Method for preparing refractory metal powder from spherical raw materials

Abstract

The invention belongs to the field of metal powder preparation, and particularly relates to a method for preparing refractory metal or oxide powder from spherical raw materials. Aiming at the technical defects of low metal powder reduction rate and poor product performance caused by the fact that raw materials and a reducing agent cannot be in full contact due to the problems of a stacking mode or a diffusion path and the like in a traditional reduction process, spherical metal oxide is obtained through granulation, and good gaps exist among spherical metal oxide particles; on one hand, the reducing agent is in full contact with the raw materials, the reaction efficiency is improved, on the other hand, products obtained after the spherical metal oxide is reduced are more uniform, the physical performance of the powder is improved, especially the fluidity of the powder is improved, the application performance of the powder is greatly improved, and the application range of the metal powder is effectively expanded. And the method can be applied to the field with higher performance requirement range.

Description

Technical Field

[0001] The invention belongs to the field of metal powder preparation, and in particular relates to a method for preparing refractory metal powder by utilizing spherical raw materials. Background Art

[0002] Metal vapor reduction is an advanced process that uses reactive metal vapor as a strong reducing agent to reduce high-melting-point, difficult-to-reduce metal oxides through a high-temperature gas-solid reaction to produce high-purity metal powders. Its core advantages are reflected in four aspects: First, its outstanding reducing power allows it to efficiently treat oxides that are difficult to reduce using conventional methods; second, its high product purity and easy separation of byproducts (such as MgO and CaO) help ensure the high purity of the final metal powder; third, its precise and controllable reaction conditions allow for effective control of powder particle size and morphology by adjusting vapor pressure and temperature; and fourth, its wide range of applications, including the preparation of metals such as titanium (Ti), zirconium (Zr), tantalum (Ta), niobium (Nb), uranium (U), and rare earth elements.

[0003] In the gas-solid reduction process, a reducing metal is typically placed at the bottom of a furnace chamber or crucible, with the raw oxide placed above it. The furnace chamber or crucible is heated to vaporize the reducing metal into a gaseous state, where it then undergoes a reduction reaction with the oxide above. Ensuring smooth and uniform contact and reaction between the metal vapor and the oxide is a key technical step in ensuring product performance and improving reduction efficiency.

[0004] In traditional reduction processes, the morphology and structure of raw oxides vary significantly. When stacked in a furnace chamber or crucible, the pore structure in different areas exhibits significant heterogeneity: some areas have higher porosity and larger gaps, while others have extremely low porosity or even no effective voids due to the densely packed particles. This heterogeneous pore structure directly affects the flow and reaction path of metal vapor. Vapor preferentially penetrates and reduces areas with higher porosity, while areas with lower porosity are hindered by vapor diffusion, causing the reduction reaction to lag or even fail to fully proceed. Ultimately, this leads to a decrease in the overall reduction rate of the raw materials and fluctuations in product performance, restricting its application areas and scope.

[0005] For example, the invention with application number: 202111617166.4 discloses a spheroidization process for refractory metal powder. The invention uses hydrogen peroxide and polyol to pretreat nano-scale refractory metal oxides, and then uses a plasma spheroidization device to reduce and spheroidize the pretreated refractory metal oxides to obtain nano-scale refractory metal spherical particles. However, the metal properties produced by this invention have poor uniformity.

[0006] In addition, the reduction reaction itself is accompanied by a high heat release. If the reducing agent is not in sufficient contact with the raw materials, it will not only increase the risk of local overheating, but also hinder the timely dissipation of heat, further destroying the uniformity of the reaction environment, resulting in a decrease in the uniformity of the obtained product. Therefore, how to ensure sufficient contact between the reducing agent and the raw materials by optimizing the raw material stacking method, regulating the vapor diffusion path, etc., while achieving efficient conduction and dispersion of the reaction heat, and constructing a uniform, stable and controllable reduction environment, is a key technical challenge to improve the reduction efficiency of metal powders and ensure high product performance. In summary, providing a metal reduction method that can improve the reduction efficiency of metal powders and ensure high product performance is a difficult problem that needs to be solved at present. Summary of the Invention

[0007] Based on the above technical background, the main purpose of the present invention is to provide a method for preparing refractory metal powder using spherical raw materials to overcome the shortcomings of the existing technology.

[0008] To achieve the aforementioned object of the invention, the technical solutions adopted by the present invention include: The present invention provides a method for preparing refractory metal powder using spherical raw materials, the method comprising the following steps: The metal oxide is spheroidized and granulated, and then a reducing metal is added and the temperature is raised to perform a metal thermal reduction reaction. After the reaction is completed, the reduction reaction product is acid-washed to obtain a metal powder.

[0009] Preferably, the granulation method includes agglomeration granulation and spray granulation, and also includes agglomerating the oxide, the reducing agent and the diluent salt after mixing.

[0010] The diluting salt is selected from one or more of potassium chloride, sodium chloride and calcium chloride.

[0011] Preferably, the diluent salt is potassium chloride. The present invention can absorb the heat released by the reaction by adding a diluent.

[0012] The metal oxide is selected from one or more of tantalum oxide, niobium oxide, titanium oxide, iron oxide and zirconium oxide.

[0013] Preferably, the metal oxide is tantalum oxide or niobium oxide.

[0014] The reducing metal is selected from one or more of magnesium, calcium, rare earth metals lanthanum and neodymium.

[0015] Preferably, the reducing metal is magnesium.

[0016] The present invention improves the particle structure of the metal oxide, enhances the fluidity of the particles, increases the specific surface area of ​​the particles, and when the spherical particles are stacked together, there are still good gaps between the particles, which is beneficial to improving the reduction reaction efficiency.

[0017] According to a preferred embodiment of the present invention, the agglomeration granulation method comprises the following steps: Step 1, adding a wetting agent and a binder to the metal oxide to obtain a wetted metal oxide; Step 2: vibrate and rotate the wetted metal oxide to obtain spherical metal oxide particles, and then dry them to obtain agglomerated metal oxide particles.

[0018] The above steps are described in detail below.

[0019] In step 1, the wetting agent is selected from one or more of water, ethanol, and ammonium chloride.

[0020] Preferably, the wetting agent is water or ethanol.

[0021] The added amount of the wetting agent is 5% to 100% of the mass of the metal oxide.

[0022] Preferably, the amount of the wetting agent added is 15% to 100% of the mass of the metal oxide.

[0023] The binder is selected from one or more of polyvinyl alcohol, polyethylene glycol, and carboxymethyl cellulose.

[0024] Preferably, the binder is polyvinyl alcohol or polyethylene glycol.

[0025] The added amount of the binder is 0.2-3% of the mass of the metal oxide.

[0026] Preferably, the added amount of the binder is 0.5 to 2.75% of the mass of the metal oxide.

[0027] In step 2, the vibration rotation is preferably performed on a vibrating rotating disk.

[0028] The drying conditions are: drying at 50-300° C. for 1-15 hours to remove moisture from the raw materials.

[0029] Preferably, the drying conditions are: drying at 60-150° C. for 3-12 hours.

[0030] According to a preferred embodiment of the present invention, the spray granulation method comprises the following steps: Water, dispersant and grinding balls are added to the metal oxide for wet grinding, and then a binder is added and wet grinding is continued. The grinding balls are then filtered to obtain a liquid material, and finally spray granulation is performed to obtain metal oxide agglomerated particles.

[0031] Preferably, the amount of water added is 90-150% of the mass of the metal oxide.

[0032] More preferably, the amount of water added is 100% of the mass of the metal oxide.

[0033] The dispersant is selected from one or more of polyacrylic acid, ammonium polyacrylate, and phosphate.

[0034] Preferably, the dispersant is polyacrylic acid. The addition of the dispersant can prevent the raw materials from agglomerating into lumps during the ball milling process.

[0035] The added amount of the dispersant is 1 to 2% of the mass of the metal oxide.

[0036] Preferably, the added amount of the dispersant is 1.5% of the mass of the metal oxide.

[0037] The ratio of the number of large grinding balls, medium grinding balls and small grinding balls in the grinding balls is 1:(1-3):1.

[0038] Preferably, the ratio of the number of large grinding balls, medium grinding balls and small grinding balls in the grinding balls is 1:2:1.

[0039] The wet grinding time is 4 to 50 hours, preferably, the wet grinding time is 48 hours.

[0040] The binder is selected from one or more of polyvinyl alcohol, polyethylene glycol, and carboxymethyl cellulose.

[0041] Preferably, the binder is polyvinyl alcohol or polyethylene glycol.

[0042] The added amount of the binder is 0.2-3% of the mass of the metal oxide.

[0043] Preferably, the added amount of the binder is 0.5% of the mass of the metal oxide.

[0044] After adding the binder, wet grinding is continued for 0.5 to 10 hours. Preferably, wet grinding is continued for 1 hour after adding the binder.

[0045] The raw materials after spray granulation are screened to obtain metal oxide agglomerated particles with a particle size of 20-50 μm.

[0046] The molar ratio of the reducing metal to the metal oxide is (9-15):1.

[0047] Preferably, the molar ratio of the reducing metal to the metal oxide is (10-12.5):1.

[0048] The temperature of the thermal reduction reaction of the reducing metal is 500-1100° C., and the time of the thermal reduction reaction of the reducing metal is 1-8 hours.

[0049] The present invention utilizes spherical raw materials for reduction, ensuring that the reducing agent can evenly pass through each particle during the reduction process and react with the raw materials, and the heat released by the reaction can be discharged in time, thereby improving the uniformity and stability of the reduction.

[0050] Preferably, the temperature of the thermal reduction reaction of the reducing metal is 850-1000° C., and the time of the thermal reduction reaction of the reducing metal is 3-8 hours.

[0051] The temperature and reaction time of the reducing metal thermal reduction reaction can ensure that the reduction reaction is fully carried out and improve the reduction effect of the reduction reaction.

[0052] The reduction reaction product is pickled with hydrochloric acid or nitric acid.

[0053] The beneficial effects of the present invention are: (1) The present invention increases the specific surface area of ​​the particles by spheroidizing and granulating the raw materials, making it easier for the particles to contact with the reducing agent for reduction during the reduction process. The contact between the raw materials and the reducing agent is more complete, which is beneficial to improving the reduction efficiency and reduction effect of the raw materials.

[0054] (2) The present invention spheroidizes and granulates the raw materials, so that when the spherical raw materials are piled together, there are good gaps between the spherical particles. This is conducive to the uniform diffusion of the reducing agent during the reduction process, ensuring that the reducing agent can evenly pass through each particle and react with the raw materials during the reduction process. The raw materials can be reduced in a more uniform reaction environment, making the morphology of the reduced product particles more uniform and consistent, and enhancing the stability of the product performance. In addition, the pores between the spherical particles allow the heat released by the reduction reaction to be discharged in a timely manner, which is conducive to further improving the uniformity and stability of the reduction.

[0055] (3) The method of the present invention improves the fluidity of the raw material through spheroidization granulation, so that the product after reduction of the raw material is also spherical, which effectively improves the fluidity of the product and makes the performance of the metal powder more uniform, which is conducive to expanding the application field of the metal powder and allowing the metal powder to be used in fields with higher performance requirements. For example, the prepared tantalum metal powder has better application prospects in high-voltage capacitors. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 A scanning electron microscope photograph of the tantalum powder prepared in Example 1 is shown. DETAILED DESCRIPTION

[0057] The present invention will be described in detail below, and the characteristics and advantages of the present invention will become clearer and more distinct with the following description.

[0058] Example The present invention is further described below by way of specific examples, which are intended to illustrate the present invention but not to limit the scope of the present invention. The raw materials used in the examples of the present invention were all purchased.

[0059] Example 1 Weigh 100g of tantalum oxide, 55g of magnesium, and 120g of potassium chloride (as a diluent to absorb the heat of the reaction) and mix them evenly. Dissolve 2.75g of polyethylene glycol in 88ml of anhydrous ethanol. Add the anhydrous ethanol to the mixed materials to moisten them. Place the moistened materials on a vibrating rotating disk and vibrate and rotate them to form porous spherical particles. Heat the agglomerated spherical particles to 60°C in a vacuum drying oven for 3 hours. Place the dried particles in a crucible and reduce them by heating to 900°C in a tube furnace for 3 hours. The reduced product is then acid-washed with hydrochloric acid or nitric acid to produce tantalum powder.

[0060] By using this method for reduction, all raw materials are agglomerated into spheres. The large gaps between the spherical particles ensure that the heat released by the reaction system can be discharged quickly and smoothly, thereby ensuring the stability of the system and making the reaction process more controllable.

[0061] Example 2 Weigh 100g of niobium oxide, 55g of magnesium, and 120g of potassium chloride (as a diluent to absorb the heat of the reaction) and mix them evenly. Dissolve 2g of polyethylene glycol in 100ml of anhydrous ethanol. Add the anhydrous ethanol to the mixed ingredients to moisten them. Place the moistened ingredients on a vibrating rotating disk and vibrate and rotate them to form porous spherical particles. Heat the agglomerated spherical particles to 60°C in a vacuum drying oven for 4 hours. Place the dried particles in a crucible and reduce them by heating them to 800°C in a tube furnace for 2 hours. The reduced product is then acid-washed with hydrochloric acid or nitric acid to obtain niobium powder.

[0062] Example 3 Weigh 100g of tantalum oxide, 55g of magnesium, and 120g of potassium chloride (as a diluent to absorb the heat of the reaction) and mix them evenly. Dissolve 3g of polyethylene glycol in 70ml of anhydrous ethanol. Add the anhydrous ethanol to the mixed materials to moisten them. Place the moistened materials on a vibrating rotating disk and vibrate and rotate them to form porous spherical particles. Heat the agglomerated spherical particles to 70°C in a vacuum drying oven for 3 hours. Place the dried particles in a crucible and reduce them by heating them to 1000°C in a tube furnace for 4 hours. The reduced product is then acid-washed with hydrochloric acid or nitric acid to produce tantalum powder.

[0063] Example 4 Take 200g of tantalum oxide and 30ml of water, dissolve 1g of polyvinyl alcohol in the water, add the water to the tantalum oxide to moisten it, place the moistened material on a vibrating rotating plate, and vibrate and rotate the tantalum oxide to agglomerate into spherical particles. Heat the agglomerated spherical particles to 150°C in a drying oven for 12 hours to remove moisture. The dried agglomerated tantalum oxide particles are placed in a sintering furnace under vacuum and heated to 1000°C for 8 hours to sinter the tantalum oxide spherical particles into porous spherical particles. Tantalum oxide and magnesium powders are weighed in a molar ratio of 1:12.5, mixed evenly, and placed in a tube furnace. Heated to 850°C for 6 hours, the reduced product is pickled with hydrochloric acid or nitric acid to obtain tantalum powder.

[0064] The reduction method ensures that magnesium can fully contact the tantalum oxide raw material during the reduction process, making the reduction more complete; at the same time, the reduced product tantalum powder maintains the particle shape of the spherical raw material tantalum oxide, and the fluidity is significantly improved. Example 5 Take 200g of niobium oxide and 50ml of water, dissolve 4g of polyvinyl alcohol in the water, then add the water to wet the niobium oxide. Place the wetted material on a vibrating rotating plate and vibrate and rotate the niobium oxide to agglomerate into spherical particles. Heat the agglomerated spherical particles to 150°C in a drying oven for 10 hours to remove moisture. Place the dried agglomerated niobium oxide particles in a sintering furnace under vacuum and heat to 1000°C for 8 hours to sinter the niobium oxide spherical particles into porous spherical particles. Weigh niobium oxide and magnesium powders in a molar ratio of 1:10, mix them evenly, place them in a tube furnace, heat to 900°C, and hold for 6 hours. The reduced product is then pickled with hydrochloric acid or nitric acid to obtain niobium powder.

[0065] Example 6 Take 200g of tantalum oxide and 50ml of water, dissolve 3g of polyvinyl alcohol in the water, add the water to the tantalum oxide to moisten it, place the moistened material on a vibrating rotating plate, and vibrate and rotate the tantalum oxide to agglomerate into spherical particles. Heat the agglomerated spherical particles to 120°C in a drying oven for 12 hours to remove moisture. Place the dried agglomerated tantalum oxide particles in a sintering furnace under vacuum and heat to 1000°C for 8 hours to sinter the metal oxide spherical particles into porous spherical particles. Weigh tantalum oxide and magnesium powders in a molar ratio of 1:11, mix them evenly, place them in a tube furnace, heat to 1000°C, and hold for 5 hours. The reduced product is then pickled with hydrochloric acid or nitric acid to obtain tantalum powder.

[0066] Example 7 300g of tantalum oxide is placed in a ball mill. At the same time, 600g of grinding balls (large, medium, and small in a ratio of 1:2:1), 300ml of water, and 1.5% polyacrylic acid (by weight) of the tantalum oxide are added for wet grinding. After 48 hours of wet grinding, 0.5% polyvinyl alcohol (by weight) of the tantalum oxide is added and ball milled for another hour. The grinding balls are removed with a filter to obtain a liquid material. The liquid material is then atomized and dried into spherical raw materials using a spray granulator. The atomized raw materials are sieved to obtain spherical tantalum oxide with a particle size of 20-50μm. A certain amount of magnesium powder and tantalum oxide are then weighed in a molar ratio of tantalum oxide to magnesium of 1:10. Using a gaseous metal reduction method, the tantalum oxide is placed on top, followed by reduced metal magnesium powder. The reduced metal is heated to 900°C for 8 hours. The reduced product is then pickled with hydrochloric acid or nitric acid to obtain tantalum powder.

[0067] The reduction method ensures uniform and smooth circulation of the reducing metal vapor in the tantalum oxide raw material. During the reduction process, the reducing metal magnesium can fully contact the tantalum oxide raw material, making the reduction more complete. At the same time, the reduced product tantalum powder can maintain the particle shape of the spherical raw material tantalum oxide, and the fluidity is significantly improved. Experimental example Experimental Example 1 SEM test The tantalum powder obtained in Example 1 was tested by scanning electron microscopy. The test results are as follows: Figure 1 shown.

[0068] from Figure 1 It can be seen that the primary particles of the tantalum powder are between 200 and 300 nm, with uniform particle size and good sintered structure, and the secondary particles are spherical, which makes the tantalum powder have better fluidity, indicating that the reduction method described in the present invention can produce metal powder with better fluidity.

[0069] The present invention has been described in detail above with reference to specific embodiments and exemplary examples. However, these descriptions should not be construed as limiting the present invention. Those skilled in the art will appreciate that various equivalent substitutions, modifications, or improvements may be made to the technical solutions and implementations of the present invention without departing from the spirit and scope of the present invention, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for preparing refractory metal powder using spherical raw materials, characterized in that: The method comprises the following steps: The metal oxide is spheroidized and granulated, and then a reducing metal is added and the temperature is raised to perform a metal thermal reduction reaction. After the reaction is completed, the reduction reaction product is acid-washed to obtain a metal powder; The granulation methods include agglomeration granulation and spray granulation.

2. The method according to claim 1, characterized in that The method of agglomeration and granulation comprises the following steps: Step 1, adding a wetting agent and a binder to the metal oxide to obtain a wetted metal oxide; Step 2: vibrate and rotate the wetted metal oxide to obtain spherical metal oxide particles, and then dry them to obtain agglomerated metal oxide particles.

3. The method according to claim 2, characterized in that In step 1, The wetting agent is selected from one or more of water, ethanol, and ammonium chloride; The added amount of the wetting agent is 5% to 100% of the mass of the metal oxide.

4. The method according to claim 2, characterized in that In step 1, The binder is selected from one or more of polyvinyl alcohol, polyethylene glycol, and carboxymethyl cellulose; The added amount of the binder is 0.2-3% of the mass of the metal oxide.

5. The method according to claim 1, wherein The method of spray granulation comprises the following steps: Water, a dispersant and grinding balls are added to the metal oxide for wet grinding, and then a binder is added and the wet grinding is continued. The grinding balls are then filtered to obtain a liquid material, and finally spray granulation is performed to obtain metal oxide particles.

6. The method according to claim 5, characterized in that The dispersant is selected from one or more of polyacrylic acid, ammonium polyacrylate, and phosphate; The added amount of the dispersant is 1 to 2% of the mass of the metal oxide.

7. The method according to claim 5, characterized in that The ratio of the number of large grinding balls, medium grinding balls and small grinding balls in the grinding balls is 1: (1 to 3): 1; The wet grinding time is 4 to 50 hours.

8. The method according to claim 5, characterized in that After adding the binder, continue wet grinding for 0.5 to 10 hours.

9. The method according to claim 1, characterized in that The molar ratio of the reducing metal to the metal oxide is (9-15):

1.

10. The method according to claim 1, characterized in that The temperature of the thermal reduction reaction of the reducing metal is 500-1100° C., and the time of the thermal reduction reaction of the reducing metal is 1-8 hours.

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