JP2007290885A - Method for producing inorganic particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new method for producing an inorganic particle by which the particle diameter of the inorganic particle can be smaller. <P>SOLUTION: The method for producing the inorganic particle has a pyrolyzing and primary firing step by heating a raw material solution containing a metal compound and a decomposable additive. It is preferable, but not necessary to be regarded as a restriction, that the decomposable additive has lower pyrolyzing temperature than that of the metal composition. It is preferable, but not necessary to be regarded as a restriction, that the decomposable additive contains at least any one of ammonium chloride, ammonium acetate, ammonium formate, ammonium nitrate, ammonium carbonate, ammonium sulfate and urea. It is preferable, but not necessary to be regarded as a restriction, that pyrolysis and primary firing are performed in the range of 400°C or higher and 1,800°C or lower. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing inorganic particles.

  In recent years, there is a growing need for technologies for producing nano-order particles in a wide range of fields such as electronic materials, pharmaceuticals / cosmetics, and catalysts. For example, in fluorescent materials used in plasma displays, the size of fluorescent particles can be tens of nanometers, which not only dramatically improves resolution but also reduces light scattering and increases energy efficiency. .

  In addition, in the electrodes and electrolyte materials of solid oxide fuel cells and lithium secondary batteries, when the inorganic particles used as materials are made finer to the nano order, the specific surface area increases and the diffusion distance of electrons and ions decreases. Therefore, it is possible to obtain electronic conductivity and ion conductivity far superior to those of bulk materials.

  Examples of conventional techniques for producing nano-order inorganic particles include mechanochemical methods (see, for example, the following Non-Patent Documents 1 and 2), sol-gel methods (see, for example, the following Non-Patent Documents 3 and 4), hydrothermal synthesis methods (for example, Non-patent documents 5 and 6 below), salt-added spray pyrolysis method (for example, see patent documents 1 and 2 below), and electrostatic spray pyrolysis method (for example, see non-patent documents 7 and 8 below).

  However, since the above mechanochemical method uses powders such as carbonates and oxides as starting materials, a long pulverization operation (about several tens of hours) is required to uniformly mix these powders at the molecular level. At the same time, a baking operation at a high temperature is required to crystallize the material. Furthermore, in order to synthesize nanoparticles by this method, it is necessary to add sodium chloride to the raw material powder. After grinding, it must be removed by washing with water, and the manufacturing process becomes multi-stage. There is also a problem that it cannot be completely removed.

  In the sol-gel method, composition control is easy because the synthesis is performed in a liquid phase, but the crystallinity of the particles is low, and the obtained particles must be fired at a high temperature. This causes particle growth. Furthermore, since the synthesis process is a multistage operation, continuous synthesis is difficult.

  In addition, the hydrothermal synthesis method can synthesize highly crystalline inorganic particles at a relatively low temperature. However, even if the raw material is prepared with a stoichiometric composition, the composition of the synthesized material deviates more than that. Therefore, precise control of the composition is very difficult.

  The salt-added spray pyrolysis method involves adding a large amount of sodium chloride, potassium chloride, sodium nitrate or potassium nitrate as a flux to the raw material solution, spray pyrolyzing it at a high temperature, and washing the resulting powder with water. Although it is useful in that it can synthesize inorganic particles of about 20 to 50 nm, there is a problem that it takes much time to remove the added flux by washing and the added substance cannot be completely removed.

  The electrostatic spray pyrolysis method is similar to the spray pyrolysis method in the synthesis principle, but uses electrostatic force for spraying the raw material solution, the raw material solution concentration is several mmol / l, and the spray liquid flow rate is If the condition is about several ml / h, finally, inorganic particles of about several tens of nanometers can be obtained. However, since the raw material solution concentration is very low and the spray liquid flow rate is very small, there is a problem that the production rate is very slow.

  In addition, the present inventors have already announced the spray pyrolysis method (see, for example, Patent Document 3 and Non-Patent Document 9 below) and the improved spray pyrolysis method (see Non-Patent Documents 10 to 13). Of these, Non-Patent Documents 10 to 13 are considered to be applicable to Patent Act Article 30 (1).

JP 2003-19427 A JP 2004-161533 A JP 2004-339028 A T. T. et al. ITO, Q. Zhang, F.M. Saito, Powder Technology, 143-144 (2004), 170-173. Y. Shi, J. et al. Ding, H.C. Yin, J .; Alloys Com. 308 (2000) 290-295 B. J. et al. Hwang, R.A. Santanam, D.A. G. Liu, J .; Power Sources, 97-98 (2001), 443-446. H. -C. Yu, K .; -Z. Fung, T .; C. GuO, W.M. -L. Chang, Electrochimica Acta, 50 (2004), 811-816. Y. Hakuta, H .; Ura, H .; Hayashi, K .; Arai, Mater. Lett. , 59 (2005), 1387 to 1390 R. Viswanathan, R.A. B. Gupta, J. et al. Super. Fluids, 27 (2003), 187-193 T. T. et al. Doi, Y .; Iriyama, T .; Abe, Z .; Ogumi, Chem. Mater. , 17 (2005), 1580 to 1582 I. W. Lenggoro, K .; Okuyama, J. et al. F. de la Mora, N.M. Tohge, J .; Aerosol Sci. , 31 (2000), 121-136 I. Taniguchi, Ind. Eng. Chem. Res. , 44 (2005), 6560-6565 Takeo Tsuji, Tokyo Institute of Technology Graduate School of Science and Engineering, Department of Chemical Engineering, 2005 Master Thesis Presentation, February 13, 2006 Takeo Tsuji, Tokyo Institute of Technology Graduate School of Science and Engineering, Department of Chemical Engineering, 2005 Master Thesis Presentation, 17 February 2006 Takeo Tsuji, Izumi Taniguchi, Abstracts of the 71st Annual Meeting of the Chemical Society of Japan, Lecture Number: P324, 2006 I. Taniguchi, T .; Yabu, Lithium Battery International Meeting, Abstract No. 105, Biarritz, France, June 18-23, 2006

  However, in the spray pyrolysis method described in Patent Document 3 and Non-Patent Document 9, it is still necessary to make the particle size of the inorganic particles smaller.

  Then, in view of the said subject, this invention aims at providing the manufacturing method of a novel inorganic particle.

  A method for producing inorganic particles as a means for solving the above-described problem includes a step of heating, pyrolyzing, and primary firing a raw material solution containing a metal compound and a degradable additive. Here, the “degradable additive” refers to a compound having a thermal decomposition temperature lower than that of a metal compound. Although not limited thereto, the degradable additive preferably contains an ammonium compound such as ammonium chloride, ammonium acetate, ammonium formate, ammonium nitrate, ammonium carbonate, ammonium sulfate, or urea. Although not limited to this, it is desirable that the thermal decomposition and primary firing be performed within a range of 400 ° C. or higher and 1800 ° C. or lower.

  Further, in this means, although not limited, it is desirable to include a step of secondary firing after the step of heating the raw material solution containing the decomposable additive to perform thermal decomposition and primary firing. More preferably, the next firing step is performed within a range of 100 ° C. to 700 ° C.

  In this means, although not limited, the total concentration of the metal components of the metal compound in the raw material solution is desirably in the range of 0.0001 mol / l or more and 10 mol / l or less. However, in the raw material solution, the concentration of the decomposable additive is preferably in the range of 2 to 100 times the total concentration of the metal components of the metal compound.

  As described above, the present invention can provide a novel method for producing inorganic particles.

  Embodiments of the present invention will be described below with reference to the drawings. However, the present invention can be implemented in many different modes and is not limited to the embodiments shown below.

  The method for producing inorganic particles according to the present embodiment includes a step of preparing a raw material solution, a step of performing pyrolysis and primary firing using the raw material solution as mist droplets, and a step of performing secondary firing. May have.

  In addition, as the inorganic particles as the object, LiMn₂O₄LiCoO₂, LiM_xCo_1-xO₂(M = Ni, Mn), LiMPO₄(M = Fe, Mn, Co, Ni), LiNiVO₄, LiCo_yNi_1-yVO₄, LiM_xMn_2-xO₄(M = Co, Cr, Al, Mg, Zn, Ni, Fe), LiNi_xMn_1-xO₂, LiNi_1-xyCo_xM_yO₂(M = Mn, Mg, Al, Ga), Li [Ni_xCo_1-2xMn_x] O₂, MnV₂O₆, Li₄Ti₅O₁₂, CuO, Gd₂O₃, Al₂O₃, ZnO, ZrO₂, TiO₂, SnO₂, CeO₂, SiO₂, MgO, Fe₂O₃, NiO, Y₂O₃, PdO, PbO, Co₃O₄, Mn₃O₄, BaO, PuO, V₂O₅, MoO₃, WO₃, Eu₂O₃, YBa₂Cu₃O_7-x, YBa₂Cu₄O₈, La-Sr-Cu-O, Tl-Ca-BaCu-O, (Bi, Pb) -Sr-Ca-Cu-O, MRuO₃(M = Sr, La), M₂Ru₂O_7-x(M = Bi, Pb, Y, Eu, Gd, Tb, Dy, Ho, Er, Tm), Bi₂CaSr₂Cu₂O_x, Bi₂Ca₂Sr₂Cu₃O_x, ZnO-TiO₂, ZrO₂-SiO₂, MgAl₂O₄, Co₂Mo₃O₈, CoMoO₄, CoAl₂O₄, CuCr₂O₄, PbCr₂O₄, Pb (Zr, Ti) O₃, La_xSr_1-xMnO₃, Ln_xSr_1-xCoO₃(Ln = La, Nd, Gd), Ln_xSr_1-xCo_yFe_1-yO_3-δ (La, Sm, Nd. Gd), La_xSr_1-xGa_yMg_1-yO_3-δ, Mullite (3Al₂O₃-2SiO₂), Mn-Zn ferrite, BaFe₁₂O₁₉, Ba_0.86Ca_0.14TiO₃, BaTiO₃, BaZn_1/3Nb_2/3O₃, PbMg_1/3Nb_2/3O₃, SrTiO₃, PbTiO₃, Zn₂SiO₄, Zr_xSn_1-xTiO₄, NiO-SDC (samaria-doped ceria), NiO-CGO (gadolinia-doped ceria), Gd₃Fe₅O₁₂, BaFe₁₂O₁₉ , NiFe₂O₄, SrTiO₃, LaAlO₃, Eu-doped Y₂O₃, Eu-doped (YGd)₂O₃, CdWO₄, ZnWO₄, CaWO₄, SrWO₄, LaPO₄, Ce-doped LaPO₄, Eu-doped LaPO₄, Ce-Tb-doped LaPO₄, Eu-doped (Gd_xY_1-x)₂O₃, Y₃Al₅O₁₂, YAlO₃, Y₄Al₂O₉, Y₂SiO₅, Ce_1-xTb_xMgAl₁₁O₁₉and so on. The inorganic particles are not limited to oxides. In addition, as sulfides, ZnS, CdS, CuS, CuInS₂, CaLa₂S₄As nitride, Si₃N₄, BN, AlN 3, SiC, etc. can be used.

  The raw material solution includes a metal (hereinafter referred to as “raw metal”) compound (including a metal inorganic compound, a metal organic compound, a metal complex, etc., hereinafter referred to as “metal compound”) and a decomposable addition that are constituent components of inorganic particles. Prepare by dissolving the agent in a solvent. The raw material metal is not particularly limited. For example, lithium (Li), chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), iron ( Fe), aluminum (Al), magnesium (Mg), zinc (Zn), vanadium (V), titanium (Ti), yttrium (Y), and the like can be suitably used. Specific examples of this compound include, but are not limited to, metal inorganic compounds such as nitrates, acetates, formates, chlorides, oxychlorides, etc., and their hydration Things can also be adopted. Moreover, if it is a metal organic compound, although it does not necessarily limit, a metal alkoxide, metal acetylacetonate, a metal carboxylate, etc. are employable. If it is a metal complex, the metal complex which has a various ligand is employable. Of course, the raw material solution may contain a plurality of metal compounds having different raw metal materials, and this is selected depending on the composition of the inorganic particles that are the object of production. In this case, the metal compound is prepared so as to have a stoichiometric ratio of the metal in the inorganic particles.

  Further, the concentration of the present metal compound is not limited, but the total of the metal components is preferably 0.0001 mol / l or more and 10 mol / l or less. Further, it is more preferably 0.001 mol / l or more and 5 mol / l or less. When the total of the metal components is 0.0001 mol / l or more and 10 mol / l or less, there is an advantage that by adding an appropriate amount of degradable additive, particles having a smaller size can be synthesized than without adding the metal component. If the total of the components is 0.001 mol or more and 5 mol / l or less, the advantage becomes more remarkable.

  Degradable additives refer to those having a lower thermal decomposition temperature than metal compounds. This is preferably a compound that does not react with the metal compound. The degradable additive is not particularly limited, and for example, ammonium compounds such as ammonium chloride, ammonium acetate, ammonium formate, ammonium nitrate, ammonium carbonate, ammonium sulfate, and urea can be suitably used. Further, the concentration range is not limited. For example, the concentration range is preferably 2 to 100 times the total concentration of metal components contained in the raw material solution. Moreover, it is more desirable that it is 4 times or more and 50 times or less. When the concentration of the decomposable additive is 2 times or more and 100 times or less of the total concentration of the metal components of the metal compound, there is an advantage that fine particles can be synthesized as compared with the case where no additive is added, and 4 times or more and 50 times. This advantage becomes more conspicuous when the ratio is less than twice.

  The solvent in the raw material solution is not limited as long as it dissolves the metal compound and the degradable additive, but water, alcohols such as methanol, ethanol, propanol, and butanol, ethylene glycol, ethylene oxide, and triethanol Nonaqueous solvents such as amine, xylene, and acetone can be suitably used.

  The process of performing pyrolysis and primary firing with the raw material solution as droplets in a mist state is a step in which the raw material solution is made into a mist state that is fine droplets, decomposed by applying heat to this, and fired. For example, a method using an ultrasonic sprayer, a method using a two-fluid nozzle or a pressure nozzle, and a method using a rotating disk can be suitably used. The method of performing is not limited, but for example, gas burner heating, electric resistance heating, microwave heating or laser heating can be suitably used.

  The particle size of the droplets in the fog state is not limited, but is desirably in the range of 0.01 μm to 500 μm. If the particle size of the droplets is 0.01 μm or more and 500 μm or less, there is an advantage that a large amount of nano-sized particles can be synthesized although it depends on the addition amount of the degradable additive.

  Further, the temperature in the step of performing thermal decomposition and primary firing is preferably in the range of 400 ° C. or higher and 1800 ° C. or lower, although it depends on the composition of the inorganic particles as the target. Moreover, it is more preferable that it is in the range of 600 ° C. or higher and 1500 ° C. or lower. There is an advantage that the additive can be decomposed by setting the temperature to 400 ° C. or higher, and then primary firing can be performed to obtain inorganic particles that are the target of better crystallinity. The benefits are more pronounced. Moreover, there exists an advantage of suppressing the further thermal decomposition of the inorganic particle which is the target object obtained after primary baking by setting temperature as 1800 degrees C or less, and this effect becomes more remarkable by setting it as 1500 degrees C or less.

  Further, as the atmospheric gas in the process of performing thermal decomposition and primary firing, air, oxygen, or a mixed gas of these and an inert gas such as nitrogen or argon can be used when the target inorganic particles are oxides. . In the case of a non-oxide, it is not limited as long as it is other than air, oxygen, or a mixed gas thereof. For example, nitrogen, hydrogen, helium, argon, a mixed gas thereof, or the like can be used.

  Further, the time for the thermal decomposition method depends on the composition of the inorganic particles as the target and is not limited, but is preferably 10 seconds or longer. Moreover, it is more preferable that it is 2 minutes or more. By setting it for 10 seconds or more, the additive is decomposed, and finally, inorganic particles which are the target of good crystallinity can be obtained. By setting the time for 2 minutes or more, this advantage becomes more remarkable.

  The step of performing secondary firing is a step for removing the degradable additive remaining in the inorganic particles obtained by the steps of performing the above thermal decomposition and primary firing, and is particularly limited as long as it can be fired. However, gas burner heating, electrical resistance heating, microwave heating, laser heating, or the like can be used. The step of performing the secondary firing can be omitted when the degradable additive is decomposed and disappears.

  In addition, although the temperature of this baking process changes with compositions, it is preferable that it exists in the range of 100 to 700 degreeC. Moreover, it is more preferable that it exists in the range of 300 degreeC or more and 500 degrees C or less. There exists an advantage that the decomposable additive which remains can be removed by setting it as 100 degreeC or more, and this advantage becomes more remarkable by setting it as 300 degreeC or more. Moreover, it has the advantage that it suppresses the growth of the crystal grain of the inorganic particle which is a target object by setting it as 700 degrees C or less, and this advantage becomes more remarkable by setting it as 500 degrees C or less.

  As the atmospheric gas in the step of performing the secondary firing, air, oxygen, or a mixed gas of these with an inert gas such as nitrogen or argon can be used when the target inorganic particles are oxides. In the case of a non-oxide, it is not limited as long as it is other than air, oxygen, or a mixed gas thereof. For example, nitrogen, hydrogen, helium, argon, a mixed gas thereof, or the like can be used.

  Moreover, although the desirable time of this baking process is dependent on the temperature to bake, it is preferable to exist in the range of 1 minute or more and 180 minutes or less. Moreover, it is more preferable that it is 10 minutes or more and 120 minutes or less. It has the advantage that the remaining degradable additive can be removed by setting it to 1 minute or more, and this advantage becomes more remarkable when it is 10 minutes or more. Further, if it is 180 minutes or less, it has the advantage of suppressing the growth of the inorganic particles as the target particles, and if it is 120 minutes or less, this advantage becomes more prominent.

  As described above, in this embodiment, a raw material solution containing a degradable additive is converted into mist droplets, thermally decomposed and subjected to primary firing, and further subjected to secondary firing, whereby smaller inorganic particles can be obtained.

  In order to confirm the effects of the invention according to the above embodiment, inorganic particles were actually manufactured. This will be described below.

  First, FIG. 1 shows an apparatus for producing inorganic particles used in this example. The apparatus for producing inorganic particles in this example is a 1.7 MHz medical ultrasonic nebulizer 22 (manufactured by OMRON Corporation, E) for converting the raw material solution 21 into a mist-like droplet as a portion for generating a droplet. -U12), a microtube pump 23 (manufactured by EYELA, MP-3N) for supplying the raw material solution 21 to the ultrasonic nebulizer 22, a thermostat 241 and a refrigerator 242, and a mist generated from the ultrasonic nebulizer 22 And a constant temperature water circulation system 24 that keeps the temperature of the liquid droplets constant. In addition, the ultrasonic nebulizer 22 has a liquid droplet formed of an air cylinder 251, a packed column 252, a filter 253, and a flow meter 254 for introducing the liquid droplet generated by the ultrasonic nebulizer 22 into a pyrolysis reactor 31 described later. An introducing means 25 is connected.

Moreover, the manufacturing apparatus in the present embodiment uses a pyrolysis reactor 31 as a part for performing pyrolysis and primary firing, and the pyrolysis reactor 31 further includes a preheating pipe 311 and a preheating pipe 311 having a cylindrical space. And a reaction tube 312 having a cylindrical space that is connected to perform pyrolysis and primary firing. Here, a preheating tube having a cylindrical space with an inner diameter of 20 mm and a length of 500 mm was used, and a reaction tube having a cylindrical space with an inner diameter of 90 mm and a length of 1500 mm was used. In addition, heaters 313 and 314 for adjusting the respective temperatures were disposed around the preheating tube 311 and the reaction tube 312. The droplets made into a mist state by the portion that generates the spray are evaporated, crystallized, dried, pyrolyzed and baked in the process of passing through the preheating tube 311 and the reaction tube 312 to be converted into inorganic particles. . Further, a self-made diffusion electrostatic collector 315 is disposed at the outlet of the reaction tube 312 of the thermal decomposition reactor 31 so that pyrolyzed inorganic particles can be obtained. The diffusion electrostatic collector 315 has a DC voltage power source 3151 for supplying voltage, a cooling trap 3152 for removing NO _x gas contained in the exhaust gas from the reaction tube 312, and a vacuum pump 3153. It is connected.

  Moreover, as a part which performs the secondary baking of the manufacturing apparatus in a present Example, it is obtained by the part which performs the said thermal decomposition and primary baking in an air atmosphere using a 1100 degreeC box furnace (Koyo Thermosystem Co., Ltd., KBF894N). The resulting inorganic particles were subjected to secondary firing.

  In the present embodiment, inorganic particles can be produced using the above configuration. More specifically, first, a raw material solution 21 is prepared, and this sample 21 is introduced into an ultrasonic nebulizer 22 using a microtube pump 23. Then, droplets in a mist state are generated by the ultrasonic nebulizer 22, and the droplets in the mist state are introduced into the thermal decomposition reactor 31 using the droplet introduction means 25. In the pyrolysis reactor 31, the droplets are pyrolyzed through the preheating tube 311 and the reaction tube 312, and are primarily fired to become inorganic particles, which are collected by the diffusion electrostatic collector 315. The obtained inorganic particles are secondarily fired in an air atmosphere using a 1100 ° C. box furnace (manufactured by Koyo Thermo System Co., Ltd., KBF894N). During operation, the preheating tube 311 was kept at 200 ° C. and the reaction tube 312 was kept at 800 ° C., and the pyrolysis and primary firing steps (time to pass through the pyrolysis reactor) were performed in 4.8 minutes. . Further, collection by a diffusion type electrostatic collector was performed by applying a voltage of 9.5 V to a DC voltage power source. Furthermore, the inorganic particles collected by the diffusion type electrostatic collector were subjected to secondary firing at 400 ° C. for 2 hours in an air atmosphere at a heating and cooling rate of 5 K / min.

(Observation of particle surface morphology and measurement of average particle size)
The surface morphology of the fine particles was observed at 30,000 times using a field emission scanning electron microscope (FE-SEM, manufactured by Hitachi, Ltd., S-800). The average diameter (arithmetic) was determined by randomly extracting and measuring 500 particles from the SEM photograph. Furthermore, the morphology of the particles was observed at 10,000 times using a transmission electron microscope (TEM, manufactured by JEOL, JEM-200CX).

(Measurement of specific surface area)
The specific surface area of the fine particles was measured by the BET method. In addition, 150 mg to 250 mg samples dried at 200 ° C. for about 30 minutes were used for the measurement, the measurement was performed 3 to 5 times, and the average value at the time of desorption was used.

(Identification of crystal layer)
The identification of the crystal phase was performed using a powder X-ray diffractometer (manufactured by Philips, PW1700 system). The measurement was performed using a CuKα1 line and a CuKα2 line, and about 50 mg to 80 mg of a sample was performed under the following conditions.

(Comparison of thermal decomposition temperatures of metal compounds and degradable additives)
The decomposition temperature of the metal compound and the degradable additive was measured by thermogravimetric differential thermal analysis (manufactured by Rigaku, TG8120). The measurement was performed in a nitrogen atmosphere at a heating rate of 5 K / min.

Under the above, inorganic particles (LiCr _0.1 Mn _1.9 O ₄ ) were actually produced. This will be described below.

Example 1
In this example, the raw material solutions were lithium nitrate (LiNO ₃ ), manganese nitrate hexahydrate (Mn (NO ₃ ) ₂ .6H ₂ O), chromium nitrate hexahydrate (Cr (NO ₃ ) ₂ .6H _2. O) with a stoichiometric ratio of Li: Cr: Mn = 1: 0.1: 1.9 so that the total concentration of the metal components is 0.045 mol / l, and ammonium chloride as a decomposable additive Each (NH ₄ Cl) was dissolved in distilled water so as to be 0.225 mol / l. That is, ammonium chloride (NH ₄ Cl) having a concentration five times that of the metal compound was added. Further, in the present example, the droplets in a mist state by the ultrasonic nebulizer were entrained with 2 dm ³ / min of air and supplied to the thermal decomposition reactor at about 30 ml / h. The thermal decomposition temperature of lithium nitrate, which is a metal compound, is 666 ° C., the thermal decomposition temperature of manganese nitrate hexahydrate is 246 ° C., and the heat of a 1: 2 (molar ratio) mixture of lithium nitrate and manganese nitrate hexahydrate. The decomposition temperature was 415 ° C., the thermal decomposition temperature of chromium nitrate hexaanhydride was 474 ° C., and the thermal decomposition temperature of ammonium chloride was 247 ° C.

(Example 2)
In this example, inorganic particles were produced under the same conditions as in Example 1 except that the amount of added ammonium chloride (NH ₄ Cl) was dissolved in distilled water so as to be 0.45 mol / l. That is, in the above example, the amount of ammonium chloride (NH ₄ Cl) was added at a concentration 5 times that of the raw material salt, but in this example, it was added at a concentration 10 times.

(Comparative Example 1)
This comparative example is different from Example 1 in that ammonium chloride (NH ₄ Cl) is not added and the concentration of the raw material salt is 0.9 mol / l in total, but other than that is the same as Example 1 Under the conditions, inorganic particles were produced.

(Comparative Example 2)
In this comparative example, the same conditions as in Example 1 were performed except that ammonium chloride (NH ₄ Cl) was not added.

(Result, discussion)
As a result of the examples and comparative examples, each of the obtained inorganic particles was evaluated. For evaluation, observation of the surface morphology of the fine particles, measurement of the average particle diameter and specific surface area, and identification of the crystal phase were performed as described above. FIG. 2 shows the SEM photograph, FIG. 3 shows the TEM photograph, and FIG. 4 shows the results of the powder X-ray diffraction measurement. The average particle diameter and the specific surface area obtained as a result are shown in Table 2 below.

First, the average particle size was 880 nm in Comparative Example 1 while it was 408 nm in Comparative Example 2. This is considered to be an effect by lowering the metal compound concentration. However, in Example 1, it was 89 nm, and the average particle size could be further reduced. As a result, it was possible to confirm a significant decrease in the average particle diameter due to the addition of NH ₄ Cl. In Example 1, the average particle size was 89 nm, whereas in Example 2, the average particle size was 132 nm. This is considered to be an effect of NH ₄ Cl acting as a flux, but in any case, it was confirmed that the average particle size can be greatly reduced by adding NH ₄ Cl as compared with Comparative Examples 1 and 2.

The specific surface area was 7.92 m ² / g in Comparative Example 1, while it could be increased to 9.84 m ² / g in Comparative Example 2, confirming that the particle size was smaller. It was. This can also be considered to be the effect of lowering the concentration of the metal compound, similar to the result of the average particle diameter. However, in Example 1, the specific surface area was 13.3 m ² / g, and the specific surface area could be further increased. It was thus possible to confirm the substantial increase in specific surface area due to the addition of NH 4 _Cl.

2 shows SEM photographs for Comparative Example 2, Example 1, and Example 2, and FIG. 3 shows TEM photographs for Comparative Example 2, Example 1, and Example 2. From this result, It was confirmed that the particles were refined by adding NH ₄ Cl.

FIG. 4 shows the results of powder X-ray diffraction measurement of the inorganic particles obtained in Comparative Example 1, Comparative Example 2, Example 1, and Example 2. In this result, in any case, A diffraction peak of spinel type LiCr _0.1 Mn _1.9 O ₄ could be confirmed.

It is the schematic of the manufacturing apparatus of the inorganic particle which concerns on an Example. It is a figure which shows the SEM photograph of the inorganic particle in an Example and a comparative example. It is a figure which shows the TEM photograph of the inorganic particle in an Example and a comparative example. It is a figure which shows the result of the powder X-ray-diffraction measurement in an Example and a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Manufacturing apparatus, 21 ... Raw material solution, 22 ... Ultrasonic nebulizer, 23 ... Microtube pump, 24 ... Constant temperature water circulation system, 25 ... Droplet introduction means, 31 ... Pyrolysis reactor, 311 ... Preheating tube, 312 ... Reaction Pipe, 313 ... Heater, 314 ... Heater, 315 ... Diffusion type electrostatic collector, 241 ... Constant temperature bath, 242 ... Refrigerator, 3151 ... DC voltage power supply, 3152 ... Cooling trap, 3153 ... Vacuum pump

Claims (10)

  The manufacturing method of the inorganic particle which has the process of heating the raw material solution containing a metal compound and a decomposable additive, and performing a thermal decomposition and primary baking.   The method for producing inorganic particles according to claim 1, wherein the decomposable additive has a thermal decomposition temperature lower than that of the metal compound.   The method for producing inorganic particles according to claim 1, wherein the degradable additive contains an ammonium compound.   The method for producing inorganic particles according to claim 1, wherein the degradable additive contains at least one of ammonium chloride, ammonium acetate, ammonium formate, ammonium nitrate, ammonium carbonate, ammonium sulfate, and urea.   The method for producing inorganic particles according to claim 1, wherein the degradable additive contains ammonium chloride.   The method for producing inorganic particles according to claim 1, wherein the thermal decomposition and primary firing are performed within a range of 400 ° C. or higher and 1800 ° C. or lower.   The manufacturing method of the inorganic particle of Claim 1 which has the process of performing secondary baking after the process of performing thermal decomposition and primary baking.   The method for producing inorganic particles according to claim 7, wherein the step of performing secondary firing is performed within a range of 100 ° C. or more and 700 ° C. or less.   The method for producing inorganic particles according to claim 1, wherein the total concentration of the metal components of the metal compound in the raw material solution is in the range of 0.0001 mol / l to 10 mol / l.   The method for producing inorganic particles according to claim 1, wherein the concentration of the decomposable additive in the raw material solution is in the range of 2 to 100 times the total concentration of the metal components of the metal compound.

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