Nano tungsten carbide and preparation method thereof

Abstract

The invention provides nano tungsten carbide and a preparation method thereof, and belongs to the field of nano powder. The invention provides a preparation method of nano tungsten carbide, which comprises the following steps: introducing gaseous tungsten oxide obtained by gasifying tungsten oxide into an organic solvent to obtain dispersion liquid of nano tungsten oxide; mixing the dispersion liquid of the nano tungsten oxide with a construction agent, drying, and enabling the nano tungsten oxide to enter the carbon nanotubes to obtain a construction material; the construction agent comprises a carbon nano tube; and the construction material is subjected to reduction carbonization, and the nano tungsten carbide is obtained. Nanometer tungsten oxide prepared after sublimation of tungsten oxide has high activity and can be quickly adsorbed in the carbon nanotubes, so that preparation of the construction material is realized; and after the nano tungsten oxide is introduced into the carbon nano tube, the carbon nano tube limits the growth of powder particles in the reduction and carbonization process, so that the effect that the size of the powder is controllable is achieved.

Description

Technical Field

[0001] The invention relates to the field of nano powders, and in particular to nano tungsten carbide and a preparation method thereof. Background Art

[0002] Nano-tungsten carbide (WC) is a new functional material with high hardness, high thermal stability and high wear resistance. It breaks the shackles of traditional cemented carbide that cannot have both high hardness and high toughness, making nano-tungsten carbide powder have broad application prospects in tools, precision molds, drill bits and other fields.

[0003] As the main method for preparing nano-WC, the solid phase method has been widely used. The quality of nano-tungsten carbide prepared by the push boat process in the solid phase method is not high, mainly manifested in uneven particle size distribution, poor dispersibility, and small specific surface area. The quality of nano-tungsten carbide powder prepared by the rotary reduction method in the solid phase method is better and can increase the specific surface area of ​​nano-tungsten carbide, but the problem of uneven particle size distribution has not been well solved. Summary of the invention

[0004] The invention provides a nano tungsten carbide and a preparation method thereof. The nano tungsten carbide prepared by the invention has uniform particle size distribution.

[0005] The present invention provides a method for preparing nano tungsten carbide, comprising the following steps: The gaseous tungsten oxide is passed into an organic solvent to obtain a dispersion of nano tungsten oxide; The dispersion of the nano-tungsten oxide is mixed with a building agent and then dried, so that the nano-tungsten oxide enters the interior of the carbon nanotubes to obtain a building material; the building agent includes carbon nanotubes; The building material is reduced and carbonized to obtain the nano tungsten carbide.

[0006] Preferably, the mass ratio of the nano-tungsten oxide to the carbon nanotubes is 5-15:1.

[0007] Preferably, the structuring agent is a slurry; The slurry includes carbon black, phenolic resin, carbon nanotubes and ethanol; The mass ratio of the carbon nanotubes to the carbon black is 3 to 9:1; The mass ratio of the carbon nanotubes to the phenolic resin is 2-10:1.

[0008] Preferably, the structuring agent is a solid containing a porous structure; The preparation method of the structuring agent comprises the following steps: The carbon black, phenolic resin and carbon nanotubes are mixed, pressed and sintered to obtain the building agent.

[0009] Preferably, the reduction carbonization is carried out in a rotary reduction furnace; The reduction carbonization temperature is 800-1000° C., and the insulation time is 30-60 minutes.

[0010] Preferably, the reduction carbonization is carried out in a tube furnace; The reduction carbonization temperature is 800-1000° C., and the insulation time is 60-90 minutes.

[0011] Preferably, after the reduction and carbonization, the process further comprises: The product obtained by reduction and carbonization is quenched, separated and dried to obtain a tungsten carbide preform; The tungsten carbide preform is passivated and crushed to obtain the nano tungsten carbide.

[0012] Preferably, the quenching agent used for quenching includes ethanol, water or liquid nitrogen; The quenching is carried out under stirring conditions, and the quenching time is 60 to 120 minutes.

[0013] Preferably, the passivation is carried out in a hydrogen atmosphere; the passivation temperature is 1100-1200° C., and the time is 20-90 min.

[0014] The present invention also provides nano tungsten carbide prepared by the preparation method described in the above technical solution.

[0015] The present invention utilizes the high activity of nano tungsten oxide prepared by sublimation of tungsten oxide, and can quickly adsorb it inside the carbon nanotubes, thereby realizing the preparation of the building material; and after the nano tungsten oxide is introduced into the carbon nanotubes, the carbon nanotubes limit the growth of powder particles during the reduction and carbonization process, achieving the effect of controllable powder size, so that the prepared tungsten carbide particle size distribution is more uniform.

[0016] In addition, the nano-tungsten oxide prepared by sublimation in the present invention has high activity, which is conducive to its rapid entry into the interior of the carbon nanotubes. Therefore, there is no need to perform additional treatment on the carbon nanotubes to improve the activity of the carbon nanotubes to achieve the adsorption of the nano-tungsten oxide by the carbon nanotubes, thereby improving the efficiency of subsequent processes and facilitating the realization of large-scale industrialization.

[0017] Furthermore, the problem of separation of tungsten oxide and carbon black often occurs during the preparation of nano-tungsten carbide by reduction carbonization, resulting in the problem of carbon deficiency and excessive free carbon in the prepared nano-tungsten carbide, and the final nano-tungsten carbide is of low quality. In the present invention, a slurry of carbon black and phenolic resin is first prepared or carbon black, phenolic resin and carbon nanotubes are prepared into a porous block, so that the slurry is fully attached to the surface of nano-tungsten oxide or nano-tungsten oxide enters the pores, which can avoid the abnormal growth caused by the contact between nano-tungsten oxide particles in the subsequent reduction and oxidation process, and can also avoid the formation of nano-tungsten carbide wires, resulting in the inability to prepare powder particles. Therefore, the presence of carbon black and phenolic resin can, on the one hand, provide a reducing agent and a carbon source, and on the other hand, can isolate the nano-tungsten oxide particles in the carbon nanotube adsorbent and the adsorbent from each other, greatly reducing the growth of powder particles caused by the gas phase migration process.

[0018] Furthermore, due to the high temperature resistance of carbon nanotubes, they adhere to the surface of tungsten carbide particles, so they need to be removed, otherwise composite particles will be formed, reducing the quality of nano tungsten carbide. In the present invention, the mixture after reduction and carbonization is quenched, separated and passivated, and the residual carbon nanotubes are fully removed, ensuring the quality of the prepared nano tungsten carbide.

[0019] In summary, the method for preparing nano-tungsten carbide adopted in the present invention can effectively solve the problems of uneven particle size distribution and small specific surface area of ​​tungsten carbide powder prepared by traditional processes, and finally achieves the technical effect of controllable particle size of nano-tungsten carbide powder. The prepared nano-tungsten carbide has complete crystal form, complete carbonization, and less free carbon. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a flow chart of preparing nano tungsten carbide according to an embodiment of the present invention; Figure 2 This is a SEM image of the nano-tungsten carbide prepared in Example 1; Figure 3 This is a comparison chart of the particle size distribution of nano-tungsten carbide prepared in Example 2 and Comparative Example 1. DETAILED DESCRIPTION

[0021] The present invention provides a method for preparing nano tungsten carbide, comprising the following steps: The gaseous tungsten oxide is passed into an organic solvent to obtain a dispersion of nano tungsten oxide; The dispersion of the nano-tungsten oxide is mixed with a building agent and then dried, so that the nano-tungsten oxide enters the interior of the carbon nanotubes to obtain a building material; the building agent includes carbon nanotubes; The building material is reduced and carbonized to obtain the nano tungsten carbide.

[0022] In the present invention, unless otherwise specified, the raw materials used are commercially available products well known in the art.

[0023] The invention introduces gaseous tungsten oxide into an organic solvent to obtain a dispersion of nano tungsten oxide.

[0024] In the present invention, the gasification temperature is preferably 850°C.

[0025] In the present invention, the gaseous tungsten oxide is preferably introduced into an organic solvent under the drive of argon gas; the organic solvent preferably includes ethanol.

[0026] In the present invention, the introducing is preferably carried out under stirring, and the stirring time is preferably 30 to 90 min. In a specific embodiment of the present invention, the stirring time can be 30 min, 40 min, 50 min, 60 min, 70 min, 80 min or 90 min.

[0027] The nano-tungsten oxide obtained by sublimation has high activity.

[0028] After obtaining the dispersion of nano tungsten oxide, the present invention mixes the dispersion of nano tungsten oxide with a building agent and then dries the mixture, so that the nano tungsten oxide enters the interior of the carbon nanotubes to obtain a building material.

[0029] In the present invention, the mass ratio of the nano-tungsten oxide to the carbon nanotubes is preferably 5-15:1. In a specific embodiment of the present invention, the mass ratio of the nano-tungsten oxide to the carbon nanotubes can be 5:1, 8:1, 10:1, 12:1 or 15:1.

[0030] In the present invention, the structuring agent is preferably a slurry or a solid containing a porous structure.

[0031] When the building agent is a slurry, the slurry preferably includes carbon black, phenolic resin, carbon nanotubes and ethanol; the mass ratio of the carbon nanotubes to the carbon black is preferably 3-9:1, and in a specific embodiment of the present invention, the mass ratio of the carbon nanotubes to the carbon black can be 3:1, 4:1, 5:1, 5:1, 7:1, 8:1 or 9:1; the mass ratio of the carbon nanotubes to the phenolic resin is preferably 2-10:1, and in a specific embodiment of the present invention, the mass ratio of the carbon nanotubes to the phenolic resin can be 2:1, 3:1, 4:1, 5:1, 5:1, 7:1, 8:1, 9:1 or 10:1; the mass ratio of the carbon nanotubes to the ethanol is preferably 1:2-5, and in a specific embodiment of the present invention, the mass ratio of the carbon nanotubes to the ethanol can be 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1 or 5:1.

[0032] When the structuring agent is preferably a solid containing a porous structure; the preparation method of the structuring agent preferably comprises the following steps: The carbon black, phenolic resin and carbon nanotubes are mixed, pressed and sintered to obtain the building agent.

[0033] In the present invention, the molding pressure is preferably 180~200MPa. In a specific embodiment of the present invention, the molding pressure may be 180MPa, 190MPa or 200MPa. The sintering temperature is preferably 800~900℃, and the time is preferably 25~45min. In a specific embodiment of the present invention, the sintering temperature may be 800℃, 820℃, 850℃, 880℃ or 900℃, and the time may be 25min, 30min, 35min, 40min or 45min.

[0034] After sintering, a porous structure is formed.

[0035] In the present invention, when the structuring agent is a slurry, the mixing is preferably carried out under stirring, and the mixing time is preferably 60 to 120 minutes. In a specific embodiment of the present invention, the mixing time can be 60 minutes, 70 minutes, 80 minutes, 90 minutes, 100 minutes, 110 minutes or 120 minutes.

[0036] In the present invention, when the structuring agent is a solid containing a porous structure, the mixing is preferably carried out under ultrasonic conditions, and the mixing time is preferably 30 to 120 minutes. In a specific embodiment of the present invention, the mixing time can be 30 minutes, 50 minutes, 80 minutes, 100 minutes or 120 minutes.

[0037] After obtaining the building material, the present invention reduces and carbonizes the building material to obtain the nano-tungsten carbide.

[0038] In the present invention, the reduction carbonization is preferably carried out in a mixed gas of carbon monoxide and hydrogen or in carbon monoxide.

[0039] In the present invention, when the structuring agent is a slurry, the reduction carbonization is preferably carried out in a rotary reduction furnace; In the present invention, the rotary reduction furnace preferably includes a first temperature zone, a second temperature zone, a third temperature zone, a fourth temperature zone, a fifth temperature zone and a sixth temperature zone from the furnace head to the furnace tail; the temperature of the first temperature zone is preferably 850-880°C; the temperature of the second temperature zone is preferably 880-910°C; the temperature of the third temperature zone is preferably 910-930°C; the temperature of the fourth temperature zone is preferably 930-950°C; the temperature of the fifth temperature zone is preferably 980-1000°C; the temperature of the sixth temperature zone is preferably 980-1080°C; the rotation speed of the material in the rotary reduction furnace is preferably 3-6r / min; in the specific embodiment of the present invention, In the embodiment, the temperature of the first temperature zone can be 850℃, 860℃, 870℃ or 880℃; the temperature of the second temperature zone can be 880℃, 890℃, 900℃ or 910℃; the temperature of the third temperature zone can be 910℃, 920℃ or 930℃; the temperature of the fourth temperature zone can be 930℃, 940℃ or 950℃; the temperature of the fifth temperature zone can be 980℃, 990℃ or 1000℃; the temperature of the sixth temperature zone can be 980℃, 1000℃ or 1080℃; the rotation speed of the material in the rotary reduction furnace can be 3r / min, 4r / min, 5r / min or 6r / min.

[0040] In the present invention, the insulation time for the reduction carbonization is preferably 30 to 60 minutes. In a specific embodiment of the present invention, the insulation time for the reduction carbonization can be 30 minutes, 40 minutes, 50 minutes or 60 minutes.

[0041] In the present invention, when the structuring agent is a solid containing a porous structure, the reduction carbonization is preferably carried out in a tubular furnace; The temperature of the reduction carbonization is preferably 800-1000°C, and the insulation time is preferably 60-90 min. In a specific embodiment of the present invention, the temperature of the reduction carbonization can be 800°C, 820°C, 840°C, 860°C, 880°C, 900°C, 950°C or 1000°C, and the insulation time can be 60 min, 70 min, 80 min or 90 min.

[0042] In the present invention, after the reduction and carbonization, it is preferred to further include: The product obtained by reduction and carbonization is quenched, separated and dried to obtain a tungsten carbide preform; The tungsten carbide preform is passivated and crushed to obtain the nano tungsten carbide.

[0043] In the present invention, the quenching agent used for the quenching preferably includes ethanol, water or liquid nitrogen, the quenching is preferably carried out under stirring, and the quenching time is preferably 60 to 120 minutes. In a specific embodiment of the present invention, the quenching time can be 60 minutes, 70 minutes, 80 minutes, 90 minutes, 100 minutes, 110 minutes or 120 minutes.

[0044] In the present invention, the passivation is preferably carried out in a hydrogen atmosphere; the passivation temperature is preferably 1100-1200°C, and the time is preferably 20-90 min. In a specific embodiment of the present invention, the passivation temperature may be 1100°C, 1120°C, 1140°C, 1160°C, 1180°C or 1200°C, and the time may be 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min or 90 min.

[0045] The present invention also provides nano tungsten carbide prepared by the preparation method described in the above technical solution.

[0046] Figure 1 Flow chart of preparing nano tungsten carbide according to the embodiment of the present invention: The tungsten oxide is gasified and sublimated to obtain nano tungsten oxide; the nano tungsten oxide ingredients are assembled to obtain the building material; the building material is reduced and carbonized to obtain a mixed material; the mixed material is quenched and passivated to obtain nano tungsten carbide.

[0047] The nano-tungsten carbide and the preparation method thereof provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0048] The preparation method of structuring agent A in the embodiment is: 100 g of carbon nanotubes, 20 g of carbon black, 20 g of phenolic resin (BR2123F from Henan Borun New Materials Co., Ltd.) and 500 mL of ethanol were mixed to obtain a building agent A.

[0049] The preparation method of the structuring agent B in the embodiment is: 100 g of carbon nanotubes, 20 g of carbon black and 20 g of phenolic resin (BR2123F from Henan Borun New Materials Co., Ltd.) were mixed and molded under a pressure of 200 MPa to obtain a precursor; The precursor was sintered at 900° C. for 30 min to obtain a structuring agent B.

[0050] Preparation method 1 1. Gasify and sublimate 1000g of tungsten oxide at 850℃, and use argon to pass the sublimated tungsten oxide into 2000mL of ethanol for stirring for 30-90min to obtain nano tungsten oxide dispersion; 2. Add structuring agent A to the dispersion in step 1 and stir to mix for 60 to 120 minutes. After stirring, dry to obtain the structuring material; 3. The building materials described in step 2 are sent into a rotary kiln for reduction and carbonization. The temperatures of the six temperature zones from the furnace head to the furnace tail are 880°C, 910°C, 930°C, 930°C, 990°C, and 990°C, respectively. The material speed is 5r / min, and the time is 30-60min. After the insulation is completed, a mixed material is obtained; 4. Quench the mixture in step 3 in liquid nitrogen, stir and centrifuge for 60 to 120 minutes, filter and dry to obtain a tungsten carbide preform. 5. Use a molybdenum wire furnace to passivate the tungsten carbide preform in step 4 under a hydrogen atmosphere, and obtain nano-tungsten carbide after crushing. The passivation temperature is 1100 ~ 1200 ° C, the passivation time is 20min ~ 90min, and the BET of nano-tungsten carbide is 4.0 ~ 4.5 m 2 / g.

[0051] Preparation method 2 1. Gasify and sublimate 1000g of tungsten oxide at 850℃, and use argon to pass the sublimated tungsten oxide into 2000mL of ethanol for stirring for 30-90min to obtain nano tungsten oxide dispersion; 2. Add building agent B to the dispersion in step 1 and perform ultrasonication for 30 to 120 min. After ultrasonication, dry to obtain a building material. 3. The coated material in step 2 is sent into a tubular furnace for reduction and carbonization at a temperature of 800-1000° C. for 90 min, and a mixed material is obtained after the insulation is completed; 4. Quench the mixture in step 3 in liquid nitrogen, stir and centrifuge for 60 to 120 minutes, filter and dry to obtain a tungsten carbide preform. 5. Use a molybdenum wire furnace to passivate the tungsten carbide preform in step 4 under a hydrogen atmosphere, and obtain nano-tungsten carbide after crushing. The passivation temperature is 1100~1200℃, the passivation time is 20~90min, and the BET of nano-tungsten carbide is 4.0~4.5 m 2 / g.

[0052] Preparation parameters of Examples 1 to 5 and BET properties of nano-tungsten carbide

[0053] Comparative Example 1 1. Load ammonium metatungstate into an alumina crucible and calcine in a muffle furnace at a temperature of 750°C for 6 h to obtain WO3 Aggregates; 2. Use air jet mill to grind the WO obtained in step 1 3 The aggregates were crushed for 45 min and the air flow rate was 180 m 3 / h, gas pressure 0.05 MPa, the crushed WO 3 (particle size <0.5μm) and high purity carbon black (purity 99.95%, carbon black quality WO 3 The mass is 6.2%) and the vertical plowshare mixing is carried out to obtain WO 3 Mixed with carbon black; 3. Use WO 3 After mixing with carbon black mixture and solvent, spray granulation and room temperature second drying are carried out to make WO in step 2 3 Spray granulation with carbon black slurry to obtain a spherical mixture; 4. A rotary reduction furnace with six temperature zones is used to reduce and carbonize the spherical mixture in step 3 under the protection of inert gas. The temperatures of the six temperature zones from the furnace head to the furnace tail are 880°C, 910°C, 930°C, 930°C, 990°C, and 990°C, respectively. The rotation speed of the material is 5r / min, and the time from feeding to discharging is 40 min. The chemical composition is W+WC+W 2 Pre-carbonized material of C; 5. Use a molybdenum wire furnace to passivate the pre-carbonized material in step 4 in hydrogen gas. After passivation, nano-tungsten carbide with complete grains and uniform distribution is obtained. The passivation temperature is 1450°C and the passivation time is 20 minutes. Finally, the specific surface area of ​​the nano-tungsten carbide powder is 3.98m 2 / g.

[0054] Comparative Example 2 1. Put WO 3 Put it into a cylindrical mold with a size of φ20*100 mm, and use an isostatic press to press it with a pressure of 200 MPa and a holding time of 5 minutes to obtain a tungsten oxide compact; 2. The tungsten oxide pressed embryo is sent into an acetylene-oxygen flame at 2500°C (the volume ratio of acetylene to oxygen is 2:5, and the flow rate of acetylene is 3L / min) to instantly gasify the tungsten oxide to obtain tungsten oxide vapor; the obtained tungsten oxide vapor is introduced into a condensation collection device using nitrogen (flow rate is 9L / min), wherein the temperature of the condensation collection device is 5°C and the receiving time is 1h; after the tungsten oxide homogeneously nucleates and grows, the tungsten oxide vapor is condensed to form nano tungsten oxide particles, and the specific surface area of ​​the obtained nano tungsten oxide particles is 16.76m 2 / g; 3. The obtained nano-tungsten oxide particles are reduced in a carbon monoxide reduction furnace at a temperature of 650°C for 45 minutes to obtain nano-tungsten powder with complete grains and uniform distribution; 4. Place the obtained nano-tungsten powder and carbon black in a mixer and stir and mix them for 6 hours to obtain a mixed powder, in which the mass percentage of carbon black is 6.115%; carbonize the mixed powder in a carbonization furnace at a temperature of 900°C and a holding time of 90 minutes to obtain nano-tungsten carbide with complete grains and uniform distribution, and its specific surface area is 4.14m 2 / g.

[0055] Comparative Example 3 1. Modification of carbon nanotubes: 10 g of carbon nanotubes were placed in 100 mL of concentrated nitric acid with a mass concentration of 68%, and ultrasonically dispersed at 80 ° C for 30 min, and then refluxed at 90 ° C for 1-5 h. After cooling to room temperature, the powder was diluted with deionized water and filtered to neutrality, and then the powder was placed in a vacuum drying oven at 90 ° C for 5 h to obtain modified carbon nanotubes.

[0056] 2. Weigh the modified carbon nanotubes (3% of the mass content of the ammonium paratungstate solution) and mix with the ammonium paratungstate solution, add monohydrated citric acid and polyethylene glycol reagent (the amount of both dissolved is 1% of the volume of the mixed solution), stir thoroughly, then add formic acid to the solution until the pH value of the solution is 3, then place the solution in a constant temperature stirrer, stir at a stirring temperature of 70°C and a stirring speed of 30r / min for 40 hours to form a sol. Place the sol in a 200°C vacuum drying oven for 10 hours to prepare a gel, grind the gel into powder, and pass through a 300-mesh sieve.

[0057] 3. The ground and sieved gel was placed in a reduction furnace, and flowing hydrogen with a purity of 99.99% was used as the reducing carrier gas with a hydrogen flow rate of 280 mL / min. After reduction at 700°C for 5 hours, the gel was cooled in the furnace to prepare a carbon nanotube / nano-tungsten powder composite powder material with a carbon nanotube volume content of 12%.

[0058] 4. Grind and crush the carbon nanotube / nano tungsten powder composite powder material, centrifuge it after crushing, and use a molybdenum wire furnace for passivation treatment at a temperature of 1000°C for 50 minutes to obtain nano tungsten carbide with a BET of 4.0 g / cm 3 .

[0059] Comparative Example 4 1. Take tungsten powder with an average particle size of 100 nm as raw material, dissolve alcohol-soluble phenolic resin in anhydrous ethanol to prepare 0.5 g / mL phenolic resin ethanol solution, add 300 mL of the above phenolic resin ethanol solution to each kg of nano-W powder, treat in an ultrasonic dispersion device for 3 hours, stir at the same time, then heat the slurry to 100 ° C to volatilize the anhydrous ethanol, and obtain a mixture of phenolic resin-coated nano-W particles; 2. Carbonize the mixture in a vacuum furnace at 950°C for 60 min and a vacuum degree of 200 Pa to obtain nano WC powder with an average particle size of 118 nm and a carbon content of 8.72%; 3. The high carbon content nano WC powder obtained by vacuum carbonization was heated in a tube furnace at H 2 Heat treatment in atmosphere, treatment temperature 950℃, treatment time 60min, H 2 The flow rate was 2.0 L / min, and the BET of the obtained nano WC powder was 3.5 m 2 / g, and the carbon content is 6.15%.

[0060] Figure 2 This is the SEM image of the nano-tungsten carbide prepared in Example 1.

[0061] Depend on Figure 2 It can be seen that the nano-tungsten carbide prepared by the present invention is of high quality: the nano-tungsten carbide powder has complete crystal form, is fully carbonized, has less free carbon, and has a concentrated particle size distribution.

[0062] Figure 3 This is a comparison chart of the particle size distribution of nano-tungsten carbide prepared in Example 2 and Comparative Example 1.

[0063] Depend on Figure 3 It can be seen that the particle size distribution of the nano-tungsten carbide prepared by the construction method of the present invention is more concentrated, while the particle size distribution of the nano-tungsten carbide powder prepared by the existing method is wider. When carrying out industrial batch production, this method can effectively improve the quality of the prepared nano-tungsten carbide powder, which is manifested in that the particle size of the powder is controllable, and the powder produced does not need to be processed by batching to meet the requirements of use, which can shorten the process flow and generate more economic benefits. At the same time, the final nano-tungsten carbide powder product has a complete crystal form, complete carbonization, and less free carbon.

[0064] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing nano tungsten carbide, characterized in that: The following steps are involved: The gaseous tungsten oxide is passed into an organic solvent to obtain a dispersion of nano tungsten oxide; The dispersion of the nano-tungsten oxide is mixed with a building agent and then dried, so that the nano-tungsten oxide enters the interior of the carbon nanotubes to obtain a building material; the building agent includes carbon nanotubes; The building material is reduced and carbonized to obtain the nano tungsten carbide.

2. The preparation method according to claim 1, characterized in that: The mass ratio of the nano-tungsten oxide to the carbon nanotubes is 5-15:

1.

3. The preparation method according to claim 1 or 2, characterized in that: The structuring agent is a slurry; The slurry includes carbon black, phenolic resin, carbon nanotubes and ethanol; The mass ratio of the carbon nanotubes to the carbon black is 3 to 9:1; The mass ratio of the carbon nanotubes to the phenolic resin is 2-10:

1.

4. The preparation method according to claim 1 or 2, characterized in that: The structuring agent is a solid containing a porous structure; The preparation method of the structuring agent comprises the following steps: The carbon black, phenolic resin and carbon nanotubes are mixed, pressed and sintered to obtain the building agent.

5. The preparation method according to claim 3, characterized in that: The reduction and carbonization is carried out in a rotary reduction furnace; The reduction carbonization temperature is 800-1000° C., and the insulation time is 30-60 minutes.

6. The preparation method according to claim 4, characterized in that: The reduction carbonization is carried out in a tubular furnace; The reduction carbonization temperature is 800-1000° C., and the insulation time is 60-90 minutes.

7. The preparation method according to claim 1, characterized in that: After the reduction and carbonization, the method further comprises: The product obtained by reduction and carbonization is quenched, separated and dried to obtain a tungsten carbide preform; The tungsten carbide preform is passivated and crushed to obtain the nano tungsten carbide.

8. The preparation method according to claim 7, characterized in that: The quenching agent used in the quenching includes ethanol, water or liquid nitrogen; The quenching is carried out under stirring conditions, and the quenching time is 60 to 120 minutes.

9. The preparation method according to claim 7, characterized in that: The passivation is carried out in a hydrogen atmosphere; the passivation temperature is 1100-1200° C., and the time is 20-90 minutes.

10. Nano-tungsten carbide prepared by the preparation method according to any one of claims 1 to 9.

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