A granulating apparatus, a method of producing tantalum powder using the same, and tantalum powder produced thereby

Abstract

The application discloses a granulating device, a method for preparing tantalum powder by using the device and tantalum powder prepared by the method. The granulating device comprises a powder agglomerating bin, three variable frequency motors are mounted around the bin to realize multi-dimensional vibration and rotary rolling, a universal adjusting atomizing spray head is arranged above the bin, and a lifting and speed-adjustable stirring paddle is arranged on the bin. The preparation method comprises the following steps: putting reduced tantalum powder into the bin, agglomerating under the conditions of stirring and atomizing water spraying, then performing multi-dimensional vibration and rotary shaping by using the variable frequency motor, and finally obtaining spherical agglomerated tantalum powder through drying, vacuum heat treatment, oxygen reduction treatment and acid pickling purification. The application realizes the automation and standardization of tantalum powder granulation, the prepared tantalum powder has high purity, good physical performance, controllable bulk density and particle size, excellent sphericity and flowability, effectively solves the problems of poor flowability of high specific capacity tantalum powder caused by small particle size and cracking of small shell number capacitor tantalum anode block caused by uncontrollable particle size after granulation.

Description

Technical Field

[0001] This invention relates to the field of metallurgical and electronic powder material preparation technology, specifically to a multi-dimensional vibration agglomeration granulation device, a method for preparing near-spherical agglomerated tantalum powder using this device, and the near-spherical agglomerated tantalum powder prepared by this method. This granulation device can be used for agglomeration granulation of valve metal powders such as tantalum powder and niobium powder, and is particularly suitable for improving the physical and processing properties of high-specific-capacitance tantalum powder for capacitors. Background Technology

[0002] Tantalum is widely used in the manufacture of tantalum capacitors due to its excellent electrical properties. With the development of the electronics industry, electronic products are trending towards miniaturization, requiring electronic components to be both high-performance and compact. For sintered tantalum capacitors, high specific capacitance per unit volume and specific capacitance per unit weight are required, necessitating the use of tantalum powder with a higher specific surface area to fabricate the anode of electrolytic capacitors.

[0003] As the specific surface area of ​​tantalum powder increases, its particle size becomes finer, and its flowability deteriorates. This affects the processability of tantalum anode fabrication, leading to problems such as large weight deviations, chipped edges, and uneven compaction in the processed tantalum capacitor anodes. This further results in a series of electrical performance issues, including large capacitance deviations, high leakage current, high ESR, and poor reliability. To address the tantalum powder flowability problem, it is typically necessary to agglomerate and granulate the tantalum powder, followed by vacuum high-temperature sintering.

[0004] To prepare tantalum powder with good physical properties, various tantalum powder manufacturers have developed a variety of agglomerated tantalum powder preparation equipment. Patents CN106794520A and CN87101648A disclose a spray granulation device, but this method requires the addition of a binder, which easily leads to increased product impurities. When the produced tantalum powder is used in capacitor manufacturing, it may cause increased leakage. Japanese Patent Publication 2009-102680A discloses a granulation and agglomeration method and apparatus, but its second stirring speed is as high as 3000-6000 rpm, which easily reduces the porosity between particles and makes it difficult to obtain well-dispersed particles before heat treatment, affecting powder flowability. Chinese Patent CN1073480C discloses a disc granulator that requires crushing after granulation, crushing spherical particles into polygonal particles, increasing the proportion of -400 mesh fine powder, and worsening powder flowability. Patent CN102806345B discloses a rotary sieve method that produces agglomerated particles with low agglomeration strength and poor formability. Existing methods, such as hydrogenating metal ingots to form powder followed by ball milling and airflow shaping, produce tantalum powder with low porosity, making them unsuitable for producing high-specific-volume tantalum powder. While existing plasma atomization methods result in low impurities, the particles have low porosity after high-temperature melting, and the production equipment is expensive.

[0005] In summary, existing technologies suffer from numerous drawbacks, including unfavorable conditions for producing high-specific-capacity tantalum powder, high impurity content, small specific surface area, low porosity, expensive equipment, and complex production processes. Therefore, it is necessary to provide a granulation device and preparation method capable of achieving tantalum powder agglomeration, particle size control, and near-spherical shaping without introducing a binder. Summary of the Invention

[0006] The purpose of this invention is to provide a granulation device, a method for preparing tantalum powder using the device, and the tantalum powder prepared therefrom, in order to solve the problems of uncontrollable particle size, expensive equipment, and poor capacitor processing performance caused by poor flowability of tantalum powder in the existing high specific capacitance tantalum powder granulation process.

[0007] To achieve the above objectives, the present invention provides a granulation apparatus, comprising: A powder agglomeration silo, wherein the powder agglomeration silo has a cylindrical structure and a discharge port is provided at the bottom; Multiple variable frequency motors are installed around the powder agglomeration hopper to drive the powder in the powder agglomeration hopper to vibrate up and down and rotate clockwise or counterclockwise. Atomizing spray head is positioned above the powder agglomeration hopper; and A stirring paddle is positioned above the powder agglomeration hopper and can be raised and lowered to extend into the powder agglomeration hopper. The stirring speed of the stirring paddle is adjustable.

[0008] Furthermore, the multiple variable frequency motors include a first variable frequency motor and a third variable frequency motor respectively installed on both sides of the powder agglomeration silo, and a second variable frequency motor installed at the bottom of the powder agglomeration silo; the first variable frequency motor, the second variable frequency motor and the third variable frequency motor are each equipped with a timing control device.

[0009] Furthermore, the powder agglomeration hopper is a high-strength stainless steel cylinder lined with tantalum; the stirring paddle is a high-strength stainless steel stirring paddle with tantalum lining on the surface; the atomizing spray head is independently fixed and does not move synchronously with the powder agglomeration hopper, and has a universal adjustment function; the atomizing spray head is connected to a solenoid valve and is equipped with a timing control device.

[0010] The present invention also provides a method for preparing spheroidized agglomerated tantalum powder using the above-mentioned granulation equipment, comprising the following steps: 1) Add the reduced tantalum powder to the powder agglomeration hopper; 2) Start the mixing paddle, add water through the atomizing spray head, and stir for 5-60 minutes. Then stop stirring and lift the mixing paddle. Start multiple variable frequency motors to rotate and vibrate the agglomerated powder in the hopper to shape it. 3) Dry the powder treated in step 2) at 110-150℃ for 8-20 hours; 4) The tantalum powder dried in step 3) is subjected to vacuum heat treatment in a vacuum heat treatment furnace. The heat treatment conditions are: holding at 950-1550℃ for 0.5-3 hours. 5) The tantalum powder after heat treatment and passivation in step 4) is subjected to deoxygenation treatment; 6) After the oxygen reduction treatment in step 5), the material is crushed and / or sieved according to the degree of agglomeration, and then acid washed, water washed, dried and sieved in sequence to finally obtain spherical agglomerated tantalum powder.

[0011] Further, in step 1), the reduced tantalum powder is obtained by reducing potassium fluorotantalate with purified sodium, followed by a wet purification process of water washing, acid washing, and filtration.

[0012] Further, in step 2), the rate at which water is added through the atomizing spray head is 0.2-0.8 L / min, the amount of water added is 15-40% of the mass of the reduced tantalum powder, and the water added is deionized water.

[0013] Furthermore, in step 5), the specific conditions for deoxygenation treatment are as follows: the amount of magnesium added is 0.5-5%, the temperature is raised to 700℃-960℃ and held for 1-3 hours, then the magnesium is removed by vacuuming for 1-4 hours, and the furnace is removed after passivation.

[0014] Furthermore, in step 6), the pickling process is carried out using HNO3 acid solution with a mass concentration of 5-20%, and the pickling time is 0.5-2 hours.

[0015] This invention also provides a quasi-spherical agglomerated tantalum powder, prepared by the above method. The quasi-spherical agglomerated tantalum powder can be used to prepare tantalum capacitor anodes.

[0016] The beneficial effects of this invention are as follows: 1) The granulation equipment of the present invention can realize stirring and multi-dimensional vibration and rotation, effectively adjust the loose density and particle size of the product, and agglomerate and shape tantalum powder, realize the automation and standardization of the granulation process, and is simple to operate and has low manufacturing cost.

[0017] 2) For reduced tantalum powder obtained by conventional wet purification and drying, no additional binder premixing, briquetting or melt pretreatment is required. By controlling the amount of water added, stirring intensity and vibration rotation time, spherical agglomerated tantalum powder with different loose density and particle size can be obtained.

[0018] 3) The granulation process does not require the addition of organic binders, which can reduce the introduction of impurities; at the same time, the powder agglomeration hopper and the agitator adopt a tantalum lining structure, which can reduce the contamination of tantalum powder by equipment contact parts, resulting in high purity of tantalum powder and low content of metal impurities and carbon.

[0019] 4) The prepared agglomerated tantalum powder has good sphericity and excellent flowability, which can improve the poor flowability caused by small particle size of high specific capacitance tantalum powder and the processing performance problems such as cracking of capacitor anode blocks caused by uncontrollable particle size. Attached Figure Description

[0020] Figure 1 SEM image of the morphology of the clustered spherical tantalum particles prepared in Example 1; Figure 2 SEM image of the morphology of the clustered spherical tantalum particles prepared in Example 2; Figure 3 This is a schematic diagram of the multidimensional vibration agglomeration granulator of the present invention.

[0021] The corresponding labels in the figure are as follows: 1 is the atomizing spray head, 2 is the stirring paddle, 3 is the powder agglomeration hopper, 4 is the first variable frequency motor, 5 is the second variable frequency motor, and 6 is the third variable frequency motor. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Equivalent substitutions or adaptive adjustments made by those skilled in the art to the equipment structure, process parameters, or operating methods without departing from the concept of the present invention should all fall within the scope of protection of the present invention.

[0023] Combination Figure 3 As shown, the multi-dimensional vibration agglomeration granulator of the present invention includes a powder agglomeration hopper 3, an atomizing spray head 1, a stirring paddle 2, a first variable frequency motor 4, a second variable frequency motor 5, and a third variable frequency motor 6.

[0024] The powder agglomeration hopper 3 has a cylindrical structure, preferably a high-strength stainless steel cylinder lined with tantalum, with a discharge port at the bottom. By installing a tantalum liner inside the cylinder, the risk of contamination of the tantalum powder by the stainless steel matrix during the powder agglomeration process can be reduced, which is beneficial for obtaining tantalum powder products with low impurity content.

[0025] The stirring paddle 2 is positioned above the powder agglomeration hopper 3 and can be raised and lowered to extend into the powder agglomeration hopper 3. The stirring paddle 2 is preferably a high-strength stainless steel stirring paddle with a tantalum-lined surface. The stirring speed of the stirring paddle 2 is adjustable and is used to stir the reduced tantalum powder during the atomization and water addition process, so that the water is evenly dispersed in the powder and promotes the initial agglomeration of the powder.

[0026] The atomizing spray head 1 is positioned above the powder agglomeration hopper 3 and is independently fixed, not moving synchronously with the hopper. The atomizing spray head 1 has a omnidirectional adjustment function, allowing the spray direction to be adjusted according to the powder accumulation state and stirring area within the hopper 3. The atomizing spray head 1 is connected to the water supply pipeline via a solenoid valve, and the spray start / stop and spray duration are controlled by a timer control device, thereby achieving stable control of the water addition rate and volume.

[0027] The first variable frequency motor 4 and the third variable frequency motor 6 are respectively installed on both sides of the powder agglomeration hopper 3, and the second variable frequency motor 5 is installed at the bottom of the powder agglomeration hopper 3. The first variable frequency motor 4, the second variable frequency motor 5, and the third variable frequency motor 6 are respectively connected to a timing control device to control the duration and operating frequency of vertical vibration, clockwise rolling, or counterclockwise rolling. Through the coordinated action of multiple variable frequency motors, the powder in the powder agglomeration hopper 3 can be made to vibrate vertically and rotate clockwise or counterclockwise, thereby further shaping the agglomerated powder formed by adding water and stirring, so that it gradually forms spherical agglomerated particles.

[0028] In the preparation method of this invention, reduced tantalum powder is first added to the powder agglomeration silo 3, the stirring paddle 2 is started, and deionized water is added through the atomizing spray head 1, so that the reduced tantalum powder absorbs water and agglomerates under the stirring action; then the stirring is stopped and the stirring paddle 2 is lifted, and multiple variable frequency motors are started, so that the agglomerated powder in the silo is shaped under the action of up and down vibration and rotation; after drying, vacuum heat treatment, deoxygenation treatment, acid washing, water washing, drying and sieving, spherical agglomerated tantalum powder is obtained.

[0029] The obtained spherical agglomerated tantalum powder exhibits a rounded, agglomerated particle morphology under SEM observation, demonstrating good flowability and high bulk density. Depending on the specific process parameters, the flowability of the obtained spherical agglomerated tantalum powder can range from 8.0 to 11.2 s / 50 g, and the bulk density can range from 1.61 to 2.10 g / cm³. 3 .

[0030] Example 1

[0031] Potassium fluorotantalate was reduced with sodium at 880℃. The resulting tantalum powder and byproducts were then crushed into small lumps approximately 1 cm in size. After washing with pure water for 24 hours, the mixture was acid-washed with a mixture of 2.0% HF and 15% HNO3 for 4 hours. Following rinsing with pure water and vacuum filtration, the mixture was vacuum-dried at 120℃ for 14 hours to obtain a product with a specific surface area of ​​2.1 m². 2 / g, loose bulk density 0.6g / cm³ 3 Tantalum raw powder.

[0032] The raw powder was placed in the powder agglomeration hopper 3 of the multi-dimensional vibratory agglomeration granulator, and the stirring paddle 2 was started at a speed of 20 rpm. Deionized water was added through the atomizing spray head 1 at a rate of 0.4 L / min, with the amount of deionized water being 20% ​​of the mass of the raw powder. After stirring for 30 minutes, the machine was stopped and the stirring paddle 2 was removed.

[0033] Start the first variable frequency motor 4, the second variable frequency motor 5 and the third variable frequency motor 6 to make the tantalum powder vibrate up and down and rotate and roll in the powder agglomeration hopper 3 for 20 minutes to obtain spherical agglomerated tantalum powder.

[0034] The powder was dried at 120°C for 14 hours; then placed in a tantalum crucible and put into a vacuum heat treatment furnace, held at 950°C for 1.5 hours, then held at 1150°C for 0.5 hours, then cooled to 35°C, passivated and removed from the furnace and passed through a 50-mesh sieve.

[0035] The material was then subjected to deoxygenation treatment: 3.5% magnesium was added, the furnace was charged with argon gas, and the temperature was raised to 800℃ and held for 2 hours for reduction. Afterwards, the magnesium was removed by evacuation for 2 hours, and the material was passivated before being removed from the furnace. After deoxygenation treatment and passivation, the material was lightly crushed and sieved, then acid-washed with 15% HNO3 for 40 minutes, washed with water and filtered, vacuum-dried at 80℃ for 15 hours, and passed through a 50-mesh sieve to obtain sample 1. Its electrical and physical properties are shown in Tables 1 and 2, and its morphology is shown in... Figure 1 .

[0036] Example 2

[0037] The initial preparation of the original powder was the same as in Example 1.

[0038] The raw powder was placed in the powder agglomeration hopper 3 of the multi-dimensional vibratory agglomeration granulator, and the stirring paddle 2 was started at a speed of 20 rpm. Deionized water was added through the atomizing spray head 1 at a rate of 0.4 L / min, with the amount of deionized water being 20% ​​of the mass of the raw powder. After stirring for 40 minutes, the machine was stopped and the stirring paddle 2 was removed.

[0039] Start the first variable frequency motor 4, the second variable frequency motor 5 and the third variable frequency motor 6 to make the tantalum powder vibrate up and down and rotate in the powder agglomeration hopper 3 for 40 minutes to obtain spherical agglomerated tantalum powder.

[0040] Subsequent drying, heat treatment, deoxygenation treatment, and pickling-drying processes were the same as in Example 1. Specifically, the heat treatment conditions were 950℃ for 1.5 hours, followed by 1150℃ for 0.5 hours; the deoxygenation treatment conditions were 3.5% magnesium addition and 800℃ for 2 hours. After deoxygenation treatment and passivation, the material was lightly crushed and sieved, then pickled, washed, filtered, dried, and sieved again to obtain Sample 2. Its electrical and physical properties are shown in Tables 1 and 2, and its morphology is shown in... Figure 2 .

[0041] Table 1: Chemical impurities and physical properties of the samples Sample 1 11.2 1.61 4400 12 4 4 3 2 Sample 2 8.0 2.10 3970 11 4 3 3 3 Table 2: Electrical properties of the samples Sample 1 34 101799 20 1250 / 20 Sample 2 32.7 100820 20 1250 / 20 As can be seen from Tables 1 and 2, Sample 1 and Sample 2 prepared using the multidimensional vibration agglomeration granulation equipment and method of this invention both exhibit good flowability and high bulk density, with low metal impurity content and good electrical properties. Combined with... Figure 1 and Figure 2 It is evident that the obtained tantalum powder particles exhibit a near-spherical agglomerate morphology, indicating that the present invention, through a combination of stirring and water addition with multidimensional vibration and rotational shaping, can effectively improve the morphology and flowability of tantalum powder, making it suitable for use in the preparation of tantalum capacitor anodes.

Claims

1. A granulation device, characterized in that, include: Powder agglomeration silo (3), wherein the powder agglomeration silo (3) is a cylindrical structure and has a discharge port at the bottom; Multiple variable frequency motors are installed around the powder agglomeration silo (3) to drive the powder in the powder agglomeration silo (3) to vibrate up and down and rotate clockwise or counterclockwise. Atomizing spray head (1) is positioned above the powder agglomeration silo (3); as well as A stirring paddle (2) is positioned above the powder agglomeration hopper (3) and can be raised and lowered and extended into the powder agglomeration hopper (3). The stirring speed of the stirring paddle (2) is adjustable.

2. The granulation equipment according to claim 1, characterized in that: The multiple variable frequency motors include a first variable frequency motor (4) and a third variable frequency motor (6) installed on both sides of the powder agglomeration silo (3), and a second variable frequency motor (5) installed at the bottom of the powder agglomeration silo (3); the first variable frequency motor (4), the second variable frequency motor (5) and the third variable frequency motor (6) are respectively equipped with timing control devices.

3. The granulation equipment according to claim 1, characterized in that: The powder agglomeration hopper (3) is a high-strength stainless steel cylinder lined with tantalum; the stirring paddle (2) is a high-strength stainless steel stirring paddle with tantalum lining on the surface; the atomizing spray head (1) is independently fixed and does not move synchronously with the powder agglomeration hopper (3), and has a universal adjustment function; the atomizing spray head (1) is connected to a solenoid valve and is equipped with a timing control device.

4. A method for preparing spheroidized tantalum powder using the granulation equipment according to any one of claims 1-3, characterized in that, The steps are as follows: 1) Add the reduced tantalum powder to the powder agglomeration silo (3); 2) Start the stirring paddle (2), add water through the atomizing spray head (1), stir for 5-60 minutes, then stop stirring and lift the stirring paddle (2); start multiple variable frequency motors to rotate and vibrate the agglomerated powder in the silo to shape it. 3) Dry the powder treated in step 2) at 110-150℃ for 8-20 hours; 4) The tantalum powder dried in step 3) is subjected to vacuum heat treatment in a vacuum heat treatment furnace. The heat treatment conditions are: holding at 950-1550℃ for 0.5-3 hours. 5) The tantalum powder after heat treatment and passivation in step 4) is subjected to deoxygenation treatment; 6) After the oxygen reduction treatment in step 5), the material is crushed and / or sieved according to the degree of agglomeration, and then acid washed, water washed, dried and sieved in sequence to finally obtain spherical agglomerated tantalum powder.

5. The method according to claim 4, characterized in that: In step 1), the reduced tantalum powder is obtained by reducing potassium fluorotantalate with purified sodium, followed by a wet purification process of water washing, acid washing, and filtration.

6. The method according to claim 4, characterized in that: In step 2), the water is added at a rate of 0.2-0.8 L / min through the atomizing spray head (1), and the amount of water added is 15-40% of the mass of the reduced tantalum powder. The water added is deionized water.

7. The method according to claim 4, characterized in that: In step 5), the specific conditions for deoxygenation treatment are as follows: the amount of magnesium added is 0.5-5%, the temperature is raised to 700℃-960℃ and held for 1-3 hours, then the magnesium is removed by vacuuming for 1-4 hours, and the furnace is removed after passivation.

8. The method according to claim 4, characterized in that: In step 6), the pickling process is carried out using HNO3 acid solution with a mass concentration of 5-20%, and the pickling time is 0.5-2 hours.

9. A quasi-spherical agglomerated tantalum powder, characterized in that: Prepared by the method described in any one of claims 4-8.

10. The quasi-spherical agglomerated tantalum powder according to claim 9, characterized in that: The spheroidized tantalum powder is used to prepare tantalum capacitor anodes.

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