Device and method for preparing tantalum powder by reducing gaseous magnesium

Abstract

The invention discloses a device and a method for preparing tantalum powder by reducing gaseous magnesium, and solves the problems of high oxygen content, poor particle uniformity, incomplete reaction and the like in the prior art. The device adopts a vertical multi-layer reaction furnace structure, and realizes efficient reduction of tantalum oxide through heating of a resistance wire and reaction with gaseous magnesium. The method comprises gaseous magnesium reduction and product post-treatment. The oxygen content of the tantalum powder prepared through the method is controlled to be 3000-6000 ppm, the specific volume reaches 80000-100000 mu F.V / g, the apparent density ranges from 1.5 g / cm < 3 > to 1.8 g / cm < 3 >, particle size distribution is uniform, and the method is suitable for large-scale production of electronic-grade tantalum powder.

Description

Technical Field

[0001] The present invention relates to the technical field of rare metal powder metallurgy, and in particular to a device and method for preparing high-purity tantalum powder by vertical multi-layer gaseous magnesium reduction, which is suitable for large-scale production of tantalum powder for electronic components. Background Art

[0002] In the electronics industry, tantalum capacitors are widely used in key areas such as aerospace, new energy vehicles, and 5G communications due to their high specific capacitance, long life, and high-temperature resistance. Tantalum powder, as the core raw material for tantalum electrolytic capacitors, has a quality that directly affects the performance and reliability of the capacitors. Specifically, excessive oxygen content in tantalum powder will significantly increase the leakage current of the capacitor, reducing its stability and service life; poor particle uniformity will lead to uneven electric field distribution within the capacitor, easily causing local overheating or even breakdown; and substandard bulk density will affect the filling efficiency and overall performance of the capacitor.

[0003] Currently, the traditional magnesium thermal reduction process for tantalum powder production faces severe technical bottlenecks. This process uses solid magnesium as a reducing agent. During the reduction of tantalum oxide, contact between the solid magnesium and the tantalum oxide occurs only within a limited surface area, making it difficult to achieve sufficient and uniform mixing. Consequently, a large amount of tantalum oxide is unable to fully participate in the reaction. Due to this incomplete and uneven reaction, the oxygen content in the tantalum powder is difficult to effectively control, resulting in wide fluctuations in oxygen content, further impacting the quality and subsequent applications of the tantalum powder. Summary of the Invention

[0004] In view of this, in one aspect, some embodiments disclose an apparatus for preparing tantalum powder by reducing gaseous magnesium, comprising:

[0005] Reaction vessel: used to place raw materials magnesium block and tantalum oxide;

[0006] The reaction vessel comprises:

[0007] A reaction tray is provided inside the furnace body and is used to place tantalum oxide;

[0008] The resistance wire is arranged around the outside of the furnace body to form a uniform heating area;

[0009] Magnesium source supply system: used to vaporize magnesium by heating to form a gaseous magnesium source;

[0010] The magnesium source supply system comprises:

[0011] Magnesium block placement area: located at the bottom of the furnace, used to evenly place magnesium blocks;

[0012] Water-cooled insulation cover: installed at the feed inlet at the top of the furnace body to prevent the cover from overheating;

[0013] Gas path system: set at the bottom of the furnace body, used to introduce high-purity argon as protective gas;

[0014] The temperature sensor is installed in the electric heating pit furnace to monitor the temperature changes during the reaction.

[0015] Some embodiments disclose a device for preparing tantalum powder by reducing gaseous magnesium. The reaction vessel is a cylindrical stainless steel furnace body, and the inner wall is lined with alumina fiber felt, a high-temperature resistant heat-insulating material.

[0016] Some embodiments disclose a device for preparing tantalum powder by reducing gaseous magnesium. The reaction tower trays have multiple layers and are made of high-purity tantalum sheets, all of which are horizontally placed in the furnace.

[0017] Some embodiments disclose a device for preparing tantalum powder by reducing gaseous magnesium, wherein the resistance wire power is 5-8kW and the maximum temperature resistance is 1200-1400°C.

[0018] Some embodiments disclose a device for preparing tantalum powder by reducing gaseous magnesium, wherein the reaction tower has 3-5 layers of reaction trays.

[0019] Some embodiments disclose a device for preparing tantalum powder by reducing gaseous magnesium, wherein the magnesium block placement area is a cylindrical container with a built-in porous partition with a pore size of 4-6 mm.

[0020] On the other hand, some embodiments disclose a method for preparing tantalum powder by reducing gaseous magnesium, comprising: a reduction reaction:

[0021] Evenly spread tantalum oxide on the upper tray, place magnesium blocks at the bottom of the furnace, introduce high-purity argon gas to replace the air in the furnace 4-8 times, heat to vaporize magnesium, and fully react at 900-1200℃;

[0022] Post-processing:

[0023] The reaction product is cooled in a water cooling chamber and then sequentially subjected to water washing, acid washing and vacuum drying.

[0024] Some embodiments disclose a method for preparing tantalum powder by reducing gaseous magnesium, wherein the tantalum oxide powder is laid to a thickness of 2-4 mm, and the molar ratio of magnesium block to tantalum oxide is (5-8):1.

[0025] Some embodiments disclose a method for preparing tantalum powder by reducing gaseous magnesium, wherein the argon flow rate is 200-300 mL / min and the heating rate is 5-10° C. / min.

[0026] Some embodiments disclose a method for preparing tantalum powder by reducing gaseous magnesium. The reduction reaction comprises heating from room temperature to 900-950°C at a heating rate of 5-8°C / min while controlling the pressure at 0.10-0.12 MPa, and maintaining the temperature under these conditions for 4-6 hours. After the temperature is maintained, the pressure in the furnace is adjusted to 0.03-0.05 Pa, and the temperature is increased at a heating rate of 8-10°C / min to 1095-1200°C. The temperature is maintained for 0.5-1 hour, and then the power is turned off to cool the temperature.

[0027] Some embodiments disclose a method for preparing tantalum powder by gaseous magnesium reduction, wherein post-treatment includes: washing with hot pure water at 60-80°C until the conductivity is ≤50μS / cm, pickling with 10-20% hydrochloric acid at 55-65°C with stirring for 4-6 hours, washing with water until neutral, and finally drying at 75-85°C and a vacuum degree of -0.1MPa to -0.09MPa for 8-10 hours.

[0028] The method for preparing tantalum powder by reducing gaseous magnesium disclosed in the embodiment of the present invention utilizes a multi-layer tray structure to transmit gaseous magnesium, thereby avoiding material accumulation. The gaseous magnesium diffuses upward from the bottom of the furnace and contacts tantalum oxide fully, thus greatly improving uniformity. At the same time, combined with the regulation of sodium chloride flux, NaCl melts at high temperature to form an ion melt, promoting the oxidation of O in Ta2O5. 2 - Migrate to the melt, the reaction formula is: Ta2O5+5Mg(g)→2Ta+5MgO, MgO and NaCl form MgO·NaCl solid solution, reducing the residual oxygen to obtain tantalum powder with oxygen content controlled at 3000-6000ppm, specific capacitance of 80000-100000μF·V / g, and bulk density of 1.5-1.8g / cm 3 , stable performance and uniform size distribution. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the structure of the device of the present invention.

[0030] Figure 2 This is the SEM image of the obtained tantalum powder.

[0031] Reference numerals

[0032] 1 Water-cooled insulation cover 2 Temperature sensor

[0033] 3 Reaction tray 4 Resistance wire

[0034] 5 Magnesium block placement area 6 Gas path

[0035] 7 valve 8 electric heating pit furnace

[0036] 9 Bracket 10 Tray

[0037] 11 Gas flow meter 12 Furnace body

[0038] 13 Furnace DETAILED DESCRIPTION

[0039] In order to fully and deeply present the technical solution architecture of the present invention and its effectiveness in practical applications, the present invention will now be analyzed in detail through specific implementation cases. It should be made clear that the following implementation cases are only used to illustrate the implementation methods of the technical solutions of the present invention, and the application scenarios and specific implementation methods involved do not constitute a limitation on the scope of protection of the claims of the present invention. In other words, any technical improvements, optimizations or adjustments based on the contents disclosed in the embodiments of the present invention should be included in the scope of protection of the rights of the present invention.

[0040] Example 1

[0041] The furnace body is constructed of high-temperature stainless steel and equipped with a temperature-controlled heating system, gas inlet and outlet piping, and a pressure monitoring device. Four high-purity tantalum trays are installed from bottom to top within the furnace, each tray's diameter matching the furnace's internal diameter. 1.38 kg of 99.9% pure magnesium blocks are placed on a porous baffle at the furnace bottom, and 5 kg of tantalum oxide raw material, 2 mm thick, is evenly distributed on the upper tray.

[0042] High-purity argon is introduced through the gas inlet pipe at a flow rate of 250mL / min. Each time the air in the furnace is replaced, after the pressure in the furnace reaches a slightly positive pressure, the exhaust valve is opened and the gas is slowly discharged. This process is repeated 5 times to ensure that the air in the furnace is fully replaced. After the replacement is completed, the heating system is started and the temperature is increased to 950℃ at a rate of 8℃ / min. At the same time, the pressure is controlled at 0.10-0.12MPa and kept at this temperature for 6 hours. After the insulation is completed, the pressure in the furnace is adjusted to 0.04Pa, and the temperature is increased to 1200℃ at a heating rate of 8℃ / min. After keeping the temperature for 0.5h, the power is turned off to cool down.

[0043] After the reaction is completed, the water cooling system is immediately started to quickly reduce the furnace temperature to room temperature. The product is removed and first washed with 80°C hot pure water. Stir continuously during the washing process and repeat the washing operation until the conductivity of the washing liquid is ≤50μS / cm. After the water washing is completed, the product is transferred to a corrosion-resistant container, 12% hydrochloric acid solution is added, and pickling is carried out at 60°C with stirring at a speed of 100-200r / min for 4-6 hours. After the pickling is completed, the product is rinsed with deionized water until neutral, and then placed in a vacuum drying oven and vacuum dried at 80°C and -0.09MPa for 8-10 hours.

[0044] The oxygen content of the obtained tantalum powder was determined to be 5800 ppm by inert gas fusion-infrared absorption method. The specific capacitance of the tantalum powder was determined to be 82000 μF·V / g according to GB / T5162-2006 standard. The bulk density was determined to be 1.52 g / cm by the Scott volumetric method according to GB / T1479.1-2011 standard. 3 .

[0045] Example 2

[0046] A cylindrical furnace body made of high-temperature resistant stainless steel is selected, which is equipped with a temperature-controlled heating system, gas inlet and outlet pipes, and a pressure monitoring device. Four layers of high-purity tantalum plate trays are installed in the furnace body from bottom to top, and the diameter of each layer of tray is adapted to the inner diameter of the furnace body. The tray parameters are the same as in Example 1. 1.38 kg of magnesium blocks with a purity of 99.9% are placed on the porous partition at the bottom of the furnace, and a tantalum oxide raw material with a thickness of 2 mm and a mass of 5 kg is laid on the upper tray. At the same time, 50 g of sodium chloride with a purity of ≥99.5% is weighed, and the sodium chloride and tantalum oxide are mixed in a mixer at a speed of 70-80 r / min for 30-60 minutes. After ensuring uniform mixing, they are laid on the tray.

[0047] High-purity argon was introduced at a flow rate of 250 mL / min, and the air in the furnace was replaced 5 times using the same gas replacement method as in Example 1. After the replacement was completed, the mixture was heated from room temperature to 950°C at a heating rate of 8°C / min, while the pressure was controlled at 0.10-0.12 MPa, and kept warm under this condition for 6 hours. After the insulation was completed, the pressure in the furnace was adjusted to 0.04 Pa, and the mixture was heated to 1200°C at a heating rate of 8°C / min and kept warm for 0.5 hours, and then the power was turned off to cool the mixture. After the reaction was completed and water-cooled, the product was washed with water, pickled, and dried in the same manner as in Example 1.

[0048] The oxygen content of the obtained tantalum powder was 4500ppm, the specific capacitance was 89000μF·V / g, and the apparent density was 1.68g / cm 3 , the detection method is the same as in Example 1.

[0049] Example 3

[0050] A cylindrical furnace body with the same specifications and materials as in Example 1 was selected, and four high-purity tantalum trays were installed within the furnace. A porous partition at the bottom of the furnace contained 1.38 kg of 99.9% pure magnesium blocks. A 2 mm thick, 5 kg supply of tantalum pentoxide was placed on the upper tray. 50 g of potassium chloride with a purity of ≥99.0% was weighed and mixed with tantalum oxide in a mixer at 60-80 rpm for 40-60 minutes. After mixing thoroughly, the mixture was applied to the trays.

[0051] High-purity argon was introduced at a flow rate of 50 mL / min to replace the air in the furnace five times. After the replacement was completed, the furnace was heated from room temperature to 950°C at a heating rate of 8°C / min while controlling the pressure at 0.10-0.12 MPa. The temperature was then maintained under these conditions for 6 hours. After the temperature was maintained, the pressure in the furnace was adjusted to 0.04 Pa and the temperature was increased to 1200°C at a heating rate of 8°C / min. The temperature was then maintained for 0.5 hours before the power was turned off to cool the furnace.

[0052] After the reaction is completed and the product is cooled with water, the steps of washing with water, acid washing and drying the product are the same as those in Example 1. Product performance testing

[0053] The oxygen content of the obtained tantalum powder was 4900ppm, the specific capacitance was 85000μF·V / g, and the apparent density was 1.60g / cm 3 , detection is the same as in Example 1.

[0054] Comparative description of the embodiments:

[0055] Sodium chloride promotes the migration of oxygen ions by forming a low-melting-point eutectic phase (NaCl-Ta2O5), which has the best effect in reducing oxygen content. Potassium chloride has a larger cation radius and weaker binding ability with oxygen ions than sodium ions, so its deoxygenation efficiency is lower.

[0056] The following table shows the oxygen content, specific volume, and bulk density of different examples.

[0057]

Claims

1. A device for preparing tantalum powder by reducing gaseous magnesium, characterized in that: include: Reaction vessel: used to place raw materials magnesium block and tantalum oxide; The reaction vessel comprises: A reaction tray is provided inside the furnace body and is used to place tantalum oxide; The resistance wire is arranged around the outside of the furnace body to form a uniform heating area; Magnesium source supply system: used to vaporize magnesium by heating to form a gaseous magnesium source; The magnesium source supply system comprises: Magnesium block placement area: located at the bottom of the furnace, used to evenly place magnesium blocks; Water-cooled insulation cover: installed at the feed inlet at the top of the furnace body to prevent the cover from overheating; Gas system: set at the bottom of the furnace body, used to introduce high-purity argon as protective gas; The temperature sensor is installed in the electric heating pit furnace to monitor the temperature changes during the reaction.

2. The device according to claim 1, characterized in that: The reaction container is a cylindrical stainless steel furnace body, the inner wall of which is lined with alumina fiber felt, a high-temperature resistant heat-insulating material.

3. The device according to claim 1, characterized in that: The reaction tower tray has multiple layers and is made of high-purity tantalum sheets, all of which are horizontally placed in the furnace.

4. The device according to claim 1, characterized in that: The resistance wire has a power of 5-8kW and a maximum temperature resistance of 1200-1400°C.

5. The device according to claim 1, characterized in that The reaction tower tray has 3-5 layers, and the layer spacing is the same.

6. The device according to claim 1, characterized in that The magnesium block placement area is a cylindrical container with a built-in porous partition with a pore diameter of 4-6 mm.

7. A method for preparing tantalum powder by gaseous magnesium reduction using the apparatus according to any one of claims 1 to 6, characterized in that: The following steps are involved: Reduction reaction: Evenly spread tantalum oxide on the upper tray, place magnesium blocks at the bottom of the furnace, introduce high-purity argon gas to replace the air in the furnace 4-8 times, heat to vaporize magnesium, and fully react at 900-1200℃; Post-processing: The reaction product is cooled in a water cooling chamber and then sequentially subjected to water washing, acid washing and vacuum drying.

8. The method according to claim 7, wherein: The tantalum oxide powder is laid with a thickness of 2-4 mm, and the molar ratio of magnesium block to tantalum oxide is (5-8):

1.

9. The method according to claim 7, wherein: The argon flow rate is 200-300mL / min, heating rate is 5-10℃ / min.

10. The method according to claim 7, wherein: The reduction reaction comprises: heating from room temperature to 900-950° C. at a heating rate of 5-8° C. / min, while controlling the pressure at 0.10-0.12 MPa, and keeping the temperature under this condition for 4-6 hours; after the end of the heat preservation, adjusting the pressure in the furnace to 0.03-0.05 Pa, heating to 1095-1200° C. at a heating rate of 8-10° C. / min, keeping the temperature for 0.5-1 hour, and then cutting off the power to cool down.

11. The method according to claim 7, wherein: The post-treatment includes: washing with hot pure water at 60-80° C. until the conductivity is ≤50 μS / cm, pickling with 10-20% hydrochloric acid at 55-65° C. with stirring for 4-6 hours, washing with water until neutral, and finally drying at 75-85° C. and vacuum degree of -0.1 MPa to -0.09 MPa for 8-10 hours.

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