Uniform superfine tungsten powder and preparation method thereof

Abstract

The invention belongs to the technical field of metal powder preparation, and particularly relates to uniform superfine tungsten powder and a preparation method thereof. The preparation method comprises the following steps: S1, obtaining an ammonium tungstate solution and a first solvent; the first solvent is obtained by mixing water and ethanol; s2, dropwise adding the ammonium tungstate solution and the hydrazine hydrate solution into a first solvent to obtain a first system; the molar ratio of hydrazine hydrate to WO3 in the ammonium tungstate solution is (4-9): 1; s3, continuously stirring the first system to crystallize the first system, and then performing suction filtration and drying to obtain precursor powder; and S4, in the atmosphere of protective gas, the precursor powder is heated, so that the precursor powder is subjected to self-reduction, and the uniform superfine tungsten powder is obtained. The prepared uniform superfine tungsten powder is uniform in particle size, and the average particle size is 100-400 nm. The dosage of the reducing agent is controllable, reduction is sufficient and thorough, and the tungsten powder is uniform in particle size; high-purity tungsten powder can be obtained, and introduction of impurities is avoided; the method has the advantages of simplicity in operation, high reproducibility, short process, simple equipment, easiness in industrialization, cost saving and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metal powder preparation, and particularly relates to a uniform superfine tungsten powder and a preparation method thereof. BACKGROUND

[0002] In the modern industrial production system, as a kind of vital material, hard alloy plays an irreplaceable role in many fields due to its high hardness, high strength, excellent wear resistance and heat resistance, etc. As the core basic raw material for preparing hard alloy, the development level of tungsten powder preparation technology directly affects the development direction and quality improvement of the hard alloy industry.

[0003] In the early stage, due to the relatively low requirement of industrial production on material performance, the tungsten powder produced by the traditional tungsten powder preparation process has obvious limitations in purity, particle size uniformity, etc. This leads to the fact that the prepared hard alloy is difficult to meet the actual use requirements under complex working conditions in terms of hardness, toughness and other comprehensive performance. With the rapid development of manufacturing industry towards high precision, high efficiency and high reliability, especially the rapid rise of high-end industries such as aerospace, automobile manufacturing and electronic information, more stringent challenges are put forward for the performance of hard alloy. For example, in the manufacturing process of high-temperature parts of aero-engine, the hard alloy material is required to have excellent wear resistance and fatigue resistance while bearing high temperature and high pressure; in the electronic manufacturing field, with the continuous intensification of the miniaturization trend of products, high requirements are put forward for the precision and durability of hard alloy cutters. In order to meet these growing high-performance requirements, researchers and enterprises actively explore more advanced tungsten powder preparation technology to continuously improve the quality and performance of hard alloy products.

[0004] The traditional tungsten powder preparation method is mainly to obtain tungsten oxide by reducing high-purity tungsten oxide through hydrogen reduction method; the source of tungsten oxide is mainly converted from tungstic acid and ammonium paratungstate; the preparation of tungsten oxide from tungstate is generally carried out in an open calcination furnace using air in the factory environment, which is easy to cause product contamination, and a large amount of ammonia gas is generated during the cracking process of tungstate, which needs to increase the recovery facility; the preparation of tungsten powder from tungsten oxide includes multi-stage hydrogen reduction; the overall process flow is long, the equipment is complex, and the product quality fluctuates. SUMMARY

[0005] To solve the above technical problems, the application provides a preparation method of uniform superfine tungsten powder, which comprises the following steps: S1, obtaining an ammonium tungstate solution and a first solvent; the first solvent is obtained by mixing water and ethanol, and the temperature of the first solvent is heated and maintained at a predetermined temperature; S2, drop the ammonium tungstate solution and the hydrazine hydrate solution into the first solvent under the condition of stirring the first solvent to obtain a first system, and maintain the temperature of the first system at the predetermined temperature during the dropping process; the molar ratio of hydrazine hydrate in the hydrazine hydrate solution to WO3 in the ammonium tungstate solution is (4-9):1; S3, continuously stir the first system to crystallize under the condition of maintaining the temperature of the first system at the predetermined temperature, then perform suction filtration and drying to obtain a precursor powder; S4, heat the precursor powder in an atmosphere of a protective gas to self-reduce the precursor powder to obtain the uniform ultrafine tungsten powder; Further, the molar ratio of hydrazine hydrate in the hydrazine hydrate solution to WO3 in the ammonium tungstate solution in step S2 is any one of 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or a range between any two of them.

[0006] As a preferred scheme of the method for preparing the uniform ultrafine tungsten powder, in step S1, the ratio of water to ethanol in the first solvent is 1:(0.5-1.5).

[0007] As a preferred scheme of the method for preparing the uniform ultrafine tungsten powder, in step S2, the ammonium tungstate solution and the hydrazine hydrate solution are dropped through a dropping funnel, the dropping rate of the ammonium tungstate solution is 25-50 mL / min, the dropping rate of the hydrazine hydrate solution is 9-20 mL / min, and the sum of the volumes of the ammonium tungstate solution and the hydrazine hydrate solution is 10-30 times that of the first solvent. Further, the ammonium tungstate solution and the hydrazine hydrate solution are started to be dropped at the same time and completed to be dropped at the same time.

[0008] As a preferred scheme of the method for preparing the uniform ultrafine tungsten powder, in steps S1, S2 and S3, the heating and temperature maintaining mode is water bath, and the predetermined temperature is 20-90℃. Further, the predetermined temperature is any one of 20℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 90℃ or a range between any two of them.

[0009] As a preferred scheme of the method for preparing the uniform ultrafine tungsten powder, in step S2, the WO3 content in the ammonium tungstate solution is 130-230 g / L, and the concentration of the hydrazine hydrate solution is 4-16 mol / L.

[0010] As a preferred scheme of the method for preparing the uniform ultrafine tungsten powder, in step S3, the time for stirring to crystallize is 4-8 h, the drying temperature is 70-90℃, and the drying time is 7-10 h.

[0011] As a preferred scheme of the preparation method of the uniform ultrafine tungsten powder, in step S4, the protective gas comprises at least one of inert gas and hydrogen. Further, the protective gas is N2.

[0012] As a preferred scheme of the preparation method of the uniform ultrafine tungsten powder, in step S4, the protective gas is N2 or H2, the flow rate is 1-3 L / min, the precursor powder is heated in the tube furnace, the temperature is 800-1000℃, and the reduction time is 3-7 h.

[0013] To solve the above technical problems, the application further provides a uniform ultrafine tungsten powder, which is prepared by the preparation method of the uniform ultrafine tungsten powder.

[0014] As a preferred scheme of the uniform ultrafine tungsten powder, the uniform ultrafine tungsten powder has uniform particle size, and the average particle size is 100-400 nm.

[0015] The application has the following advantages: the amount of the reducing agent is controllable, the reduction is complete, the tungsten powder has uniform particle size, high-purity tungsten powder can be obtained, impurities are avoided to be introduced, the operation is simple, the reproducibility is high, the process is short, the equipment is simple, the industrialization is easy, and the cost is saved. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only show some embodiments of the application, and for those skilled in the art, other drawings can also be obtained according to the structures shown in the drawings without creative labor.

[0017] Figure 1 The SEM image of the uniform ultrafine tungsten powder prepared in Example 1; Figure 2 The SEM image of the tungsten powder prepared in Comparative Example 1; Figure 3 The SEM image of the tungsten powder prepared in Comparative Example 2; Figure 4 The SEM image of the tungsten powder prepared in Comparative Example 3; Figure 5 The SEM image of the tungsten powder prepared in Comparative Example 5; Figure 6 The SEM image of the tungsten powder prepared in Comparative Example 6.

[0018] The implementation, functional features and advantages of the application will be further described with reference to the embodiments and the drawings. DETAILED DESCRIPTION

[0019] 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 a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0020] The present application provides a preparation method of uniform ultrafine tungsten powder, comprising the following steps: S1, obtaining an ammonium tungstate solution and a first solvent; the first solvent is obtained by mixing water and ethanol, and the temperature of the first solvent is maintained at a predetermined temperature by heating; The addition of ethanol helps to regulate the crystallization behavior and morphology of the precursor. As a dispersion medium, it can effectively avoid the agglomeration of precursor particles, thereby laying a foundation for obtaining uniform ultrafine tungsten powder subsequently; S2, under the condition of stirring the first solvent, the ammonium tungstate solution and the hydrazine hydrate solution are added dropwise into the first solvent to obtain a first system, and the temperature of the first system is maintained at the predetermined temperature during the dropwise addition process; the molar ratio of hydrazine hydrate in the hydrazine hydrate solution to WO3 in the ammonium tungstate solution is (4-9):1; Through a large number of experiments, it is determined that the molar ratio of hydrazine hydrate to WO3 should be controlled between 4:1 and 9:1. Too low molar ratio will lead to insufficient reduction of the obtained precursor in the subsequent heating self-reduction step, and there are unreduced oxides in the product; too high molar ratio can be completely reduced, but it is not economical and the excess hydrazine hydrate brings waste liquid treatment problems; the optimal ratio of the present application ensures that the reduction reaction is complete and complete, and high-purity uniform ultrafine tungsten powder with uniform particle size can be obtained; The ammonium tungstate solution and the hydrazine hydrate solution are mixed by dropwise addition, in order to accurately control the addition rate of the reactants, so as to control the temperature of the reaction system and the nucleation and growth process of the precursor; if replaced by rapid or one-time addition, it will cause the nucleation of the precursor to be too fast and the growth to be uneven, finally leading to the particle size distribution of the precursor and the final tungsten powder to be wide and the morphology to be irregular, therefore, this operation is not suitable to be replaced by other mixing methods; S3, continuously stirring the first system to crystallize under the condition that the temperature of the first system is maintained at the predetermined temperature, then filtering and drying to obtain a precursor powder; The reaction of ammonium tungstate and hydrazine hydrate is a complex reaction, and the crystallization product is a tungsten ammine hydroxide, and the hydrazine hydrate is uniformly distributed in the crystallization product; The heating and temperature maintaining mode in S1, S2 and S3 can be a water bath; the water bath is heated to provide a mild, uniform and controllable heating environment, avoiding local overheating and temperature out of control caused by open fire or electric heating mantle, which is crucial for obtaining a precursor with good reproducibility; S4, heating the precursor powder in a protective gas atmosphere to self-reduce the precursor powder to obtain uniform ultrafine tungsten powder; The reducing agent for reducing the precursor to obtain uniform ultrafine tungsten powder is hydrogen gas obtained by decomposing hydrazine hydrate (N2H4·H2O), and no external hydrogen gas is needed to participate in the reduction process. Moreover, during the preparation of the precursor, hydrazine hydrate enters the grain boundaries of the precursor. During the reduction process, the decomposition of hydrazine hydrate causes volume expansion, which causes the precursor grains to crack and be reduced at the same time. Therefore, the reduction process of the present application can be carried out in a H2 atmosphere and other inert gases; the present application uses hydrazine hydrate as a reducing agent and reduces it in a protective gas atmosphere. The source of the reducing agent is clear, the amount of the reducing agent is controllable, the reduction process is sufficient and complete, the introduction of external impurities is effectively avoided, and the high purity and uniformity of the final uniform ultrafine tungsten powder are ensured. The temperature of the heating reduction also affects the uniformity of the tungsten powder particle size. When the temperature is low (600-800℃), the tungsten powder grains have not all grown, and the particle size uniformity is poor. Increasing the temperature can improve the particle size uniformity. When the temperature is 800-1000℃, the grains have grown, and the overall uniformity is good.

[0021] The technical solutions of the present application will be further described in conjunction with specific embodiments.

[0022] Example 1 A preparation method of uniform ultrafine tungsten powder, comprising the following steps: S1, obtaining an ammonium tungstate solution and a first solvent; the first solvent is obtained by mixing water and ethanol, and the temperature of the first solvent is heated and maintained at a predetermined temperature; wherein the WO3 content in the ammonium tungstate solution is 150 g / L, the volume is 1000 mL, and the molar number of WO3 is 0.647 mol; 50 mL (volume ratio 1:1) of water and ethanol are put into a beaker and mixed uniformly by stirring to obtain the first solvent, and the predetermined temperature of the first solvent is maintained at 50℃ by a water bath. S2, drop the ammonium tungstate solution and the hydrazine hydrate solution into the first solvent under the condition of stirring the first solvent to obtain a first system, and maintain the temperature of the first system at the predetermined temperature during the dropping; wherein the concentration of the hydrazine hydrate solution is 12 mol / L, the volume is 350 mL, the mole number of hydrazine hydrate is 4.2 mol, and the mole ratio of hydrazine hydrate to WO3 is 6.5:1; the dropping is performed by using a dropping funnel, the dropping rate of the ammonium tungstate solution is 40 mL / min, the dropping rate of the hydrazine hydrate solution is 14 mL / min, and the sum of the volumes of the ammonium tungstate solution and the hydrazine hydrate solution is 13.5 times of the first solvent; the predetermined temperature of the first system is maintained at 50°C by using a water bath heater during the dropping; S3, continuously stir the first system to crystallize under the condition of maintaining the temperature of the first system at the predetermined temperature, and then perform suction filtration and drying to obtain a precursor powder; wherein the predetermined temperature of the first system is maintained at 50°C by using a water bath heater; the time for continuously stirring the first system to crystallize is 8 h, the drying temperature is 80°C, and the drying time is 10 h; S4, heat the precursor powder in an atmosphere of a protective gas to self-reduce the precursor powder to obtain a uniform ultrafine tungsten powder; wherein the protective gas is H2, the flow rate of H2 is 1.5 L / min, the precursor powder is heated in a tube furnace, the temperature is 850°C, and the reduction time is 5 h.

[0023] Please refer to Figure 1 , Figure 1 The SEM image of the uniform ultrafine tungsten powder prepared in Example 1 can be seen from Figure 1 It can be seen that the crystal grains are angular, there are basically no flocculent crystals, and the overall uniformity of the crystal grains is good, and the average size of the overall crystal grains is about 200 nm.

[0024] Example 2 Different from Example 1: the content of WO3 in the ammonium tungstate solution in S1 is 200 g / L, the volume is 1000 mL, and the mole number of WO3 is 0.863 mol; the concentration of the hydrazine hydrate solution in S2 is 12 mol / L, the volume is 500 mL, the mole number of hydrazine hydrate is 6 mol, the mole ratio of hydrazine hydrate to WO3 is 7:1, the dropping rate of the ammonium tungstate solution is 40 mL / min, the dropping rate of the hydrazine hydrate solution is 20 mL / min, and the sum of the volumes of the ammonium tungstate solution and the hydrazine hydrate solution is 15 times of the first solvent. Except for this, other aspects are the same as those in Example 1.

[0025] Experimental results: the overall crystal grains of the obtained tungsten powder are uniform, the particle size is slightly grown, and the average particle size is about 250 nm.

[0026] Example 3 Different from example 1, the content of WO3 in the ammonium tungstate solution in S1 is 200 g / L, the volume is 1000 mL, and the mole number of WO3 is 0.863 mol; the concentration of the hydrazine hydrate solution in S2 is 12 mol / L, the volume is 500 mL, the mole number of hydrazine hydrate is 6 mol, the mole ratio of hydrazine hydrate to WO3 is 7:1, the dropping rate of the ammonium tungstate solution is 40 mL / min, the dropping rate of the hydrazine hydrate solution is 20 mL / min, and the sum of the volumes of the ammonium tungstate solution and the hydrazine hydrate solution is 15 times the first solvent; the predetermined temperature in S1, S2 and S3 is 60°C; the time for continuously stirring to crystallize in S3 is 6 h. Except for this, the others are the same as example 1.

[0027] Experimental results: the obtained tungsten powder has uniform overall crystal grains, the overall tungsten powder morphology is similar to that of example 2, and the overall average particle size is about 250 nm, but the precursor particle size is more uniform.

[0028] Example 4 Different from example 1, the content of WO3 in the ammonium tungstate solution in S1 is 210 g / L, the volume is 1000 mL, and the mole number of WO3 is 0.906 mol; the concentration of the hydrazine hydrate solution in S2 is 12 mol / L, the volume is 500 mL, the mole number of hydrazine hydrate is 6 mol, the mole ratio of hydrazine hydrate to WO3 is 6.6:1, the dropping rate of the ammonium tungstate solution is 40 mL / min, the dropping rate of the hydrazine hydrate solution is 20 mL / min, and the sum of the volumes of the ammonium tungstate solution and the hydrazine hydrate solution is 15 times the first solvent; the predetermined temperature in S1, S2 and S3 is 80°C; the time for continuously stirring to crystallize in S3 is 4 h. Except for this, the others are the same as example 1.

[0029] Experimental results: the obtained tungsten powder has uniform overall crystal grains, and the overall average particle size is about 280 nm.

[0030] Example 5 Different from example 1, the protective gas in S4 is N2. Except for this, the others are the same as example 1.

[0031] Experimental results: the obtained tungsten powder morphology is similar to that of example 1, the overall average particle size is about 200 nm, but the tungsten powder crystal grains are more rounded.

[0032] Example 6 Different from Example 1: the content of WO3 in the ammonium tungstate solution in S1 was 130 g / L, the volume was 1500 mL, the mole number of WO3 was 0.842 mol, and the volume ratio of water to ethanol was 1:0.5; the concentration of the hydrazine hydrate solution in S2 was 4.5 mol / L, the volume was 750 mL, the mole number of hydrazine hydrate was 3.38 mol, the mole ratio of hydrazine hydrate to WO3 was 4:1, the dropping rate of the ammonium tungstate solution was 50 mL / min, the dropping rate of the hydrazine hydrate solution was 9.3 mL / min, and the volume sum of the ammonium tungstate solution and the hydrazine hydrate solution was 30 times the first solvent; the predetermined temperature in S1, S2 and S3 was 90℃; the time for continuous stirring to make it crystallize in S3 was 4 h, the drying temperature was 70℃, and the drying time was 10 h; the protective gas in S4 was N2, the N2 flow rate was 1 L / min, the reduction temperature was 800℃, and the reduction time was 7 h. Except for the above, the others were the same as in Example 1.

[0033] Experimental results: the obtained tungsten powder had uniform overall crystal grains, and the overall average particle size was about 100 nm.

[0034] Example 7 Different from Example 1: the content of WO3 in the ammonium tungstate solution in S1 was 230 g / L, the volume was 800 mL, the mole number of WO3 was 0.794 mol, and the volume ratio of water to ethanol was 1:1.5; the concentration of the hydrazine hydrate solution in S2 was 16 mol / L, the volume was 450 mL, the mole number of hydrazine hydrate was 7.2 mol, the mole ratio of hydrazine hydrate to WO3 was 9:1, the dropping rate of the ammonium tungstate solution was 25 mL / min, the dropping rate of the hydrazine hydrate solution was 18.5 mL / min, and the volume sum of the ammonium tungstate solution and the hydrazine hydrate solution was 10 times the first solvent; the predetermined temperature in S1, S2 and S3 was 20℃; the time for continuous stirring to make it crystallize in S3 was 8 h, the drying temperature was 90℃, and the drying time was 7 h; the protective gas in S4 was N2, the N2 flow rate was 3 L / min, the reduction temperature was 1000℃, and the reduction time was 3 h. Except for the above, the others were the same as in Example 1.

[0035] Experimental results: the obtained tungsten powder had uniform overall crystal grains, and the overall average particle size was about 400 nm.

[0036] Comparative Example 1 Different from Example 1: the first solvent in S1 only contained water, and 50 mL of water was taken as the first solvent. Except for the above, the others were the same as in Example 1.

[0037] Experimental results: serious agglomeration occurred during the crystallization of the obtained precursor, please refer to Figure 2 , Figure 2The SEM image of the tungsten powder prepared in Comparative Example 1 shows that the tungsten powder has a wide particle size distribution and a large amount of micron-sized agglomerates, and uniform ultrafine tungsten powder cannot be obtained.

[0038] Comparative Example 2 Different from Example 1: the ammonium tungstate solution and the hydrazine hydrate solution were added into the first solvent at one time (not dropwise). Except for this, other conditions were the same as in Example 1.

[0039] Experimental results: the ammonium tungstate solution and the hydrazine hydrate solution were added at one time, which resulted in too fast nucleation of the precursor and uneven crystallization. Please refer to Figure 3 , Figure 3 The SEM image of the tungsten powder prepared in Comparative Example 2 shows that the tungsten powder has an irregular morphology and a wide particle size distribution after reduction, and the uniformity is poor.

[0040] Comparative Example 3 Different from Example 5: the concentration of the hydrazine hydrate solution in S2 was 12 mol / L, the volume was 108 mL, the number of moles of hydrazine hydrate was 1.3 mol, the molar ratio of hydrazine hydrate to WO3 was 2:1, the dropwise addition rate of the ammonium tungstate solution was 40 mL / min, the dropwise addition rate of the hydrazine hydrate solution was 4.3 mL / min, and the sum of the volumes of the ammonium tungstate solution and the hydrazine hydrate solution was 11 times the volume of the first solvent. Except for this, other conditions were the same as in Example 5.

[0041] Experimental results: a large amount of incompletely reduced oxide intermediate phases existed in the product after reduction. Please refer to Figure 4 , Figure 4 The SEM image of the tungsten powder prepared in Comparative Example 3 shows that the grains are not obvious and the particle size uniformity is poor.

[0042] Comparative Example 4 Different from Example 5: the concentration of the hydrazine hydrate solution in S2 was 12 mol / L, the volume was 650 mL, the number of moles of hydrazine hydrate was 7.8 mol, the molar ratio of hydrazine hydrate to WO3 was 12:1, the dropwise addition rate of the ammonium tungstate solution was 40 mL / min, the dropwise addition rate of the hydrazine hydrate solution was 26 mL / min, and the sum of the volumes of the ammonium tungstate solution and the hydrazine hydrate solution was 16.5 times the volume of the first solvent. Except for this, other conditions were the same as in Example 5.

[0043] Experimental results: although the reduction was complete, the economy was poor, and the excessive reducing agent resulted in a high ammonia content in the waste liquid, which was not conducive to subsequent treatment.

[0044] Comparative Example 5 Different from Example 1: the temperature in S4 was 650°C. Except for this, other conditions were the same as in Example 1.

[0045] Experimental results: please refer to Figure 5 , Figure 5The SEM image of the tungsten powder prepared from Comparative Example 5 is shown in Figure 2. Figure 5 It can be seen that there are still many grains that have not grown, and the flocculent structure is adhered to the grown grains.

[0046] Comparative Example 6 The difference from Example 1 is that the temperature in S4 is 750℃. Except for this, it is the same as Example 1.

[0047] Experimental results: please refer to Table 1. Figure 6 , Figure 6 The SEM image of the tungsten powder prepared from Comparative Example 6 is shown in Figure 3. Figure 6 It can be seen that the grains have basically grown, and the grain size is about 200 nm, but the uniformity of the overall grains is slightly poor.

[0048] Comparative Example 1 and Example 1 compared to illustrate the key role of the addition of ethanol in the solvent, the addition of ethanol helps to regulate the crystallization behavior and morphology of the precursor, as a dispersion medium, it can effectively avoid the agglomeration of the precursor particles, thereby laying the foundation for obtaining uniform and uniform ultra-fine tungsten powder subsequently.

[0049] Comparative Example 2 and Example 1 compared to illustrate the key role of the dropwise mixing of the ammonium tungstate solution and the hydrazine hydrate solution, dropwise is to accurately control the addition rate of the reactants, so as to control the temperature and nucleation process of the reaction system. If replaced by rapid or one-time addition, it will lead to rapid and uneven nucleation, ultimately resulting in a wide particle size distribution of the precursor and the final tungsten powder, and irregular morphology.

[0050] Comparative Example 3 and Example 5 compared to illustrate that too low a molar ratio of hydrazine hydrate to WO3 will lead to insufficient reduction, and there are unreduced oxides in the product.

[0051] Comparative Example 4 and Example 5 compared to illustrate that a molar ratio of hydrazine hydrate to WO3 greater than 9:1, although the precursor can be completely reduced, but the economy is poor.

[0052] Comparative Example 5, Comparative Example 6 and Example 1 compared to illustrate that when the temperature is low (600-800℃), the tungsten powder grains have not all grown, and the particle size uniformity is poor; increasing the temperature can improve the particle size uniformity, and when the temperature is 800-1000℃, the grains have grown, and the overall uniformity is good.

[0053] The present application prepares a precursor by a hydrazine hydrate complex method, and then uses a self-reduction technology to prepare a uniform ultra-fine tungsten powder, which has the following beneficial effects: the amount of the reducing agent is controllable, the reduction is complete and thorough, and the tungsten powder has uniform particle size; high-purity tungsten powder can be obtained, avoiding the introduction of impurities; it has the advantages of simple operation, high reproducibility, short process, simple equipment, easy industrialization, cost saving, etc.

[0054] 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 producing uniform ultrafine tungsten powder, characterized by, The method comprises the following steps: S1, obtaining an ammonium tungstate solution and a first solvent; the first solvent is obtained by mixing water and ethanol, and the temperature of the first solvent is maintained at a predetermined temperature by heating; S2, under the condition of stirring the first solvent, the ammonium tungstate solution and a hydrazine hydrate solution are added dropwise into the first solvent to obtain a first system, and the temperature of the first system is maintained at the predetermined temperature during the dropwise adding process; the molar ratio of hydrazine hydrate in the hydrazine hydrate solution to WO3 in the ammonium tungstate solution is (4-9):1; S3, under the condition of maintaining the temperature of the first system at the predetermined temperature, the first system is continuously stirred to crystallize, and then is subjected to suction filtration and drying to obtain a precursor powder; S4, under the atmosphere of a protective gas, the precursor powder is heated to self-reduce the precursor powder to obtain a uniform ultrafine tungsten powder.

2. The method of claim 1, wherein the tungsten powder has a D50 of 0.1 to 0.5 μm. In the step S1, the ratio of water to ethanol in the first solvent is 1:(0.5-1.5).

3. The method of claim 1, wherein the tungsten powder has a D50 of 0.1 to 0.5 μm. In the step S2, the ammonium tungstate solution and the hydrazine hydrate solution are added dropwise through a dropping funnel, the rate of adding the ammonium tungstate solution is 25-50 mL / min, the rate of adding the hydrazine hydrate solution is 9-20 mL / min, and the sum of the volumes of the ammonium tungstate solution and the hydrazine hydrate solution is 10-30 times of the first solvent.

4. The method of claim 1, wherein the tungsten powder has a D50 of 0.1 to 0.5 μm. In the steps S1, S2 and S3, the heating and temperature maintaining mode is water bath, and the predetermined temperature is 20-90℃.

5. The method of claim 1, wherein the tungsten powder has a D50 of 0.1 to 0.5 μm. In the step S2, the content of WO3 in the ammonium tungstate solution is 130-230 g / L, and the concentration of the hydrazine hydrate solution is 4-16 mol / L.

6. The method of claim 1, wherein the tungsten powder has a D50 of 0.1 to 0.5 μm. In the step S3, the time for stirring to crystallize is 4-8 h, the drying temperature is 70-90℃, and the drying time is 7-10 h.

7. The method of claim 1, wherein the tungsten powder has a D50 of 0.1 to 0.5 μm. In the step S4, the protective gas comprises at least one of an inert gas and hydrogen.

8. The method of claim 1, wherein the tungsten powder has a D50 of 0.1 to 0.5 μm. In the step S4, the protective gas is N2 or H2, the flow rate is 1-3 L / min, the precursor powder is heated in a tube furnace, the temperature is 800-1000℃, and the reduction time is 3-7 h.

9. A uniform ultrafine tungsten powder, characterized by, The uniform ultrafine tungsten powder is prepared by the method of any one of claims 1-8.

10. The uniform ultrafine tungsten powder of claim 9, wherein, The uniform ultrafine tungsten powder has uniform particle size, and the average particle size is 100-400 nm.

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