A method for preparing high-purity tungsten powder by vacuum induction sublimation of WO3 coupled with plasma hydrogen reduction.

Abstract

This invention discloses a method for preparing high-purity tungsten powder by vacuum induction sublimation of WO3 coupled with plasma hydrogen reduction, belonging to the field of metal powder preparation technology. The method includes six steps: raw material pretreatment, loading and atmosphere construction, vacuum induction sublimation, plasma hydrogen reduction, gas-phase condensation and collection, and tail gas circulation purification. This invention solves the problems of incomplete impurity separation, easy residue of intermediate products, difficulty in achieving high purity levels, and lengthy production processes in traditional solid-phase reduction or melt evaporation processes. It achieves synergy between gas-phase purification and gas-phase reduction, obtaining ultra-high purity tungsten powder with uniform particle size. It also solves the problems of insufficient hydrogen reduction activity, incomplete reduction, and high reaction energy consumption in traditional processes, achieving efficient and deep reduction of WO3 vapor and eliminating intermediate product residue. Furthermore, it solves the problems of uneven particle size distribution, high subsequent processing costs, and high waste gas emissions associated with traditional processes.

Description

Technical Field

[0001] This invention belongs to the field of metal powder preparation technology, specifically relating to a method for preparing high-purity tungsten powder by vacuum induction sublimation of WO3 coupled with plasma hydrogen reduction. Background Technology

[0002] Tungsten, a rare metal with a high melting point, high hardness, and corrosion resistance, plays an irreplaceable role in high-end manufacturing fields such as semiconductor targets, aerospace, nuclear fusion, and high-end electronic devices. With the increasing demands of modern industry for material purity and particle size uniformity, developing high-purity, ultrafine-particle-size, and simple-process tungsten powder preparation technology has become an important research direction in this field.

[0003] Currently, the mainstream industrial process for preparing tungsten powder is the ammonium paratungstate hydrogen reduction method. This process requires multiple steps, including crystallization, calcination, and multi-stage hydrogen reduction, resulting in a lengthy process, long production cycle, high energy consumption, and easy residue of impurities, making it difficult to produce ultra-high purity tungsten powder. Furthermore, while the direct tungsten oxide hydrogen reduction process shortens some steps, the reactivity of tungsten oxide with hydrogen is limited, leading to incomplete reduction and the presence of residual intermediate products. It also cannot separate high-boiling-point impurities from tungsten oxide, thus limiting purity. The vacuum evaporation and reduction coupling process uses electron beam heating to melt and evaporate tungsten oxide, achieving some impurity separation. However, it does not utilize the sublimation properties of tungsten oxide, still requiring high-temperature heating to a molten state, resulting in high energy consumption, uneven evaporation, and easy decomposition. Additionally, conventional hydrogen reduction capacity is insufficient, and the equipment structure is complex and costly, making large-scale production difficult.

[0004] In summary, the core bottlenecks of existing tungsten powder preparation technologies are: failure to utilize the high volatility of tungsten oxide at high temperatures, still employing solid-phase reduction or high-temperature melting evaporation methods, resulting in significant energy waste; incomplete impurity separation, making it difficult to meet the purity requirements of high-end applications; low reduction efficiency and long production cycles; difficulty in particle size control and high subsequent processing costs; and poor equipment adaptability, hindering large-scale implementation. Therefore, a new method for preparing high-purity tungsten powder that can simultaneously achieve efficient impurity separation and deep reduction, while also being energy-efficient, having a short process, and controllable particle size is urgently needed. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention aims to provide a method for preparing high-purity tungsten powder by vacuum induction sublimation of WO3 coupled with plasma hydrogen reduction. This method solves the problems of incomplete impurity separation, easy residue of intermediate products, difficulty in achieving high purity levels, and lengthy production processes in traditional solid-phase reduction or melt evaporation processes. It achieves synergy between gas-phase purification and gas-phase reduction, resulting in ultra-high purity tungsten powder with uniform particle size. The specific solution is as follows: This application provides a method for preparing high-purity tungsten powder by vacuum induction sublimation of WO3 coupled with plasma hydrogen reduction, including the following steps: S1. Raw material pretreatment: Obtain industrial pure WO3 raw material, remove adsorbed water by heat preservation and drying, and obtain dry WO3 powder; S2. Charging and Atmosphere Construction: Dry WO3 powder is loaded into a graphite crucible and placed in an induction coil. After sealing the furnace cavity, the vacuum system is started to adjust the pressure inside the furnace, thus obtaining the WO3 charge to be sublimated. S3, Vacuum Induction Sublimation: The WO3 charge to be sublimated is induction heated to raise the temperature, the temperature inside the furnace is controlled, and the induction power is adjusted in real time according to the WO3 sublimation rate. WO3 vapor enters the hydrogen plasma reduction zone through the guide channel, and the unsublimated impurities remain at the bottom of the graphite crucible, thus obtaining the separated WO3 vapor. S4. Plasma hydrogen reduction: A hydrogen-argon mixed plasma gas is introduced into the hydrogen plasma reduction zone. The radio frequency plasma generator is started to excite the hydrogen gas to form hydrogen plasma. The pressure in the reduction zone is controlled so that the separated WO3 vapor and the hydrogen plasma undergo a gas-phase reduction reaction to generate tungsten vapor. S5. Gas-phase condensation and collection: Tungsten vapor is introduced into a water-cooled collector for condensation to obtain high-purity tungsten powder; S6. Tail gas recirculation and purification: The tail gas produced by the reduction reaction is collected, and after being purified by condensation and dehydration and molecular sieve adsorption, it is circulated into the hydrogen plasma reduction zone to obtain a recirculating hydrogen-argon mixture.

[0006] In one embodiment, in step S1, the drying temperature is controlled at 110-130°C and the heat preservation time is controlled at 4-8 hours; the purity of the industrial pure WO3 raw material is ≥99.95%.

[0007] In one embodiment, in step S2, the graphite crucible is made of high-purity graphite and is equipped with a perforated crucible lid; the pressure inside the furnace is controlled at 500-1000 Pa.

[0008] In one embodiment, in step S3, the furnace temperature is controlled at 950–1050°C, the induction power is controlled at 20–40 kW, and the WO3 sublimation rate is controlled at 0.5–2.0 kg / h.

[0009] In one embodiment, in step S3, the flow channel is made of high-purity graphite.

[0010] In one embodiment, in step S4, the hydrogen content in the hydrogen-argon mixed plasma gas is 20%, and the gas flow rate is controlled at 0.1–1 Nm³. 3 / h, the pressure in the reduction zone is controlled at 50-200Pa; the hydrogen purity is ≥99.999%.

[0011] In one embodiment, in step S5, the temperature of the water-cooled collector is controlled at ≤80°C.

[0012] In one embodiment, in step S5, the water-cooled collector is a water-cooled capillary collector. Beneficial effects

[0013] (1) This invention uses a one-step coupling process of vacuum induction sublimation of WO3 coupled with plasma hydrogen reduction to enable WO3 vapor to simultaneously complete impurity separation and deep reduction in the gas phase state. This solves the problems of incomplete impurity separation, easy residue of intermediate products, difficulty in achieving high purity and lengthy production process in traditional solid phase reduction or melt evaporation processes. It achieves synergy between gas phase purification and gas phase reduction to obtain high-purity tungsten powder with ultra-high purity and uniform particle size. (2) This invention controls the weak oxidizing atmosphere in the furnace and the radio frequency plasma to excite hydrogen to form hydrogen plasma, so that WO3 vapor and hydrogen plasma can fully contact each other in the low-pressure reduction zone to carry out gas phase reduction reaction. This solves the problems of insufficient hydrogen reduction activity, incomplete reduction and high reaction energy consumption in traditional hydrogen reduction, and realizes efficient and deep reduction of WO3 vapor, eliminating intermediate product residue. (3) The present invention uses a water-cooled collector to quickly condense and collect tungsten vapor, and combines tail gas condensation and dehydration with molecular sieve purification and recycling processes to solve the problems of uneven particle size distribution, high subsequent processing costs and large waste gas emissions in traditional processes. It realizes the direct molding of ultrafine tungsten powder and the recycling of hydrogen, reduces production costs and reduces environmental pollution. Attached Figure Description

[0014] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0015] Figure 1 The preparation flow chart provided by the present invention; Figure 2 The preparation structure diagram provided by the present invention; Figure 3 The morphology diagram of the high-purity tungsten powder provided by this invention.

[0016] In the diagram: 1. Vacuum system; 2. Induction heating system; 3. Radio frequency plasma generation system; 4. Hydrogen and argon plasma gas; 5. Tungsten oxide powder; 6. Graphite crucible; 7. Induction coil; 8. Condenser; 9. Powder collector; 10. Exhaust pump. Detailed Implementation

[0017] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0018] Traditional tungsten powder preparation processes often focus on solid-phase reduction or high-temperature melting and evaporation, which do not make full use of the physical properties of WO3 at high temperatures and high volatility above 800℃. This results in incomplete impurity separation, difficulty in achieving purity levels above 5N, long production cycles, and high energy consumption. Some processes only use single hydrogen reduction or electron beam heating, failing to form a synergistic system of gas-phase sublimation and gas-phase reduction, making it difficult to achieve large-scale preparation of ultra-high purity tungsten powder of 5N grade and above.

[0019] To address the aforementioned problems, this invention provides a method for preparing high-purity tungsten powder by vacuum induction sublimation of WO3 coupled with plasma hydrogen reduction. By coupling vacuum induction sublimation and plasma hydrogen reduction in one step, efficient separation of WO3 from high-boiling-point impurities and deep reduction of WO3 vapor are achieved, constructing a synergistic system of gas-phase purification and gas-phase reduction, improving the purity and particle size uniformity of tungsten powder, and reducing energy consumption and production cycle.

[0020] This application provides a method for preparing high-purity tungsten powder by vacuum induction sublimation of WO3 coupled with plasma hydrogen reduction, comprising the following steps: S1. Raw Material Pretreatment: Obtain industrial-grade pure WO3 raw material, and remove adsorbed water through heat preservation and drying to obtain dry WO3 powder. The purpose of this step is to remove adsorbed water from the raw material, prevent moisture from evaporating in a vacuum environment and affecting the pressure stability inside the furnace, and at the same time prevent moisture from reacting with high-temperature WO3 and introducing impurities.

[0021] S2. Charging and Atmosphere Construction: Dry WO3 powder is charged into a graphite crucible 6 and placed in an induction coil 7. After sealing the furnace cavity, the vacuum system 1 is activated to adjust the pressure inside the furnace, thus obtaining the WO3 charge to be sublimated. The purpose of this step is to create a weakly oxidizing atmosphere, suppress the thermal decomposition of WO3 during the heating process, and at the same time promote the stable escape and transport of WO3 vapor.

[0022] S3. Vacuum Induction Sublimation: The WO3 charge to be sublimated is induction heated to raise the temperature, the furnace temperature is controlled, and the induction power is adjusted in real time according to the WO3 sublimation rate. After the tungsten oxide powder 5 is sublimated, the WO3 vapor enters the hydrogen plasma reduction zone through the guide channel, and the unsublimated impurities remain at the bottom of the graphite crucible 6, resulting in separated WO3 vapor. The purpose of this step is to utilize the high-temperature and high-volatility physical properties of WO3 above 800℃, combined with vacuum conditions, to achieve efficient sublimation of WO3 and simultaneously separate WO3 from high-boiling-point impurities.

[0023] S4. Hydrogen Plasma Reduction: Hydrogen-argon plasma gas 4 is introduced into the hydrogen plasma reduction zone. The radio frequency plasma generation system 3 is activated to excite hydrogen gas to form hydrogen plasma. The pressure in the reduction zone is controlled so that the separated WO3 vapor undergoes a gas-phase reduction reaction with the hydrogen plasma. The reaction formula is as follows: This process generates tungsten vapor. The purpose of this step is to utilize the high temperature and strong reducing activity of hydrogen plasma to achieve a one-step deep reduction of WO3 vapor, avoiding the residue of intermediate products.

[0024] S5. Vapor-phase condensation and collection: Tungsten vapor is introduced into condenser 8 for condensation. The tungsten vapor rapidly condenses on the surface of condenser 8 to form ultrafine tungsten powder. The ultrafine tungsten powder falls into powder collector 9 under negative pressure suction, obtaining high-purity tungsten powder. The purpose of this step is to crystallize tungsten vapor through rapid condensation to obtain ultrafine tungsten powder with uniform particle size.

[0025] S6. Tail Gas Recirculation and Purification: The tail gas generated by the reduction reaction is discharged through exhaust pump 10, condensed and dehydrated by a 0-10℃ condenser, and then purified by molecular sieve adsorption before being recycled into the hydrogen plasma reduction zone to obtain a recycled hydrogen-argon mixture. The purpose of this step is to achieve the recycling of hydrogen, reduce production costs, and reduce waste gas emissions.

[0026] In one embodiment, in step S1, the heat preservation and drying temperature is controlled at 110-130°C, the heat preservation time is controlled at 4-8 hours, and the purity of the industrial pure WO3 raw material is ≥99.95%.

[0027] In one embodiment, in step S2, the graphite crucible 6 is made of high-purity graphite and is equipped with a perforated crucible lid, and the pressure inside the furnace is controlled at 500-1000 Pa.

[0028] In one embodiment, in step S3, the furnace temperature is controlled at 950–1050°C, the induction power is controlled at 20–40 kW, and the WO3 sublimation rate is controlled at 0.5–2.0 kg / h.

[0029] In one embodiment, in step S3, the flow channel is made of high-purity graphite.

[0030] In one embodiment, in step S4, the hydrogen content in the hydrogen-argon plasma gas 4 is 20%, and the gas flow rate is controlled at 0.1–1 Nm³. 3 / h, the pressure in the reduction zone is controlled at 50-200Pa, and the hydrogen purity is ≥99.999%.

[0031] In one embodiment, in step S5, the temperature of the condenser 8 is controlled at ≤80°C.

[0032] In one embodiment, in step S5, the condenser 8 is a water-cooled capillary collector.

[0033] The complete process steps of this application are as follows: S1. Raw material pretreatment: Weigh industrial pure WO3 raw material with a purity of 99.95%, put it into a drying oven, keep it at 120℃ for 4 hours to remove adsorbed water, and obtain dry WO3 powder.

[0034] S2. Loading and Atmosphere Construction: Dry WO3 powder is loaded into a high-purity graphite crucible 6, and a perforated crucible lid is placed on top. The graphite crucible 6 is then placed into an induction coil 7. After sealing the furnace cavity, the vacuum system 1 is started, and the furnace pressure is adjusted to 800 Pa by the exhaust pump 10 to obtain the WO3 to be sublimated.

[0035] S3, Vacuum Induction Sublimation: Start the induction heating system 2, and heat the graphite crucible 6 through the induction coil 7 to raise the furnace temperature to 1000℃. The induction power is controlled at 30kW, and the power is adjusted in real time according to the WO3 sublimation rate to stabilize the sublimation rate at 1.2kg / h. After the tungsten oxide powder 5 is sublimated, the WO3 vapor enters the hydrogen plasma reduction zone through the high-purity graphite material guide channel. The unsublimated high-boiling-point impurities remain at the bottom of the graphite crucible 6, and the separated WO3 vapor is obtained.

[0036] The hydrogen plasma reduction zone is located directly above the graphite crucible 6 and contains a reaction tube made of high-temperature resistant quartz or corundum. The outside of the reaction tube is wound with an induction coil of the radio frequency plasma generation system 3. The radio frequency plasma generation system 3 is used to excite hydrogen gas to form hydrogen plasma, providing a high-temperature and strong reduction environment for WO3 vapor, thereby achieving deep reduction of WO3 vapor.

[0037] S4, Hydrogen Plasma Reduction: Hydrogen-argon plasma gas with a purity of 99.999% is introduced into the hydrogen plasma reduction zone at a flow rate of 0.8 Nm³. 3 / h, start the radio frequency plasma generation system 3 to excite hydrogen gas to form hydrogen plasma, control the pressure in the reduction zone to 180Pa, and allow the separated WO3 vapor to fully contact the hydrogen plasma to undergo a reduction reaction. The reaction formula is: Tungsten vapor is generated.

[0038] S5. Gas-phase condensation and collection: The tungsten vapor generated by the reduction reaction is guided into the condenser 8 through the guide channel. The water temperature in the condenser 8 is controlled at 50℃. The tungsten vapor is rapidly condensed on the surface of the condenser 8 to form ultrafine tungsten powder. The ultrafine tungsten powder falls into the powder collector 9 under negative pressure suction to obtain high-purity tungsten powder.

[0039] S6. Tail gas recirculation and purification: The tail gas generated by the reduction reaction is discharged through exhaust pump 10, condensed and dehydrated by a 0-10℃ condenser, and then purified by molecular sieve adsorption before being circulated into the hydrogen plasma reduction zone. The hydrogen recycling rate reaches more than 90%.

[0040] The tungsten powder prepared in this embodiment has a purity of 99.9995% and a total impurity content of 5 ppm, including iron content ≤2 ppm, molybdenum content ≤1 ppm, silicon content ≤2 ppm, and an average particle size of 0.5 μm.

[0041] The following detailed description of the method for preparing high-purity tungsten powder by vacuum induction sublimation of WO3 coupled with plasma hydrogen reduction in this application is illustrated with specific embodiments. The raw materials in each embodiment all conform to the aforementioned ratio range, and the process steps refer to the aforementioned complete process steps, with only some parameters differing. Example

[0042] The method for preparing high-purity tungsten powder by vacuum induction sublimation of WO3 coupled with plasma hydrogen reduction provided in this embodiment includes the following specific steps: S1. Raw material pretreatment: Weigh out industrial pure WO3 raw material with a purity of 99.95% and keep it at 120℃ for 4 hours in a drying oven.

[0043] S2. Loading and Atmosphere Construction: Load the dry WO3 powder into the high-purity graphite crucible 6, cover it with the perforated crucible lid, place it in the induction coil 7, seal the furnace cavity, start the vacuum system 1, and adjust the furnace pressure to 800 Pa through the exhaust pump 10.

[0044] S3, Vacuum Induction Sublimation: Start the induction heating system 2, and heat the graphite crucible 6 through the induction coil 7. The temperature inside the furnace rises to 1000℃, the induction power is 30kW, and the sublimation rate is 1.2kg / h. After the tungsten oxide powder 5 is sublimated, the WO3 vapor enters the hydrogen plasma reduction zone through the high-purity graphite guide channel. High-boiling-point impurities remain at the bottom of the crucible 6.

[0045] The hydrogen plasma reduction zone is located directly above the graphite crucible 6 and contains a reaction tube made of high-temperature resistant quartz or corundum. The induction coil of the radio frequency plasma generation system 3 is wound around the outside of the reaction tube.

[0046] S4, Plasma Hydrogen Reduction: A hydrogen-argon plasma gas with a purity of 99.999% is introduced, with hydrogen comprising 20% ​​of the gas, at a flow rate of 0.8 Nm³. 3 / h, start radio frequency plasma generation system 3, reduce zone pressure 180Pa, WO3 vapor reacts with hydrogen plasma, the reaction formula is: Tungsten vapor is generated.

[0047] S5. Gas-phase condensation and collection: Tungsten vapor enters condenser 8, water temperature 50℃, condenses to form ultrafine tungsten powder, falls into powder collector 9, and high-purity tungsten powder is obtained.

[0048] S6. Tail gas recirculation and purification: The tail gas is discharged through exhaust pump 10, and after being condensed and dehydrated at 0-10℃ and purified by molecular sieve, it is recirculated into the reduction zone.

[0049] Examples 2 to 10, Comparative Examples 1 to 3 The preparation steps of Examples 2 to 10 and Comparative Examples 1 to 3 are based on Example 1. Each example changes only one process parameter, while the other parameters are completely consistent with Example 1. The specific differences are shown in Table 1.

[0050] Among them, Comparative Example 1 did not use vacuum induction sublimation, but used the traditional APT hydrogen reduction process; Comparative Example 2 did not use plasma hydrogen reduction, but used the conventional hydrogen solid phase reduction process; Comparative Example 3 did not undergo raw material heat preservation and drying pretreatment.

[0051] Table 1

[0052] The tungsten powders prepared in Examples 1 to 10 and Comparative Examples 1 to 3 were tested. The test indicators included purity, total impurity content, and average particle size. The results are shown in Table 2.

[0053] Table 2

[0054] Combining the data in Tables 1 and 2, the influence of each parameter on performance can be derived, and the specific analysis is as follows.

[0055] 1. Effect of drying temperature In Table 1, Examples 2 and 3 only differ in drying temperature: Example 2 uses 110℃ and Example 3 uses 130℃, while other parameters remain the same as Example 1's 120℃. Corresponding to the performance data in Table 2, Example 2 has a purity of 99.9994% and a total impurity content of 6 ppm. Due to the lower temperature, the adsorbed water removal was insufficient, increasing the load on vacuum system 1 and causing pressure fluctuations in the furnace during the initial sublimation phase. Example 3 has a purity of 99.9995% and a total impurity content of 5 ppm, similar to Example 1. This indicates that 120℃ is the optimal drying temperature, balancing dehydration efficiency and energy consumption.

[0056] 2. The effect of furnace pressure In Table 1, Examples 4 and 5 only differed in furnace pressure: Example 4 was at 500 Pa, and Example 5 at 1000 Pa. Other parameters remained the same as Example 1's 800 Pa. Table 2 shows that Example 4 had a purity of 99.9993% and a total impurity content of 7 ppm. Due to the low pressure, the weak oxidizing atmosphere was insufficient, increasing the tendency for WO3 decomposition. Example 5 had a purity of 99.9996% and a total impurity content of 4 ppm. The increased pressure enhanced the weak oxidizing atmosphere, improving the inhibition of WO3 decomposition and the stability of the sublimation rate. The optimal furnace pressure range is 800–1000 Pa.

[0057] 3. Effect of sublimation temperature In Table 1, Examples 6 and 7 only differed in their sublimation temperature. Example 6 used 950℃, with an induction power of 20kW and a sublimation rate of 0.5kg / h. Example 7 used 1050℃, with an induction power of 40kW and a sublimation rate of 2.0kg / h. Other parameters remained the same as in Example 1 (1000℃). Table 2 shows that Example 6 had a purity of 99.9992% and a total impurity content of 8ppm. The lower temperature resulted in a decreased sublimation rate and reduced separation efficiency for high-boiling-point impurities. Example 7 had a purity of 99.9994% and a total impurity content of 6ppm. The increased temperature improved the sublimation rate but also increased energy consumption. 1000℃ is the optimal sublimation temperature, balancing separation efficiency and energy consumption control.

[0058] 4. Effect of gas flow rate In Table 1, Examples 8 and 9 only changed the gas flow rate; Example 8 had a flow rate of 0.1 Nm³. 3 / h, Example 9 is 1.0 Nm 3 / h, other parameters are the same as 0.8Nm in Example 1. 3 The concentration was consistent with the h. Table 2 shows that Example 8 had a purity of 99.9990% and a total impurity content of 10 ppm. Due to the low flow rate, the hydrogen plasma concentration was insufficient, resulting in incomplete reduction and residual intermediate products. Example 9 had a purity of 99.9995% and a total impurity content of 5 ppm, which was close to that of Example 1. 0.8 Nm 3 / h represents the optimal gas flow rate.

[0059] 5. The effect of pressure in the reduction zone In Table 1, Example 10 only changed the reduction zone pressure to 50 Pa; other parameters remained the same as Example 1 at 180 Pa. Table 2 shows that Example 10 had a purity of 99.9991% and a total impurity content of 9 ppm. The low pressure resulted in a shortened contact time between WO3 vapor and hydrogen plasma, leading to incomplete reduction. 180–200 Pa is the optimal reduction zone pressure.

[0060] 6. Verification of the necessity of key processes The key processes of this application are omitted in Comparative Examples 1, 2, and 3 in Table 1, and their necessity can be verified by the corresponding performance data in Table 2.

[0061] Comparative Example 1 did not use vacuum induction sublimation, but used the traditional APT hydrogen reduction process, with a purity of 99.9500%, a total impurity content of 500 ppm, and an average particle size of 3.0 μm. Compared with Example 1, the purity decreased and the total impurity content increased, proving the necessity of vacuum induction sublimation for the separation of high-boiling-point impurities.

[0062] Comparative Example 2 did not use plasma hydrogen reduction, but used conventional hydrogen solid-phase reduction process, with a purity of 99.9900%, a total impurity content of 100 ppm, and an average particle size of 2.5 μm. The purity was lower than that of Example 1, which proves the necessity of plasma hydrogen reduction for deep reduction of WO3 vapor.

[0063] Comparative Example 3 did not undergo raw material heat preservation and drying pretreatment, with a purity of 99.9990%, a total impurity content of 10 ppm, and an average particle size of 0.6 μm. The purity decreased compared to Example 1, demonstrating the necessity of raw material pretreatment for maintaining the stability of the vacuum environment.

[0064] Table 3 shows the chemical composition of the high-purity tungsten powder prepared by vacuum induction sublimation of WO3 coupled with plasma hydrogen reduction according to this application, as determined by GD-MS purity. The mass fraction is expressed in ppm.

[0065] Table 3

[0066] Based on the data and analysis in Tables 1 to 3, the innovative aspects of the method for preparing high-purity tungsten powder by vacuum induction sublimation of WO3 coupled with plasma hydrogen reduction provided in this application can be summarized into four points.

[0067] 1. One-step coupling of gas phase sublimation and gas phase reduction: Utilizing the physical properties of WO3 at high temperature and high volatility above 800℃, combined with vacuum conditions, WO3 is efficiently sublimated, and WO3 is separated from high-boiling-point impurities at the same time. Then, through the high temperature and strong reduction activity of hydrogen plasma, WO3 vapor is deeply reduced in one step, which solves the problem of incomplete impurity separation and difficulty in achieving purity of 5N in traditional processes.

[0068] 2. Weak oxidizing atmosphere inhibits decomposition: By controlling the furnace pressure to 500-1000 Pa, a weak oxidizing atmosphere is formed, which inhibits the decomposition of WO3 during the heating process and promotes the stable transmission of WO3 vapor. This avoids the problem of uneven WO3 decomposition caused by traditional electron beam heating, reduces energy consumption and improves sublimation efficiency.

[0069] 3. Radio frequency hydrogen plasma deep reduction: Hydrogen gas is excited by radio frequency plasma to generate hydrogen plasma. The pressure in the reduction zone is controlled at 50-200 Pa. WO3 vapor and hydrogen plasma are in full contact to undergo a gas-gas reaction. The reduction reaction is thorough and there are no intermediate product residues. After generating tungsten vapor, it is rapidly condensed by a water-cooled collector at ≤80℃ to obtain high-purity tungsten powder with uniform particle size.

[0070] 4. Green recycling process: The exhaust gas is recycled after being dehydrated by low-temperature condensation and purified by molecular sieve. The hydrogen recycling rate reaches more than 90%, and there are no harmful by-product emissions, which meets the requirements of green manufacturing.

[0071] In summary, the specific implementation method of this application demonstrates the innovation, stability and practicality of the process through a complete logical chain of parameter design, performance testing, pattern analysis and application verification. It not only solves the technical pain points of low purity, long process and high energy consumption of traditional tungsten powder preparation process, but also meets the demand of high-end fields for 5N grade and above ultra-high purity tungsten powder, and has broad promotion value.

[0072] Finally, it should be noted that the above experimental examples are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred experimental examples, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing high-purity tungsten powder by vacuum induction sublimation of WO3 coupled with plasma hydrogen reduction, characterized in that, Includes the following steps: S1. Raw material pretreatment: Obtain industrial pure WO3 raw material, remove adsorbed water by heat preservation and drying, and obtain dry WO3 powder; S2. Charging and Atmosphere Construction: Dry WO3 powder is loaded into a graphite crucible and placed in an induction coil. After sealing the furnace cavity, the vacuum system is started to adjust the pressure inside the furnace, thus obtaining the WO3 charge to be sublimated. S3, Vacuum Induction Sublimation: The WO3 charge to be sublimated is induction heated to raise the temperature, the temperature inside the furnace is controlled, and the induction power is adjusted in real time according to the WO3 sublimation rate. WO3 vapor enters the hydrogen plasma reduction zone through the guide channel, and the unsublimated impurities remain at the bottom of the graphite crucible, thus obtaining the separated WO3 vapor. S4. Plasma hydrogen reduction: A hydrogen-argon mixed plasma gas is introduced into the hydrogen plasma reduction zone. The radio frequency plasma generator is started to excite the hydrogen gas to form hydrogen plasma. The pressure in the reduction zone is controlled so that the separated WO3 vapor and the hydrogen plasma undergo a gas-phase reduction reaction to generate tungsten vapor. S5. Gas-phase condensation and collection: Tungsten vapor is introduced into a water-cooled collector for condensation to obtain high-purity tungsten powder; S6. Tail gas recirculation and purification: The tail gas produced by the reduction reaction is collected, and after being purified by condensation and dehydration and molecular sieve adsorption, it is circulated into the hydrogen plasma reduction zone to obtain a recirculating hydrogen-argon mixture.

2. The method for preparing high-purity tungsten powder by vacuum induction sublimation of WO3 coupled with plasma hydrogen reduction according to claim 1, characterized in that, In step S1, the drying temperature is controlled at 110-130℃ and the holding time is controlled at 4-8h; the purity of industrial pure WO3 raw material is ≥99.95%.

3. The method for preparing high-purity tungsten powder by vacuum induction sublimation of WO3 coupled with plasma hydrogen reduction according to claim 1, characterized in that, In step S2, the graphite crucible is made of high-purity graphite and is equipped with a perforated crucible lid; the pressure inside the furnace is controlled at 500-1000 Pa.

4. The method for preparing high-purity tungsten powder by vacuum induction sublimation of WO3 coupled with plasma hydrogen reduction according to claim 1, characterized in that, In step S3, the furnace temperature is controlled at 950–1050℃, the induction power is controlled at 20–40kW, and the WO3 sublimation rate is controlled at 0.5–2.0kg / h.

5. The method for preparing high-purity tungsten powder by vacuum induction sublimation of WO3 coupled with plasma hydrogen reduction according to claim 1, characterized in that, In step S3, the flow channel is made of high-purity graphite.

6. The method for preparing high-purity tungsten powder by vacuum induction sublimation of WO3 coupled with plasma hydrogen reduction according to claim 1, characterized in that, In step S4, the hydrogen content in the hydrogen-argon mixed plasma gas is 20%, and the gas flow rate is controlled between 0.1 and 1 Nm³. 3 / h, the pressure in the reduction zone is controlled at 50-200Pa; the hydrogen purity is ≥99.999%.

7. The method for preparing high-purity tungsten powder by vacuum induction sublimation of WO3 coupled with plasma hydrogen reduction according to claim 1, characterized in that, In step S5, the temperature of the water-cooled collector is controlled at ≤80℃.

8. The method for preparing high-purity tungsten powder by vacuum induction sublimation of WO3 coupled with plasma hydrogen reduction according to claim 1, characterized in that, In step S5, the water-cooled collector is a water-cooled capillary collector.

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