A method for preparing nano tungsten carbide powder

Abstract

The application provides a method for preparing nano tungsten carbide powder, which comprises the following steps: subjecting a tungsten source solution to hydrothermal reaction to obtain a tungsten oxide precursor; subjecting the oxide precursor to plasma treatment to obtain nano tungsten oxide powder; mixing the nano tungsten oxide powder with a composite carbon source to obtain spherical composite precursor powder; and subjecting the spherical composite precursor powder to reduction and carbonization to obtain nano tungsten carbide powder. The method for preparing nano tungsten carbide powder provided by the application solves the problems of high temperature, coarse grains and difficult carbon content control in the traditional process by means of hydrothermal reaction, plasma treatment, composite carbon source mixing and reduction and carbonization, and the obtained nano tungsten carbide powder has an average grain size of ≤ 150 nm, free carbon of ≤ 0.2 wt%, and oxygen content of ≤ 0.35 wt%, low energy consumption and easy continuous industrial production.

Description

Technical Field

[0001] This application belongs to the field of nanopowder preparation technology, and relates to a method for preparing nano-tungsten carbide powder. Background Technology

[0002] Nano-tungsten carbide (WC) powder is a raw material for preparing ultrafine-grained cemented carbide. Precise control of its grain size, purity, and carbon content directly determines the alloy's hardness, wear resistance, and fracture toughness. Currently, the mainstream industrial process for preparing tungsten carbide powder involves first reducing tungsten oxide to elemental tungsten powder in high-temperature hydrogen gas, then mechanically mixing the tungsten powder with carbon black, and finally performing solid-phase carbonization at 1300℃~1450℃. This route is lengthy, energy-intensive, and the prolonged high-temperature carbonization inevitably leads to abnormal grain growth and powder sintering and agglomeration, making it difficult to consistently obtain high-quality ultrafine nano-tungsten carbide products. Furthermore, mechanical carbon mixing makes it difficult to achieve uniform molecular-level contact between carbon and tungsten. The carbonization reaction relies on solid-state diffusion at high temperatures, which easily results in a high free carbon content and a deviation of the combined carbon content from the theoretical value in the product, directly affecting the alloy's performance.

[0003] To lower the carbonization temperature and improve the uniformity of carbon distribution, existing technologies attempt to use nano-tungsten oxide as a precursor and introduce organic carbon sources for liquid-phase coating. However, these technologies still have significant shortcomings: on the one hand, conventional nano-tungsten oxide has a low surface oxygen vacancy concentration, and its intrinsic reactivity is not fully activated, resulting in carbonization temperatures still exceeding 1200℃; on the other hand, carbon source coating is mostly limited to mechanical adsorption, failing to achieve precise control of molecular-level uniform thickness, and the pyrolysis and local enrichment of carbon sources at high temperatures are still difficult to avoid. Existing carbonization processes are generally carried out in static powder beds such as tube furnaces, where the powder is stacked statically, leading to uneven heat and mass transfer during the reaction process. This not only exacerbates sintering between particles and grain coarsening but also makes precise online carbon adjustment almost impossible, making it difficult to simultaneously achieve the desired results in terms of finished product grain size, free carbon, and combined carbon content.

[0004] Therefore, there is an urgent need to develop a novel method for preparing nano-tungsten carbide that can integrate the preparation of highly active nano-tungsten oxide precursors, molecular-level uniform coating of carbon sources, and dynamic low-temperature carbonization process. This method can complete reduction and carbonization in one step within a closed reactor, completely eliminating the need for high-temperature and intermediate product preparation steps, and achieving precise and coordinated control of grain size, carbon content, and impurity content. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this application aims to provide a method for preparing nano-tungsten carbide powder. This method utilizes hydrothermal reaction and plasma treatment to synergistically activate the tungsten source, mix the composite carbon source, and perform reduction carbonization. This solves the problems of high temperature, coarse grains, and difficulty in controlling carbon content in traditional processes. The resulting nano-tungsten carbide powder has an average grain size ≤150nm, free carbon ≤0.2wt%, and oxygen content ≤0.35wt%. It also features low energy consumption and is easy for continuous industrial production.

[0006] To achieve this objective, the present application adopts the following technical solution:

[0007] This application provides a method for preparing nano-tungsten carbide powder, the method comprising the following steps:

[0008] A tungsten source solution undergoes a hydrothermal reaction to obtain a tungsten oxide precursor; the oxide precursor is then subjected to plasma treatment to obtain nano-tungsten oxide powder.

[0009] The nano-tungsten oxide powder is mixed with the composite carbon source to obtain spherical composite precursor powder;

[0010] The spherical composite precursor powder was reduced and carbonized to obtain nano-tungsten carbide powder.

[0011] The method provided in this application enhances the intrinsic reactivity of the tungsten source by performing a hydrothermal reaction on the tungsten source solution and combining it with plasma treatment to regulate the surface oxygen vacancy concentration of the nano-tungsten oxide powder. This allows for reduction and carbonization to be completed within 950℃, reducing heat treatment energy consumption and minimizing the risks of nanoparticle sintering and abnormal grain coarsening under high-temperature conditions. By employing a composite carbon source, uniform molecular-level coating of the nano-tungsten oxide powder is achieved, solving the problems of uneven carbon distribution, excessive free carbon, and deviation of combined carbon from theoretical values ​​that exist in traditional mechanical mixing and single-component carbon coating. Combined with reduction and carbonization, the final nano-tungsten carbide powder has a uniform average grain size of no more than 150nm, low oxygen impurity content, stable combined carbon content within the standard range, narrow particle size distribution, and no coarse impurities. When used as a raw material to prepare ultrafine-grained WC-Co cemented carbide, it can simultaneously improve the alloy's hardness and fracture toughness. The entire process is adaptable to continuous industrial production, resulting in lower production costs and better product consistency.

[0012] In some embodiments, the tungsten source solution is a sodium tungstate solution.

[0013] In some embodiments, the temperature of the hydrothermal reaction is 120°C to 200°C.

[0014] In some embodiments, the hydrothermal reaction takes 6 to 24 hours.

[0015] In some embodiments, the plasma treatment reduces the oxygen vacancy concentration of the nano-tungsten oxide powder to 1 × 10⁻⁶.19 cm -3 ~5×10 20 cm -3 .

[0016] In some embodiments, the average particle size of the nano-tungsten oxide powder is 10 nm to 80 nm.

[0017] In some embodiments, the composite carbon source comprises a first carbon source and a second carbon source in a mass ratio of 1:0.5 to 1:2;

[0018] The first carbon source includes glucose and / or sucrose;

[0019] The second carbon source includes polyethylene glycol.

[0020] In some embodiments, the carbon-tungsten molar ratio of the spherical composite precursor powder is 1.02:1 to 1.04:1.

[0021] In some embodiments, the reduction carbonization includes a first reduction carbonization, a second reduction carbonization, and a third reduction carbonization performed sequentially;

[0022] The first reduction carbonization is carried out in a nitrogen atmosphere;

[0023] The second reduction carbonization is carried out in a mixture of hydrogen and methane, with a hydrogen to methane volume ratio of 2:1 to 5:1.

[0024] The third reduction carbonization is carried out in a mixture of hydrogen and methane, with a hydrogen to methane volume ratio of 10:1 to 50:1.

[0025] In some embodiments, the heating rate of the first reduction carbonization is 2°C / min to 5°C / min.

[0026] In some embodiments, the temperature of the first reduction carbonization is 300°C to 400°C.

[0027] In some embodiments, the first reduction carbonization time is 0.5h to 1.5h.

[0028] In some embodiments, the heating rate of the second reduction carbonization is 3°C / min to 8°C / min.

[0029] In some embodiments, the temperature of the second reduction carbonization is 600°C to 800°C.

[0030] In some embodiments, the second reduction carbonization time is 1h to 4h.

[0031] In some embodiments, the temperature of the third reduction carbonization is 600°C to 800°C.

[0032] In some embodiments, the third reduction carbonization time is 0.5h to 1h.

[0033] As a preferred embodiment of the method provided in this application, the method includes the following steps:

[0034] S1. A sodium tungstate solution is subjected to a hydrothermal reaction at 120℃~200℃ for 6h~24h to obtain a tungsten oxide precursor; the oxide precursor is then subjected to plasma treatment to obtain an oxygen vacancy concentration of 1×10⁻⁶. 19 cm -3 ~5×10 20 cm -3 Nano-sized tungsten oxide powder;

[0035] The average particle size of the nano-tungsten oxide powder is 10nm~80nm;

[0036] S2. The nano-tungsten oxide powder is mixed with the composite carbon source to obtain spherical composite precursor powder;

[0037] The composite carbon source comprises a first carbon source and a second carbon source in a mass ratio of 1:0.5 to 1:2; the first carbon source comprises glucose and / or sucrose; the second carbon source comprises polyethylene glycol.

[0038] The carbon-tungsten molar ratio of the spherical composite precursor powder is 1.02:1 to 1.04:1;

[0039] S3. The spherical composite precursor powder is reduced and carbonized to obtain nano-tungsten carbide powder.

[0040] The reduction carbonization includes a first reduction carbonization, a second reduction carbonization, and a third reduction carbonization performed sequentially; the first reduction carbonization is carried out in a nitrogen atmosphere; the second reduction carbonization is carried out in a mixture of hydrogen and methane, with a hydrogen to methane volume ratio of 2:1 to 5:1; the third reduction carbonization is carried out in a mixture of hydrogen and methane, with a hydrogen to methane volume ratio of 10:1 to 50:1.

[0041] The heating rate for the first reduction carbonization is 2℃ / min~5℃ / min, the temperature is 300℃~400℃, and the time is 0.5h~1.5h;

[0042] The heating rate for the second reduction carbonization is 3℃ / min~8℃ / min, the temperature is 600℃~800℃, and the time is 1h~4h;

[0043] The third reduction carbonization is carried out at a temperature of 600℃~800℃ for a time of 0.5h~1h.

[0044] The numerical range described in this application includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific point values ​​included in the range.

[0045] Compared with the prior art, this application has the following advantages:

[0046] The method for preparing nano-tungsten carbide powder provided in this application enhances the intrinsic reactivity of the tungsten source by subjecting the tungsten source solution to a hydrothermal reaction combined with plasma treatment to regulate the surface oxygen vacancy concentration of the nano-tungsten oxide powder. This allows for reduction carbonization to be completed within 950℃, reducing heat treatment energy consumption and minimizing the risk of nanoparticle sintering and abnormal grain coarsening under high-temperature conditions. The use of a composite carbon source achieves uniform molecular-level coating of the nano-tungsten oxide powder, solving the problems of uneven carbon distribution, excessive free carbon, and deviation of combined carbon from theoretical values ​​associated with traditional mechanical mixing and single-component carbon coating. Combined with reduction carbonization, the final nano-tungsten carbide powder exhibits a uniform average grain size not exceeding 150nm, low oxygen impurity content, stable combined carbon content within the standard range, narrow particle size distribution, and absence of coarse impurities. When used as a raw material to prepare ultrafine-grained WC-Co cemented carbide, it can simultaneously improve the alloy's hardness and fracture toughness. The entire process is adaptable to continuous industrial production, resulting in lower production costs and better product consistency. Detailed Implementation

[0047] The technical solution of this application will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely to help understand this application and should not be regarded as specific limitations on this application.

[0048] The "range" disclosed in this application can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints. Any endpoint can be independently included or excluded, and they can be combined arbitrarily; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for a specific parameter, it is expected that ranges of 60~110 and 80~120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are also listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this application, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0049] In this application, "a combination of at least two" refers to a quantity greater than or equal to two, unless otherwise specified. For example, "any one or at least two combinations" means one or more of the two. It can be understood that "a combination of at least two" refers to any suitable combination of multiple items, that is, a combination of "at least two" items that are not conflicting and can be implemented in the manner described in this application.

[0050] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0051] The term "embodiment" as used in this application means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this application can be combined with other embodiments.

[0052] Those skilled in the art will understand that the order in which the steps are written in the methods of the various embodiments does not imply a strict execution order. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of this application may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), meaning that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0053] In this application, open-ended technical features or solutions described with terms such as "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, if A includes a1, a2, and a3, it may also include other members or exclude additional members unless otherwise specified. This can be considered as providing both technical features or solutions where "A consists of a1, a2, and a3" or "A is selected from a1, a2, and a3," and technical features or solutions where "A includes not only a1, a2, and a3, but also other members."

[0054] In this application, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a group consisting of A, B, and "a combination of A and B". "Containing A and / or B" can mean "containing A, containing B, and containing A and B", or "containing A, containing B, or containing A and B", and can be appropriately understood according to the context.

[0055] In this application, "room temperature" generally refers to 4℃~35℃, and may refer to 20℃±5℃. In some embodiments of this application, room temperature refers to 20℃~30℃.

[0056] This application provides a method for preparing nano-tungsten carbide powder, the method comprising the following steps:

[0057] A tungsten source solution undergoes a hydrothermal reaction to obtain a tungsten oxide precursor; the oxide precursor is then subjected to plasma treatment to obtain nano-tungsten oxide powder.

[0058] The nano-tungsten oxide powder is mixed with the composite carbon source to obtain spherical composite precursor powder;

[0059] The spherical composite precursor powder was reduced and carbonized to obtain nano-tungsten carbide powder.

[0060] The method provided in this application enhances the intrinsic reactivity of the tungsten source by performing a hydrothermal reaction on the tungsten source solution and combining it with plasma treatment to regulate the surface oxygen vacancy concentration of the nano-tungsten oxide powder. This allows for reduction and carbonization to be completed within 950℃, reducing heat treatment energy consumption and minimizing the risks of nanoparticle sintering and abnormal grain coarsening under high-temperature conditions. By employing a composite carbon source, uniform molecular-level coating of the nano-tungsten oxide powder is achieved, solving the problems of uneven carbon distribution, excessive free carbon, and deviation of combined carbon from theoretical values ​​that exist in traditional mechanical mixing and single-component carbon coating. Combined with reduction and carbonization, the final nano-tungsten carbide powder has a uniform average grain size of no more than 150nm, low oxygen impurity content, stable combined carbon content within the standard range, narrow particle size distribution, and no coarse impurities. When used as a raw material to prepare ultrafine-grained WC-Co cemented carbide, it can simultaneously improve the alloy's hardness and fracture toughness. The entire process is adaptable to continuous industrial production, resulting in lower production costs and better product consistency.

[0061] In some embodiments, the tungsten source solution is a sodium tungstate solution.

[0062] Optionally, the concentration of the sodium tungstate solution is 0.2 mol / L to 0.3 mol / L.

[0063] In some embodiments, the temperature of the hydrothermal reaction is 120°C to 200°C, for example, 120°C, 130°C, 140°C, 150°C, 160°C, 180°C or 200°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0064] In some embodiments, the hydrothermal reaction time is 6h to 24h, for example, it can be 6h, 8h, 10h, 12h, 15h, 16h, 18h, 20h, 21h or 24h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0065] In some embodiments, the plasma treatment reduces the oxygen vacancy concentration of the nano-tungsten oxide powder to 1 × 10⁻⁶. 19 cm -3 ~5×10 20 cm -3 For example, it could be 1×10 19 cm-3 5×10 19 cm -3 1×10 20 cm -3 2×10 20 cm -3 3×10 20 cm -3 4×10 20 cm -3 Or 5×10 20 cm -3 However, this does not limit the listed values; any other unlisted values ​​within the range are also applicable.

[0066] Optionally, the plasma treatment conditions can be as follows: under an absolute pressure not exceeding 10 Pa, a mixture of argon and hydrogen is introduced as the working gas (the hydrogen volume percentage can be 10%), and the pressure is maintained at 100 Pa to 200 Pa; the radio frequency power supply is turned on, the discharge power is adjusted to 100 W to 300 W, and the time is adjusted to 30 min to 90 min. This application does not limit the specific plasma treatment parameters, as long as the oxygen vacancy concentration of the nano-tungsten oxide powder reaches the specified value.

[0067] In some embodiments, the average particle size of the nano-tungsten oxide powder is 10nm to 80nm, for example, it can be 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm or 80nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0068] In some embodiments, the composite carbon source comprises a first carbon source and a second carbon source in a mass ratio of 1:0.5 to 1:2;

[0069] The first carbon source includes glucose and / or sucrose;

[0070] The second carbon source includes polyethylene glycol.

[0071] The mass ratio of the first carbon source to the second carbon source is 1:0.5 to 1:2, for example, it can be 1:0.5, 1:0.6, 1:0.8, 1:1, 1:1.2, 1:1.5, 1:1.6, 1:1.8 or 1:2, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0072] In some embodiments, the carbon-tungsten molar ratio of the spherical composite precursor powder is 1.02:1 to 1.04:1, for example, it can be 1.02:1, 1.03:1 or 1.04:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0073] In some embodiments, the reduction carbonization includes a first reduction carbonization, a second reduction carbonization, and a third reduction carbonization performed sequentially;

[0074] The first reduction carbonization is carried out in a nitrogen atmosphere;

[0075] The second reduction carbonization is carried out in a mixture of hydrogen and methane, with a hydrogen to methane volume ratio of 2:1 to 5:1, for example, 2:1, 3:1, 4:1 or 5:1, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0076] The third reduction carbonization is carried out in a mixture of hydrogen and methane, with a hydrogen to methane volume ratio of 10:1 to 50:1, for example, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1 or 50:1, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0077] In some embodiments, the heating rate of the first reduction carbonization is 2°C / min to 5°C / min, for example, it can be 2°C / min, 3°C / min, 4°C / min or 5°C / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0078] In some embodiments, the temperature of the first reduction carbonization is 300°C to 400°C, for example, it can be 300°C, 320°C, 330°C, 340°C, 350°C, 360°C, 380°C, 390°C or 400°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0079] In some embodiments, the first reduction carbonization time is 0.5h to 1.5h, for example, it can be 0.5h, 0.6h, 0.8h, 0.9h, 1h, 1.2h, 1.3h, 1.4h or 1.5h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0080] In some embodiments, the heating rate of the second reduction carbonization is 3°C / min to 8°C / min, for example, it can be 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min or 8°C / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0081] In some embodiments, the temperature of the second reduction carbonization is 600°C to 800°C, for example, it can be 600°C, 650°C, 700°C, 750°C or 800°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0082] In some embodiments, the second reduction carbonization time is 1h to 4h, for example, it can be 1h, 2h, 3h or 4h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0083] In some embodiments, the temperature of the third reduction carbonization is 600°C to 800°C, for example, it can be 600°C, 650°C, 700°C, 750°C or 800°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0084] In some embodiments, the third reduction carbonization time is 0.5h to 1h, for example, it can be 0.5h, 0.6h, 0.7h, 0.8h, 0.9h or 1h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0085] As a preferred embodiment of the method provided in this application, the method includes the following steps:

[0086] S1. A sodium tungstate solution is subjected to a hydrothermal reaction at 120℃~200℃ for 6h~24h to obtain a tungsten oxide precursor; the oxide precursor is then subjected to plasma treatment to obtain an oxygen vacancy concentration of 1×10⁻⁶. 19 cm -3 ~5×10 20 cm -3 Nano-sized tungsten oxide powder;

[0087] The average particle size of the nano-tungsten oxide powder is 10nm~80nm;

[0088] S2. The nano-tungsten oxide powder is mixed with the composite carbon source to obtain spherical composite precursor powder;

[0089] The composite carbon source comprises a first carbon source and a second carbon source in a mass ratio of 1:0.5 to 1:2; the first carbon source comprises glucose and / or sucrose; the second carbon source comprises polyethylene glycol.

[0090] The carbon-tungsten molar ratio of the spherical composite precursor powder is 1.02:1 to 1.04:1;

[0091] S3. The spherical composite precursor powder is reduced and carbonized to obtain nano-tungsten carbide powder.

[0092] The reduction carbonization includes a first reduction carbonization, a second reduction carbonization, and a third reduction carbonization performed sequentially; the first reduction carbonization is carried out in a nitrogen atmosphere; the second reduction carbonization is carried out in a mixture of hydrogen and methane, with a hydrogen to methane volume ratio of 2:1 to 5:1; the third reduction carbonization is carried out in a mixture of hydrogen and methane, with a hydrogen to methane volume ratio of 10:1 to 50:1.

[0093] The heating rate for the first reduction carbonization is 2℃ / min~5℃ / min, the temperature is 300℃~400℃, and the time is 0.5h~1.5h;

[0094] The heating rate for the second reduction carbonization is 3℃ / min~8℃ / min, the temperature is 600℃~800℃, and the time is 1h~4h;

[0095] The third reduction carbonization is carried out at a temperature of 600℃~800℃ for a time of 0.5h~1h.

[0096] As a further preferred technical solution, the method includes the following steps:

[0097] S1. A sodium tungstate solution with a concentration of 0.2 mol / L to 0.3 mol / L is subjected to a hydrothermal reaction at a temperature of 120℃ to 200℃ for 6 h to 24 h to obtain a tungsten oxide precursor; the oxide precursor is then subjected to plasma treatment to obtain an oxygen vacancy concentration of 1×10⁻⁶. 19 cm -3 ~5×10 20 cm -3 Nano-sized tungsten oxide powder;

[0098] The average particle size of the nano-tungsten oxide powder is 10nm~80nm;

[0099] S2. The nano-tungsten oxide powder is mixed with the composite carbon source to obtain spherical composite precursor powder;

[0100] The composite carbon source comprises a first carbon source and a second carbon source in a mass ratio of 1:0.5 to 1:2; the first carbon source comprises glucose and / or sucrose; the second carbon source comprises polyethylene glycol.

[0101] The carbon-tungsten molar ratio of the spherical composite precursor powder is 1.02:1 to 1.04:1;

[0102] S3. The spherical composite precursor powder is reduced and carbonized; then cooled to 580℃~620℃ at a cooling rate of 2℃ / min~5℃ / min and held for 0.4h~0.6h; then cooled to room temperature at a cooling rate of 5℃ / min~10℃ / min to obtain nano-tungsten carbide powder with an average grain size ≤150nm.

[0103] The reduction carbonization includes a first reduction carbonization, a second reduction carbonization, and a third reduction carbonization performed sequentially; the first reduction carbonization is carried out in a nitrogen atmosphere; the second reduction carbonization is carried out in a mixture of hydrogen and methane, with a hydrogen to methane volume ratio of 2:1 to 5:1; the third reduction carbonization is carried out in a mixture of hydrogen and methane, with a hydrogen to methane volume ratio of 10:1 to 50:1.

[0104] The heating rate for the first reduction carbonization is 2℃ / min~5℃ / min, the temperature is 300℃~400℃, and the time is 0.5h~1.5h;

[0105] The heating rate for the second reduction carbonization is 3℃ / min~8℃ / min, the temperature is 600℃~800℃, and the time is 1h~4h;

[0106] The third reduction carbonization is carried out at a temperature of 600℃~800℃ for a time of 0.5h~1h.

[0107] Example 1

[0108] This embodiment provides a method for preparing nano-tungsten carbide powder, including:

[0109] S1. A 0.25 mol / L sodium tungstate solution was subjected to a hydrothermal reaction at 160°C for 15 h to obtain a tungsten oxide precursor; the oxide precursor was then subjected to plasma treatment to obtain an oxygen vacancy concentration of 1 × 10⁻⁶. 20 cm -3 Nano-sized tungsten oxide powder;

[0110] The average particle size of the nano-tungsten oxide powder is 40 nm;

[0111] S2. The nano-tungsten oxide powder is mixed with the composite carbon source to obtain spherical composite precursor powder;

[0112] The composite carbon source comprises a first carbon source and a second carbon source in a mass ratio of 1:1; the first carbon source is glucose; and the second carbon source is polyethylene glycol 400.

[0113] The carbon-tungsten molar ratio of the spherical composite precursor powder is 1.03:1;

[0114] S3. The spherical composite precursor powder is reduced and carbonized; then cooled to 600°C at a cooling rate of 3°C / min and held for 0.5h; then cooled to room temperature at a cooling rate of 8°C / min to obtain nano-tungsten carbide powder.

[0115] The reduction carbonization includes a first reduction carbonization, a second reduction carbonization, and a third reduction carbonization performed sequentially; the first reduction carbonization is carried out in a nitrogen atmosphere; the second reduction carbonization is carried out in a mixture of hydrogen and methane, with a hydrogen to methane volume ratio of 3:1; the third reduction carbonization is carried out in a mixture of hydrogen and methane, with a hydrogen to methane volume ratio of 30:1.

[0116] The heating rate for the first reduction carbonization was 3℃ / min, the temperature was 350℃, and the time was 1h.

[0117] The second reduction carbonization heating rate is 5℃ / min, the temperature is 700℃, and the time is 2h;

[0118] The third reduction carbonization was carried out at a temperature of 700°C for 0.8 hours.

[0119] Example 2

[0120] This embodiment provides a method for preparing nano-tungsten carbide powder, including:

[0121] S1. A 0.2 mol / L sodium tungstate solution was subjected to a hydrothermal reaction at 120°C for 24 hours to obtain a tungsten oxide precursor; the oxide precursor was then subjected to plasma treatment to obtain an oxygen vacancy concentration of 1 × 10⁻⁶. 19 cm -3 Nano-sized tungsten oxide powder;

[0122] The average particle size of the nano-tungsten oxide powder is 10 nm;

[0123] S2. The nano-tungsten oxide powder is mixed with the composite carbon source to obtain spherical composite precursor powder;

[0124] The composite carbon source comprises a first carbon source and a second carbon source in a mass ratio of 1:0.5; the first carbon source is glucose; and the second carbon source is polyethylene glycol 400.

[0125] The carbon-tungsten molar ratio of the spherical composite precursor powder is 1.02:1;

[0126] S3. The spherical composite precursor powder is reduced and carbonized; then cooled to 620°C at a cooling rate of 2°C / min and held for 0.4h; then cooled to room temperature at a cooling rate of 5°C / min to obtain nano-tungsten carbide powder.

[0127] The reduction carbonization includes a first reduction carbonization, a second reduction carbonization, and a third reduction carbonization performed sequentially; the first reduction carbonization is carried out in a nitrogen atmosphere; the second reduction carbonization is carried out in a mixture of hydrogen and methane, with a hydrogen to methane volume ratio of 2:1; the third reduction carbonization is carried out in a mixture of hydrogen and methane, with a hydrogen to methane volume ratio of 10:1.

[0128] The heating rate for the first reduction carbonization is 2℃ / min, the temperature is 300℃, and the time is 1.5h;

[0129] The second reduction carbonization heating rate is 3℃ / min, the temperature is 600℃, and the time is 4h;

[0130] The third reduction carbonization is carried out at a temperature of 600°C for 1 hour.

[0131] Example 3

[0132] This embodiment provides a method for preparing nano-tungsten carbide powder, including:

[0133] S1. A 0.3 mol / L sodium tungstate solution was subjected to a hydrothermal reaction at 200°C for 6 hours to obtain a tungsten oxide precursor; the oxide precursor was then subjected to plasma treatment to obtain an oxygen vacancy concentration of 5 × 10⁻⁶. 20 cm -3 Nano-sized tungsten oxide powder;

[0134] The average particle size of the nano-tungsten oxide powder is 80 nm;

[0135] S2. The nano-tungsten oxide powder is mixed with the composite carbon source to obtain spherical composite precursor powder;

[0136] The composite carbon source comprises a first carbon source and a second carbon source in a mass ratio of 1:2; the first carbon source is glucose; and the second carbon source is polyethylene glycol 400.

[0137] The carbon-tungsten molar ratio of the spherical composite precursor powder is 1.04:1;

[0138] S3. The spherical composite precursor powder is reduced and carbonized; then cooled to 580°C at a cooling rate of 5°C / min and held for 0.6h; then cooled to room temperature at a cooling rate of 10°C / min to obtain nano-tungsten carbide powder.

[0139] The reduction carbonization includes a first reduction carbonization, a second reduction carbonization, and a third reduction carbonization performed sequentially; the first reduction carbonization is carried out in a nitrogen atmosphere; the second reduction carbonization is carried out in a mixture of hydrogen and methane, with a hydrogen to methane volume ratio of 5:1; and the third reduction carbonization is carried out in a mixture of hydrogen and methane, with a hydrogen to methane volume ratio of 50:1.

[0140] The heating rate for the first reduction carbonization was 5℃ / min, the temperature was 400℃, and the time was 0.5h.

[0141] The second reduction carbonization heating rate is 8℃ / min, the temperature is 800℃, and the time is 1h;

[0142] The third reduction carbonization is carried out at a temperature of 800°C for 0.5 hours.

[0143] Example 4

[0144] This embodiment provides a method for preparing nano-tungsten carbide powder, which is the same as in Example 1 except that the first reduction carbonization is not performed.

[0145] Example 5

[0146] This embodiment provides a method for preparing nano-tungsten carbide powder, which is the same as in Example 1 except that the second reduction carbide is not performed.

[0147] Example 6

[0148] This embodiment provides a method for preparing nano-tungsten carbide powder, which is the same as in Example 1 except that the third reduction carbide is not performed.

[0149] Example 7

[0150] This embodiment provides a method for preparing nano-tungsten carbide powder, which, in addition to adjusting the plasma treatment parameters, achieves an oxygen vacancy concentration of 1×10⁻⁶ in the nano-tungsten oxide powder. 18 cm -3 Except for the above, everything else is the same as in Example 1.

[0151] Example 8

[0152] This embodiment provides a method for preparing nano-tungsten carbide powder, which, in addition to adjusting the plasma treatment parameters, achieves an oxygen vacancy concentration of 1×10⁻⁶ in the nano-tungsten oxide powder. 21 cm -3 Except for the above, everything else is the same as in Example 1.

[0153] Comparative Example 1

[0154] This comparative example provides a method for preparing nano-tungsten carbide powder, except that the composite carbon source is only the first carbon source, and all other aspects are the same as in Example 1.

[0155] Comparative Example 2

[0156] This comparative example provides a method for preparing nano-tungsten carbide powder, except that the composite carbon source is only the second carbon source, and everything else is the same as in Example 1.

[0157] Comparative Example 3

[0158] This comparative example provides a method for preparing nano-tungsten carbide powder, which is the same as in Example 1 except that plasma treatment is not performed and tungsten oxide precursor is used directly.

[0159] Performance Characterization

[0160] The average particle size, free carbon content, combined carbon content, and oxygen content of the nano-tungsten carbide powders obtained in the above examples and comparative examples were measured, and the results are shown in Table 1.

[0161] The average particle size of the powder was measured using a laser particle size analyzer, the total carbon content of the powder was determined using a carbon-sulfur analyzer, the free carbon and combined carbon content were calculated using the difference method, and the oxygen impurity content of the powder was measured using an oxygen-nitrogen analyzer.

[0162] Table 1

[0163]

[0164] As can be seen from Examples 1 to 3 in Table 1, the method for preparing nano-tungsten carbide powder provided by the present invention can obtain nano-tungsten carbide powder with small grain size, low free carbon, combined carbon close to the theoretical value, and low oxygen impurities under a wide process parameter window.

[0165] A comparison of Examples 4, 5, and 6 with Example 1 shows that omitting the first reduction carbonization prevents the low-temperature removal of adsorbed components from the precursor and pre-reduction treatment, leading to particle agglomeration and growth during subsequent heat treatment, while also increasing the impurity content. Omitting the second reduction carbonization results in the lack of a main reduction-carbonization process in the medium-temperature range, insufficient reduction and conversion of tungsten oxide, low combined carbon content, and increased residual oxygen impurities. Omitting the third reduction carbonization prevents fine-tuning of the carbon composition and deep deoxidation of the tungsten carbide product, resulting in high free carbon in the powder and deviation of combined carbon from the standard range.

[0166] A comparison of Examples 7 and 8 with Example 1 shows that when the oxygen vacancy concentration is too low, the tungsten source reaction activity is insufficient, the reduction and carbonization conversion is incomplete, and the oxygen impurities in the obtained nano-tungsten carbide powder product increase while the combined carbon decreases. When the oxygen vacancy concentration is too high, there are too many active sites on the precursor surface, which easily induces particle coarsening during the heat treatment stage, resulting in an increase in the average particle size of the nano-tungsten carbide powder product and an increase in the free carbon content.

[0167] Comparison of Comparative Examples 1 and 2 with Example 1 shows that when only the first carbon source is used, the carbon layer is prone to agglomeration and clumping during the pyrolysis process, resulting in poor carbon distribution uniformity and a significant increase in free carbon content. When only polyethylene glycol is used as the second carbon source, the continuity of the pyrolysis carbon layer is insufficient, and carbon coating is missing in some areas, resulting in insufficient combined carbon in the nano-tungsten carbide powder product and abnormal grain growth.

[0168] Comparison of Comparative Example 3 and Example 1 shows that the tungsten oxide precursor without plasma treatment has low reactivity, high resistance to reduction and carbonization conversion, requires higher heat treatment conditions, is prone to grain coarsening, and leads to an increase in residual oxygen impurities in the nano-tungsten carbide powder product, with the combined carbon content deviating from the theoretical range.

[0169] In summary, the method for preparing nano-tungsten carbide powder provided in this application enhances the intrinsic reactivity of the tungsten source by performing a hydrothermal reaction on the tungsten source solution and combining it with plasma treatment to regulate the surface oxygen vacancy concentration of the nano-tungsten oxide powder. This allows for reduction carbonization to be completed within 950℃, reducing heat treatment energy consumption and minimizing the risks of nanoparticle sintering and abnormal grain coarsening under high-temperature conditions. The use of a composite carbon source achieves uniform molecular-level coating of the nano-tungsten oxide powder, solving the problems of uneven carbon distribution, excessive free carbon, and deviation of combined carbon from theoretical values ​​associated with traditional mechanical mixing and single-component carbon coating. Combined with reduction carbonization, the final nano-tungsten carbide powder exhibits uniform grain size (not exceeding 150nm), low oxygen impurity content, stable combined carbon content within the standard range, narrow particle size distribution, and no coarse impurities. When used as a raw material to prepare ultrafine-grained WC-Co cemented carbide, it can simultaneously improve the alloy's hardness and fracture toughness. The entire process is adaptable to continuous industrial production, resulting in lower production costs and better product consistency.

[0170] The applicant declares that the above description is only a specific implementation of this application, but the protection scope of this application is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application fall within the protection and disclosure scope of this application.

Claims

1. A method for preparing nano-tungsten carbide powder, characterized in that, The method includes the following steps: A tungsten source solution undergoes a hydrothermal reaction to obtain a tungsten oxide precursor; the oxide precursor is then subjected to plasma treatment to obtain nano-tungsten oxide powder. The nano-tungsten oxide powder is mixed with the composite carbon source to obtain spherical composite precursor powder; The spherical composite precursor powder was reduced and carbonized to obtain nano-tungsten carbide powder.

2. The method according to claim 1, characterized in that, The tungsten source solution is a sodium tungstate solution; And / or, the temperature of the hydrothermal reaction is 120℃~200℃; And / or, the hydrothermal reaction time is 6h~24h.

3. The method according to claim 1 or 2, characterized in that, The plasma treatment reduces the oxygen vacancy concentration of the nano-tungsten oxide powder to 1×10⁻⁶. 19 cm -3 ~5×10 20 cm -3 ; And / or, the average particle size of the nano-tungsten oxide powder is 10nm~80nm.

4. The method according to any one of claims 1 to 3, characterized in that, The composite carbon source includes a first carbon source and a second carbon source with a mass ratio of 1:0.5 to 1:2; The first carbon source includes glucose and / or sucrose; The second carbon source includes polyethylene glycol.

5. The method according to any one of claims 1 to 4, characterized in that, The carbon-tungsten molar ratio of the spherical composite precursor powder is 1.02:1 to 1.04:

1.

6. The method according to any one of claims 1 to 5, characterized in that, The reduction carbonization includes a first reduction carbonization, a second reduction carbonization, and a third reduction carbonization performed sequentially. The first reduction carbonization is carried out in a nitrogen atmosphere; The second reduction carbonization is carried out in a mixture of hydrogen and methane, with a hydrogen to methane volume ratio of 2:1 to 5:

1. The third reduction carbonization is carried out in a mixture of hydrogen and methane, with a hydrogen to methane volume ratio of 10:1 to 50:

1.

7. The method according to claim 6, characterized in that, The heating rate for the first reduction carbonization is 2℃ / min to 5℃ / min; And / or, the temperature of the first reduction carbonization is 300℃~400℃; And / or, the time for the first reduction carbonization is 0.5h to 1.5h.

8. The method according to claim 6 or 7, characterized in that, The heating rate for the second reduction carbonization is 3℃ / min to 8℃ / min; And / or, the temperature of the second reduction carbonization is 600℃~800℃; And / or, the second reduction carbonization time is 1h to 4h.

9. The method according to any one of claims 6 to 8, characterized in that, The temperature for the third reduction carbonization is 600℃~800℃; And / or, the time for the third reduction carbonization is 0.5h to 1h.

10. The method according to claim 1, characterized in that, The method includes the following steps: S1. A sodium tungstate solution is subjected to a hydrothermal reaction at 120℃~200℃ for 6h~24h to obtain a tungsten oxide precursor; the oxide precursor is then subjected to plasma treatment to obtain an oxygen vacancy concentration of 1×10⁻⁶. 19 cm -3 ~5×10 20 cm -3 Nano-sized tungsten oxide powder; The average particle size of the nano-tungsten oxide powder is 10nm~80nm; S2. The nano-tungsten oxide powder is mixed with the composite carbon source to obtain spherical composite precursor powder; The composite carbon source comprises a first carbon source and a second carbon source in a mass ratio of 1:0.5 to 1:2; the first carbon source comprises glucose and / or sucrose; the second carbon source comprises polyethylene glycol. The carbon-tungsten molar ratio of the spherical composite precursor powder is 1.02:1 to 1.04:1; S3. The spherical composite precursor powder is reduced and carbonized to obtain nano-tungsten carbide powder. The reduction carbonization includes a first reduction carbonization, a second reduction carbonization, and a third reduction carbonization performed sequentially. The first reduction carbonization is carried out in a nitrogen atmosphere; the second reduction carbonization is carried out in a mixture of hydrogen and methane, with a hydrogen to methane volume ratio of 2:1 to 5:1; the third reduction carbonization is carried out in a mixture of hydrogen and methane, with a hydrogen to methane volume ratio of 10:1 to 50:

1. The heating rate for the first reduction carbonization is 2℃ / min~5℃ / min, the temperature is 300℃~400℃, and the time is 0.5h~1.5h; The second reduction carbonization heating rate is 3℃ / min~8℃ / min, the temperature is 600℃~800℃, and the time is 1h~4h; The third reduction carbonization is carried out at a temperature of 600℃~800℃ for a time of 0.5h~1h.

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