Method for preparing nano tungsten powder by using activated aluminum oxide and nano tungsten powder

Abstract

The invention belongs to the technical field of nano powder material preparation, and particularly relates to a method for preparing nano tungsten powder from activated aluminum oxide and nano tungsten powder.The method comprises the following steps that S1, tungsten oxide and activated aluminum oxide balls are evenly mixed according to the mass ratio of 1: (1-2), and a premix is obtained; s2, heating and reducing the premix in a hydrogen atmosphere to obtain a mixture; s3, the mixture is screened, and nano tungsten powder and activated aluminum oxide balls are obtained; the high water absorption performance of activated aluminum oxide is utilized, water vapor generated in a system is efficiently adsorbed, and it is ensured that the particle size of tungsten powder is stably controlled at the nanoscale; the porous structure can physically block mutual contact and combination of nucleated tungsten particles, and agglomeration of tungsten powder is effectively reduced; the method has the advantages of high process compatibility, capability of fine adjustment based on the existing process, controllable raw material cost, better economical efficiency, no complex process in the operation process and easiness in realization of large-scale stable production.

Description

Technical Field

[0001] This invention belongs to the field of nanopowder material preparation technology, specifically a method for preparing nano-tungsten powder using activated alumina and the nano-tungsten powder itself. Background Technology

[0002] High-quality nano-tungsten powder is the core raw material for preparing high-performance tungsten materials. Its key performance indicators, such as particle size distribution uniformity, purity level and microstructure integrity, directly determine the final quality and core performance level of downstream key products such as tungsten-based composite materials, cemented carbide, and ultrafine crystalline tungsten products. Currently, the mainstream process for preparing tungsten powder in the industrial field is the hydrogen reduction tungsten oxide method. Although this process is mature and widely used, it has two major technical bottlenecks: First, the problem of particle coarsening dominated by gas phase migration: In a high-temperature and humid hydrogen environment, the intermediate products generated during the reduction process (such as WO2) are prone to react with water vapor in the system to generate volatile gaseous hydrate WO2(OH)2. After this hydrate diffuses to the surface of the nucleated tungsten particles with hydrogen, it is reduced by hydrogen and converted back into tungsten and deposited. Finally, the Ostwald ripening mechanism continuously promotes the growth of tungsten particles, making it difficult to control the particle size. Second, the problem of limited nucleation kinetics: Due to the high diffusion barrier of tungsten atoms and the large nucleation barrier during the formation of tungsten crystal nuclei, it is difficult to achieve high-density uniform nucleation in the system. This not only results in a small number of crystal nuclei but also makes the initial tungsten particle size larger, further aggravating the particle coarsening effect in the subsequent deposition process.

[0003] Constrained by the two major technological bottlenecks mentioned above, existing processes struggle to reliably produce high-quality nano-tungsten powder with narrow particle size distribution, satisfactory purity, and excellent microstructure adaptability. Meanwhile, with the ever-increasing demand for high-performance tungsten materials in aerospace, high-end equipment manufacturing, and the nuclear industry, overcoming the limitations of existing hydrogen reduction processes and developing new methods for efficiently preparing high-quality nano-tungsten powder has become a critical technological challenge urgently needing to be addressed in the field of tungsten materials. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for preparing nano-tungsten powder using activated alumina, comprising the following steps: S1. Tungsten oxide and activated alumina balls are uniformly mixed at a mass ratio of 1:(1~2) to obtain a premix, wherein the particle size of the activated alumina balls is 0.5~8mm; S2. The premix is ​​reduced by heating in a hydrogen atmosphere to obtain a mixture; S3. The mixture is sieved to obtain nano-tungsten powder and activated alumina balls.

[0005] Specifically, step S1 involves mixing tungsten oxide and activated alumina balls uniformly at a mass ratio of 1:(1~2) using a three-dimensional motion mixer to obtain a premix.

[0006] Specifically, step S2 involves placing the premixed material in a ceramic boat, placing the ceramic boat in a tube furnace, and introducing hydrogen gas for reduction to obtain the mixture.

[0007] In step S2, the hydrogen flow rate of the hydrogen atmosphere is 3~5L / min.

[0008] In step S2, the heating reduction includes: a first stage of heating reduction, a second stage of heating reduction, and a third stage of heating reduction. The temperature of the first stage of heating reduction is 300~350℃ and the time is 0.5~1h. The temperature of the second stage of heating reduction is 500~550℃ and the time is 1~3h. The temperature of the third stage of heating reduction is 650~700℃ and the time is 1~3h.

[0009] In step S2, the heating rate of the reduction process is 5~10℃ / min.

[0010] To solve the above-mentioned technical problems, the present invention also provides nano-tungsten powder, characterized in that the nano-tungsten powder is prepared by the above-mentioned method for preparing nano-tungsten powder using activated alumina.

[0011] The purity of the nano-tungsten powder is greater than or equal to 99%.

[0012] The specific surface area of ​​the nano-tungsten powder is greater than or equal to 4 m². 2 / g.

[0013] The average particle size of the nano-tungsten powder is 20~80nm.

[0014] This invention utilizes the high water absorption capacity of activated alumina to efficiently adsorb water vapor generated within the system, cutting off the "gas migration-deposition coarsening" path at the source and significantly suppressing the Ostwald ripening effect, ensuring stable control of tungsten powder particle size at the nanoscale. Relying on the abundant porous structure and surface active sites of activated alumina, it provides a high-quality heterogeneous nucleation substrate for tungsten atoms—its surface defects lower the nucleation energy barrier, promoting high-density uniform nucleation. Furthermore, the porous structure physically blocks the contact and merging of nucleated tungsten particles, effectively reducing tungsten powder agglomeration and optimizing the microstructure (approaching spherical shape) and dispersibility. The process is highly compatible, requiring no major modifications to traditional hydrogen reduction equipment; it can be fine-tuned based on existing processes; raw material costs are controllable, resulting in good economic efficiency; the operation process is simple, and large-scale stable production is easily achieved. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0016] Figure 1 The image shows a SEM image of the nano-tungsten powder prepared in Example 1. Figure 2 The image shows the XRD pattern of the nano-tungsten powder prepared in Example 1. Figure 3 Here is a SEM image of the tungsten powder prepared in Comparative Example 2; Figure 4 Here is a SEM image of the tungsten powder prepared in Comparative Example 3; Figure 5 Here is a SEM image of the tungsten powder prepared in Comparative Example 4; Figure 6 The image shows a SEM image of the tungsten powder prepared in Comparative Example 5.

[0017] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0018] The technical solutions described below in conjunction with the embodiments will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] This invention provides a method for preparing nano-tungsten powder using activated alumina, comprising the following steps: S1. Tungsten oxide and activated alumina balls are uniformly mixed at a mass ratio of 1:(1~2) to obtain a premix, wherein the particle size of the activated alumina balls is 0.5~8mm; This invention uses activated alumina spheres with a particle size of 0.5~8mm mixed with tungsten oxide to utilize the high water absorption capacity of activated alumina to efficiently adsorb water vapor generated in the system, ensuring that the particle size of the tungsten powder is stably controlled at the nanoscale. If the particle size of the activated alumina spheres is too small, it cannot completely adsorb the water vapor generated in the system and is not easy to separate from the tungsten powder by sieving. If the particle size of the activated alumina spheres is too large, it is difficult to mix them evenly with the tungsten oxide powder. If the mass ratio of tungsten oxide to activated alumina spheres is too large, water adsorption will be incomplete. If it is too small, it is meaningless for the preparation of nano-tungsten powder.

[0020] S2. The premix is ​​reduced by heating in a hydrogen atmosphere to obtain a mixture; In the embodiments of the present invention, nano-tungsten powder can be effectively prepared by three-stage heating reduction. The first stage of heating reduction is a mild reduction, which pretreats water vapor and prepares the ground for nucleation. The second stage of heating reduction is a deep reduction, but at the same time avoids the premature generation of tungsten atoms, which would lead to rapid growth after nucleation. Water vapor can also be adsorbed by active alumina. The third stage of heating reduction is a complete reduction, in which a large number of initial crystal nuclei slowly generate nano-tungsten powder with uniform particle size.

[0021] S3. The mixture is sieved to obtain nano-tungsten powder and activated alumina balls.

[0022] The activated alumina spheres obtained by sieving in this invention can be recycled and reused. The surface activity and water binding capacity of the activated alumina spheres are significantly better than those of nano-tungsten powder: Tungsten oxide generates water vapor during hydrogen reduction. Activated alumina spheres can quickly capture and adsorb water vapor through hydrogen bonding between surface hydroxyl groups and water molecules, as well as the capillary adsorption effect of the porous structure, preventing it from depositing on the surface of nano-tungsten powder and causing the tungsten powder to grow. The adsorbed water vapor is not retained in the activated alumina spheres for a long time: On the one hand, the hydrogen reduction reaction is carried out at a high temperature, which weakens the adsorption force between water vapor and the surface of activated alumina; on the other hand, the hydrogen gas continuously introduced into the reaction system forms an airflow that carries away the desorbed water vapor in time. After adsorption and desorption, the core structure of the alumina spheres remains unchanged, maintaining the initial high specific surface area and surface activity, and can continue to play an adsorption role.

[0023] Example 1 Tungsten oxide and activated alumina spheres were uniformly mixed using a three-dimensional motion mixer to obtain a premix, wherein the activated alumina spheres had a particle size of 0.5~1mm and the mass ratio of tungsten oxide to activated alumina was 1:1. The premix was placed in a ceramic boat, which was then placed in a tube furnace for three-stage reduction with hydrogen gas introduced during the reduction process, resulting in a mixture. The hydrogen flow rate was 5L / min. The first stage of reduction was carried out at 300℃ for 0.5h, the second stage at 500℃ for 1h, and the third stage at 650℃ for 1h, with a heating rate of 10℃ / min for each stage. The mixture was then sieved under a protective atmosphere to obtain activated alumina spheres and nano-tungsten powder. Please see Figure 1 , Figure 1 This is a SEM image of the nano-tungsten powder prepared in Example 1. Figure 1 As can be seen, the nano-tungsten powder has a uniform particle size and no impurity phase.

[0024] Please refer to further information. Figure 2 , Figure 2The image shows the XRD pattern of the nano-tungsten powder prepared in Example 1. Figure 2 As can be seen, the diffraction peaks are sharp and free of impurities, and they are completely matched with the standard tungsten powder XRD pattern (JCPDS No. 04-0806), indicating that the product is a pure phase tungsten crystal with good crystallinity and no residual tungsten oxide or other impurity phases.

[0025] Testing revealed that the nano-tungsten powder had a purity of 99.99% and a specific surface area of ​​7.57 m². 2 / g, with an average particle size of 38nm.

[0026] Example 2 Tungsten oxide and activated alumina spheres were uniformly mixed using a three-dimensional motion mixer to obtain a premix, wherein the activated alumina spheres had a particle size of 0.5~1mm and the mass ratio of tungsten oxide to activated alumina was 1:1. The premix was placed in a ceramic boat, which was then placed in a tube furnace for three-stage reduction with hydrogen gas introduced during the reduction process, resulting in a mixture. The hydrogen flow rate was 5L / min. The first stage of reduction was carried out at 350℃ for 0.5h, the second stage at 550℃ for 1h, and the third stage at 700℃ for 1h, with a heating rate of 5℃ / min for all three stages. The mixture was then sieved under a protective atmosphere to obtain activated alumina spheres and nano-tungsten powder. Testing revealed that the nano-tungsten powder had a purity of 99.99% and a specific surface area of ​​6.62 m². 2 / g, with an average particle size of 47nm.

[0027] Example 3 Tungsten oxide and activated alumina spheres were uniformly mixed using a three-dimensional motion mixer to obtain a premix, wherein the activated alumina spheres had a particle size of 0.5~1mm and the mass ratio of tungsten oxide to activated alumina was 1:1. The premix was placed in a ceramic boat, which was then placed in a tube furnace for three-stage reduction with hydrogen gas introduced during the reduction process, resulting in a mixture. The hydrogen flow rate was 5L / min. The first stage of reduction was carried out at 350℃ for 1 hour, the second stage at 550℃ for 3 hours, and the third stage at 700℃ for 3 hours, with a heating rate of 9℃ / min for all three stages. The mixture was then sieved under a protective atmosphere to obtain activated alumina spheres and nano-tungsten powder. Testing revealed that the nano-tungsten powder had a purity of 99.99% and a specific surface area of ​​4.37 m². 2 / g, with an average particle size of 72nm.

[0028] Example 4 Tungsten oxide and activated alumina spheres were uniformly mixed using a three-dimensional motion mixer to obtain a premix, wherein the activated alumina spheres had a particle size of 0.5~1mm and the mass ratio of tungsten oxide to activated alumina was 1:2. The premix was placed in a ceramic boat, which was then placed in a tube furnace for three-stage reduction with hydrogen gas introduced during the reduction process, resulting in a mixture. The hydrogen flow rate was 5L / min. The first stage of reduction was carried out at 300℃ for 0.5h, the second stage at 500℃ for 1h, and the third stage at 650℃ for 1h, with a heating rate of 10℃ / min for each stage. The mixture was then sieved under a protective atmosphere to obtain activated alumina spheres and nano-tungsten powder. Testing revealed that the nano-tungsten powder had a purity of 99.99% and a specific surface area of ​​7.34 m². 2 / g, with an average particle size of 41nm.

[0029] Example 5 Tungsten oxide and activated alumina spheres were uniformly mixed using a three-dimensional motion mixer to obtain a premix, wherein the activated alumina spheres had a particle size of 6-8 mm and the mass ratio of tungsten oxide to activated alumina was 1:1. The premix was placed in a ceramic boat, which was then placed in a tube furnace for three-stage reduction with hydrogen gas introduced during the reduction process, resulting in a mixture. The hydrogen flow rate was 5 L / min. The first stage of reduction was carried out at 300 °C for 0.5 h, the second stage at 500 °C for 1 h, and the third stage at 650 °C for 1 h, with a heating rate of 10 °C / min for each stage. The mixture was then sieved under a protective atmosphere to obtain activated alumina spheres and nano-tungsten powder. Testing revealed that the nano-tungsten powder had a purity of 99.99% and a specific surface area of ​​5.14 m². 2 / g, with an average particle size of 63nm.

[0030] Example 6 Tungsten oxide and activated alumina spheres were uniformly mixed using a three-dimensional motion mixer to obtain a premix, wherein the activated alumina spheres had a particle size of 0.5~8mm and the mass ratio of tungsten oxide to activated alumina was 1:1. The premix was placed in a ceramic boat, which was then placed in a tube furnace for three-stage reduction with hydrogen gas introduced during the reduction process, resulting in a mixture. The hydrogen flow rate was 5L / min. The first stage of reduction was carried out at 300℃ for 0.5h, the second stage at 500℃ for 1h, and the third stage at 650℃ for 1h, with a heating rate of 10℃ / min for each stage. The mixture was then sieved under a protective atmosphere to obtain activated alumina spheres and nano-tungsten powder. Testing revealed that the nano-tungsten powder had a purity of 99.99% and a specific surface area of ​​5.67 m². 2 / g, with an average particle size of 57nm.

[0031] Comparative Example 1 Unlike Example 1, the particle size of the activated alumina balls is 75 μm. When the mixture is sieved under a protective atmosphere, it is difficult to separate the activated alumina balls and tungsten powder due to the small particle size of the activated alumina balls.

[0032] Comparative Example 2 Unlike Example 1, no activated alumina balls were added; tungsten powder was obtained. Please see Figure 3 , Figure 3 The image shows the SEM image of the tungsten powder prepared in Comparative Example 2. It can be seen from the image that the tungsten powder has no impurity phase, but the particle size is uneven and agglomeration occurs.

[0033] Testing revealed that the tungsten powder had a purity of 99.99% and a specific surface area of ​​1.45 m². 2 / g, with an average particle size of 234nm.

[0034] Comparative Example 3 Unlike Example 1, the hydrogen reduction process only involves a single heating reduction at 650°C for 2.5 hours at a heating rate of 10°C / min and a hydrogen flow rate of 5 L / min. The mixture is then sieved under a protective atmosphere to obtain activated alumina balls and tungsten powder. Please see Figure 4 , Figure 4 The image shows the SEM image of the tungsten powder prepared in Comparative Example 3. It can be seen from the image that the tungsten powder has no impurity phase, but the particle size is uneven and agglomeration occurs.

[0035] Testing revealed that the tungsten powder had a purity of 99.99% and a specific surface area of ​​3.52 m². 2 / g, with an average particle size of 286nm.

[0036] Comparative Example 4 Unlike Example 1, the temperature of the third stage of heating and reduction was 800°C; the mixture was sieved under a protective atmosphere to obtain activated alumina balls and tungsten powder; Please see Figure 5 , Figure 5 The image shows the SEM image of the tungsten powder prepared in Comparative Example 4. As can be seen from the image, the tungsten particles are significantly coarsened. Since activated alumina will deactivate at temperatures above 700℃, it cannot adsorb water vapor or provide a large number of active sites, resulting in severe agglomeration of tungsten powder, uneven particle size, far deviating from the nanoscale range, and irregular particle morphology.

[0037] Testing revealed that the tungsten powder had a purity of 99.99% and a specific surface area of ​​2.98 m². 2 / g, with an average particle size of 194nm.

[0038] Comparative Example 5 Unlike Example 1, the particle size of the activated alumina balls is 8.5~10 mm; the mixture is sieved under a protective atmosphere to obtain activated alumina balls and tungsten powder; Please see Figure 6 , Figure 6 The image shows the SEM image of the tungsten powder prepared in Comparative Example 5. It can be seen from the image that the tungsten powder has no impurity phase, but the particle size is uneven and agglomeration occurs.

[0039] Testing revealed that the tungsten powder had a purity of 99.99% and a specific surface area of ​​2.78 m². 2 / g, with an average particle size of 92nm.

[0040] This invention utilizes the high water absorption capacity of activated alumina to efficiently adsorb water vapor generated within the system, cutting off the "gas migration-deposition coarsening" path at the source and significantly suppressing the Ostwald ripening effect, ensuring stable control of tungsten powder particle size at the nanoscale. Relying on the abundant porous structure and surface active sites of activated alumina, it provides a high-quality heterogeneous nucleation substrate for tungsten atoms—its surface defects lower the nucleation energy barrier, promoting high-density uniform nucleation. Furthermore, the porous structure physically blocks the contact and merging of nucleated tungsten particles, effectively reducing tungsten powder agglomeration and optimizing the microstructure (approaching spherical shape) and dispersibility. The process is highly compatible, requiring no major modifications to traditional hydrogen reduction equipment; it can be fine-tuned based on existing processes; raw material costs are controllable, resulting in good economic efficiency; the operation process is simple, and large-scale stable production is easily achieved.

[0041] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for preparing nano tungsten powder using activated alumina, characterized in that, The method comprises the following steps: S1, uniformly mixing tungsten oxide and active alumina balls in a mass ratio of 1:(1-2) to obtain a premix, wherein the active alumina balls have a particle size of 0.5-8 mm; S2, reducing the premix under a hydrogen atmosphere to obtain a mixture; S3, screening the mixture to obtain nano tungsten powder and active alumina balls.

2. The method for preparing nano-tungsten powder using active alumina according to claim 1, characterized in that, The step S1 specifically comprises uniformly mixing tungsten oxide and active alumina balls by a three-dimensional motion mixer to obtain a premix.

3. The method for preparing nano-tungsten powder using activated alumina according to claim 1, characterized in that, The step S2 specifically comprises placing the premix in a ceramic boat, placing the ceramic boat in a tube furnace, and reducing by introducing hydrogen to obtain a mixture.

4. The method for preparing nano-tungsten powder using activated alumina according to claim 1, characterized in that, In the step S2, the hydrogen flow rate of the hydrogen atmosphere is 3-5 L / min.

5. The method for preparing nano-tungsten powder using activated alumina according to claim 1, characterized in that, In the step S2, the temperature of the first-stage temperature rising reduction is 300-350℃, the temperature of the second-stage temperature rising reduction is 500-550℃, and the temperature of the third-stage temperature rising reduction is 650-700℃.

6. The method for preparing nano-tungsten powder using activated alumina according to claim 1, wherein the activated alumina is prepared by the method according to any one of claims 2 to 5. In the step S2, the temperature rising rate of the temperature rising reduction is 5-10℃ / min.

7. Nanosized tungsten powder, characterized in that, The nano tungsten powder is prepared by the method for preparing nano tungsten powder by using active alumina according to any one of claims 1-6.

8. The nano-tungsten powder of claim 7, wherein, The purity of the nano tungsten powder is greater than or equal to 99%.

9. The nano-tungsten powder of claim 7, wherein, The specific surface area of the nano-tungsten powder is greater than or equal to 4 m 2 / g.

10. The nano-tungsten powder of claim 7, wherein, The average particle size of the nano tungsten powder is 20-80 nm.

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