Tungsten powder with high specific surface area and high activity and preparation method thereof

Abstract

The invention belongs to the technical field of high-activity tungsten powder preparation, and particularly relates to high-specific-surface-area high-activity tungsten powder and a preparation method thereof.The preparation method comprises the steps that diluted hydrochloric acid is added into an ammonium tungstate solution to adjust the pH to be acidic, then hydrogen peroxide is added, and a mixed solution is obtained; carrying out vacuum drying on the mixed solution at the temperature of less than or equal to 80 DEG C to obtain a solid substance; and in the hydrogen atmosphere, the solid matter is reduced, the tungsten powder with the high specific surface area and the high activity is obtained, and the specific surface area is larger than or equal to 10 m < 2 > / g. According to the technical scheme, ammonium chloride and peroxotungstic acid are creatively applied to be subjected to low-temperature heating decomposition to generate a large amount of gas to form a porous framework, and therefore the nano tungsten powder controllable in granularity, good in dispersity, high in specific surface area and high in activity is prepared; the performance of the high-specific-surface-area and high-activity nano tungsten powder can be controlled by simply controlling process conditions; and the application potential of the nano tungsten powder as a novel high-performance tungsten material is increased.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high-activity tungsten powder preparation, and particularly relates to high-specific-surface-area high-activity tungsten powder and a preparation method thereof. BACKGROUND

[0002] As a core basic raw material for preparing high-performance new tungsten materials, high-quality ultrafine / nano tungsten powder directly determines the quality and performance level of key products such as tungsten-based composite materials, hard alloys, and ultrafine-grain tungsten products, in terms of particle size distribution, purity, and microstructure, and the like. Traditional nano-tungsten powder preparation takes ammonium paratungstate (APT) or ammonium metatungstate (AMT) as a precursor, and obtains tungsten powder through three steps of "calcination → primary reduction → secondary reduction". This route is mature and reliable, but has two major bottlenecks. One is that the primary particle size of tungsten powder is coarse and the specific surface area is low, and the other is that high-energy ball milling or spray pyrolysis needs to be added to improve the specific surface area, which has a long process, high energy consumption, and is easy to introduce impurities. Therefore, developing a new type of precursor with "self-pore-forming function" has become the key to breaking through the technical shackles - such a precursor can naturally form a porous morphology in the reduction process through its own crystal structure design, without the need for additional processes to achieve high specific surface area, thus shortening the process and reducing energy consumption from the source, and fundamentally avoiding the introduction of impurities, opening up a new path for efficient and clean preparation of ultrafine / nano tungsten powder. SUMMARY

[0003] In view of the above problems, the application provides high-specific-surface-area high-activity tungsten powder and a preparation method thereof. The method first prepares a new precursor with "self-pore-forming function", and then uses hydrogen reduction to prepare nano-tungsten powder with controllable particle size, good dispersity, high specific surface area, and high activity.

[0004] According to a first aspect of the application, the application provides a preparation method of high-specific-surface-area high-activity tungsten powder, comprising 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.

[0005] In the above technical solution, in step S1, the addition of dilute hydrochloric acid to adjust the pH to be acidic generates tungstic acid precipitate, while creating an acidic environment, and then the addition of hydrogen peroxide can react with tungstic acid to generate peroxotungstic acid, so that the precipitate gradually dissolves. The complete conversion of tungstate into peroxotungstate can be ensured by adding excess hydrogen peroxide, and the mixed solution simultaneously contains peroxotungstate ions ([W2O3(O2)4] 2- ), chloride ions (Cl -hydroxide ions (OH ), ammonium ions (NH4 + ) and hydrogen ions (H + ). The acidic environment of the mixed solution can also inhibit the decomposition of peroxotungstate. In addition, peroxotungstate is prone to decomposition when the temperature exceeds 80℃. In order to obtain peroxotungstate solid, the mixed solution is placed in a vacuum environment in step S2, so that the mixed solution is evaporated at a lower boiling point, and the temperature of the system is not too high, thereby inhibiting the decomposition of peroxotungstate. During the evaporation of the solution, peroxotungstate crystals and ammonium chloride crystals are precipitated. In step S3, the solid substance is reduced in a hydrogen atmosphere. During the heating process, peroxotungstate will decompose to generate oxygen and tungstate, and then dehydrate to obtain tungsten oxide. A large amount of gas is released during this process, forming a porous framework. Ammonium chloride is prone to decomposition into ammonia and hydrogen chloride gas, leaving behind a loose and porous tungsten oxide powder. The tungsten oxide is then reduced by hydrogen to obtain high specific surface area and high activity tungsten powder.

[0006] Further, in step S1, the molar ratio of hydrogen peroxide to WO3 in the ammonium tungstate solution is 1.2:1 to 2.0:1.

[0007] Further, in step S1, dilute hydrochloric acid is added to the ammonium tungstate solution to adjust the pH to 1 to 2.

[0008] Further, in step S1, the mixed solution includes peroxotungstate.

[0009] Further, in step S2, ethanol is added to the mixed solution, and then vacuum drying is performed. The volume ratio of the ethanol to the mixed solution is 1:9 to 3:7. The addition of ethanol can further reduce the drying temperature of the mixed solution and accelerate the evaporation speed, so that the system can be dried at a lower temperature.

[0010] Further, in step S2, the temperature of the vacuum drying is 70 to 80℃.

[0011] Further, in step S3, the flow rate of hydrogen in the hydrogen atmosphere is 3 to 5 L / min.

[0012] Further, in step S3, the solid substance is heated to 650 to 1100℃ for reduction. If the temperature is too low, the tungsten element cannot be fully reduced to tungsten powder. If the temperature is too high, the tungsten powder will sinter, resulting in a lower specific surface area.

[0013] Further, the step S3 is specifically: heating the solid substance to 300-350℃ in a hydrogen atmosphere and keeping for 0.5-1h, then heating to 500-550℃ and keeping for 1-3h, and finally heating to 650-1100℃ and keeping for 1-3h for reduction, to obtain high specific surface area high activity tungsten powder; The heating to 300-350℃ can make the decomposition reaction of tungsten peroxide acid and ammonium chloride fully proceed, and the obtained tungsten oxide is initially reduced; the keeping at 500-550℃ can reduce the tungsten oxide to low-valence tungsten oxide, and finally heating to 650-1100℃ can deeply reduce the tungsten oxide to obtain tungsten powder; at the same time, by controlling the heating rate to reduce in stages, the local temperature too high to cause the tungsten oxide to sinter and agglomerate can be avoided, and the grain growth rate of the tungsten powder can be precisely controlled to obtain high specific surface area high activity nano tungsten powder.

[0014] According to a second aspect of the present application, the present application provides a high specific surface area high activity tungsten powder, which is prepared by any one of the above preparation methods of high specific surface area high activity tungsten powder.

[0015] Further, the specific surface area of the high specific surface area high activity tungsten powder is ≥10m 2 / g, and the porosity is ≥0.850.

[0016] Further, the Fisher particle size of the high specific surface area high activity tungsten powder is 0.70-2.0μm; Because the nano tungsten powder will appear agglomeration phenomenon, small particles are aggregated into large particles, so that the Fisher particle size deviates from the nanometer level.

[0017] The present application proposes a high specific surface area high activity tungsten powder and a preparation method thereof, which has the following beneficial effects: the present application innovatively uses ammonium chloride and tungsten peroxide acid to produce a large amount of gas by low-temperature heating and decomposition to form a porous skeleton, so as to prepare nano tungsten powder with controllable particle size, good dispersibility, high specific surface area and high activity; the performance of the high specific surface area high activity nano tungsten powder can be simply controlled by controlling the process conditions; and the application potential of the nano tungsten powder as a high-performance new tungsten material is increased. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the drawings shown.

[0019] Figure 1 SEM image of high specific surface area high activity tungsten powder prepared for Example 1; Figure 2 SEM image of high specific surface area high activity tungsten powder prepared for Example 2; Figure 3 SEM image of high specific surface area high activity tungsten powder prepared for Example 3; Figure 4 SEM image of high specific surface area high activity tungsten powder prepared for Example 4; Figure 5 SEM image of high specific surface area high activity tungsten powder prepared for Example 5; Figure 6 SEM image of tungsten powder prepared for Comparative Example 1; Figure 7 SEM image of tungsten powder prepared for Comparative Example 2; Figure 8 SEM image of tungsten powder prepared for Comparative Example 3.

[0020] The implementation, functional features and advantages of the present application will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0022] According to a first aspect of the present application, the present application provides a preparation method of high specific surface area high activity tungsten powder, comprising 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; 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 comprises peroxotungstate.

[0023] Specifically, dilute hydrochloric acid is added to the ammonium tungstate solution to adjust the pH to any one of 1, 1.2, 1.4, 1.6, 1.8, 2 or a range between any two of them, and the molar ratio of hydrogen peroxide to WO3 in the ammonium tungstate solution can be any one of 1.2:1, 1.4:1, 1.6:1, 1.8:1, 2.0:1 or a range between any two of them.

[0024] S2, vacuum drying the mixed solution to obtain a solid substance, the temperature of vacuum drying being ≤80℃; 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. 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.

[0025] S3. In a hydrogen atmosphere, the solid material is reduced to obtain tungsten powder with high specific surface area and high activity. 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; 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. 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. 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.

[0026] Preferably, the high specific surface area and high activity tungsten powder has a specific surface area ≥ 10 m². 2 / g, porosity ≥0.850.

[0027] Preferably, the high specific surface area and high activity tungsten powder has a Fisher particle size of 0.70~2.0μm.

[0028] The technical solution of this application will be further described below with reference to specific embodiments.

[0029] Example 1 A method for preparing high specific surface area and high activity tungsten powder includes the following steps: 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. 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. 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; 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.

[0030] Example 2 A method for preparing high specific surface area and high activity tungsten powder includes the following steps: 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. 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. 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; 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.

[0031] Example 3 A method for preparing high specific surface area and high activity tungsten powder includes the following steps: 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. 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. 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; 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.

[0032] Example 4 A method for preparing high specific surface area and high activity tungsten powder includes the following steps: 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. 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. 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; 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.

[0033] Example 5 A method for preparing high specific surface area and high activity tungsten powder includes the following steps: 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. S2. Place the mixed solution in a vacuum oven and dry it under vacuum at 80°C to obtain a solid substance; 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.

[0034] 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.

[0035] Comparative Example 1 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. 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.

[0036] Comparative Example 2 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. 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.

[0037] Comparative Example 3 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. 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.

[0038] 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.

[0039] 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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