or less, 5 or less, 4 or less, 3 or less, 2 or less, 1 or less, 0.5 or less, or 0.1 or less.

[0117] Furthermore, when the metal compounds contained in the metal carbide intermediate dispersion liquid of the present invention are niobium hydroxide and tantalum hydroxide, the molar ratio of the alkaline compounds to the niobium and tantalum (alkaline compounds / (Nb+Ta)) is preferably greater than 0 and less than 100, more preferably 0.001 to 100, even more preferably 0.01 to 50, particularly preferably 0.1 to 30, and even particularly preferably 4 to 20. Typically, the molar ratio of alkaline compounds / (Nb+Ta) may be 0.005 or greater, 0.05 or greater, or 0.5 or greater. On the other hand, the molar ratio of alkaline compounds / (Nb+Ta) may be 15 or less, 10 or less, 8 or less, 5 or less, 4 or less, 3 or less, 2 or less, 1 or less, 0.5 or less, or 0.1 or less.

[0118] When the alkaline compound is, for example, ammonia, the ammonia content is preferably more than 0% by mass and less than 50% by mass, and more preferably 0.01% by mass or more and 4% by mass or less. From the viewpoints of reactivity and dispersibility, a high ammonia content is desirable. On the other hand, since ammonia is a volatile component, a low ammonia content is desirable from the viewpoint of suppressing volatilization during film formation in a subsequent process. Typically, the ammonia content may be 0.1% by mass or more, 0.5% by mass or more, 1% by mass or more, 2% by mass or more, 3% by mass or more, 5% by mass or more, 8% by mass or more, or 10% by mass or more. On the other hand, the ammonia content may be 30% by mass or less, 25% by mass or less, 20% by mass or less, or 10% by mass or less.

[0119] The content of ammonia contained in the metal carbide intermediate dispersion liquid of the present invention can be expressed by the molar ratio of NH3 / metal compound. The molar ratio of NH3 / metal compound is preferably greater than 0 and less than 100, more preferably 0.001 to 100, even more preferably 0.01 to 50, particularly preferably 0.1 to 30, and even more particularly preferably 4 to 20. Typically, the molar ratio of NH3 / metal compound may be 0.005 or greater, 0.05 or greater, or 0.5 or greater. On the other hand, the molar ratio of NH3 / metal compound may be 15 or less, 10 or less, 8 or less, 5 or less, 4 or less, 3 or less, 2 or less, 1 or less, 0.5 or less, or 0.1 or less.

[0120] When the metal compound contained in the metal carbide intermediate dispersion liquid of the present invention is tantalum hydroxide, the NH3 / Ta molar ratio is preferably greater than 0 and less than 100, more preferably 0.001 to 100, even more preferably 0.01 to 50, particularly preferably 0.1 to 30, and even more particularly preferably 4 to 20. Typically, the NH3 / Ta molar ratio may be 0.005 or greater, 0.05 or greater, or 0.5 or greater. On the other hand, the NH3 / Ta molar ratio may be 15 or less, 10 or less, 8 or less, 5 or less, 4 or less, 3 or less, 2 or less, 1 or less, 0.5 or less, or 0.1 or less.

[0121] Furthermore, when the metal compound contained in the metal carbide intermediate dispersion liquid of the present invention is niobium hydroxide, the NH3 / Nb molar ratio is preferably greater than 0 and less than 100, more preferably 0.001 to 100, even more preferably 0.01 to 50, particularly preferably 0.1 to 30, and even more particularly preferably 4 to 20. Typically, the NH3 / Ta molar ratio may be 0.005 or greater, 0.05 or greater, or 0.5 or greater. On the other hand, the NH3 / Nb molar ratio may be 15 or less, 10 or less, 8 or less, 5 or less, 4 or less, 3 or less, 2 or less, 1 or less, 0.5 or less, or 0.1 or less.

[0122] Furthermore, when the metal compounds contained in the metal carbide intermediate dispersion liquid of the present invention are niobium hydroxide and tantalum hydroxide, the molar ratio of ammonia to niobium and tantalum, NH3 / (Nb+Ta), is preferably greater than 0 and less than 100, more preferably 0.001 to 100, even more preferably 0.01 to 50, particularly preferably 0.1 to 30, and even particularly preferably 4 to 20. Typically, the molar ratio of NH3 / (Nb+Ta) may be 0.005 or greater, 0.05 or greater, or 0.5 or greater. On the other hand, the molar ratio of NH3 / (Nb+Ta) may be 15 or less, 10 or less, 8 or less, 5 or less, 4 or less, 3 or less, 2 or less, 1 or less, 0.5 or less, or 0.1 or less.

[0123] The amount of alkaline compound contained in the metal carbide intermediate dispersion liquid of the present invention can be reduced by replenishing the solvent that has evaporated by heating or the like after preparing the metal carbide intermediate dispersion liquid.

[0124] The content of hydrogen peroxide in the metal carbide intermediate dispersion liquid of the present invention is preferably more than 0% by mass and not more than 35% by mass, more preferably 0.001% by mass to 30% by mass, even more preferably 0.01% by mass to 25% by mass, and particularly preferably 0.1% by mass to 20% by mass. Typically, the content of hydrogen peroxide may be 0.005% by mass or more, 0.05% by mass or more, 0.5% by mass or more, 1% by mass or more, 2% by mass or more, or 4% by mass or more. On the other hand, the content of hydrogen peroxide may be 10% by mass or less, 5% by mass or less, 3% by mass or less, or 1% by mass or less.

[0125] The content of hydrogen peroxide in the metal carbide intermediate dispersion liquid of the present invention can be expressed by the molar ratio of H2O2 / metal compound. The molar ratio of hydrogen peroxide to metal compound, H2O2 / metal compound, is preferably greater than 0 and less than 10, more preferably 0.001 to 3, and even more preferably 0.01 to 1. Typically, the molar ratio of H2O2 / metal compound may be 0.005 or greater, 0.05 or greater, or 0.5 or greater. On the other hand, the molar ratio of H2O2 / metal compound may be 0.8 or less, 0.7 or less, 0.6 or less, or 0.5 or less.

[0126] Here, H2O2 in the molar ratio H2O2 / metal compound indicates the content of H2O2 in the metal carbide intermediate dispersion liquid of the present invention. On the other hand, the metal compound in the molar ratio H2O2 / metal compound indicates the content of the metal compound in terms of metal atoms in the metal carbide intermediate dispersion liquid of the present invention. Furthermore, when the metal carbide intermediate dispersion liquid of the present invention contains two or more types of metal compounds, the content of the metal compound in terms of metal atoms is the total content of these two or more types of metal compounds in terms of metal atoms.

[0127] When the metal compound contained in the metal carbide intermediate dispersion liquid of the present invention is, for example, tantalum hydroxide, the molar ratio of hydrogen peroxide to tantalum, H2O2 / Ta, is preferably greater than 0 and not greater than 10, more preferably 0.001 to 3, and even more preferably 0.01 to 1. Typically, the molar ratio H2O2 / Ta may be 0.005 or greater, 0.05 or greater, or 0.5 or greater. On the other hand, the molar ratio H2O2 / Ta may be 0.8 or less, 0.7 or less, 0.6 or less, or 0.5 or less.

[0128] Furthermore, when the metal compound contained in the metal carbide intermediate dispersion liquid of the present invention is, for example, niobium hydroxide, the molar ratio H2O2 / Nb of hydrogen peroxide to niobium is preferably more than 0 and not more than 10, more preferably 0.001 to 3, and even more preferably 0.01 to 1. Typically, the molar ratio H2O2 / Nb may be 0.005 or more, 0.05 or more, or 0.5 or more. On the other hand, the molar ratio H2O2 / Nb may be 0.8 or less, 0.7 or less, 0.6 or less, or 0.5 or less.

[0129] Furthermore, when the metal compounds contained in the metal carbide intermediate dispersion liquid of the present invention are, for example, niobium hydroxide and tantalum hydroxide, the molar ratio of hydrogen peroxide to niobium and tantalum, HO / (Nb+Ta), is preferably greater than 0 and less than 10, more preferably 0.001 to 3, and even more preferably 0.01 to 1. Typically, the molar ratio HO / (Nb+Ta) may be 0.005 or greater, 0.05 or greater, or 0.5 or greater. On the other hand, the molar ratio HO / (Nb+Ta) may be 0.8 or less, 0.7 or less, 0.6 or less, or 0.5 or less.

[0130] It is preferable that the content of hydrogen peroxide is small from the viewpoint of safety (volatility, volatility due to reaction with other materials). On the other hand, with the above-mentioned content and molar ratio of hydrogen peroxide, good dispersibility can be obtained.

[0131] Examples of organic acids include carboxylic acids, polyfunctional carboxylic acids, hydroxycarboxylic acids, and amino acids. Examples of carboxylic acids include butyric acid, formic acid, acetic acid, lauric acid, oleic acid, linoleic acid, and benzoic acid. Examples of polyfunctional carboxylic acids include oxalic acid, succinic acid, malonic acid, maleic acid, glutaric acid, and citric acid. Examples of hydroxycarboxylic acids include lactic acid, gluconic acid, tartaric acid, and malic acid. Examples of amino acids include alanine, arginine, aspartic acid, and ethylenediaminetetraacetic acid. Organic acids that do not contain nitrogen atoms are particularly preferred, such as carboxylic acids, polyfunctional carboxylic acids, and hydroxycarboxylic acids, with citric acid, tartaric acid, and lactic acid being more preferred. Polyfunctional carboxylic acids are also more preferred, and citric acid, which is a polyfunctional carboxylic acid that does not contain nitrogen atoms, is most preferred. Organic acids also include various isomers (structural isomers, optical isomers, etc.) of the above-mentioned compounds. Furthermore, one or more organic acids of the above-mentioned compounds may be used.

[0132] The organic acid content is preferably more than 0% by mass and less than 100% by mass, more preferably 1% by mass or more and 40% by mass or less, and preferably 3% by mass or more and 15% by mass or less. Typically, the organic acid content may be 0.1% by mass or more, 0.5% by mass or more, 2% by mass or more, 5% by mass or more, 8% by mass or more, or 10% by mass or more. On the other hand, the organic acid content may be 30% by mass or less, 25% by mass or less, 20% by mass or less, or 10% by mass or less. Here, when two or more organic acids are contained in the metal carbide intermediate dispersion liquid of the present invention, the organic acid content is the total content of these two or more organic acids.

[0133] The content of organic acid in the metal carbide intermediate dispersion of the present invention can be expressed by the molar ratio of organic acid to metal compound. It is preferable to add the organic acid so that the molar ratio of organic acid to metal compound (organic acid / metal compound) is greater than 0 and less than 500. From the viewpoint of the stability and cost reduction of the metal carbide intermediate dispersion of the present invention, the molar ratio is more preferably 0.01 to 100, even more preferably 0.1 to 9, and particularly preferably 0.1 to 6. Typically, the molar ratio (organic acid / metal compound) may be 0.005 or more, 0.5 or more, 1 or more, 2 or more, 3 or more, or 5 or more. On the other hand, the molar ratio (organic acid / metal compound) may be 200 or less, 50 or less, 40 or less, 30 or less, 20 or less, 10 or less, 8 or less, or 5 or less.

[0134] Here, the organic acid in the molar ratio: organic acid / metal compound indicates the content of the organic acid in the metal carbide intermediate dispersion liquid of the present invention. Furthermore, when two or more organic acids are contained in the metal carbide intermediate dispersion liquid of the present invention, the content of the organic acid is the total content of these two or more organic acids. On the other hand, the metal compound in the molar ratio: organic acid / metal compound indicates the content of the metal compound in terms of metal atoms in the metal carbide intermediate dispersion liquid of the present invention. Furthermore, when two or more metal compounds are contained in the metal carbide intermediate dispersion liquid of the present invention, the content of the metal compound in terms of metal atoms is the total content of these two or more metal compounds in terms of metal atoms.

[0135] When the metal hydroxide contained in the metal carbide intermediate dispersion liquid of the present invention is tantalum hydroxide, the organic acid is preferably added so that the molar ratio of the organic acid to tantalum (organic acid / Ta) is greater than 0 and not greater than 500. From the viewpoint of the stability and cost reduction of the metal carbide intermediate dispersion liquid of the present invention, the molar ratio is more preferably 0.01 or more and 100 or less, even more preferably 0.1 or more and 9 or less, and particularly preferably 0.1 or more and 6 or less. Typically, the molar ratio (organic acid / Ta) may be 0.005 or more, 0.5 or more, 1 or more, 2 or more, 3 or more, or 5 or more. On the other hand, the molar ratio (organic acid / Ta) may be 200 or less, 50 or less, 40 or less, 30 or less, 20 or less, 10 or less, 8 or less, or 5 or less.

[0136] Furthermore, in the case of niobium hydroxide contained in the metal carbide intermediate dispersion liquid of the present invention, it is preferable to add an organic acid so that the molar ratio of the organic acid to niobium (organic acid / Nb) is more than 0 and not more than 500. From the viewpoint of the stability and cost reduction of the metal carbide intermediate dispersion liquid of the present invention, it is more preferably 0.01 to 100, even more preferably 0.1 to 9, and particularly preferably 0.1 to 6. Typically, the molar ratio (organic acid / Nb) may be 0.005 or more, 0.5 or more, 1 or more, 2 or more, 3 or more, or 5 or more. On the other hand, the molar ratio (organic acid / Nb) may be 200 or less, 50 or less, 40 or less, 30 or less, 20 or less, 10 or less, 8 or less, or 5 or less.

[0137] Furthermore, when the metal hydroxide contained in the metal carbide intermediate dispersion liquid of the present invention is niobium hydroxide and tantalum hydroxide, the organic acid is preferably added so that the molar ratio of the organic acid to the niobium and tantalum (organic acid / (Nb+Ta)) is greater than 0 and not greater than 500. From the viewpoint of the stability and cost reduction of the metal carbide intermediate dispersion liquid of the present invention, the molar ratio is more preferably 0.01 to 100, even more preferably 0.1 to 9, and particularly preferably 0.1 to 6. Typically, the molar ratio (organic acid / (Nb+Ta)) may be 0.005 or greater, 0.5 or greater, 1 or greater, 2 or greater, 3 or greater, or 5 or greater. On the other hand, the molar ratio (organic acid / (Nb+Ta)) may be 200 or less, 50 or less, 40 or less, 30 or less, 20 or less, 10 or less, 8 or less, or 5 or less.

[0138] Furthermore, the metal carbide intermediate dispersion liquid of the present invention may contain water, an organic solvent, or a mixed solvent thereof as the solvent. Examples of organic solvents include alcohol solvents, ketone solvents, ether solvents, ester solvents, aromatic hydrocarbon solvents, and aliphatic hydrocarbon solvents, and the solvent may be a mixture of these organic solvents and pure water. Examples of alcohol solvents include alcohols having 5 or fewer carbon atoms (methanol, ethanol, n-propanol, isopropyl alcohol, butanol, ethylene glycol, and propylene glycol), high-boiling point solvents, and acetone. The above-mentioned solvents are preferably compatible with water. Examples of high-boiling point solvents include polyhydric alcohol-based solvents and glycol-based solvents. It is preferable that the solvent contained in the metal carbide intermediate dispersion liquid of the present invention is water, as this allows high dispersibility to be maintained.

[0139] The solvent may contain a resin such as a polyolefin compound or a polyvinyl compound, and the resin added to the solvent may be an anionic water-soluble resin and / or a nonionic water-soluble resin.

[0140] As described above, the metal carbide intermediate dispersion of the present invention contains a metal compound, an alkaline compound, hydrogen peroxide, and an organic acid, and it is presumed that at least a portion of these components form a peroxo complex containing a metal element derived from the metal compound.

[0141] Furthermore, in terms of stability over time, the particle size (D50) of the particles in the metal carbide intermediate dispersion of the present invention, as measured by dynamic light scattering particle size distribution measurement, is preferably 1000 nm or less, more preferably 500 nm or less, and particularly preferably 100 nm or less. Typically, the particle size (D50) may be 900 nm or less, 800 nm or less, 700 nm or less, 600 nm or less, 400 nm or less, 300 nm or less, 200 nm or less, 50 nm or less, 30 nm or less, 20 nm or less, 10 nm or less, 6 nm or less, 2 nm or less, 1 nm or less, or 0.6 nm or less. On the other hand, the particle diameter (D50) of the particles in the metal carbide intermediate dispersion liquid of the present invention is preferably 1 nm or more, more preferably 2 nm or more, even more preferably 6 nm or more, particularly preferably 10 nm or more, and may further be 100 nm or more, 200 nm or more, 300 nm or more, 400 nm or more, or 500 nm or more. Typically, the particle diameter (D50) of the particles in the metal carbide intermediate dispersion liquid of the present invention is 10 nm or more and 800 nm or less.

[0142] Specifically, particle size distribution was evaluated using a zeta potential, particle size, and molecular weight measurement system (ELSZ-2000ZS, manufactured by Otsuka Electronics Co., Ltd.) in accordance with JIS Z 8828:2019 "Particle size analysis - dynamic light scattering method." If necessary, the measurement sample was diluted 1000 times with pure water. Just before measurement, the sample was filtered through an 11 μm pore size filter to remove dust and other particles, and then ultrasonicated for 3 minutes in an ultrasonic cleaner (VS-100III, manufactured by AS ONE Corporation). The liquid temperature of the measurement sample was adjusted to 25°C. The particle size (D50) of the particles in the metal carbide intermediate dispersion of the present invention refers to the median diameter (D50), which is the particle size at 50% of the cumulative distribution curve. Furthermore, in this specification, unless otherwise specified, the "particle diameter (D50)" includes both the particle diameter (D50) of particles in the metal carbide intermediate dispersion liquid of the present invention adjusted to a liquid temperature of 25°C immediately after production, and the particle diameter (D50) of particles in the metal carbide intermediate dispersion liquid of the present invention after being left to stand for two weeks or three weeks from the day of production of the metal carbide intermediate dispersion liquid in an incubator set at room temperature of 25°C.

[0143] The metal carbide intermediate dispersion liquid of the present invention is characterized in that it contains a metal compound, an alkaline compound, hydrogen peroxide, and an organic acid, and that the maximum light transmittance of the metal carbide intermediate dispersion liquid in a wavelength region of 350 nm to 750 nm is 70% or more.

[0144] The metal carbide intermediate dispersion liquid of the present invention contains a metal compound, an alkaline compound, hydrogen peroxide, and an organic acid as described above. Note that the metal carbide intermediate dispersion liquid of the present invention may contain water, an organic solvent, or a mixed solvent thereof as the solvent as described above.

[0145] Furthermore, the metal carbide intermediate dispersion liquid of the present invention preferably has a maximum light transmittance of 70% or more in the wavelength region of 350 nm to 750 nm, which results in high dispersibility and excellent uniformity of the components in the liquid. The maximum light transmittance in the wavelength region of 350 nm to 750 nm is more preferably 85% or more, even more preferably 90% or more, and most preferably 100%. Typically, the maximum light transmittance may be 72% or more, 74% or more, 76% or more, 78% or more, 80% or more, 90% or more, 98% or more, or 99% or more.

[0146] Furthermore, the metal carbide intermediate dispersion liquid of the present invention preferably has a light transmittance of 70% or more at one or more wavelengths of 350 nm, 450 nm, 550 nm, 650 nm, and 750 nm, more preferably 85% or more, even more preferably 90% or more, and most preferably 100%. Typically, the light transmittance at one or more wavelengths of 350 nm, 450 nm, 550 nm, 650 nm, and 750 nm may be 72% or more, 74% or more, 76% or more, 78% or more, 80% or more, 90% or more, 98% or more, or 99% or more.

[0147] Furthermore, the metal carbide intermediate dispersion liquid of the present invention preferably has a light transmittance in the wavelength region of 350 nm to 750 nm of 70% or more, more preferably 85% or more, even more preferably 90% or more, and most preferably 100%. Typically, the light transmittance in the wavelength region of 350 nm to 750 nm may be 72% or more, 74% or more, 76% or more, 78% or more, 80% or more, 90% or more, 98% or more, or 99% or more.

[0148] Although the measured value of the light transmittance may exceed 100% due to measurement error or the like, since the theoretical upper limit is 100%, a measured value exceeding 100% is considered to be 100%. Thus, a liquid in which the maximum light transmittance in the wavelength region of 350 nm to 750 nm of the metal carbide intermediate dispersion liquid of the present invention is 70% or more is defined as the "metal carbide intermediate dispersion liquid" of the present invention. Furthermore, unless otherwise specified, the term "light transmittance" in this specification includes both the light transmittance of the metal carbide intermediate dispersion liquid of the present invention adjusted to a liquid temperature of 25°C immediately after production, and the light transmittance of the metal carbide intermediate dispersion liquid of the present invention after being left to stand in an incubator set at room temperature of 25°C for two or three weeks from the day of production of the metal carbide intermediate dispersion liquid of the present invention.

[0149] Here, the light transmittance described above is measured for the metal carbide intermediate dispersion liquid of the present invention using a spectrophotometer under the following transmittance measurement conditions.

[0150] =Light transmittance measurement conditions= Measurement equipment: UV-Vis-NIR spectrophotometer UH4150 (Hitachi High-Tech Science Corporation) Measurement mode: Wavelength scan Data mode: %T (transparent) Measurement wavelength range: 200nm to 2000nm Scan speed: 600nm / min Sampling interval: 2nm

[0151] In the present invention, the term "dispersion" is not limited to a dispersion in which a solute is dispersed or mixed in a solvent in a monomolecular state, but also includes aggregates in which a plurality of molecules are attracted to each other by intermolecular interactions, such as (1) polymeric molecules, (2) solvated molecules, (3) molecular clusters, and (4) colloidal particles dispersed in a solvent.

[0152] The metal carbide intermediate dispersion liquid of the present invention is characterized by having a pH of 3.0 or more and 10.0 or less. The pH of the metal carbide intermediate dispersion of the present invention is preferably 3.0 or more and 10.0 or less, since the polyacid ions contained in the dispersion are stable. The pH of the metal carbide intermediate dispersion of the present invention is more preferably 4.0 or more and 7.0 or less, and even more preferably 4.7 or more and 6.5 or less. Typically, the pH may be 5.0 or more, 6.0 or more, or even 6.5 or more. On the other hand, the pH may be 9.0 or less, or 8.0 or less. In this specification, unless otherwise specified, "pH" refers to both the pH of the metal carbide intermediate dispersion of the present invention adjusted to a liquid temperature of 25°C immediately after production, and the pH of the metal carbide intermediate dispersion of the present invention after being left to stand in an incubator set at room temperature of 25°C for two or three weeks from the day of production of the metal carbide intermediate dispersion of the present invention.

[0153] Here, the pH of the metal carbide intermediate dispersion liquid of the present invention is measured by immersing an electrode (HORIBA: Standard ToupH electrode 9615S-10D) of a pH meter (HORIBA: Glass electrode type hydrogen ion concentration indicator D-51) in the metal carbide intermediate dispersion liquid of the present invention, and after confirming that the liquid temperature has stabilized at 25°C.

[0154] The metal carbide intermediate dispersion liquid of the present invention is characterized in that the molar ratio of the organic acid to the metal compound is greater than 0 and less than 500, the molar ratio of the hydrogen peroxide to the metal compound is greater than 0 and less than 10, and the molar ratio of the alkaline compound to the metal compound is greater than 0 and less than 100. In the metal carbide intermediate dispersion liquid of the present invention, it is preferable from the viewpoint of stability and dispersibility that the molar ratio of the organic acid to the metal compound is greater than 0 and less than 500, the molar ratio of the hydrogen peroxide to the metal compound is greater than 0 and less than 10, and the molar ratio of the alkaline compound to the metal compound is greater than 0 and less than 100.

[0155] The molar ratio of the organic acid to the metal compound is preferably greater than 0 to 500, more preferably 0.01 to 100, even more preferably 0.1 to 9, and particularly preferably 0.1 to 6. The molar ratio of the hydrogen peroxide to the metal compound is preferably greater than 0 to 10, more preferably 0.001 to 3, and even more preferably 0.01 to 1. The molar ratio of the alkaline compound to the metal compound is preferably greater than 0 to 100, more preferably 0.001 to 100, even more preferably 0.01 to 50, particularly preferably 0.1 to 30, and even particularly preferably 4 to 20.

[0156] Here, the molar ratio of the organic acid to the metal compound, the molar ratio of the hydrogen peroxide to the metal compound, and the molar ratio of the alkaline compound to the metal compound can be determined by calculating the metal compound content, the organic acid content, the hydrogen peroxide content, and the alkaline compound content using the following measurement methods.

[0157] The metal compound content in the metal carbide intermediate dispersion of the present invention can be calculated by diluting the dispersion appropriately with dilute hydrochloric acid as needed, and measuring the metal atom mass fraction in terms of metal atoms in the metal compound using ICP optical emission spectrometry (AG-5110 manufactured by Agilent Technologies) in accordance with JIS K0116:2014.

[0158] Methods for measuring the organic acid content in the metal carbide intermediate dispersion of the present invention include gas chromatography (GC), liquid chromatography (LC), mass spectrometry (MS), gas chromatography-mass spectrometry (GC-MS), and liquid chromatography-mass spectrometry (LC-MS).

[0159] The hydrogen peroxide content in the metal carbide intermediate dispersion of the present invention can be confirmed by, for example, using the standard addition method, measuring the relative absorbance intensity with respect to a standard solution of hydrogen peroxide. Specifically, the wavelength region in which a change in absorbance associated with peroxo complex formation is observed is identified from the UV-visible absorption spectra of a standard solution containing a known concentration of hydrogen peroxide, e.g., 1% by mass, and a standard solution containing no added hydrogen peroxide. If the difference in absorbance between the standard solution containing no added hydrogen peroxide and a sample with an unknown hydrogen peroxide concentration in that wavelength region is less than 1%, it can be confirmed that the sample with an unknown hydrogen peroxide concentration is substantially free of hydrogen peroxide. If hydrogen peroxide is present in the dispersion, it reacts with the polyacid of the metal element to form a peroxo complex. Therefore, the absence of hydrogen peroxide in the dispersion can be confirmed by determining the difference in absorbance with the standard solution containing no added hydrogen peroxide, as described above. In addition to the above-mentioned standard addition method, qualitative and quantitative analysis of hydrogen peroxide in the dispersion may be performed by, for example, using a commercially available hydrogen peroxide measurement kit, adding a reagent that undergoes a color reaction with hydrogen peroxide to the dispersion and measuring the color development, or by adding a reagent that undergoes a fluorescent reaction with hydrogen peroxide to the dispersion and measuring the luminescence.

[0160] Methods for measuring the content of alkaline compounds, such as ammonia content, in the metal carbide intermediate dispersion of the present invention include adding sodium hydroxide to the dispersion and separating the ammonia by distillation, and then quantifying the ammonia content using an ion meter; quantifying the N content in a gasified sample using a thermal conductivity meter; and the Kjeldahl method. The method of quantifying the ammonia content using an ion meter is particularly preferred. Methods for measuring the content of organic nitrogen compounds include gas chromatography (GC), ion chromatography, and gas chromatography-mass spectrometry (GC-MS). For example, the content of one or more organic nitrogen compounds selected from sodium hydroxide, potassium hydroxide, lithium hydroxide, and calcium hydroxide can be measured using ICP atomic emission spectrometry in accordance with JIS K0116:2014.

[0161] From the calculated metal compound content, organic acid content, hydrogen peroxide content, and alkaline compound content in this manner, the molar ratio of the organic acid to the metal compound, the molar ratio of the hydrogen peroxide to the metal compound, and the molar ratio of the alkaline compound to the metal compound can be calculated.

[0162] The metal carbide intermediate dispersion of the present invention is characterized in that the tantalum content in terms of Ta is 0.4 mass % or more, or the niobium content in terms of Nb is 0.35 mass % or more in terms of Nb. It is preferable that the tantalum content in terms of Ta equivalent is 0.4% by mass or more, or the niobium content in terms of Nb equivalent is 0.35% by mass or more in the metal carbide intermediate dispersion liquid of the present invention, in terms of increasing the thickness of the metal carbide film during film formation. Furthermore, it is more preferable that the tantalum content in terms of Ta equivalent is 10% by mass or more, and even more preferable that it is 20% by mass or more. Furthermore, it is more preferable that the niobium content in terms of Nb equivalent is 20% by mass or more, and even more preferable that it is 30% by mass or more in terms of Nb equivalent in the metal carbide intermediate dispersion liquid of the present invention.

[0163] As described above, the tantalum content or niobium content in the metal carbide intermediate dispersion of the present invention can be calculated by measuring the Ta mass fraction in Ta equivalent or the Nb mass fraction in Nb equivalent using ICP optical emission spectrometry (manufactured by Agilent Technologies: AG-5110) in accordance with JIS K0116:2014.

[0164] In this specification, when "X to Y" (X and Y are any numbers) is expressed, unless otherwise specified, it means "X or more and Y or less," and also includes the meaning "preferably larger than X" or "preferably smaller than Y." Furthermore, when "X or more" (X is any number) or "Y or less" (Y is any number), it also includes the meaning "preferably larger than X" or "preferably smaller than Y." [Effects of the Invention]

[0165] The method for producing metal carbide of the present invention can produce a metal carbide powder that is extremely fine and exhibits high fluidity. Furthermore, the metal carbide of the present invention exhibits high fluidity even in the form of extremely fine particles. Furthermore, the metal carbide intermediate dispersion of the present invention is a dispersion that has high dispersibility and does not produce precipitates even after a long period of time has elapsed. [Brief explanation of the drawings]

[0166] [Figure 1] 1 is a table showing the physical property values ​​of metal carbide intermediate dispersions according to Examples 3 to 10 and Comparative Examples 8 to 10. [Figure 2] 1 is a table showing the measurement results of metal carbide intermediate dispersions according to Examples 3 to 10 and Comparative Examples 8 to 10. BEST MODE FOR CARRYING OUT THE INVENTION

[0167] The metal carbide according to the embodiment of the present invention will be further described below with reference to Examples 1 and 2 and Comparative Examples 1 to 7. However, the present invention is not limited to the following examples.

[0168] Example 1 A first mixed solution was obtained by stirring and mixing 200 g of tantalum hydroxide and 92 g of 25 mass % ammonia water for 10 minutes. 220 g of 35 mass % hydrogen peroxide water was then added to the first mixed solution and stirred for 10 minutes to obtain a second mixed solution. 79 g of citric acid was then added to the second mixed solution and stirred for 10 minutes to obtain a peroxo complex aqueous dispersion according to Example 1 containing tantalum, which is the metal carbide precursor according to Example 1.

[0169] The obtained aqueous dispersion of the peroxo complex according to Example 1 was a transparent solution without precipitate immediately after production, and remained a transparent solution without precipitate even 7 days after production. Furthermore, the Ta2O5-equivalent concentration of the aqueous dispersion of the peroxo complex according to Example 1 after 7 days of production was 175 g / L. Furthermore, the average particle size of the aqueous dispersion of the peroxo complex according to Example 1 after 7 days of production, as measured by dynamic light scattering, was 625.2 nm.

[0170] Then, from the peroxo complex aqueous dispersion of Example 1, a powder-shaped metal carbide and a film-shaped metal carbide were produced.

[0171] First, the peroxo complex aqueous dispersion according to Example 1 was placed in a static furnace and dried by heating at a temperature of 110°C for 12 hours, thereby obtaining a peroxo complex powder containing tantalum. Furthermore, the peroxo complex powder containing tantalum was filled into a carbon crucible, which was then placed in a high-temperature vacuum furnace and fired in the atmosphere at a firing temperature of 1500°C for 1 hour, thereby obtaining tantalum carbide. The obtained tantalum carbide was then crushed using a ball mill or the like, thereby obtaining the tantalum carbide powder, which is the powdered metal carbide according to Example 1. The tantalum carbide powder according to Example 1 was confirmed to be tantalum carbide (TaC, ICDD Card No. 00-019-1292), since a peak was observed in the 2θ=33° to 90° range from the results of XRD measurement obtained according to the above-mentioned X-ray diffraction measurement conditions and X-ray diffraction analysis conditions.

[0172] Next, the peroxo-complex aqueous dispersion according to Example 1 was applied to a carbon black substrate, and the carbon black substrate coated with the peroxo-complex aqueous dispersion according to Example 1 was placed in a static furnace and dried at a heating temperature of 110°C for 10 minutes. The dried carbon black substrate coated with the peroxo-complex aqueous dispersion according to Example 1 was then placed in a high-temperature vacuum furnace and fired in the atmosphere at a firing temperature of 1600°C for 60 minutes to obtain a tantalum carbide film, which is a metal carbide film in the form of Example 1. The tantalum carbide film according to Example 1 was confirmed to be a single-phase tantalum carbide (TaC, ICDD Card No. 00-019-1292) because a peak was observed in the 2θ=33 to 90° range from the results of XRD measurement obtained according to the above-mentioned X-ray diffraction measurement conditions and X-ray diffraction analysis conditions.

[0173] Example 2 100 g of niobium hydroxide, 153 g of 25 mass % ammonia water, and 365 g of 35 mass % hydrogen peroxide water were mixed and stirred for 10 minutes to obtain a mixed solution. Then, 87.6 g of citric acid was added to the mixed solution and stirred for 10 minutes to obtain a peroxo complex dispersion containing niobium, which is a metal carbide precursor according to Example 2.

[0174] The obtained peroxo complex dispersion of Example 2 was a transparent solution without precipitate immediately after its production, and remained a transparent solution without precipitate even 7 days after its production. Furthermore, the Nb2O5-equivalent concentration of the peroxo complex dispersion of Example 2 7 days after its production was 133 g / L. Furthermore, the average particle size of the peroxo complex dispersion of Example 2 7 days after its production, as measured by dynamic light scattering, was 540 nm.

[0175] Then, from the peroxo complex aqueous dispersion of Example 2, a powder-shaped metal carbide and a film-shaped metal carbide were produced.

[0176] First, the peroxo complex dispersion according to Example 2 was placed in a static furnace and dried by heating at 110°C for 12 hours, thereby obtaining a peroxo complex powder containing niobium. The peroxo complex powder containing niobium was then filled into a carbon crucible, which was then placed in a high-temperature vacuum furnace and fired in the atmosphere at 1500°C for 1 hour, thereby obtaining niobium carbide. The obtained niobium carbide was then crushed using a ball mill or the like to obtain the niobium carbide powder, which is the metal carbide according to Example 2. The niobium carbide powder according to Example 2 was confirmed to be niobium carbide (TaNb, PDF Card No. 01-076-7071) because a peak was observed in the 2θ=33° to 90° range from the results of XRD measurement performed according to the X-ray diffraction measurement conditions and X-ray diffraction analysis conditions described above.

[0177] Next, the peroxo complex aqueous dispersion according to Example 2 was applied to a carbon black substrate, and the carbon black substrate coated with the peroxo complex aqueous dispersion according to Example 2 was placed in a static furnace and dried at a heating temperature of 110°C for 10 minutes. The dried carbon black substrate coated with the peroxo complex aqueous dispersion according to Example 1 was then placed in a high-temperature vacuum furnace and fired in the atmosphere at a firing temperature of 1600°C for 60 minutes to obtain a niobium carbide film, which is a metal carbide film in the form of Example 2. The niobium carbide film according to Example 2 was confirmed to be a single-phase niobium carbide (TaNb, PDF Card No. 01-076-7071) because a peak was observed in the 2θ=33° to 90° range from the results of XRD measurement obtained according to the above-mentioned X-ray diffraction measurement conditions and X-ray diffraction analysis conditions.

[0178] (Comparative Example 1) 120 kg of tantalum oxide and 22 kg of carbon black were weighed on a platform balance and mixed by stirring in a vertical mixer for 5 minutes to obtain a mixed powder.

[0179] This mixed powder was filled into a carbon container (2 kg / bottle), fed into a resistance-heated hydrogen furnace at a rate of two bottles every three hours, and fired at a temperature of 1,700°C for 14 hours to perform primary carbonization, thereby obtaining primary carbide.

[0180] This primary carbide was filled into a carbon crucible (100 kg / bottle), placed in a high-frequency induction heating vacuum furnace, and fired at 1,800°C for 5 hours to obtain a secondary carbide.

[0181] The secondary carbide was cooled to room temperature in the high-frequency induction heating vacuum furnace, removed from the carbon crucible, and coarsely crushed into lumps with a diameter of 2 cm or less using a jaw crusher.

[0182] After the coarse pulverization, the coarsely pulverized secondary carbide was finely pulverized by carrying out pulverization for 20 hours using a ball mill filled with iron balls of 20 to 50 mmφ.

[0183] The finely pulverized secondary carbide was then classified using a vibrating sieve, and the undersize particles (fine particles) were collected to obtain powdered tantalum carbide, which was the metal carbide according to Comparative Example 1.

[0184] (Comparative Example 2) In Comparative Example 2, the coarsely crushed secondary carbide was blown through a wind speed of 2.5 m 3 A similar production method to that of Comparative Example 1 was carried out, except that the powder was finely pulverized using a jet mill, which is an airflow pulverizer, set at a flow rate of 1 / min and a sample supply rate of 10 kg / hr, to obtain powdered tantalum carbide, which is the metal carbide of Comparative Example 2.

[0185] (Comparative Example 3) In Comparative Example 3, the same production method as in Comparative Example 1 was carried out, except that tantalum oxide was changed to niobium oxide and the amount of carbon black added was changed to 13 kg, thereby obtaining powdered niobium carbide, which is a metal carbide according to Comparative Example 3.

[0186] Comparative Example 4 50 g of tantalum pentachloride was dissolved in a small amount of methanol, water was added, and then 25 mass% aqueous ammonia was added to obtain a precipitate of tantalum acid hydrate Ta2O5·nH2O. The precipitate was washed with water to remove chloride ions, and then 12.57 g of citric acid and 46 g of 25 mass% aqueous ammonia were added and mixed, followed by the addition of 109 g of 35 mass% aqueous hydrogen peroxide and stirring for 10 minutes to obtain a peroxo complex dispersion containing tantalum, which is a metal carbide precursor according to Comparative Example 4.

[0187] The obtained peroxo-complex dispersion liquid according to Comparative Example 4 was a transparent solution with a white precipitate immediately after production, and remained a transparent solution with a white precipitate even 7 days after production. Furthermore, the peroxo-complex dispersion liquid according to Comparative Example 4 after 7 days of production was centrifuged to separate the white precipitate, and the resulting dispersion had a Ta2O5-equivalent concentration of 39 g / L. Furthermore, the peroxo-complex dispersion liquid according to Comparative Example 4 after 7 days of production contained white precipitate, making it difficult to measure the average particle size by dynamic light scattering.

[0188] The peroxo complex dispersion liquid according to Comparative Example 4 was then placed in a static furnace and heated and dried at a temperature of 110°C for 12 hours, as in Example 1, to obtain a dried powder. The obtained dried powder was filled into a carbon crucible, which was then placed in a high-temperature vacuum furnace and fired in the atmosphere at a firing temperature of 1500°C for 1 hour, to obtain a fired powder. The fired powder was analyzed by XRD under the X-ray diffraction measurement conditions and X-ray diffraction analysis conditions described above. No peak was observed within the 2θ range of 33° to 90°, confirming that the carbonization reaction had not progressed.

[0189] (Comparative Example 5) In Comparative Example 5, a peroxo complex dispersion according to Comparative Example 5 was obtained by carrying out the same production method as in Comparative Example 4, except that the citric acid in Comparative Example 4 was changed to 37.4 g of lactic acid.

[0190] The obtained peroxo-complex dispersion liquid according to Comparative Example 5 was a transparent solution with a white precipitate immediately after production, and remained a transparent solution with a white precipitate even 7 days after production. Furthermore, the peroxo-complex dispersion liquid according to Comparative Example 5 after 7 days of production was centrifuged to separate the white precipitate, and the resulting dispersion had a Ta2O5-equivalent concentration of 2 g / L. Furthermore, the peroxo-complex dispersion liquid according to Comparative Example 5 after 7 days of production contained white precipitate, making it difficult to measure the average particle size by dynamic light scattering.

[0191] The peroxo complex dispersion liquid according to Comparative Example 5 was then placed in a static furnace and heated and dried at a temperature of 110°C for 12 hours, as in Example 1, to obtain a dried powder. The obtained dried powder was filled into a carbon crucible, which was then placed in a high-temperature vacuum furnace and fired in the atmosphere at a firing temperature of 1500°C for 1 hour, to obtain a fired powder. The obtained fired powder was analyzed by XRD under the above-mentioned X-ray diffraction measurement conditions and X-ray diffraction analysis conditions. No peak was observed in the range of 2θ = 33° to 90°, confirming that the carbonization reaction had not progressed.

[0192] (Comparative Example 6) In Comparative Example 6, a peroxo complex dispersion according to Comparative Example 6 was obtained by carrying out the same production method as in Comparative Example 4, except that the citric acid in Comparative Example 4 was changed to 92.3 g of tartaric acid.

[0193] The obtained peroxo-complex dispersion liquid according to Comparative Example 6 was a transparent solution with a white precipitate immediately after production, and remained a transparent solution with a white precipitate even 7 days after production. Furthermore, the peroxo-complex dispersion liquid according to Comparative Example 6 after 7 days of production was centrifuged to separate the white precipitate, and the resulting dispersion had a Ta2O5-equivalent concentration of <1 g / L. Furthermore, the peroxo-complex dispersion liquid according to Comparative Example 6 after 7 days of production contained white precipitate, making it difficult to measure the average particle size by dynamic light scattering.

[0194] The peroxo complex dispersion liquid according to Comparative Example 6 was then placed in a static furnace and heated and dried at a temperature of 110°C for 12 hours, as in Example 1, to obtain a dried powder. The obtained dried powder was filled into a carbon crucible, which was then placed in a high-temperature vacuum furnace and fired in the atmosphere at a firing temperature of 1500°C for 1 hour, to obtain a fired powder. The obtained fired powder was analyzed by XRD under the above-mentioned X-ray diffraction measurement conditions and X-ray diffraction analysis conditions. No peak was observed in the range of 2θ = 33° to 90°, confirming that the carbonization reaction had not progressed.

[0195] (Comparative Example 7) In Comparative Example 7, a peroxo complex dispersion according to Comparative Example 7 was obtained by carrying out the same production method as in Comparative Example 4, except that the citric acid in Comparative Example 4 was changed to 120.2 g of EDTA (ethylenediaminetetraacetic acid).

[0196] The obtained peroxo-complex dispersion liquid according to Comparative Example 7 was a transparent solution with a white precipitate immediately after production, and remained a transparent solution with a white precipitate even 7 days after production. Furthermore, the peroxo-complex dispersion liquid according to Comparative Example 7 after 7 days of production was centrifuged to separate the white precipitate, and the resulting dispersion had a Ta2O5-equivalent concentration of <1 g / L. Furthermore, the peroxo-complex dispersion liquid according to Comparative Example 7 after 7 days of production contained a white precipitate, making it difficult to measure the average particle size by dynamic light scattering.

[0197] The peroxo complex dispersion liquid according to Comparative Example 7 was then placed in a static furnace and heated and dried at a temperature of 110°C for 12 hours, as in Example 1, to obtain a dried powder. The obtained dried powder was filled into a carbon crucible, which was then placed in a high-temperature vacuum furnace and fired in the atmosphere at a firing temperature of 1500°C for 1 hour, to obtain a fired powder. The obtained fired powder was analyzed by XRD under the above-mentioned X-ray diffraction measurement conditions and X-ray diffraction analysis conditions. No peak was observed in the range of 2θ = 33° to 90°, confirming that the carbonization reaction had not progressed.

[0198] Next, the metal carbide intermediate dispersion liquid of the embodiment according to the present invention will be further explained with reference to the following Examples 3 to 10 and Comparative Examples 8 to 10. However, the following examples do not limit the present invention.

[0199] Example 3 A first mixed solution was obtained by stirring and mixing 200 g of tantalum hydroxide and 92 g of 25 mass % ammonia water for 10 minutes. Then, 220 g of 35 mass % hydrogen peroxide water was further added to the first mixed solution, and the mixture was stirred for 10 minutes to obtain a second mixed solution. Then, 79 g of citric acid was added to the second mixed solution, and the mixture was stirred for 10 minutes to obtain a metal carbide intermediate dispersion liquid according to Example 3. The metal carbide intermediate dispersion liquid according to Example 3 is the same dispersion liquid as the peroxo complex aqueous dispersion liquid according to Example 1, which contains tantalum, the metal carbide precursor according to Example 1.

[0200] The metal carbide intermediate dispersion liquid obtained according to Example 3 had a Ta content of 0.050 mol (Ta content: 18,800 mass%). The hydrogen peroxide content was 0.009 mol (0.3 mass%), and the ammonia content was 0.2 mol (3.6 mass%). The organic acid (citric acid) content was 0.07 mol (14 mass%). The remainder was water.

[0201] Example 4 200 g of niobium hydroxide, 100 g of 25 mass % ammonia water, and 235 g of 35 mass % hydrogen peroxide water were mixed and stirred for 10 minutes to obtain a mixed liquid. Then, 75 g of citric acid was added to the mixed liquid and stirred for 10 minutes to obtain a metal carbide intermediate dispersion liquid according to Example 4.

[0202] The metal carbide intermediate dispersion liquid obtained according to Example 4 had a Nb-equivalent content of 0.020 mol (3.495% by mass of Nb). The hydrogen peroxide content was 0.009 mol (0.3% by mass), and the ammonia content was 0.2 mol (3.6% by mass). The organic acid (citric acid) content was 0.07 mol (14% by mass). The remainder was water.

[0203] Example 5 In Example 5, 79 g of citric acid and 5 g of lactic acid were added to the second mixed liquid obtained by the same production method as in Example 3, and the mixture was stirred for 10 minutes to obtain a metal carbide intermediate dispersion liquid according to Example 5.

[0204] The resulting metal carbide intermediate dispersion liquid according to Example 5 had a Ta-equivalent content of 0.010 mol (Ta-equivalent content: 4.095% by mass). The hydrogen peroxide content was 0.009 mol (0.3% by mass), and the ammonia content was 0.2 mol (3.6% by mass). The total organic acid (citric acid, lactic acid) content was 0.08 mol (15% by mass), with the breakdown of the total content being 0.07 mol (14% by mass) of citric acid and 0.010 mol (1% by mass) of lactic acid. The remainder was water.

[0205] Example 6 In Example 6, 58 g of tartaric acid was added to the second mixed liquid obtained by the same production method as in Example 3, and the mixture was stirred for 10 minutes to obtain a metal carbide intermediate dispersion liquid according to Example 6.

[0206] The resulting metal carbide intermediate dispersion liquid according to Example 6 had a Ta content of 0.010 mol (Ta content: 4.095% by mass). The hydrogen peroxide content was 0.009 mol (0.3% by mass), and the ammonia content was 0.2 mol (3.6% by mass). The organic acid (tartaric acid) content was 0.09 mol (14% by mass). The remainder was water.

[0207] Example 7 200 g of niobium hydroxide, 100 g of 25 mass % ammonia water, and 235 g of 35 mass % hydrogen peroxide water were mixed and stirred for 10 minutes to obtain a mixed liquid. Then, 75 g of citric acid and 5 g of lactic acid were added to the mixed liquid and stirred for 10 minutes to obtain a metal carbide intermediate dispersion liquid according to Example 7.

[0208] The metal carbide intermediate dispersion liquid obtained according to Example 7 had a Nb-equivalent content of 0.015 mol (3.495% by mass). The hydrogen peroxide content was 0.009 mol (0.3% by mass), and the ammonia content was 0.2 mol (3.6% by mass). The total organic acid (citric acid, lactic acid) content was 0.08 mol (15% by mass), with the breakdown of the total content being 0.07 mol (14% by mass) of citric acid and 0.010 mol (1% by mass) of lactic acid. The remainder was water.

[0209] Example 8 In Example 8, 75 g of citric acid and 5 g of tartaric acid were added to a mixed liquid obtained by the same production method as in Example 7, and the mixture was stirred for 10 minutes to obtain a metal carbide intermediate dispersion liquid according to Example 8.

[0210] The metal carbide intermediate dispersion liquid obtained according to Example 8 had a Nb-equivalent content of 0.015 mol (3.495% by mass). The hydrogen peroxide content was 0.009 mol (0.3% by mass), and the ammonia content was 0.2 mol (3.6% by mass). The total organic acid (citric acid, tartaric acid) content was 0.076 mol (15% by mass), of which the citric acid content was 0.07 mol (14% by mass) and the tartaric acid content was 0.06 mol (1% by mass). The remainder was water.

[0211] Example 9 A first mixture was obtained by stirring and mixing 100 g of tantalum hydroxide, 100 g of niobium hydroxide, and 100 g of 25 mass% ammonia water for 10 minutes. 235 g of 35 mass% hydrogen peroxide water was then added to the first mixture and stirred for 10 minutes to obtain a second mixture. 79 g of citric acid was then added to the second mixture and stirred for 10 minutes to obtain a metal carbide intermediate dispersion liquid according to Example 9.

[0212] The total content in terms of Nb and Ta in the obtained metal carbide intermediate dispersion liquid according to Example 9 was 0.025 mol (the total content in terms of Nb and Ta was 7.590% by mass), and the breakdown of this total content was as follows: Nb content was 0.015 mol (Nb content was 3.495% by mass), and Ta content was 0.010 mol (Ta content was 4.095% by mass). The hydrogen peroxide content was 0.009 mol (0.3% by mass), and the ammonia content was 0.2 mol (3.6% by mass). The organic acid (citric acid) content was 0.07 mol (14% by mass). The remainder was water.

[0213] Example 10 In Example 10, 79 g of citric acid, 5 g of tartaric acid, and 5 g of lactic acid were added to a second mixed liquid obtained by the same manufacturing method as in Example 9, and the mixture was stirred for 10 minutes to obtain a metal carbide intermediate dispersion liquid according to Example 10.

[0214] The total content in terms of Nb and Ta in the obtained metal carbide intermediate dispersion liquid according to Example 10 was 0.025 mol (the total content in terms of Nb and Ta was 7.590% by mass), and the breakdown of this total content was as follows: Nb content 0.015 mol (Nb content 3.495% by mass), Ta content 0.010 mol (Ta content 4.05% by mass). The hydrogen peroxide content was 0.009 mol (0.3% by mass), and ammonia content 0.2 mol (3.6% by mass). The total content of organic acids (citric acid, lactic acid, tartaric acid) was 0.086 mol (16% by mass), and the breakdown of this total content was: citric acid content 0.07 mol (14% by mass), lactic acid content 0.010 mol (1% by mass), and tartaric acid content 0.06 mol (1% by mass). The remainder was water.

[0215] (Comparative Example 8) 50 g of tantalum pentachloride was dissolved in a small amount of methanol, water was added, and then 25 mass% aqueous ammonia was added to obtain a precipitate of tantalum acid hydrate Ta2O5·nH2O. The precipitate was washed with water to remove chloride ions, and then 12.57 g of citric acid and 46 g of 25 mass% aqueous ammonia were added and mixed, followed by the addition of 109 g of 35 mass% aqueous hydrogen peroxide and stirring for 10 minutes to obtain a metal carbide intermediate dispersion liquid according to Comparative Example 8. Note that the metal carbide intermediate dispersion liquid according to Comparative Example 8 is the same dispersion liquid as the peroxo complex dispersion liquid according to Comparative Example 4.

[0216] The metal carbide intermediate dispersion liquid obtained according to Comparative Example 8 had a Ta content of 0.009 mol (Ta content: 3.276% by mass). The hydrogen peroxide content was 0.009 mol (0.3% by mass). The organic acid (citric acid) content was 0.07 mol (14% by mass). The remainder was water.

[0217] (Comparative Example 9) In Comparative Example 9, a metal carbide intermediate dispersion liquid according to Comparative Example 9 was obtained by carrying out the same production method as in Comparative Example 8, except that the citric acid in Comparative Example 8 was changed to 37.4 g of lactic acid. The metal carbide intermediate dispersion liquid according to Comparative Example 9 is the same dispersion liquid as the peroxo complex dispersion liquid according to Comparative Example 5.

[0218] The metal carbide intermediate dispersion liquid obtained according to Comparative Example 9 had a Ta content of 0.009 mol (Ta content: 0.164% by mass). The hydrogen peroxide content was 0.009 mol (0.3% by mass). The organic acid (lactic acid) content was 0.2 mol (15% by mass). The remainder was water.

[0219] (Comparative Example 10) In Comparative Example 10, a metal carbide intermediate dispersion liquid according to Comparative Example 10 was obtained by carrying out the same production method as in Comparative Example 8, except that the citric acid in Comparative Example 8 was changed to 92.3 g of tartaric acid. The metal carbide intermediate dispersion liquid according to Comparative Example 10 is the same dispersion liquid as the peroxo complex dispersion liquid according to Comparative Example 6.

[0220] The metal carbide intermediate dispersion liquid obtained according to Comparative Example 10 had a Ta content of 0.001 mol (Ta content: 0.082% by mass). The hydrogen peroxide content was 0.009 mol (0.3% by mass). The organic acid (tartaric acid) content was 0.1 mol (15% by mass). The remainder was water.

[0221] The following physical properties were measured for the metal carbides according to Examples 1 and 2 and Comparative Examples 1 to 3. The measured physical properties and the methods for measuring the physical properties are shown below, and the measurement results are shown in Table 1. Note that, as the results of XRD measurement showed that the sintered powders according to Comparative Examples 4 to 7 were not carbides, the following physical properties were not measured.

[0222] <Elemental analysis> If necessary, the sample was diluted appropriately with hydrofluoric acid and nitric acid, and the Ta mass fraction in Ta equivalent and the Nb mass fraction in Nb equivalent were measured by ICP optical emission spectrometry (Agilent Technologies: AG-5110).

[0223] <Specific surface area> The specific surface area of ​​each of the powdered metal carbide samples according to Examples 1 and 2 and Comparative Examples 1 to 3 was measured by the BET method in accordance with JIS Z8830 using a fully automatic specific surface area measuring device (Macsorb HM-1230).

[0224] <Primary particle size> The specific surface area and carbide density (for example, the density of tantalum carbide is 13.9 g / cm) of each sample of powdered metal carbide according to Examples 1 and 2 and Comparative Examples 1 to 3 were compared. 3 ] and the density of niobium carbide is 8.57 [g / cm 3 ]) was substituted into the above-mentioned formula (1) to calculate the primary particle diameter.

[0225] <Circularity> For each sample of powdered metal carbide according to Examples 1 and 2 and Comparative Examples 1 to 3, a scanning electron microscope (SEM) (Hitachi High-Technologies Corporation: S-4800) was used to measure SEM images of the primary particles at a magnification of 10,000 times or more and 100,000 times or less, at which the primary particles could be measured. Furthermore, the "major axis" and "minor axis" of 20 randomly selected particles were measured using image analysis software ImageJ. Circularity was calculated from the measured "major axis" and "minor axis," and the arithmetic mean value of the circularity of multiple particles was taken as the "circularity."

[0226] <Chlorine content measurement> An appropriate amount of each powdered metal carbide sample according to Examples 1 and 2 and Comparative Examples 1 to 3 was collected on a ceramic board, and the sample was heated in an argon (Ar) atmosphere at 1000°C for 10 minutes using a combustion ion chromatograph (Nitto Seiko Analytech Co., Ltd.: AQF-2100H). The amount of chlorine generated was measured, thereby determining the chlorine content in each metal carbide powder.

[0227] <Nitrogen content measurement> An appropriate amount of each powdered metal carbide sample according to Examples 1 and 2 and Comparative Examples 1 to 3 was sealed in a Ni capsule, and the nitrogen content in each metal carbide powder was determined by the thermal conductivity method using an oxygen / nitrogen analyzer (ON836 manufactured by LECO).

[0228] <Fluidity test 1> Ten grams of powder samples of the powdered metal carbides according to Examples 1 and 2 and Comparative Examples 1 to 3 were placed in an ABD powder property measuring instrument manufactured by Tsutsui Scientific Instruments Co., Ltd., equipped with a filter having a pore size of 850 μm. The filter was vibrated for one minute, and the powder sample that passed through the filter was collected. The amount of the powder sample collected was then measured, and the recovery rate was calculated from the formula: Recovery rate = Recovery amount (g) / 10 g x 100. The feed adjustment dial, which controls the vibration of the filter, was set to "8."

[0229] <Fluidity test 2> The pore size of the filter set in the ABD powder property measuring instrument manufactured by Tsutsui Rikagakuki Kikai Co., Ltd. was changed to 1000 μm, and measurements were carried out in the same manner as in fluidity test 1, and the recovery rate was calculated.

[0230] <Mixability evaluation> Mixed samples (10 g total) of the powdered metal carbides according to Examples 1 and 2 and Comparative Examples 1 to 3 and tungsten carbide (Nippon Shinkinzoku Co., Ltd., particle size 0.8 μm) were weighed so that the molar ratio of the two was 1:1. The samples were placed in a 100 ml wide-mouth PP bottle and stirred and mixed for 1 minute using a paint shaker (frequency: 50 Hz). Five samples were then taken from the mixed samples using a medicine spoon, and the Ta or Nb mass fraction of each sample was analyzed. Samples in which the difference between the maximum and minimum Ta or Nb analytical values ​​for the five samples after 1 minute of stirring and mixing was 0.5% by mass or less were evaluated as having excellent mixability and marked with a "Good"; samples in which the difference between the maximum and minimum Ta or Nb analytical values ​​for the five samples after 1 minute of stirring and mixing was greater than 0.5% by mass were evaluated as having poor mixability and marked with a "Poor"

[0231] Furthermore, the following physical properties were measured for the metal carbide intermediate dispersions according to Examples 3 to 10 and Comparative Examples 8 to 10. The measured physical properties and the methods for measuring the physical properties are shown below, and the measurement results are shown in Figs.

[0232] <Particle size distribution measurement (dynamic light scattering method)> The particle size distribution was evaluated using a zeta potential, particle size, and molecular weight measurement system (manufactured by Otsuka Electronics Co., Ltd.: ELSZ-2000) by dynamic light scattering in accordance with JIS Z 8828:2019. In addition, immediately before measurement, the metal carbide intermediate dispersions of Examples 3 to 10 and Comparative Examples 8 to 10, which were the measurement targets, were filtered through a filter with a 1 μm pore size to remove dust and other particles. Furthermore, D50 indicates the particle size at 50% volume fraction. If the measured particle size (D50) was 1 nm or greater but 500 nm or less, it was evaluated as "〇〇 (VERY GOOD)." If the particle size (D50) was greater than 500 nm but 1000 nm or less, it was evaluated as "〇 (GOOD)." If the particle size (D50) was greater than 1000 nm, it was evaluated as "× (BAD)." "Initial" in Fig. 2 refers to the metal carbide intermediate dispersion liquids according to Examples 3 to 10 and Comparative Examples 8 to 10 immediately after they were produced. Furthermore, "2 weeks later" and "3 weeks later" in Fig. 2 refer to the metal carbide intermediate dispersion liquids according to Examples 3 to 10 and Comparative Examples 8 to 10 after they were left to stand for 2 weeks or 3 weeks from the day of production in an incubator set at room temperature of 25°C. Note that the metal carbide intermediate dispersion liquids according to Comparative Examples 8 to 10 were suspension solutions, and therefore the particle diameter (D50) thereof could not be measured.

[0233] <Light transmittance measurement> 3 ml of the metal carbide intermediate dispersion liquid according to Examples 3 to 10 and Comparative Examples 8 to 10 was placed in a glass cell, and the light transmittance in the wavelength range of 350 nm to 750 nm (specifically, the light transmittance at wavelengths of 350 nm, 450 nm, 550 nm, 650 nm, and 750 nm) of the metal carbide intermediate dispersion liquid according to Examples 3 to 10 and Comparative Examples 8 to 10 was measured using a spectrophotometer according to the light transmittance measurement conditions described above. If the measured light transmittance was 85% or more and 100%, it was evaluated as "〇〇 (VERY GOOD)." If the light transmittance was 70% or more and less than 85%, it was evaluated as "〇 (GOOD)." If the light transmittance was less than 70%, it was evaluated as "× (BAD)." If the light transmittance was more than 100%, it was considered to be 100%. "Initial" in Fig. 2 refers to the metal carbide intermediate dispersion liquids according to Examples 3 to 10 and Comparative Examples 8 to 10 immediately after they were produced. Furthermore, "2 weeks later" and "3 weeks later" in Fig. 2 refer to the metal carbide intermediate dispersion liquids according to Examples 3 to 10 and Comparative Examples 8 to 10 that were left to stand for 2 weeks or 3 weeks from the day of production in an incubator set at room temperature of 25°C. Note that the metal carbide intermediate dispersion liquids according to Comparative Examples 8 to 10 were suspension solutions, and therefore the particle diameter (D50) could not be measured.

[0234] <pH measurement> The pH of the metal carbide intermediate dispersion liquids of Examples 3 to 10 and Comparative Examples 8 to 10 was measured using an electrode (HORIBA: Standard ToupH electrode 9615S-10D) of a pH meter (HORIBA: Glass electrode type hydrogen ion concentration indicator D-51) after confirming that the liquid temperature had stabilized at 25°C. "Initial" in FIG. 2 refers to the metal carbide intermediate dispersion liquids of Examples 3 to 10 and Comparative Examples 8 to 10 immediately after production. Furthermore, "2 weeks later" and "3 weeks later" in FIG. 2 refer to the metal carbide intermediate dispersion liquids of Examples 3 to 10 and Comparative Examples 8 to 10 after they were allowed to stand for 2 weeks or 3 weeks from the day of production in an incubator set at room temperature of 25°C.

[0235] [Table 1]

[0236] As shown in Table 1, the metal carbides according to Examples 1 and 2 have a specific surface area of ​​1 m2 by the BET method. 2 / g or more and the circularity was 0.78 or more, which indicated that the particles had high fluidity despite being extremely fine particles.

[0237] The metal carbides according to Examples 1 and 2 had a primary particle size of 0.7 μm or less as measured by the BET method and a circularity of 0.78 or more, and therefore had high fluidity despite being extremely fine particles.

[0238] The metal carbides according to Examples 1 and 2 do not contain hydrogen peroxide because the chlorine content in the metal carbide powder is 25 ppm or less. For example, when the metal carbides according to Examples 1 and 2 are applied to the surface of a crucible to form a film, no foaming occurs, making it easy to apply the film uniformly.

[0239] The metal carbides according to Examples 1 and 2 have a nitrogen content of 1000 ppm or less in the metal carbide powder, and therefore do not contain ammonia components, which is preferable in terms of safety and workability.

[0240] 1 and 2, the metal carbide intermediate dispersions according to Examples 3 to 10 contained a metal compound, an alkaline compound, hydrogen peroxide, and an organic acid, and when the particle size (D50) of the particles in the metal carbide intermediate dispersions was 1000 nm or less as measured by particle size distribution measurement using dynamic light scattering, the dispersions were highly dispersible and did not produce precipitates even after a long period of time. Furthermore, the metal carbide intermediate dispersions according to Examples 3 to 10 contained a metal compound, an alkaline compound, hydrogen peroxide, and an organic acid, and the maximum light transmittance of the metal carbide intermediate dispersions in the wavelength range of 350 nm to 750 nm was 70% or more, indicating high dispersibility and excellent uniformity of the components in the dispersions.

[0241] The metal carbide intermediate dispersions according to Examples 3 to 10 had a pH of 3.0 or more and 10.0 or less, and therefore the polyacid ions contained in the dispersions were stable.

[0242] The metal carbide intermediate dispersions according to Examples 3 to 10 had excellent stability and dispersibility because the molar ratio of the organic acid to the metal compound (organic acid / (Nb+Ta) shown in FIG. 1) was greater than 0 and 500, the molar ratio of the hydrogen peroxide to the metal compound (hydrogen peroxide / (Nb+Ta) shown in FIG. 1) was greater than 0 and 10, and the molar ratio of the alkaline compound to the metal compound (ammonia / (Nb+Ta) shown in FIG. 1) was greater than 0 and 100.

[0243] The metal carbide intermediate dispersion liquids according to Examples 3 to 10 are suitable in that the thickness of the metal carbide film formed is large because the tantalum content in terms of Ta is 0.4 mass % or more, or the niobium content in terms of Nb is 0.35 mass % or more in the metal carbide intermediate dispersion liquid.

[0244] Furthermore, by firing the metal carbide intermediate dispersion liquids according to Examples 3 to 10, metal carbide powders having high fluidity despite being extremely fine particles were obtained.

[0245] Furthermore, the metal carbide intermediate dispersion liquids according to Examples 3 to 10 were applied onto a substrate and fired to obtain metal carbide films.

[0246] The inventions disclosed in this specification include, in addition to the configurations of each invention and embodiment, those specified by changing these partial configurations to other configurations disclosed in this specification, to the extent applicable, or those specified by adding other configurations disclosed in this specification to these configurations, or those specified as higher-level concepts specified by deleting these partial configurations to the extent that partial effects can be obtained. [Industrial Applicability]

[0247] The metal carbide according to the present invention is extremely fine yet has high fluidity, making it suitable as an additive for the raw materials of superhardened tools. Specifically, the metal carbide according to the present invention does not require excessive mixing with the raw materials of the superhardened tools, and does not require long heating times during sintering, thereby reducing energy costs. Furthermore, the rate of defective products, which are those that cannot be formed into homogeneous superhardened tools due to poor mixability with the raw materials of the superhardened tools, can be reduced, thereby reducing waste and the energy costs associated with waste disposal. These advantages contribute to the sustainable management and efficient use of natural resources, as well as the achievement of carbon neutrality.

Claims

1. A metal carbide intermediate dispersion liquid obtained by mixing a metal hydroxide with an alkaline compound to produce a first mixed liquid, adding hydrogen peroxide to the first mixed liquid to produce a second mixed liquid, and further adding an organic acid to the second mixed liquid, and dispersing the produced metal carbide precursor in pure water, wherein A method for treating a catalysis comprising the steps of: a metal compound; an alkaline compound; hydrogen peroxide; and an organic acid; A metal carbide intermediate dispersion liquid, characterized in that the particle diameter (D50) of particles in the metal carbide intermediate dispersion liquid is 1000 nm or less, as determined by particle diameter distribution measurement using a dynamic light scattering method.

2. 2. The metal carbide intermediate dispersion liquid according to claim 1, wherein the metal carbide intermediate dispersion liquid has a maximum light transmittance of 70% or more in the wavelength region of 350 nm or more and 750 nm or less.

3. A metal carbide intermediate dispersion liquid obtained by mixing a metal hydroxide with an alkaline compound to produce a first mixed liquid, adding hydrogen peroxide to the first mixed liquid to produce a second mixed liquid, and further adding an organic acid to the second mixed liquid, and dispersing the produced metal carbide precursor in pure water, wherein A method for treating a catalysis comprising the steps of: a metal compound; an alkaline compound; hydrogen peroxide; and an organic acid; a particle size (D50) of particles in the metal carbide intermediate dispersion liquid, as determined by particle size distribution measurement using a dynamic light scattering method, being 1000 nm or less, and a maximum light transmittance of the metal carbide intermediate dispersion liquid at a wavelength of 350 nm or more and 750 nm or less being 70% or more.

4. 4. The metal carbide intermediate dispersion liquid according to claim 1, wherein the metal compound is a metal hydroxide.

5. 4. The metal carbide intermediate dispersion liquid according to claim 1, wherein the organic acid is at least one of citric acid, tartaric acid, and lactic acid.

6. 5. The metal carbide intermediate dispersion liquid according to claim 4, wherein the metal hydroxide is tantalum hydroxide and / or niobium hydroxide.

7. 4. The metal carbide intermediate dispersion liquid according to claim 1, wherein the pH is 3.0 or more and 10.0 or less.

8. 4. The metal carbide intermediate dispersion liquid according to claim 1, which is used for producing a metal carbide.

9. 4. The metal carbide intermediate dispersion liquid according to claim 1, wherein a molar ratio of the organic acid to the metal compound (organic acid / metal compound) is greater than 0 and greater than 500, a molar ratio of the hydrogen peroxide to the metal compound (hydrogen peroxide / metal compound) is greater than 0 and greater than 10, and a molar ratio of the alkaline compound to the metal compound (alkaline compound / metal compound) is greater than 0 and greater than 100.

10. 4. The metal carbide intermediate dispersion liquid according to claim 1, wherein the solvent of the metal carbide intermediate dispersion liquid is water.

11. The metal carbide intermediate dispersion liquid according to any one of claims 1 to 3, characterized in that the metal carbide intermediate dispersion liquid has a tantalum content, calculated as Ta, of 0.4 mass% or more, or a niobium content, calculated as Nb, of 0.35 mass% or more.

12. A method for producing a metal carbide intermediate according to any one of claims 1 to 3, a complexing step of mixing a metal hydroxide with an alkaline compound to produce a first mixed liquid, adding hydrogen peroxide to the first mixed liquid to produce a second mixed liquid, and further adding an organic acid to the second mixed liquid to produce a metal carbide precursor; a dissolving step of dispersing the metal carbide precursor in pure water to produce a metal carbide intermediate; 1. A method for producing a metal carbide intermediate, comprising:

13. 13. The method for producing a metal carbide intermediate according to claim 12, further comprising a drying step of drying the metal carbide precursor produced in the complexing step.

14. 14. The method for producing a metal carbide intermediate according to claim 13, further comprising a crushing step of crushing the metal carbide precursor dried in the drying step.

15. 13. The method for producing a metal carbide intermediate according to claim 12, wherein the metal hydroxide is tantalum hydroxide or niobium hydroxide.

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