JP4715998B2 - Composite metal compound particles with controlled particle size distribution - Google Patents

Description

  The present invention relates to composite metal compound particles composed of a central portion and a coating layer around the central portion, the central portion is composed of a compound of a rare earth metal, the coating layer is composed of a compound of a metal other than the rare earth, and the particle size distribution is controlled. It is related with the composite metal compound particle made.

  Conventionally, the surface of metal oxide particles, metal particles, organic resin particles and the like coated with other materials is known. For example, the surface of titanium oxide particles coated with iron oxide and titanium oxide, the surface of zinc oxide particles coated with silica, the surface of iron oxide particles coated with silica, alumina, etc., the surface of mica particles Iron oxide, titanium oxide layered coating, copper particle surface coated with copper monoxide, polystyrene particle or polyethylene particle surface coated with silica, titanium oxide, etc., metal fine particles (Au, Ag, Ni, Cu, etc.) are coated with protective colloids. These composite particles are widely used in fields such as paints, cosmetics, and electronic materials.

  Examples of the coating method include a hydrolysis method, a sol-gel method, an electroless plating method, a CVD method, and a sputtering method. These coating methods are selected according to the characteristics of the particles that are the central part before coating, the characteristics of the composite particles after coating, and the like.

  Examples of the purpose of coating the core (core) particles with other materials include, for example, the purpose of protecting the central particles (for example, imparting oxidation resistance, touch resistance, solvent resistance, etc.) There is a purpose to develop a new function that cannot be achieved only by the particles. As an example of the latter, for example, the center part and the covering part are made of materials having different refractive indexes to control the light reflection characteristics, and the composite material is used as a pigment, a lens, or the like.

  The shape of the composite particles varies from spherical particles to those having an aspect ratio, and the size of the spherical particles ranges from several nanometers to several micrometers. In particular, in the electronic material field and the ceramics field, it is important to provide a high-quality functional material by using a composite material having a uniform particle size (that is, a controlled particle size distribution). In particular, in order to form a fine regular structure by utilizing the self-organization of composite particles and obtain a so-called photonic crystal, it is important that the particle diameters of the composite particles are uniform.

As for the particle size distribution of composite particles, polystyrene particles, some silica particles, etc. have a standard deviation within 15% (preferably within 10%) of the average particle diameter. In particular, it is not known that the standard deviation is within 15% of the average particle size. Rare earth oxide fine particles having a relatively uniform particle size are reported, for example, in Non-Patent Document 1, which means that the standard deviation of the particle size distribution exceeds 15% of the average particle size. Moreover, it is not known that a composite metal compound obtained by coating the surface of a rare earth oxide with another material has a standard deviation of the particle size distribution controlled within 15% of the average particle diameter.
Bulletin of. The Chemical Society of Japan, 1992, p1388-1391 “Effect of reaction temperature on the formation of fine particles of basic yttrium carbonate by homogeneous precipitation”

  The present invention is a composite metal compound particle composed of a central portion and a coating layer around the central portion, wherein the central portion is composed of a compound of a rare earth metal, the coating layer is composed of a compound of a metal other than the rare earth, and a standard particle size distribution The main object is to provide composite metal compound particles that contribute to the provision of high-quality functional materials whose deviation is within 15% of the average particle diameter.

  As a result of intensive studies to achieve the above object, the present inventor, according to a specific manufacturing method, is a composite metal compound particle composed of a central portion and a surrounding coating layer, the central portion being a rare earth It was found that composite metal compound particles comprising a metal compound, the coating layer comprising a metal compound other than rare earth, and having a standard deviation of the particle size distribution within 15% of the average particle diameter can be produced, and the present invention has been completed. It was.

That is, the present invention relates to the following composite metal compound particles and a method for producing the same.
1. A composite metal compound particle composed of a central portion and a surrounding coating layer,
(1) The central portion is composed of at least one selected from the group consisting of rare earth metal oxides, hydroxides and carbonates,
(2) The coating layer is made of at least one selected from the group consisting of oxides, hydroxides and carbonates of metals other than rare earths,
(3) The average particle size of the composite metal compound particles is 35 to 600 nm,
(4) The composite metal compound particles, wherein the standard deviation of the particle size distribution of the composite metal compound particles is within 15% of the average particle size.
2. Item 1 wherein the rare earth metal is at least one selected from the group consisting of Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. The composite metal compound particle as described.
3. Item 3. The composite metal compound particle according to Item 1 or 2, wherein the metal other than the rare earth is at least one selected from the group consisting of Al, Ga, In, Si, Ti, Zr, Sn, Ge, Ta, and Nb.
4). Item 4. The composite metal compound particle according to any one of Items 1 to 3, wherein the central part is a spherical particle having an average particle size of 30 to 500 nm.
5. Item 5. The composite metal compound particle according to any one of Items 1 to 4, wherein the coating layer has an average thickness of 5 to 100 nm.
6). Item 6. The composite metal compound particle according to any one of Items 1 to 5, wherein the central portion is made of an oxide of a rare earth metal, and the coating layer is made of an oxide of a metal other than the rare earth.
7). 7. An optical material comprising the composite metal compound particle according to any one of items 1 to 6.
8). A method for producing composite metal compound particles, comprising the following steps;
(1) An aqueous solution containing urea and at least one selected from the group consisting of chlorides, nitrates and sulfates of rare earth metals, and containing 10 mol or more of urea with respect to 1 mol of the rare earth metal, and 0% of the rare earth metal. Step 1 of obtaining spherical particles comprising at least one selected from the group consisting of rare earth metal oxides, hydroxides and carbonates by heating an aqueous solution containing 0.001 to 0.01 mol / L. ,
(2) Mixing a dispersion containing the spherical particles and having a pH of 6 to 11 with at least one aqueous solution selected from the group consisting of alkoxides, chlorides, nitrates and sulfates of metals other than rare earths, Step 2 of forming a coating layer made of at least one selected from the group consisting of oxides, hydroxides and carbonates of metals other than rare earths on the surface of the spherical particles by decomposing.

Hereinafter, the present invention will be described in detail.

1. Composite metal compound particles The composite metal compound particles of the present invention are composite metal compound particles composed of a central portion and a surrounding coating layer,
(1) The central portion is composed of at least one selected from the group consisting of rare earth metal oxides, hydroxides and carbonates,
(2) The coating layer comprises at least one selected from the group consisting of oxides, hydroxides and carbonates of metals other than rare earths,
(3) The average particle size of the composite metal compound particles is 35 to 600 nm,
(4) The rare earth metal is not particularly limited, and is characterized in that the standard deviation of the particle size distribution of the composite metal compound particles is within 15% of the average particle size, but Y, La, Ce, Pr, Nd, Pm, Sm At least one selected from the group consisting of Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu is preferred. Among these, Eu, Sm, Gd, Dy, Ho, Er, etc. are particularly suitable when the composite metal compound particles are used as an optical material (especially a lens) because the refractive index is large (described in order of decreasing refractive index). is there.

  The central portion is composed of at least one spherical particle selected from the group consisting of the rare earth metal oxides, hydroxides and carbonates. The central portion may be a spherical particle made of a composite, for example, a basic carbonate which is a composite of hydroxide and carbonate. Among these, when the composite metal compound particles are used as an optical material (particularly a lens), an oxide is preferable from the viewpoint of a large refractive index.

  The metal other than the rare earth is not particularly limited, but at least one selected from the group consisting of Al, Ga, In, Si, Ti, Zr, Sn, Ge, Ta, and Nb is preferable. Among these, when using composite metal compound particles as an optical material (especially a lens), Ti, Zr, Si and the like are preferable. From the viewpoint of uniforming the particle size of the composite metal compound particles, Si that is easy to control hydrolysis is used. preferable. For example, when composite metal compound particles are used as a photonic crystal production material, Si is preferable from the viewpoint of easy particle size control.

  The coating layer is made of at least one selected from the group consisting of oxides, hydroxides and carbonates of metals other than the rare earths described above. The coating layer may be a composite, for example, a basic carbonate that is a composite of hydroxide and carbonate. Among these, when the composite metal compound particles are used as an optical material (particularly a lens), an oxide is preferable from the viewpoint of high protection at the center.

  When both the central portion and the coating layer are made of an oxide, the composite metal compound particles can be suitably used as an optical material (particularly, a lens) from the viewpoint of refractive index and the central protective property.

  The average particle size of the composite metal compound particles may be 35 to 600 nm, and more preferably 60 to 400 nm.

  The average particle size of the central particles is preferably from 30 to 500 nm, particularly preferably from 50 to 300 nm.

  The average thickness of the coating layer is preferably 5 to 100 nm, and more preferably 15 to 50 nm.

  In addition, the average particle diameter in this specification is an average value of particle diameters measured by arbitrarily selecting 100 target particles by observing SEM images of target particles in the presence of polystyrene particles of 210 nm.

  The standard deviation of the particle size distribution of the composite metal compound particles may be within 15% of the average particle diameter, and particularly preferably within 10%.

  The standard deviation of the particle size distribution in the present specification is a value measured by a particle size distribution measuring device “DLS-7000” (manufactured by Otsuka Electronics Co., Ltd.) using a dynamic light scattering method.

  The composite metal compound particles of the present invention in which the standard deviation of the particle size distribution is controlled within 15% of the average particle size, particularly within 10%, are suitable in the field of electronic materials, ceramics, etc. Can be used for

  For example, a composite metal compound material can be used as an optical material by setting materials constituting the central portion and the covering portion to materials having different refractive indexes. The combination of the material of the center portion and the coating layer is selected in consideration of the difference in refractive index, the stability of the composite metal compound particles (including dispersion stability), and the like.

Specifically, for example, when Gd ₂ O ₃ is used as the central portion and SiO ₂ is used as the coating layer, the refractive index of the central portion is larger than the refractive index of the coating layer, and an optical material (particularly a lens) ). Moreover, since the coating layer is composed of SiO 2 _(oxide), a high performance to protect the heart. The lens can be applied as a large-capacity microsphere lens, and can also be applied as a near-field microsphere probe.

  On the other hand, the composite metal compound particles of the present invention can be used even when dispersed in a dispersion medium. For example, there are applications as an optical pigment that utilizes the difference in refractive index of the particle surface, and applications that form so-called photonic crystals by forming a fine regular structure by utilizing self-organization of particles. Since the composite metal compound particle of the present invention has a coating layer that protects the central portion, it can be used without being dissolved even in a region where the pH of the dispersion medium is lower than when the central portion is used alone. Examples of the dispersion medium that can be used include alcohol solvents such as methanol, ethanol, and isopropanol, and glycolic solvents such as ethylene glycol monoethyl ether and ethylene glycol monobutyl ether.

  When the composite metal compound particles are used in the state of a dispersion, the surface of the coating layer may be treated to increase the surface charge for the purpose of improving dispersibility. For example, polar groups (such as sulfate radicals) may be added to the surface of the coating layer, or the surface of the coating layer may be modified using a dispersant. In addition, the dispersibility of the composite metal compound particles may be improved by blending an acrylic or carboxy dispersant in the dispersion medium.

2. Manufacturing method of composite metal compound particle The composite metal compound particle of this invention can be suitably manufactured with the manufacturing method containing the following process 1 and 2, for example.
(1) An aqueous solution containing urea and at least one selected from the group consisting of chlorides, nitrates and sulfates of rare earth metals, and containing 10 mol or more of urea with respect to 1 mol of the rare earth metal, and 0% of the rare earth metal. Step 1 of obtaining spherical particles comprising at least one selected from the group consisting of rare earth metal oxides, hydroxides and carbonates by heating an aqueous solution containing 0.001 to 0.01 mol / L. ,
(2) Mixing a dispersion containing the spherical particles and having a pH of 6 to 11 with at least one aqueous solution selected from the group consisting of alkoxides, chlorides, nitrates and sulfates of metals other than rare earths, Step 2 of forming a coating layer made of at least one selected from the group consisting of oxides, hydroxides and carbonates of metals other than rare earths on the surface of the spherical particles by decomposing.

  In step 1, spherical particles made of at least one selected from the group consisting of oxides, hydroxides and carbonates of rare earth metals as the central part are produced.

  The aqueous solution to be heated in Step 1 contains at least one selected from the group consisting of rare earth metal chlorides, nitrates and sulfates (hereinafter referred to as “rare earth-containing raw material”) and urea.

  As the rare earth metal, those described above can be used. The aqueous solution contains 10 mol or more of urea, preferably 10 to 100 mol, more preferably about 15 to 100 mol with respect to 1 mol of rare earth metal. The aqueous solution contains rare earth metal in a proportion of 0.001 to 0.01 mol / L, preferably 0.003 to 0.007 mol / L. When the ratio of urea is less than 10 mol, it may be difficult to obtain spherical particles. When the content ratio of the rare earth metal exceeds 0.01 mol / L, it may be difficult to obtain spherical particles or the particle size distribution may be increased.

  By heating the aqueous solution, urea is decomposed into ammonia and carbon dioxide gas, and these react with the rare earth-containing raw material, so that they are selected from the group consisting of oxides, hydroxides and carbonates of rare earth metals. At least one kind of spherical particles is obtained.

  This reaction is referred to as a homogeneous precipitation method. Due to the decomposition of urea, the pH of the reaction solution rises uniformly, and the decomposition products ammonia (hydroxide ions) and carbon dioxide (carbonate ions) react with the rare earth-containing raw material, and the pH is in the range of 6-11. Spherical particles mainly composed of at least one of hydroxide, carbonate and basic carbonate are generated and grown, and are precipitated according to the solubility product. Note that the smaller the rare earth metal ion radius, the higher the pH at which precipitation begins.

  The heating conditions are not particularly limited as long as the reaction proceeds, but the heating temperature is preferably room temperature (about 25 ° C.) to about 90 ° C., more preferably about 60 to 85 ° C. The heating time can be appropriately adjusted according to the heating temperature, but is preferably 1 to 24 hours, particularly 2 to 10 hours so that urea is sufficiently decomposed.

  In the uniform precipitation method, it is important to prepare conditions under which the reaction occurs uniformly in any part of the reaction solution in order to control the standard deviation of the particle size distribution of the composite metal particles within 15% of the average particle size. For that purpose, it is preferable that the reaction vessel also has a condition in which no particles are generated on the side wall of the vessel or the stirring blade. That is, the container and the stirring blade are made of a water-repellent material (for example, polytetrafluoroethylene (PTFE); thermoplastic fluororesin (PFA) made of a copolymer of tetrafluoroethylene (TFE) and perfluoroalkoxyethylene). It is preferable to make it close to the property of repelling the wet property. Thereby, uniform particles can be obtained by generating and growing particle nuclei (seeds) only in the reaction solution. As the particle diameter of the spherical particles, those described above are obtained.

  The state of particle growth in the uniform precipitation method can be confirmed, for example, by observing the transmitted light / reflected light of the reaction solution over time. Since the transmittance and reflectance change according to the growth of particles, the degree of growth can be confirmed by confirming the color tone change of transmitted light and reflected light.

  The spherical particles obtained in step 1 may be used in step 2 as they are, such as hydroxide, carbonate, basic carbonate, etc., and may be converted to oxides by firing in the range of 400 to 600 ° C.

  In step 2, a coating layer made of at least one selected from the group consisting of oxides, hydroxides and carbonates of metals other than rare earths is formed on the surface of the spherical particles. Specifically, a dispersion liquid containing spherical particles and having a pH of 6 to 11 is mixed with at least one aqueous solution selected from the group consisting of alkoxides, chlorides, nitrates, and sulfates of metals other than rare earth metals. Thus, hydrolysis may be performed.

  In step 2, the particles are treated at a pH at which the spherical particles (center part) serving as nuclei do not dissolve. The treatment method basically uses a hydrolysis reaction. It is processed by selecting a pH at which the rare earth compound particles are not dissolved in the pH range of 6 to 11. The pH range at which the rare earth compound does not dissolve can be known from the existing published solubility product data “Atlas of Metal-Ligand Equilibria in Aqueous Solution, Ellis Horwood Limided”.

  In order to adjust the pH, aqueous ammonia, sodium hydroxide, ammonium hydrogen carbonate, ammonium carbonate and the like can be used. The compound of the covering element is a salt such as a metal alkoxide, chloride, nitrate or sulfate, and the metal alkoxide is particularly preferably used because the hydrolysis proceeds sufficiently even in a neutral region. The amount of coating can be controlled by setting conditions for 100% hydrolysis of the compound of the coating element. The average thickness of the coating layer is as described above (5 to 100 nm). At the time of coating, the dispersion state of the central part serving as a nucleus is most preferably a monodispersion state. In order to create a monodispersed state, it is preferable to adjust the absolute value of the surface charge of the central portion serving as a nucleus to 30 to 40 mV or more. If the absolute value of the surface charge is less than 30 mV (for example, 20 to 30 mV), precipitation or aggregation is likely to occur. The surface charge can be adjusted with the pH adjusting agent.

  As a form to coat | cover, it is at least 1 sort (s) selected from the group which consists of a hydroxide, carbonate, basic carbonate, and an oxide. In particular, when coating with an oxide, it may be fired at 400 to 600 ° C. after the coating treatment. Although confirmation by X-ray diffraction (XRD) or the like is necessary, it can be considered as an oxide when the firing temperature exceeds 400 ° C., and as a hydroxide or basic carbonate at 400 ° C. or less. Generally, after coating, the powder is treated by drying at 100 ° C. or baking at 500 ° C. In the multilayer coating treatment, the same treatment as that for the first layer is repeated using the first-layer treated product in consideration of the coating amount.

  The fine particle group of the composite metal compound particles of the present invention is obtained by the above steps. Furthermore, by incorporating a classification step, the standard deviation of the particle size distribution can be controlled to be smaller.

  Classification can be performed by, for example, a method using a difference in particle weight or a difference in surface charge of a particle, a method using a filter having a homogeneous through hole, and the like. Specifically, when a centrifuge is used, classification can be performed based on the difference in particle weight. In the case of classification in a state dispersed in a dispersion medium, it is desirable to create a state where the composite metal compound particles are monodispersed, and classification is preferably performed after adjusting the absolute value of the surface charge to 30 to 40 mV or more.

  The composite metal compound particles of the present invention can be suitably used in the electronic material field, the ceramics field and the like because the standard deviation of the particle size distribution is controlled within 15%, preferably within 10% of the average particle size.

  Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples. However, the present invention is not limited to the examples.

Example 1
100 g of gadolinium nitrate (metal concentration 0.3 mol) was dissolved in 100 L of water. In this solution, 870 g (15 mol) of urea was dissolved, and heating was performed while stirring. The temperature rising rate was 1 hour from room temperature (about 25 ° C.) to 90 ° C. The pH gradually rises and becomes slightly cloudy around pH 6. Continue heating and hold at 70 ° C. for 10 minutes, raise to 90 ° C. (maximum temperature) and stop heating. The reaction vessel was lined with Teflon (registered trademark) PTFE, and the surface of a stirring blade or the like in contact with the liquid was coated with Teflon (registered trademark) PFA.

  After cooling, the precipitated basic gadolinium carbonate powder is filtered off. The separated powder is redispersed in 5 L of water containing 200 g of ammonia water. 56 g of normal ethyl silicate is added dropwise and stirred for 12 hours. This is separated by centrifugation. The powder was washed by repeating redispersion / centrifugation three times. After drying at room temperature, it is further dried at 100 ° C. for 12 hours. This was calcined at 500 ° C. for 4 hours to obtain an oxide.

  Disperse 10 g of this oxide powder in 1 L of water adjusted to pH 10 with ammonia water, centrifuge at 3000 rpm for 5 minutes, remove the liquid other than the precipitate, and further centrifuge at 4000 rpm for 15 minutes in another container. A precipitate was obtained. This precipitate was again subjected to the same treatment. Subsequently, it was re-dispersed in 100 g of water adjusted to pH 8 with aqueous ammonia. Centrifugation was performed at 3000 rpm for 5 minutes each to obtain a target liquid.

  The average particle diameter of the separated basic gadolinium oxide was measured by SEM observation, and the average particle diameter of the basic gadolinium oxide (in the dispersion) after completion of the reaction was measured with a particle size distribution device. The sizes were 190 nm and 196 nm, respectively. Met. Moreover, the average particle diameters of the gadolinium oxide / silica bilayer powder finally coated with normal ethyl silicate were 243 nm (SEM) and 247 nm (particle size distribution apparatus). The standard deviation was ± 9.3% (within 9.3% of the average particle size).

Examples 2-10
Using the raw materials listed in Tables 1 and 2, composite metal compound materials were manufactured by selecting the reaction conditions and rare earth elements in the same procedure as in Example 1.

Comparative Examples 1-2
Using the raw materials listed in Table 2, composite metal oxide materials were produced by changing the reaction conditions in the same manner as in Example 1 and selecting Gd as the rare earth. Moreover, the glass container was used for the comparative example.

It is a schematic diagram of the composite metal compound particle of this invention. _{2 is} an SEM image of composite metal compound particles (center part: Gd ₂ O ₃ , coating layer: SiO ₂ ) produced in Example 1.

Claims (7)

A composite metal compound particle composed of a central portion and a surrounding coating layer,
(1) The central portion is made of a rare earth metal oxide ,
(2) The coating layer is made of an oxide of a metal other than rare earth,
(3) The average particle size of the composite metal compound particles is 35 to 600 nm,
(4) The composite metal compound particles, wherein the standard deviation of the particle size distribution of the composite metal compound particles is within 15% of the average particle size.   2. The rare earth metal is at least one selected from the group consisting of Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. The composite metal compound particle as described.   The composite metal compound particle according to claim 1 or 2, wherein the metal other than the rare earth is at least one selected from the group consisting of Al, Ga, In, Si, Ti, Zr, Sn, Ge, Ta, and Nb.   The composite metal compound particle according to any one of claims 1 to 3, wherein the central portion is composed of spherical particles having an average particle diameter of 30 to 500 nm.   The composite metal compound particle according to any one of claims 1 to 4, wherein the coating layer has an average thickness of 5 to 100 nm. Optical material made of a composite metal compound particles according to any one of claims 1-5. The manufacturing method of the composite metal compound particle of Claim 1 including the following process;
(1) An aqueous solution containing urea and at least one selected from the group consisting of chlorides, nitrates and sulfates of rare earth metals, and containing 10 mol or more of urea with respect to 1 mol of the rare earth metal, and 0% of the rare earth metal. Step 1 of obtaining spherical particles comprising at least one selected from the group consisting of rare earth metal oxides, hydroxides and carbonates by heating an aqueous solution containing 0.001 to 0.01 mol / L. ,
(2) From the oxides, hydroxides and carbonates of metals other than rare earths, by mixing and hydrolyzing the dispersion liquid having a pH of 6 to 11 and alkoxides of metals other than rare earths, containing the spherical particles Forming a coating layer made of at least one selected from the group on the surface of the spherical particles , and
(3) Step 3 of firing the spherical particles after the coating treatment at 400 to 600 ° C.

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