Barium titanate spherical powder production method

Abstract

The invention relates to the technical field of barium titanate production and preparation, in particular to a barium titanate spherical powder production method. The preparation method comprises the following steps: preparing and atomizing a precursor solution, then spraying the atomized precursor solution into a high-temperature reaction furnace for flame melt crystallization, and then carrying out gradient cooling and spherical curing in a cooling area of the high-temperature reaction furnace, and finally, grading and collecting the prepared spherical barium titanate powder through a collecting system to obtain spherical barium titanate powder with uniform particle size, and carrying out surface functionalization treatment on the collected spherical barium titanate powder through a coating unit to obtain surface-coated spherical barium titanate powder. The precursor solution is subjected to solvent evaporation, thermal decomposition and flame melting in a high-temperature reaction furnace to form barium titanate crystal nucleuses, the crystal nucleuses naturally shrink to form balls under the driving of surface tension, the defect of mechanical damage of a traditional solid phase method or the defect of agglomeration of a liquid phase method is overcome, the crystal defects of the crystal nucleuses are reduced, and meanwhile particle size distribution is more uniform.

Description

Technical Field

[0001] The invention relates to the technical field of barium titanate production and preparation, and in particular to a method for producing spherical barium titanate powder. Background Art

[0002] Barium titanate is an inorganic substance with the chemical formula BaTiO3. It is a strong dielectric compound material with a high dielectric constant and low dielectric loss. It is one of the most widely used materials in electronic ceramics and is known as the "pillar of the electronic ceramics industry." It is easily soluble in concentrated sulfuric acid, hydrochloric acid, and hydrofluoric acid, and insoluble in hot dilute nitric acid, water, and alkali. Barium titanate is a uniformly molten compound with a melting point of 1618°C. When the temperature changes, the symmetry of the barium titanate crystal also changes, resulting in a phase transition.

[0003] The existing traditional solid-phase synthesis method for preparing barium titanate powder has problems such as regular particle morphology, severe agglomeration, and a wide particle size distribution range, resulting in poor density during component sintering, unstable dielectric properties, and high dielectric loss. Although the existing liquid-phase method for preparing barium titanate can improve particle morphology, it requires a complex precipitation-washing-drying process and high-temperature calcination, resulting in high energy consumption and easy introduction of impurities to cause secondary agglomeration, resulting in excessively high production costs. Therefore, it is of great significance to develop a preparation technology for barium titanate spherical powder with controllable morphology, uniform particle size, and suitable for industrial production. Summary of the Invention

[0004] The purpose of the present invention is to solve the problems in the background technology and provide a method for producing spherical barium titanate powder. Through the process of melt crystallization-rapid condensation, the atomization, melting and condensation processes are precisely controlled to achieve the prepared spherical barium titanate powder with controllable morphology and uniform particle size.

[0005] The above technical objectives of the present invention are achieved through the following technical solutions: A method for producing spherical barium titanate powder comprises the following steps: S1. Preparation and atomization of precursor solution: preparing barium titanate precursor solution, and then atomizing the precursor solution into micron-sized droplets through an atomizing nozzle; S2, melt crystallization, a high temperature reactor is provided with a gradient temperature rising zone, and the atomized precursor solution is sprayed into the gradient temperature rising zone of the high temperature reactor to perform flame melt crystallization; S3, gradient cooling and spherical solidification, after the crystallized barium titanate crystals enter the cooling section of the high-temperature reactor, they complete the crystal form transformation of barium titanate through rapid condensation-slow cooling solidification, while reducing lattice defects; S4, classification and collection, the barium titanate spherical powder after cooling and solidification is sequentially classified and collected by cyclone separation and bag dust removal to obtain barium titanate spherical powder with appropriate particle size; S5. Surface functionalization: The collected barium titanate spherical powder is passed through a coating unit and introduced with silane coupling agent vapor to obtain a surface coating layer, thereby improving the dispersibility of the barium titanate spherical powder.

[0006] Preferably, the precursor solution preparation in step S1 is easy to prepare and the barium titanate precursor is configured according to a Ba:Ti molar ratio of 1:1 during atomization, and the steps include: S11, dissolving tetrabutyl titanate in an ethanol solution with a concentration of 50%-70%, adding acetic acid, stirring evenly, and then inputting into a titanium salt storage tank, wherein the volume ratio of tetrabutyl titanate to the ethanol solution is 1:3-1:5, and the volume ratio of acetic acid to tetrabutyl titanate is 1:5-1:10; S12, adding barium nitrate to a 70%-80% ethanol solution, stirring the mixture evenly, and then inputting the mixture into a barium salt storage tank, wherein the volume ratio of the barium nitrate to the ethanol solution is 1:3-1:5; S13, transporting the solutions in the titanium salt storage tank and the barium salt storage tank to a mixing tank for uniform mixing by ultrasonic stirring, wherein the ultrasonic frequency is 40 kHz and the stirring time is 30 min; S14. Use an atomizing nozzle to atomize the precursor solution into micron-sized droplets. The atomizing gas is compressed air with a pressure of 0.3-0.5 MPa and a gas flow rate of 10-30 m³ / h.

[0007] Preferably, the combustion zone of the high-temperature reactor in the melt crystallization in step S2 is a gradient combustion structure, in which an evaporation zone, a flame zone and a melting zone are sequentially arranged along the airflow direction, the temperature of the evaporation zone is 300-500°C, the temperature of the flame zone is 500-800°C, and the temperature of the melting zone is 800-1200°C; the temperature of the evaporation zone is 300-500°C, in which the ethanol and aqueous solution in the precursor solution evaporate to form Ba(NO3)2-Ti(OC4H9)4 composite solid particles; the temperature of the flame zone is 500-800°C, in which Under the action of the temperature in the flame zone, Ti(OC4H9)4 decomposes into TiO2, and Ba(NO3)2 decomposes into BaO, while releasing NO2 and CO2 gases to form TiO2-BaO composite crystal nuclei; the temperature in the melting zone is 800-1200℃, and under the action of the temperature in the melting zone, BaO and TiO2 undergo a solid-phase reaction to form BaTiO3 spherical nuclei. Due to the uniformity of the mixing of the precursor solution, the reaction activation energy is reduced by 30%-40% during the solid-phase reaction. At the same time, the particle size of the spherical core grains can be controlled by controlling the residence time in each area.

[0008] Preferably, in the step S3 gradient cooling and spherical solidification, rapid condensation is cooling with circulating cooling water, the cooling water flow rate is 20-60m³ / h, and the air flow temperature in the rapid condensation zone is ≤600°C; slow cooling solidification is cooling with cooling air, the cooling air flow rate is 50-150m³ / h, and the air flow temperature in the slow cooling solidification zone is ≤200°C; the air flow temperature in the high-temperature reactor in the rapid condensation zone can be reduced to about 600°C in a short time, BaTiO3 can form a spherical core wrapped in an amorphous shell, inhibiting abnormal crystal growth, and the crystal is slowly cooled in the slow cooling solidification zone, completing the transformation of the crystal phase from cubic phase to tetragonal phase, reducing lattice defects and internal stress.

[0009] Preferably, the production method is further configured with a preparation device, including a high-temperature reactor, a precursor preparation system, a heating system, a cooling system and a collection system; the high-temperature reactor is provided with a gradient heating zone and a cooling zone, the gradient heating zone includes an evaporation zone, a flame zone and a melting zone in sequence, a feed port is provided at the top position of the high-temperature reactor, and a discharge port is provided at the bottom position, the precursor preparation system is connected to the interior of the high-temperature reactor through the feed port, the heating system is arranged at the gradient heating zone position, the cooling system is connected to the cooling zone, and the interior of the high-temperature reactor is connected to the collection system through the discharge port; the high-temperature reactor is the main preparation area, and the preparation of BaTiO3 is completed through the internal gradient heating zone and cooling zone, the precursor preparation system is mainly used for the preparation of the precursor solution and to improve the uniformity of its mixed atomization, the heating system is used to provide a gradient temperature difference area to the gradient heating zone, the cooling system is used to cool the prepared BaTiO3, and the collection system is used to collect BaTiO3 particles and perform surface functionalization treatment on them.

[0010] Preferably, the precursor preparation system includes a titanium salt storage tank, a barium salt storage tank and a mixing tank, the titanium salt storage tank and the barium salt storage tank are connected to the mixing tank through a pipeline, an ultrasonic agitator is provided inside the mixing tank, and a feeding high-pressure pump is also provided on the mixing tank. The mixed raw materials are transported to the atomizing nozzle through the feeding high-pressure pump and then sprayed into the high-temperature reactor, and the atomizing nozzle is provided on the feed port; after the raw materials in the titanium salt storage tank and the barium salt storage tank are transported to the mixing tank, the ultrasonic agitator in the mixing tank will ultrasonically mix and stir the two raw materials evenly to form a precursor solution, which is then atomized and sprayed into the high-temperature reactor through the atomizing nozzle for high-temperature reaction treatment.

[0011] Preferably, the heating system includes an evaporation heating device, a combustion heating device and a melting heating device, the evaporation heating device is arranged at the evaporation zone, the combustion heating device is arranged at the flame zone, and the melting heating device is arranged at the melting zone; the evaporation heating device is heated by an electric heating wire, and a ring-shaped electric heating wire is installed on the inner wall of the evaporation zone; the combustion heating device is fuel combustion heating, including a fuel tank and an oxygen tank, a combustion nozzle is provided on the flame zone, and the fuel tank and the oxygen tank are both connected to the combustion nozzle; The melting temperature rising device is heated by silicon-molybdenum rods, and the melting temperature rising device is provided with several groups of silicon-molybdenum rods arranged circumferentially on the inner side wall of the melting zone; the evaporation temperature rising device on the evaporation zone is heated by electric heating wires, which can raise the temperature of the evaporation zone to 300-500°C, the oxygen-fuel ratio of the combustion temperature rising device in the flame zone is 1.0-1.5, the fuel uses natural gas, the injection flow rate is 3-20m³ / h, the flame zone temperature can be raised to 500-800°C, and the melting temperature rising device in the melting zone is heated by silicon-molybdenum rods, which can raise the temperature of the melting zone to 800-1200°C.

[0012] Preferably, the cooling system includes a rapid condensation unit and a slow cooling and solidification unit, the inner jacket of the cooling zone of the high-temperature reactor is provided with a circulating water cooling pipe, and the circulating water cooling pipe is connected to the circulating water cooling device of the rapid condensation unit; the slow cooling and solidification unit is arranged at the discharge port, and the slow cooling and solidification unit is provided with a cooling pipe at the discharge port, and a spiral guide channel is provided inside the cooling pipe, and the slow cooling and solidification unit is also provided with a cooling fan connected to the cooling pipe; liquid cooling circulating water flows in the circulating water cooling pipe in the inner jacket of the cooling zone, and the temperature drop time in the cooling zone can be controlled by increasing the flow rate of the liquid cooling circulating water. After passing through the cooling zone, the prepared BaTiO3 particles will enter the cooling pipe on the discharge port for slow cooling and solidification. The spiral guide channel design in the cooling pipe can make the airflow form turbulence therein, enhance the heat transfer coefficient, and enhance the heat transfer efficiency.

[0013] Preferably, the collection system includes a cyclone separator, a bag dust collector and a collection fan; the cyclone separator includes a straight cylinder section and a conical cylinder section, the length of the conical cylinder section is longer than the straight cylinder section, a separation inlet is provided on the side wall of the straight cylinder section and is connected to the air outlet, a separation outlet is also provided at the top of the straight cylinder section, and a star-shaped discharge valve is also provided at the bottom of the conical cylinder section; an air flow plate with a plurality of holes is provided inside the bag dust collector box, filter bags are installed at the openings of the air flow plate, and a hopper and a dust removal inlet are provided at the bottom of the bag dust collector. The dust removal inlet is connected to the separation outlet, and a dust removal outlet is also provided at the top of the bag dust collector to be connected to the collection fan; the cyclone separator can separate large particles of material, and the remaining fine particles will enter the bag dust collector for secondary collection. The structural design of graded collection can greatly improve the collection accuracy, and the collection fan can provide a negative pressure environment for the entire collection system, so that the airflow in the high-temperature reactor can flow out stably to avoid flame backflow. At the same time, the negative pressure environment provided enables the collection system to better collect BaTiO3 spherical powder.

[0014] Preferably, a coating unit is provided at the outlet position of the collection system, and a coating inlet, a coating area and a coating outlet are sequentially provided on the coating unit; a coating nozzle is provided between the coating inlet and the coating area, and the diameter of the coating nozzle is much smaller than the inner diameter of the pipe of the coating inlet; the coating area and the coating outlet are connected through a coating throat, and the inner wall between the coating area and the coating throat is set to contract inwardly, and the inner wall of the coating throat and the coating outlet is set to expand outwardly; a coating material inlet pipe is also provided on the side wall of the coating area, and the coating material inlet pipe is connected to a storage tank for storing the coating material through a pipeline; the coating unit adopts a Venturi effect design, and the airflow with BaTiO3 spherical powder will reach the coating nozzle position through the coating inlet, and when it passes through the coating inlet, the airflow will reach the coating nozzle position through the coating inlet. When passing through the coating nozzle, the cross-sectional area of ​​the channel becomes smaller and the flow rate of the airflow increases. After the faster airflow passes through the coating nozzle and reaches the coating area, the pressure in the coating area will be lower than the external pressure. At this time, the storage tank for storing the coating material transports KH-570 silane coupling agent vapor to the coating area through the coating material inlet pipe. At this time, the silane coupling agent vapor and the BaTiO3 spherical powder airflow will be mixed and coated in the coating area due to the pressure difference. Since the cross-sectional area of ​​the coating throat suddenly decreases, the silane coupling agent vapor and the BaTiO3 spherical powder airflow will be further intensely mixed and coated at the coating throat. After the coating is completed, the BaTiO3 spherical powder after surface functionalization treatment will be discharged through the coating outlet. The dispersibility of the BaTiO3 spherical powder after surface functionalization treatment is greatly improved.

[0015] In summary, the beneficial effects of the present invention are: 1. The present invention discloses a method for producing spherical barium titanate powder. The precursor solution is ultrasonically mixed in a mixing tank and then atomized through an atomizing nozzle to form micron-sized droplets. In a high-temperature reactor, BaTiO3 crystal nuclei are formed through solvent evaporation, thermal decomposition, and flame melting. Driven by surface tension, the crystal nuclei naturally shrink into spheres, avoiding mechanical damage in traditional solid-phase methods or agglomeration defects in liquid-phase methods, and reducing crystal defects in the crystal nuclei. 2. The method for producing spherical barium titanate powder described in the present invention controls the droplet size by adjusting the atomization pressure, combines the step-by-step heating in the gradient heating zone with the graded cooling of the collaborative cooling system to regulate the growth and phase transition of the crystal, thereby achieving the adjustability of the particle size within the range of 1μm-50μm and making the particle size distribution more uniform. 3. The method for producing spherical barium titanate powder of the present invention comprises introducing silane coupling agent vapor into a coating unit to conduct surface functionalization treatment with the BaTiO3 spherical powder airflow, thereby forming a coating layer on the surface of the BaTiO3 spherical powder, thereby reducing the water contact angle of the spherical powder, improving its dispersibility, and extending its sedimentation half-life in polar solvents; 4. The method for producing spherical barium titanate powder described in the present invention adopts a production process of precursor configuration-atomization-melt crystallization-graded cooling-collection-surface functionalization treatment, which abandons the traditional mixing-calcination-ball milling process, greatly improving production efficiency and capacity. The coarse particles that have not been completely reacted can be returned to the precursor preparation system for re-atomization after cyclone separation, thereby improving energy recovery rate and reducing energy loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the overall structure of the preparation device of the present invention; Figure 2 It is a schematic structural diagram of the heating system of the present invention; Figure 3 It is a schematic structural diagram of the cooling system of the present invention; Figure 4 It is a schematic structural diagram of the collection system of the present invention; Figure 5 It is a schematic diagram of the coating unit structure of the present invention.

[0017] Markings in the figure: 1-high temperature reaction furnace, 11-gradient heating zone, 111-evaporation zone, 112-flame zone, 113-melting zone, 12-cooling zone, 13-feed port, 14-discharge port, 2-precursor preparation system, 21-titanium salt storage tank, 22-barium salt storage tank, 23-mixing tank, 24-ultrasonic agitator, 25-feeding high-pressure pump, 26-atomizing nozzle, 3-heating system, 31-evaporation heating device, 32-combustion heating device, 321-fuel tank, 322-oxygen tank, 323-combustion nozzle, 33-melting heating device, 4-cooling system, 41-rapid condensation unit, 411-circulating water cooling pipe, 412-circulating water cooling device , 42-slow cooling and solidification unit, 421-cooling pipe, 422-spiral guide channel, 423-cooling fan, 5-collection system, 51-cyclone separator, 511-straight cylinder section, 512-conical cylinder section, 513-separation inlet, 514-separation outlet, 515-star discharge valve, 52-bag collector, 521-air flow plate, 522-filter bag, 523-hopper, 524-dust removal inlet, 525-dust removal outlet, 53-collecting fan, 54-coating unit, 541-coating inlet, 542-coating nozzle, 543-coating area, 544-coating throat, 545-coating outlet, 546-coating material inlet pipe, 547-storage tank. DETAILED DESCRIPTION

[0018] The following specific embodiments are merely explanations of the present invention and are not limitations of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to the embodiments as needed. However, as long as they are within the scope of the claims of the present invention, they are protected by patent law.

[0019] The present invention will be described in detail below with reference to the accompanying drawings using embodiments.

[0020] Example 1

[0021] A method for producing spherical barium titanate powder comprises the following steps: Step 1: Preparation and atomization of precursor solution, Titanium salt solution: Add 1 L of tetrabutyl titanate, 4 L of ethanol solution, and 150 mL of acetic acid to the titanium salt storage tank and stir to mix evenly; Barium salt solution: Add 1 kg of barium nitrate and 3 L of ethanol solution to the barium salt storage tank and stir until evenly mixed; Atomization: The raw materials in the titanium salt storage tank and the barium salt storage tank are introduced into a mixing tank for ultrasonic dispersion mixing at a frequency of 30 kHz and a stirring time of 30 min. The raw materials are then introduced into an atomizing nozzle 26 for atomization spraying at a pressure of 0.5 MPa and a gas flow rate of 10 m³ / h to obtain atomized droplets with a D50 of 10 μm. Step 2: melt crystallization, the temperature of the evaporation zone in the high-temperature reactor is 400°C, the temperature of the flame zone is 750°C, and the temperature of the melting zone is 1050°C; Step 3: Gradient cooling and spherical solidification, Rapid condensation, cooling water flow rate is 50m³ / h, cooling zone outlet temperature is 550℃; Slow cooling solidification, cooling air flow rate is 100m³ / h, the temperature in the cooling pipe is 180℃; Step 4: Classification and collection: After cyclone separation and bag dust removal, uncoated BaTiO3 spherical powder with a particle size of about 10 μm is collected, with a sphericity of 99.1% and a dielectric constant ε=3800.

[0022] Example 2

[0023] The difference from the above embodiment 1 is that a method for producing spherical barium titanate powder includes the following steps: Step 1: Preparation of base powder: atomized droplets with a D50 of 5 μm, an evaporation zone temperature of 400°C, a flame zone temperature of 750°C, and a melting zone temperature of 950°C in a high-temperature reactor, to obtain uncoated BaTiO3 spherical powder with a particle size of 4.8±0.8 μm; Step 2: Surface functionalization: The vapor flow rate of KH-570 silane coupling agent in the coating unit was 0.3 m³ / h, and the coating temperature was 110°C. BaTiO3 spherical powder with a coating layer thickness of 35 nm was obtained, the water contact angle was 28°, and the dispersion stability was improved to 8 hours without obvious sedimentation.

[0024] Example 3

[0025] According to a method for producing barium titanate spherical powder, a preparation device is also provided, including a high-temperature reactor 1, a precursor preparation system 2, a heating system 3, a cooling system 4 and a collection system 5; a gradient heating zone 11 and a cooling zone 12 are provided inside the high-temperature reactor 1, and the gradient heating zone 11 includes an evaporation zone 111, a flame zone 112 and a melting zone 113 in sequence, a feed port 13 is provided at the top of the high-temperature reactor 1, and a discharge port 14 is provided at the bottom, the precursor preparation system 2 is connected to the inside of the high-temperature reactor 1 through the feed port 13, and the heating system 3 is provided at the position of the gradient heating zone 11 The cooling system 4 is connected to the cooling zone 12, and the interior of the high-temperature reactor 1 is connected to the collection system 5 through the discharge port 14; the high-temperature reactor 1 is the main preparation area, and the preparation of BaTiO3 is completed through the internal gradient heating zone 11 and the cooling zone 12. The precursor preparation system 2 is mainly used for the preparation of the precursor solution and to improve the uniformity of its mixed atomization. The heating system 3 is used to provide a gradient temperature difference area to the gradient heating zone 11. The cooling system 4 is used to cool the prepared BaTiO3, and the collection system 5 is used to collect BaTiO3 particles and perform surface functionalization treatment on them.

[0026] According to, the precursor preparation system 2 includes a titanium salt storage tank 21, a barium salt storage tank 22 and a mixing tank 23. The titanium salt storage tank 21 and the barium salt storage tank 22 are connected to the mixing tank 23 through pipelines. An ultrasonic stirrer 24 is provided inside the mixing tank 23. A feeding high-pressure pump 25 is also provided on the mixing tank 23. The mixed raw materials are transported to the atomizing nozzle 26 through the feeding high-pressure pump 25 and then sprayed into the high-temperature reactor 1. The atomizing nozzle 26 is provided on the feed inlet 13; after the raw materials in the titanium salt storage tank 21 and the barium salt storage tank 22 are transported to the mixing tank 23, the ultrasonic stirrer 24 in the mixing tank 23 will ultrasonically mix and stir the two raw materials to form a precursor solution, which is then atomized and sprayed into the high-temperature reactor 1 through the atomizing nozzle 26 for high-temperature reaction treatment.

[0027] According to the invention, the heating system 3 includes an evaporation heating device 31, a combustion heating device 32 and a melting heating device 33. The evaporation heating device 31 is arranged at the evaporation zone 111, the combustion heating device 32 is arranged at the flame zone 112, and the melting heating device 33 is arranged at the melting zone 113; the evaporation heating device 31 is heated by an electric heating wire, and a ring-shaped electric heating wire is installed on the inner wall of the evaporation zone 111; the combustion heating device 32 is heated by fuel combustion, and includes a fuel tank 321 and an oxygen tank 322. A combustion nozzle 323 is arranged on the flame zone 112, and the fuel tank 321 and the oxygen tank 322 are both connected to the combustion nozzle 323; the melting The heating device 33 is a silicon-molybdenum rod heating device, and the melting heating device 33 is provided with several groups of silicon-molybdenum rods arranged circumferentially on the inner wall of the melting zone 113; the evaporation heating device 31 on the evaporation zone 111 is heated by an electric heating wire, which can increase the temperature of the evaporation zone 111 to 300-500°C. The oxygen-fuel ratio of the combustion heating device 32 in the flame zone 112 is 1.0-1.5, and the fuel uses natural gas with an injection flow rate of 3-20m³ / h. The temperature of the flame zone 112 can be increased to 500-800°C. The melting heating device 33 in the melting zone 113 is a silicon-molybdenum rod heating device, which can increase the temperature of the melting zone 113 to 800-1200°C.

[0028] According to, the cooling system 4 includes a rapid condensation unit 41 and a slow cooling and solidification unit 42, the inner jacket of the cooling zone 12 of the high-temperature reactor 1 is provided with a circulating water cooling pipe 411, and the circulating water cooling pipe 411 is connected to the circulating water cooling device 412 of the rapid condensation unit 41; the slow cooling and solidification unit 42 is arranged at the discharge port 14, and the slow cooling and solidification unit 42 is provided with a cooling pipe 421 at the discharge port 14, and a spiral guide channel 422 is provided inside the cooling pipe 421, and the slow cooling and solidification unit 42 is also provided with a cooling fan 423 connected to the cooling pipe 421; liquid cooling circulating water flows in the circulating water cooling pipe 411 in the inner jacket of the cooling zone 12, and the temperature drop time in the cooling zone 12 can be controlled by increasing the flow rate of the liquid cooling circulating water. After passing through the cooling zone 12, the prepared BaTiO3 particles will enter the cooling pipe 421 on the discharge port 14 for slow cooling and solidification. The spiral guide channel 422 in the cooling pipe 421 is designed to make the airflow form turbulence therein, thereby enhancing the heat transfer coefficient and the heat transfer efficiency.

[0029] According to, the collection system 5 includes a cyclone separator 51, a bag dust collector 52 and a collection fan 53; the cyclone separator 51 includes a straight section 511 and a conical section 512, the length of the conical section 512 is longer than the straight section 511, and a separation inlet 513 is provided on the side wall of the straight section 511 to communicate with the air outlet 36, a separation outlet 514 is also provided at the top of the straight section 511, and a star-shaped discharge valve 515 is also provided at the bottom of the conical section 512; an air flow plate 521 with a plurality of holes is provided inside the bag dust collector 52 box, and filter bags 522 are installed at the openings of the air flow plate 521, and a material outlet 513 is provided at the bottom of the bag dust collector 52. The bucket 523 and the dust removal inlet 524 are connected, and the dust removal inlet 524 is connected to the separation outlet 514. A dust removal outlet 525 is also provided at the top of the bag dust collector 52 and is connected to the collection fan 53; the cyclone separator 51 can separate large particles of material, and the remaining fine particles will enter the bag dust collector 52 for secondary collection. The structural design of the graded collection can greatly improve the collection accuracy. The collection fan 53 can provide a negative pressure environment for the entire collection system, so that the airflow in the high-temperature reactor 1 can flow out stably to avoid flame backflow. At the same time, the negative pressure environment provided can enable the collection system to better collect BaTiO3 spherical powder.

[0030] According to, a coating unit 54 is provided at the outlet position of the collection system 5, and a coating inlet 541, a coating area 543 and a coating outlet 545 are sequentially provided on the coating unit 54; a coating nozzle 542 is provided between the coating inlet 541 and the coating area 543, and the diameter of the coating nozzle 542 is much smaller than the inner diameter of the pipe of the coating inlet 541; the coating area 543 and the coating outlet 545 are connected through a coating throat 544, and the inner wall between the coating area 543 and the coating throat 544 is set to contract inwardly, and the inner wall of the coating throat 544 and the coating outlet 545 is set to expand outwardly; a coating material inlet pipe 546 is also provided on the side wall of the coating area 543, and the coating material inlet pipe 546 is connected to a storage tank 547 for storing the coating material through a pipeline; the coating unit 54 adopts a Venturi effect design, and the airflow with BaTiO3 spherical powder will reach the coating nozzle 541 through the coating inlet 541 When passing through the coating nozzle 542, the cross-sectional area of ​​the channel becomes smaller and the flow rate of the airflow increases. After the faster airflow passes through the coating nozzle 542 and reaches the coating area 543, the pressure in the coating area 543 will be lower than the external pressure. At this time, the storage tank 547 for storing the coating material transports KH-570 silane coupling agent vapor to the coating area 543 through the coating material inlet pipe 546. At this time, the silane coupling agent vapor and the BaTiO3 spherical powder airflow will be mixed and coated in the coating area 543 due to the pressure difference. Since the cross-sectional area of ​​the coating throat 544 is suddenly reduced, the silane coupling agent vapor and the BaTiO3 spherical powder airflow will be further intensely mixed and coated at the coating throat 544. After the coating is completed, the BaTiO3 spherical powder after surface functionalization treatment is finally discharged through the coating outlet 545. The dispersibility of the BaTiO3 spherical powder after surface functionalization treatment is greatly improved.

Claims

1. A method for producing spherical barium titanate powder, characterized in that: The following steps are involved: S1. Preparation and atomization of precursor solution: preparing barium titanate precursor solution, and then atomizing the precursor solution into micron-sized droplets through an atomizing nozzle; S2, melt crystallization, a high temperature reactor is provided with a gradient temperature rising zone, and the atomized precursor solution is sprayed into the gradient temperature rising zone of the high temperature reactor to perform flame melt crystallization; S3, gradient cooling and spherical solidification, after the crystallized barium titanate crystals enter the cooling section of the high-temperature reactor, they complete the crystal form transformation of barium titanate through rapid condensation-slow cooling solidification, while reducing lattice defects; S4, classification and collection, the barium titanate spherical powder after cooling and solidification is sequentially classified and collected by cyclone separation and bag dust removal to obtain barium titanate spherical powder with appropriate particle size; S5. Surface functionalization: The collected barium titanate spherical powder is passed through a coating unit and introduced with silane coupling agent vapor to obtain a surface coating layer, thereby improving the dispersibility of the barium titanate spherical powder.

2. The method for producing spherical barium titanate powder according to claim 1, wherein: The step S1 is to prepare the precursor solution and atomize the barium titanate precursor according to a Ba:Ti molar ratio of 1:1, which is easy to configure and includes the following steps: S11, dissolving tetrabutyl titanate in an ethanol solution with a concentration of 50%-70%, adding acetic acid, stirring evenly, and then inputting into a titanium salt storage tank, wherein the volume ratio of tetrabutyl titanate to the ethanol solution is 1:3-1:5, and the volume ratio of acetic acid to tetrabutyl titanate is 1:5-1:10; S12, adding barium nitrate to a 70%-80% ethanol solution, stirring the mixture evenly, and then inputting the mixture into a barium salt storage tank, wherein the volume ratio of the barium nitrate to the ethanol solution is 1:3-1:5; S13, transporting the solutions in the titanium salt storage tank and the barium salt storage tank to a mixing tank for uniform mixing by ultrasonic stirring, wherein the ultrasonic frequency is 40 kHz and the stirring time is 30 min; S14. Use an atomizing nozzle to atomize the precursor solution into micron-sized droplets. The atomizing gas is compressed air with a pressure of 0.3-0.5 MPa and a gas flow rate of 10-30 m³ / h.

3. The method for producing spherical barium titanate powder according to claim 1, wherein: The combustion zone of the high-temperature reactor in the melt crystallization step S2 is a gradient combustion structure, with an evaporation zone, a flame zone and a melting zone arranged in sequence along the airflow direction. The temperature of the evaporation zone is 300-500°C, the temperature of the flame zone is 500-800°C, and the temperature of the melting zone is 800-1200°C.

4. The method for producing spherical barium titanate powder according to claim 1, wherein: In the step S3 gradient cooling and spherical solidification, rapid condensation is cooling with circulating cooling water, the cooling water flow rate is 20-60 m³ / h, and the air flow temperature in the rapid condensation zone is ≤600°C; slow cooling solidification is cooling with cooling air, the cooling air flow rate is 50-150 m³ / h, and the air flow temperature in the slow cooling solidification zone is ≤200°C.

5. The method for producing spherical barium titanate powder according to claim 1, wherein: The production method is further provided with a preparation device, including a high-temperature reaction furnace (1), a precursor preparation system (2), a heating system (3), a cooling system (4) and a collection system (5); a gradient heating zone (11) and a cooling zone (12) are provided inside the high-temperature reaction furnace (1), the gradient heating zone (11) sequentially including an evaporation zone (111), a flame zone (112) and a melting zone (113); a feed port (13) is provided at the top of the high-temperature reaction furnace (1), and a discharge port (14) is provided at the bottom; the precursor preparation system (2) is communicated with the interior of the high-temperature reaction furnace (1) through the feed port (13); the heating system (3) is provided at the position of the gradient heating zone (11); the cooling system (4) is communicated with the cooling zone (12); and the interior of the high-temperature reaction furnace (1) is communicated with the collection system (5) through the discharge port (14).

6. The method for producing spherical barium titanate powder according to claim 5, characterized in that: The precursor preparation system (2) includes a titanium salt storage tank (21), a barium salt storage tank (22) and a mixing tank (23). The titanium salt storage tank (21) and the barium salt storage tank (22) are both connected to the mixing tank (23) through pipelines. An ultrasonic stirrer (24) is provided inside the mixing tank (23). A feeding high-pressure pump (25) is also provided on the mixing tank (23). The mixed raw materials are transported to an atomizing nozzle (26) through the feeding high-pressure pump (25) and then sprayed into the high-temperature reaction furnace (1). The atomizing nozzle (26) is provided on the feed port (13).

7. The method for producing spherical barium titanate powder according to claim 5, characterized in that: The heating system (3) comprises an evaporation heating device (31), a combustion heating device (32) and a melting heating device (33), wherein the evaporation heating device (31) is arranged at the evaporation zone (111), the combustion heating device (32) is arranged at the flame zone (112), and the melting heating device (33) is arranged at the melting zone (113); the evaporation heating device (31) is heated by an electric heating wire, and a ring-shaped electric heating wire is installed in the evaporation zone (111). ) inner wall; the combustion heating device (32) is for heating and melting fuel by combustion, and includes a fuel tank (321) and an oxygen tank (322); a combustion nozzle (323) is provided on the flame zone (112), and the fuel tank (321) and the oxygen tank (322) are both connected to the combustion nozzle (323); the melting heating device (33) is for heating silicon molybdenum rods, and the melting heating device (33) is provided with a plurality of groups of silicon molybdenum rods circumferentially arranged on the inner wall of the melting zone (113).

8. The method for producing spherical barium titanate powder according to claim 5, characterized in that: The cooling system (4) includes a rapid condensation unit (41) and a slow cooling and solidification unit (42); the inner jacket of the cooling zone (12) of the high-temperature reaction furnace (1) is provided with a circulating water cooling pipe (411), and the circulating water cooling pipe (411) is connected to the circulating water cooling device (412) of the rapid condensation unit (41); the slow cooling and solidification unit (42) is arranged at the discharge port (14), and the slow cooling and solidification unit (42) is provided with a cooling pipe (421) at the discharge port (14), and a spiral guide channel (422) is provided inside the cooling pipe (421); the slow cooling and solidification unit (42) is also provided with a cooling fan (423) connected to the cooling pipe (421).

9. The method for producing spherical barium titanate powder according to claim 5, characterized in that: The collection system (5) includes a cyclone separator (51), a bag dust collector (52) and a collection fan (53); the cyclone separator (51) includes a straight section (511) and a conical section (512), the conical section (512) is longer than the straight section (511), a separation inlet (513) is provided on the side wall of the straight section (511) and is connected to the air outlet (36), a separation outlet (514) is also provided at the top of the straight section (511), and a separation outlet (514) is provided at the bottom of the conical section (512). A star-shaped discharge valve (515) is also provided; an airflow plate (521) with a plurality of holes is provided inside the bag dust collector (52) box, and filter bags (522) are installed at the openings of the airflow plate (521); a hopper (523) and a dust removal inlet (524) are provided at the bottom of the bag dust collector (52); the dust removal inlet (524) is communicated with the separation outlet (514); and a dust removal outlet (525) is also provided at the top of the bag dust collector (52) and is communicated with the collection fan (53).

10. The method for producing spherical barium titanate powder according to claim 5, characterized in that: A coating unit (54) is provided at the outlet of the collection system (5), and a coating inlet (541), a coating area (543) and a coating outlet (545) are sequentially provided on the coating unit (54); a coating nozzle (542) is provided between the coating inlet (541) and the coating area (543), and the diameter of the coating nozzle (542) is much smaller than the inner diameter of the pipe of the coating inlet (541); the coating area (543) and the coating outlet (545) are connected. The coating outlets (545) are connected via a coating throat (544); the inner wall between the coating area (543) and the coating throat (544) is configured to contract inwardly, while the inner wall between the coating throat (544) and the coating outlet (545) is configured to expand outwardly; a coating material inlet pipe (546) is further provided on the side wall of the coating area (543); the coating material inlet pipe (546) is connected to a storage tank (547) for storing the coating material through a pipeline.

Images