Porous tungsten workpiece and preparation method thereof, tungsten-based diffusion cathode and electronic device

Abstract

The invention discloses a porous tungsten workpiece and a preparation method thereof, a tungsten-based diffusion cathode and an electronic device, and belongs to the technical field of metallurgical materials. The preparation method of the porous tungsten workpiece comprises the steps that S1, tungsten powder is pressed to obtain a powder pressed blank; s2, sintering the pressed blank to obtain a tungsten framework; s3, the tungsten framework is subjected to manganese infiltration treatment, and a manganized tungsten-manganese alloy is obtained; machining the tungsten-manganese alloy to obtain a target tungsten-manganese alloy product; and S5, the target tungsten-manganese alloy product is subjected to heat preservation for 2-4 h under the conditions that the vacuum degree ranges from 0.01 Pa to 10 Pa and the temperature ranges from 1350 DEG C to 1550 DEG C, manganese removal treatment is conducted, and the porous tungsten workpiece is obtained. The porosity of the prepared porous tungsten workpiece is 10-30%, the residual amount of infiltrated manganese is smaller than 0.01 wt.%, the pore characteristic is consistent with that of a tungsten framework, and the boundary dimension linear deformation is smaller than 0.1%. The tungsten-based diffusion cathode material has the excellent effects of stable structure, high strength, high purity and high dimensional precision.

Description

Technical Field

[0001] The present application relates to the technical field of metallurgical materials, and in particular to a porous tungsten component and a preparation method thereof, a tungsten-based diffusion cathode and an electronic device. Background Art

[0002] Tungsten-based diffused cathodes play a vital role in modern electronics, primarily used in microwave vacuum electronic devices such as klystrons and traveling wave tubes, and are widely used in communications, radar, and other fields. As an electron emission source, tungsten-based diffused cathodes can release electrons under specific operating conditions. As the core component of diffused cathodes, the performance of porous tungsten directly affects the output performance and lifespan of microwave sources. Its excellent electron emission properties can improve the efficiency and stability of electronic devices.

[0003] However, the current method of preparing porous tungsten by infiltration of copper still has some deficiencies and disadvantages; in particular, there are some problems with the copper removal process during the preparation and purification of porous tungsten alloy materials; for example, incomplete copper removal will distort parameters such as the porosity and pore size of the tungsten-based diffusion cathode, and a high residual copper content will also affect the electron emission capability of the cathode, reduce the emission current density and emission efficiency, hinder the escape of electrons, and thus affect the performance of the cathode; and the strong acid chemical reagents used in the copper removal process damage the tungsten substrate, resulting in a rough surface, structural damage, and reduced mechanical strength. Summary of the Invention

[0004] The main purpose of the present application is to provide a porous tungsten part and its preparation method, a tungsten-based diffusion cathode and an electronic device, so as to solve the problems in the prior art of using copper as the tungsten matrix infiltration metal, such as a large amount of copper residue, easy distortion of the porosity and pore size of the tungsten matrix, and the destruction of the structure and strength of the tungsten matrix during the copper removal process.

[0005] In order to achieve the above object, according to one aspect of the present application, a method for preparing a porous tungsten component is provided, comprising the following steps:

[0006] Step S1: Compressing tungsten powder to obtain a powder compact;

[0007] Step S2: sintering the powder compact to obtain a tungsten skeleton;

[0008] Step S3: performing a manganese infiltration treatment on the tungsten skeleton to obtain a manganese infiltrated tungsten-manganese alloy;

[0009] Step S4: machining the manganese-infiltrated tungsten-manganese alloy to obtain a target tungsten-manganese alloy product;

[0010] Step S5: The target tungsten-manganese alloy product is kept at a vacuum degree of 0.01-10 Pa and a temperature of 1350-1550° C. for 2-4 hours to perform a manganese removal treatment to obtain a porous tungsten product.

[0011] Furthermore, in step S5, the conditions for the manganese removal treatment include: a vacuum degree of 0.1 to 1 Pa, a manganese removal temperature of 1400 to 1550° C., and a manganese removal holding time of 2 to 4 hours.

[0012] Furthermore, compared with the outer dimensions of the tungsten skeleton, the linear deformation of the porous tungsten component is less than 0.1%.

[0013] Furthermore, the porosity of the porous tungsten component is 10-30%, preferably 15-30%.

[0014] Furthermore, the average pore size of the porous tungsten component is 1.2 to 2 μm, preferably 1.5 to 1.7 μm.

[0015] Furthermore, the residual content of infiltrated manganese in the porous tungsten component is less than 0.01 wt.%, preferably less than 0.008 wt.%.

[0016] Furthermore, the equipment for manganese removal treatment is a vacuum demetallization furnace.

[0017] Furthermore, in step S3, the process of manganese infiltration treatment includes: keeping the tungsten skeleton and the manganese material in a first non-oxidizing atmosphere at a temperature of 1400-1600° C. for 0.5-2 hours to obtain a manganese infiltrated tungsten-manganese alloy.

[0018] Furthermore, the temperature of the manganese infiltration treatment is 1500-1600° C., and the holding time of the manganese infiltration treatment is 0.5-2.0 h.

[0019] Furthermore, the heating rate during the manganese infiltration treatment is 5 to 15° C. / min.

[0020] Furthermore, the first non-oxidizing atmosphere is a hydrogen atmosphere.

[0021] Furthermore, the volume ratio of the tungsten skeleton to the manganese material is 1:(1.1-2).

[0022] Furthermore, the manganese material is a manganese ingot.

[0023] Furthermore, the equipment for the manganese infiltration treatment is an infiltration furnace.

[0024] Furthermore, in step S1, the pressing process includes: maintaining the tungsten powder under a pressing force of 200 to 250 MPa for 90 to 180 seconds to obtain a powder compact.

[0025] Furthermore, in step S2, the sintering process includes: keeping the powder compact in a second non-oxidizing atmosphere at a temperature of 1800-2150° C. for 3-8 hours to obtain a tungsten skeleton.

[0026] Furthermore, in step S4, the machining includes at least one of wire cutting, centerless cylindrical grinding and turning.

[0027] Furthermore, in step S1, the pressing force is 200-220 MPa, and the holding time is 150-180 s.

[0028] Furthermore, the pressing equipment is a cold isostatic press.

[0029] Furthermore, the tungsten powder has a Fisher particle size of 6 to 10 μm.

[0030] Furthermore, in step S2, the sintering temperature is 1850-1950°C, and the sintering holding time is 6-8 hours.

[0031] Furthermore, the second non-oxidizing atmosphere is a hydrogen atmosphere.

[0032] Furthermore, the sintering equipment is a medium frequency induction furnace.

[0033] Furthermore, the porosity of the tungsten skeleton is 10 to 30%, preferably 15 to 30%.

[0034] According to a second aspect of the present application, a porous tungsten component is provided, which is prepared using the above-mentioned preparation method.

[0035] Furthermore, the porosity of the porous tungsten component is 10-30%, preferably 15-30%.

[0036] Furthermore, the average pore size of the porous tungsten component is 1.2 to 2 μm, preferably 1.5 to 1.7 μm.

[0037] Furthermore, the residual content of infiltrated manganese in the porous tungsten component is less than 0.01 wt.%, preferably less than 0.008 wt.%.

[0038] According to the third aspect of the present application, a tungsten-based diffusion cathode is provided, comprising a porous tungsten skeleton and an active substance, wherein the active substance is loaded in the pores of the porous tungsten skeleton; the porous tungsten skeleton is a porous tungsten part prepared by the above-mentioned preparation method or the above-mentioned porous tungsten part.

[0039] According to a fourth aspect of the present application, an electronic device is provided, comprising a tungsten-based diffusion cathode; the tungsten-based diffusion cathode is the above-mentioned tungsten-based diffusion cathode.

[0040] Compared with the prior art, this application has the following beneficial effects:

[0041] The present application provides a porous tungsten component and a preparation method thereof, a tungsten-based diffusion cathode and an electronic device; a tungsten-manganese alloy is obtained by subjecting a tungsten skeleton with a porosity of 10 to 30% to a melt infiltration manganese process, the tungsten-manganese alloy is mechanically processed into a desired shape, and the porous tungsten component obtained by the manganese removal process still has a porosity of 10 to 30%, a residual content of the infiltrated metal is less than 0.01 wt.%, the pore characteristics are consistent with those of the tungsten skeleton, and the linear deformation of the outer dimensions is less than 0.1%; as a tungsten-based diffusion cathode material, it has excellent effects of stable structure, high strength, high purity and high dimensional accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The drawings that constitute part of this application are used to provide a further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation on this application. In the drawings:

[0043] Figure 1 This is a scanning electron microscope image of the fracture morphology of the tungsten skeleton prepared in Example 1 of the present application before manganese infiltration;

[0044] Figure 2 This is a metallographic image of the tungsten skeleton prepared in Example 1 of the present application after manganese infiltration;

[0045] Figure 3 This is a scanning electron microscope image of the fracture morphology of the tungsten skeleton prepared in Example 1 of the present application after manganese removal. DETAILED DESCRIPTION

[0046] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and embodiments.

[0047] In traditional technology, copper is used as the infiltration metal to prepare porous tungsten parts. Due to the material properties of copper, the residual copper content in the porous tungsten parts after conventional chemical copper removal is relatively high. The chemical copper removal process can easily destroy the tungsten matrix structure and reduce its strength, which will reduce the performance of the tungsten-based diffusion cathode. The vacuum copper removal process requires high vacuum degree and removal temperature, which is not easy to operate.

[0048] In order to achieve the above object, according to one aspect of the present application, a method for preparing a porous tungsten component is provided, comprising the following steps:

[0049] Step S1: Compressing tungsten powder to obtain a powder compact;

[0050] Step S2: sintering the powder compact to obtain a tungsten skeleton;

[0051] Step S3: performing a manganese infiltration treatment on the tungsten skeleton to obtain a manganese infiltrated tungsten-manganese alloy;

[0052] Step S4: machining the manganese-infiltrated tungsten-manganese alloy to obtain a target tungsten-manganese alloy product;

[0053] Step S5: The target tungsten-manganese alloy product is kept at a vacuum degree of 0.01-10 Pa and a temperature of 1350-1550° C. for 2-4 hours to perform a manganese removal treatment to obtain a porous tungsten product.

[0054] The porous tungsten microstructure in this application is produced by the incomplete densification of a tungsten powder blank after high-temperature sintering. Its characteristic is that it cannot be changed after high-temperature sintering. The factors affecting the purity of the porous tungsten are mainly the purity of the tungsten powder and the residual content of the infiltrated metal, which places higher requirements on the residual content of the infiltrated metal. After extensive testing and research, this application found that the residual content of the infiltrated metal in porous tungsten parts prepared by using manganese instead of copper as the infiltrated metal of the porous tungsten base material is low. Specifically, a tungsten skeleton with a porosity of 10-30% is subjected to a manganese infiltration process to obtain a tungsten-manganese alloy. The tungsten-manganese alloy is then machined into the desired shape and the manganese is removed to obtain a porous tungsten part with a porosity of 10-30%, a residual content of less than 0.01 wt.%, and pore characteristics that are essentially consistent with the tungsten skeleton. Compared to the external dimensions of the tungsten skeleton, the linear deformation of the porous tungsten part is less than 0.1%. The porous tungsten-based material prepared by this application method has excellent structural stability, high strength, high purity, and high dimensional accuracy.

[0055] In the above-mentioned preparation method of the present application, the specific methods and equipment for pressing, sintering, infiltration of manganese, machining, etc. of tungsten powder can be selected from the existing technology; the main innovation of the present application is to utilize the performance characteristics of manganese materials to replace copper materials, avoiding the above-mentioned defects caused by copper materials. Replacing copper with manganese can significantly reduce the amount of residual infiltration metal in porous tungsten parts; for the entire preparation process, if process conditions that are more suitable for manganese materials are adopted, the residual amount of manganese can be further reduced, the deformation rate of the porous tungsten base can be reduced, and the stability and strength of the porous tungsten base structure can be guaranteed. During the entire preparation process, it is particularly important to remove manganese from the target tungsten-manganese alloy product; for example, the target tungsten-manganese alloy product is placed in a vacuum demetallization furnace and kept warm for 2 to 4 hours under the conditions of controlling the vacuum degree to be 0.01 to 10 Pa and the temperature to be 1350 to 1550° C.; for another example, the manganese removal vacuum degree is any value among 0.01 Pa, 0.1 Pa, 1 Pa, 2 Pa, 3 Pa, 4 Pa, 5 Pa, 6 Pa, 7 Pa, 8 Pa, 9 Pa, and 10 Pa, or a range between any two of them; the manganese removal temperature is any value among 1550° C., 1500° C., 1450° C., 1400° C., and 1350° C., or a range between any two of them; and the manganese removal holding time is any value among 2 h, 2.5 h, 3 h, 3.5 h, and 4 h, or a range between any two of them. Under the above-mentioned vacuum and high temperature conditions, the manganese material can be fully evaporated and removed from the pores of the tungsten skeleton, leaving only the tungsten skeleton. The residual manganese is small, and the original porous structure and mechanical properties such as strength and hardness of the tungsten skeleton are not affected. The degree of deformation is very small. Under the above-mentioned vacuum degree, the evaporation of manganese is easier.

[0056] In some embodiments, in step S1, the tungsten powder has a Fisher particle size of 6 to 10 μm; for example, any value selected from 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, or 10 μm, or any range therebetween; for example, 6.5 to 10 μm; further, 6.5 to 8 μm. The particle size of the tungsten powder can directly affect the microstructure of the final porous tungsten component, and thus the electron emission performance of the porous tungsten component as a diffusion cathode. By limiting the tungsten powder particle size to the above range, the porosity and pore size of the prepared porous tungsten component can meet the required performance, which is more conducive to its electron emission performance.

[0057] In some embodiments, in step S1, the pressing process includes: holding the tungsten powder under a pressing force of 200-250 MPa for 90-180 seconds to obtain a powder compact; for example, the pressing force is any value among 200 MPa, 210 MPa, 220 MPa, 230 MPa, 240 MPa, and 250 MPa, or a range value between any two of them; the holding time is any value among 90 seconds, 100 seconds, 110 seconds, 120 seconds, 130 seconds, 140 seconds, 150 seconds, 160 seconds, 170 seconds, and 180 seconds, or a range value between any two of them; further, the pressing force is 200-220 MPa, and the holding time is 150-180 seconds; further, it is 200-210 MPa, and the holding time is 170-180 seconds; and the equipment used in the pressing process is a cold isostatic press. By controlling the pressing force of tungsten powder within the above range, the obtained compact has an appropriate compaction density and the required porosity, providing a good billet basis for the subsequent sintering process; it is conducive to obtaining a compact with a preset porosity microstructure; by optimizing the above process parameters, a compact with high compactness and uniform structure can be obtained, thereby improving the performance and quality of the final porous tungsten parts.

[0058] In some embodiments, in step S2, the sintering process includes: keeping the powder compact in a second non-oxidizing atmosphere at a temperature of 1800 to 2150° C. for 3 to 8 hours to obtain a tungsten skeleton; for example, the sintering temperature is any value among 1800, 1850, 1900, 1950, 2000, 2050, 2100, 2150° C. or a range value between any two of them; the holding time is any value among 3, 4, 5, 6, 7, 8 hours or a range value between any two of them; further, sintering The temperature is 1850-1950° C., and the holding time is 6-8 hours; the second non-oxidizing atmosphere can be a hydrogen atmosphere; the sintering equipment is a medium-frequency induction furnace; the porosity of the tungsten skeleton is 10-30%, preferably 15-30%, and further 20-30%; the average pore diameter is 1.2-2 microns, and further preferably 1.5-1.7 microns; the closed porosity is less than 1%, and further less than 0.5%; the residual content of infiltrated manganese in the porous tungsten part is less than 0.01wt.%, and further less than 0.008wt.%. Sintering is performed in a non-oxidizing atmosphere to avoid oxidation of the tungsten material and thus affect the performance of the tungsten material as a diffusion cathode material; sintering is preferably performed in hydrogen, which not only avoids the formation of tungsten oxide in the tungsten material, but also hydrogen, as a reducing gas, can reduce the oxide on the tungsten surface back to a metallic state at high temperature, thereby protecting the tungsten powder from oxidation during the sintering process and maintaining its purity and original properties; at the same time, when the sintering temperature and sintering time are controlled within the above range, the density, microstructure, porosity and mechanical properties of the prepared tungsten skeleton can meet the use requirements and meet its performance as a diffusion cathode material, such as having a porous structure.

[0059] In some embodiments, in step S3, the volume ratio of the tungsten skeleton to the manganese material is 1:(1.1-2); for example, any value selected from 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, and 1:2, or any range therebetween. By controlling the volume of the manganese material and the tungsten material within the above range, manganese can fully fill the pores of the tungsten skeleton, which is beneficial to the mechanical properties, porous structure, and density of the tungsten-manganese alloy, and is beneficial to the difficulty or effectiveness of the subsequent manganese removal operation.

[0060] In some embodiments, in step S3, the manganese infiltration treatment process includes: maintaining the tungsten skeleton and manganese material in a first non-oxidizing atmosphere at a temperature of 1400-1600°C for 0.5-2 hours to obtain a manganese-infiltrated tungsten-manganese alloy. For example, the heating temperature is any value among 1400°C, 1450°C, 1500°C, 1550°C, and 1600°C, or a range therebetween; and the holding time is any value among 0.5, 1, 1.5, and 2 hours, or a range therebetween. By infiltrating manganese in the first non-oxidizing atmosphere, oxidation of tungsten and manganese to form impurities such as manganese oxide or tungsten oxide can be avoided, thereby preventing the tungsten and manganese from being oxidized to form impurities such as manganese oxide or tungsten oxide, which could affect the properties of the tungsten material. This helps form a purer alloy material, which in turn improves the electrical properties of the tungsten material as a diffusion cathode material. The temperature and time of manganese infiltration will directly affect the degree of manganese diffusion in the tungsten matrix, the thickness of the manganese infiltration layer, the microstructure and the performance of the final product; as the temperature rises, the fluidity of the manganese liquid improves, and manganese can be deeply and evenly distributed in the tungsten pores. The extension of the holding time will provide more time for the manganese liquid to complete the capillary penetration process and form a stable alloy structure; using a manganese infiltration temperature of 1400-1600℃ and a holding time of 0.5-2h is more conducive to the difficulty of subsequent processing and post-processing of the product, such as mechanical processing and manganese removal; the process parameters such as the heating temperature and time of manganese infiltration not only take into account the manganese In addition to the characteristics of the material itself, the quality and performance of the tungsten-manganese alloy prepared using the process conditions must also be considered, because the quality of the tungsten-manganese alloy must be suitable for mechanical processing in step S4 to obtain a formed product. The effect of removing manganese from the tungsten-manganese alloy in step S5 must also be considered. It is necessary to ensure that manganese in the tungsten-manganese alloy is easy to remove and the residual amount is extremely small, and the manganese removal process cannot affect the structural characteristics of the tungsten skeleton itself, otherwise it will affect its performance as a diffusion cathode; therefore, the manganese infiltration process, especially the heating temperature and heating time, in addition to being adapted to the characteristics of manganese itself, also needs to be adapted to the subsequent processing steps, and its process processing has a complex impact mechanism on the subsequent processing.

[0061] In some embodiments, in step S3, the heating rate in the manganese infiltration treatment is 5 to 15°C / min; further, 8 to 12°C / min. By controlling the heating rate, the manganese material can be gradually infiltrated into the tungsten skeleton, which is beneficial to improving the effect and quality of the manganese infiltration. The manganese infiltration treatment temperature is further controlled at 1500 to 1600°C, and the holding time is controlled at 0.5 to 2.0 hours; the first non-oxidizing atmosphere uses a hydrogen atmosphere; further, the temperature is 1550 to 1600°C, and the holding time is controlled at 0.5 to 2.0 hours. The use of the above-mentioned more suitable temperature and holding time is conducive to the proper diffusion of manganese in the tungsten skeleton, forming a stable and uniform manganese infiltration layer, while not destroying the original porous structure and mechanical properties of the tungsten skeleton, providing good conditions for subsequent mechanical processing and manganese removal processes. The equipment for the above-mentioned manganese infiltration treatment can be an infiltration furnace; the manganese material selected is a manganese ingot, and other pure manganese materials with good compatibility with the tungsten material can also be used.

[0062] In some embodiments, in step S4, the machining includes at least one of wire cutting, centerless cylindrical grinding, and turning; the target tungsten-manganese alloy product is in the form of a sheet, a rod, or a block. The machining methods described above can be selected from existing technologies, as long as the tungsten-manganese alloy is processed into the desired profile component. The tungsten-manganese alloy prepared in this application, which has suitable machining properties, is more conducive to the precision and molding effect of the molded product, and is conducive to the high performance and high dimensional precision of the tungsten material as a diffusion cathode.

[0063] In order to obtain porous tungsten parts with higher purity, stable structure and good performance, which are more suitable for the application of high-performance tungsten-based diffusion cathodes, the manganese removal treatment process conditions are optimized; in some embodiments, in step S5, the manganese removal treatment conditions include: a vacuum degree of 0.1 to 1 Pa, a manganese removal temperature of 1400 to 1550°C, and a manganese removal holding time of 2 to 4 hours; the manganese removal treatment equipment is a vacuum demetallization furnace. By adopting a more suitable vacuum degree, evaporation temperature and evaporation time, it is possible to ensure that manganese is removed from the tungsten-manganese alloy quickly, effectively and completely, while maintaining the original performance and structural stability of the tungsten material, avoiding damage to the surface of the tungsten skeleton and changes in the pore structure, and ensuring that the residual manganese content is less than 0.01wt.%, further less than 0.008wt.%; at the same time, the linear deformation of the porous tungsten component after manganese removal is less than 0.1%, further less than 0.08%; the porosity remains 10-30%, further 15-30%; further 20-30%; the closed porosity of the porous tungsten component is less than 0.5%; and the average pore size of the porous tungsten component is 1.2-2μm, further 1.5-1.7μm.

[0064] In some specific embodiments, the preparation method of porous tungsten includes: step S1: pressing tungsten powder with a Fisher particle size of 8 μm, a pressing force of 200 MPa, and holding the pressure for 180S to obtain a powder compact; step S2: sintering the powder compact, the sintering temperature is 1900°C, and the heat preservation is carried out for 6 hours to obtain a tungsten skeleton; step S3: performing melt infiltration manganese treatment on the tungsten skeleton, the volume ratio of the manganese ingot to the pores of the tungsten skeleton is 1.2, and the temperature is raised to 1500°C at 10°C / min in a hydrogen atmosphere, and the temperature is kept for 1.5 hours to obtain a manganese-infiltrated tungsten-manganese alloy; step S4: machining the manganese-infiltrated tungsten-manganese alloy to obtain a target tungsten-manganese alloy product; step S5: performing manganese removal treatment on the target tungsten-manganese alloy product, under a vacuum degree of 1Pa, the temperature is 1550°C, and the temperature is kept for 3 hours to obtain a porous tungsten part.

[0065] According to a second aspect of the present application, a porous tungsten component is provided. The porous tungsten component is prepared using the above-mentioned preparation method.

[0066] In some embodiments, the porosity of the porous tungsten part is 10-30%, further 15-30%; the average pore size of the porous tungsten part is 1.2-2 microns, further 1.5-1.7 microns; the closed porosity of the porous tungsten part is less than 1%, further less than 0.8%; the residual content of infiltrated manganese in the porous tungsten part is less than 0.01wt.%, further less than 0.008wt.%; compared with the external dimensions of the tungsten skeleton, the linear deformation of the porous tungsten part is less than 0.1%; further less than 0.08%. The porosity of the porous tungsten parts obtained by the above preparation method still maintains the original 10% to 30%, the pore size has not changed significantly, the manganese residue is very small, the linear deformation rate of the tungsten skeleton is also very small, and the microstructure and mechanical properties of the tungsten skeleton have almost no change before manganese infiltration and after manganese removal; it shows that the above-mentioned manganese infiltration process conditions of this application can be used to successfully prepare tungsten-manganese alloy and are more suitable for processing and forming, and the above-mentioned manganese removal process conditions can be used to successfully remove the manganese material in the tungsten skeleton and almost do not change the original structure and properties of the tungsten skeleton, so that the porous tungsten parts have high performance and high precision and can be used as tungsten-based diffusion cathode materials.

[0067] The porous tungsten parts prepared in this application have high performance and high precision, and can be used as core components of diffusion cathodes. The material has the characteristics of a porous structure that is conducive to the diffusion of active substances, and has the characteristics of tungsten's high melting point, burn-out resistance, and high hardness. The porous tungsten microstructure and tungsten purity prepared in this application are more conducive to the emission current and life of the diffusion cathode.

[0068] According to the third aspect of the present application, a tungsten-based diffusion cathode is provided, comprising a porous tungsten skeleton and an active substance, wherein the active substance is loaded in the pores of the porous tungsten skeleton; the porous tungsten skeleton is a porous tungsten part prepared by the above-mentioned preparation method or the above-mentioned porous tungsten part.

[0069] According to a fourth aspect of the present application, an electronic device is provided, comprising a tungsten-based diffusion cathode; the tungsten-based diffusion cathode is the above-mentioned tungsten-based diffusion cathode.

[0070] The present application is further described in detail below with reference to specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in this application.

[0071] The tungsten powder of the present application is pure tungsten material, and the manganese ingot is pure manganese material, both of which are prior art and commercially available.

[0072] Example 1

[0073] Step S1: Compression molding: tungsten powder with a Fisher particle size of 8 μm is loaded into a rubber mold of a cold isostatic press, the inner cavity size of the rubber mold is 110×150×400 mm, and then the rubber mold is locked after mechanical vibration; the rubber mold filled with the material is placed in a cold isostatic press for pressing, with a pressing force of 200 MPa and a holding pressure of 180 seconds; after demolding, a powder compact of 110×130×180 is obtained;

[0074] Step S2: high temperature sintering: the pressed powder compact is placed in a medium frequency induction furnace for sintering in a hydrogen atmosphere at a sintering temperature of 1950°C for 6 hours to obtain a tungsten skeleton; Figure 1 As shown;

[0075] Step S3: high-temperature infiltration: add the tungsten skeleton and manganese ingot from step S2 into an alumina ceramic crucible in an infiltration furnace, with the volume ratio of the manganese ingot to the pores of the tungsten skeleton being 1.1, and heat to 1550°C at a rate of 10°C / min in a hydrogen atmosphere, hold for 1.5 hours, and cool to room temperature with the furnace to obtain a manganese-infiltrated tungsten-manganese alloy; Figure 2 As shown;

[0076] Step S4: machining: machining the tungsten-manganese alloy obtained in step S3 by wire cutting and centerless cylindrical grinding to obtain a tungsten-manganese alloy product meeting the target size;

[0077] Step S5: Vacuum high-temperature evaporation to remove manganese: Place the tungsten-manganese alloy product from step S4 in an alumina ceramic crucible in a vacuum demetallization furnace, at a vacuum degree of 1 Pa, a temperature of 1550° C., and keep warm for 3 hours to obtain a porous tungsten product; Figure 3 shown.

[0078] Example 2

[0079] Step S1: Compression molding: tungsten powder with a Fisher particle size of 6.5 μm is loaded into a rubber mold of a cold isostatic press, the inner cavity size of the rubber mold is 110×150×400 mm, and then the rubber mold is locked after mechanical vibration; the rubber mold filled with the material is placed in a cold isostatic press for pressing, with a pressing force of 220 MPa and a holding pressure of 150 seconds; after demolding, a powder compact of 110×130×180 is obtained;

[0080] Step S2: high-temperature sintering: placing the pressed powder compact into a medium-frequency induction furnace for sintering in a hydrogen atmosphere at a sintering temperature of 1850° C. for 8 hours to obtain a tungsten skeleton;

[0081] Step S3: high-temperature infiltration: the tungsten skeleton and manganese ingot from step S2 are added to an alumina ceramic crucible in an infiltration furnace, with the volume ratio of the manganese ingot to the pores of the tungsten skeleton being 1.5. The temperature is raised to 1550°C at a rate of 8°C / min in a hydrogen atmosphere, kept at this temperature for 2 hours, and cooled to room temperature with the furnace to obtain a manganese-infiltrated tungsten-manganese alloy.

[0082] Step S4: machining: machining the tungsten-manganese alloy obtained in step S3 by wire cutting and centerless cylindrical grinding to obtain a tungsten-manganese alloy product meeting the target size;

[0083] Step S5: vacuum high-temperature evaporation to remove manganese: the tungsten-manganese alloy product of step S4 is placed in an alumina ceramic crucible of a vacuum demetallization furnace, at a vacuum degree of 0.1 Pa and a temperature of 1400° C. for 4 hours to obtain a porous tungsten product.

[0084] Example 3

[0085] Step S1: Compression molding: tungsten powder with a Fisher particle size of 8 μm is loaded into a rubber mold of a cold isostatic press, the inner cavity size of the rubber mold is 110×150×400 mm, and then the rubber mold is locked after mechanical vibration; the rubber mold filled with the material is placed in a cold isostatic press for pressing, with a pressing force of 250 MPa and a holding pressure of 90 seconds; after demolding, a powder compact of 110×130×180 is obtained;

[0086] Step S2: high-temperature sintering: placing the pressed powder compact into a medium-frequency induction furnace for sintering in a hydrogen atmosphere at a sintering temperature of 1950° C. for 6 hours to obtain a tungsten skeleton;

[0087] Step S3: high-temperature infiltration: the tungsten skeleton and manganese ingot from step S2 are added to an alumina ceramic crucible in an infiltration furnace, with the volume ratio of the manganese ingot to the pores of the tungsten skeleton being 2. The temperature is raised to 1600°C at a rate of 12°C / min in a hydrogen atmosphere, kept at this temperature for 0.5h, and cooled to room temperature with the furnace to obtain a manganese-infiltrated tungsten-manganese alloy.

[0088] Step S4: machining: machining the tungsten-manganese alloy obtained in step S3 by wire cutting and centerless cylindrical grinding to obtain a tungsten-manganese alloy product meeting the target size;

[0089] Step S5: vacuum high-temperature evaporation to remove manganese: the tungsten-manganese alloy product of step S4 is placed in an alumina ceramic crucible of a vacuum demetallization furnace, at a vacuum degree of 0.1 Pa and a temperature of 1500° C. for 3 hours to obtain a porous tungsten product.

[0090] Example 4

[0091] The difference between Example 4 and Example 1 is that the manganese removal conditions in step S5 are replaced as follows: vacuum degree is 0.01 Pa, manganese removal temperature is 1350° C., and manganese removal holding time is 4 h.

[0092] Example 5

[0093] The difference between Example 5 and Example 1 is that the manganese removal conditions in step S5 are replaced as follows: vacuum degree is 10 Pa, manganese removal temperature is 1550° C., and manganese removal holding time is 4 h.

[0094] Example 6

[0095] The difference between Example 6 and Example 1 is that the manganese infiltration temperature in step S3 is replaced with 1400° C. and the holding time is 2 h.

[0096] Example 7

[0097] The difference between Example 7 and Example 1 is that the sintering temperature in step S2 is replaced with 2150° C. and the holding time is 6 h.

[0098] Comparative Example 1

[0099] The difference between Comparative Example 1 and Example 1 is that copper is used instead of manganese to carry out steps S3 to S5 respectively;

[0100] The specific operations are as follows:

[0101] Step S3: high-temperature copper infiltration: the tungsten skeleton and the copper block from step S2 are placed in an alumina ceramic crucible, with the volume ratio of the copper block to the pores of the tungsten skeleton being 1.5. The crucible is heated to 1550°C at a rate of 10°C / min under a hydrogen atmosphere, kept at this temperature for 1.5 hours, and then cooled to room temperature to obtain a copper-infiltrated tungsten-copper alloy.

[0102] Step S4: machining: machining the tungsten-copper alloy obtained in step S3 by wire cutting and centerless cylindrical grinding to obtain a tungsten-copper alloy product meeting the target size;

[0103] Step S5: Chemical copper removal: Immerse the tungsten-copper alloy product in a nitric acid solution (HNO3 concentration of 48 wt.%), and continuously change the solution until the solution is no longer blue.

[0104] Comparative Example 2

[0105] The difference between Comparative Example 2 and Example 1 is that copper is used instead of manganese to carry out steps S3 to S5 respectively;

[0106] The specific operations are as follows:

[0107] Step S3: high-temperature copper infiltration: the tungsten skeleton and the copper block from step S2 are placed in an alumina ceramic crucible, with the volume ratio of the copper block to the pores of the tungsten skeleton being 1.5. The crucible is heated to 1550°C at a rate of 10°C / min under a hydrogen atmosphere, held at that temperature for 1.5 hours, and then cooled to room temperature to obtain a tungsten-copper alloy.

[0108] Step S4: machining: machining the tungsten-copper alloy obtained in step S3 by wire cutting and centerless cylindrical grinding to obtain a tungsten-copper alloy product meeting the target size;

[0109] Step S5: vacuum decoppering: placing the tungsten-copper alloy product of step S4 in an alumina ceramic crucible of a vacuum demetallization furnace, at a vacuum degree of 1 Pa and a temperature of 1550° C. for 3 hours to obtain a porous tungsten product.

[0110] Test Case

[0111] The average porosity and the residual amount of infiltration metal of the porous tungsten parts prepared in the above embodiments and comparative examples were detected.

[0112] 1. Average porosity

[0113] The porosity of three different parts of the sample was measured and the average porosity was calculated. The porosity of a single sample = (1-sample density / theoretical density) × 100%. The theoretical density is tungsten density 19.35 g / cm 3 The sample density refers to GB / T 5163-2006 "Sintered metal materials (excluding cemented carbide) - Determination of density, oil content and porosity of permeable sintered metal materials".

[0114] 2. Residual amount of infiltration metal

[0115] The test method for the residual amount of infiltration metal refers to GB / T 19502-2023 "General Rules for Surface Chemical Analysis - Glow Discharge Optical Emission Spectroscopy".

[0116] 3. Deformation of the outer dimension deformation line

[0117] At room temperature, take a 5mm length sample as the test sample, measure the length change rate of the metal-infiltrated sample and its length after metal removal, and refer to GB / T 1958-2017 "Geometrical Technical Specification for Products (GPS) - Geometric Tolerance Testing and Verification" and take the absolute value.

[0118] 4. Closed-cell rate

[0119] Measure the closed porosity of the finished product. The closed porosity of a single sample = (1-true density of the sample / theoretical density) × 100%. The theoretical density is tungsten density 19.35 g / cm 3 The true density of the sample refers to GB / T 40401-2021 Measurement of skeletal density - Gas volume displacement method.

[0120] The test results are shown in Table 1.

[0121] Table 1

[0122]

[0123] The test data in Table 1 show that the residual amount of infiltrated manganese in the porous tungsten parts prepared in Examples 1 to 7 is less than 0.01wt.%; the linear deformation amount on the outer shape is less than 0.1%; the porosity, pore size and closed porosity are basically unchanged, and the porosity is still between 10% and 30%; this shows that the high-temperature infiltration and vacuum removal of infiltrated metal manganese in the present application have little effect on the microstructure and composition of the tungsten matrix, and the residual amount of infiltrated metal is less than 0.01wt.%, which further improves the emission performance of the porous tungsten on the tungsten-based diffusion cathode device; after vacuum removal of infiltrated metal manganese, the outer dimensions of the porous tungsten parts are little affected, which can improve the assembly accuracy of the tungsten-based diffusion cathode; preparing porous tungsten parts by infiltrating manganese facilitates the machining of porous tungsten, which is beneficial to the dimensional accuracy of high-performance tungsten-based diffusion cathodes.

[0124] Combine Figure 1 and Figure 3 It is shown that the porosity of the tungsten skeleton before infiltration in Example 1 is similar to the porosity of the porous tungsten skeleton material after manganese removal, and there is almost no infiltration metal residue. As can be seen from Table 1, after the porous tungsten is infiltrated and de-coppered in Comparative Examples 1 and 2, the copper residue is too high, which affects the porosity of the porous tungsten. For example, the chemical de-coppering in Comparative Example 1 causes the porous tungsten matrix to be corroded, thereby affecting its pore structure, and the copper residue is relatively high, reaching 1.53wt.%. In addition, since the boiling point of copper is higher than that of metallic manganese, the temperature required for de-coppering is higher than that of metallic manganese; for example, the infiltration metal residue in Comparative Example 2 is as high as 12.8wt.%, which is much higher than the infiltration metal residue of less than 0.01wt.% in the embodiment of the present application; this shows that under the same conditions of vacuum, high temperature and processing time, compared with manganese, the copper removal efficiency is too low, and copper cannot be effectively removed in a short time.

[0125] It should be noted that the terms "first," "second," and the like in the specification and claims of this application are used to distinguish similar objects, and are not necessarily used to describe a specific order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, so that the embodiments of the application described herein can, for example, be implemented in an order other than that described herein.

[0126] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A method for preparing a porous tungsten component, characterized in that: The method comprises the following steps: Step S1: Compressing tungsten powder to obtain a powder compact; Step S2: sintering the powder compact to obtain a tungsten skeleton; Step S3: performing a manganese infiltration treatment on the tungsten skeleton to obtain a manganese infiltrated tungsten-manganese alloy; Step S4: machining the manganese-infiltrated tungsten-manganese alloy to obtain a target tungsten-manganese alloy product; Step S5: The target tungsten-manganese alloy product is kept at a vacuum degree of 0.01-10 Pa and a temperature of 1350-1550° C. for 2-4 hours to perform a manganese removal treatment to obtain the porous tungsten product.

2. The method for preparing a porous tungsten component according to claim 1, wherein: In step S5, the conditions for the manganese removal treatment include: a vacuum degree of 0.1 to 1 Pa, a manganese removal temperature of 1400 to 1550° C., and a manganese removal holding time of 2 to 4 hours; and / or, compared with the outer dimensions of the tungsten skeleton, the linear deformation of the porous tungsten component is less than 0.1%; And / or, the porosity of the porous tungsten component is 10-30%, preferably 15-30%; And / or, the average pore size of the porous tungsten component is 1.2 to 2 μm; preferably 1.5 to 1.7 μm; And / or, the residual content of infiltrated manganese in the porous tungsten article is less than 0.01 wt.%, preferably less than 0.008 wt.%; And / or, the equipment for manganese removal treatment is a vacuum demetallization furnace.

3. The method for preparing a porous tungsten component according to claim 1 or 2, characterized in that: In the step S3, the process of the manganese infiltration treatment includes: keeping the tungsten skeleton and the manganese material in a first non-oxidizing atmosphere at a temperature of 1400-1600° C. for 0.5-2 hours to obtain the manganese infiltrated tungsten-manganese alloy.

4. The method for preparing a porous tungsten component according to claim 3, wherein: The temperature of the manganese infiltration treatment is 1500-1600° C., and the holding time of the manganese infiltration treatment is 0.5-2.0 h; And / or, the heating rate in the manganese infiltration treatment is 5 to 15°C / min; And / or, the first non-oxidizing atmosphere is a hydrogen atmosphere; and / or, the volume ratio of the tungsten skeleton to the manganese material is 1:(1.1-2); And / or, the manganese material is a manganese ingot; And / or, the equipment for the manganese infiltration treatment is an infiltration furnace.

5. The method for preparing a porous tungsten component according to any one of claims 1 to 4, characterized in that: In the step S1, the pressing process includes: maintaining the tungsten powder under a pressing force of 200 to 250 MPa for 90 to 180 seconds to obtain the powder compact; And / or, in step S2, the sintering process includes: keeping the powder compact in a second non-oxidizing atmosphere at a temperature of 1800 to 2150° C. for 3 to 8 hours to obtain the tungsten skeleton; And / or, in step S4, the machining includes at least one of wire cutting, centerless cylindrical grinding and turning.

6. The method for preparing a porous tungsten component according to claim 5, wherein: In step S1, the pressing force is 200-220 MPa, and the holding time is 150-180 s; And / or, the pressing equipment is a cold isostatic press; and / or, the tungsten powder has a Fisher particle size of 6 to 10 μm; And / or, in step S2, the sintering temperature is 1850-1950° C., and the sintering holding time is 6-8 hours; And / or, the second non-oxidizing atmosphere is a hydrogen atmosphere; And / or, the sintering equipment is a medium frequency induction furnace; And / or, the porosity of the tungsten skeleton is 10-30%, preferably 15-30%.

7. A porous tungsten component, characterized in that: The porous tungsten component is prepared by the preparation method according to any one of claims 1 to 6.

8. The porous tungsten article according to claim 7, characterized in that: The porosity of the porous tungsten component is 10-30%, preferably 15-30%. And / or, the average pore size of the porous tungsten component is 1.2 to 2 μm; preferably 1.5 to 1.7 μm; And / or, the residual content of infiltrated manganese in the porous tungsten component is less than 0.01 wt.%, preferably less than 0.008 wt.%.

9. A tungsten-based diffusion cathode comprising a porous tungsten member and an active material, wherein the active material is loaded in the pores of the porous tungsten skeleton; characterized in that: The porous tungsten component is the porous tungsten component prepared by the preparation method according to any one of claims 1 to 6 or the porous tungsten component according to claim 7 or 8.

10. An electronic device comprising a tungsten-based diffused cathode; characterized in that: The tungsten-based diffusion cathode is the tungsten-based diffusion cathode according to claim 9.

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