A high specific surface area and highly active tungsten powder and its preparation method

Abstract

This application belongs to the field of high-activity tungsten powder preparation technology, specifically relating to a high specific surface area, high-activity tungsten powder and its preparation method. The preparation method includes: adding dilute hydrochloric acid to an ammonium tungstate solution to adjust the pH to acidic, then adding hydrogen peroxide to obtain a mixed solution; vacuum drying the mixed solution to obtain a solid substance, wherein the vacuum drying temperature is ≤80℃; and reducing the solid substance in a hydrogen atmosphere to obtain high specific surface area, high-activity tungsten powder with a specific surface area ≥10m². 2 / g. This innovative technical solution utilizes the low-temperature heating and decomposition of ammonium chloride and peroxytungstic acid to produce a large amount of gas, forming a porous framework, thereby obtaining nano-tungsten powder with controllable particle size, good dispersibility, high specific surface area, and high activity; the performance of high specific surface area and high activity nano-tungsten powder can be easily controlled by controlling process conditions; thus increasing the application potential of nano-tungsten powder as a high-performance new tungsten material.

Description

Technical Field

[0001] This application belongs to the field of high-activity tungsten powder preparation technology, specifically a high specific surface area high-activity tungsten powder and its preparation method. Background Technology

[0002] High-quality ultrafine / nano-tungsten powder is a core raw material for preparing high-performance novel tungsten materials. Its key performance indicators, such as particle size distribution, purity, and microstructure, directly determine the quality and performance level of key products such as tungsten-based composite materials, cemented carbides, and ultrafine crystalline tungsten products. Traditional nano-tungsten powder preparation uses ammonium paratungstate (APT) or ammonium metatungstate (AMT) as precursors, obtaining tungsten powder through a three-step process of "calcination → primary reduction → secondary reduction." This route is mature and reliable, but it has two major bottlenecks. First, the primary particle size of the tungsten powder is coarse, resulting in a low specific surface area. Second, to increase the specific surface area, additional high-energy ball milling or spray pyrolysis is required, leading to a long process, high energy consumption, and easy introduction of impurities. Therefore, developing novel precursors with "self-contained pore-forming function" has become the key to breaking through technological constraints. These precursors can naturally form porous morphologies during the reduction process through their own crystal structure design, achieving high specific surface area without additional processes. This shortens the process and reduces energy consumption from the source, and fundamentally avoids the introduction of impurities, opening up a new path for the efficient and clean preparation of ultrafine / nano tungsten powder. Summary of the Invention

[0003] To address the aforementioned issues, this application provides a high specific surface area and high activity tungsten powder and its preparation method. The method first prepares a new precursor that has "self-contained pore-forming function," and then uses hydrogen reduction to prepare nano-tungsten powder with controllable particle size, good dispersibility, high specific surface area, and high activity.

[0004] According to a first aspect of this application, this application provides a method for preparing high specific surface area and high activity tungsten powder, comprising the following steps:

[0005] S1. Add dilute hydrochloric acid to the ammonium tungstate solution to adjust the pH to acidic, then add hydrogen peroxide to obtain a mixed solution;

[0006] S2. The mixed solution is vacuum dried to obtain a solid substance, wherein the vacuum drying temperature is ≤80℃;

[0007] S3. The solid material is reduced in a hydrogen atmosphere to obtain high specific surface area and high activity tungsten powder.

[0008] In the above technical solution, in step S1, adding dilute hydrochloric acid to adjust the pH to acidic will generate tungstate precipitate and create an acidic environment. Then, adding hydrogen peroxide reacts with the tungstate to generate peroxytungstate, causing the precipitate to gradually dissolve. Adding excess hydrogen peroxide ensures that the tungstate ions are completely converted to peroxytungstate ions. The mixed solution simultaneously contains peroxytungstate ions ([W₂O₃(O₂)₄)₄)2- ), chloride ions (Cl) - ), ammonium ions (NH4) + ) and hydrogen ions (H + The acidic environment in the mixed solution also inhibits the decomposition of peroxytungstate ions. Furthermore, peroxytungstate is easily decomposed at temperatures exceeding 80°C. To obtain solid peroxytungstate, in step S2, the mixed solution is placed in a vacuum environment, allowing it to evaporate to dryness at a lower boiling point, preventing the system temperature from becoming too high and thus inhibiting the decomposition of peroxytungstate. During the evaporation process, peroxytungstate crystals and ammonium chloride crystals precipitate. In step S3, the solid material is reduced in a hydrogen atmosphere. During the heating process, peroxytungstate decomposes to produce oxygen and tungstic acid, which is then dehydrated to obtain tungsten oxide. This process releases a large amount of gas, forming a porous framework. Ammonium chloride easily decomposes into ammonia and hydrogen chloride gas, leaving loose and porous tungsten oxide powder. The tungsten oxide is then reduced by hydrogen to obtain high-specific-surface-area, highly active tungsten powder.

[0009] Furthermore, in step S1, the molar ratio of hydrogen peroxide to WO3 in the ammonium tungstate solution is 1.2:1 to 2.0:1.

[0010] Furthermore, in step S1, dilute hydrochloric acid is added to the ammonium tungstate solution to adjust the pH to 1-2.

[0011] Furthermore, in step S1, the mixed solution includes peroxytungstic acid.

[0012] Furthermore, in step S2, ethanol is added to the mixed solution and then vacuum dried, wherein the volume ratio of ethanol to the mixed solution is 1:9 to 3:7.

[0013] Adding ethanol can further reduce the drying temperature of the mixed solution and accelerate the evaporation rate, thus allowing the system to be dried at a lower temperature.

[0014] Furthermore, in step S2, the temperature of the vacuum drying is 70~80℃.

[0015] Furthermore, in step S3, the flow rate of hydrogen in the hydrogen atmosphere is 3~5 L / min.

[0016] Furthermore, in step S3, the solid material is heated to 650~1100℃ for reduction;

[0017] If the temperature is too low, tungsten cannot be fully reduced into tungsten powder; if the temperature is too high, the tungsten powder will sinter, resulting in a lower specific surface area.

[0018] Further, step S3 specifically involves: heating the solid material to 300~350℃ and holding it at that temperature for 0.5~1h in a hydrogen atmosphere, then heating it to 500~550℃ and holding it at that temperature for 1~3h, and finally heating it to 650~1100℃ and holding it at that temperature for 1~3h to reduce it, thereby obtaining high specific surface area and high activity tungsten powder.

[0019] Heating to 300-350℃ and holding it at that temperature allows the decomposition reaction of peroxytungstic acid and ammonium chloride to proceed fully, and the resulting tungsten oxide begins to be initially reduced. Holding at 500-550℃ reduces the tungsten oxide to a lower valence tungsten oxide. Finally, heating to 650-1100℃ further reduces the tungsten oxide to obtain tungsten powder. At the same time, by controlling the heating rate and reducing in stages, the sintering and agglomeration of tungsten oxide caused by excessively high local temperatures can be avoided. It also allows for precise control of the grain growth rate of tungsten powder, resulting in high specific surface area and high activity nano-tungsten powder.

[0020] According to a second aspect of this application, this application provides a high specific surface area and high activity tungsten powder, which is prepared by any of the above-described methods for preparing high specific surface area and high activity tungsten powder.

[0021] Furthermore, the specific surface area of ​​the high-specific-surface-area, highly active tungsten powder is ≥10 m². 2 / g, porosity ≥0.850.

[0022] Furthermore, the high specific surface area and high activity tungsten powder has a Fisher particle size of 0.70~2.0μm;

[0023] Because nano-tungsten powder can agglomerate, small particles can cluster into large particles, causing its Fisher particle size to deviate from the nanoscale.

[0024] This application proposes a high specific surface area and high activity tungsten powder and its preparation method, which produces the following beneficial effects: It innovatively utilizes the low-temperature heating and decomposition of ammonium chloride and peroxytungstic acid to produce a large amount of gas to form a porous framework, thereby obtaining nano-tungsten powder with controllable particle size, good dispersibility, high specific surface area, and high activity; it can easily control the performance of high specific surface area and high activity nano-tungsten powder by controlling the process conditions; and it increases the application potential of nano-tungsten powder as a high-performance new tungsten material. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of this application 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 this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0026] Figure 1SEM image of the high specific surface area and high activity tungsten powder prepared in Example 1;

[0027] Figure 2 SEM image of the high specific surface area and high activity tungsten powder prepared in Example 2;

[0028] Figure 3 SEM image of the high specific surface area and high activity tungsten powder prepared in Example 3;

[0029] Figure 4 SEM image of the high specific surface area and high activity tungsten powder prepared in Example 4;

[0030] Figure 5 SEM image of the high specific surface area and high activity tungsten powder prepared in Example 5;

[0031] Figure 6 SEM image of the tungsten powder prepared in Comparative Example 1;

[0032] Figure 7 SEM image of the tungsten powder prepared in Comparative Example 2;

[0033] Figure 8 The image shows a SEM image of the tungsten powder prepared in Comparative Example 3.

[0034] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0035] The technical solutions in the embodiments will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0036] According to a first aspect of this application, this application provides a method for preparing high specific surface area and high activity tungsten powder, comprising the following steps:

[0037] S1. Add dilute hydrochloric acid to the ammonium tungstate solution to adjust the pH to acidic, then add hydrogen peroxide to obtain a mixed solution;

[0038] Preferably, dilute hydrochloric acid is added to the ammonium tungstate solution to adjust the pH to 1-2, the molar ratio of hydrogen peroxide to WO3 in the ammonium tungstate solution is 1.2:1-2.0:1, and the mixed solution includes peroxytungstic acid.

[0039] Specifically, dilute hydrochloric acid is added to the ammonium tungstate solution to adjust the pH to any one or any two of 1, 1.2, 1.4, 1.6, 1.8, and 2. The molar ratio of hydrogen peroxide to WO3 in the ammonium tungstate solution can be any one or any two of 1.2:1, 1.4:1, 1.6:1, 1.8:1, and 2.0:1.

[0040] S2. Vacuum dry the mixed solution to obtain a solid substance. The vacuum drying temperature is ≤80℃.

[0041] Preferably, ethanol is added to the mixed solution, and then vacuum drying is performed at a temperature of 70~80°C, with the volume ratio of ethanol to the mixed solution being 1:9~3:7.

[0042] Specifically, the vacuum drying temperature can be any one of 70℃, 72℃, 74℃, 76℃, 78℃, or 80℃, or any two of these ranges, and the volume ratio of ethanol to the mixed solution can be any one of 1:9, 3:22, 3:17, 1:4, or 3:7, or any two of these ranges.

[0043] S3. In a hydrogen atmosphere, the solid material is reduced to obtain tungsten powder with high specific surface area and high activity.

[0044] Preferably, the flow rate of hydrogen is controlled at 3~5L / min, and the solid material is heated to 650~1100℃ for reduction to obtain high specific surface area and high activity tungsten powder;

[0045] More preferably, the flow rate of hydrogen is controlled at 3~5L / min, the solid material is heated to 300~350℃ and held for 0.5~1h, then heated to 500~550℃ and held for 1~3h, and finally heated to 650~1100℃ and held for 1~3h for reduction to obtain high specific surface area and high activity tungsten powder.

[0046] Specifically, the flow rate of hydrogen is controlled at 3L / min, 3.5L / min, 4L / min, 4.5L / min, and 5L / min. The solid material is heated to any one or any two of 300℃, 310℃, 320℃, 330℃, 340℃, and 350℃ and held for 0.5~1h. Then, the temperature is raised to any one or any two of 500℃, 510℃, 520℃, 530℃, 540℃, and 550℃ and held for 1~3h. Finally, the temperature is raised to any one or any two of 650℃, 700℃, 800℃, 900℃, 1000℃, and 1100℃ and held for 1~3h for reduction to obtain high specific surface area and high activity tungsten powder.

[0047] According to a second aspect of this application, this application provides a high specific surface area and high activity tungsten powder, which is prepared by any of the above-described methods for preparing high specific surface area and high activity tungsten powder.

[0048] Preferably, the high specific surface area and high activity tungsten powder has a specific surface area ≥ 10 m². 2 / g, porosity ≥0.850.

[0049] Preferably, the high specific surface area and high activity tungsten powder has a Fisher particle size of 0.70~2.0μm.

[0050] The technical solution of this application will be further described below with reference to specific embodiments.

[0051] Example 1

[0052] A method for preparing high specific surface area and high activity tungsten powder includes the following steps:

[0053] S1. Place the ammonium tungstate solution in a water-water stirring vessel, add dilute hydrochloric acid to adjust the pH to 1.5, and then add hydrogen peroxide to obtain a mixed solution, wherein the molar ratio of hydrogen peroxide to WO3 in the ammonium tungstate solution is 1.2:1.

[0054] S2. Add ethanol to the mixed solution, then place it in a vacuum oven and dry it under vacuum at 70°C. The volume ratio of ethanol to the mixed solution is 3:7, and a solid substance is obtained.

[0055] S3. Place the solid material in a tube furnace, control the hydrogen flow rate at 3 L / min, heat the solid material to 300℃ and hold for 0.5 h, then heat to 500℃ and hold for 1 h, and finally heat to 650℃ and hold for 1 h for reduction, obtaining a specific surface area of ​​26.57 m². 2 High specific surface area and high activity tungsten powder with a porosity of 0.890 and a Fisher particle size of 1.51μm / g;

[0056] The SEM image of the high specific surface area and high activity tungsten powder prepared in this embodiment is shown below. Figure 1 As shown.

[0057] Example 2

[0058] A method for preparing high specific surface area and high activity tungsten powder includes the following steps:

[0059] S1. Place the ammonium tungstate solution in a water-water stirring vessel, add dilute hydrochloric acid to adjust the pH to 1.0, and then add hydrogen peroxide to obtain a mixed solution, wherein the molar ratio of hydrogen peroxide to WO3 in the ammonium tungstate solution is 1.5:1.

[0060] S2. Add ethanol to the mixed solution, then place it in a vacuum oven and dry it under vacuum at 80°C. The volume ratio of ethanol to the mixed solution is 1:4, and a solid substance is obtained.

[0061] S3. Place the solid material in a tube furnace, control the hydrogen flow rate at 5 L / min, heat the solid material to 350℃ and hold for 1 hour, then heat to 550℃ and hold for 3 hours, and finally heat to 900℃ and hold for 3 hours for reduction, obtaining a specific surface area of ​​20.06 m². 2 High-specific-surface-area, highly active tungsten powder with a porosity of 0.855 and a Fisher particle size of 1.12 μm;

[0062] The SEM image of the high specific surface area and high activity tungsten powder prepared in this embodiment is shown below. Figure 2 As shown.

[0063] Example 3

[0064] A method for preparing high specific surface area and high activity tungsten powder includes the following steps:

[0065] S1. Place the ammonium tungstate solution in a water-based stirring vessel, add dilute hydrochloric acid to adjust the pH to 2.0, and then add hydrogen peroxide to obtain a mixed solution, wherein the molar ratio of hydrogen peroxide to WO3 in the ammonium tungstate solution is 2.0:1.

[0066] S2. Add ethanol to the mixed solution, then place it in a vacuum oven and dry it under vacuum at 80°C. The volume ratio of ethanol to the mixed solution is 1:9, and a solid substance is obtained.

[0067] S3. Place the solid material in a tube furnace, control the hydrogen flow rate at 4 L / min, heat the solid material to 300℃ and hold for 0.5 h, then heat to 500℃ and hold for 2 h, and finally heat to 850℃ and hold for 2 h for reduction, obtaining a specific surface area of ​​22.83 m². 2 High-specific-surface-area, highly active tungsten powder with a porosity of 0.872 and a Fisher particle size of 1.28 μm;

[0068] The SEM image of the high specific surface area and high activity tungsten powder prepared in this embodiment is shown below. Figure 3 As shown.

[0069] Example 4

[0070] A method for preparing high specific surface area and high activity tungsten powder includes the following steps:

[0071] S1. Place the ammonium tungstate solution in a water-water stirring vessel, add dilute hydrochloric acid to adjust the pH to 1.5, and then add hydrogen peroxide to obtain a mixed solution, wherein the molar ratio of hydrogen peroxide to WO3 in the ammonium tungstate solution is 1.2:1.

[0072] S2. Add ethanol to the mixed solution, then place it in a vacuum oven and dry it under vacuum at 70°C. The volume ratio of ethanol to the mixed solution is 3:7, and a solid substance is obtained.

[0073] S3. Place the solid material in a tube furnace, control the hydrogen flow rate at 3 L / min, heat the solid material to 300℃ and hold for 0.5 h, then heat to 500℃ and hold for 1 h, and finally heat to 1200℃ and hold for 1 h for reduction, obtaining a specific surface area of ​​13.13 m². 2 High specific surface area and high activity tungsten powder with a porosity of 0.831 and a Fisher particle size of 0.93μm / g;

[0074] The SEM image of the high specific surface area and high activity tungsten powder prepared in this embodiment is shown below. Figure 4 As shown.

[0075] Example 5

[0076] A method for preparing high specific surface area and high activity tungsten powder includes the following steps:

[0077] S1. Place the ammonium tungstate solution in a water-based stirring vessel, add dilute hydrochloric acid to adjust the pH to 1.7, and then add hydrogen peroxide to obtain a mixed solution, wherein the molar ratio of hydrogen peroxide to WO3 in the ammonium tungstate solution is 1.5:1.

[0078] S2. Place the mixed solution in a vacuum oven and dry it under vacuum at 80°C to obtain a solid substance;

[0079] S3. Place the solid material in a tube furnace, control the hydrogen flow rate at 3 L / min, heat the solid material to 350℃ and hold for 1 hour, then heat to 550℃ and hold for 3 hours, and finally heat to 900℃ and hold for 3 hours for reduction, obtaining a specific surface area of ​​16.73 m². 2 High-specific-surface-area, highly active tungsten powder with a porosity of 0.868 and a Fisher particle size of 1.27 μm.

[0080] The SEM image of the high specific surface area and high activity tungsten powder prepared in this embodiment is shown below. Figure 5 As shown.

[0081] Comparative Example 1

[0082] The only difference between this comparative example and Example 2 is that in step S1, dilute hydrochloric acid is not added to adjust the pH, and hydrogen peroxide is directly added to the ammonium tungstate solution.

[0083] The specific surface area of ​​the obtained tungsten powder was 2.57 m². 2 / g, porosity 0.783, Fisher particle size 1.41μm; its SEM image is as follows. Figure 6 As shown.

[0084] Comparative Example 2

[0085] The only difference between this comparative example and Example 2 is that hydrogen peroxide is not added after adjusting the pH of the ammonium tungstate solution with dilute hydrochloric acid in step S1.

[0086] The specific surface area of ​​the obtained tungsten powder was 1.15 m². 2 / g, porosity 0.752, Fisher particle size 1.56μm; its SEM image is as follows. Figure 7 As shown.

[0087] Comparative Example 3

[0088] The only difference between this comparative example and Example 3 is that in step S2, ethanol is added to the mixed solution and then placed in an oven to dry at a temperature of 110°C.

[0089] The specific surface area of ​​the obtained tungsten powder was 6.84 m². 2 / g, porosity 0.836, Fisher particle size 1.43μm; its SEM image is as follows. Figure 8 As shown.

[0090] This application proposes a high specific surface area and high activity tungsten powder and its preparation method, which produces the following beneficial effects: It innovatively utilizes the low-temperature heating and decomposition of ammonium chloride and peroxytungstic acid to produce a large amount of gas to form a porous framework, thereby obtaining nano-tungsten powder with controllable particle size, good dispersibility, high specific surface area, and high activity; it can easily control the performance of high specific surface area and high activity nano-tungsten powder by controlling the process conditions; and it increases the application potential of nano-tungsten powder as a high-performance new tungsten material.

[0091] The above description is only a preferred embodiment of this application and does not limit the patent scope of this application. All equivalent structural transformations made using the content of this application's specification under the inventive concept of this application, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. A method for producing high specific surface area high activity tungsten powder, characterized by, The method comprises the following steps: S1, adding dilute hydrochloric acid to an ammonium tungstate solution to adjust the pH to be acidic, and then adding hydrogen peroxide to obtain a mixed solution; S2, vacuum drying the mixed solution to obtain a solid substance, wherein the temperature of the vacuum drying is ≤80℃; S3, reducing the solid substance in a hydrogen atmosphere to obtain high specific surface area high activity tungsten powder.

2. The method for preparing high specific surface area and high activity tungsten powder according to claim 1, characterized in that, In the step S1, the molar ratio of the hydrogen peroxide to WO3 in the ammonium tungstate solution is 1.2:1-2.0:

1.

3. The method for preparing high specific surface area and high activity tungsten powder according to claim 1, characterized in that, In the step S1, the dilute hydrochloric acid is added to the ammonium tungstate solution to adjust the pH to 1-2.

4. The method for preparing high specific surface area and high activity tungsten powder according to claim 1, characterized in that, In the step S1, the mixed solution comprises peroxotungstic acid.

5. The method for preparing high specific surface area and high activity tungsten powder according to claim 1, characterized in that, In the step S2, ethanol is added to the mixed solution before vacuum drying, and the volume ratio of the ethanol to the mixed solution is 1:9-3:

7.

6. The method for preparing high specific surface area and high activity tungsten powder according to claim 1, characterized in that, In the step S3, the flow rate of hydrogen in the hydrogen atmosphere is 3-5 L / min.

7. The method for preparing high specific surface area and high activity tungsten powder according to claim 1, characterized in that, In the step S3, the solid substance is heated to 650-1100℃ for reduction.

8. The method for preparing high specific surface area and high activity tungsten powder according to claim 7, characterized in that, In the step S3, the solid substance is heated to 300-350℃ in the hydrogen atmosphere and kept for 0.5-1 h, then heated to 500-550℃ and kept for 1-3 h, and finally heated to 650-1100℃ and kept for 1-3 h for reduction to obtain high specific surface area high activity tungsten powder.

9. A high specific surface area high activity tungsten powder characterized in that, The high specific surface area high activity tungsten powder is prepared by the method according to any one of claims 1-8.

10. The high surface area high activity tungsten powder of claim 9, wherein, a specific surface area of > 10 m 2 / g, a porosity of > 0.850.

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