JP2011098867A - Method for producing fine particle of metal oxide or metal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing fine particles of a metal oxide or a metal capable of improving production stability, a production rate and a production efficiency. <P>SOLUTION: The method for producing fine particles of a metal oxide or a metal includes a solution-preparing step for preparing a solution containing a metal component, a mist-generating step for vibrating the solution prepared in the solution-preparing step with a plurality of ultrasonic vibrators to generate a mist out of the solution, and a heating step for heating the mist generated in the mist-generating step under flowing to produce the fine particles of a metal oxide or a metal. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing metal oxide or metal fine particles by heat-treating a mist of a solution containing a metal component.

  In recent years, in the fields of electronic devices, secondary batteries, fuel cells, catalysts, environmental purification materials, biomaterials, and the like, high performance and / or high performance are required, and fine particles have attracted attention.

  There is a gas phase method as a technique for producing fine particles. There is also a plasma method represented by arc plasma at the test equipment level. However, the production capacity including overseas technology is very low, and there is no device for mass production of fine particles.

  In addition, there is a liquid phase method as a technique for producing fine particles. For example, the sol-gel method or the hydrothermal method has equipment that can be industrially mass-produced. However, since a technique for separating fine particles from a solvent is necessary, there are problems such as aggregation in a subsequent drying / firing process. Therefore, recently, a spray pyrolysis method has been proposed in order to compensate for such drawbacks (see, for example, Patent Documents 1 to 11).

  In order to efficiently produce fine particles, it is necessary to atomize the precursor and efficiently collect it.

JP-A-5-253469 Japanese Patent Laid-Open No. 10-218608 Japanese Patent No. 2001-233618 JP-A-8-170112 JP 2003-313607 A JP-A-2005-75691 JP 2007-83111 A JP 2005-183004 A JP 2007-238402 A JP 2003-19427 A JP 2004-161533 A

  By the way, since the conventional method for producing fine particles by spray pyrolysis is a continuous process, it can be used as a mass production apparatus for fine particles. However, it is difficult to generate a large amount of mist with a mist generator using an ultrasonic transducer. There are also problems such as low thermal decomposition efficiency.

  In addition, since the technique of patent document 1-patent document 3 uses the two-fluid nozzle for the mist generator, it is difficult to manufacture the particle | grains of the target particle diameter.

  Moreover, although the technique of patent document 4-patent document 6 is a mist generator by an ultrasonic transducer | vibrator, there is little mist generation amount and it is not suitable for mass production.

  Moreover, although the technique of patent document 7-patent document 9 performs the heat processing of mist with a hot air or a flame, it does not utilize waste heat.

The technologies described in Patent Document 10 and Patent Document 11 include a low melting point compound such as KNO ₃ or NaNO ₃ in an aqueous solution, spray pyrolysis, particle formation, and pulverization to obtain an oxide of 100 nm or less This is a technique for obtaining metal particles. However, since K, Na, and the like are contained in the particles, they cannot be applied to electronic materials, secondary batteries, magnetic materials, biomaterials, and the like.

  An object of this invention is to provide the manufacturing method of the metal oxide or metal microparticle which can improve manufacturing stability, a manufacturing amount, and manufacturing efficiency.

  One aspect of the present invention is a method for producing metal oxide or metal fine particles, a solution generating step for generating a solution containing a metal component, and a plurality of ultrasonic vibrations for the solution generated in the solution generating step. A mist generating step for generating mist from the solution by vibrating with a child, and a heating step for generating metal oxide or metal fine particles by heat treatment while circulating the mist generated in the mist generating step. Is a manufacturing method characterized by According to this, suitable metal oxide or metal fine particles can be suitably generated.

  In another aspect of the present invention, the solution generation step generates an inorganic salt aqueous solution or a mixed solution of water of an organic metal compound and an organic solvent as the solution. According to this, suitable metal oxide or metal fine particles can be generated.

  In another aspect of the present invention, in the solution generation step, a mixed solution of an organic metal compound water and an organic solvent is generated as the solution, and in the mist generation step, the solution is a plurality of ultrasonic transducers. And mist from droplets having a particle size of 100 nm to 3000 nm is generated from the solution. According to this, suitable metal oxide or metal fine particles can be generated.

  In addition, in another aspect of the present invention, the heating step is characterized in that heat treatment is performed in a temperature range of 300 ° C to 900 ° C. According to this, suitable heat treatment can be performed, and suitable metal oxide or metal fine particles can be generated.

  In another aspect of the present invention, in the heating step, a heat treatment using a flame as a heat source is performed. According to this, the heating temperature required for the heat treatment can be ensured.

  In another aspect of the present invention, in the heating step, heat treatment using hot air as a heat source is performed. According to this, the heating temperature required for the heat treatment can be ensured.

  In another aspect of the present invention, in the heating step, a heat treatment using radiant heat by electric heating as a heat source is performed. According to this, the heating temperature required for the heat treatment can be ensured.

  In another aspect of the present invention, in the heating step, a heat treatment using a flame or hot air as a heat source is performed by each of a plurality of gas burners arranged at equal angles. According to this, the heating temperature required for the heat treatment can be ensured with the minimum amount of combustion gas.

  Further, in another aspect of the present invention, in the heating step, a heat treatment using a flame or hot air as a heat source is performed by the gas burner provided with a cover at a position on the upstream end in the mist distribution direction. And According to this, adhesion of mist and / or generated fine particles to the gas burner can be suppressed, and misfiring due to adhesion does not occur, and continuous combustion of the gas burner can be realized.

  In another aspect of the present invention, the heating step generates metal oxide or metal fine particles having a particle size of 50 nm to 500 nm. According to this, suitable metal oxide or metal fine particles can be generated.

  In another aspect of the present invention, in the mist generation step, the amount of mist generated can be up to 4 liters / hour. According to this, heat treatment can be suitably performed, and suitable metal oxide or metal fine particles can be generated.

  In another aspect of the present invention, the production time of the metal oxide or metal fine particles in the heating step is within 1 minute. According to this, suitable heat treatment can be performed, and suitable metal oxide or metal fine particles can be generated.

  In another aspect of the present invention, the mist generation step is characterized in that mist generation is continuously performed while the temperature of the solution is maintained at a constant temperature. According to this, suitable metal oxide or metal fine particles can be continuously generated. It is possible to prevent the produced metal oxide or metal fine particles from having an influence on the particle size and / or chemical composition.

  In another aspect of the present invention, the heating step uses waste heat of the heat used in the heating step. According to this, energy consumption at the time of manufacture can be reduced.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the metal oxide or metal microparticle which can improve manufacture stability, a manufacturing amount, and manufacturing efficiency can be obtained.

It is a figure which shows schematic structure of a microparticle manufacturing apparatus. It is a figure which shows the relationship between the generation | occurrence | production time of a mist generator, and apparatus temperature. It is a figure which shows the relationship between the number of ultrasonic transducer | vibrators, and the amount of mist generation per hour. It is a figure which shows the outline of a heat treatment furnace. (A)-(c) is a figure which shows arrangement | positioning and schematic structure of a gas burner. It is a powder X-ray diffraction pattern of zinc oxide powder. It is a transmission electron micrograph of zinc oxide powder. It is a figure which shows the relationship between the reagent density | concentration of a zinc oxide powder, a particle size, and the manufacturing amount per hour. It is a powder X-ray diffraction pattern of silver powder. It is a scanning electron micrograph of silver powder. It is a powder X-ray diffraction pattern of the cerium oxide powder which added 20 mol% of samarium. It is a scanning electron micrograph of the cerium oxide powder which added 20 mol% of samarium.

  Embodiments according to the present invention will be described below in detail with reference to the drawings. The present invention is not limited to the configurations described below, and various configurations can be employed in the same technical idea. For example, in each configuration (process) described below, a predetermined configuration (process) can be omitted.

(Microparticle production method and microparticle production apparatus)
The production method of the present embodiment is a production method of metal oxide or metal fine particles, for example, nanoparticles, and includes and uses a spray pyrolysis method. The manufacturing method of the present embodiment includes a solution generation step, a mist generation step, and a heating step. In the solution generation process, which is the first process, a solution containing one or more metal components is prepared. For example, zinc acetate is put in a beaker and dissolved in water to prepare a 1 molar aqueous solution.

  In the production method of the present embodiment, various raw material reagents, specifically, an inorganic salt aqueous solution, a mixed solution of water of an organic metal compound and an organic solvent, or the like can be used to generate fine particles. For example, it is possible to use metal nitrate, metal acetate, metal sulfate, metal chloride, metal fatty acid, metal alkoxide, metal acetylacetonate, and simply use an aqueous solution in which the metal is dissolved in nitric acid, hydrochloric acid, sulfuric acid, etc. You can also. As the organic solvent, for example, alcohol can be used. Various alcohols can be used as long as the alcohol is a primary to tertiary alcohol higher than ethanol. For example, ethanol or methanol (primary), isopropyl alcohol (secondary) or tertiary butyl alcohol (tertiary) can be used. In addition, when performing the heating process mentioned later in a predetermined atmosphere, the alcohol (organic solvent) solution of an organometallic compound can also be used.

  In the mist generation process, which is the second process, the solution generated in the solution generation process is vibrated by a plurality of ultrasonic vibrators to generate mist (aerosol) from the solution. Specifically, it is put in an acrylic resin humidifier (see mist generator 110 described later) having 40 2.4 MHz ultrasonic vibrators to generate mist at 4 L / hour. As the ultrasonic transducer, for example, “HM-2412” manufactured by Honda Electronics Co., Ltd. can be adopted.

  In the mist generation step, the number of ultrasonic transducers is not limited to the above 40, and may be increased or decreased according to the volume of the humidifier and the amount of mist generated. The frequency of the ultrasonic vibrator of the humidifier may be 1.6 MHz.

  In order to avoid deterioration of the ultrasonic vibrator due to heat generation due to the generation of mist of the solution, the ultrasonic vibrator may be cooled using a cooling mechanism. Specifically, cooling may be performed by circulating cooling water around the ultrasonic transducer. The cooling can be air cooling by a fan. The temperature of the solution is kept uniform. For example, when operating continuously for 24 hours, the temperature of the solution is kept constant for 24 hours.

  The concentration of mist generated from the solution is set in the range of 0.1 mol to 2 mol per liter. The droplets constituting the mist (mist droplets) have a particle size set to 100 nm to 3000 nm.

  In the heating process as the third process, the mist generated in the mist generation process is heat-treated in a temperature range of 300 ° C. to 900 ° C. while circulating the heating space with the carrier gas. That is, the mist flowing through the heating space is heated in a temperature range of 300 ° C. to 900 ° C., dried, and thermally decomposed. For example, air is used as the carrier gas for circulating the mist. In addition to air, any one of nitrogen gas, argon gas, argon-hydrogen mixed gas, and nitrogen-hydrogen mixed gas may be used. The temperature for heating the mist is appropriately changed according to the crystallization temperature of the generated metal oxide or metal. When the crystallization temperature is taken into account, a predetermined metal or the like may be heated at a temperature outside this temperature range. By the heating process, spherical fine particles having a particle size of 50 nm to 500 nm are generated. The production time of the fine particles in the heating process is within 1 minute. The generated fine particles are collected to obtain a powder in which the fine particles are aggregated (in the case where the fine particles are nanoparticles, a nanopowder).

  Note that the metal oxide or metal fine particles generated in the heating process and recovered by the recovery device 150 are heat-treated (fired) again in a temperature range of, for example, 400 ° C. to 900 ° C. in the firing process. The firing step is performed in a predetermined atmosphere using an electric furnace or the like.

  A schematic configuration of the fine particle manufacturing apparatus 100 used in the manufacturing method (mist generation process and heating process) of the present embodiment will be described with reference to FIG. The fine particle manufacturing apparatus 100 includes a mist generator (aerosol generator) 110, a heat treatment furnace 120, a gas burner 130, a heat exchanger 140, and a recovery device 150. These components of the mist generator 110 are connected by a predetermined pipe or the like. The fine particle manufacturing apparatus 100 has a total height of about 6000 mm (vertical height when viewing FIG. 1 from the front) and a total width of about 3000 mm (horizontal width when viewing FIG. 1 from the front).

  The mist generator 110 is installed on the upper part of the fine particle manufacturing apparatus 100. The mist generator 110 is composed of the humidifier described above, and includes an ultrasonic vibrator, a cooling mechanism (not shown), and the like. The mist of the solution generated by the mist generator 110 flows through the heating space from the upper side to the lower side together with the carrier gas flowing through the heating space formed in the vertical direction in the heat treatment furnace 120.

  In the fine particle manufacturing apparatus 100, the flow rate of the carrier gas for circulating the mist through the heating space in the heat treatment furnace 120 is set in a range of about 1 liter / minute to 30 liter / minute. However, this flow rate may be appropriately changed according to the heat treatment amount of the mist, and is not limited to this range. The type of carrier gas is as described above. The mist flowing through the heating space is heated in the temperature range of 300 ° C. to 900 ° C. by the heat from the plurality of gas burners 130, dried and thermally decomposed.

  In the fine particle manufacturing apparatus 100, spherical fine particles having a particle diameter of 50 nm to 500 nm are generated. The generated fine particles are collected by a bag filter (not shown) provided in the collecting device 150, and a powder in which the fine particles are collected is obtained. The fine particles (powder) can be used for various applications from electronic materials to biomaterials.

  In the fine particle manufacturing apparatus 100, the mist generating device 110 is installed at the upper part. However, the fine particle manufacturing apparatus can be configured such that the mist generating apparatus is installed at the lower part. In this case, the mist generated by the mist generator installed in the lower part of the fine particle production apparatus flows along with the carrier gas flowing from the lower side to the upper side while pushing up the heating space from the lower side to the upper side. , Heated as above, dried and pyrolyzed.

  Here, the relationship between the generation time of the mist generator 110 and the apparatus temperature will be described with reference to FIG. In FIG. 2, the horizontal axis is the mist occurrence time, and the unit is time. The vertical axis is the water temperature inside the mist generator 110, and the unit is ° C. In FIG. 2, “●” indicates a temperature change when the cooling mechanism is installed, and “▲” indicates a temperature change when the cooling mechanism is not installed. If there is no cooling mechanism, the temperature of the aqueous solution becomes 40 ° C. in 5 hours, and the state of the solution changes, which affects the life of the ultrasonic vibrator and the particle size and / or chemical composition of the generated fine particles. Absent. By providing a cooling mechanism, the liquid temperature is maintained at 25 ° C. or lower even for 24 hours, and there is no influence on the life of the ultrasonic vibrator or the particle size and / or chemical composition of the generated fine particles. Can be generated.

  Next, the relationship between the number of ultrasonic transducers of the mist generator (humidifier) 110 and the amount of mist generated will be described with reference to FIG. In FIG. 3, the horizontal axis is the number of ultrasonic transducers, and the unit is n. The vertical axis represents the amount of mist generated per hour, and the unit is liter / hour (L / hr). The amount generated per one is 100 mL. By setting the number of ultrasonic transducers to 40, it was possible to generate up to 4 liters / hour.

  The description is returned to the fine particle manufacturing apparatus 100, and the description of the heat treatment furnace 120 is continued. The heat treatment furnace 120 has a size of about 450 mm in diameter and about 4500 mm in length, for example. As shown in FIG. 4, the heating space formed in the vertical direction in the heat treatment furnace 120 includes a drying zone and a pyrolysis zone. The drying zone on the upper side of the heating space is a side where the mist generated by the mist generator 110 is introduced, and the mist circulating by the carrier gas is dried in this range. The thermal decomposition zone below the heating space is the side from which the generated fine particles are discharged, and the mist dried in the drying zone is thermally decomposed in this range.

  In the heat treatment furnace 120, in order to ensure sufficient drying of the mist, the drying zone of the heat treatment furnace 120 is set in a range of 1000 mm to 2000 mm, but may be appropriately changed according to the heat treatment amount of the mist. It is not limited to the range. In the heat treatment furnace 120, in order to ensure thermal decomposition of the mist, the thermal decomposition zone of the heat treatment furnace 120 is set in a range of 1000 mm to 2000 mm, but may be appropriately changed according to the heat treatment amount of the mist. It is not limited to the range.

  A plurality of gas burners 130 are installed at a lower portion of the heat treatment furnace 120 in a spiral shape at equal intervals. The arrangement of the gas burner 130 will be described later. A supply port 122 for supplying waste heat from the heat treatment furnace 120 is installed in an intermediate portion of the heat treatment furnace 120. In the configuration shown in FIG. 4, the supply port 122 is provided in the vicinity of the boundary between the drying zone and the thermal decomposition zone. The supply port 122 may appropriately change the presence / absence and arrangement position of the supply port 122 according to the heat treatment amount of the mist, and is not limited to such a configuration.

  Supply of waste heat to the supply port 122 is performed via the heat exchanger 140. For example, in the heat treatment furnace 120, waste heat of 200 ° C. from the heat exchanger 140 is reused as heat treatment energy. The speed at which waste heat is supplied from the heat exchanger 140 to the heat treatment furnace 120 is set in a range of wind speeds of 3 m / second to 5 m / second. However, the supply rate may be appropriately changed according to the amount of waste heat, and is not limited to this range. When using waste heat, energy consumption during the production of fine particles can be reduced.

  The arrangement and schematic configuration of the gas burner 130 will be described with reference to FIG. In the heat treatment furnace 120, a plurality of gas burners 130 are arranged at equal angles in the circumferential direction of the heat treatment furnace 120. For example, as shown in FIG. 5, six gas burners 130 are evenly arranged at intervals of 60 ° in the circumferential direction. In FIG. 5A, the six gas burners 130 are denoted by reference numerals “130-1” to “130-6”, respectively. Here, the two adjacent gas burners 130 are arranged so as to be evenly spaced in the height direction of the heat treatment furnace 120. For example, as shown in FIG. 5B, the gas burner 130-1, the gas burner 130-2, the gas burner 130-2, and the gas burner 130-3 are arranged at intervals of 400 mm in the height direction of the heat treatment furnace 120. ing. Similarly, the gas burner 130-5 and the gas burner 130-6 (not shown in FIG. 5B) are arranged at intervals of 400 mm in the height direction of the heat treatment furnace 120. The number of gas burners 130 may be increased or decreased according to the size of the heat treatment furnace 120 or the like. For example, nine gas burners 130 may be evenly arranged at intervals of 40 ° in the circumferential direction. Three gas burners 130 may be equally arranged at intervals of 120 ° in the circumferential direction. Furthermore, the 18 gas burners 130 may be equally arranged at intervals of 20 ° in the circumferential direction. In other words, the plurality of gas burners 130 may be arranged at intervals equally divided by 360 °.

  In addition, since the heat treatment furnace 120 (heating space) illustrated in FIG. 5A has a circular cross-sectional shape, the plurality of gas burners 130 arranged in the heat treatment furnace 120 are in the arranged state. Are arranged at equal intervals (60 ° intervals) at predetermined positions on the circumference along the cross-sectional shape. The cross-sectional shape of the heat treatment furnace 120 (heating space) may be different from a circular shape. Specifically, it may be a polygon, for example, a polygon that is equal to or greater than a regular hexagon. In such a shape, the plurality of gas burners 130 are arranged at equal intervals along this shape. For example, in the case of a regular hexagon, six gas burners 130 may be arranged, for example, at the center or corner of each side. In this case, the gas burners 130 are evenly arranged at intervals of 60 °. The arrangement and number of gas burners 130 can be changed as appropriate as in the case where the cross-sectional shape is circular. Even when the cross-sectional shape of the heat treatment furnace 120 (heating space) is polygonal, the plurality of gas burners 130 may be arranged at equal intervals in the height direction of the heat treatment furnace 120.

As shown in FIG. 5 (c), a plurality of gas outlets 132 are formed on the end face of the tip of the gas burner 130 on the side where the gas burner 130 is attached to the heat treatment furnace 120 in the heating space 120. Is formed. An ignition electrode 134 and a cover 136 are attached to the front end of the gas burner 130 toward the front of the gas outlet 132. Fuel is blown out from the plurality of gas outlets 132, and the blown-out fuel is ignited by the ignition electrode 134. LP gas is used as the fuel for the gas burner 130. Ignition is ON / OFF controlled by PID (a method of controlling by a combination of three of proportional, integral and derivative) with respect to the set temperature. As fuel, city gas may be used in addition to LP gas. The amount of LP gas used by the gas burner 130 is set in the range of 0.8 to 1.5 Nm ³ / hour. For example, it is set to 1 Nm ³ / hour. The gas partial pressure of the gas burner 130 is set such that the ratio of air and LP gas is 1: 1.

  The cover 136 has a shape capable of covering the ignition electrode 134 on the upstream side in the mist flow direction, and is installed so as to cover this. Specifically, in the fine particle manufacturing apparatus 100, since the mist flows from the upper side to the lower side in the heating space in the heat treatment furnace 120, the cover 136 is located above the ignition electrode 134 as shown in FIG. It arrange | positions so that this may be covered. When the mist is distributed from the lower side to the upper side, the cover 136 is disposed on the lower side of the ignition electrode 134. By arranging the cover 136 on the upstream side in the mist flow direction, mist and / or generated fine particles flowing to the ignition electrode 134 do not adhere during the heat treatment, and as a result, continuous ignition is performed. Can be realized.

  The collection device 150 includes a plurality of bag filters. For example, seven bag filters having a diameter of 110 mm and a length of 800 mm are provided. The collecting device 150 sucks the generated fine particles, attaches the sucked fine particles to the bag filter, and collects the fine particles. The amount of air introduced into the recovery device 150 is set to about 3 m / second to 20 m / second, for example. By collecting the fine particles with the collecting device 150, a powder in which the fine particles are gathered is obtained. In addition to this, the collection method by the collection device 150 may use any one of a cyclone, a glass filter, and electrostatic dust collection.

  In addition, the heat treatment in the heating process can be performed using hot air generated by the gas burner 130 as a heat source in addition to a configuration using a flame generated by the gas burner 130 as a heat source. Radiation heat by electric heating can also be used as a heat source. In addition to the heat treatment furnace 120 configured as described above, a microwave induction furnace, an infrared furnace, an arc plasma furnace, a heating furnace using a siliconite heating element, or a heating furnace using a super cantal heating element may be used.

(Experimental result)
Predetermined experiments were conducted on the fine particles or the powders in which the fine particles are aggregated, produced by the manufacturing method of the present embodiment described above. Hereinafter, this result will be described.

  The powder X-ray diffraction result of the zinc oxide powder in which the zinc oxide particles are assembled will be described with reference to FIG. For the measurement, an X-ray diffractometer (XRD-6100) manufactured by Shimadzu Corporation was used. CuKα rays were used as the X-ray source, the applied voltage and the applied current were 40 kV and 30 mA, respectively, and the range of 2θ from 10 ° to 80 ° was measured with a step width of 0.02 °. In FIG. 6, the upper side (see “800 ° C.”) covers the zinc oxide powder produced and recovered by the manufacturing method of the present embodiment, which is again heat treated at 800 ° C. (see the firing step), and the lower side ( “As-prepared”) is intended for zinc oxide powder produced and recovered by the production method of the present embodiment. FIG. 6 shows that the particles (powder) are crystallized into zinc oxide.

  The observation result of the zinc oxide powder by the transmission electron microscope will be described with reference to FIG. For observation, a transmission electron microscope (FX-2000) manufactured by Hitachi, Ltd. was used. As an observation sample, a solution in which zinc oxide powder was dispersed in isopropyl alcohol was dropped onto a copper mesh covered with a collodion film, dried, and then measured at an acceleration voltage of 200 kV. The average particle diameter was obtained by measuring and averaging the diameter of the particles on the photograph. Spherical particles had an average particle size of 100 nm.

  The relationship between the reagent concentration in the aqueous solution of zinc oxide powder, the particle size, and the production amount per hour will be described with reference to FIG. The particle diameter was measured by measuring the diameter of particles on a scanning electron micrograph and averaging them. In FIG. 8, “●” represents the particle size, and “▲” represents the production amount. According to FIG. 8, it can be seen that as the reagent concentration increases, both the particle size and the production per hour increase.

  The powder X-ray diffraction result of the silver powder in which silver particles are aggregated will be described with reference to FIG. For the measurement, an X-ray diffractometer (XRD-6100) manufactured by Shimadzu Corporation was used. CuKα rays were used as the X-ray source, the applied voltage and the applied current were 40 kV and 30 mA, respectively, and the range of 2θ from 10 ° to 80 ° was measured with a step width of 0.02 °. According to FIG. 9, it can be seen that the particles (powder) produced by the production method of the present embodiment are crystallized into silver.

  The observation result of silver powder by a scanning electron microscope will be described with reference to FIG. For the observation, a scanning electron microscope (S-2300) manufactured by Hitachi, Ltd. was used. The observation sample was gold coated with an ion coater and then measured at an acceleration voltage of 25 kV. The average particle diameter was obtained by measuring and averaging the diameter of the particles on the photograph. Spherical particles had an average particle size of 300 nm.

  The powder X-ray diffraction result of the cerium oxide powder in which cerium oxide particles added with 20 mol% of samarium are assembled will be described with reference to FIG. For the measurement, an X-ray diffractometer (XRD-6100) manufactured by Shimadzu Corporation was used. CuKα rays were used as the X-ray source, the applied voltage and the applied current were 40 kV and 30 mA, respectively, and the range of 2θ from 10 ° to 80 ° was measured with a step width of 0.02 °. As can be seen from FIG. 11, the particles (powder) produced by the production method of the present embodiment are crystallized into cerium oxide, and scandium is uniformly added.

  The observation result of the cerium oxide powder added with 20 mol% of samarium by a scanning electron microscope will be described with reference to FIG. For the observation, a scanning electron microscope (S-2300) manufactured by Hitachi, Ltd. was used. The observation sample was gold coated with an ion coater and then measured at an acceleration voltage of 25 kV. The average particle diameter was obtained by measuring and averaging the diameter of the particles on the photograph. Spherical particles had an average particle size of 500 nm.

  According to the production method of the present invention, metal oxide or metal fine particles can be produced and can be provided. The stable generation of mist can contribute to mass production of metal oxides or metal fine particles (powder).

  For this reason, the present invention can improve the quality of the production of fine particles (powder) and is very useful in that the cost can be reduced by mass production. The metal oxide or metal fine particles (powder) produced by the production method according to the present invention are, for example, dielectric materials, ferroelectric materials, semiconductor materials, secondary battery electrode materials, photonic crystals, exhaust gases. It can be used as a catalyst material, a solid oxide fuel cell material, a magnetic material, a photocatalyst material, a phosphor material, a dental filler, a liquid crystal spacer, a laser oscillator, a biomaterial, a drug delivery system, and a conductive paste.

100 Fine particle production device 110 Mist generator (humidifier)
120 heat treatment furnace 130, 130-1 to 130-6 gas burner 140 heat exchanger 150 recovery device

Claims (14)

A method for producing metal oxide or metal fine particles,
A solution generating step for generating a solution containing a metal component;
A mist generating step of generating mist from the solution by vibrating the solution generated in the solution generating step with a plurality of ultrasonic vibrators;
And a heating step of generating a metal oxide or metal fine particles by heat-treating the mist generated in the mist generation step while circulating the mist.   2. The production method according to claim 1, wherein, in the solution generation step, an inorganic salt aqueous solution or a mixed solution of an organic metal compound water and an organic solvent is generated as the solution. In the solution generation step, a mixed solution of an organic metal compound water and an organic solvent is generated as the solution,
2. The manufacturing method according to claim 1, wherein, in the mist generation step, the solution is vibrated by a plurality of ultrasonic vibrators to generate mist from droplets having a particle diameter of 100 nm to 3000 nm from the solution.   In the said heating process, it heat-processes in the temperature range of 300 to 900 degreeC, The manufacturing method of any one of Claims 1-3 characterized by the above-mentioned.   The manufacturing method according to any one of claims 1 to 4, wherein in the heating step, a heat treatment using a flame as a heat source is performed.   The manufacturing method according to any one of claims 1 to 4, wherein in the heating step, heat treatment using hot air as a heat source is performed.   The manufacturing method according to any one of claims 1 to 4, wherein in the heating step, heat treatment is performed using radiant heat generated by electric heating as a heat source.   5. The heat treatment using a flame or hot air as a heat source is performed in each of the plurality of gas burners arranged at an equal angle in the heating step. 6. Manufacturing method.   9. The manufacturing method according to claim 8, wherein in the heating step, a heat treatment using a flame or hot air as a heat source is performed by the gas burner provided with a cover at a position of a tip on the upstream side in the flow direction of mist. .   The manufacturing method according to any one of claims 1 to 9, wherein in the heating step, metal oxide or metal fine particles having a particle diameter of 50 nm to 500 nm are generated.   The manufacturing method according to any one of claims 1 to 10, wherein in the mist generation step, the amount of mist generated can be up to 4 liters / hour.   The production method according to any one of claims 1 to 11, wherein the generation time of the metal oxide or metal fine particles in the heating step is within 1 minute.   13. The mist generation process according to claim 1, wherein the generation of mist is continuously performed in a state where the temperature of the solution is maintained at a constant temperature. Production method.   The manufacturing method according to claim 1, wherein waste heat of heat used in the heating step is used in the heating step.