JP2019048733A - Porous spherical oxide particles and production method thereof - Google Patents

Abstract

To provide porous spherical oxide particles with uniform shape and size comprising open pores having complicated communication paths, and provide a simplified method capable of giving the porous spherical oxide particles stably and efficiently.SOLUTION: There are provided porous spherical oxide particles that are substantially spherical oxide particles the inside of which has open pores separated by particle walls and three-dimensionally communicating, communicating paths of the open pores being random. The porous spherical oxide particles are preferably MnOparticles, MnOparticles, or LiMnOparticles.SELECTED DRAWING: Figure 2

Description

  The present invention relates to porous spherical oxide particles and a method for producing the same, and more specifically, porous spherical oxide particles which can be used for various filters, adsorbents, catalyst carriers, positive electrode materials for secondary batteries, etc. And an efficient manufacturing method.

  Since porous spherical particles having an appropriate pore structure can be widely used as various filters, adsorbents, catalyst carriers, positive electrode materials for secondary batteries, etc., the pore structure, particle shape, particle diameter, etc. Production methods for control are being actively studied.

  Here, in order to obtain porous spherical particles having a particle size of submicron to millimeter order, it is general to mix and granulate base material particles and a pore forming agent, and to fire under high temperature. For example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 11-268909), an aqueous solution of a silica sol, a metal oxide sol and an inorganic salt or a mixture of inorganic salts having a melting point of 400 to 800 ° C. Is then granulated using the heterogeneous mixed liquid, dehydrated and dried, and a temperature range from the melting point of the inorganic salt oxide or the mixture of the inorganic salt oxides formed by calcination of the inorganic salt to a temperature higher by 200 ° C. A method for producing an inorganic porous material has been proposed which is fired and then removing an inorganic salt oxide or a mixture of inorganic salt oxides.

  In the method for producing an inorganic porous body described in Patent Document 1, a columnar entangled structure is formed by the interaction at the interface between the liquid phase of the inorganic salt and the solid of the silica during the firing step. Thus, it is possible to obtain an inorganic porous body having a large average pore diameter and a high porosity, high particle strength, and excellent in water resistance and alkali resistance.

  Moreover, in patent document 2 (Unexamined-Japanese-Patent No. 2014-73927), the manufacturing method of the tetramanganese tetraoxide which has a crystallization process which crystallizes trimanganese tetraoxide from manganese salt aqueous solution without passing manganese hydroxide is mentioned. After mixing the aqueous solution of manganese salt and the alkaline solution in the crystallization step to obtain a slurry in which manganese trioxide is crystallized, a solid content concentration of trimanganese tetraoxide in the slurry exceeds 2% by weight. And tri-manganese tetraoxide having a pore volume of at least 0.1 mL / g for pores with a pore diameter of 0.3 to 2 μm, which are crystallized such that the average residence time of trimanganese tetraoxide in the slurry is 10 hours or less. The production method of is proposed.

  Manganese trioxide is used as a raw material or the like of a lithium manganese-based composite oxide, and mixed with a lithium raw material and another metal raw material to form a lithium manganese-based composite oxide by being fired. Here, if a phenomenon (necking phenomenon) in which the particles of the lithium manganese composite oxide are fused to each other occurs during the firing, there is a problem that the diameter, the shape, etc. of the obtained particles become nonuniform. By using trimanganese tetraoxide having a pore volume of at least 0.1 mL / g for pores with a pore diameter of 0.3 to 2 μm as described in Patent Document 2, adhesion of particles is suppressed. And.

Japanese Patent Application Laid-Open No. 11-268909 JP, 2014-73927, A

  However, in the method for producing an inorganic porous body described in Patent Document 1 above, in addition to the necessity of many steps such as the adjustment of the mixture and the removal of the pore forming agent, the dispersion state of each component in the mixture is Since it affects the pore structure, particle size and size of the inorganic porous material, it is difficult to stably produce a homogeneous inorganic porous material.

  Also in the method of producing trimanganese tetraoxide described in Patent Document 2 above, it is necessary to mix a manganese salt aqueous solution and an alkaline solution to prepare a slurry in which trimanganese tetraoxide is crystallized, and It is necessary to control the solid content concentration of trimanganese tetraoxide in the slurry.

  In addition, in the inorganic porous body described in Patent Document 1 and trimanganese tetraoxide described in Patent Document 2, the shape and communication path of the pores are relatively simple, for example, when used as a filter or an adsorbent There are cases where the ability to hold an object to be captured is not sufficient.

  In view of the problems in the prior art as described above, an object of the present invention is a porous spherical oxide particle having uniform shape and size, in which open spherical pores having complicated communication paths are formed. It is an object of the present invention to provide a simple production method capable of stably and efficiently obtaining substance particles and the porous spherical oxide particles.

  As a result of intensive studies on porous spherical oxide particles and a method for producing the same in order to achieve the above object, the present inventor is very effective to thermally decompose substantially spherical carbonate particles in a water vapor atmosphere. The present invention has been achieved.

That is, the present invention
Substantially spherical oxide particles,
Inside the oxide particles, open pores are formed in three-dimensional communication separated by particle walls,
The communication path of the open pores is random,
And providing porous spherical oxide particles.

  Here, the open pores communicating in a three-dimensional shape are in a complex maze shape throughout the inside of the porous spherical oxide particle, and when the cross section of the porous spherical oxide particle is observed, from the center to the outer edge It is possible to identify irregularly formed open pores throughout. That is, when extremely minute particles intrude into the open pores, they are not easily discharged.

The porous spherical oxide particles of the present invention are preferably Mn ₂ O ₃ particles, Mn ₃ O ₄ particles or LiMn _x O _y particles, and the LiMn _x O _y particles are LiMn ₂ O ₄ particles. Is more preferable. For example, LiMn ₂ O ₄ particles can be used as a positive electrode material of a lithium secondary battery, and Mn ₂ O ₃ particles and Mn ₃ O ₄ particles can be used as a raw material of a lithium manganese-based composite oxide.

  In the porous spherical oxide particles of the present invention, the thickness of the particle wall is preferably 0.1 μm to 1.0 μm. By setting the thickness of the particle wall to 0.1 μm or more, the open pore structure and the strength of the whole porous spherical oxide particles can be secured, and the porous spherical oxide particles can be used in various applications. it can. On the other hand, by setting the thickness of the particle wall to 1.0 μm or less, the thickness of the particle wall can be made sufficiently thin with respect to the size of the porous spherical oxide particles, and the porous spherical oxide particles A large number of open pores can be provided inside the

  In the porous spherical oxide particles of the present invention, it is preferable to have the open pores having a diameter of 50 nm or more. The porous spherical oxide particles having open pores with a diameter of 50 nm or more can sufficiently ensure gas and liquid permeability, and at the same time, fine particulate matter (PM 2.5) which is one of air pollutants. Sufficient pore diameter can be secured for the collection of.

The porous spherical oxide particles of the present invention preferably have a particle size distribution of 0.5 μm to 10 μm and a median diameter (D ₅₀ ) of 1 μm to ₅ μm. For example, when the porous spherical oxide particles are manganese oxides, the storage stability of the lithium manganese composite oxide obtained using the median diameter (D ₅₀ ) of 1 μm or more as the raw material can be increased. it can. In addition, by setting the median diameter (D ₅₀ ) to 10 μm or less, it is possible to enhance the mixing property with other materials and the operability.

  Furthermore, by setting the particle diameter of the porous spherical oxide particles to 0.5 μm or more, three-dimensional maze-like open pores can be formed in the particles, and by setting the particle diameter to 10 μm or less, the surface area is increased. It can be made sufficiently large, and can be suitably used for various filters, adsorbents, catalyst carriers and the like.

  The present invention also provides a method for producing porous spherical oxide particles, which comprises heating carbonate particles in a water vapor atmosphere to thermally decompose the carbonate particles.

  As a result of intensive researches on the method of producing porous spherical oxide particles, the present inventors promoted thermal decomposition reaction of carbonate to oxide by heating in the presence of water vapor and at the same time, grain growth progressed from low temperature It became clear to do. Here, as the grain growth proceeds from a low temperature, porous spherical oxide particles can be produced while maintaining a complex open pore structure.

  The method for producing porous spherical oxide particles of the present invention is an extremely simple method of heating carbonate particles, and no pore forming agent is required. Further, the shape and size of the porous spherical particles can be easily controlled by the carbonate particles as the raw material.

  In addition, in the method for producing porous spherical oxide particles of the present invention, particle growth occurs in a self-flowing manner by thermal decomposition of the inside of the carbonate particles, and the particle growth proceeds at a low temperature. The structure of open pores formed in a state in which open pores separated by particle walls communicate in a three-dimensional manner and the open pore communication path is random) is maintained without being blocked by grain growth.

  In the method for producing porous spherical oxide particles of the present invention, it is preferable to heat at a temperature lower than the thermal decomposition temperature of the carbonate particles in the atmosphere. By heating the carbonate particles in a steam atmosphere, the carbonate particles can be thermally decomposed at a lower temperature than in the case of heating in the atmosphere, and the thermal decomposition at a low temperature makes the grain growth proceed more than necessary Disappearance of the porous structure can be suppressed. In addition, it is preferable from the viewpoint of reducing the energy required for the manufacturing process.

Further, in the method for producing porous spherical oxide particles of the present invention, the carbonate particles are preferably MnCO ₃ particles. By using MnCO ₃ particles as carbonate particles, Mn ₂ O ₃ particles and Mn ₃ O ₄ particles can be easily produced. In addition, Mn ₂ O ₃ particles and Mn ₃ O ₄ particles can be used as raw materials for producing LiMn _x O _y particles.

  Further, in the method for producing porous spherical oxide particles of the present invention, the water vapor pressure is preferably about 1 atm. Here, the water vapor pressure is not particularly limited as long as the effects of the present invention are not impaired, and the composition, shape, size and amount of the carbonate particles used as the raw material, the composition and fines of the porous spherical oxide particles obtained It may be appropriately determined according to the structure etc. However, by setting the water vapor pressure to about 1 atm, the thermal decomposition and the reduction reaction can be promoted more than in the case of less than 1 atm.

Furthermore, in the method for producing porous spherical oxide particles of the present invention, it is preferable to have a re-baking step of reheating in an oxidizing atmosphere after the thermal decomposition. By reheating after pyrolysis, the formation phase of the porous spherical oxide particles can be controlled. For example, if _{the Mn} 3 _{O 4} particles obtained by the thermal decomposition of MnCO ₃ particles, by heating the _Mn 3 _{O 4} particles to 750 ° C., to obtain the _Mn 2 _{O 3} particles having a similar open pore structure be able to. On the other hand, when Mn ₂ O ₃ particles are obtained by thermal decomposition of MnCO ₃ particles, Mn ₃ O ₄ particles can be obtained by heating the Mn ₂ O ₃ particles at 900 ° C. or higher.

  According to the present invention, porous spherical oxide particles having uniform shapes and sizes, which are formed with open pores having complicated communication paths, and the porous spherical oxide particles It is possible to provide a simple manufacturing method that can be stably and efficiently obtained.

It is a schematic external view of the porous spherical oxide particle of this invention. It is a schematic sectional drawing of the porous spherical oxide particle of this invention. It is a SEM photograph of MnCO ₃ particles used as a raw material. It is the schematic of the heating condition in an Example. It is a phase diagram of the baked product obtained by the example and the comparative example. It is a SEM photograph of the appearance of Mn ₃ O ₄ particles obtained at 750 ° C. for 2 hours. 750 ° C., a cross-sectional SEM photograph of the obtained _Mn 3 _{O 4} particles for 2 hours. 750 ° C., a particle size distribution of the obtained _Mn 3 _{O 4} particles for 2 hours. The MnCO ₃ particles having a weight change upon heating. It is a XRD pattern of the baked product obtained by each water vapor partial pressure. Mn ₃ O ₄ by weight change when the particle re fired. It is a XRD pattern of the baked product obtained by re-baking Mn ₃ O ₄ particles. It is a SEM photograph of the appearance of the rebaking thing obtained by rebaking at 750 degreeC for 2 hours. It is a SEM photograph of the section of the rebaking thing obtained by rebaking at 750 ° C for 2 hours. It is a TEM photograph of carbon nanoparticles. It is an external appearance photograph of the glass container immediately after vibrating for 10 seconds. It is an external appearance photograph of the glass container after leaving still for 2 hours. It is a SEM photograph of Mn ₃ O ₄ particles after standing for 2 hours. It is a XRD pattern of Li salt / Mn ₃ O ₄ mixed precursor particle calcination thing. It is a SEM photograph of the appearance of Mn ₂ O ₃ particles processed in the atmosphere at 850 ° C. It is a SEM photograph of a section of Mn ₂ O ₃ particles processed in the atmosphere at 850 ° C. It is a SEM photograph of the appearance of Mn ₂ O ₃ particles processed in the atmosphere at 900 ° C.

  Hereinafter, although representative embodiments of the porous spherical oxide particles and the method for producing the same according to the present invention will be described in detail with reference to the drawings, the present invention is not limited thereto. In the following description, the same or corresponding parts will be denoted by the same reference symbols, and overlapping descriptions may be omitted. Further, since the drawings are for explaining the present invention conceptually, the dimensions of the components shown and their ratios may be different from the actual ones.

(1) Porous Spherical Oxide Particles FIG. 1 and FIG. 2 show a schematic external view and a schematic cross-sectional view, respectively, of the porous spherical oxide particles of the present invention. The porous spherical oxide particles 1 have a substantially spherical shape, and open pores 4 communicated in a three-dimensional manner separated by particle walls 2 are formed.

The communication path of the open pores 4 is random, and the open pores 4 form a three-dimensional maze-like structure inside the porous spherical oxide particles 1. In addition, on the surface of the porous spherical oxide particles 1, a large number of openings 6 of the open pores 4 are formed. Here, the specific surface area of the porous spherical oxide particles 1 varies depending on the circumstances, such as particle size and open pores ^4, the 2.0m ² /g~4.0m 2 / g.

  Moreover, although the thickness of the particle wall 2 changes with places, it is preferable that they are 0.1 micrometer-1.0 micrometer. By setting the thickness of the particle wall 2 to 0.1 μm or more, the structure of the open pore 4 and the strength of the whole porous spherical oxide particle 1 can be secured, and the porous spherical oxide particle 1 can be used in various applications. It can be used for On the other hand, by setting the thickness of the particle wall 2 to 1.0 μm or less, the thickness of the particle wall 2 can be made sufficiently thin with respect to the size of the porous spherical oxide particle 1, and porous spherical A large number of open pores 4 can be provided inside the oxide particle 1.

  The diameter of the open pores 4 is also different depending on the place, but it is preferable to have the open pores 4 having a diameter of 50 nm or more. When the porous spherical oxide particles 1 have open pores 4 with a diameter of 50 nm or more, gas and liquid permeability can be sufficiently ensured, and at the same time, fine particulate matter (PM 2) which is one of air pollutants A sufficient pore diameter can be secured also for the collection of .5).

The porous spherical oxide particles 1 preferably have a particle size distribution of 0.5 μm to 10 μm, and a median diameter (D ₅₀ ) of 1 μm to ₅ μm. For example, when the porous spherical oxide particle 1 is a manganese oxide, the storage diameter of the lithium manganese composite oxide obtained using the median diameter (D ₅₀ ) of 1 μm or more as the raw material is increased. Can. In addition, by setting the median diameter (D ₅₀ ) to 10 μm or less, it is possible to enhance the mixing property with other materials and the operability.

  Furthermore, by setting the particle diameter of the porous spherical oxide particles 1 to 0.5 μm or more, three-dimensional maze-like open pores 4 can be formed in the particles, and by setting the particle diameter to 10 μm or less, The surface area can be made sufficiently large, and can be suitably used for various filters, adsorbents, catalyst carriers and the like.

The composition and crystal structure of the porous spherical oxide particles 1 are not particularly limited, but Mn ₂ O ₃ , Mn ₃ O ₄ or LiMn _x O _y (LiMn ₂ O ₄ , Ni, Co in which the amount of Li is more than the stoichiometric value) And the like, and composites of different elements such as Al and B, and the like are preferable. For example, LiMn ₂ O ₄ particles can be used as a positive electrode material of a lithium secondary battery, and Mn ₂ O ₃ particles and Mn ₃ O ₄ particles can be used as a raw material of a lithium manganese-based composite oxide.

(2) Method of producing porous spherical oxide particles The method of producing porous spherical oxide particles of the present invention is characterized in that the carbonate particles are heated in a water vapor atmosphere to thermally decompose the carbonate particles. It is a thing.

  The method of heating carbonate particles under a steam atmosphere is not particularly limited as long as the effects of the present invention are not impaired. For example, carbonate particles are disposed in the soaking zone of a tubular furnace and distilled water is heated to 100 ° C. or higher. It may be converted into water vapor by the above-mentioned evaporator and introduced into a tubular furnace.

  By heating in the presence of water vapor, the thermal decomposition reaction of carbonate to oxide is promoted and, at the same time, grain growth proceeds from low temperature, porous spherical oxide particles 1 while maintaining the structure of open pores 4 You can get In addition to the fact that the method of producing porous spherical oxide particles of the present invention is an extremely simple method of heating carbonate particles and no pore forming agent is required, the shape of porous spherical oxide particles 1 and The size can be easily controlled by the raw material carbonate particles.

  In addition, thermal decomposition inside the carbonate particle causes particle growth in a self-flowing manner, and the particle growth proceeds at a low temperature, so a three-dimensional labyrinth (open pores 4 separated by particle walls 2 in three-dimensional) The structure of the open pores 4 which are in communication and formed in a state in which the communication path of the open pores 4 is random) is maintained without being blocked by the densification by the grain growth. On the other hand, when carbonates are heated in the atmosphere, grain growth proceeds rapidly, so sintering and densification of particle walls 2 can not be controlled, and heating temperature, heating time, etc. are controlled. Also, it is extremely difficult to obtain a porous spherical oxide particle 1 having a three-dimensional maze-like open pore 4.

  The heating temperature varies depending on the type of carbonate used as the raw material and the desired porous spherical oxide particles, but heating at a temperature lower than the thermal decomposition temperature of the carbonate particles in the atmosphere is preferable. By heating the carbonate particles in a steam atmosphere, the carbonate particles can be thermally decomposed at a lower temperature than in the case of heating in the atmosphere, and the thermal decomposition at a low temperature makes the grain growth proceed more than necessary Disappearance of the porous structure can be suppressed. In addition, it is preferable also from a viewpoint of reducing the energy required for a manufacturing process. The heating temperature is preferably 100 ° C. or more lower than the thermal decomposition temperature of the carbonate particles in the air, and more preferably 150 ° C. or more lower.

The type of carbonate particles is not particularly limited as long as the effect of the present invention is not impaired, and various conventionally known carbonate particles can be used, but MnCO ₃ particles are preferably used. By using MnCO ₃ particles as carbonate particles, Mn ₂ O ₃ particles and Mn ₃ O ₄ particles can be easily produced. In addition, Mn ₂ O ₃ particles and Mn ₃ O ₄ particles can be used as raw materials for producing LiMn _x O _y particles.

Here, in the case of using spherical MnCO ₃ particles having a particle diameter of 0.4 μm to 10 μm as carbonate particles, the thermal decomposition temperature in the air is about 900 ° C., but in a water vapor atmosphere, 600 ° C. to 800 ° C. The thermal decomposition can proceed at a temperature of about ° C. In the temperature range, when the heating temperature is high, Mn ₃ O ₄ particles can be obtained in a short time, and even at 650 ° C., Mn ₃ O ₄ particles can be obtained by prolonging the heating time. . On the other hand, when the heating temperature is as low as about 600 ° C., basically Mn ₂ O ₃ particles can be obtained.

  The heat treatment time may be suitably determined in accordance with the type of carbonate particles and the desired porous spherical oxide particles 1, but, for example, homogeneous porous spherical oxide particles 1 by heat treatment for 2 hours to 12 hours You can get

  The water vapor pressure used for the heat treatment is not particularly limited as long as the effects of the present invention are not impaired, and the composition, shape, size and amount of carbonate particles used as a raw material, and porous spherical oxide particles 1 obtained The thermal decomposition and the reduction reaction can be promoted by setting the water vapor pressure to approximately 1 atm, as compared with the case where the water vapor pressure is approximately 1 atm.

Furthermore, the composition of the porous spherical oxide particles 1 can be controlled by reheating in an oxidizing atmosphere after the thermal decomposition. For example, when Mn ₃ O ₄ particles are obtained by thermal decomposition of MnCO ₃ particles, the Mn ₂ O ₃ particles having the same open pore 4 structure can be obtained by heating the Mn ₃ O ₄ particles at ̃750 ° C. You can get it. On the other hand, when Mn ₂ O ₃ particles are obtained by thermal decomposition of MnCO ₃ particles, Mn ₃ O ₄ particles can be obtained by heating the Mn ₂ O ₃ particles at 900 ° C. or higher. The oxidizing atmosphere is not particularly limited as long as the effects of the present invention are not impaired. For example, the atmosphere can be used.

  As mentioned above, although the typical embodiment of the present invention was described, the present invention is not limited only to these, and various design changes are possible, and all the design changes are included in the technical scope of the present invention. Be

<< Example >>
Heat treatment was performed in a water vapor atmosphere using a horizontal tubular furnace, using MnCO ₃ particles of which the particle diameter is equalized to 0.4 μm to 10 μm as a raw material. The SEM photograph of the MnCO ₃ particles is shown in FIG. The MnCO ₃ particles were approximately spherical, and when the particle size distribution was measured by a laser diffraction scattering method, the median diameter (D ₅₀ ) was 2.7 μm.

  The schematic of a heating condition is shown in FIG. Distilled water was supplied at 1 mL / min to an evaporator heated to 100 ° C. or higher to obtain steam, and then the steam was introduced into the tubular furnace. In addition, the outlet side of the core tube was released, and the supply of water vapor was performed only for the holding time at the heating temperature. That is, the water vapor pressure at the time of heat treatment is 101 kPa (1 atm).

A phase diagram of a fired product obtained when the heating temperature is set to 600 ° C. to 750 ° C. and the holding time is set to 1 hour to 12 hours is shown in FIG. Depending on the conditions, Mn ₂ O ₃ or Mn ₃ O ₄ is obtained, and Mn ₃ O ₄ tends to be generated when the heating temperature is high and the holding time is long. In addition, powder X-ray diffraction (XRD) was used for phase identification. For the XRD measurement, a D2 PHASER manufactured by Bruker AXS was used, and a CuKα ray with a tube output of 300 W was used, and the step width was 0.02 ° and the scanning speed was 1 second / step.

Scanning electron microscope (SEM) photographs of the appearance and cross section of the Mn ₃ O ₄ particles obtained at a heating temperature of 750 ° C. and a holding time of 2 hours are shown in FIGS. 6 and 7, respectively. The cross section of the particles was processed by ion milling. For scanning electron microscopy (SEM), JSM-6010LA manufactured by JEOL was used, and for ion milling, IB-09020CP manufactured by JEOL was used. A large number of openings are formed on the surface of the Mn ₃ O ₄ particles, and three-dimensional open pores communicating with one another separated by particle walls are formed in the interior from the cross-sectional photograph, and the open pore communication path Is found to be random (three-dimensional maze-like). Further, from the cross-sectional photograph, the thickness of the particle wall is in the range of 0.1 μm to 1.0 μm, and open pores with a diameter of 50 nm or more are formed.

Also, 750 ° C. The heating temperature, shows the results of measurement by a laser diffraction scattering method particle size distribution of the obtained Mn ₃ O ₄ particles retention time as 2 hours in FIG. The median diameter (D ₅₀ ) of the Mn ₃ O ₄ particles was 3.2 μm. The particle size distribution was measured by laser diffraction / scattering method using MT3300EXII manufactured by Microtrac Bell, dispersing the sample in a 0.05 mass% aqueous sodium hexametaphosphate solution. The specific surface area of the particles obtained by the _{N 2} adsorption measurements pore volume of 3.0 m ² / g, the particles obtained by mercury porosimetry was 0.4 mL / g. For measurement of the specific surface area, 3 Flex manufactured by micromeritics was used, and it was calculated by BET method from measurement of N ₂ adsorption amount in liquid N ₂ at −196 ° C., and AutoPore IV manufactured by micrometritics was used for mercury intrusion method.

Next, in order to confirm that the thermal decomposition temperature of carbonate particles shifts to the low temperature side due to the water vapor atmosphere, when flowing dry air into the core tube and when flowing water vapor at 4.7 kPa or 42 kPa With respect to and, the weight change at the time of raising the temperature of the MnCO ₃ particles was measured. The obtained result is shown in FIG. A drop in the thermal decomposition temperature due to water vapor is confirmed, and it is found that it is remarkable particularly when water vapor flows at 42 kPa. In addition, TG / DTA6200 manufactured by SII was used for thermogravimetric analysis (TG), and the sample was placed on a platinum sample pan and measured in a dry air flow (300 mL / min) at a temperature rising rate of 5 ° C./min. Moreover, in the case of flowing water vapor, TG-DTA / HUM-1 manufactured by Rigaku was used, and air containing 4.7 kPa or 42 kPa of water vapor was flowed at 300 to 430 mL / min.

Next, in order to confirm the influence of the water vapor partial pressure on the phase of the obtained oxide particles, powder X-ray diffraction (XRD) measurement of the fired product obtained with the water vapor partial pressure in the core tube of 10 kPa to 101 kPa (1 atm) Did. In addition, the heating temperature at the time of baking was 750 degreeC, and holding time was 2 hours. The obtained result is shown in FIG. When the water vapor partial pressure is 50 kPa or less, Mn ₂ O ₃ particles are formed, and at 101 kPa (1 atm), Mn ₃ O ₄ particles are formed.

Next, 750 ° C. The heating temperature was re-calcined in air for resulting Mn ₃ O ₄ particles retention time as 2 hours. The change in weight when the particles are refired is shown in FIG. The recalcining temperature shows a weight increase due to the oxidation reaction up to 750 ° C., and shows a weight decrease due to the reduction reaction above 900 ° C. The powder X-ray-diffraction (XRD) result of the re-baking thing which performed the re-baking process for 2 hours at 750 degreeC or 1000 degreeC is shown in FIG. It can be seen that Mn ₂ O ₃ forms at 750 ° C. and Mn ₃ O ₄ forms at 1000 ° C., and the phase of the porous spherical oxide particles can be freely controlled by the re-sintering treatment. In addition, TG / DTA6200 made from SII was used for thermogravimetric analysis (TG), and the sample was mounted on a platinum sample pan and measured in the air at a temperature rising rate of 5 ° C./min.

The SEM photographs of the appearance and the cross section (processed using ion milling) of the refired product obtained by rebaking at 750 ° C. for 2 hours are shown in FIGS. 13 and 14, respectively. It can be seen that the structure of the openings on the surface of the particle and the inside of the particle maintain the state before re-baking.

Next, regarding the Mn ₃ O ₄ particles obtained at a heating temperature of 750 ° C. and a holding time of 2 hours, their nanoparticle adsorption performance was evaluated. After 10 mg of carbon nanoparticles and 15 mL of 2-propanol were placed in a glass container, the carbon nanoparticles were dispersed by ultrasonic dispersion. The transmission electron microscope (TEM) photograph of the used carbon nanoparticle is shown in FIG. In addition, JEM-2100F made from JEOL was used for the transmission electron microscope (TEM).

Thereafter, 100 mg of Mn ₃ O ₄ particles (heating temperature: 750 ° C., holding time 2 hours) were inserted, shaken for 10 seconds, and allowed to stand for 2 hours. The external appearance photograph of the glass container immediately after shaking for 10 seconds and after leaving still for 2 hours is each shown in FIG.16 and FIG.17. Immediately after shaking for 10 seconds, the entire dispersion medium is black due to the presence of carbon nanoparticles, but after standing for 2 hours, the carbon nanoparticles are trapped in Mn ₃ O ₄ particles and precipitated at the bottom of the glass container You can see how it is.

The SEM photograph of Mn ₃ O ₄ particles after standing for 2 hours is shown in FIG. Although many carbon nanoparticles are considered to be trapped inside the Mn ₃ O ₄ particles, the presence of carbon nanoparticles can also be confirmed from the surface (arrows in FIG. 18).

Next, conversion of Mn ₃ O ₄ particles to LiMn ₂ O ₄ particles was attempted, using Mn ₃ O ₄ particles as a raw material. Specifically, LiOH / ethanol and Mn ₃ O ₄ particles (heating temperature: 750 ° C., holding time 2 hours) are put in a beaker, ethanol is evaporated while stirring to reprecipitate Li salt, Li salt / Mn After obtaining the ₃ O ₄ mixed precursor particles, the Li salt / Mn ₃ O ₄ mixed precursor particles were calcined in the air at 400 ° C. or 600 ° C. for 2 hours.

Powder X-ray diffraction (XRD) results of the calcined product obtained by calcining the Li salt / Mn ₃ O ₄ mixed precursor particles in air at 400 ° C. or 600 ° C. for 2 hours are shown in FIG. In the XRD pattern are peak due to LiMn ₂ O ₄ is confirmed, the _Mn 3 _{O 4} particles as a raw material, it from _Mn 3 _{O 4} particles are possible conversion to LiMn ₂ O ₄ particles was confirmed.

«Comparative example»
Using the same MnCO ₃ particles as in the example as a raw material, heat treatment was performed in the atmosphere using a horizontal tubular furnace shown in FIG. A phase diagram of a fired product obtained when the heating temperature is 850 ° C. to 900 ° C. and the holding time is 2 hours to 12 hours is shown in FIG. As in the case of the example, depending on the conditions, Mn ₂ O ₃ or Mn ₃ O ₄ is obtained, and Mn ₃ O ₄ tends to be generated when the heating temperature is high and when the holding time is long. In addition, powder X-ray diffraction (XRD) was used for phase identification.

SEM photographs of the appearance and cross section of Mn ₂ O ₃ particles obtained at a heating temperature of 850 ° C. and a holding time of 2 hours are shown in FIGS. 20 and 21, respectively. The cross section of the particles was processed by ion milling. The densification of the particles by firing is in progress, almost no open pores are observed on the surface of the particles, and the open pores communicating in a three-dimensional shape separated by the particle walls are also collapsed in the cross-sectional photograph. When the heating temperature is 900 ° C. and the holding temperature is 2 hours, Mn ₃ O ₄ particles are obtained, but densification progresses more and the open pore structure disappears completely (FIG. 22).

Here, from the above results and the results shown in FIG. 9, the thermal decomposition temperature from MnCO ₃ to Mn ₃ O ₄ in the atmosphere is about 900 ° C., and the high processing temperature (densification of particles) is avoided. If the water vapor atmosphere is not used, porous spherical oxide particles having a three-dimensional maze-like open pore structure can not be obtained.

Incidentally, 900 ° C. The heating temperature, where the specific surface area of the obtained _Mn 3 _{O 4} particles retention time as 2 hours was measured by _{N 2} adsorption measurement was 1.0 m ² / g.

Using the same method as the example, the nanoparticle adsorption performance was evaluated for the Mn ₃ O ₄ particles obtained at a heating temperature of 900 ° C. and a holding time of 2 hours. 16 and 17 show outline photographs of a glass container immediately after shaking for 10 seconds after being charged with 10 mg of carbon nanoparticles, 15 mL of 2-propanol and 100 g of Mn ₃ O ₄ particles, and after standing for 2 hours. Immediately after shaking for 10 seconds, the entire dispersion medium turns black due to the presence of carbon nanoparticles, and the situation does not change significantly even after standing for 2 hours. From the results, it is understood that carbon nanoparticles can not be trapped efficiently when using Mn ₃ O ₄ particles obtained by atmospheric treatment.

1 ··· Porous spherical oxide particles,
2 ... particle wall,
4 ... open pore,
6 ... opening.

Claims (11)

Substantially spherical oxide particles,
Inside the oxide particles, open pores are formed in three-dimensional communication separated by particle walls,
The communication path of the open pores is random,
Porous spherical oxide particles characterized by Being Mn ₂ O ₃ particles, Mn ₃ O ₄ particles or LiMn _x O _y particles,
The porous spherical oxide particles according to claim 1, characterized in that The LiMn _x O _y particles are LiMn ₂ O ₄ particles,
The porous spherical oxide particles according to claim 2, characterized in that The thickness of the particle wall is 0.1 μm to 1.0 μm,
The porous spherical oxide particle according to any one of claims 1 to 3, characterized in that Having the open pores with a diameter of 50 nm or more,
The porous spherical oxide particles according to any one of claims 1 to 4, characterized in that Having a particle size distribution of 0.5 μm to 10 μm and a median diameter (D ₅₀ ) of 1 μm to ₅ μm,
The porous spherical oxide particles according to any one of claims 1 to 5, characterized in that Heating the carbonate particles under a steam atmosphere to pyrolyze the carbonate particles;
A method of producing porous spherical oxide particles characterized by Heating at a temperature lower than the thermal decomposition temperature of the carbonate particles in the atmosphere,
The manufacturing method of the porous spherical oxide particle of Claim 7 characterized by these. Said carbonate particles are MnCO ₃ particles,
The manufacturing method of the porous spherical oxide particle of Claim 7 or 8 characterized by these. Water vapor pressure to be approximately 1 atm,
The manufacturing method of the porous spherical oxide particle in any one of the Claims 7-9 characterized by these. Having a rebaking step of reheating the carbonate particles after the thermal decomposition under an oxidizing atmosphere,
The manufacturing method of the porous spherical oxide particle in any one of the Claims 7-10 characterized by these.