Porous pure tungsten material and preparation method and application thereof

Abstract

The invention provides a porous pure tungsten material and a preparation method and application thereof, and belongs to the technical field of porous metal material preparation. The pore-forming agent used in the method is tungsten oxide, the product obtained after reduction sintering is pure tungsten, no external impurity residues exist, the purity of the porous pure tungsten material is guaranteed, pores of the obtained porous pure tungsten material are of a three-dimensional communicated net-shaped structure, and the porous pure tungsten material is suitable for application scenes such as filtration and permeation. According to the method, the in-situ volume shrinkage effect generated in the tungsten oxide reduction process is used for pore forming, and directional design and accurate control over the porosity and the pore diameter of the porous pure tungsten material can be achieved by accurately regulating and controlling the particle size and the morphology of the raw material powder, the adding proportion of the pore forming agent and sintering process parameters.

Description

Technical Field

[0001] This invention belongs to the field of porous metal material preparation technology, specifically relating to a porous pure tungsten material, its preparation method, and its application. Background Technology

[0002] Porous pure tungsten materials have broad application prospects in high-temperature filtration, catalyst carriers, aerospace thermal protection, and high-density alloy skeleton materials due to their high melting point, high strength, good thermal conductivity, and corrosion resistance.

[0003] Currently, conventional methods for preparing porous pure tungsten materials mainly include: powder metallurgy sintering-solvent removal method, pore-forming agent method, and fiber sintering method. However, these methods all have certain limitations.

[0004] Powder metallurgy sintering-solvent removal method: Porosity is typically achieved by controlling sintering temperature and time. However, this method is extremely sensitive to the process, making it difficult to precisely control the morphology, size, and uniformity of pore distribution, and the achievable total porosity is limited. Pore-forming agent method: Ammonium carbonate, starch, etc., are commonly used as pore-forming agents, which decompose or volatilize during sintering, leaving pores. However, the decomposition of these pore-forming agents generates gas, which can easily cause cracking of the green body, and residual carbon or other impurities can contaminate the tungsten matrix, affecting the material purity. Summary of the Invention

[0005] The purpose of this invention is to provide a porous pure tungsten material, its preparation method, and its application. This invention uses tungsten oxide as a pore-forming agent, which does not introduce other impurities, thus ensuring the high purity of the porous pure tungsten material; and the prepared porous pure tungsten material has high porosity.

[0006] To achieve the objectives of this invention, the following technical solutions are provided: A method for preparing porous pure tungsten material includes the following steps: Pure tungsten powder and tungsten oxide are mixed and molded to obtain W-WO. x Mixed preform; The W-WO x The mixed preform was sintered in a reducing atmosphere to obtain the porous pure tungsten material; The sintering includes sequentially performing a first sintering and a second sintering; The temperature of the first sintering is 460~800 ℃; The second sintering temperature is 1300~1600 ℃; The porous pure tungsten material has a porosity of 10-65% and a through-pore rate of 92-99%.

[0007] Preferably, the average particle size of the pure tungsten powder is 0.5~10.0 μm.

[0008] Preferably, the tungsten oxide is WO3 and / or WO4. 2.9 The average particle size of the tungsten oxide is 0.1~10.0 μm.

[0009] Preferably, the mass of the tungsten oxide is 1 to 60 wt% of the total mass of pure tungsten powder and tungsten oxide.

[0010] Preferably, the holding time for the first sintering is 0.5 to 15 hours; and the holding time for the second sintering is 0.5 to 4 hours.

[0011] Preferably, the forming is compression molding; the compression molding is cold isostatic pressing or molding.

[0012] The present invention also provides a porous pure tungsten material prepared by the preparation method described above, wherein the porous pure tungsten material has a porosity of 10-65% and a through-pore rate of 92-99%.

[0013] Preferably, the average pore size of the porous pure tungsten material is 0.2~5 μm.

[0014] Preferably, the porous pure tungsten material has a three-dimensional interconnected network structure.

[0015] The present invention also provides the application of the porous pure tungsten material described above in flue gas filtration, catalyst support, or preparation of tungsten-based composite materials.

[0016] This invention provides a method for preparing porous pure tungsten material, comprising the following steps: mixing pure tungsten powder and tungsten oxide to form W-WO x Mixed preform; the W-WO x The mixed preform is sintered under a reducing atmosphere to obtain the porous pure tungsten material. The sintering includes a first sintering and a second sintering sequentially. The temperature of the first sintering is 460~800℃; the temperature of the second sintering is 1300~1600℃; the porosity of the porous pure tungsten material is 10~65%, and the open-pore ratio is 92~99%. This invention adopts a traditional powder metallurgy process, requiring no complex equipment or expensive special pore-forming agents. The process is simple and easy to scale up. The pore-forming agent used in this invention is tungsten oxide, and the product after reduction sintering is pure tungsten without any foreign impurities, ensuring the purity of the porous pure tungsten material. The resulting porous pure tungsten material has a three-dimensional interconnected network structure, suitable for applications such as filtration and permeation.

[0017] Furthermore, this invention utilizes the in-situ volume shrinkage effect generated during the reduction of tungsten oxide to create pores. By precisely controlling the particle size and morphology of the raw material powder, the proportion of the pore-forming agent, and the sintering process parameters, the porosity and pore size of the porous pure tungsten material can be directionally designed and precisely controlled. The prepared porous pure tungsten material has a uniform and controllable structure and can be used for high-temperature flue gas filtration, catalyst support, and as a prefabricated skeleton for preparing highly uniform tungsten-based composite materials (such as tungsten-copper alloys and high-density tungsten alloys), significantly improving the performance consistency and designability of the final composite material. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a flowchart of the process for preparing porous pure tungsten materials according to the present invention; Figure 2 The image shows the morphology of the porous pure tungsten material obtained in Example 1, with a scale bar of 5 μm. Figure 3 The image shows the morphology of the porous pure tungsten material obtained in Example 2, with a scale bar of 5 μm. Figure 4 The image shows the morphology of the porous pure tungsten material obtained in Comparative Example 1, with a scale bar of 5 μm. Figure 5 The image shows the morphology of the porous pure tungsten material obtained in Comparative Example 2, with a scale bar of 5 μm. Detailed Implementation

[0020] This invention provides a method for preparing porous pure tungsten material, comprising the following steps: Pure tungsten powder and tungsten oxide are mixed and molded to obtain W-WO. x Mixed preform; The W-WO x The mixed preform was sintered in a reducing atmosphere to obtain the porous pure tungsten material; The sintering includes sequentially performing a first sintering and a second sintering; The temperature of the first sintering is 460~800 ℃; The second sintering temperature is 1300~1600 ℃; The porous pure tungsten material has a porosity of 10-65% and a through-pore rate of 92-99%.

[0021] In this invention, unless otherwise specified, all raw materials are commercially available products well known to those skilled in the art.

[0022] This invention involves mixing pure tungsten powder and tungsten oxide to form W-WO. x Mixed preform. In this invention, the average particle size of the pure tungsten powder is 0.5~10.0 μm, and in specific embodiments it can be 0.96 μm, 1.4 μm, 3 μm, 5.5 μm or 8 μm; the purity of the pure tungsten powder is 99.5%.

[0023] In this invention, the tungsten oxide is WO3 and / or WO 2.9 The average particle size of the tungsten oxide is 0.1~10.0 μm; the mass of the tungsten oxide is 1~60 wt% of the total mass of pure tungsten powder and tungsten oxide, and in specific embodiments it can be 10 wt%, 30 wt%, 35 wt%, or 45 wt%. This invention controls the tungsten powder particle size within the above range to prevent dense accumulation between smaller particles, which is more likely to occur. Simultaneously, because smaller tungsten powder particles have higher surface activation energy, they can provide a greater sintering driving force, promoting pore closure. This invention controls particle size and morphology uniformity, reducing material densification and allowing more pores to be retained.

[0024] The present invention does not have any particular limitation on the mixing method of pure tungsten powder and tungsten oxide, and conventional mixing methods in the art can be used; in specific embodiments, mixing can be carried out in a ball mill or a three-dimensional mixer; the mixing time is 3~10h.

[0025] In this invention, the forming is compression molding; the compression molding is cold isostatic pressing or molding; in a specific embodiment, it can be cold isostatic pressing; the pressure of the cold isostatic pressing is 100~300MPa.

[0026] Get W-WO x After mixing the preform, the present invention will use the W-WO xThe mixed preform is sintered under a reducing atmosphere to obtain the porous pure tungsten material. In this invention, the reducing atmosphere is one or more of hydrogen, nitrogen, and argon; the sintering includes sequentially performing a first sintering and a second sintering; the temperature of the first sintering is 460~800 °C, which can be 500, 600, or 750 °C in specific embodiments, and the holding time is 0.5~15 h, which can be 2, 5, or 10 h in specific embodiments; the temperature of the second sintering is 1300~1600 °C, which can be 1450, 1500, or 1550 °C in specific embodiments, and the holding time is 0.5~4 h, which can be 1.5 h or 3 h in specific embodiments; the heating rate from room temperature to the first and second sintering stages is 3~10 °C / min, which can be 5 or 8 °C / min in specific embodiments. This invention achieves incomplete sintering of pure tungsten material by first sintering in a reducing atmosphere to reduce tungsten oxide, causing in-situ volume shrinkage and the formation of pores. Subsequently, a second sintering is performed in a reducing atmosphere at 1300–1650 °C to achieve incomplete sintering. This incomplete sintering method is comparable to complete sintering, which typically results in higher material density (even reaching 99%). However, to preserve porosity, this invention controls the process to maintain the material's density within a certain range, achieving incomplete sintering.

[0027] The present invention also provides a porous pure tungsten material prepared by the preparation method described in the above technical solution. The porosity of the porous pure tungsten material is 10-65%, which can be 35, 42 or 55% in specific embodiments; the through porosity is 92-99%, which can be 93% or 95% in specific embodiments; the average pore size of the porous pure tungsten material is 0.2-5 μm, which can be 0.8, 1.06, 2.1 or 3.7 μm in specific embodiments; and the pore structure of the porous pure tungsten material is a three-dimensional interconnected network structure.

[0028] The present invention also provides the application of the porous pure tungsten material described above in high-temperature flue gas filtration, catalyst support, or preparation of tungsten-based composite materials.

[0029] To further illustrate the present invention, the porous pure tungsten material, its preparation method, and its application provided by the present invention will be described in detail below with reference to the accompanying drawings and embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0030] Example 1 according to Figure 1 The process flow diagram shown illustrates the preparation of porous pure tungsten materials. The specific steps are as follows: WO3 powder with a particle size of 18 μm was used as a pore-forming agent. The WO3 powder was crushed by ball milling and passed through a 200-mesh sieve.

[0031] The WO3 green body was mixed with 0.96 μm pure tungsten powder (FSSS) at a ratio of 3:7 in a ball mill for 6 hours. The mixture was then pressed at 200 MPa using cold isostatic pressing to obtain a W-WO3 green body. The green body was then placed in a hydrogen atmosphere sintering furnace and heated to 600 °C at a rate of 5 °C / min, holding for 3.5 hours for WO3 reduction. Subsequently, the temperature was increased to 1450 °C at a rate of 5 °C / min, holding for 80 minutes for incomplete sintering to obtain a porous pure tungsten material.

[0032] Figure 2 The image shows the morphology of the porous pure tungsten material obtained in Example 1, with a scale bar of 5 μm. The porosity of the obtained porous pure tungsten material is 51.87%, the open porosity is 92.82%, and the average pore size is 1.06 μm. The pores are uniformly distributed, forming a three-dimensional interconnected network structure. The tungsten grain size is approximately 2.0 μm, the material surface is crack-free, and the purity is as high as 99.95%.

[0033] Example 2 Using 5.0 μm FSSS WO3 powder as a pore-forming agent, it was mixed with 3.5 μm FSSS pure tungsten powder at a ratio of 1:9 for 9 hours in a three-dimensional mixer. Subsequently, it was pressed into a W-WO3 green body using cold isostatic pressing at 200 MPa. The green body was then placed in a hydrogen atmosphere sintering furnace and heated to 680 °C at a rate of 4 °C / min, holding for 2 hours for WO3 reduction. Subsequently, it was heated to 1550 °C at a rate of 5 °C / min and held for 120 minutes for incomplete sintering to obtain porous pure tungsten material.

[0034] Figure 3 The image shows the morphology of the porous pure tungsten material obtained in Example 2, with a scale bar of 5 μm. The obtained porous pure tungsten material has a porosity of 38.98%, a through-pore rate of 95.65%, and an average pore size of 1.02 μm. The pores are uniformly distributed, exhibiting a three-dimensional interconnected network structure. The tungsten grain size is approximately 5.0 μm, and the material has good permeability, making it suitable for catalyst support applications.

[0035] Example 3 Porous pure tungsten material was prepared according to the preparation method described in Example 2, with the only difference being that the second sintering was carried out at 1450°C for 120 min.

[0036] The obtained porous tungsten material has a porosity of 43.08%, a through-pore rate of 95.39%, and an average pore size of 1.06 μm. Except for the increased porosity, the other porosity properties of the material are not significantly different from those in Example 2.

[0037] Comparative Example 1 Porous pure tungsten material was prepared according to the preparation method described in Example 1, except that WO3 powder pore-forming agent was not added.

[0038] Figure 4 The image shows the morphology of the porous pure tungsten material obtained in Comparative Example 1, with a scale bar of 5 μm. The obtained material has a porosity of only 23.43%, a porosity of 78.07%, and an average pore size of 0.26 μm. The pore structure is mainly closed pores, unevenly distributed, and lacks a three-dimensional interconnected network, resulting in poor fluid permeability.

[0039] Comparative Example 2 Porous pure tungsten material was prepared according to the preparation method described in Example 2, except that WO3 powder pore-forming agent was not added.

[0040] Figure 5 The image shows the morphology of the porous pure tungsten material obtained in Comparative Example 2, with a scale bar of 5 μm. The obtained material has a porosity of 39.24%, a porosity of 81.5%, and an average pore size of 0.83 μm. The pore distribution is slightly improved compared to Comparative Example 2, but it is still dominated by semi-connected pores with a low porosity, making it difficult to meet the requirements for high-efficiency filtration or as a carrier.

[0041] Comparative Example 3 Porous pure tungsten material was prepared according to the preparation method described in Example 2, the only difference being that the FSSS particle size of the pure tungsten powder was 1.35 μm.

[0042] The obtained porous pure tungsten material has a porosity of 25.86%, a through-pore ratio of 92.31%, and an average pore size of 0.61 μm. The pores are uniformly distributed, exhibiting a three-dimensional interconnected network structure, and the tungsten grain size is approximately 2.0 μm. Compared to Example 2, both the porosity and through-pore ratio of the material decreased, and the pore size was also significantly reduced because only the original channels from the pressing process were retained.

[0043] Comparative Example 4 Porous pure tungsten material was prepared according to the preparation method described in Example 3, with the only difference being that the second sintering was carried out at 1650°C for 120 min.

[0044] The obtained porous tungsten material has a porosity of 23.57%, a through-pore rate of 88.73%, and an average pore size of 0.99 μm. The closed-pore rate of the pore structure is significantly increased, and the average pore size is also significantly reduced.

[0045] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a porous pure tungsten material, characterized in that, Includes the following steps: Pure tungsten powder and tungsten oxide are mixed and molded to obtain W-WO. x Mixed preform; The W-WO x The mixed preform was sintered in a reducing atmosphere to obtain the porous pure tungsten material; The sintering includes sequentially performing a first sintering and a second sintering; The temperature of the first sintering is 460~800 ℃; The second sintering temperature is 1300~1600 ℃; The porous pure tungsten material has a porosity of 10-65% and a through-pore rate of 92-99%.

2. The preparation method according to claim 1, characterized in that, The average particle size of the pure tungsten powder is 0.5~10.0 μm.

3. The preparation method according to claim 1, characterized in that, The tungsten oxide is WO3 and / or WO 2.9 The average particle size of the tungsten oxide is 0.1~10.0 μm.

4. The preparation method according to claim 1, characterized in that, The mass of the tungsten oxide is 1 to 60 wt% of the total mass of pure tungsten powder and tungsten oxide.

5. The preparation method according to claim 1, characterized in that, The holding time for the first sintering is 0.5 to 15 hours; the holding time for the second sintering is 0.5 to 4 hours.

6. The preparation method according to claim 1, characterized in that, The forming process is compression molding; the compression molding is cold isostatic pressing or molding.

7. The porous pure tungsten material prepared by the preparation method according to any one of claims 1 to 6, characterized in that, The porous pure tungsten material has a porosity of 10-65% and a through-pore rate of 92-99%.

8. The porous pure tungsten material according to claim 7, characterized in that, The average pore size of the porous pure tungsten material is 0.2~5 μm.

9. The porous pure tungsten material according to claim 7, characterized in that, The porous pure tungsten material has a three-dimensional interconnected network structure.

10. The use of the porous pure tungsten material according to any one of claims 7 to 9 in flue gas filtration, catalyst support, or preparation of tungsten-based composite materials.

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