JP2011028848A - Aqueous slurry and method of producing therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide aqueous slurry in which nano-composite materials formed of redox-capable nanoparticles and carbon materials coating the nanoparticles are dispersed so that the mean secondary particle size becomes 1 μm or smaller, and an inexpensive and simple method for producing the aqueous slurry. <P>SOLUTION: In the aqueous slurry, the nano-composite materials formed of redox-capable nanoparticles and carbon materials coating the nanoparticles in aqueous solution comprising tea components are dispersed where the mean secondary particle size of the dispersed nano-composite material is 1 μm or smaller. By the method for producing the aqueous slurry, raw material slurry comprising the redox-capable nanoparticles and carbon materials coating the nanoparticles is pulverized and the pulverized raw material slurry is mixed with the aqueous solution comprising the tea components. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a water slurry using a nanocomposite material composed of nanoparticles capable of oxidation-reduction and a carbon material covering the nanoparticles, and a method for producing the same.

  Powdered carbon materials are used in a wide variety of applications such as positive and negative electrodes in electrochemical electricity storage devices, conductive paints for antistatic purposes, and aqueous paints as coloring materials. International Publication No. 2007/044614 pamphlet (Patent Document 1) discloses a nanocomposite material composed of nanoparticles capable of oxidation-reduction and a carbon material covering the nanoparticles. However, the surface of the powdery carbon material is generally hydrophobic and difficult to disperse in water. Therefore, a slurry in which a carbon material is stably and uniformly dispersed in water and a method for producing the same have been desired.

  Genki Nakamura et al., “Green Tea Solution Individually Solubilizes Single-walled Carbon Nanotubes”, Chemistry Letters Vol. 36, No.9 (2007) p.1140-1141 (Non-Patent Document 1) includes representative carbon materials. In order to disperse the carbon nanotubes in water, a method is disclosed in which the carbon nanotubes are uniformly dispersed in water only by ultrasonic irradiation after the carbon nanotubes are added to the green tea aqueous solution.

International Publication No. 2007/044614 Pamphlet

Genki Nakamura et al., `` Green Tea Solution Individually Solubilizes Single-walled Carbon Nanotubes '', Chemistry Letters Vol. 36, No. 9 (2007) p.1140-1141

  However, the nanocomposite material forms a strong aggregate in terms of the production method, and it is difficult to disperse it in water with an average secondary particle size of 1 μm or less only by adding a tea component or the like.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to coat a nanoparticle capable of redox (hereinafter also simply referred to as “nanoparticle”) and the nanoparticle. An object is to provide a water slurry in which a nanocomposite material made of a carbon material is dispersed with an average secondary particle diameter of 1 μm or less, and a method capable of producing the water slurry by an inexpensive and simple method.

  The present invention relates to an average of dispersed nanocomposites in an aqueous slurry in which a nanocomposite composed of a redox-capable nanoparticle and a carbon material covering the nanoparticle is dispersed in an aqueous solution containing a tea component. The secondary particle diameter is 1 μm or less.

  In the water slurry of the present invention, the carbon material preferably forms a layer. In this case, the number of layers formed by the carbon material is more preferably 2 to 1000, the total thickness is 1 to 200 nm, and the diameter of the nanoparticles is more preferably 0.5 to 400 nm.

  The water slurry of the present invention has a weight reduction rate of 3% by weight or less when the nanocomposite reaches a temperature of 600 ° C. at a temperature increase rate of 10 ° C./min from room temperature in a nitrogen atmosphere. It is preferable.

  The nanocomposite material in the water slurry of the present invention is preferably obtained by a production method including the following steps (1) and (2) in this order.

(1) a step of polymerizing a carbon material precursor in the presence of nanoparticles capable of redox, and forming a carbon material intermediate on the surface of the nanoparticles;
(2) A step of carbonizing the carbon material intermediate to form a carbon material that covers the nanoparticles to produce a nanocomposite material.

  The present invention is also a method for producing the water slurry of the present invention described above, wherein a raw slurry containing a nanocomposite material comprising a redox-capable nanoparticle and a carbon material covering the nanoparticle is pulverized and pulverized. The present invention also provides a method for producing a water slurry in which the raw material slurry mixed with an aqueous solution containing a tea component is mixed.

  According to the present invention, a water slurry dispersed with an average secondary particle diameter of 1 μm or less, which is a water slurry using a nanocomposite material comprising a nanoparticle capable of redox and a carbon material covering the nanoparticle, Can be provided. Moreover, the method which can manufacture the said water slurry by a cheap and simple method can be provided.

The water slurry of the present invention is characterized in that nanocomposite particles are dispersed in water with an average secondary particle diameter of 1 μm or less, preferably 0.02 to 0.8 μm in the presence of a tea component. In this way, by realizing a water slurry in which nanocomposite particles are dispersed with an average secondary particle diameter of 1 μm or less, conductivity is improved when applied to electrode materials and conductive materials, filling properties and adhesion during coating film formation. Effects, such as improvement in hardness and hardness. Here, the “average secondary particle size” of the nanocomposite material dispersed in the water slurry means the particle size in which the nanocomposite material is actually dispersed in water. The aggregated particle diameter is shown. The average secondary particle size of such a nanocomposite can be calculated using a laser diffraction / scattering method. Specifically, a laser diffraction / scattering type particle size distribution measuring device such as a microtrack HRA (Leads and North wrap), SALD series (manufactured by Shimadzu Corporation), LS series (manufactured by Beckman Coulter), etc. are added to the water slurry of the present invention, diluted and adjusted to a predetermined concentration, and then measured. A particle size distribution curve is obtained and indicates a value calculated as a ₅₀ % by weight equivalent particle diameter (D ₅₀ ).

  The nanocomposite material used in the present invention has a redox-capable nanoparticle and a carbon material that covers a part or all of the nanoparticle in a bag shape, that is, about 0.5 nm to 800 nm. The typical shape is granular. Here, “redox capable” of the nanoparticles in the nanocomposite means that the metal atoms constituting the nanoparticles can exchange electrons. The ability of the nanoparticles to be redoxed in this way has the advantage of promoting the polymerization of the carbon material precursor and / or the formation and carbonization of the carbon material intermediate.

  The nanocomposite material in the present invention preferably has the following requirements (A), and more preferably has the following requirements (B), (C) and (D).

(A) The carbon material forms a layer,
(B) The number of layers formed by the carbon material is 2-1000, preferably 2-100,
(C) The total thickness of the layer formed by the carbon material is 1 to 200 nm, preferably 1 to 20 nm.
(D) The diameter of the nanoparticles is 0.5 to 400 nm, preferably 0.5 to 200 nm.

  Here, the carbon material is preferably a graphite-like layer, that is, a multilayer. This layer may be curved or bent along the surface of the nanoparticles.

  Moreover, when the diameter of the nanoparticles in the nanocomposite material is less than 0.5 nm, it is difficult to suppress aggregation of the nanoparticles in the nanoparticle production process described later. Moreover, when exceeding 400 nm, the particle diameter as a nanocomposite material also including the layer of a carbon material will become enlarged, and there exists a possibility that a suitable effect may not be acquired with respect to uses, such as an electrode material and a conductive paint. The diameter of the nanoparticles is more preferably in the range of 0.5 to 50 nm. Here, the nanoparticle in the present invention is not limited to an equiaxed shape including a substantially spherical shape, that is, a particle having an aspect ratio of about 1, but also includes a rod shape, a cylindrical shape, a prism shape, and the like having a major axis and a minor axis. When the nanoparticles have a major axis and a minor axis, it is sufficient that at least the minor axis is within the above range. The nanoparticles in the present invention are preferably equiaxed particles including a substantially spherical shape.

  In the nanocomposite material, the shape, the number of layers when the carbon material forms a layer, the total thickness of the carbon layer, and the diameter of the nanoparticles can be measured by a transmission electron microscope (TEM). In the nanocomposite material, the shape and particle size of the carbon material formed around the nanoparticles are largely dependent on the shape and particle size of the nanoparticles.

  As such a nanocomposite material in the present invention, a material obtained by a production method including the following steps (1) and (2) in this order can be suitably used.

(1) a step of polymerizing a carbon material precursor in the presence of nanoparticles capable of redox, and forming a carbon material intermediate on the surface of the nanoparticles;
(2) A step of carbonizing the carbon material intermediate to form a carbon material that covers the nanoparticles to produce a nanocomposite material.

  First, in the step (1), nanoparticles capable of redox are produced as follows. That is, using one or more nanoparticle precursors and one or more dispersing agents, the nanoparticle precursors and the dispersing agent are reacted or combined to form a precursor complex. Generally, the nanoparticle precursor and the dispersant are dissolved in an appropriate solvent or dispersion medium (the one obtained at this time is referred to as “composite solution”) or dispersed (the one obtained at this time is “ This precursor complex is formed by combining the nanoparticle precursor and the dispersant.

  The nanoparticle precursor is not particularly limited as long as it promotes polymerization of a carbon material precursor and / or carbonization of a carbon material intermediate, which will be described later. Specifically, lithium, sodium, potassium as constituent elements Alkali metal elements such as calcium and magnesium, Group 4 elements such as titanium and zirconium, Group 5 elements such as vanadium and niobium, Group 6 elements such as chromium, molybdenum and tungsten, Copper Group 11 elements such as silver and gold, Group 12 elements such as zinc and cadmium, Group 13 elements such as aluminum, gallium and indium, Group 14 elements such as silicon, germanium, tin and lead, and manganese And transition metal elements such as iron, cobalt, nickel, palladium, and platinum. Examples of the nanoparticle precursor include a simple metal composed of these elements, an alloy including two or more of these elements, a metal compound including one or more of these elements, or a mixture thereof. The nanoparticle precursor preferably contains one or more elements selected from the group consisting of manganese, iron, cobalt, and nickel because the valence can be easily changed. The polymerization of the carbon material precursor and / or It is more preferable that iron is included from the reason that carbonization of the carbon material intermediate can be further promoted.

  The precursor complex includes one or more dispersants. This dispersant is selected from those that promote the production of nanoparticles having the desired stability, size, and uniformity. The dispersant includes various organic molecules, polymers, oligomers and the like. This dispersant is used after being dissolved or dispersed in a suitable solvent or dispersion medium.

  As the solvent or dispersion medium used for dissolving or dispersing the precursor complex including the nanoparticle precursor and the dispersing agent, various known solvents or dispersion media can be used. Preferred examples of such a solvent or dispersion medium include water, methanol, ethanol, n-propanol, isopropyl alcohol, acetonitrile, acetone, tetrahydrofuran, ethylene glycol, dimethylformamide, dimethyl sulfoxide, and methylene chloride. These may be used as a mixture.

  The precursor complex dissolved or dispersed in the solvent or dispersion medium described above is considered to be a complex obtained from a nanoparticle precursor and a dispersant surrounded by solvent molecules or dispersion medium molecules. After the precursor complex is produced in the complex solution or the complex suspension, the dried precursor complex can be obtained by removing the solvent or the dispersion medium by drying or the like. In addition, the dried precursor complex can be returned to a solution or suspension by adding an appropriate solvent or dispersion medium.

  Thus, when the nanoparticle precursor and the dispersant are dissolved or dispersed in a solvent or dispersion medium to prepare a complex solution or a complex suspension, in the complex solution or the complex suspension, The molar ratio of the dispersant to the nanoparticle precursor can be controlled.

  When preparing a complex solution or a complex suspension as described above, the dispersant can promote the formation of nanoparticles having a very small and uniform particle size. In general, the nanoparticle precursor is formed in a size of 1 μm or less in the presence of a dispersant. Preferably it is 500 nm or less, More preferably, it is 50 nm or less.

  In the complex solution or complex suspension, an additive for promoting the formation of nanoparticles may be included. As an additive, for example, an inorganic acid or a basic compound can be added. Examples of the inorganic acid include hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid, and examples of the inorganic base compound include sodium hydroxide, potassium hydroxide, calcium hydroxide, and ammonium hydroxide.

  Moreover, in order to adjust pH in the range of 8-13, Preferably it is 10-11, you may add a basic substance (for example, ammonia aqueous solution) to a composite solution or composite suspension. Since the nanoparticle precursor can be finely separated by adjusting the complex solution or the complex suspension to a high pH value within the above-described range, the pH of the complex solution or the complex suspension is Affects the particle size of the nanoparticles.

  Further, a solid substance for promoting the formation of nanoparticles may be added to the complex solution or the complex suspension. For example, an ion exchange resin as a solid material can be added during nanoparticle formation. Solid material can be removed from the final complex solution or complex suspension by simple manipulations.

  Typically, nanoparticles are obtained by mixing the complex solution or complex suspension for 0.5 hours to 14 days. The mixing temperature is about 0 to 200 ° C. Mixing temperature is an important factor affecting the particle size of the nanoparticles.

  When iron is used as the nanoparticle precursor, typical examples of the nanoparticle precursor include iron compounds such as iron chloride, iron nitrate, and iron sulfate. The nanoparticle precursor becomes nanoparticles by reacting with or binding to the dispersant. These compounds are often dissolved in an aqueous solvent. By-products are formed by the formation of nanoparticles using metal salts. A typical by-product is hydrogen gas that is generated when nanoparticles are prepared using metal. In a typical embodiment, the nanoparticles are activated in the mixing step or are further reduced with hydrogen.

  The nanoparticles are preferably formed as a suspension of stably active nanoparticles. The aggregation of nanoparticles is suppressed by the stability of the nanoparticles. Even if some or all of the nanoparticles settle, they are easily resuspended by mixing.

  The nanoparticles obtained as described above can serve as a catalyst for promoting the polymerization of the carbon material precursor and / or the formation of the carbon material intermediate in the step (1).

The carbon material precursor used in step (1) is preferably one that can disperse nanoparticles. By dispersing the nanoparticles and polymerizing the carbon material precursor in the presence of the nanoparticles, a carbon material intermediate is formed on the surface of the nanoparticles. Organic materials suitable as the carbon material precursor include benzene and naphthalene derivatives having one or more aromatic rings in the molecule and a functional group for polymerization. Examples of functional groups for polymerization include COOH, C═O, OH, C═C, SO ₃ , NH ₂ , SOH, and N═C═O.

  Preferred carbon material precursors include resorcinol, phenolic resin, melamine-formamide gel, polyfurfuryl alcohol, polyacrylonitrile, sugar, petroleum pitch and the like.

  The nanoparticles are mixed with the carbon material precursor such that the carbon material precursor polymerizes on its surface. If the nanoparticles are catalytically active, they can play a role in initiating and / or promoting the polymerization of the carbon material precursor in the vicinity of the nanoparticles.

  The amount of the nanoparticles relative to the carbon material precursor may be set so that the carbon material precursor uniformly forms the maximum amount of the carbon material intermediate. The amount of nanoparticles also depends on the type of carbon material precursor used. The molar ratio of the carbon material precursor to the nanoparticles is preferably 0.1: 1 to 100: 1, more preferably 1: 1 to 30: 1. This molar ratio, the type of nanoparticles, and the particle size affect the thickness of the resulting carbon material.

  The mixture of the nanoparticles and the carbon material precursor is sufficiently aged until the carbon material intermediate is sufficiently formed on the surface of the nanoparticles. The time required to form the carbon material intermediate depends on the temperature, the type of nanoparticles, the concentration of nanoparticles, the pH of the solution, and the type of carbon material precursor used. In addition, by adding ammonia for pH adjustment, the rate of polymerization is increased, the amount of crosslinking between the carbon material precursors is increased, and there are cases where polymerization can be performed effectively.

  Carbon material precursors that can be polymerized by heat usually undergo polymerization as the temperature rises. The temperature at which the carbon material precursor is polymerized is preferably 0 to 200 ° C, more preferably 25 to 120 ° C.

  Specifically, when resorcinol-formaldehyde gel (when iron particles are used and the suspension pH is 1 to 14) is used as the carbon material precursor, the optimum polymerization condition is 0 to 90 ° C. The aging time is 1 to 72 hours.

  In step (2), the carbon material intermediate obtained in step (1) is carbonized to form a carbon material to obtain a nanocomposite material. Carbonization is usually performed by firing. Typically, the calcination is performed at a temperature of 500 to 2500 ° C, preferably 1000 to 2500 ° C. At the time of firing, oxygen atoms and nitrogen atoms in the carbon material intermediate are released, and rearrangement of carbon atoms occurs to form a carbon material. The carbon material thus formed is preferably graphite-like layered (multilayered), but the number of layers can be controlled by the type, thickness and firing temperature of the carbon material intermediate. The thickness of the carbon material (layer thickness) in the nanocomposite material can also be controlled by adjusting the progress of carbonization of the carbon material precursor and / or the carbon material intermediate.

  The nanocomposite material obtained by the above method has an average secondary particle diameter of 3 to 100 μm when suspended as a slurry in water. The content of the nanocomposite material in the slurry is 1 part by weight or more and less than 50 parts by weight with respect to 100 parts by weight of water. Water is used as a solvent for dispersing the nanocomposite, and a water-soluble solvent such as ethanol, methanol, acetone, or ethyl acetate may be added as necessary. The amount of the water-soluble solvent added at this time is preferably in the range of 0.1 to 20 parts by weight with respect to 100 parts by weight of water.

In addition, the nanocomposite material obtained by the above method usually has a BET specific surface area (measured by a nitrogen adsorption method according to the method defined in JIS-Z-8830) in the range of 80 to 400 m ² / g. Yes, preferably in the range of 100-200 m ² / g. When the nanocomposite material has a BET specific surface area of less than 80 m ² / g, it suggests that the primary particles of the nanocomposite material are sintered, making it difficult to disperse by pulverization described later. There is a fear. On the other hand, when the BET specific surface area of the nanocomposite material exceeds 400 m ² / g, the viscosity of the water slurry obtained by pulverization described later tends to be remarkably high.

  The content of the nanoparticles in the nanocomposite material is not particularly limited, but is usually in the range of 1000 to 200000 ppm in terms of metal atoms.

  The nanocomposite material in the present invention preferably has a weight reduction rate of 3% by weight or less when the temperature is increased from room temperature at a temperature increase rate of 10 ° C./min and reaches 600 ° C. in a nitrogen atmosphere. More preferably, it is 2% by weight or less. As shown in Comparative Example 4 described later, when the weight reduction rate exceeds 3% by weight, the tea component is dispersed without adding. However, when the weight reduction rate is 3% by weight or less, the dispersibility is poor, and the dispersibility is remarkably improved by the addition of the tea component, and the present invention can be applied particularly preferably.

  The present invention exists in the state where the nanocomposite is dispersed with an average secondary particle diameter of 1 μm or less from the raw material slurry in a state where the average secondary particle diameter is 3 to 100 μm and the nanocomposite is dispersed in water. A method for producing a water slurry for obtaining the water slurry of the present invention is also provided. The method for producing a water slurry of the present invention comprises a raw material slurry containing a nanocomposite material composed of nanoparticles capable of oxidation and reduction and a carbon material covering the nanoparticles, and contains the pulverized raw material slurry and a tea component. It is characterized by mixing with an aqueous solution. In this specification, the “raw material slurry” refers to a water slurry for producing the water slurry of the present invention, which contains a nanocomposite material but does not contain a tea component.

  The raw slurry in which the nanocomposite material is suspended can be pulverized using a pulverizer such as a ball mill, a high-speed rotary pulverizer, or a medium stirring mill. As a medium used for pulverization, a known medium such as alumina or zirconia can be used.

  Although the time which grind | pulverizes the said raw material slurry with a grinder is not restrict | limited in particular, Preferably it is 0.1 to 5 hours. If the pulverization time is less than 0.1 hour, it may be difficult to apply sufficient pulverization energy to weaken strong aggregation between the nanocomposites. On the other hand, even if the pulverization time is longer than 5 hours, an effect commensurate with the treatment time cannot be obtained.

  In the method for producing a water slurry of the present invention, an aqueous solution containing a tea component is mixed with the pulverized raw material slurry. Here, the “tea component” in the present invention refers to tea leaves and / or stems of oolong tea, green tea, black tea, etc., water, water-containing ethanol, ethanol, water-containing methanol, methanol, acetone, ethyl acetate, etc. at a predetermined temperature. An extract extracted by contacting with a water-soluble solvent. The solvent used for extraction of the tea component may be a solvent in which two or more selected from the above are mixed. The extraction amount of the tea component is influenced by the blending ratio of the solvent and tea leaves and / or tea stems, but is usually 0.01 to 5 parts by weight of tea leaves and / or tea stems with respect to 100 parts by weight of the solvent. The tea component is preferably extracted until the extraction amount of the tea component reaches equilibrium.

  The tea components obtained by such extraction include “tea science” edited by Keiichiro Muramatsu, P.A. 85-93, for example, polyphenols such as catechins (catechin, gallocatechin, epicatechin, epigallocatechin, catechin gallate, epicatechin gallate, gallocatechin gallate, epigallocatechin gallate) and tannins Mainly contained.

  The amount of the aqueous solution containing the tea component is preferably in the range of 1 to 200 parts by weight and more preferably in the range of 5 to 100 parts by weight with respect to 100 parts by weight of the ground slurry after pulverization. When the mixing amount of the aqueous solution containing the tea component is less than 1 part by weight with respect to 100 parts by weight of the raw material slurry after pulverization, sufficient tea component cannot be supplied to disperse the nanocomposite material to a desired particle size. This is because the dispersed particle size in water tends to be large, and when it exceeds 200 parts by weight, the effect corresponding to the amount added cannot be obtained.

  After pulverizing the raw slurry containing the nanocomposite according to the production method of the present invention, the nanocomposite has an average secondary particle size in the aqueous solution containing the tea component by adding an aqueous solution containing the tea component. A water slurry existing in a dispersed state at 1.0 μm or less can be produced. On the other hand, even if the tea component is added to the raw slurry containing the nanocomposite material before pulverization and pulverized, the nanocomposite material is present in a dispersed state with an average secondary particle size of 1.0 μm or less. A water slurry cannot be obtained.

  The application of the water slurry of the present invention is not particularly limited, but can be suitably applied to the same application as a conventionally known water slurry containing carbon black, and the water slurry is applied to a substrate, or resin or By compounding with inorganic powder and other water slurry, electrode materials and conductive materials for lithium secondary batteries, non-aqueous capacitors and fuel cells, conductive paints, hard coat materials, water-based paints, pneumatic tires, etc. It can be applied to a wide range of applications such as wet masterbatch for manufacturing rubber products.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in detail, this invention is not limited to these.

<Example 1>
BET specific surface area 117 m ² / g, average secondary particle diameter 16 μm, Fe content 8440 ppm, under nitrogen atmosphere, the temperature was increased from room temperature at a heating rate of 10 ° C./min. 30 parts by weight of a nanocomposite powder having a rate of 0.8% by weight was added to 970 parts by weight of pure water and stirred to obtain a raw material slurry. 100 parts by weight of this raw material slurry and 150 ml of zirconia beads having a diameter of 0.1 mm were charged into a wet medium mill (sand grinder, manufactured by IMEX (internal volume: 400 ml)), and pulverized at a rotational speed of 2000 rpm for 60 minutes. After pulverization, the zirconia beads and the raw material slurry were sieved with a sieve having an opening of 75 μm.

  3 g of commercially available dried tea leaves (Kuki tea, manufactured by Waki Seika Tea House Co., Ltd.) were spread on a SUS sieve having an opening of 850 μm, and 1 L of pure water at 75 ° C. was poured to extract tea components (extraction time: 3 minutes). Thereafter, the solid content was removed with a SUS sieve having an opening of 42 μm to prepare an aqueous solution containing a tea component. In addition, the liquid color of this aqueous solution was L value: 95.8, a value: -0.9, b value: 5.15.

  The raw material slurry and the aqueous solution containing the tea component were mixed at a weight ratio of 1: 1, and subjected to ultrasonic treatment for 5 minutes using a 300 W ultrasonic generator. The average secondary particle diameter of the nanocomposite material in the obtained water slurry was 0.50 μm.

The average secondary particle diameter described above is adjusted by adding a water slurry to water and diluting it to a predetermined concentration using a laser scattering particle size distribution analyzer (Microtrac HRA, manufactured by Leeds and Northrup). The particle size distribution curve is measured, and the value calculated as the ₅₀ % by weight equivalent particle diameter (D ₅₀ ) is indicated. Moreover, the BET specific surface area mentioned above points out the value computed by the nitrogen adsorption method according to the method prescribed | regulated to JIS-Z-8830. Moreover, the liquid color (L value, a value, b value) of the aqueous solution containing the tea component mentioned above puts the said aqueous solution in a glass cell, and a colorimetric color difference meter (ZE-2000, Nippon Denshoku Industries Co., Ltd. make). The value obtained by measuring twice using and calculating the arithmetic average of the values.

The weight reduction rate mentioned above was measured using a thermogravimetric differential thermal simultaneous measurement apparatus (TG / DTA300, manufactured by Seiko Electronics), a nitrogen flow rate of 200 ml / min, a nanocomposite powder of 8.0 mg, and α-Al ₂ O ₃ as a reference. 10 mg each in a platinum cell, heated from room temperature to 800 ° C. at a rate of 10 ° C./min without a top cover, measured TG curve, and the weight loss from the room temperature to 600 ° C. Based on calculations.

<Comparative Example 1>
A water slurry containing the nanocomposite material was prepared in the same manner as in Example 1 except that the aqueous solution containing the tea component was not added. The water slurry and pure water were mixed at a weight ratio of 1: 1, and sonicated for 5 minutes with a 300 W ultrasonic generator. The average secondary particle diameter (measured in the same manner as in Example 1) of the nanocomposite material in the obtained water slurry was 6.8 μm.

<Comparative Example 2>
After mixing 30 parts by weight of the nanocomposite powder used in Example 1 with 970 parts by weight of the aqueous solution containing the tea component prepared in Example 1, the nanocomposite material was pulverized by the same method as in Example 1 to obtain the nanocomposite material. A water slurry containing was obtained. The water slurry and pure water were mixed at a weight ratio of 1: 1, and sonicated for 5 minutes with a 300 W ultrasonic generator. The average secondary particle diameter (measured in the same manner as in Example 1) of the nanocomposite material in the obtained slurry was 6.2 μm.

<Comparative Example 3>
30 parts by weight of the nanocomposite powder used in Example 1 was added to 970 parts by weight of pure water, and an aqueous solution containing the same tea component as in Example 1 was added to the water slurry obtained by stirring at a weight ratio of 1: 1. The mixture was mixed and sonicated for 5 minutes with a 300 W ultrasonic generator. The average secondary particle diameter of the average secondary particle diameter of the nanocomposite in the obtained water slurry was 14 μm.

  The results are shown in Table 1.

<Comparative example 4>
BET specific surface area 106 m ² / g, average secondary particle diameter 16 μm, Fe content 7444 ppm, weight loss rate when reaching 600 ° C. when heated at 10 ° C./min under nitrogen atmosphere is 3.7 Grinding was carried out under the same conditions as in Example 1 except that the weight percent nanocomposite powder was used to obtain an aqueous slurry containing no tea component.

  Sonication was performed with a 300 W ultrasonic generator for 5 minutes. The average secondary particle diameter of the nanocomposite material in the obtained water slurry was 0.47 μm.

It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

Claims (6)

In an aqueous slurry in which a nanocomposite material composed of nanoparticles capable of oxidation and reduction and a carbon material covering the nanoparticles is dispersed in an aqueous solution containing a tea component,
A water slurry in which the average secondary particle diameter of the dispersed nanocomposite is 1 μm or less.   The water slurry according to claim 1, wherein the carbon material forms a layer.   The water slurry according to claim 2, wherein the number of layers formed by the carbon material is 2 to 1000, the total thickness is 1 to 200 nm, and the diameter of the nanoparticles is 0.5 to 400 nm.   2. The water according to claim 1, wherein the nanocomposite material has a weight reduction rate of 3% by weight or less when the temperature is increased from room temperature to a temperature increase rate of 10 ° C./min and reaches 600 ° C. in a nitrogen atmosphere. slurry. The water slurry according to claim 1, wherein the nanocomposite material is obtained by a production method including the following steps (1) and (2) in this order.
(1) a step of polymerizing a carbon material precursor in the presence of nanoparticles capable of redox, and forming a carbon material intermediate on the surface of the nanoparticles;
(2) A step of carbonizing the carbon material intermediate to form a carbon material that covers the nanoparticles to produce a nanocomposite material. A method for producing the water slurry according to claim 1,
Production of a water slurry in which a raw material slurry containing a nanocomposite material composed of nanoparticles capable of oxidation and reduction and a carbon material covering the nanoparticles is pulverized, and the pulverized raw material slurry and an aqueous solution containing a tea component are mixed. Method.