Method for producing composite tungsten oxide particles

Abstract

To provide a production method of a composite tungsten oxide particle having a smaller number of processes and capable of using facilities of lower introduction costs.SOLUTION: A production method is of a composite tungsten oxide particle expressed by a general formula MxWyOz (0.001≤x / y≤1, 2.2≤z / y≤3.0). The production method of a composite tungsten oxide particle includes: an aerosol formation process of forming an aerosol, being a processing object, containing mixed base powder of W source base powder to be served as a tungsten source and M element source base powder to be served as an M element source; and a heat treatment process of applying a heat treatment at 500 to 1150°C while conveying the aerosol by a carrier gas. The carrier gas is a mixed gas containing an inert gas and H2 of 0.5 to 5 vol.%.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing composite tungsten oxide particles. [Background technology]

[0002] Various near-infrared shielding technologies have been proposed to reduce solar radiation transmittance while maintaining good visible light transmittance and transparency. Among them, near-infrared shielding technologies using inorganic conductive fine particles have the advantages of superior near-infrared shielding properties compared to other technologies, low cost, radio wave transmittance, and high weather resistance.

[0003] For example, Patent Document 1 discloses an infrared-shielding material fine particle dispersion in which fine particles of an infrared-shielding material are dispersed in a medium, and the fine particles of the infrared-shielding material are represented by the general formula M x W y O z (wherein M is one or more elements selected from H, He, alkali metals, alkaline earth metals, rare earth elements, Mg, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Tl, Si, Ge, Sn, Pb, Sb, B, F, P, S, Se, Br, Te, Ti, Nb, V, Mo, Ta, Re, Be, Hf, Os, Bi, and I; W is tungsten; O is oxygen; and 0.001≦x / y≦1, 2.2≦z / y≦3.0), as well as a technique relating to a method for producing the infrared-shielding microparticles. Patent Document 1 also discloses an example of producing an infrared-shielding film, which is a thin-film dispersion of infrared-shielding material microparticles.

[0004] According to Patent Document 1, it is possible to prepare an infrared-shielding material microparticle dispersion having excellent optical properties, such as more efficient shielding of sunlight, particularly light in the near-infrared region, while at the same time maintaining transmittance in the visible light region, etc. For this reason, application of the infrared-shielding particle dispersion disclosed in Patent Document 1 to various applications such as window glass has been considered.

[0005] Various studies have been conducted on methods for producing composite tungsten oxide particles that are useful as a near-infrared shielding material.

[0006] For example, the inventor of Patent Document 1 described in Non-Patent Document 1 that Cs 0.32 proposed a method for synthesizing WO3 nanoparticles. However, the particle size in the synthesis method disclosed in Non-Patent Document 1 was large, and a pulverization process was required to produce nanoparticles. This could increase the number of process steps.

[0007] Non-Patent Document 2 describes Cs by hydrothermal synthesis. x A method for synthesizing WO3 has been disclosed. However, the hydrothermal synthesis method requires a synthesis time of several tens of hours or more. In addition, the hydrothermal synthesis method has a problem in that it requires a large number of steps, such as post-treatment steps.

[0008] Non-Patent Document 3 discloses a synthesis method based on inductively coupled thermal plasma technology. However, this synthesis method requires the introduction of an inductively coupled thermal plasma device, which increases the cost.

[0009] Patent Document 2 describes the chemical formula K x Cs y WO z A process for preparing potassium-cesium-tungsten bronze solid solution particles of the formula: where x+y≦1 and 2≦z≦3, comprising combining a suitable tungsten source with potassium and cesium salts to form a powder mixture, and exposing the powder mixture to a plasma torch under a reducing atmosphere, preferably where the reducing atmosphere is supplied by a sheath gas consisting of a hydrogen / noble gas mixture, is disclosed.

[0010] However, the method disclosed in Patent Document 2 also requires the use of plasma, which increases the cost of introducing a plasma device. Furthermore, the manufacturing method disclosed in Patent Document 2 also discloses that metallic tungsten is mixed in as an impurity. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] International Publication No. 2005 / 037932 [Patent Document 2] Special Publication No. 2012-532822 [Non-patent literature]

[0012] [Non-Patent Document 1] Takeda Hiromitsu, and Kenji Adachi, "Near infrared absorption of tungsten oxide nanoparticle dispersions." Journal of the American Ceramic Society,2007 , Vol.90, Issue 12, P.4059-4061 [Non-Patent Document 2] Guo Chongshen, et al., "Novel synthesis of homogenous CsxWO3 nanorods with excellent NIR shielding properties by a water controlled-release solvothermal process." Journal of Materials Chemistry,2010, Vol.20, Issue38, P.8227-8229. [Non-Patent Document 3] Mamak Marc, et al., "Thermal plasma synthesis of tungsten bronze nanoparticles for near infra-red absorption applications." Journal of Materials Chemistry, 2010, Vol.20, Issue44, P.9855-9857. Summary of the Invention [Problem to be solved by the invention]

[0013] As described above, composite tungsten oxide particles are useful as a near-infrared shielding material. There is a demand for a method for producing composite tungsten oxide particles that can be produced at low cost and with fewer steps.

[0014] However, the conventional methods for producing composite tungsten oxide particles have problems such as the need to introduce special, expensive equipment and the need for many steps, as described above.

[0015] In view of the problems of the conventional techniques described above, an object of one aspect of the present invention is to provide a method for producing composite tungsten oxide particles that can use equipment with low introduction costs and that requires a small number of steps. [Means for solving the problem]

[0016] In one aspect of the invention, a compound of general formula M x W y O z (However, the M element is Cs , W is tungsten, O is oxygen, and 0.001≦x / y≦1, 2.2≦z / y≦3.0), an aerosol forming step of forming an aerosol containing a mixed raw material powder of a W source raw material powder as a tungsten source and an M element source raw material powder as an M element source, which are objects to be processed; The aerosol Flow rate is between 8L / min and 20L / min A heat treatment process in which the heat treatment is performed at 500°C or more and 1150°C or less while transporting the material by a carrier gas; The present invention provides a method for producing composite tungsten oxide particles, wherein the carrier gas is a mixed gas containing an inert gas and 0.5 volume % or more and 5 volume % or less of H2. Effect of the Invention

[0017] One aspect of the present invention provides a method for producing composite tungsten oxide particles that can use equipment with low introduction costs and that requires a small number of steps. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic diagram of a composite material production apparatus that can be suitably used in a method for producing composite tungsten oxide particles according to one embodiment of the present invention. [Diagram 2] FIG. 2 shows a temperature profile in the pipe of the reaction section in Example 1. [Diagram 3] FIG. 3 shows XRD diffraction patterns of the mixed raw material powder and the composite tungsten oxide particles obtained in the examples and comparative examples. [Figure 4] FIG. 4 is an XRD diffraction pattern of the composite tungsten oxide particles obtained in Example 2. [Diagram 5] FIG. 5 is a TEM image of the composite tungsten oxide particles obtained in Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] A specific example of the method for producing composite tungsten oxide particles according to one embodiment of the present disclosure (hereinafter referred to as "the present embodiment") will be described below with reference to the drawings. Note that the present invention is not limited to these examples, but is indicated by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0020] Hereinafter, one configuration example of the method for producing composite tungsten oxide particles of the present embodiment will be described.

[0021] The method for producing the composite tungsten oxide particles of the present embodiment comprises the steps of: x W y O z The method for producing the composite tungsten oxide particles represented by the formula (1) can include the following aerosol formation step and heat treatment step.

[0022] In addition, the M element in the above general formula can be one or more elements selected from alkali metals, alkaline earth metals, rare earth elements, Mg, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Tl, Si, Ge, Sn, Pb, Sb, B, F, P, S, Se, Br, Te, Ti, Nb, V, Mo, Ta, Re, Be, Hf, Os, Bi, and I. In addition, W represents tungsten, O represents oxygen, and x, y, and z preferably satisfy 0.001≦x / y≦1 and 2.2≦z / y≦3.0, respectively.

[0023] The aerosol forming step can form an aerosol containing a mixed raw material powder of a W source raw material powder serving as a tungsten source and an M element source raw material powder serving as an M element source, which is the object to be processed.

[0024] In the heat treatment step, the aerosol formed in the aerosol formation step can be heat-treated at 500° C. or more and 1150° C. or less while transporting the aerosol formed in the aerosol formation step with a carrier gas.

[0025] The carrier gas used in the heat treatment step may be a mixed gas containing an inert gas and 0.5% by volume to 5% by volume of H2. (1) Composite tungsten oxide particles First, the composite tungsten oxide particles produced by the method for producing composite tungsten oxide particles of the present embodiment will be described. (About the composition) The composite tungsten oxide contained in the composite tungsten oxide particles is represented by the general formula M x W y O z The M element, W, O, and x, y, and z in the formula have already been described, so their explanation will be omitted here.

[0026] The composite tungsten oxide can have a tungsten bronze type crystal structure, for example, any of tetragonal, cubic, and hexagonal. The crystal structure of the composite tungsten oxide contained in the composite tungsten oxide particles obtained by the method for producing composite tungsten oxide particles of the present embodiment is not particularly limited, and can have one or more types of crystal structures selected from tetragonal, cubic, and hexagonal.

[0027] However, when the composite tungsten oxide has a hexagonal crystal structure, the composite tungsten oxide particles are particularly improved in light transmittance in the visible light region and in light absorption in the near-infrared region, and therefore the composite tungsten oxide particles preferably contain a composite tungsten oxide having a hexagonal crystal structure.

[0028] Furthermore, when one or more elements selected from Cs, Rb, K, Tl, Ba, and In are used as the M element, it becomes easier to form a hexagonal crystal. For this reason, it is preferable that the M element contains one or more elements selected from Cs, Rb, K, Tl, Ba, and In. In particular, it is more preferable that the M element contains Cs, and it is even more preferable that the M element is Cs.

[0029] Here, the manner in which the M element is arranged when the composite tungsten oxide has a hexagonal crystal structure will be described.

[0030] An octahedron formed of a unit of W and six O, i.e., an octahedron with O atoms at the vertices and W atoms at the center, is assembled into six hexagonal voids (tunnels) composed of O atoms. Then, M element is arranged in the void to form one unit, and a large number of these units are assembled to form a hexagonal crystal structure. When the composite tungsten oxide having a hexagonal crystal structure has a uniform crystal structure, the amount of M element added is preferably 0.2 to 0.5 in terms of the value of x / y, more preferably 0.33. When z / y=3, it is considered that the value of x / y is 0.33, so that M element is arranged in all of the hexagonal voids.

[0031] Similarly, when z / y=3, each of the composite tungsten oxides of cubic and tetragonal crystals has an upper limit of the amount of M element added due to the structure, and the maximum amount of M element added to 1 mole of tungsten is 1 mole in the case of cubic crystals, and about 0.5 moles in the case of tetragonal crystals. Note that the maximum amount of M element added to 1 mole of tungsten in the case of tetragonal crystals varies depending on the type of M element, but the amount that is easy to manufacture industrially is about 0.5 moles as described above. However, these structures are difficult to simply define, and the range is an example that shows a particularly basic range, so the present invention is not limited to this.

[0032] In addition, even a very small amount of M element is added to generate free electrons in the composite tungsten oxide, and the desired infrared absorbing effect can be obtained. For this reason, it is preferable that x / y satisfies 0.001≦x / y≦1.

[0033] In addition, the composite tungsten oxide has a composition in which an M element is added to tungsten trioxide (WO3). Since tungsten trioxide does not contain effective free electrons, the ratio of oxygen to 1 mole of tungsten must be less than 3 in order to achieve infrared absorption. However, in the composite tungsten oxide, free electrons are generated by adding an M element, and the infrared absorption effect can be obtained. Therefore, the ratio of oxygen to 1 mole of tungsten can be 3 or less. However, the crystal phase of WO2 may absorb or scatter light in the visible light region, thereby reducing the absorption of light in the near infrared region. Therefore, from the viewpoint of suppressing the generation of WO2, it is preferable that the ratio of oxygen to 1 mole of tungsten is greater than 2.

[0034] Therefore, it is preferable to satisfy 2.2≦z / y≦3.0 as described above. (About particle size) The particle size of the composite tungsten oxide particles produced by the method for producing composite tungsten oxide particles of the present embodiment is not particularly limited, and can be selected depending on the intended use, etc.

[0035] For example, when used in applications that require maintaining transparency, it is preferable that the particle size is 800 nm or less. This is because particles with a particle size of 800 nm or less do not completely block light due to scattering, and can maintain high visibility in the visible light range while efficiently maintaining transparency at the same time. In particular, when transparency in the visible light range is important, it is preferable to further consider scattering by particles.

[0036] When emphasis is placed on reducing scattering due to such particles, the particle size is preferably 200 nm or less, and more preferably 100 nm or less.

[0037] This is because if the particle size is small, scattering of light in the visible light region of wavelength 400nm to 780nm due to geometric scattering or Mie scattering is reduced, and the infrared shielding film becomes like cloudy glass, and clear transparency cannot be obtained. If the particle size is 200nm or less, the geometric scattering or Mie scattering is reduced and the Rayleigh scattering region is reached. In the Rayleigh scattering region, scattered light is reduced in proportion to the sixth power of the particle size, so scattering is reduced with the decrease in particle size, and transparency is improved. Furthermore, if the particle size is 100nm or less, the scattered light is very small, which is preferable. From the viewpoint of avoiding light scattering, a small particle size is preferable.

[0038] Therefore, the particle size of the composite tungsten oxide particles produced by the method for producing composite tungsten oxide particles of this embodiment can be selected according to the purpose of use.For example, as described above, when it is required to maintain high visibility in the visible light region, the particle size is preferably 800nm ​​or less, more preferably 200nm or less, and even more preferably 100nm or less.The lower limit of the particle size of the composite tungsten oxide particles produced by the method for producing composite tungsten oxide particles of this embodiment is not particularly limited, but can be, for example, 1nm or more.

[0039] The particle diameter of the composite tungsten oxide particles obtained by the method for producing composite tungsten oxide particles of the present embodiment can be determined by observing the particle with, for example, an SEM or TEM, and determining the diameter of the smallest circumscribing circle that circumscribes the particle.

[0040] The particle size of the resulting composite tungsten oxide particles can be selected by adjusting, for example, the size of the aerosol formed in the aerosol formation step described below or the heat treatment temperature in the heat treatment step.

[0041] Since infrared-shielding materials containing the composite tungsten oxide particles obtained by the method for producing composite tungsten oxide particles of this embodiment largely absorb light in the near-infrared region, particularly light with a wavelength of about 1000 nm, the transmitted color tone is often bluish to greenish. (2) Manufacturing method of composite tungsten oxide particles Next, the method for producing the composite tungsten oxide particles of the present embodiment will be specifically described.

[0042] The method for producing composite tungsten oxide particles of the present embodiment is a powder supply type pyrolysis method in which a mixed raw material powder is made into an aerosol and heated while being transported by a carrier gas in a reducing atmosphere, whereby the powder undergoes sublimation, condensation, and precipitation reactions to obtain composite tungsten oxide particles.

[0043] Therefore, the method for producing composite tungsten oxide particles of this embodiment can include an aerosol forming step of aerosolizing a mixed raw material powder obtained by mixing a W source raw material powder serving as a tungsten source and an M element source raw material powder serving as an M element source, and can include a heat treatment step of supplying the aerosol with a carrier gas and heat treating the aerosol at 500°C or higher and 1150°C or lower.

[0044] Each step will be described below. (Aerosol formation process) In the aerosol forming process, the aerosol is formed from a mixed raw material powder obtained by mixing a W source raw material powder as a tungsten source and an M element source raw material powder as an M element source, which are the objects to be processed. Note that being a tungsten source and being an M element source mean that tungsten can be supplied and that the M element can be supplied, respectively.

[0045] The aerosol forming step may be performed by any device capable of forming a dispersion state of the mixed raw material powder and supplying it into the airflow, and the specific means are not particularly limited. For example, the aerosol forming section provided in the composite material manufacturing device that can be used in the manufacturing method of the composite tungsten oxide particles of this embodiment can be composed of a stirring section such as a rotating brush or stirring blade, and a powder supply section including a piston or a screw feeder that sends the mixed powder raw material to the stirring section. The mixed raw material powder supplied from the powder supply section is dispersed into particles that constitute the powder in the stirring section, and an aerosol can be generated from the mixed raw material powder by sending each particle to the carrier gas. The stirring section can select the rotation speed of the brush or stirring blade so that the mixed raw material powder can be dispersed into particles, and it is preferable to rotate it at a high speed.

[0046] In particular, since an aerosol with little aggregation between particles can be stably formed, a rotating brush can be suitably used in the stirring section, and a configuration in which the mixed raw material powder loaded in a reservoir is supplied to the stirring section by a piston can be suitably used in the powder supply section.

[0047] In such an aerosol forming section, the powder concentration in the aerosol changes depending on the transport speed of the powder loaded in the reservoir, for example, the movement speed of the piston.

[0048] The tungsten source is not particularly limited, and a tungsten salt or the like can be used. For example, H2WO4 or ammonium paratungstate can be preferably used.

[0049] In H2WO4, the elements other than tungsten are H (hydrogen) and O (oxygen), and the elements other than tungsten are discharged outside the system in the heat treatment process described below. Therefore, by using H2WO4 as the W source raw material powder that is the tungsten source, composite tungsten oxide particles with reduced impurity contamination can be obtained, and therefore it is preferably used.

[0050] The M element source raw material powder can be, for example, a powder of a salt containing the M element. The type of salt containing the M element is not particularly limited, but one or more types selected from, for example, carbonates, acetates, nitrates, hydroxides, etc. of the M element can be used.

[0051] For example, when the M element is cesium, one or more selected from carbonates, acetates, nitrates, hydroxides, etc. can be used, with carbonates being particularly preferred.

[0052] The ratio of the M element to 1 mole of tungsten in the obtained composite tungsten oxide, i.e., the doping amount, is determined by the mixing ratio of the W source raw material powder and the M element source raw material powder when forming the raw material mixture powder. Therefore, the doping amount can be controlled by adjusting, for example, the amount of the W source raw material powder and the amount of the M element source raw material powder.

[0053] The mixed raw powder may be a mixed raw powder obtained by physically mixing the W source raw powder and the M element source raw powder, or may be a mixed raw powder obtained by dissolving the W source raw powder and the M element source raw powder in a solvent such as water to form a solution, mixing them, and then removing the solvent from the solution by drying, etc. In cases where it is particularly required to suppress the variation in the composition of the obtained composite tungsten oxide particles, a mixed raw powder obtained by dissolving the W source raw powder and the M element source raw powder in a solution, mixing them, and then removing the solvent from the solution by drying, etc. may be preferable.

[0054] The particle size of the mixed raw material powder dispersed in the aerosol forming process is not particularly limited, but the particle diameter is preferably 100 μm or less, more preferably 10 μm or less, and even more preferably 3 μm or less. By making the particle diameter 100 μm or less, it is possible to more reliably sublimate the inside of the particle. The particle diameter of the mixed raw material powder can be measured in the same manner as the particle diameter of the composite tungsten oxide particles described above.

[0055] The aerosol formed in the aerosol forming step can be transported, for example, by a carrier gas and subjected to a heat treatment step. (Heat treatment process) In the heat treatment step, the workpiece is heat treated at 500°C or higher and 1150°C or lower.

[0056] The mixed powder material containing the W source raw material powder and the M element source raw material powder, which is the object to be treated, is evaporated in the process of heating to 500°C or more and 1150°C or less, and is considered to be decomposed into the atomic level. It is considered that the mixed powder material then forms clusters, and undergoes a condensation process as a composite tungsten oxide to form composite tungsten oxide particles. The heat treatment temperature is more preferably 900°C or more and 1150°C or less, and even more preferably 1000°C or more and 1150°C or less.

[0057] It is considered that the composite tungsten oxide is formed by the reaction of tungsten and M element during the decomposition process of the W source raw material powder or the M element source raw material powder, or at a higher temperature. Therefore, in order to sufficiently advance the decomposition of the W source raw material powder or the M element source raw material powder and to suppress the incorporation of impurities into the composite tungsten oxide, it is preferable to perform the heat treatment at a temperature equal to or higher than the decomposition temperature of the W source raw material powder or the M element source raw material powder in the heat treatment process. It is considered that the decomposition of the W source raw material powder or the M element source raw material powder usually occurs at 500°C or lower. Therefore, in the heat treatment process, the aerosol, which is the object to be treated, can be heat treated at 500°C or higher.

[0058] According to the studies of the present inventors, the heat treatment temperature also affects the particle size of the resulting composite tungsten oxide particles. Further studies by the present inventors have shown that the particle size of the resulting composite tungsten oxide particles tends to decrease as the heat treatment temperature increases.

[0059] This is presumably because, when the heat treatment temperature is increased, thermal energy is used to sublimate the generated composite tungsten oxide particles, causing the particles to burst upon sublimation, resulting in particles with a fine particle size.

[0060] Therefore, in order to obtain composite tungsten oxide particles that are particularly fine nanoparticles, the heat treatment temperature is more preferably 900° C. or higher, and even more preferably 1000° C. or higher. That is, when the purpose is to obtain particularly fine nanoparticles, it is more preferable to heat treat the workpiece in the heat treatment step at 900° C. or higher, and even more preferable to heat treat the workpiece at 1000° C. or higher.

[0061] The upper limit of the temperature in the heat treatment process is 1150℃ or less. If heat treatment is performed at a temperature exceeding 1150℃, the metallic W and Cs6W 11 O 36 This is because heterogeneous phases such as the above may occur.

[0062] The aerosol is transported to an electric furnace or the like by a carrier gas, and the above-mentioned heat treatment process can be carried out. Therefore, for example, by controlling the flow rate of the carrier gas, the time of the heat treatment process can be adjusted.

[0063] The time required for the heat treatment step is not particularly limited and can be selected arbitrarily.

[0064] As described above, the mixed powder material containing the W source powder and the M element source powder, which is the object to be treated, evaporates during the process of heating to the heat treatment temperature and is decomposed into atoms. After that, clusters are formed, and the composite tungsten oxide is formed through a condensation process as the composite tungsten oxide.

[0065] The carrier gas used in the heat treatment process is a mixed gas containing an inert gas and 0.5% to 5% by volume of H2. The carrier gas preferably contains 1% to 5% by volume of H2, and more preferably 2% to 4% by volume of H2. The inert gas in the carrier gas is not particularly limited, and one or more types selected from rare gases (noble gases) and nitrogen gas can be used. The inert gas is particularly preferably Ar. For this reason, the carrier gas is preferably a mixed gas of Ar and H2.

[0066] When the carrier gas contains 0.5% by volume or more and 5% by volume or less of H2, composite tungsten oxide particles with few heterogeneous phases can be obtained. When the content of H2 exceeds 5% by volume, reduction proceeds and metal W may precipitate. As described above, hexagonal composite tungsten oxide particles can be suitably used from the viewpoint of increasing the transmittance of light in the visible light region and the absorption of light in the near infrared region. In particular, by making the content of H2 in the carrier gas 0.5% by volume or more, composite tungsten oxide particles having a hexagonal crystal structure can be easily obtained, so as described above, it is preferable to make the content of H2 in the carrier gas 0.5% by volume or more.

[0067] The flow rate of the carrier gas may be any flow rate that can form and maintain an aerosol in the aerosol forming section of the composite material production apparatus described below, and can be appropriately adjusted depending on the size of the composite material production apparatus used to produce the composite tungsten oxide particles.

[0068] For example, the flow rate of the carrier gas is preferably 8 L / min or more and 20 L / min or less. By setting the flow rate of the carrier gas at 8 L / min or more, the mixed raw material powder can be more reliably converted into an aerosol and its form can be maintained. In addition, from the viewpoint of ensuring a sufficient heat treatment time in the heat treatment step, the flow rate of the carrier gas is preferably 20 L / min or less. (3)Composite material manufacturing equipment An example of the configuration of a composite material production apparatus that can be suitably used in the method for producing composite tungsten oxide particles of this embodiment will be described below.

[0069] FIG. 1 is a schematic diagram of a composite material manufacturing apparatus 10. As shown in FIG.

[0070] The composite material manufacturing apparatus 10 can have an aerosol forming section 11, a transporting section 21, a reaction section 31, and a recovery section 41. (Aerosol forming part) The aerosol forming section 11 can include an aerosol generating tube 12, an agitating section 14, and a powder supplying section 16 that supplies mixed raw material powder to the agitating section 14.

[0071] The aerosol generating tube 12 is tubular and has an opening 13 that is connected to the stirring unit 14. The stirring unit 14 has a rotating brush 15. The brush 15 is disposed at the opening 13 so as to be exposed to the aerosol generating tube 12. Also, a stirring blade may be used instead of the brush 15.

[0072] The powder supply unit 16 can have a raw material reservoir 17 for storing the mixed raw material powder, and a piston 18 for sending the mixed raw material powder to the mixing unit 14. The supply speed of the mixed raw material powder can be controlled by the moving speed of the piston 18. A known screw feeder or the like can be used instead of the piston 18.

[0073] Furthermore, the aerosol generating pipe 12 can also be provided with a function of supplying carrier gas to the composite material manufacturing apparatus 10 by connecting a regulator 19 that controls the flow rate of carrier gas supplied from the outside. (Transportation Department) The transport part 21 can be provided between the aerosol formation part 11 and the reaction part 31. Specifically, the aerosol generation tube 12 can be connected to the transport part 21 on the downstream side of the carrier gas, and the transport part 21 can be connected to the piping 32. The transport part 21 can supply the aerosol from the aerosol generation tube 12 to the piping 32. (Reaction section) The above-mentioned heat treatment step can be carried out in the reaction section 31. For this purpose, the reaction section 31 can have, for example, a heat-resistant pipe 32 and a heater 33 for heating the pipe 32, as shown in FIG.

[0074] For example, a ceramic pipe can be used as the pipe 32. From the viewpoint of preventing the inclusion of impurities, it is preferable to use a furnace tube made of Al2O3 with high purity. To reduce the cost of the furnace tube, mullite or the like can also be used.

[0075] The length of the reaction section 31 is not particularly limited, and is preferably selected so that it can be heated to a predetermined temperature in the heat treatment step and so that a sufficient time for the heat treatment step can be secured.

[0076] The length L32 of the pipe 32 in the reaction section 31 is preferably 1 m or more from the viewpoint of heating to a predetermined temperature and ensuring a sufficient time for the heat treatment process. Although there is no particular upper limit to the length L32 of the pipe 32, an excessively long length requires a large amount of carrier gas and increases the size of the apparatus, so that the length is preferably 5 m or less.

[0077] In addition, the diameter D32 of the pipe 32 is not particularly limited, but is preferably 1 cm or more from the viewpoint of productivity. The upper limit of the diameter D32 of the pipe 32 is not particularly limited, but it is preferably selected so that the temperature difference between the center and the wall portion is not excessively large, and the diameter D32 of the pipe 32 is preferably, for example, 20 cm or less.

[0078] The diameter D32 of the pipe 32 means the inside diameter of the pipe 32.

[0079] The pipe 32 of the reaction section 31 usually has a temperature gradient along its longitudinal direction. Therefore, for example, the pipe 32 can be configured so that the temperature is low on the reaction section inlet 32A side and increases toward the reaction section outlet 32B.

[0080] For this reason, it is preferable to set various conditions so that a temperature region with a temperature of 500° C. or higher can be formed in the vicinity of the reaction part outlet 32B.

[0081] In particular, when the workpiece is heat-treated at a temperature of 1000° C. or higher in the heat treatment step described above, it is preferable to set various conditions so that a temperature region with a temperature of 1000° C. or higher can be formed near the reaction section outlet 32B. In addition, in the heat treatment step, when the heat treatment time at a temperature of 1000° C. or higher is set to 1 second or more, it is preferable to set various conditions so that the time the workpiece passes through the temperature region with a temperature of 1000° C. or higher in the reaction section 31 is 1 second or more. Specifically, for example, it is preferable to measure the temperature distribution in the pipe 32 in advance and adjust the supply rate of the carrier gas, etc.

[0082] However, without being limited to the above form, various conditions may be set so that a temperature gradient is not formed along the longitudinal direction of the piping 32, but the temperature in the longitudinal direction of the piping 32 is made almost uniform, and a temperature region above a predetermined temperature is formed.

[0083] In the recovery section 41, the composite tungsten oxide particles produced in the reaction section 31 can be recovered. The configuration of the recovery section 41 is not particularly limited, and can be selected according to the particle size of the composite tungsten oxide particles to be produced, etc. As the recovery section 41, for example, various filters 42 can be used. Alternatively, an electrostatic collector can be used. A pressure adjusting valve 51 may be provided upstream of the recovery section 41 , and a pump 52 may be provided downstream of the recovery section 41 .

[0084] The interior of the composite material production apparatus 10 is preferably sealed, and the gas flow is configured so that the gas flows from the regulator 19 into the aerosol formation section 11 and flows out from the recovery section 41.

[0085] According to the method for producing composite tungsten oxide particles of the present embodiment described above, it is possible to use equipment with low introduction costs, such as an aerosol forming unit and a heater, and the number of steps can be reduced, thereby making it possible to easily produce composite tungsten oxide particles. EXAMPLES

[0086] The present invention will be described below with reference to specific examples, but is not limited to these examples. (1) Evaluation method (1-1) Powder X-ray Diffraction The composite tungsten oxide particles obtained in the following Examples and Comparative Examples were subjected to measurement of powder X-ray diffraction patterns (XRD patterns) using a powder X-ray diffractometer (Bruker, Model: D2 PHASER). The powder X-ray diffraction patterns were measured using CuKα radiation as the radiation source, with a tube voltage of 40 kV and a tube current of 30 mA. (1-2) TEM Image Observation The obtained composite tungsten oxide particles were observed using a transmission electron microscope (TEM, Model: JEM-2011, manufactured by JEOL Ltd.) with an applied voltage of 200 kV. (2) Examples and Comparative Examples [Example 1] Using the composite material manufacturing apparatus 10 shown in FIG. 1, composite tungsten oxide particles were prepared by the following method. 0.32 WO3 particles were produced and evaluated. The specific conditions are explained below.

[0087] The composite material manufacturing apparatus 10 shown in Figure 1 has an aerosol formation section 11, a transport section 21, a reaction section 31, and a collection section 41, and the aerosol formation section 11, the transport section 21, the reaction section 31, and the collection section 41 are connected by piping.

[0088] The aerosol forming section 11 includes an aerosol generating tube 12, a stirring section 14, and a powder supplying section 16 that supplies mixed raw material powder to the stirring section 14. The aerosol generating tube 12 is tubular and includes an opening 13 that is connected to the stirring section 14. The stirring section 14 includes a rotating brush 15. The brush 15 is disposed at the opening 13 so as to be exposed to the aerosol generating tube 12.

[0089] The powder supply section 16 is composed of a raw material reservoir 17 for storing the mixed raw material powder, and a piston 18 for delivering the mixed raw material powder to the stirring section.

[0090] Furthermore, the aerosol generating tube 12 is connected to a regulator 19 that controls the flow rate of a carrier gas supplied from a carrier gas tank (not shown), and also has the function of supplying a carrier gas to the composite material manufacturing apparatus 10 .

[0091] First, a tungsten oxide powder represented by H2WO4 was prepared as a W source raw material powder.

[0092] In addition, cesium carbonate (Sigma-Aldrich) was prepared as the M element source raw material powder. The cesium carbonate was dissolved in water and used as an aqueous solution.

[0093] The Cs2CO3 aqueous solution and H2WO4 powder were mixed so that the mass ratio of the substances was Cs / W = 0.33, and then dried at 100°C for 12 hours to obtain a mixed raw material powder. When the mixed raw material powder was examined with an SEM, it was found to be a powder with a particle size of 1 μm or more and 2 μm or less. (Aerosol formation process) In the aerosol forming section 11, the mixed raw material powder was extruded from the powder supplying section 16 at a supply rate of 2 g / hour toward the brush 15 rotating at a high speed of 1000 rpm or more. The mixed raw material powder dispersed in the carrier gas by the brush 15 becomes an aerosol. The aerosol is transported to the reaction section 31 via the transporting section 21. That is, the aerosol formed in the aerosol forming process is supplied to the heat treatment process.

[0094] The flow rate of the carrier gas was set to 9.6 L / min in order to sufficiently disperse the mixed raw material powder.

[0095] A mixed gas of argon gas and hydrogen gas was used as the carrier gas. Note that, in order to introduce oxygen vacancies into the composite tungsten oxide particles to be produced, 3% H2 / Ar gas containing 3% by volume of hydrogen gas was used.

[0096] The reaction section 31 is equipped with a ceramic pipe 32, and a cylindrical tube having a length L32 of 1 m and a diameter D32 of 13 mm is used as the pipe 32. The diameter D32 means the inner diameter of the pipe 32.

[0097] In the reaction section 31, the temperature of the heater 33 was set to 1000°C. Figure 2 shows the temperature profile in the reaction section 31. The position on the horizontal axis indicates the distance from the reaction section outlet 32B, and is the temperature profile measured along the central axis of the pipe 32. By introducing the carrier gas, the high temperature region heated by the furnace body shifted toward the discharge direction, i.e., toward the reaction section outlet. It is presumed that the precipitation and condensation reaction of the composite tungsten oxide particles progressed in the temperature change region from this high temperature region toward the low temperature region located on the reaction section outlet side.

[0098] The recovery section 41 was provided with a bag filter as the filter 42, and was configured so that the composite tungsten oxide particles formed after the heat treatment step in the reaction section 31 could be recovered.

[0099] Under the above conditions, composite tungsten oxide particles were produced.

[0100] In Example 1, the furnace temperature in the reaction section 31 was set to 1000° C. That is, in the heat treatment step, the supplied aerosol was heated to 1000° C. and heat-treated at 1000° C. The heat treatment time at 1000° C. or higher was 0.8 seconds.

[0101] The composite tungsten oxide particles recovered in recovery section 41 were evaluated. [Example 2] Composite tungsten oxide particles were produced in the same manner as in Example 1, except that the furnace temperature in the reaction section was set to 1100°C.

[0102] That is, in Example 2, the aerosol supplied to the heat treatment step was heated to 1100° C., and heat treatment was carried out at 1100° C. The heat treatment time at 1100° C. or higher was 0.8 seconds. [Comparative Example 1 and Comparative Example 2] Composite tungsten oxide particles were produced in the same manner as in Example 1, except that the furnace temperature in the reaction section was set to 1200° C. (Comparative Example 1) or 1300° C. (Comparative Example 2).

[0103] That is, in Comparative Example 1 and Comparative Example 2, the aerosol supplied to the heat treatment process was heated to 1200°C (Comparative Example 1) and 1300°C (Comparative Example 2), and heat treatment was performed at 1200°C (Comparative Example 1) and 1300°C (Comparative Example 2). [summary] The XRD patterns of the composite tungsten oxide particles obtained in the above-mentioned Example 1, Example 2, Comparative Example 1, and Comparative Example 2 are shown in Fig. 3. As shown in Fig. 3, the obtained composite tungsten oxide particles in Example 1 and Example 2 are composed of almost single-phase Cs 0.32 On the other hand, in Comparative Examples 1 and 2, the furnace temperature was raised to 1200°C and 1300°C, respectively, which strengthened the effect of reduction and increased the proportion of the W phase.

[0104] FIG. 4 shows the XRD patterns of Example 2. In FIG. 4, the data of the powder X-ray diffraction pattern database is also shown. In the case of Example 2, as shown in FIG. 0.32 In addition to the WO3 phase, there is a small amount of Cs 8.5 W 15 O 48 Phase, Cs6W 11 O 36 Phase, Cs4W 11 O 35 phase was confirmed.

[0105] 5(A) and 5(B) show TEM images of the composite tungsten oxide particles obtained in Example 2.

[0106] As shown in Figures 5(A) and 5(B), the TEM images also confirmed that submicron-sized powder of 600 nm or less and nanoparticles of several tens of nm in size were obtained.

[0107] From the above results, it has been confirmed that according to the method for producing composite tungsten oxide particles of the present embodiment, composite tungsten oxide particles can be produced using equipment with low introduction costs, such as an aerosol forming unit and a heater, and the number of steps can be reduced.

Claims

1. General formula M ｘ W ｙ O ｚ (wherein M element is Cs, W is tungsten, O is oxygen, and 0.001≦x / y≦1, 2.2≦z / y≦3.0), an aerosol forming step of forming an aerosol containing a mixed raw material powder of a W source raw material powder serving as a tungsten source and an M element source raw material powder serving as an M element source, which are objects to be processed; A heat treatment process in which the aerosol is heat-treated at 500° C. or more and 1150° C. or less while being transported by a carrier gas having a flow rate of 8 L / min or more and 20 L / min or less, The carrier gas is an inert gas and 0.5% to 5% by volume of H ２ A method for producing composite tungsten oxide particles, the method comprising the steps of:

2. The carrier gas is Ar and H ２ 2. The method for producing composite tungsten oxide particles according to claim 1, wherein the mixed gas is

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