Device for preparing refractory metal powder through layered reduction
By using a layered reduction device and controlling the reduction process, the problem of impurities during magnesium reduction was solved, enabling the efficient preparation of refractory metal powders and improving the quality and uniformity of tantalum powder.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- ZHENGZHOU UNIV
- Filing Date
- 2025-05-21
- Publication Date
- 2026-04-21
AI Technical Summary
In the existing process of preparing refractory metal powders, impurities are easily introduced during magnesium reduction. The addition of salt affects the uniform contact between magnesium and tantalum oxide, resulting in poor reduction effect.
A layered reduction device is adopted, in which diluted salt and reducing agent are laid in layers in the reactor, and the reduction reaction of refractory metal oxides at different layers is controlled by a lifting mechanism. Combined with vacuum and inert gas protection, the salt is used to avoid damage to the product structure and promote the reduction effect.
It improves the surface activity and particle uniformity of refractory metal powder, reduces impurity content, and improves the flowability and particle structure of tantalum powder.
Smart Images
Figure CN224143496U_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of refractory metal preparation technology, specifically relating to an apparatus for preparing refractory metal powder by layered reduction. Background Technology
[0002] Refractory metals generally refer to metals with melting points above 1650℃, mainly including tungsten, tantalum, molybdenum, niobium, and rhenium. Tantalum, a rare refractory metal with a high melting point, excellent corrosion resistance (especially in acidic media where it can form a dense oxide film), and good biocompatibility, is a core material for manufacturing miniature high-capacitance tantalum capacitors due to its high specific surface area. Tantalum is widely used in consumer electronics, communication equipment, automotive electronics, and medical fields. Its primary application is in the manufacture of tantalum capacitors; the quality of tantalum powder, the raw material for tantalum capacitors, determines the performance of the capacitors. Niobium, a silvery-gray rare high-melting-point metal, possesses excellent superconductivity, corrosion resistance, and wear resistance, and is widely used in steel, superconducting materials, aerospace, and nuclear energy.
[0003] Taking tantalum powder preparation as an example, there are currently only two industrialized processes for tantalum powder preparation: the sodium reduction of potassium fluorotantalate and the magnesium reduction of tantalum oxide. The sodium reduction of potassium fluorotantalate uses potassium fluorotantalate as a raw material and metallic sodium as a reducing agent, undergoing a displacement reaction in a high-temperature molten state (700–900℃) to produce metallic tantalum powder. This method is relatively mature and can be used for large-scale production of high-specific-capacity tantalum powder with small particles and large specific surface area. However, the resulting tantalum powder has uneven particle size and a relatively high impurity content.
[0004] Magnesium reduction of tantalum oxide can be classified into three types according to the reduction method: the magnesothermic self-propagating method, the gaseous magnesium reduction method, and the liquid magnesium reduction method. Among them, the magnesothermic self-propagating method involves pressing tantalum oxide and magnesium into blocks, igniting them, and using the heat released by the reaction to ignite other areas for further reaction. This method has a fast reaction rate, high reaction temperature, and results in uneven tantalum powder particles with severe sintering between particles, leading to poor controllability.
[0005] The gaseous magnesium reduction method utilizes magnesium vapor to react with raw materials, but magnesium vapor in the gaseous magnesium reduction system is difficult to control, and the requirements for the reaction equipment are high.
[0006] Liquid magnesium reduction utilizes liquid magnesium. A common reduction method involves uniformly mixing magnesium, tantalum oxide, and a diluted salt, then heating the mixture to a specific temperature for reaction. In this system, magnesium acts as a reducing agent, and the salt acts as a diluent, absorbing excess heat released during the reaction. The salt also improves particle morphology and surface activity. However, the presence of salt disrupts the structure of the reduction products, leading to smaller, more complex secondary tantalum powder particles and reduced flowability. Furthermore, the addition of salt affects the uniform contact between magnesium and tantalum oxide, thus impacting the reduction efficiency. Utility Model Content
[0007] In view of the above situation, this utility model provides an apparatus for preparing refractory metal powder by layered reduction, which solves the technical problem that when other reduction methods in the prior art only add magnesium for liquid reduction, the reduced tantalum powder has strong surface activity and is easy to introduce impurities; while adding salt can improve this phenomenon and improve the uniformity of tantalum powder particles to a certain extent; when magnesium and salt are added for mixed reduction, the addition of salt will also affect the uniform contact between magnesium and tantalum oxide, thus affecting the reduction effect.
[0008] To achieve the above objectives, the present invention adopts the following technical solution:
[0009] An apparatus for preparing refractory metal powder by layered reduction includes a reactor, a heater fixedly disposed outside the reactor, and a tray that can be raised and lowered inside the reactor. A lifting mechanism is connected above the tray. The reactor interior is layered with diluent salt and reducing agent from bottom to top. The tray contains refractory metal oxide raw material. The tray and the refractory metal oxide raw material can be raised and lowered and submerged in the reducing agent or diluent salt by the lifting mechanism. A vacuum tube is provided at the top of the reactor, one end of which is connected to the inside of the reactor, and the other end is connected to a vacuum device for evacuating the reactor interior. The top of the reactor also has an inlet and an outlet for introducing and discharging inert gas into the reactor to create an inert gas protective atmosphere inside the reactor.
[0010] Preferably, the reactor is a sealable cylindrical tank structure, and the reactor is made of nickel-based alloy material. The air inlet, air outlet and vacuum pipe are all connected through the top cover of the reactor.
[0011] Preferably, the tray is a disc-shaped structure with a U-shaped longitudinal section and an open top, and the tray is made of nickel-based alloy material.
[0012] Preferably, the lifting mechanism includes a lifting rod and a lifting device. The lower end of the lifting rod is connected to the center of the tray, and the upper end of the lifting rod is connected to the lifting end of the lifting device. The lifting rod is also made of a nickel-based alloy material.
[0013] Preferably, the lifting device is an electric telescopic pole.
[0014] Preferably, the vacuum device is a vacuum pump.
[0015] Preferably, the inert gas is argon.
[0016] Preferably, the refractory metal is tantalum or niobium; the refractory metal oxide raw material is tantalum oxide or niobium oxide. This invention can be used to prepare refractory metals tantalum or niobium. Of course, this apparatus can also be applied to the preparation of other refractory metals such as tungsten, molybdenum, and rhenium.
[0017] Preferably, the reducing agent is magnesium or calcium.
[0018] Preferably, the diluent salt is one or a mixture of different rare earth salts selected from potassium chloride, sodium chloride, magnesium chloride, calcium chloride, lanthanum chloride, etc.
[0019] This utility model also includes other components that enable its normal use, all of which are conventional means in the field. In addition, devices or components not limited in this utility model, such as reactors, heaters, vacuum pumps, electric telescopic rods, etc., all adopt existing technologies in the field.
[0020] The working principle of this utility model is as follows:
[0021] Before the preparation of refractory metals begins, a certain height of diluted salt (a single rare earth salt such as potassium chloride, sodium chloride, magnesium chloride, calcium chloride, and lanthanum chloride, or a mixture of different salts) is first laid at the bottom of the reactor. Then, a certain height of reducing agent (Mg, Ca, etc.) is laid on top of the salt, and a certain amount of refractory metal oxide raw material (tantalum oxide or niobium oxide, etc.) is placed in a tray. The vacuum system is then turned on to evacuate the upper reaction zone and magnesium evaporation zone of the reactor. Argon gas is then used to purge and clean the reactor at a certain flow rate, repeating this process several times before the vacuum system is turned off. During the reaction, the reactor is first heated (800-1100℃). After the diluted salt and reducing agent have completely melted, the tray containing the refractory metal oxide raw material is lowered to the reducing agent layer via a lifting mechanism for reduction reaction, and held at this temperature for a certain time (0-8h). Then, it is lowered to the diluted salt layer and held at this temperature for another certain time (0-12h). After the heat preservation is completed, the reactor and the refractory metal (tantalum or niobium) generated by reduction are allowed to cool naturally to room temperature. Then, the reduction product is subjected to acid washing and water washing, followed by drying treatment, and finally the corresponding refractory metal tantalum powder or niobium powder is obtained.
[0022] The beneficial effects of this utility model are as follows:
[0023] This invention provides a layered reduction apparatus and a layered reduction preparation method for tantalum powder. Of course, this apparatus can also be applied to the preparation of other refractory metals such as niobium. First, the powder is reduced in the upper layer of magnesium molten liquid for a certain period of time, which eliminates the influence of dilution salt that may be affected during the reduction process, does not damage the product structure, and promotes the reduction reaction and enhances the reduction effect. Then, the powder enters the lower layer of molten salt system containing dilution salt and is kept at a certain temperature for a period of time. This improves the surface activity of tantalum powder particles, reduces the impurity content on the surface of tantalum powder, promotes the growth and sintering of small particles, and improves particle uniformity and pore structure. Attached Figure Description
[0024] Figure 1 This is a schematic diagram of the apparatus for preparing refractory metal powder by layer reduction in the embodiment. Detailed Implementation
[0025] The technical solution of this utility model will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments.
[0026] Example
[0027] like Figure 1 As shown, an apparatus for preparing refractory metal powder by layered reduction includes a reactor 1 with a sealable cylindrical tank structure made of nickel-based alloy material, a heater 2 fixedly installed on the outside of the reactor, and a tray 3 that can be lifted and lowered inside the reactor. The heater uses resistance heating wire, and the tray is a disc-shaped structure with a U-shaped longitudinal section and an open top, also made of nickel-based alloy material. A lifting mechanism is connected to the top of the tray. The lifting mechanism includes a lifting rod 4 and a lifting device 5. The lower end of the lifting rod is connected to the center of the tray, and the upper end of the lifting rod is connected to the lifting end of the lifting device via a connector. The lifting rod, like the reactor and tray, is also made of nickel-based alloy material; the lifting device is an electric telescopic rod. The electric telescopic rod and resistance heating wire, etc., are all existing technologies and will not be described in detail here.
[0028] The reactor interior is layered from bottom to top with diluting salt 6 and reducing agent 7. In this embodiment, the device is mainly used to prepare refractory tantalum powder. The tray contains refractory metal oxide raw material 8, in this case tantalum oxide. The tray and tantalum oxide raw material can be raised and lowered by the lifting mechanism to be submerged in the reducing agent or diluting salt. The reducing agent is magnesium, and the diluting salt is a mixture of potassium chloride and sodium chloride.
[0029] A vacuum tube is installed at the top of the reactor. One end of the vacuum tube is connected to the inside of the reactor, and the other end is connected to a vacuum device 9, which is a vacuum pump, used to evacuate the inside of the reactor. The top of the reactor also has an inlet 10 and an outlet 11 for introducing and discharging inert gas into the reactor to create a protective atmosphere. Before the reaction begins, the reactor is evacuated, and then inert gas is introduced for purging to ensure the protective atmosphere inside the reactor. The outlet is used to discharge excess inert gas, which is argon. The inlet, outlet, and vacuum tube are all connected to the top cover of the reactor.
[0030] Specifically, before the reaction begins, potassium chloride and sodium chloride are uniformly mixed in a 1:1 molar ratio to form a mixed salt. A 20cm thick layer of this mixed salt is then laid at the bottom of the reactor, followed by a 15cm thick layer of magnesium shavings. 200g of tantalum oxide is placed in the tray. The vacuum pump is then turned on to evacuate the reactor to a vacuum level, and argon gas is continuously purged at a flow rate of 600ml / min. This process is repeated several times before the vacuum system is shut off. The reaction temperature is then raised to 900℃ to melt the diluted salt and magnesium. A lifting device is then activated to lower the tray containing the tantalum oxide raw material to the magnesium layer to begin reduction. After holding at this temperature for 2 hours, the tray is lowered to the diluted salt layer and held at this temperature for another 8 hours. Due to the different surface tensions and other properties of the diluted salt and magnesium, the molten magnesium and diluted salt do not fuse together. After the required holding time is reached, the mixture is allowed to cool naturally to room temperature. The reduction product is then first acid-washed to remove oxide byproducts, followed by water washing to remove soluble salts produced during the acid washing process. Finally, it is filtered and dried to obtain refractory tantalum powder.
[0031] Example 2
[0032] The difference from Example 1 is that the apparatus in this example is mainly used to prepare the refractory metal niobium. The refractory metal oxide raw material is niobium oxide; the reducing agent is calcium powder; and the diluent salt is a single rare earth salt such as potassium chloride, sodium chloride, magnesium chloride, calcium chloride, or lanthanum chloride.
[0033] The technical solution of this utility model is not limited to the specific embodiments described above. Without departing from the scope and spirit of the described embodiments, many modifications and changes will be obvious to those skilled in the art. Any technical modifications made within the spirit and principles of this utility model shall fall within the protection scope of this utility model.
Claims
1. An apparatus for preparing refractory metal powder by layered reduction, characterized in that: The reactor includes a heater fixedly installed on the outside of the reactor and a tray that can be raised and lowered inside the reactor, with a lifting mechanism connected above the tray. The reactor interior is layered with diluent salt and reducing agent from bottom to top. The tray contains refractory metal oxide raw materials, and the tray and refractory metal oxide raw materials can be raised and lowered under the action of the lifting mechanism to be submerged in the reducing agent or diluent salt. A vacuum pipe is installed at the top of the reactor, one end of which is connected to the inside of the reactor, and the other end is connected to a vacuum device for evacuating the reactor interior. The top of the reactor also has an inlet and an outlet for introducing and discharging inert gas into and out of the reactor to create an inert gas protective atmosphere inside the reactor.
2. A device for the production of refractory metal powders by successive reduction according to claim 1, characterized in that: The reactor is a sealable cylindrical tank structure made of nickel-based alloy material. The air inlet, air outlet and vacuum tube are all connected to the top cover of the reactor.
3. The apparatus for producing refractory metal powder by a layered reduction according to claim 1, characterized in that: The tray is a disc-shaped structure with an open top, and it is made of nickel-based alloy material.
4. A device for the production of refractory metal powders by a layered reduction according to claim 3, characterized in that The lifting mechanism includes a lifting rod and a lifting device. The lower end of the lifting rod is connected to the center of the tray, and the upper end of the lifting rod is connected to the lifting end of the lifting device.
5. A device for the production of refractory metal powders by a layered reduction according to claim 4, characterized in that The lifting device is an electric telescopic pole.
6. The apparatus for producing refractory metal powder by a layered reduction according to claim 1, characterized by: The vacuum device is a vacuum pump.
7. The apparatus for preparing refractory metal powder by layered reduction according to claim 1, characterized in that: The inert gas is argon.
8. A device for the production of a refractory metal powder by successive reduction according to any one of claims 1 to 7, characterized in that: The refractory metal is tantalum or niobium; the refractory metal oxide raw material is tantalum oxide or niobium oxide.
9. A device for the production of refractory metal powders by a layered reduction according to claim 8, characterized in that The reducing agent is magnesium or calcium.
10. A device for the production of refractory metal powder by a layered reduction according to claim 9, characterized in that The diluent is potassium chloride, sodium chloride, magnesium chloride, calcium chloride, or lanthanum chloride.