A method for preparing ultrafine nano-tungsten carbide powder

Abstract

This invention discloses a method for preparing ultrafine nano-tungsten carbide powder, comprising: 1. preparing a mixed solvent; 2. dissolving tungsten salt in the mixed solvent to obtain a transparent solution A; 3. adding dilute acid to the transparent solution B and carrying out a homogeneous reaction to obtain ultrafine nano-WO3 material; 4. obtaining ultrafine WO2 nanomaterial through a reduction reaction; 5. uniformly compounding with a carbon source; 6. obtaining nano-WC powder through a carbonization reaction. This invention utilizes a hydrothermal method to synthesize ultrafine nano-WO3 material with good dispersibility and uniform morphology and size, providing a foundation for subsequently obtaining highly dispersible and small-sized tungsten dioxide particles. The stepwise reduction method, combining reduction and carbonization, avoids the chemical vapor transport process in the WO2-W process, resulting in ultrafine nano-WC powder. This method is low-cost, low-energy-consumption, and has a short reaction time, showing high industrial application potential.

Description

Technical Field

[0001] This invention belongs to the field of nanopowder material preparation technology, specifically relating to a method for preparing ultrafine nano tungsten carbide powder. Background Technology

[0002] Tungsten carbide-cobalt (WC-Co) cemented carbide possesses high hardness, high wear resistance, high red hardness, high compressive strength, high elastic modulus, high toughness, low coefficient of thermal expansion, and good chemical stability. Combining the advantages of both tungsten carbide and cobalt, it has wide applications in aerospace, automotive, electronics, shipbuilding, mining, oil drilling, and military industries. It is known as the "teeth of industry" and is a key material driving the development of manufacturing and processing levels in these fields.

[0003] Currently, the aerospace, precision machining / manufacturing, and electronics industries are developing rapidly, leading to a surge in demand for precision machining of high-temperature alloy materials, lightweight alloys such as titanium / aluminum, high-hardness steel mold materials, composite materials, and printed circuit board materials. This necessitates cemented carbide materials with higher hardness, heat resistance, strength, and toughness. However, conventional WC-Co cemented carbides suffer from a trade-off between hardness and strength; increasing hardness leads to decreased strength, and vice versa. To address this issue, researchers have discovered that when the WC grain size in WC-Co cemented carbides is reduced to below the nanometer scale (average grain size 0.1μm–0.2μm), the material's hardness, toughness, strength, and wear resistance all experience significant improvements, demonstrating its potential to replace traditional cemented carbides. Therefore, nanocrystalline WC-Co cemented carbides, possessing higher hardness, wear resistance, strength, and excellent toughness, have rapidly gained widespread attention and become a research hotspot since their emergence, representing a crucial direction for cemented carbide development both domestically and internationally.

[0004] The low-cost, large-scale, and controllable preparation of high-quality nano-tungsten carbide powder is a key raw material foundation for the preparation of high-performance nanocrystalline cemented carbides. Nano-tungsten carbide powder is produced by carbonizing nano-tungsten powder, and the biggest challenge lies in the preparation of high-quality nano-tungsten powder. Traditional hydrogen reduction of tungsten oxide processes generates water vapor, leading to low tungsten nucleation rates and the "dissolution-volatilization-deposition" phenomenon. This is because the hydrogen reduction of WO3-WO2-W involves a chemical vapor transport (CVT) process, with a strong CVT process mainly occurring between WO2 and W. The resulting intermediate product (WO2(OH)2) promotes the aggregation and growth of W powder, leading to an increase in WC powder particle size during carbonization. The resulting WC-Co cemented carbide has coarse grains, reduced performance, and fails to achieve the desired fine-grain strengthening effect. Therefore, particle size control is extremely challenging in this process.

[0005] The supply of high-quality nano-tungsten carbide raw materials is a crucial step in the preparation of high-end nanocrystalline cemented carbides. Therefore, there is an urgent need to vigorously develop technologies for preparing highly dispersed, ultra-fine nano-tungsten powder and tungsten carbide powder. Summary of the Invention

[0006] The technical problem to be solved by this invention is to provide a method for preparing ultrafine nano-tungsten carbide powder, addressing the shortcomings of the prior art. This method utilizes a hydrothermal method to synthesize ultrafine nano-WO3 materials with good dispersibility and uniform morphology and size, providing a foundation for subsequently obtaining highly dispersible and small-sized tungsten dioxide particles. Then, a stepwise reduction process combining reduction and carbonization is employed, avoiding the chemical vapor transport process in the WO2-W process, resulting in ultrafine nano-WC powder. This solves the problem of poor dispersibility and size uniformity of nano-tungsten carbide particles prepared by conventional hydrogen reduction.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for preparing ultrafine nano-tungsten carbide powder, characterized in that the method includes the following steps:

[0008] Step 1: Mix ethanol and deionized water at room temperature, then slowly add oleic acid while stirring to obtain a homogeneous and transparent mixed solvent.

[0009] Step 2: Add the tungsten salt to the mixed solvent obtained in Step 1 and stir until completely dissolved to obtain a transparent solution A;

[0010] Step 3: Dilute the concentrated acid into a transparent solution B, then add the transparent solution B dropwise to the transparent solution A obtained in step 2 to adjust the pH, and transfer it to a polytetrafluoroethylene reactor for homogeneous reaction. After naturally cooling to room temperature, the yellow ultrafine nano WO3 material is obtained by vacuum freeze drying.

[0011] Step 4: The ultrafine nano-WO3 material obtained in Step 3 is subjected to a reduction reaction and the oxygen vacancies are adjusted to obtain ultrafine WO2 nanomaterials with high activity and high oxygen vacancies.

[0012] Step 5: The ultrafine WO2 nanomaterials obtained in Step 4 are uniformly compounded with a carbon source to obtain nanocomposite powder containing tungsten oxide and carbon.

[0013] Step 6: The nanocomposite powder containing tungsten oxide and carbon obtained in Step 5 is subjected to a carbonization reaction to obtain nano WC powder.

[0014] Typically, in step one of this invention, ethanol and deionized water are placed in a magnetic stirrer and stirred at a speed of 400 r / min to 600 r / min for 5 min to 10 min; oleic acid is slowly added and the mixture is stirred at a speed of 400 r / min to 600 r / min for another 5 min to 10 min.

[0015] In step one of this invention, tungsten salt is added to the mixed solvent and stirred at a speed of 400 r / min to 600 r / min for 0.5 h to 1 h until completely dissolved.

[0016] In step three of this invention, after naturally cooling to room temperature, the polytetrafluoroethylene reactor is opened, and the homogeneous product is taken out and washed sequentially with anhydrous ethanol and deionized water and centrifuged. The washing is repeated 4 times and then vacuum freeze-dried.

[0017] In step five of this invention, the ultrafine WO2 nanomaterials and the carbon source are thoroughly ground and stirred until uniform to achieve uniform composite.

[0018] The above-mentioned method for preparing ultrafine nano-tungsten carbide powder is characterized in that, in step one, the volume ratio of ethanol to deionized water is 5:1, and the volume ratio of oleic acid to the total volume of ethanol and deionized water is 1 to 5:30. This invention uses oleic acid as a surfactant, and by controlling the volume ratio of oleic acid to the total volume of ethanol and deionized water, the nucleation and growth process of WO3 during the hydrothermal reaction is controlled, thereby controlling the size of the ultrafine nano-WO3 material; simultaneously, since oleic acid is soluble in ethanol but insoluble in water, a mixed solvent of ethanol and deionized water is not used.

[0019] The above-described method for preparing ultrafine nano-tungsten carbide powder is characterized in that the tungsten salt in step two is sodium tungstate dihydrate, and the concentration of the transparent solution A is 0.05 mol / L to 0.25 mol / L. Sodium tungstate dihydrate is readily soluble in water and is a suitable tungsten source for mixed solvents. Simultaneously, by controlling the concentration of the transparent solution A, i.e., the tungsten salt concentration, suitable nucleation sites are formed to obtain ultrafine nano-sized particles. This avoids the problem of excessively low concentration leading to low reaction efficiency, and excessively high concentration leading to rapid nucleation and excessively large particle size, thus preventing the acquisition of small-sized nanoparticles.

[0020] The above-described method for preparing ultrafine nano-tungsten carbide powder is characterized in that, in step three, the concentrated acid is concentrated hydrochloric acid, and the concentration of the transparent solution B is 0.1 mol / L to 1 mol / L, with a pH of 1 to 2; the homogeneous reaction temperature is 120℃ to 180℃, and the reaction time is 10 h to 24 h; the vacuum freeze-drying temperature is below -40℃, the vacuum degree is below 40 Pa, and the drying time is above 8 h. These preferred conditions are suitable for the nucleation and growth of WO3.

[0021] The above-mentioned method for preparing ultrafine nano-tungsten carbide powder is characterized in that the reduction atmosphere used in step four is an inert gas with a hydrogen volume content greater than 10%, the heating rate of the reduction reaction is 5℃ / min to 10℃ / min, the temperature is 500℃ to 700℃, and the holding time is 1h to 3h. During the hydrogen reduction process of ultrafine nano-WO3 materials, a gaseous intermediate product (WO2(OH)2) is generated. This invention uses a hydrogen reduction atmosphere containing an inert gas to reduce the hydrogen concentration, combined with a lower reduction temperature, resulting in a lower concentration of the generated gaseous intermediate product (WO2(OH)2) and reduced water vapor generation. Therefore, tungsten is difficult to migrate in the gaseous phase, and the tungsten product maintains the original morphology and particle size of tungsten oxide, thus ensuring effective morphology transfer.

[0022] The above-described method for preparing ultrafine nano-tungsten carbide powder is characterized in that the carbon source in step five is highly active carbon nanoparticles with a particle size of less than 100 nm, and the molar ratio of ultrafine WO2 nanomaterials to the carbon source is 1:3.0–3.5. This invention controls the particle size of the carbon source, thereby controlling the morphology of nucleation sites during the carbonization reaction to ensure the acquisition of ultrafine nano-WC powder; by controlling the molar ratio of the two materials, the carbon source is ensured to meet the requirements of the carbonization reaction without producing excessive residues after the reaction.

[0023] The above-described method for preparing ultrafine nano-tungsten carbide powder is characterized in that the protective atmosphere used in step six for the carbonization reaction is argon or nitrogen, the heating rate is 5℃ / min to 20℃ / min, the temperature is 1100℃ to 1400℃, and the holding time is more than 3 hours. Compared with the traditional method of preparing tungsten carbide with a carbonization temperature greater than 1400℃, the preparation method of the present invention reduces the carbonization reaction temperature and reduces energy consumption costs.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] 1. This invention utilizes a hydrothermal method to prepare ultrafine nano-WO3 materials through homogeneous reaction. By adding the surfactant oleic acid and controlling the composition and reaction conditions of the homogeneous reaction system, the nucleation and growth process of tungsten trioxide is regulated, effectively controlling the particle size of the product and obtaining ultrafine tungsten trioxide nanoparticles with good product dispersibility and size uniformity. The size is approximately 10 nm to 20 nm, providing a foundation for further preparation of ultrafine WO2 nanomaterials and nano-WC powder particles.

[0026] 2. This invention utilizes a combination of reduction and carbonization. First, oxygen vacancies are adjusted through low-temperature hydrogen reduction to achieve the transition from WO3 to WO2, producing ultrafine WO2 nanoparticles. Then, carbonization with a solid carbon source is used to achieve the transition from WO2 to W. This avoids the chemical vapor transport process in the WO2-W process, ensuring the transfer of structural uniformity and size uniformity of the highly dispersed ultrafine nano WO3 material, thereby preventing the subsequent aggregation and growth of WC powder and effectively controlling the particle size of the nano WC powder.

[0027] 3. This invention utilizes a hydrothermal method to prepare ultrafine nano-WO3 particles, combined with the control of the nucleation and growth process of the products during hydrogen reduction and carbonization. Through stepwise preparation, ultrafine nano-tungsten carbide with an average particle size of 60 nm is obtained, which is suitable for the synthesis of high-performance cemented carbide and has wide applications in aviation, aerospace, automotive, electronics, shipbuilding, mining, oil drilling, and military industries. In addition, the method of this invention has low cost, low energy consumption, and short reaction time, and has high industrial application prospects.

[0028] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0029] Figure 1 The image shows the XRD pattern of the ultrafine nano-WO3 material prepared in Example 3 of this invention.

[0030] Figure 2a This is a low-magnification SEM image of the ultrafine nano-WO3 material prepared in Example 3 of the present invention.

[0031] Figure 2b This is a high-magnification SEM image of the ultrafine nano-WO3 material prepared in Example 3 of the present invention.

[0032] Figure 3 The XRD pattern of the highly active and oxygen-vacancy-rich ultrafine WO2 nanomaterials prepared in Example 3 of this invention.

[0033] Figure 4a This is a low-magnification SEM image of the highly active and oxygen-vacancy-rich ultrafine WO2 nanomaterials prepared in Example 3 of the present invention.

[0034] Figure 4b This is a high-magnification SEM image of the highly active and oxygen-vacancy-rich ultrafine WO2 nanomaterials prepared in Example 3 of this invention.

[0035] Figure 5 XRD pattern of nano-WC powder prepared in Example 3 of this invention.

[0036] Figure 6a This is a low-magnification SEM image of the nano-WC powder prepared in Example 3 of the present invention.

[0037] Figure 6b This is a high-magnification SEM image of the nano-WC powder prepared in Example 3 of the present invention. Detailed Implementation

[0038] Example 1

[0039] This embodiment includes the following steps:

[0040] Step 1: At room temperature, place 40 mL of ethanol and 8 mL of deionized water on a magnetic stirrer and stir at 400 r / min for 5 min to mix them. Then slowly add 2 mL of oleic acid and continue stirring at 400 r / min for 5 min to obtain a homogeneous and transparent mixed solvent.

[0041] Step 2: Add 0.735g of sodium tungstate dihydrate to 50mL of the mixed solvent obtained in Step 1, and stir at 400r / min for 0.5h until completely dissolved to obtain transparent solution A;

[0042] Step 3: Dilute concentrated hydrochloric acid to a 0.1 mol / L transparent solution B, then add transparent solution B dropwise to the transparent solution A obtained in step 2 to adjust the pH to about 1, and transfer it to a 100 mL polytetrafluoroethylene reactor for homogeneous reaction at 120 °C for 10 h. After natural cooling to room temperature, remove the homogeneous reaction product and wash it sequentially with anhydrous ethanol and deionized water and centrifuge. Repeat the washing 4 times, and then place it in a freeze dryer at -40 °C and a vacuum of 10 Pa for 8 h to obtain yellow ultrafine nano WO3 material.

[0043] Step 4: Reduce 5g of the ultrafine nano WO3 material obtained in Step 3 and adjust the oxygen vacancies. The reduction atmosphere is an inert gas with a hydrogen volume content of 80%. The heating rate of the reduction reaction is 5℃ / min, the temperature is 500℃, and the holding time is 3h. Highly active ultrafine WO2 nanomaterials with high oxygen vacancies are obtained.

[0044] Step 5: Grind and stir the ultrafine WO2 nanomaterials obtained in Step 4 with highly active carbon nanoparticles with a particle size of 80 nm until uniform to achieve uniform composite. The molar ratio of ultrafine WO2 nanomaterials to carbon source is 1:3.0 to obtain nanocomposite powder containing tungsten oxide and carbon.

[0045] Step 6: Carbide 5g of the tungsten oxide and carbon nanocomposite powder obtained in Step 5. The protective atmosphere is argon, the heating rate is 5℃ / min, the temperature is 1100℃, and the holding time is 3h to obtain nano WC powder.

[0046] Example 2

[0047] This embodiment includes the following steps:

[0048] Step 1: At room temperature, place 33.3 mL of ethanol and 6.7 mL of deionized water on a magnetic stirrer and stir at 600 r / min for 1 min to mix them. Then slowly add 10 mL of oleic acid and continue stirring at 600 r / min for 10 min to obtain a homogeneous and transparent mixed solvent.

[0049] Step 2: Add 3.76g of sodium tungstate dihydrate to 50mL of the mixed solvent obtained in Step 1, and stir at 600r / min for 1h until completely dissolved to obtain transparent solution A;

[0050] Step 3: Dilute concentrated hydrochloric acid to a 1 mol / L transparent solution B, then add transparent solution B dropwise to transparent solution A obtained in step 2 to adjust the pH to about 2, and transfer it to a 100 mL polytetrafluoroethylene reactor for homogeneous reaction at 180℃ for 24 h. After natural cooling to room temperature, remove the homogeneous reaction product and wash it sequentially with anhydrous ethanol and deionized water and centrifuge. Repeat the washing 4 times, and then place it in a freeze dryer at -70℃ and 40 Pa vacuum for 24 h to obtain yellow ultrafine nano WO3 material.

[0051] Step 4: Reduce 10g of the ultrafine nano WO3 material obtained in Step 3 and adjust the oxygen vacancies. The reduction atmosphere is an inert gas with a hydrogen volume content of 60%. The heating rate of the reduction reaction is 10℃ / min, the temperature is 700℃, and the holding time is 1h. This yields ultrafine WO2 nanomaterials with high activity and high oxygen vacancies.

[0052] Step 5: Grind and stir the ultrafine WO2 nanomaterials obtained in Step 4 with highly active carbon nanoparticles with a particle size of 85nm until uniform to achieve uniform composite. The molar ratio of ultrafine WO2 nanomaterials to carbon source is 1:3.5 to obtain nanocomposite powder containing tungsten oxide and carbon.

[0053] Step 6: Place 10g of the tungsten oxide and carbon nanocomposite powder obtained in Step 5 into an alumina crucible with a length × width × height of 100mm × 40mm × 20mm, and place it in a low-temperature tube furnace for carbonization reaction. The protective atmosphere is nitrogen, the heating rate is 20℃ / min, the temperature is 1400℃, and the holding time is 6h to obtain nano WC powder.

[0054] Example 3

[0055] This embodiment includes the following steps:

[0056] Step 1: At room temperature, place 35 mL of ethanol and 7 mL of deionized water on a magnetic stirrer and stir at 500 r / min for 10 min to mix them. Then slowly add 8 mL of oleic acid and continue stirring at 500 r / min for 10 min to obtain a homogeneous and transparent mixed solvent.

[0057] Step 2: Add 1.47g of sodium tungstate dihydrate to 50mL of the mixed solvent obtained in Step 1, and stir at 500r / min for 1h until completely dissolved to obtain transparent solution A;

[0058] Step 3: Dilute concentrated hydrochloric acid to prepare a 0.5 mol / L transparent solution B. Then, add transparent solution B dropwise to the transparent solution A obtained in step 2 to adjust the pH to about 1.5. Transfer the solution to a 100 mL polytetrafluoroethylene reactor for homogeneous reaction at 160 °C for 12 h. Allow the solution to cool naturally to room temperature. Remove the homogeneous reaction product and wash the solution sequentially with anhydrous ethanol and deionized water, followed by centrifugation. Repeat the washing process four times. Then, dry the solution in a freeze dryer at -40 °C and a vacuum of 25 Pa for 12 h to obtain yellow ultrafine nano-WO3 material.

[0059] Step 4: Reduce 5g of the ultrafine nano WO3 material obtained in Step 3 and adjust the oxygen vacancies. The reduction atmosphere is an inert gas with a hydrogen volume content of 50%. The heating rate of the reduction reaction is 10℃ / min, the temperature is 560℃, and the holding time is 3h. Highly active ultrafine WO2 nanomaterials with high oxygen vacancies are obtained.

[0060] Step 5: Grind and stir the ultrafine WO2 nanomaterials obtained in Step 4 with highly active carbon nanoparticles with a particle size of 40 nm until uniform to achieve uniform composite. The molar ratio of ultrafine WO2 nanomaterials to carbon source is 1:3.2 to obtain nanocomposite powder containing tungsten oxide and carbon.

[0061] Step 6: Carbide 5g of the tungsten oxide and carbon nanocomposite powder obtained in Step 5. The protective atmosphere is argon, the heating rate is 10℃ / min, the temperature is 1200℃, and the holding time is 4h to obtain nano WC powder.

[0062] Figure 1 The image shows the XRD pattern of the ultrafine nano-WO3 material prepared in this embodiment. Figure 1 It can be seen that the structure of this ultrafine nano WO3 material is consistent with that of WO3 with JCPDS number 33-1387, with no other impurities present, high purity, and good crystallinity.

[0063] Figure 2a and Figure 2bThese are low-magnification and high-magnification SEM images of the ultrafine nano-WO3 material prepared in this embodiment, combined with... Figure 2a and Figure 2b It can be seen that the particle size of this ultrafine nano WO3 material is uniform, ranging from approximately 10 nm to 20 nm.

[0064] Figure 3 The XRD pattern of the highly active and oxygen-vacancy-rich ultrafine WO2 nanomaterials prepared in this embodiment is shown below. Figure 3 It can be seen that the structure of this ultrafine WO2 nanomaterial is consistent with that of WO2 with JCPDS number 32-1393, with no other impurities present, high purity, and good crystallinity.

[0065] Figure 4a and Figure 4b The images shown are low-magnification and high-magnification SEM images of the highly active and oxygen-vacancy-rich ultrafine WO2 nanomaterials prepared in this embodiment, respectively, combined with... Figure 4a and Figure 4b It can be seen that the particles of this ultrafine WO2 nanomaterial have a uniform size and shape, approximately 40 nm.

[0066] Figure 5 The XRD pattern of the nano-WC powder prepared in this embodiment is shown below. Figure 5 It can be seen that the nano WC powder has the same structure as the WC with JCPDS number 51-0939, with no other impurities present, high purity, and good crystallinity.

[0067] Figure 6a and Figure 6b These are low-magnification and high-magnification SEM images of the nano-WC powder prepared in this embodiment, combined with... Figure 6a and Figure 6b It can be seen that the particle size of this nano WC powder is uniform, approximately 60 nm.

[0068] Example 4

[0069] This embodiment includes the following steps:

[0070] Step 1: At room temperature, place 37.5 mL of ethanol and 7.5 mL of deionized water on a magnetic stirrer and stir at 550 r / min for 8 min to mix thoroughly. Then slowly add 5 mL of oleic acid and continue stirring at 600 r / min for 10 min to obtain a homogeneous and transparent mixed solvent.

[0071] Step 2: Add 2.57g of sodium tungstate dihydrate to 50mL of the mixed solvent obtained in Step 1, and stir at 400r / min for 1h until completely dissolved to obtain transparent solution A;

[0072] Step 3: Dilute concentrated hydrochloric acid to a 0.2 mol / L transparent solution B, then add transparent solution B dropwise to the transparent solution A obtained in step 2 to adjust the pH to approximately 1.2, and transfer it to a 100 mL polytetrafluoroethylene reactor for homogeneous reaction at 140℃ for 18 h. Allow it to cool naturally to room temperature, remove the homogeneous reaction product, and wash it sequentially with anhydrous ethanol and deionized water, followed by centrifugation. Repeat the washing process 4 times, and then dry it in a freeze dryer at -45℃ and a vacuum of 30 Pa for 18 h to obtain yellow ultrafine nano-WO3 material.

[0073] Step 4: Reduce 8g of the ultrafine nano WO3 material obtained in Step 3 and adjust the oxygen vacancies. The reduction atmosphere is an inert gas with a hydrogen volume content of 70%. The heating rate of the reduction reaction is 8℃ / min, the temperature is 580℃, and the holding time is 2h. Highly active ultrafine WO2 nanomaterials with high oxygen vacancies are obtained.

[0074] Step 5: Grind and stir the ultrafine WO2 nanomaterials obtained in Step 4 with highly active carbon nanoparticles with a particle size of 60 nm until uniform to achieve uniform composite. The molar ratio of ultrafine WO2 nanomaterials to carbon source is 1:3.4 to obtain nanocomposite powder containing tungsten oxide and carbon.

[0075] Step 6: Place 8g of the tungsten oxide and carbon nanocomposite powder obtained in Step 5 into an alumina crucible with a length × width × height of 100mm × 40mm × 20mm, and place it in a low-temperature tube furnace for carbonization reaction. The protective atmosphere is argon, the heating rate is 15℃ / min, the temperature is 1250℃, and the holding time is 5h to obtain nano WC powder.

[0076] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing ultrafine nanoscale tungsten carbide powder, characterized in that, The method comprises the following steps: Step one, stirring and mixing ethanol and deionized water at room temperature, then slowly adding oleic acid and stirring to obtain a uniform transparent mixed solvent; Step two, adding tungsten salt into the mixed solvent obtained in step one and stirring until completely dissolved to obtain a transparent solution A; Step three, diluting concentrated acid into a transparent solution B, then adding the transparent solution B dropwise into the transparent solution A obtained in step two to adjust the pH, and transferring into a polytetrafluoroethylene reactor for homogeneous reaction, naturally cooling to room temperature, and vacuum freeze-drying to obtain yellow ultrafine nano WO3 material; Step four, reducing the ultrafine nano WO3 material obtained in step three and adjusting the oxygen vacancy to obtain ultrafine WO2 nano material with high activity and high oxygen vacancy; the reducing atmosphere used in the reducing reaction is inert gas with hydrogen content greater than 10%, the heating rate of the reducing reaction is 5-10 ℃ / min, the temperature is 500-700 ℃, and the holding time is 1-3 h; Step five, uniformly compounding the ultrafine WO2 nano material obtained in step four with a carbon source to obtain nano composite powder containing tungsten oxide and carbon; Step six, performing carbonization reaction on the nano composite powder containing tungsten oxide and carbon obtained in step five to obtain nano WC powder.

2. The method according to claim 1, wherein The volume ratio of ethanol to deionized water in step one is 5:1, and the volume ratio of oleic acid to the total volume of ethanol and deionized water is 1-5:

30.

3. The method according to claim 1, wherein the method is characterized by, The tungsten salt in step two is sodium tungstate dihydrate, and the concentration of the transparent solution A is 0.05-0.25 mol / L.

4. The method according to claim 1, wherein the method is characterized by, The concentrated acid in step three is concentrated hydrochloric acid, the concentration of the transparent solution B is 0.1-1 mol / L, the pH is 1-2, the temperature of the homogeneous reaction is 120-180 ℃, the reaction time is 10-24 h, the temperature of the vacuum freeze-drying is below -40 ℃, the vacuum degree is below 40 Pa, and the drying time is more than 8 h.

5. The method according to claim 1, wherein the method is characterized by, The carbon source in step five is high-activity carbon nanoparticles with a particle size of less than 100 nm, and the molar ratio of the ultrafine WO2 nano material to the carbon source is 1:3.0-3.

5.

6. The method according to claim 1, wherein the method is characterized by, The carbonization reaction in step six uses argon or nitrogen as the protective atmosphere, the heating rate is 5-20 ℃ / min, the temperature is 1100-1400 ℃, and the holding time is more than 3 h.

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