A method for preparing tungsten carbide powder by one-step carbonization of an ammonium paratungstate precursor
The one-step carbonization method using ammonium arsotungstenate precursor to prepare ultrafine tungsten carbide powder solves the problem of spontaneous combustion due to oxidation of ultrafine tungsten powder, realizes safe and efficient production of ultrafine tungsten carbide powder, simplifies the process and improves product quality and safety.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JIANGXI UNIV OF SCI & TECH
- Filing Date
- 2026-01-28
- Publication Date
- 2026-07-07
Smart Images
Figure CN121778734B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of chemical materials technology, specifically relating to a method for preparing tungsten carbide powder by one-step carbonization of ammonium arsotungstate precursor. Background Technology
[0002] In recent years, tungsten smelting technology based on heteropolyacid chemistry has received widespread attention and research due to its high efficiency, environmental friendliness, and potential for comprehensive resource recovery. The core of this technology lies in utilizing the formation of stable heteropolyacid complexes between tungsten and elements such as phosphorus, arsenic, and silicon in an acidic medium, thereby achieving efficient extraction and purification of tungsten and simultaneously recovering valuable elements. Patent CN114525416B provides a specific implementation scheme: In a mixed acid system containing inorganic acid and arsenic acid, tungstate raw materials are added. By controlling the acidity and concentration, a coordination reaction between tungsten and arsenic is induced, generating soluble arsotungstic acid. Subsequently, an ammonium reagent (such as ammonia or ammonium salt) is introduced into the solution, causing the arsotungstic acid to precipitate as ammonium arsotungstate. Finally, the precursor is placed in a hydrogen atmosphere at 720–800°C for reduction, obtaining both ultrafine tungsten powder and elemental arsenic in one step. Another patent, CN114517264B, further applies this principle to the processing of complex materials, proposing a metallurgical method for synergistic tungsten extraction and arsenic removal: scheelite is mixed with a high-arsenic, high-acidity solution for leaching, dissolving tungsten while simultaneously allowing arsenic to combine with tungsten to form arsotungstic heteropolyacids that enter the liquid phase; after solid-liquid separation to remove residues, the heteropolyacids are enriched and purified through solvent extraction and back-extraction; subsequently, ammonium is added to precipitate ammonium arsotungstate, which can then be reduced with hydrogen to prepare ultrafine tungsten powder and elemental arsenic. Both patents demonstrate the advantages of the heteropolyacid pathway in tungsten resource extraction and the harmless and resource-based treatment of arsenic.
[0003] However, the ultrafine tungsten powder obtained in this way exhibits very high chemical activity due to its large specific surface area and high surface energy. It is extremely prone to oxidation upon contact with air, forming a tungsten oxide layer, and can even spontaneously combust in air, posing safety risks and quality control challenges for subsequent storage and processing. Furthermore, the ultrafine tungsten powder, as an intermediate product, requires long-term ball milling and high-temperature carbonization after being uniformly mixed with carbon powder to finally transform into ultrafine tungsten carbide powder. This traditional two-step process is lengthy, and the risk of oxidation from exposure to air in the intermediate stages is difficult to completely avoid. Therefore, exploring a more integrated process route to directly prepare ultrafine tungsten carbide from ammonium arsotungstate precursor via one-step carbonization completely avoids the generation of ultrafine tungsten powder intermediates and their exposure risks. This not only has the potential to simplify the process, reduce energy consumption and costs, but also fundamentally improve the safety of the production process and provide a new technical approach for the controllable synthesis of high-performance ultrafine / nano-tungsten carbide materials. Summary of the Invention
[0004] The purpose of this invention is to provide a method for preparing ultrafine tungsten carbide powder, which aims to generate ultrafine tungsten carbide powder in one step by carbonizing an ammonium arsotungstate precursor in a mixed gas of methane and hydrogen or water vapor.
[0005] To achieve the above objectives, this invention proposes a method for preparing tungsten carbide powder by one-step carbonization of ammonium arsotungstate precursor, comprising the following steps:
[0006] (1) Dehydration step: Place the ammonium arsotungstate precursor in a controllable atmosphere reactor and raise the temperature to 450°C under inert gas protection to decompose the ammonium arsotungstate precursor and remove the water of crystallization therein;
[0007] (2) First carbonization process: After step (1), the atmosphere is switched to methane or natural gas with methane as the main component, and the temperature is raised to 700-800℃ and kept at the temperature to carry out the reduction carbonization reaction;
[0008] (3) Second stage carbonization process: After step (2), the atmosphere is switched to a mixture of methane and hydrogen or water vapor, and the temperature is raised to 900-1200℃ and kept at the temperature for deep carbonization reaction;
[0009] (4) Cooling and collection steps: After step (3), the atmosphere is switched to inert gas, and after cooling, the tungsten carbide powder in the furnace and the elemental arsenic condensed in the low temperature zone of the furnace are collected respectively.
[0010] Preferably, the volume content of hydrogen or water vapor in the mixed gas in step (3) is 20% to 90%, and the volume content of methane is 10% to 80%.
[0011] Preferably, the time taken for the temperature to rise from 100°C to 450°C in step (1) is not less than 30 minutes.
[0012] Preferably, the reduction carbonization reaction time in step (2) is 30 to 60 minutes.
[0013] Preferably, the deep carbonization reaction time in step (3) is 30 to 90 minutes.
[0014] Preferably, the inert gas used in steps (1) and (4) is one or both of argon and nitrogen.
[0015] The technical principles employed in this invention are as follows:
[0016] Ammonium arsotungstate, when heated under an inert atmosphere, begins to lose its water of crystallization after reaching 100°C and decomposes at around 480–500°C, producing ammonia and water vapor. Upon further heating, arsenic will volatilize as As₂O₃. Prior to the decomposition of ammonium arsotungstate, only a dehydration reaction occurs.
[0017]
[0018] Therefore, in step (1), only an inert gas is introduced, and it is not necessary to introduce a reducing gas.
[0019] In a reducing atmosphere of methane, arsenic is readily reduced and volatilized, and ammonium arsotungstate is decomposed. Therefore, to facilitate the separation of arsenic and tungsten, methane is introduced during the decomposition stage of ammonium arsotungstate. Simultaneously, in step (2), under the reducing atmosphere, arsenic will volatilize and be reduced to elemental arsenic, while tungsten will be partially reduced to elemental tungsten and undergo varying degrees of carbonization. The reaction equations are as follows:
[0020]
[0021] In step (3), during the deep carbonization stage, a mixture of methane and hydrogen or water vapor is introduced to suppress the high-temperature decomposition of methane into carbon. The carbonization reaction that occurs in this stage is as follows:
[0022]
[0023] Methane tends to decompose into carbon and hydrogen under high-temperature conditions. Therefore, a mixture of methane and hydrogen or water vapor is used in the high-temperature stage to remove the carbon produced by methane decomposition. The main reaction is as follows:
[0024]
[0025] The beneficial effects that this invention can achieve are as follows:
[0026] This invention not only utilizes methane at moderate temperatures to efficiently drive the reduction and volatilization of arsenic and the initial carbonization of tungsten, significantly reducing the consumption of expensive hydrogen and process costs, but also effectively suppresses excessive methane cracking and free carbon generation by introducing hydrogen or water vapor during the high-temperature deep carbonization stage, thereby ensuring the high purity and precise stoichiometry of the ultrafine tungsten carbide product. The entire process is completed continuously in a closed system, avoiding the risks of oxidation and spontaneous combustion caused by exposure of the ultrafine tungsten powder intermediates to air, thus improving production safety. Simultaneously, this process achieves efficient and targeted recovery of arsenic in elemental form, simultaneously completing the deep carbonization of tungsten and the resource recovery of arsenic, ultimately obtaining ultrafine tungsten carbide powder with uniform particle size and regular morphology in one step. This invention provides a new technical approach for the controllable synthesis of high-performance ultrafine tungsten carbide materials. Attached Figure Description
[0027] Figure 1 This is a scanning electron microscope image of the ammonium arsotungstate precursor used in Example 1.
[0028] Figure 2 This is a scanning electron microscope image of the tungsten carbide powder prepared in Example 1.
[0029] Figure 3The image shows the XRD pattern of the tungsten carbide powder prepared in Example 1.
[0030] Figure 4 This is a scanning electron microscope image of the tungsten carbide powder prepared in Example 2.
[0031] Figure 5 The image shows the XRD pattern of the tungsten carbide powder prepared in Example 2. Detailed Implementation
[0032] The present invention will be further illustrated by the following examples, but is not limited thereto.
[0033] Example 1
[0034] Scanning electron microscope image of ammonium arsotungstate precursor as shown below Figure 1 As shown in the figure. 8 grams of ammonium arsotungstenate precursor powder were placed in a crucible and then placed in a tube furnace. Under argon protection, the temperature was increased from room temperature (approximately 27°C) to 450°C at a rate of 10°C per minute. Then, the atmosphere was switched to methane, and the temperature was further increased to 700°C and held for 60 minutes for the first stage of carbonization. Subsequently, the atmosphere was switched to a mixture of methane and water vapor, with a water vapor volume content of 20% and a methane volume content of 80%. The temperature was increased to 1200°C and held for 30 minutes. After heating was stopped, the atmosphere was switched back to argon, and the mixture was cooled to room temperature before the solid product was removed. The scanning electron microscope image of the obtained tungsten carbide powder is shown in the figure. Figure 2 As shown, the XRD pattern is as follows Figure 3 As shown.
[0035] Example 2
[0036] Ten grams of ammonium arsotungstate precursor powder were placed in a crucible and then placed in a tube furnace. Under argon protection, the temperature was increased from room temperature (approximately 22°C) to 450°C at a rate of 10°C per minute. Then, the atmosphere was switched to natural gas with methane as the main component, and the temperature was further increased to 800°C and held for 30 minutes for the first stage of carbonization. Subsequently, the atmosphere was switched to a mixture of methane and hydrogen, with a hydrogen volume content of 90% and a methane volume content of 10%, and the temperature was increased to 900°C and held for 90 minutes. After heating was stopped, the atmosphere was switched back to argon, and the mixture was cooled to room temperature before the solid product was removed. The scanning electron microscope image of the obtained tungsten carbide powder is shown below. Figure 4 As shown, the XRD pattern is as follows Figure 5 As shown.
[0037] Example 3
[0038] 60 grams of ammonium arsotungstenate precursor powder were divided into three equal portions: Sample A, Sample B, and Sample C. Sample A was placed in a crucible and then in a tube furnace. Under nitrogen protection, the temperature was increased from room temperature (approximately 21°C) to 450°C at a rate of 10°C per minute. The atmosphere was then switched to methane, and the temperature was further increased to 750°C and held for 30 minutes for the first stage of carbonization. Subsequently, the atmosphere was switched to a mixture of methane and hydrogen, with a hydrogen volume content of 50% and a methane volume content of 50%. The temperature was increased to 1000°C and held for 60 minutes. After heating was stopped, the atmosphere was switched back to nitrogen, and the mixture was cooled to room temperature before the solid product was removed. The free carbon content of the obtained tungsten carbide powder was determined to be 0.046 wt.%.
[0039] Sample B was placed in a crucible and then placed in a tube furnace. Under nitrogen protection, the temperature was increased from room temperature (approximately 20°C) to 450°C at a rate of 10°C per minute. The atmosphere was then switched to methane, and the temperature was further increased to 750°C and held for 30 minutes. Subsequently, the atmosphere was switched to a mixture of methane and water vapor, with a water vapor volume content of 50% and a methane volume content of 50%, and the temperature was increased to 1000°C and held for 60 minutes. After heating was stopped, the atmosphere was switched to nitrogen, and the mixture was cooled to room temperature before the solid product was removed. Black carbon deposits were found on the surface of the crucible and the inner wall of the tube. The free carbon content of the obtained tungsten carbide powder was determined to be 0.037 wt.%.
[0040] Sample C was placed in a crucible and then in a tube furnace. Under nitrogen protection, the temperature was increased from room temperature (approximately 22°C) to 450°C at a rate of 10°C per minute. The atmosphere was then switched to methane, and the temperature was further increased to 750°C and held for 30 minutes. Methane was then continuously introduced, and the temperature was increased to 1000°C and held for 60 minutes. After heating was stopped, the atmosphere was switched to nitrogen, and the product was cooled to room temperature before being removed. Black carbon deposits were found on the surface of the crucible and the inner wall of the tube. The free carbon content of the obtained tungsten carbide powder was determined to be 0.191 wt.%.
[0041] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for preparing tungsten carbide powder by one-step carbonization of ammonium arsotungstate precursor, characterized in that, Includes the following steps: (1) Dehydration step: Place the ammonium arsotungstate precursor in a controllable atmosphere reactor and raise the temperature to 450°C under inert gas protection to decompose the ammonium arsotungstate precursor and remove the water of crystallization therein; (2) First carbonization process: After step (1), the atmosphere is switched to methane or natural gas with methane as the main component, and the temperature is raised to 700-800℃ and kept at the temperature to carry out the reduction carbonization reaction; (3) Second stage carbonization process: After step (2), the atmosphere is switched to a mixture of methane and hydrogen or water vapor, and the temperature is raised to 900-1200℃ and kept at the temperature for deep carbonization reaction; (4) Cooling and collection steps: After step (3), the atmosphere is switched to inert gas, and after cooling, the tungsten carbide powder in the furnace and the elemental arsenic condensed in the low temperature zone of the furnace are collected respectively.
2. The method as described in claim 1, characterized in that, In step (3), the volume content of hydrogen or water vapor in the mixed gas is 20% to 90%, and the volume content of methane is 10% to 80%.
3. The method as described in claim 1, characterized in that, The time taken to raise the temperature from 100℃ to 450℃ in step (1) shall not be less than 30 minutes.
4. The method as described in claim 1, characterized in that, The reduction carbonization reaction time in step (2) is 30 to 60 minutes.
5. The method as described in claim 1, characterized in that, The deep carbonization reaction time in step (3) is 30 to 90 minutes.
6. The method as described in claim 1, characterized in that, The inert gas used in steps (1) and (4) is one or both of argon and nitrogen.