Ultrafine tungsten powder and method for producing the same

Abstract

The application belongs to the technical field of superfine tungsten powder and specifically relates to a superfine tungsten powder and a preparation method thereof, wherein ammonium tungstate solution, hydrochloric acid and carbon black are used as raw materials to prepare a tungstic acid and carbon precursor mixture; the tungstic 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 natural cooling is maintained in the argon atmosphere to obtain the superfine tungsten powder, which is uniformly dispersed, has complete grain development, a relatively smooth surface, no pores and complex morphology, and a body-centered cubic crystal structure, and has an average particle size of less than or equal to 0.7 microns and a specific surface area of less than or equal to 1.0 m 2 / g.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ultra-fine tungsten powder, and particularly relates to an ultra-fine tungsten powder and a preparation method thereof. BACKGROUND

[0002] Tungsten, as an extremely important refractory metal, has an extremely important position in modern industry and is widely used in the fields of hard alloy, high-temperature structural material and electronic material. In recent years, with the development of high-end manufacturing industry, the demand for ultra-fine tungsten powder in China is increasing, and the preparation technology of ultra-fine tungsten powder has made great progress.

[0003] At present, the main method for industrial production of ultra-fine tungsten powder is still the hydrogen reduction method of fine tungsten oxide powder, which is simple, stable and reliable, and has great cost advantage, but also has problems such as difficult control of particle size and local agglomeration of particles. At the same time, the ultra-fine tungsten powder prepared by the hydrogen reduction method has the characteristics of complex surface morphology and high activity, which makes the ultra-fine tungsten powder easy to agglomerate during carbon preparation, resulting in uneven carbon preparation, and easy to be oxidized during carbon preparation, greatly increasing the difficulty of subsequent tungsten carbide production. SUMMARY

[0004] In order to solve the problems existing in the prior art, the main purpose of the present application is to provide an ultra-fine tungsten powder and a preparation method thereof.

[0005] According to one aspect of the present application, the present application provides the following technical scheme:

[0006] A preparation method of an ultra-fine tungsten powder, comprising the following steps:

[0007] S1, using ammonium tungstate solution, hydrochloric acid and carbon black as raw materials to prepare a tungstic acid and carbon precursor mixture;

[0008] S2, calcining the tungstic acid and carbon precursor mixture in a nitrogen atmosphere to obtain a tungsten oxide and carbon mixture;

[0009] S3, calcining the tungsten oxide and carbon mixture in an argon atmosphere, and naturally cooling the argon atmosphere to obtain the ultra-fine tungsten powder.

[0010] As a preferred scheme of the preparation method of the ultra-fine tungsten powder, in the step S1, the carbon powder is uniformly dispersed in the hydrochloric acid under ultrasonic stirring, and then the ammonium tungstate solution is dropped into the hydrochloric acid, and the tungstic acid and carbon precursor mixture is obtained after washing with pure water and drying.

[0011] As a preferred scheme of the preparation method of the ultra-fine tungsten powder, in the step S1, the concentration of the hydrochloric acid is 13-19wt%.

[0012] As a preferred scheme of the preparation method of the superfine tungsten powder, in the step S2, the molar ratio of tungsten oxide to carbon in the tungsten oxide and carbon mixture is 1:3.

[0013] As a preferred scheme of the preparation method of the superfine tungsten powder, in the step S2, the calcination temperature is 550-650℃, and the calcination time is 0.5-3h.

[0014] As a preferred scheme of the preparation method of the superfine tungsten powder, in the step S3, the tungsten oxide and carbon mixture is calcined in a tube furnace in an argon atmosphere.

[0015] As a preferred scheme of the preparation method of the superfine tungsten powder, in the step S3, the tube furnace is supplied with argon gas at a flow rate of 1-4L / min to provide the argon atmosphere.

[0016] As a preferred scheme of the preparation method of the superfine tungsten powder, in the step S3, the tungsten oxide and carbon mixture is heated to the calcination temperature at a heating rate of 5-10℃ / min, and the calcination temperature is 1100-1300℃, and after the calcination temperature is reached, the calcination is continued for 1-3h.

[0017] According to another aspect of the present application, the present application provides the following technical scheme:

[0018] The superfine tungsten powder is prepared by the above-mentioned preparation method of the superfine tungsten powder, is uniformly dispersed, has complete grain development, has a relatively smooth surface, has no pores and complex morphology, has a body-centered cubic crystal structure, has an average particle size of ≤0.7μm, and has a specific surface area of ≤1.0m 2 / g.

[0019] The present application has the following beneficial effects:

[0020] The present application provides a superfine tungsten powder and a preparation method thereof, uses ammonium tungstate solution, hydrochloric acid and carbon black as raw materials to prepare tungstic acid and carbon precursor mixture, calcines the tungstic acid and carbon precursor mixture in a nitrogen atmosphere to obtain tungsten oxide and carbon mixture, calcines the tungsten oxide and carbon mixture in an argon atmosphere, and naturally cools down under the argon atmosphere to obtain the superfine tungsten powder, which is uniformly dispersed, has complete grain development, has a relatively smooth surface, has no pores and complex morphology, has a body-centered cubic crystal structure, has an average particle size of ≤0.7μm, and has a specific surface area of ≤1.0m 2 / g. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to describe the technical solutions of the embodiments of the present application or the prior art more clearly, the accompanying drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description only show some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort based on the drawings shown.

[0022] Figure 1 SEM image of tungsten powder prepared for Example 1 of the present application;

[0023] Figure 2 XRD image of tungsten powder prepared for Example 1 of the present application;

[0024] Figure 3 SEM image of tungsten powder prepared for Example 2 of the present application;

[0025] Figure 4 SEM image of tungsten powder prepared for Example 3 of the present application

[0026] Figure 5 SEM image of tungsten powder prepared for Comparative Example 1 of the present application;

[0027] Figure 6 XRD image of tungsten powder prepared for Comparative Example 1 of the present application;

[0028] Figure 7 SEM image of tungsten powder prepared for Comparative Example 2 of the present application;

[0029] Figure 8 XRD image of tungsten powder prepared for Comparative Example 2 of the present application;

[0030] Figure 9 SEM image of tungsten powder prepared for Comparative Example 3 of the present application;

[0031] Figure 10 SEM image of tungsten powder prepared for Comparative Example 4 of the present application;

[0032] Figure 11 SEM image of tungsten powder prepared for Comparative Example 5 of the present application;

[0033] Figure 12 XRD image of tungsten powder prepared for Comparative Example 5 of the present application;

[0034] Figure 13 SEM image of tungsten powder prepared for Comparative Example 6 of the present application;

[0035] Figure 14 XRD image of tungsten powder prepared for Comparative Example 6 of the present application.

[0036] The objectives, functional features and advantages of the present application will be further illustrated in conjunction with the embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative effort shall fall within the protection scope of the present application.

[0038] The present application provides a preparation method of ultrafine tungsten powder.

[0039] According to one aspect of the present application, the present application provides the following technical solutions:

[0040] A preparation method of ultrafine tungsten powder, comprising the following steps:

[0041] S1, using ammonium tungstate solution, hydrochloric acid and carbon black as raw materials to prepare tungstic acid and carbon precursor mixture;

[0042] S2, calcining the tungstic acid and carbon precursor mixture in a nitrogen atmosphere to obtain a tungsten oxide and carbon mixture;

[0043] S3, calcining the tungsten oxide and carbon mixture in an argon atmosphere, and keeping the argon atmosphere to naturally cool down, to obtain the ultrafine tungsten powder.

[0044] The active sites on the surface of the carbon powder are used as the nucleation sites of the tungstic acid, which can combine the carbon and tungsten source more closely. Meanwhile, the tungstic acid has a small particle size, and the subsequently generated tungsten oxide is more likely to react with the carbon powder to prepare the ultrafine tungsten powder. Moreover, the nano-tungstic acid is easy to gel in water, and the tungstic acid gel can prevent the originally dispersed carbon powder from re-aggregating during the filtration and drying process. The carbon is used as a reducing agent to prepare the tungsten powder, which avoids the phenomenon of tungsten powder growth caused by the volatilization-deposition mechanism during hydrogen reduction.

[0045] Preferably, in the step S1, the carbon powder is uniformly dispersed in the 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. After washing with pure water and drying, the tungstic acid and carbon precursor mixture is obtained. Further preferably, in the step S1, the concentration of the hydrochloric acid is 13-19 wt%. Specifically, the concentration of the hydrochloric acid can be, for example, any one of 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt% and 19 wt%, or a range between any two of them.

[0046] 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 0.5-3h. Calcination of WO3 and C under a protective gas only generates CO, so theoretically the amount of C added to the raw material should correspond to the amount of WO3 in the raw material in order to carbonize WO3 into W. If there is too much C, WC or W2C is generated, and if there is not enough C, WO2 remains. Nitrogen is used as the protective gas to prevent oxidation of the carbon, and carbon does not undergo carbothermic reduction with tungsten oxide in this range of 550-650°C, and the tungsten 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 a range between any two of them, and the calcination time can be, for example, any one of 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, or a range between any two of them.

[0047] Preferably, in the step S3, the tungsten oxide and carbon mixture is calcined in a tube furnace under an argon atmosphere; the tube furnace is connected to argon gas with a flow rate of 1-4L / min to provide the argon atmosphere. Too large a gas flow rate can easily carry away some of the carbon, resulting in insufficient carbon and failing to completely reduce the tungsten oxide into W powder; too small a gas flow rate can easily cause the generated CO to participate in the reaction to generate rod-shaped tungsten. Specifically, the flow rate of the argon gas can be, for example, any one of 1L / min, 1.5L / min, 2L / min, 2.5L / min, 3L / min, 3.5L / min, 4L / min, or a range between any two of them.

[0048] Preferably, in the step S3, the tungsten oxide and carbon mixture is heated to the calcination temperature at a heating rate of 5-10℃ / min, the calcination temperature is 1100-1300℃, and after reaching the calcination temperature, the calcination is continued for 1-3h. The calcination temperature can have a decisive effect on the thermodynamics and kinetics of the carbothermic reduction, on the one hand, it determines whether the carbothermic reduction of tungsten oxide by carbon can proceed, on the other hand, it greatly affects the reaction speed of the carbothermic reduction, that is, when the temperature is too low, the tungsten oxide does not react with the carbon powder, and when the temperature is too high, the tungsten powder has a too large particle size, which cannot meet the requirements of the ultrafine tungsten powder. If the calcination time is too short, the reaction of the tungsten oxide powder and the carbon is incomplete, so that the carbon content and the oxygen content in the product are too high; if the calcination time is too long, the tungsten powder grains will excessively grow. Specifically, the calcination temperature can be, for example, any one of 1100℃, 1110℃, 1120℃, 1130℃, 1140℃, 1150℃, 1160℃, 1170℃, 1180℃, 1190℃, 1200℃, 1210℃, 1220℃, 1230℃, 1240℃, 1250℃, 1260℃, 1270℃, 1280℃, 1290℃, 1300℃, or a range between any two of them. After reaching the calcination temperature, the continuous calcination time can be, for example, any one of 1h, 1.5h, 2h, 2.5h, 3h, or a range between any two of them.

[0049] According to another aspect of the present application, the present application provides the following technical solutions:

[0050] An ultrafine tungsten powder is prepared by the above-mentioned method for preparing an ultrafine tungsten powder. The ultrafine tungsten powder is uniformly dispersed, the crystal grains are complete, the surface is relatively smooth, there are no pores and complex morphologies, the crystal structure of the ultrafine tungsten powder is body-centered cubic, the average particle size is ≤0.7μm, and the specific surface area is ≤1.0m 2 / g.

[0051] The technical solutions of the present application are further described below in combination with specific embodiments.

[0052] Embodiment 1

[0053] A method for preparing an ultrafine tungsten powder, comprising the following steps:

[0054] S1, uniformly dispersing carbon powder in hydrochloric acid under ultrasonic stirring, then dropping 220g / L ammonium tungstate solution into the hydrochloric acid, and washing and drying to obtain a tungstic acid and carbon precursor mixture; the concentration of the hydrochloric acid is 16wt%;

[0055] S2, calcining the tungstic 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℃, and the calcination time is 1h;

[0056] S3, calcining the tungsten oxide and carbon mixture in a tube furnace in an argon atmosphere, keeping the argon atmosphere to naturally cool down, to obtain the superfine tungsten powder; the tube furnace is provided with the argon atmosphere by introducing argon gas at a flow rate of 2 L / min. The temperature is raised to the calcination temperature at a temperature raising rate of 10 ℃ / min, the calcination temperature is 1200 ℃, and after reaching the calcination temperature, the calcination is continued for 1 h.

[0057] The SEM image of the superfine tungsten powder obtained in this example is shown in Figure 1 The XRD image is shown in Figure 2 It can be seen that the tungsten powder has complete grain development, uniform dispersion, relatively smooth surface, no pores and complex morphology; 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.

[0058] Example 2

[0059] A method for preparing a superfine tungsten powder, comprising the following steps:

[0060] S1, uniformly dispersing carbon powder in hydrochloric acid under ultrasonic stirring, then dropping 190 g / L ammonium tungstate solution into the hydrochloric acid, and washing and drying to obtain a tungstic acid and carbon precursor mixture; the concentration of the hydrochloric acid is 16 wt%;

[0061] S2, calcining the tungstic 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 ℃, and the calcination time is 1 h;

[0062] S3, calcining the tungsten oxide and carbon mixture in a tube furnace in an argon atmosphere, keeping the argon atmosphere to naturally cool down, to obtain the superfine tungsten powder; the tube furnace is provided with the argon atmosphere by introducing argon gas at a flow rate of 2 L / min. The temperature is raised to the calcination temperature at a temperature raising rate of 10 ℃ / min, the calcination temperature is 1200 ℃, and after reaching the calcination temperature, the calcination is continued for 1 h.

[0063] The SEM image of the superfine tungsten powder obtained in this example is shown in Figure 3 It can be seen that the tungsten powder has complete grain development, uniform dispersion, relatively smooth surface, no pores and complex morphology; 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.

[0064] Example 3

[0065] A method for preparing a superfine tungsten powder, comprising the following steps:

[0066] S1, uniformly disperse the carbon powder in hydrochloric acid under ultrasonic stirring, then drop 240 g / L ammonium tungstate solution into the hydrochloric acid, wash with pure water, and dry to obtain a tungsten oxide and carbon precursor mixture; the concentration of the hydrochloric acid is 16 wt%;

[0067] S2, calcine the tungsten oxide 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;

[0068] S3, calcine the tungsten oxide and carbon mixture in a tube furnace in an argon atmosphere, naturally cool under the argon atmosphere, and obtain ultrafine tungsten powder; the tube furnace is connected to argon gas with a flow rate of 3 L / min to provide the argon atmosphere; the temperature is raised to the calcination temperature at a rate of 10°C / min, the calcination temperature is 1300°C, and the calcination is continued for 1.5 h after the calcination temperature is reached.

[0069] The SEM image of the ultrafine tungsten powder obtained in this example is shown in Figure 4 . It can be seen that the tungsten powder has complete grain development, is uniformly dispersed, has a relatively smooth surface, and has no pores or complex morphology; the specific surface area of the tungsten powder is 0.93 m 2 / g, the total carbon content is 0.0047 wt%, the oxygen content is 0.172 wt%, and the average particle size is 0.674 μm.

[0070] Comparative Example 1

[0071] The difference from Example 1 is that the calcination temperature in step S3 is 800°C.

[0072] The SEM image of the product obtained in this comparative example is shown in Figure 5 , and the XRD image is shown in Figure 6 . It can be seen that the product is still tungsten oxide in the form of a sheet, and carbon powder in the form of a sheet can be observed; the main component of the obtained product is β-tungsten oxide, the total carbon content is 11.110 wt%, and the oxygen content is 17.37 wt%.

[0073] Comparative Example 2

[0074] The difference from Example 1 is that the calcination temperature in step S3 is 1400°C.

[0075] The SEM image of the product obtained in this comparative example is shown in Figure 7 , and the XRD image is shown in Figure 8 . It can be seen that there are coarse grains that have grown abnormally in the product; the product is tungsten, the total carbon content is 0.02 wt%, the oxygen content is 0.241 wt%, and the average particle size is 1.133 μm.

[0076] Comparative Example 3

[0077] The difference from Example 1 is that in step S3, the calcination time is 4 hours.

[0078] The SEM image of the product obtained in this comparative example is shown below. Figure 9 As shown, the total carbon content of the sample is 0.016%, and the oxygen content is 0.245%. The SEM image shows that there are obviously abnormally grown coarse grains in the sample, with an average grain size of 1.026 μm.

[0079] Comparative Example 4

[0080] The difference from Example 1 is that in step S3, argon gas is introduced into the tubular furnace at a flow rate of 0.5 L / min to provide an argon atmosphere.

[0081] The SEM image of the product obtained in this comparative example is shown below. Figure 10 As shown, the product contains abnormally grown rod-shaped grains, and the total carbon content of the product is 0.016 wt%, and the oxygen content is 0.209 wt%.

[0082] Comparative Example 5

[0083] The difference from Example 1 is that in step S1, tungstic acid is prepared by slowly adding 240 g / L ammonium tungstate solution dropwise into 16 wt% hydrochloric acid. After the tungstic acid is prepared, carbon powder is added and stirred evenly under ultrasound. 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.

[0084] The SEM image of the product obtained in this comparative example is shown below. Figure 11 As shown, the XRD pattern is as follows Figure 12 As shown, the product exhibits extremely uneven grain size, with abnormally large particles; the total carbon content is 0.940 wt%, and the oxygen content is 2.8 wt%, indicating that some WO3 was not completely reduced. x .

[0085] Comparative Example 6

[0086] The difference from Example 1 is that in step S3, a hydrogen atmosphere is used instead of an argon atmosphere.

[0087] The SEM image of the product obtained in this comparative example is shown below. Figure 13 As shown, the XRD pattern is as follows Figure 14 As shown, the crystal particles in the product are relatively large, with a diameter of about 1 μm, and contain a large amount of residual carbon; the product contains three substances: WC, W2C and W, with a total carbon content of 5.64 wt% and a free carbon content of 2.31 wt%.

[0088] The above merely describes the preferred embodiments of the present application, and is not intended to limit the patent scope of the present application. Any equivalent structural variations or direct / indirect applications in other related technical fields based on the content of the present application description are included in the patent protection scope of the present application.

Claims

1. A method for preparing ultrafine tungsten powder, characterized in that, Includes the following steps: S1. Carbon powder is uniformly dispersed in hydrochloric acid under ultrasonic stirring, and then ammonium tungstate solution is added dropwise to hydrochloric acid. After washing with pure water and drying, a mixture of tungstic acid and carbon precursor is obtained. S2. A mixture of tungstic acid and carbon precursor is calcined in a nitrogen atmosphere to obtain a mixture of tungsten oxide and carbon; the molar ratio of tungsten oxide to carbon in the tungsten oxide and carbon mixture is 1:3; the calcination temperature is 550~650℃, and the calcination time is 0.5~3h; S3. The mixture of tungsten oxide and carbon is calcined in a tube furnace under an argon atmosphere. The tube furnace is supplied with argon gas at a flow rate of 1~4 L / min to provide an argon atmosphere. The temperature is increased to the calcination temperature at a rate of 5~10℃ / min. The calcination temperature is 1100~1300℃. After reaching the calcination temperature, the calcination is continued for 1~3 hours. The argon atmosphere is maintained for natural cooling to obtain ultrafine tungsten powder. The ultrafine tungsten powder is uniformly dispersed, with well-developed grains, a body-centered cubic crystal structure, an average particle size ≤0.7μm, and a specific surface area ≤1.0m². 2 / g.

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

3. An ultrafine tungsten powder, characterized in that, It is prepared by the method for preparing ultrafine tungsten powder according to any one of claims 1-2.

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