Oxide-coated metallic fine particle and production thereof

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

In the present invention, metal fine particles are used as core particles, and the core particles are a heterogeneous oxide or a compound oxide or a salt of an oxygen acid different from this metal, or a double oxide or a compound salt of an oxide of this metal and a heterogeneous oxide. It relates to oxide-coated metal fine particles coated with (1) and a method for producing the same.

【0002】

[Conventional technology]

Conventionally, the core particles are inorganic material particles such as diamond particles and ceramic particles, and metal particles, and various metal materials, ceramics, oxides, carbides, nitrides, etc. that serve as sintering aids and thermal spraying aids are used for the core particles. The coated metal particles coated with the inorganic material of the above are electrically insulating materials such as semiconductor substrates, printed substrates, various electrically insulating parts, high-hardness and high-precision machining materials such as cutting tools, dies, and bearings, grain boundary capacitors, and humidity. It is used in fields such as the manufacture of functional materials such as sensors, sintered bodies such as precision sintered molding materials, and the manufacture of thermal spray parts such as materials that require high temperature wear resistance such as engine valves. There is. By using such coated particles, the bonding strength and denseness between dissimilar ceramics and dissimilar metals in sintered bodies and sprayed parts are improved.

【0003】

For example, Japanese Patent Application Laid-Open No. 8-253851 states that the surface of Ti powder is coated with a Ni layer of 5 μm or more, and the ratio of the particle size of the Ti powder to the thickness of the Ni layer is 10 or less, and the average particle size is 10 to 150 μm. The composite powder for thermal spraying is disclosed. Further, in Japanese Patent Application Laid-Open No. 8-253853, a part of WC powder having an average particle size of 0.5 to 20 μm is embedded in the surface of a Co-Cr alloy powder having an average particle size of 20 to 99 μm. The composite powder for thermal spraying is disclosed. Then, these composite powders for spraying are powders in which the powders of both raw materials are mixed directly or uniformly by a mixer, sealed in a stirring container, and stirred with a stirring rod to form the coated powder as core particles. It is manufactured by mechanically pressing it against the surface, crimping it, and mechanically covering it.

【0004】

In addition, JP-A-3-75302, JP-A-7-53268-7-54008, and other particles of inorganic or metallic materials having an average particle size of 0.1 μm to 100 μm according to the applicant's application. Discloses coating particles coated with ultrafine particles of the same or different kinds of inorganic materials or metal materials having an average particle size of 0.005 μm to 0.5 μm, and a method for producing the same. The method for producing coated particles disclosed here is to generate these ultrafine particles by a vapor phase method such as a thermal plasma method, and then introduce core particles to be coated into the flow of the generated ultrafine particles. Alternatively, the core particles to be coated are introduced into the space where the ultrafine particles are generated, and the two are brought into contact with each other in a fluid state to coat the surface of the core particles with the ultrafine particles.

【0005】

[Problems to be Solved by the Invention]

By the way, the composite powder for spraying disclosed in JP-A-8-253851 and 8-253853 is a coating powder such as Ni powder or WC powder on core particles such as Ti powder and Co-Cr alloy powder. Is merely mechanically pressed and crimped to mechanically coat it, the adhesion at the interface is weak, the particle size of the core particles is as large as several μm to a hundred and several tens of μm, and the coating powder is also 0.5. There was a problem that it was limited to those as large as ~ 20 μm. Further, although the core particles are metals, the coating powder is only disclosed as a metal or a carbide thereof, and the surface of the metal particles to be the core particles is not coated with a different kind of oxide.

【0006】

Further, the coating particles disclosed in JP-A-3-75302 and others according to the application of the present applicant are average particles because the coating particles are produced by a vapor phase method such as thermal plasma. It is an ultrafine particle with a diameter of 0.005 μm to 0.5 μm, but if the core particle is, for example, a fine particle of 1 μm or less, it is easy to aggregate and it is difficult to monodisperse, so it is not possible to cover individual core particles well. Therefore, there is a problem that the core particles themselves are not finely divided and only cover the ultrafine particles with an average particle size of 0.1 μm to 100 μm, and only coated particles having a large particle size can be obtained. In addition, there is a problem that it is not possible to obtain coated particles coated in a completely film-like form.

【0007】

Further, what is disclosed in these is that when the core particles are basically metal particles, the coating particles are also mostly metal ultrafine particles, and the metal fine particles are coated with a different kind of oxide. It does not obtain fine particles. In Japanese Patent Application Laid-Open No. 7-54008, TiAl quasi-fine particles having an average particle size of 40 μm are used as core particles, and alumina (Al), which is an oxide of the same type as the core particles, is used.₂O₃) Alumina-coated TiAl semi-fine particles coated with ultrafine particles are disclosed, but the core particles are not fine particles of 1 μm or less, and the coated oxide alumina is also one of the metals that are the main components of the core particles. It is not a different kind of oxide.

【0008】

As described above, the conventionally obtained coated particles have a large core particle size, the metal core particles are coated with a metal, and the inorganic material particles are coated with an inorganic material. Artificial bones, which are useful for conventional sintered bodies and sprayed parts, but have problems with strength and affinity with living organisms, and fuel cells, which require strength and adhesion to various inorganic materials. Since it is not suitable for use as an electrode material or the like, there has been a strong demand for oxide-coated metal fine particles in which metal fine particles are coated with dissimilar oxides.

【0009】

The subject of the present invention is to solve the above-mentioned problems of the prior art, and to firmly, preferably all, the metal fine particles to be core particles contain an oxide containing no metal element as a main component constituting the metal fine particles. It is an object of the present invention to provide a novel oxide-coated metal fine particle whose surface is completely coated and a method for producing an oxide-coated metal fine particle capable of reliably and easily producing such a novel oxide-coated metal fine particle.

【0010】

[Means for solving problems]

In order to solve the above problems, the present invention comprises a core particle composed of metal fine particles and an oxide or a compound oxide or a salt of oxygen acid containing no metal element as a main component constituting the metal fine particles. Alternatively, the oxide coating is characterized by having a coating layer for coating the core particles, which is composed of the compound oxide or the compound salt of the oxide or the compound oxide or the salt of oxygen acid and the oxide of the metal element. It provides metal fine particles.

【0011】

Here, it is preferable that the average particle size of the core particles is 0.01 μm to 1 μm, and the average thickness of the coating layer is 1 nm to 10 nm. The metal elements that are the main components of the metal fine particles are Al, Ti, V, Cr, Fe, Co, Ni, Mn, Cu, Zn, Zr, Ru, Pd, Ag, In, Pt, Au and It is preferable that it is at least one metal element selected from the group consisting of Sm, and the oxide or compound oxide or salt of oxygen acid that coats the metal fine particles is titanium oxide, zirconium oxide, calcium oxide, or the like. Silicon oxide, aluminum oxide, silver oxide, iron oxide, magnesium oxide, manganese oxide, yttrium oxide, cerium oxide, samarium oxide, beryllium oxide, barium titanate, lead titanate, lithium aluminate, yttrium vanadium, calcium phosphate, zirconic acid It is preferably at least one selected from the group consisting of calcium, lead titanium zirconate, iron titanium oxide, cobalt titanium oxide and barium tinate.

【0012】

Further, the present invention was obtained by mixing a metal powder raw material and a powder raw material of an oxide, a compound oxide or a salt of oxygen acid which does not contain a metal element as a main component of the metal powder raw material as a main component. After supplying the raw material mixture to a thermal plasma to prepare a mixture in a gas phase state, the mixture in the gas phase state is rapidly cooled to use metal fine particles finer than the metal powder raw material as core particles, and the oxide or compound is used. Oxide or a salt of an oxygen acid, or an oxidation forming a coating layer covering the core particles, which is a compound oxide or a compound salt of the oxide or the compound oxide or the salt of the oxygen acid and the oxide of the metal. The present invention provides a method for producing oxide-coated metal fine particles, which comprises producing object-coated metal fine particles.

【0013】

Here, it is preferable that the average particle size of the core particles is 0.01 μm to 1 μm, and the average thickness of the coating layer is 1 nm to 10 nm. The metal elements that are the main components of the metal fine particles are Al, Ti, V, Cr, Fe, Co, Ni, Mn, Cu, Zn, Zr, Ru, Pd, Ag, In, Pt, Au and It is preferable that it is at least one metal element selected from the group consisting of Sm, and the oxide or compound oxide or salt of oxygen acid that coats the metal fine particles is titanium oxide, zirconium oxide, calcium oxide, or the like. Silicon oxide, aluminum oxide, silver oxide, iron oxide, magnesium oxide, manganese oxide, yttrium oxide, cerium oxide, samarium oxide, beryllium oxide, barium titanate, lead titanate, lithium aluminate, yttrium vanadium, calcium phosphate, zirconic acid It is preferably at least one selected from the group consisting of calcium, lead titanium zirconate, iron titanium oxide, cobalt titanium oxide and barium tinate. The average particle size of the metal powder raw material is 0.5 μm to 20 μm, more preferably the total particles are 20 μm or less, and the average particle size of the oxide powder raw material is 0.1 μm to 1 μm. .. Further, the mixing of the metal powder raw material and the oxide powder raw material is preferably performed by a high-speed shearing / impact type mixer or a grinding type mixer, and the metal powder raw material and the oxide powder raw material are mixed with each other. The raw material mixture is preferably an aggregate of composite particles in which the oxide powder raw material is coated with the individual metal powder raw materials. Further, the temperature of the thermal plasma is preferably higher than the boiling points of the metal powder raw material and the oxide powder raw material. Further, the atmosphere of the thermal plasma is preferably an atmosphere of atmospheric pressure or less, and preferably 200 Torr to 600 Torr. The atmosphere for rapidly cooling the mixture in the gas phase state is preferably an inert atmosphere or a reducing atmosphere, and preferably contains a rare gas, or a rare gas and hydrogen.

【0014】

BEST MODE FOR CARRYING OUT THE INVENTION

The oxide-coated metal fine particles and the method for producing the same according to the present invention will be described in detail below based on the preferred embodiments shown in the accompanying drawings.

【0015】

FIG. 1 is a schematic cross-sectional view showing the configuration of an example of oxide-coated metal fine particles of the present invention. As shown in the figure, the oxide-coated metal fine particles (hereinafter, simply referred to as coated particles) 10 contain metal fine particles 12 as core particles and metal elements as main components constituting the metal fine particles 12. It has an oxide coating layer 14 composed of no oxide or a composite oxide of this oxide and an oxide of this metal element.

【0016】

Here, the metal fine particles 12 serve as core particles of the coated particles 10, and may be fine particles of one kind of metal or fine particles of alloys of a plurality of metals, depending on the use of the coated particles 10. Can be selected as appropriate. For example, the main metal elements constituting the metal fine particles 12 are Al, Ti, V, Cr, Fe, Co, Ni, Mn, Cu, Zn, Zr, Ru, Pd, Ag, In, Pt, Au and At least one metal element selected from the group consisting of Sm can be mentioned. More specifically, single metals such as the above-mentioned metal elements, various intermetallic compounds of these metal elements, and two or more alloys of these metal elements, for example, Fe-Co-Ni alloys and Ni-Fe alloys. , Ni-Cu alloys, Ni-Mn alloys, In-Ni alloys, Al-Ti alloys, Ti-Cu alloys and other various alloys, and composite materials thereof. In particular, Ti is preferable for artificial bone applications, Fe is preferable for cosmetic additives and catalyst applications, and Ni is preferable for electrode materials such as fuel cells.

【0017】

The average particle size of the metal fine particles 12 is not particularly limited as long as they are fine particles, but fine particles having an average particle size in the range of 0.01 μm to 1 μm are preferable, and more preferably 0.1 μm to 0.5 μm. Fine particles in the range of are preferable. Further, the particle size distribution of the metal fine particles 12 is not particularly limited, and it is preferable that the particle size variation is small, that is, the half-value width of the particle size distribution is narrow.

【0018】

Further, the oxide coating layer (hereinafter, simply referred to as a coating layer) 14 uses the metal fine particles 12 as core particles and completely covers the outer peripheral surface thereof, preferably the entire outer peripheral surface, and constitutes the main metal fine particles 12. Consists of an oxide that does not contain a metal element as a main component, that is, a layer of a heterogeneous oxide or a layer of a compound oxide or a layer of a salt of oxygen acid, or a salt of this heterogeneous oxide or a compound oxide or an oxygen acid. It is a compound oxide layer or a compound salt layer of a metal element and oxygen constituting the metal element and the metal fine particle 12.

【0019】

Here, a salt of a heterogeneous oxide or a compound oxide or an oxygen acid used for the oxide coating layer 14 in the present invention, or a compound oxide or a compound salt thereof (hereinafter, these are also collectively referred to as an oxide). (A) is not particularly limited, and may be any oxide, compound oxide, salt of oxygen acid, or compound salt, and may be appropriately selected for the metal fine particles 12 and the coated particles 10 to be coated. Good. For example, titanium oxide (TiO₂), Zirconium oxide (ZrO)₂), Calcium oxide (CaO), Silicon oxide (SiO)₂), Aluminum oxide (alumina: Al₂O₃), Silver oxide (Ag₂O), iron oxide, magnesium oxide (MgO), manganese oxide (Mn)₂O₇), Yttrium oxide (Y₂O₃), Cerium oxide, samarium oxide, oxides such as beryllium oxide (BeO), barium (meth) titanate (BaTiO)₃), Lead titanate (PbTiO₃), Lithium aluminate, yttrium vanadium, calcium phosphate, calcium zirconate, lead titanate titanate, iron titanium oxide (FeTiO)₃), Titanium Cobalt (CoTiO)₃), Barium tinate (BaSnO)₃), Etc., but CaO or SiO for Ti, especially in artificial bone applications.₂Alternatively, calcium phosphate is preferred, and for cosmetic additives and catalyst applications, TiO is used relative to Fe.₂Is preferable, and ZrO with respect to Ni or Cu is used for electrode materials such as fuel cells.₂Or BaTiO₃Is preferable.

【0020】

The average thickness of the coating layer 14 is not particularly limited and may be appropriately selected depending on the average particle size of the metal fine particles 12 and the size and application of the coating particles 10, but is 1 nm to 10 nm. Preferably, more preferably, the range of 3 nm to 5 nm is preferable. In the present invention, one of the characteristics of the coating layer 14 is that the thickness of the coating layer 14 is uniform or substantially uniform over the entire outer peripheral surface of the metal fine particles 12, and the more uniform or uniform the thickness is. Of course, the closer it is, the more preferable it is, but the present invention is not limited to this, and the thickness may be slightly uneven. In this case as well, the average thickness of the entire outer peripheral surface satisfies the above range. It is better to do so. The oxide-coated metal fine particles according to the present invention are basically configured as described above.

【0021】

Next, the method for producing the oxide-coated metal fine particles of the present invention will be described below with reference to FIGS. 2 to 5. FIG. 2 is a block diagram showing an example of the method for producing oxide-coated metal fine particles of the present invention. FIG. 3 is a block diagram showing an example of a mixing treatment block of the method for producing oxide-coated metal fine particles shown in FIG. FIG. 4 is an explanatory diagram illustrating a state in which particles are compounded, which is carried out in the mixing processing block shown in FIG. FIG. 5 is a schematic cross-sectional view of an embodiment of the oxide-coated metal fine particle manufacturing apparatus for carrying out the thermal plasma treatment of the oxide-coated metal fine particle manufacturing method of the present invention shown in FIG. The method for producing the oxide-coated metal fine particles of the present invention is not limited to these illustrated examples.

【0022】

As shown in FIG. 2, in the oxide-coated metal fine particle manufacturing process 20 for carrying out the method for producing the oxide-coated metal fine particles of the present invention, the metal powder raw material 22 and the oxide for forming the metal fine particles 12 to be the core particles 12 are formed. A mixing treatment step 26 in which the oxide powder raw material 24 for forming the coating layer 14 is mixed, and a thermal plasma treatment of the mixture of the core particle metal powder raw material 22 and the oxide powder raw material 24 obtained in this mixing step 26 are subjected to thermal plasma treatment. Then, it is composed of a thermal plasma treatment step 28 for producing the coated particles 10 of the present invention in which the finely divided metal fine particles 12 from the metal powder raw material 22 are coated with a dense coating layer 14.

【0023】

The metal powder raw material 22 used in the present invention supplies the metal constituting the metal fine particles 12 serving as the core particles of the coating particles 10, and is not particularly limited as long as it is the metal powder raw material of the metal fine particles 12 described above. Absent. The average particle size of the metal powder raw material 22 is not particularly limited, but when the average particle size of the metal fine particles 12 is in the range of 0.05 μm to 1 μm, it is preferably in the range of 0.5 μm to 20 μm. More preferably, the total particle size is in the range of 20 μm or less.

【0024】

The oxide powder raw material 24 used in the present invention is an oxide or double oxide or oxygen that does not contain a metal element as a main component of the metal powder raw material 22 constituting the oxide coating layer 14 of the coating particles 10. It supplies an acid salt, and is not particularly limited as long as it is a powder raw material of the above-mentioned oxide, compound oxide, or oxygen acid salt. The average particle size of the oxide powder raw material 24 is not particularly limited, but when the average thickness of the coating layer 14 is in the range of 1 nm to 10 nm, it is preferably in the range of 0.1 μm to 1 μm. It is preferably in the range of 0.2 μm to 0.5 μm.

【0025】

The mixing treatment step 26 shown in FIG. 2 is a step of mixing the metal powder raw material 22 serving as the core particles 12 and the oxide powder raw material 24 serving as the coating layer 14. In this mixing treatment step 26, both powder raw materials 22 and 24 may be mixed in any way as long as they can be mixed, but it is preferable to uniformly mix both powder raw materials 22 and 24. Here, the mixer used in the mixing treatment step 26 is not particularly limited, and examples thereof include conventionally known mixers such as a high-speed shearing / impact type mixer and a grinding type mixer.

【0026】

In particular, in the present mixing treatment step 26, both powder raw materials 22 and 24 are compounded to disperse the individual particles of the metal powder raw material 22, and the entire outer circumference of the dispersed individual particles of the metal powder raw material 22 is dispersed. It is more preferable to use composite particles dispersed and adhered so that a large number of particles of the oxide powder raw material 24 are uniformly coated. Here, FIG. 3 shows a block diagram showing an example of a mixing treatment process block for obtaining composite particles. As shown in the figure, the mixing treatment step 26 includes a premixing treatment step 30 in which the metal powder raw material 22 and the oxide powder raw material 24 are premixed in advance, preferably uniformly mixed, prior to the compounding treatment. It is composed of a particle compounding treatment step 32 for producing the compounded particles 34 by compounding the premixed powder raw material mixture.

【0027】

The premixing treatment step 30 is a step for uniformly mixing the metal powder raw material 22 and the oxide powder raw material 24 in advance. In this premixing process 30, for example, a V-type mixer, a bicone-type mixer, or the like can be used, but in addition, any conventionally known mixer can be used. By the way, in the premixing process 30, the metal powder raw material 22 and the oxide powder raw material 24 are mixed by the above-mentioned mixer, and as shown in FIG. 4A, the metal powder raw material 22 and the oxide powder are mixed. The raw materials 24 are uniformly mixed as in a so-called normal mixing, but the metal powder raw materials 22 and the oxide powder raw materials 24, which are particularly fine particles, are slightly agglomerated with each other. Is evenly mixed.

【0028】

Next, the raw material mixture of the metal powder raw material 22 and the oxide powder raw material 24 uniformly mixed in the premixing treatment step 30 is obtained by compounding both the powder raw materials 22 and 24 in the particle compounding treatment step 32, and the composite particles. Manufacture 34. In the present invention, as shown in FIG. 4 (b), compounding means a large number of oxide powder raw materials 24 on the entire outer periphery of each particle of the metal powder raw material 22 without agglomeration of the metal powder raw materials 22. Composite particles 34a, in which the particles are dispersed and simply adhered, or, as shown in FIG. 4 (c), some or all of the particles of the oxide powder raw material 24 are of the individual particles of the metal powder raw material 22. A large number of particles of the oxide powder raw material 24 are dispersed on the entire outer circumference of the individual particles of the metal powder raw material 22 so as to be embedded therein, and preferably uniformly dispersed and coated in a fixed state, preferably uniformly. It refers to producing the composite particles 34b to be coated, or the composite particles 34 in various states in between these.

【0029】

In the particle compounding treatment step 32 of the present invention, it is preferable to combine all the powder raw materials 22 and 24 to form composite particles 34, but the present invention is not limited to this. It goes without saying that the part may contain a powder raw material mixture that is not compounded. The particle composite processing step 32 is not particularly limited as long as the particles are composited by utilizing shearing force, impact force, or grinding force. For example, a high-speed shearing / impact type mixer or abrasion is used. A crushing mixer or the like can be used.

【0030】

The powder raw material mixture thus obtained in the mixing treatment step 26 (preferably containing the composite particles 34) is sent to the thermal plasma treatment step 28. The thermal plasma treatment step 28 is carried out in the oxide-coated metal fine particle manufacturing apparatus shown in FIG. The oxide-coated metal fine particle manufacturing apparatus 40 shown in FIG. 5 includes a plasma torch 42 having a plasma chamber 42a, a quartz double tube 44, a cooling double tube 46, a quenching tube 48, and a powder raw material mixture supply device 50. , Has a product recovery unit 52.

【0031】

Here, the plasma torch 42 includes a quartz tube 42b constituting a plasma chamber 42a that generates a thermal plasma (plasma flame) 43 inside, a high-frequency transmission coil 42c attached to the outside of the quartz tube 42b, and the high-frequency transmission. A cooling mantle tube 42d provided on the outside of the coil 42c and a gas outlet 42e provided on the upper part of the quartz tube 42b and ejecting plasma gas in three directions of tangential, axial and radial directions. And a supply port 42f for supplying the powder raw material mixture to the thermal plasma 43 formed in the plasma chamber 42a. The plasma torch 42 is a double tube consisting of a quartz tube 42b and a mantle tube 42d, and a coil 42c is inserted between them. However, the present invention is not limited to this, and the coil 42c is turned outward. It may be a multi-tube configuration of 3 or more, and its size is not particularly limited. Further, the ejection direction of the plasma gas at the gas ejection port 42e is not limited to three directions, and may be ejected in various directions.

【0032】

The gas outlet 42e is connected to one or more gas sources 42g on the outer upper side of the plasma torch 42. When plasma gas is supplied from the gas supply source 42g to the gas outlet 42e, plasma gas is ejected from the gas outlet 42e into the plasma chamber 42a from the above three directions, and the ejected plasma gas is high frequency (RF). ) Plasma is generated by the high-frequency transmission coil 42c to which a high-frequency voltage is applied from the power source, and a thermal plasma 43 is formed in the plasma chamber 42a of the plasma torch 42. The plasma gas supplied from the gas outlet 42e is limited to a rare gas such as argon and helium, a gas such as hydrogen and nitrogen, and a mixed gas thereof. The amount of the gas supplied from the gas outlet 42e may be appropriately selected according to the size of the plasma chamber 42a, the properties of the thermal plasma 43, the processing amount of the powder raw material mixture, and the like. Further, the high frequency (frequency) and voltage (or power) of the high frequency voltage applied to the high frequency transmitting coil 42c are not particularly limited, and may be appropriately selected according to the properties such as the temperature of the thermal plasma 43.

【0033】

Here, since the temperature of the thermal plasma 43 thus formed needs to vaporize the powder raw material mixture of the metal powder raw material 22 and the oxide powder raw material 24, the mixture of these powder raw materials 22 and 24 is used together. Must be above boiling point. The higher the temperature of the thermal plasma 43, the easier it is to vaporize the mixture of the two powder raw materials 22 and 24. Therefore, the higher the temperature of the thermal plasma 43, the more preferable, but not particularly limited. For example, it may be equal to or higher than the boiling point of the metal powder raw material 22 and the oxide powder raw material 24, or may be appropriately selected according to the metal powder raw material 22 and the oxide powder raw material 24. For example, specifically, the temperature of the thermal plasma 43 can be set to 6000 ° C. or higher. On the other hand, the upper limit is not particularly limited and it is difficult to measure, so it is difficult to determine the upper limit, but theoretically it is considered to reach about 10,000 ° C. The atmosphere of the thermal plasma 43 is not particularly limited, but is preferably an atmosphere of atmospheric pressure or lower, that is, an atmospheric pressure atmosphere or a reduced pressure atmosphere. The atmosphere of the thermal plasma 43 below the atmospheric pressure is not particularly limited, but is preferably 200 Torr to 600 Torr.

【0034】

The powder raw material mixture supply port 42f is also connected to the powder raw material mixture supply device 50 on the outer upper side of the plasma torch 42. From the powder raw material mixture supply device 50 to the supply port 42f, the powder raw material mixture, for example, Fe-TiO₂The powder mixture, preferably the composite particles 34, is supported on a carrier gas and introduced into the thermal plasma. The carrier gas for carrying the powder raw material mixture is limited to a rare gas such as argon and helium, a gas such as hydrogen and nitrogen, and a mixed gas thereof. The plasma gas or a part thereof (one or two or more of the gases before mixing) may be used as a carrier gas for supporting the powder raw material mixture. In this way, the powder raw material mixture introduced into the thermal plasma 43 is heated by the heat of the thermal plasma 43 and gasified in an instant, and in the thermal plasma 43, the metal powder raw material 22 and the oxide powder of the powder raw material mixture are used. Both the raw material 24 and the raw material 24 are in a gas phase state. Here, the supply amount of the powder raw material mixture supplied from the supply port 42f, and the type and supply amount of the carrier gas carrying the powder raw material mixture are also not particularly limited, and the properties of the thermal plasma 43 and the powder raw material mixture are not particularly limited. It may be appropriately selected according to the processing amount and the like.

【0035】

The quartz double tube 44 is provided under the plasma torch 42, and a mixed gas of the metal powder raw material 22 vaporized by the thermal plasma 43 and the oxide powder raw material 24 is derived from the thermal plasma 43 inside. It has a quartz tube 44b having a diameter slightly larger than the quartz tube 42b of the plasma torch 42 and a cooling cloak tube 44c provided outside the quartz tube 44b, which constitutes the cooling chamber 44a for the primary cooling. The cooling double tube 46 is provided below the quartz double tube 44, and is internally provided with the primary cooled gas phase, liquid phase or solid phase metal powder raw material 22 and oxide in the quartz double tube 44. An inner pipe 46b having substantially the same diameter as the quartz pipe 44b of the quartz double pipe 44, which constitutes a cooling chamber 46a for further secondary cooling of the powder raw material 24, and a cooling outer pipe provided outside the inner pipe 46b. Has 46c and.

【0036】

The quenching pipe 48 is provided below the cooling double pipe 46, and internally, the gas phase, liquid phase or solid phase metal powder raw material 22 and the oxide powder raw material that are secondarily cooled in the cooling double pipe 46 are provided. An inner tube 48b having a diameter significantly larger than that of the quartz tube 46b of the cooling double tube 46, which constitutes the coating particle generation chamber 48a for rapidly cooling the 24 and the coating particle 10 of the present invention, and this inner tube 48b. It has a cooling mantle tube 48c provided on the outside of the. In the coated particle generation chamber 48a of the quenching tube 48, the raw material mixture of the secondary cooled gas phase or liquid phase metal powder raw material 22 and the oxide powder raw material 24 is rapidly cooled in the cooling double tube 46. , Gas phase or liquid phase The raw material mixture of the metal powder raw material 22 and the oxide powder raw material 24 is made finer than the solid phase metal powder raw material 22 at once, that is, smaller than the particle size of the particles of the metal powder raw material 22, preferably. Uses metal fine particles 12 having a particle size of a fraction to a few tenths as core particles, and coats the core particles with a dense and uniform thickness oxide coating layer 14 formed from an oxide powder raw material 24. The coated particles 10 of the present invention are produced. Here, the coating layer 14 is a layer of an oxide, a compound oxide, or a salt of oxygen acid that does not contain a metal element as a main component of the metal fine particles 12, but is densely bonded (adhered) or bonded together with these. As long as it is coated, it may also contain an oxide or a compound oxide of a metal element or a salt of oxygen acid, which is a main component of the metal fine particles 12.

【0037】

Here, the atmosphere in the coated particle generation chamber 48a of the quenching tube 48 for quenching the raw material mixture in the gas phase or liquid phase suppresses the oxidation of the metal fine particles as the core particles, that is, the formation of oxides of the constituent metal elements. Alternatively, in order to prevent it, an inert atmosphere or a reducing atmosphere is preferable. Here, the inert atmosphere or the reducing atmosphere is not particularly limited, but for example, argon (Ar), helium (He), and nitrogen (N).₂) At least one inert gas atmosphere, or hydrogen (H) in these inert gases₂), Specifically, a rare gas atmosphere such as an argon atmosphere or a helium atmosphere, an inert atmosphere such as a nitrogen gas atmosphere or a mixed gas atmosphere of argon or helium and nitrogen gas, or an argon atmosphere containing hydrogen. , A reducing atmosphere such as a helium atmosphere containing hydrogen and a nitrogen gas atmosphere containing hydrogen, and the degree of the reducing property is not limited. Further, the quartz double tube 44, the cooling double tube 46, and the quenching tube 48 also have a double tube configuration similar to the plasma torch 42, but the present invention is not limited to this, and the present invention is not limited to this. It may be, and its size is not particularly limited.

【0038】

The product recovery unit 52 is a portion for collecting the coated particles 10 of the present invention generated in the coated particle generation chamber 48a of the quenching tube 48, and is provided at the lower outer side of the quenching tube 48 and communicates with the coated particle generation chamber 48a. A filter 52b provided between the chamber 52a and the communication portion between the recovery chamber 52a and the coated particle generation chamber 48a, which separates the coated particles 10 of the present invention from a fluidized gas such as a carrier gas or a plasma gas and recovers them. And a gas suction / discharge port 52c that sucks the coated particles 10 of the present invention in the coated particle generation chamber 48a together with the fluidized gas and sucks and discharges only the fluidized gas separated by the filter 52b.

【0039】

The gas suction / discharge port 52c is connected to the gas suction source 52d on the outer upper side of the product recovery unit 52. The fluidized gas sucked by the gas suction source 52d through the gas suction port 52c consists of a plasma gas such as argon and nitrogen used to generate the thermal plasma 43 and a carrier gas of a powder raw material mixture such as argon. , The coated particle generation chamber 48a is sucked into the product recovery unit 52 together with the coated particle 10 of the present invention, but the particles generated in the coated particle generation chamber 48a are not perfect coated particles other than the coated particle 10 of the present invention. Even if it contains metal particles, oxide particles, etc., these particles are completely recovered in the recovery chamber 52a by the filter 52b, and only the fluidized gas separated by the filter 52b from the gas suction port 52c. Is discharged.

【0040】

Although not shown, the powder raw material mixture supply device 50 supports a powder raw material mixture of the metal powder raw material 22 and the oxide powder raw material 24 mixed by various mixing devices in the mixing treatment step 26 on a carrier gas such as argon. A storage chamber for supplying the thermal plasma 43 of the plasma torch 42, a storage chamber for storing the powder raw material mixture, a mixing chamber for supporting the powder raw material mixture stored in this storage chamber on a carrier gas, and a carrier in this mixing chamber. It has a gas supply source for supplying gas and the like. The oxide-coated metal fine particle manufacturing apparatus 40 of the illustrated example comprises quenching the plasma torch 42 for vaporizing the powder raw material mixture of the metal powder raw material 22 and the oxide powder raw material 24 and the gas phase powder raw material mixture of the present invention. Although it has a quartz double tube 44 and a cooling double tube 46 that perform two-stage cooling of primary and secondary cooling for intermediate cooling with the quenching tube 48 that produces the coated particles 10. The present invention is not limited to this, and may not have these intermediate cooling means at all, may have a means for performing one-stage intermediate cooling, or may provide three or more stages of intermediate cooling. You may have the means to do so.

【0041】

The oxide-coated metal fine particle manufacturing apparatus for carrying out the thermal plasma treatment step 28 of the oxide-coated metal fine particle manufacturing process of the present invention is basically configured as described above. The thermal plasma treatment step 28 for producing metal fine particles will be described.

【0042】

First, the powder raw material mixture (preferably composite particles 34) obtained in the mixing treatment step 26 is sent to the thermal plasma treatment step 28, and the powder raw material mixture supply device of the oxide-coated metal fine particle production apparatus 40 shown in FIG. Supplied to 50. At this time, in the oxide-coated metal fine particle manufacturing apparatus 40, a predetermined high-frequency voltage is applied to the high-frequency transmission coil 42c of the plasma torch 42, and the plasma gas supplied from the gas supply source 42g from the gas outlet 42e. Is ejected, and thermal plasma (plasma flame) 43 is generated and maintained in the plasma chamber 42a.

【0043】

Subsequently, when the powder raw material mixture is supplied from the powder raw material mixture supply device 50 to the thermal plasma 43 formed in the plasma chamber 42a through the supply port 42f, the metal powder raw material 22 and the oxide powder in the powder raw material mixture are supplied. The raw material 24 and the raw material 24 evaporate and both become in a vapor phase state. Both the metal powder raw material 22 and the oxide powder raw material 24, which are in the vapor phase state by the thermal plasma 43, descend from the plasma chamber 42a and escape from the thermal plasma 43, and enter the cooling chamber 44a of the quartz double tube 44. It enters, is first cooled, and further descends into the cooling chamber 46a of the cooling double pipe 46, where it is secondarily cooled.

【0044】

Subsequently, both the raw materials of the metal powder raw material 22 and the oxide powder raw material 24, which have been secondarily cooled and are in the gas phase state or the partially liquid phase state, further descend and the coated particle generation chamber 48a of the quenching tube 48. to go into. Since the size of the coated particle generation chamber 48a is extremely large compared to the size of the cooling chamber 46a of the cooling double tube 46, the metal powder raw material 22 that has entered the coated particle generation chamber 48a and is in a gas phase state or a partially liquid phase state 22 Both the raw material and the oxide powder raw material 24 are rapidly cooled, solidified at once, and made finer than the metal powder raw material 22, that is, smaller than the particle size of the particles of the metal powder raw material 22, for example, one tenth. The coated particles 10 of the present invention are produced in which the metal fine particles 12 having a particle size are used as core particles and the core particles are coated with a dense and uniform thickness oxide coating layer 14 formed from the oxide powder raw material 24. To.

【0045】

In this way, the entire outer periphery of the metal fine particles 12 of the finely divided core particles is composed of an oxide, a compound oxide, or a salt of oxygen acid that does not contain the metal element that is the main component of the metal fine particles 12 as a main component, and is further required. To obtain the oxide-coated metal fine particles 10 of the present invention in which the coating layer 14 containing the oxide or compound oxide of the metal element which is the main component of the metal fine particles 12 or the salt of oxygen acid is densely coated. Can be done. In the thermal plasma treatment step 28, the powder raw material mixture supplied from the powder raw material mixture supply device 50 of the oxide-coated metal fine particle manufacturing apparatus 40 was produced in the particle compounding treatment step 32 of the above-mentioned mixing treatment step 26. By using the composite particles 34, the yield of the coated particles 10 of the present invention produced can be significantly improved. As described above, the method for producing oxide-coated metal fine particles of the present invention is not limited to the two-stage intermediate cooling by the quartz double tube 44 and the cooling double tube 46, and even the one-stage intermediate cooling has three stages. The above intermediate cooling may be used. The method for producing oxide-coated metal fine particles of the present invention is basically configured as described above.

【0046】

[Example]

Hereinafter, the present invention will be specifically described based on examples. (Example 1) Fe powder raw material 22 having an average particle size of 5 μm and TiO having an average particle size of 1 μm₂The powder raw material 24 is TiO using the oxide-coated metal fine particle manufacturing apparatus 40 shown in FIG. 5 according to the oxide-coated metal fine particle manufacturing process 20 shown in FIGS. 1 and 3.₂Fe fine particles 10 coated with. Here, in the premixing process 30 of the mixing process 26 shown in FIG. 3, the high-speed stirring type mixer Hi-X (manufactured by Nisshin Engineering Co., Ltd.) is used, and in the particle compounding process 32, the particle compounding device Theta. A composer (manufactured by Tokuju Kosakusho Co., Ltd.) was used. Further, in the oxide-coated metal fine particle manufacturing apparatus 40 shown in FIG. 5, the quartz tube 42b of the plasma torch 42, the quartz tube 44b of the quartz double tube 44, the inner tube 46b of the cooling double tube 46, and the inner tube of the quenching tube 48 The dimensions of 48b were 55 mm in inner diameter and 220 mm in length, 120 mm in inner diameter and 250 mm in length, 120 mm in inner diameter and 100 mm in length, and 400 mm in inner diameter and 900 mm in length, respectively.

【0047】

Also, TiO₂The supply ratio of powder raw material 24 and Fe powder raw material 22 is TiO.₂The mixing ratio of the powder raw material 24 was 4.5 wt% (8 vol%). A high-frequency voltage of about 4 MHz and about 6 kV is applied to the high-frequency transmission coil 42c of the plasma torch 42, and argon 100 liters / minute and hydrogen 10 liters / minute are applied to the plasma gas ejected from the gas outlet 42e. A mixed gas of minutes was used. At this time, the atmosphere of the thermal plasma 43 formed in the plasma chamber 42a of the plasma torch 42 was a reduced pressure atmosphere of about 450 Torr. Also, a powder raw material mixture (Fe-TiO)₂The composite particles 34) were supported by argon, which is a carrier gas, at a rate of 10 g / hour from the supply port 42f of the plasma torch 42, and were supplied into the thermal plasma 43 at a rate of 10 g / hour. The atmosphere in the coated particle generation chamber 48a of the quenching tube 48 was a reducing atmosphere made of argon containing hydrogen.

【0048】

In this way, the oxide-coated metal fine particles 10 could be produced with good yield. In the oxide-coated metal fine particles 10 produced in this manner, the Fe fine particles 12 serving as core particles have an average particle size of 0.3 μm, the oxide coating layer 14 has an average thickness of 5 nm, and the outer peripheral surface of the Fe fine particles 12 and oxidation. The material coating layer 14 was oxide-coated metal fine particles that were densely and firmly bonded. The TEM (scanning transmission electron microscope) photograph of the oxide-coated metal fine particles 10 obtained in this example is shown in FIG. 6, and points No. 5 and No. 6 of the oxide-coated metal fine particles 10 in the TEM photograph of FIG. 6 are shown. EDX (Energy Dispersive X-ray Analysis) analysis chart of is shown in Fig. 7 and Fig. 8. From Fig. 6, it can be seen that one coating particle is composed of a core part (core particle) and a coating layer (film) part of several nm, and from the EDX analysis chart of No. 6 in Fig. 8, the core part (core particle). ) Is a Fe particle of several tens of nm and does not contain Ti or O. Furthermore, Fe, Ti, O appear in the EDX analysis chart of No. 5 in Fig. 7. , The film part (coating layer) is not an oxide of Fe and Ti of several nm, that is, a simple oxide layer of Fe, but mainly a component Fe of core particles and a coating oxide TiO.₂It is concluded that this is a layer composed of a double oxide fused with.

【0049】

As a result, according to the present embodiment, the obtained oxide-coated metal fine particles 10 are densely and uniformly coated with the coating layer 14 mainly containing Fe-Ti-O double oxide on the entire outer periphery of the Fe fine particles 12. It can be seen that the thickness of the coating layer 14 of the Fe-Ti-O double oxide is extremely uniform. Further, it can be seen that according to the present invention, the oxide-coated metal fine particles 10 of the present invention as shown in FIG. 6 can be produced extremely reliably and easily with good yield.

【0050】

(Example 2) Ni powder raw material 22 having an average particle size of 6 μm and BaTiO having an average particle size of 0.5 μm₃BaTiO with the powder raw material 24 in the same manner as in Example 1 using the oxide-coated metal fine particle manufacturing apparatus 40 similar to Example 1 according to the oxide-coated metal fine particle manufacturing process 20 similar to Example 1.₃Ni fine particles 10 coated with. Here, BaTiO₃The supply ratio of powder raw material 24 and Ni powder raw material 22 is BaTiO.₃The mixing ratio of the powder raw material 24 was 5 wt% (7.3 vol%). Moreover, the manufacturing conditions other than the above in this example were exactly the same as in Example 1.

【0051】

In this way, the oxide-coated metal fine particles 10 could be produced with good yield. The oxide-coated metal fine particles 10 produced in this manner have an average particle size of Ni fine particles 12 serving as core particles of 0.3 μm, an average thickness of the oxide coating layer 14 of 3 nm, and oxidation with the outer peripheral surface of the Ni fine particles 12. The material coating layer 14 was oxide-coated metal fine particles that were densely and firmly bonded. The TEM (scanning transmission electron microscope) photograph of the oxide-coated metal fine particles 10 obtained in this example is shown in FIG. 9, and the EDX (energy) of points B1 and B6 of the oxide-coated metal fine particles 10 in the TEM photograph of FIG. 9 is shown. Dispersive X-ray analysis method) The analysis charts are shown in FIGS. 10 and 11. From Fig. 9, it can be seen that one coating particle is composed of a core part (core particle) and a coating layer (film) part of several nm, and from the EDX analysis chart of B1 in Fig. 10, the core part (core particle) is It was found that the Ni particles were several hundred nm and did not contain Ba, Ti, or O, and Ba, Ti, and O appeared in the EDX analysis chart of B6 in Fig. 11. The part (coating layer) is BaTiO of several nm Ba and Ti oxides, that is, only the coating oxide that does not contain the Ni component of the core particles.₃It can be seen that it is a double oxide layer of.

【0052】

As a result, according to the present embodiment, in the obtained oxide-coated metal fine particles 10, the entire outer circumference of the Ni fine particles 12 is densely and uniformly coated with the coating layer 14 of the Ba-Ti-O double oxide, and Ba- It can be seen that the thickness of the coating layer 14 of the Ti-O compound oxide is extremely uniform. Further, it can be seen that according to the present invention, the oxide-coated metal fine particles 10 of the present invention as shown in FIG. 9 can be produced extremely reliably, easily, and with good yield.

【0053】

Although the oxide-coated metal fine particles of the present invention and the method for producing the same have been described in detail above, the present invention is not limited to the above examples, and various improvements and changes are made without departing from the gist of the present invention. Of course, it may be.

【0054】

[Effect of the invention]

As described in detail above, according to the oxide-coated metal fine particles of the present invention, the metal fine particles to be the core particles do not contain the metal element as the main component constituting the metal fine particles (ordinary). The effect is that the oxide coating layer consisting of (including oxides or double oxides or salts of oxygen acids) can provide novel oxide-coated metal microparticles that are solid, preferably completely coated on the entire surface. Play. As a result, the oxide-coated metal fine particles of the present invention have functions (strength, magnetism, etc.) of the metal and functions (environmental suitability, photoactivity, etc.) of the metal, such as applications of artificial bones, cosmetic additives, and catalysts. ), And applications in fields that require adhesion between metals and oxides, such as applications in electrode materials such as fuel cells, can also be achieved.

【0055】

Further, according to the method for producing oxide-coated metal fine particles of the present invention, it is possible to reliably and easily produce new oxide-coated metal fine particles having such a great effect, preferably with good yield. Play.

[Simple explanation of drawings]

[Figure 1]

It is a schematic cross-sectional view which shows the structure of an example of the oxide-coated metal fine particle of this invention.

[Figure 2]

It is a block diagram which shows an example of the manufacturing method of the oxide-coated metal fine particle of this invention.

[Fig. 3]

It is a block diagram which shows an example of the mixing process block of the manufacturing method of the oxide-coated metal fine particle shown in FIG.

[Fig. 4]

(a), (b) and (c) are explanatory views explaining a state in which particles are compounded in the mixing processing block shown in FIG. 3, respectively.

[Fig. 5]

It is a schematic sectional view of one Example of the oxide-coated metal fine particle manufacturing apparatus which carries out the thermal plasma treatment of the oxide-coated metal fine particle manufacturing method of this invention shown in FIG.

[Fig. 6]

It is a TEM photograph of an example of oxide-coated metal fine particles obtained in Example 1 of the present invention.

[Fig. 7]

It is an EDX analysis chart of the point No. 5 of the oxide-coated metal fine particles of the TEM photograph shown in FIG.

[Fig. 8]

It is an EDX analysis chart of the point No. 6 of the oxide-coated metal fine particles of the TEM photograph shown in FIG.

[Fig. 9]

It is a TEM photograph of an example of oxide-coated metal fine particles obtained in Example 2 of the present invention.

[Fig. 10]

It is an EDX analysis chart of the point B1 of the oxide-coated metal fine particles of the TEM photograph shown in FIG.

[Fig. 11]

It is an EDX analysis chart of the point B6 of the oxide-coated metal fine particles of the TEM photograph shown in FIG.

[Explanation of symbols]

10 Oxide-coated metal fine particles 12 Metal particles 14 Oxide coating layer 20 Oxide-coated metal fine particle manufacturing process 22 Metal powder raw material 24 Oxide powder raw material 26 Mixing process 28 Thermal plasma processing process 30 Premixing process 32 Particle composite processing process 34,34a, 34b Composite particles 40 Oxide-coated metal fine particle manufacturing equipment 42 Plasma torch 42a plasma room 42b quartz tube 42c High frequency transmission coil 42c 42d Cooling mantle 42e gas outlet 42f Supply port 42g gas source 43 Thermal plasma (plasma flame) 44 Quartz double tube 44a cooling room 44b quartz tube 44c Cooling mantle 46 Cooling double pipe 46a Cooling room 46b inner tube 46c Cooling mantle 48 quenching tube 48a Coated particle generation chamber 48b inner tube 48c Cooling mantle 50 Powder raw material mixture supply device 52 Product Recovery Department 52a Collection room 52b filter 52c Gas suction / discharge port 52d gas suction source