Superfine tungsten powder and preparation method thereof

Abstract

The invention belongs to the technical field of superfine tungsten powder, and particularly relates to superfine tungsten powder and a preparation method thereof.The preparation method includes the steps that an ammonium tungstate solution, hydrochloric acid and carbon black serve as raw materials to prepare a mixture of tungstic acid and a carbon precursor; calcining the tungstic acid and carbon precursor mixture in a nitrogen atmosphere to obtain a tungsten oxide and carbon mixture; a tungsten oxide and carbon mixture is calcined in an argon atmosphere, the argon atmosphere is kept for natural cooling, the superfine tungsten powder is obtained, the superfine tungsten powder is uniform in dispersion, complete in grain development, smooth in surface, free of pores and complex in morphology, the crystal structure of the superfine tungsten powder is a body-centered cube, the average particle size is smaller than or equal to 0.7 micrometer, and the specific surface area is smaller than or equal to 1.0 m < 2 > / g.

Description

Technical Field

[0001] The present invention belongs to the technical field of ultrafine tungsten powder, and specifically relates to an ultrafine tungsten powder and a preparation method thereof. More specifically, it relates to an ultrafine tungsten powder with good dispersibility and low specific surface area and a preparation method thereof. Background Art

[0002] As an extremely important refractory metal, tungsten plays an extremely important role in modern industry and is widely used in fields such as cemented carbide, high-temperature structural materials, and electronic materials. In recent years, with the development of high-end manufacturing, the domestic demand for ultrafine tungsten powder has been increasing continuously, and the industry has made great progress in the preparation technology of ultrafine tungsten powder.

[0003] Currently, the main method for industrial production of ultrafine tungsten powder is still the hydrogen reduction method of fine-grained tungsten oxide powder. This method is simple, stable and reliable, and has great cost advantages. However, it also has problems such as difficult particle size control and local particle agglomeration. At the same time, the ultrafine tungsten powder prepared by the hydrogen reduction method has characteristics such as complex surface morphology and high activity, which makes it extremely easy to agglomerate and the carbon distribution is uneven during the carbon addition process, and it is also easy to be oxidized during the carbon addition process, greatly increasing the difficulty of subsequent tungsten carbide production. Summary of the Invention

[0004] To solve the problems existing in the prior art, the main object of the present invention is to propose an ultrafine tungsten powder and a preparation method thereof.

[0005] According to one aspect of the present invention, the following technical solution is provided: A preparation method of an ultrafine tungsten powder, comprising the following steps: S1. Using ammonium tungstate solution, hydrochloric acid and carbon black as raw materials to prepare a mixture of tungstic acid and carbon precursor; S2. Calcining the mixture of tungstic acid and carbon precursor in a nitrogen atmosphere to obtain a mixture of tungsten oxide and carbon; S3. Calcining the mixture of tungsten oxide and carbon in an argon atmosphere, and allowing the argon atmosphere to cool naturally to obtain ultrafine tungsten powder.

[0006] As a preferred scheme of the preparation method of an ultrafine tungsten powder according to the present invention, wherein: in the step S1, carbon powder is uniformly dispersed in hydrochloric acid under ultrasonic stirring conditions, and then ammonium tungstate solution is dropped into hydrochloric acid, and after washing with pure water and drying, a mixture of tungstic acid and carbon precursor is obtained.

[0007] As a preferred scheme of the preparation method of an ultrafine tungsten powder according to the present invention, wherein: in the step S1, the concentration of hydrochloric acid is 13-19wt%.

[0008] As a preferred embodiment of the method for preparing ultrafine tungsten powder according to the present invention, wherein: in the step S2, the molar ratio of tungsten oxide to carbon in the tungsten oxide and carbon mixture is 1:3.

[0009] As a preferred embodiment of the method for preparing ultrafine tungsten powder according to the present invention, wherein: in the step S2, the calcination temperature is 550 - 650 °C, and the calcination time is 0.5 - 3 h.

[0010] As a preferred embodiment of the method for preparing ultrafine tungsten powder according to the present invention, wherein: in the step S3, the tungsten oxide and carbon mixture is calcined in a tubular furnace under an argon atmosphere.

[0011] As a preferred embodiment of the method for preparing ultrafine tungsten powder according to the present invention, wherein: in the step S3, argon with a flow rate of 1 - 4 L / min is introduced into the tubular furnace to provide an argon atmosphere.

[0012] As a preferred embodiment of the method for preparing ultrafine tungsten powder according to the present invention, wherein: in the step S3, the tungsten oxide and carbon mixture is heated in the furnace to the calcination temperature at a heating rate of 5 - 10 °C / min, the calcination temperature is 1100 - 1300 °C, and after reaching the calcination temperature, it is continuously calcined for 1 - 3 h.

[0013] According to another aspect of the present invention, the present invention provides the following technical solution: An ultrafine tungsten powder is prepared by using the above method for preparing ultrafine tungsten powder. The ultrafine tungsten powder is evenly dispersed, with complete grain development, a relatively smooth surface, no pores and complex morphologies. The crystal structure of the ultrafine tungsten powder is body-centered cubic, the average particle size is ≤ 0.7 μm, and the specific surface area is ≤ 1.0 m 2 / g.

[0014] The beneficial effects of the present invention are as follows: The present invention provides an ultrafine tungsten powder and a method for preparing the same. Ammonium tungstate solution, hydrochloric acid and carbon black are used as raw materials to prepare a tungsten acid and carbon precursor mixture; the tungsten acid and carbon precursor mixture is calcined in a nitrogen atmosphere to obtain a tungsten oxide and carbon mixture; the tungsten oxide and carbon mixture is calcined in an argon atmosphere, and the argon atmosphere is allowed to cool naturally to obtain ultrafine tungsten powder. The ultrafine tungsten powder is evenly dispersed, with complete grain development, a relatively smooth surface, no pores and complex morphologies. The crystal structure of the ultrafine tungsten powder is body-centered cubic, the average particle size is ≤ 0.7 μm, and the specific surface area is ≤ 1.0 m 2 / g. Description of the Drawings

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on the structures shown in these drawings.

[0016] Figure 1 SEM diagram of the tungsten powder prepared in Example 1 of the present invention; Figure 2 XRD diagram of the tungsten powder prepared in Example 1 of the present invention; Figure 3 SEM diagram of the tungsten powder prepared in Example 2 of the present invention; Figure 4 SEM diagram of the tungsten powder prepared in Example 3 of the present invention Figure 5 SEM diagram of the tungsten powder prepared in Comparative Example 1 of the present invention; Figure 6 XRD diagram of the tungsten powder prepared in Comparative Example 1 of the present invention; Figure 7 SEM diagram of the tungsten powder prepared in Comparative Example 2 of the present invention; Figure 8 XRD diagram of the tungsten powder prepared in Comparative Example 2 of the present invention; Figure 9 SEM diagram of the tungsten powder prepared in Comparative Example 3 of the present invention; Figure 10 SEM diagram of the tungsten powder prepared in Comparative Example 4 of the present invention; Figure 11 SEM diagram of the tungsten powder prepared in Comparative Example 5 of the present invention; Figure 12 XRD diagram of the tungsten powder prepared in Comparative Example 5 of the present invention; Figure 13 SEM diagram of the tungsten powder prepared in Comparative Example 6 of the present invention; Figure 14 XRD diagram of the tungsten powder prepared in Comparative Example 6 of the present invention.

[0017] The realization, functional features and advantages of the objectives of the present invention will be further described with reference to the embodiments and the accompanying drawings. Detailed Embodiments

[0018] The following will clearly and completely describe the technical solutions in the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0019] The present invention provides a method for preparing ultrafine tungsten powder. The prepared ultrafine tungsten powder is composed of ultrafine tungsten powder particles with a smooth surface, a low specific surface area, and a uniform distribution without agglomeration.

[0020] According to one aspect of the present invention, the following technical solution is provided: A method for preparing ultrafine tungsten powder, comprising the following steps: S1. Using ammonium tungstate solution, hydrochloric acid, and carbon black as raw materials to prepare a mixture of tungstic acid and carbon precursor; S2. Calcining the mixture of tungstic acid and carbon precursor in a nitrogen atmosphere to obtain a mixture of tungsten oxide and carbon; S3. Calcining the mixture of tungsten oxide and carbon in an argon atmosphere, and allowing the argon atmosphere to cool naturally to obtain ultrafine tungsten powder.

[0021] By using the active sites on the surface of carbon powder as the nucleation sites of tungstic acid, the combination of carbon and tungsten source can be made closer. At the same time, due to the small particle size of tungstic acid, the subsequent generated tungsten oxide is more likely to react with carbon powder to obtain ultrafine tungsten powder. Moreover, nano-tungstic acid is easy to gel in water, and the tungstic acid colloid can prevent the originally dispersed carbon powder from aggregating again during the processes of filtration and drying. Using carbon as a reducing agent to prepare tungsten powder can avoid the phenomenon of tungsten powder growth caused by the volatilization-deposition mechanism during hydrogen reduction.

[0022] Preferably, in the step S1, the carbon powder is uniformly dispersed in hydrochloric acid under ultrasonic stirring, and the stirring speed is 200 rpm; then the ammonium tungstate solution is dropped into the hydrochloric acid at a dropping speed of 50 mL / min, and after washing with pure water and drying, a mixture of tungstic acid and carbon precursor is obtained. More preferably, in the step S1, the concentration of hydrochloric acid is 13-19 wt%. Specifically, the concentration of hydrochloric acid can be any one of, for example, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt% or the range between any two of them.

[0023] Preferably, in the step S2, the molar ratio of tungsten oxide to carbon in the tungsten oxide and carbon mixture is 1:3. The calcination temperature is 550-650 °C, and the calcination time is 0.5-3 h. When WO3 and C are calcined under a protective gas, only CO is generated. Therefore, theoretically, the amount of C corresponding to the amount of WO3 in the raw material should be added to the raw material to carbonize WO3 into W. If there is too much C, WC or W2C will be generated, and if there is a lack, WO2 will remain. Nitrogen is used as the protective gas to prevent carbon from being oxidized. In the range of 550-650 °C, carbon does not undergo a carbothermal reduction reaction with tungsten oxide, and tungstic acid can be completely converted into monoclinic tungsten oxide. Specifically, the calcination temperature can be, for example, any one of 550 °C, 560 °C, 570 °C, 580 °C, 590 °C, 600 °C, 610 °C, 620 °C, 630 °C, 640 °C, 650 °C or the range between any two of them, and the calcination time can be, for example, any one of 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h or the range between any two of them.

[0024] Preferably, in the step S3, the tungsten oxide and carbon mixture is calcined in a tubular furnace under an argon atmosphere; the tubular furnace is passed with argon at a flow rate of 1-4 L / min to provide an argon atmosphere. If the gas flow rate is too large, it is easy to carry away part of the carbon, resulting in insufficient carbon and inability to completely reduce tungsten oxide into W powder; if the gas flow rate is small, it is easy for the generated CO to participate in the reaction to form rod-shaped tungsten. Specifically, the flow rate of argon can be, for example, any one of 1 L / min, 1.5 L / min, 2 L / min, 2.5 L / min, 3 L / min, 3.5 L / min, 4 L / min or the range between any two of them.

[0025] Preferably, in the step S3, the mixture of tungsten oxide and carbon is heated in the furnace at a heating rate of 5-10 °C / min to the calcination temperature, and the calcination temperature is 1100-1300 °C. After reaching the calcination temperature, it is continuously calcined for 1-3 h. The calcination temperature plays a decisive role in both the thermodynamics and kinetics of carbothermal reduction. On the one hand, it determines whether the carbothermal reduction of tungsten oxide by carbon can proceed, and on the other hand, it greatly affects the reaction rate of carbothermal reduction. That is, at too low a temperature, tungsten oxide does not react with carbon powder, and at too high a temperature, the particle size of tungsten powder will be too large to meet the requirements of ultrafine tungsten powder. If the calcination time is too short, the reaction between tungsten oxide powder and carbon is incomplete, resulting in too high carbon and oxygen contents in the product; if the calcination time is too long, the excessive growth of tungsten powder grains will occur. Specifically, the calcination temperature can be, for example, any one of 1100 °C, 1110 °C, 1120 °C, 1130 °C, 1140 °C, 1150 °C, 1160 °C, 1170 °C, 1180 °C, 1190 °C, 1200 °C, 1210 °C, 1220 °C, 1230 °C, 1240 °C, 1250 °C, 1260 °C, 1270 °C, 1280 °C, 1290 °C, 1300 °C or the range between any two of them. After reaching the calcination temperature, the continuous calcination time can be, for example, any one of 1 h, 1.5 h, 2 h, 2.5 h, 3 h or the range between any two of them.

[0026] According to another aspect of the present invention, the present invention provides the following technical solution: An ultrafine tungsten powder is prepared by using the above method for preparing ultrafine tungsten powder. The ultrafine tungsten powder is evenly dispersed, the grains are completely developed, the surface is relatively smooth, without pores and complex morphologies. The crystal structure of the ultrafine tungsten powder is body-centered cubic, the average particle size is ≤0.7 μm, and the specific surface area is ≤1.0 m 2 / g.

[0027] The technical solution of the present invention will be further described below in conjunction with specific embodiments.

[0028] Example 1 A method for preparing ultrafine tungsten powder includes the following steps: S1. The carbon powder is evenly dispersed in hydrochloric acid under ultrasonic stirring conditions, and then the ammonium tungstate solution with a concentration of 220 g / L is dropped into the hydrochloric acid. After washing with pure water and drying, a mixture of tungstic acid and carbon precursor is obtained; the concentration of hydrochloric acid is 16 wt%. S2. The mixture of tungstic acid and carbon precursor is calcined in a nitrogen atmosphere to obtain a mixture of tungsten oxide and carbon, wherein: the molar ratio of tungsten oxide to carbon is 1:3; the calcination temperature is 600 °C, and the calcination time is 1 h. S3. Calcinate the tungsten oxide and carbon mixture in a tube furnace under an argon atmosphere, and let it cool naturally while maintaining the argon atmosphere to obtain ultrafine tungsten powder; the tube furnace is filled with argon at a flow rate of 2 L / min to provide the argon atmosphere. Heat it up to the calcination temperature at a heating rate of 10 °C / min. The calcination temperature is 1200 °C. After reaching the calcination temperature, continue to calcine for 1 h.

[0029] The SEM image of the ultrafine tungsten powder obtained in this example is as Figure 1 shown, and the XRD image is as Figure 2 shown. It can be seen that the tungsten powder grains are completely developed, evenly dispersed, the surface is relatively smooth, without pores and complex morphologies; the specific surface area of the tungsten powder is 0.88 m 2 / g, the total carbon is 0.0063 wt%, the oxygen content is 0.290 wt%, and the average particle size is 0.540 μm.

[0030] Example 2 A method for preparing ultrafine tungsten powder, comprising the following steps: S1. Uniformly disperse carbon powder in hydrochloric acid under ultrasonic stirring conditions, and then drop a 190 g / L ammonium tungstate solution into the hydrochloric acid. After washing with pure water and drying, a tungsten acid and carbon precursor mixture is obtained; the hydrochloric acid concentration is 16 wt%; S2. Calcinate the tungsten acid and carbon precursor mixture in a nitrogen atmosphere to obtain a tungsten oxide and carbon mixture, wherein: the molar ratio of tungsten oxide to carbon is 1:3; the calcination temperature is 600 °C, and the calcination time is 1 h; S3. Calcinate the tungsten oxide and carbon mixture in a tube furnace under an argon atmosphere, and let it cool naturally while maintaining the argon atmosphere to obtain ultrafine tungsten powder; the tube furnace is filled with argon at a flow rate of 1 L / min to provide the argon atmosphere. Heat it up to the calcination temperature at a heating rate of 10 °C / min. The calcination temperature is 1100 °C. After reaching the calcination temperature, continue to calcine for 2 h.

[0031] The SEM image of the ultrafine tungsten powder obtained in this example is as Figure 3 shown. It can be seen that the tungsten powder grains are completely developed, evenly dispersed, the surface is relatively smooth, without pores and complex morphologies; the specific surface area of the tungsten powder is 0.98 m 2 / g, the total carbon is 0.0087 wt%, the oxygen content is 0.233 wt%, and the average particle size is 0.447 μm.

[0032] Example 3 A method for preparing ultrafine tungsten powder, comprising the following steps: S1. Uniformly disperse carbon powder in hydrochloric acid under ultrasonic stirring conditions, and then drop a 240 g / L ammonium tungstate solution into the hydrochloric acid. After washing with pure water and drying, a tungsten acid and carbon precursor mixture is obtained; the hydrochloric acid concentration is 16 wt%; S2. Calcinate the mixture of tungstic acid and carbon precursor in a nitrogen atmosphere to obtain a mixture of tungsten oxide and carbon, where: the molar ratio of tungsten oxide to carbon is 1:3; the calcination temperature is 600 °C, and the calcination time is 1 h; S3. Calcinate the mixture of tungsten oxide and carbon in a tubular furnace under an argon atmosphere, and let it cool naturally under the argon atmosphere to obtain ultrafine tungsten powder; the tubular furnace is filled with argon at a flow rate of 3 L / min to provide an argon atmosphere. Heat it up to the calcination temperature at a heating rate of 10 °C / min. The calcination temperature is 1300 °C. After reaching the calcination temperature, continue to calcinate for 1.5 h.

[0033] The SEM image of the ultrafine tungsten powder obtained in this example is as Figure 4 shown. It can be seen that the tungsten powder grains are completely developed, evenly dispersed, the surface is relatively smooth, without pores and complex morphologies; the specific surface area of the tungsten powder is 0.93 m 2 / g, the total carbon is 0.0047 wt%, the oxygen content is 0.172 wt%, and the average particle size is 0.674 μm.

[0034] Comparative Example 1 The difference from Example 1 is that in step S3, the calcination temperature is 800 °C.

[0035] The SEM image of the product obtained in this comparative example is as Figure 5 shown, and the XRD image is as Figure 6 shown. It can be seen that the product is still flaky tungsten oxide, and flaky carbon powder can be observed; the main component of the obtained product is β-tungsten oxide, the total carbon is 11.110 wt%, and the oxygen content is 17.37 wt%.

[0036] Comparative Example 2 The difference from Example 1 is that in step S3, the calcination temperature is 1400 °C.

[0037] The SEM image of the product obtained in this comparative example is as Figure 7 shown, and the XRD image is as Figure 8 shown. It can be seen that there are obviously abnormally developed and grown large grains in the product; the product is tungsten, the total carbon is 0.02 wt%, the oxygen content is 0.241 wt%, and the average particle size is 1.133 μm.

[0038] Comparative Example 3 The difference from Example 1 is that in step S3, the calcination duration is 4 h.

[0039] The SEM image of the product obtained in this comparative example is as Figure 9 shown. It can be seen that the total carbon of the obtained sample is 0.016%, and the oxygen content is 0.245%; the SEM image shows that there are obviously abnormally developed and grown large grains in the sample, and the average particle size is 1.026 μm.

[0040] Comparative Example 4 The difference from Example 1 is that in step S3, argon gas with a flow rate of 0.5 L / min is introduced into the tubular furnace to provide an argon atmosphere.

[0041] The SEM image of the product obtained in this comparative example is as Figure 10 shown. There are abnormally grown rod-shaped grains in the product. The total carbon content of the product is 0.016 wt%, and the oxygen content is 0.209 wt%.

[0042] Comparative Example 5 The difference from Example 1 is that in step S1, an ammonium tungstate solution with a concentration of 240 g / L is slowly dropped into hydrochloric acid with a concentration of 16 wt% to prepare tungstic acid. After the preparation of tungstic acid is completed, carbon powder is added, and the mixture is stirred evenly under ultrasonic conditions. After washing with pure water and drying, a mixture of tungstic acid and carbon precursor with a carbon content of 12.49 wt% is obtained.

[0043] The SEM image of the product obtained in this comparative example is as Figure 11 shown, and the XRD image is as Figure 12 shown. It can be seen that the grain size of the product is extremely uneven, with abnormally large particles; the total carbon is 0.940 wt%, and the oxygen content is 2.8 wt%, indicating that there is some incompletely reduced WO x .

[0044] Comparative Example 6 The difference from Example 1 is that in step S3, a hydrogen atmosphere is used instead of an argon atmosphere.

[0045] The SEM image of the product obtained in this comparative example is as Figure 13 shown, and the XRD image is as Figure 14 shown. It can be seen that the crystal particles in the product are relatively large, with a diameter of about 1 μm, and there is more residual carbon; there are three substances, WC, W2C, and W, in the product, and its total carbon is 5.64 wt%, and the free carbon is 2.31 wt%.

[0046] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structural transformation made using the content of the specification of the present invention under the inventive concept of the present invention, or direct / indirect application in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A method for preparing ultrafine tungsten powder, characterized in that, It includes the following steps: S1. Prepare a tungsten acid and carbon precursor mixture using ammonium tungstate solution, hydrochloric acid, and carbon black as raw materials; S2. Calcinate the tungsten acid and carbon precursor mixture in a nitrogen atmosphere to obtain a tungsten oxide and carbon mixture; S3. Calcinate the tungsten oxide and carbon mixture in an argon atmosphere, and keep the argon atmosphere cool naturally to obtain ultrafine tungsten powder.

2. The preparation method of the ultrafine tungsten powder according to claim 1, characterized in that, In step S1, the carbon powder is uniformly dispersed in hydrochloric acid under ultrasonic stirring conditions, and then the ammonium tungstate solution is dropped into the hydrochloric acid. After washing with pure water and drying, a tungsten acid and carbon precursor mixture is obtained.

3. The method for preparing ultrafine tungsten powder according to claim 1, characterized in that, In step S1, the concentration of hydrochloric acid is 13-19 wt%.

4. The method for preparing ultrafine tungsten powder according to claim 1, wherein In step S2, the molar ratio of tungsten oxide to carbon in the tungsten oxide and carbon mixture is 1:

3.

5. The method for preparing ultrafine tungsten powder according to claim 1, characterized in that, In step S2, the calcination temperature is 550-650 °C, and the calcination time is 0.5-3 h.

6. The method for preparing ultrafine tungsten powder according to claim 1, wherein In step S3, the tungsten oxide and carbon mixture is calcined in a tubular furnace under an argon atmosphere.

7. The method for preparing ultrafine tungsten powder according to claim 6, wherein In step S3, the tubular furnace is supplied with argon at a flow rate of 1-4 L / min to provide an argon atmosphere.

8. The method for preparing ultrafine tungsten powder according to claim 1, wherein In step S3, the temperature is raised to the calcination temperature at a heating rate of 5-10 °C / min. The calcination temperature is 1100-1300 °C. After reaching the calcination temperature, calcination is continued for 1-3 h.

9. An ultrafine tungsten powder, characterized in that, Prepared by the preparation method of ultrafine tungsten powder described in any one of claims 1-8, the ultrafine tungsten powder is uniformly dispersed and the crystal grains are completely developed.

10. The ultrafine tungsten powder according to claim 9, wherein The crystal structure of the ultrafine tungsten powder is body-centered cubic, with an average particle size of ≤ 0.7 μm and a specific surface area of ≤ 1.0 m 2 / g.

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