High efficient preparation method of oxide cathode with exhaust activation synchronous sintering

Abstract

The application discloses a kind of high-efficiency preparation methods for oxide cathode by exhaust activation synchronous sintering, comprising the following steps: S1.metal matrix powder and emitting material are mixed and ball milled, so that the emitting material is uniformly adhered to the surface of the metal matrix powder;S2.the mixed powder after ball milling is screened;S3.the metal matrix powder with emitting material adhered on the surface obtained by screening is placed in a pressing mold, a predetermined pressure is applied for pressing, and an emitter compact is obtained;S4.the emitter compact is assembled into a cathode cylinder and fixed, and a hot wire component is assembled, to obtain a pre-assembled cathode;S5.the pre-assembled cathode is placed in a vacuum environment, and the hot wire component is powered to heat for exhaust treatment and activation treatment, and simultaneously sinter the emitter compact into a metal sponge emitter with uniformly dispersed emitting material inside.The application greatly shortens the cathode preparation period, the emitting material is uniformly distributed, the matrix is firmly combined, and the production efficiency and product reliability are significantly improved.

Description

Technical Field

[0001] This invention relates to the field of vacuum electronic device technology, and in particular to a method for the efficient preparation of oxide cathodes by utilizing exhaust gas to activate synchronous sintering. Background Technology

[0002] Oxide cathodes are core electron emission components in various vacuum electronic devices such as electron guns, microwave tubes, traveling wave tubes, klystrons, and magnetrons. Their electron emission performance, structural stability, and service life directly determine the overall performance and reliability of vacuum electronic devices. With the widespread application of vacuum electronic devices in fields such as communication, radar, medical, and industrial heating, increasingly higher requirements are being placed on the fabrication efficiency and performance of nickel sponge oxide cathodes.

[0003] In existing technologies, the typical fabrication process of nickel sponge oxide cathodes mainly includes the following three stages: The first stage is the preparation of the nickel sponge matrix: nickel powder is formed in the designated position of the cathode cylinder by spraying nickel powder onto the metal surface or filling nickel powder with a special mold, and then high-temperature sintering is carried out to form a bond between the nickel powder particles to obtain a nickel sponge matrix with certain mechanical strength and interconnected pore structure. The second stage is the introduction of the emission material: the emission material is mixed with organic binder and organic solvent to form an emission slurry, and the emission slurry is filled into the pores of the nickel sponge matrix by means of brush coating, spraying or dipping. The third stage is cathode post-processing: In a vacuum environment, thermal decomposition and venting and activation processes are carried out sequentially to transform the emission material into an active layer with electron emission capability, ultimately obtaining a working oxide cathode.

[0004] The aforementioned existing technologies have at least the following prominent problems in actual production and application: First, the preparation process is cumbersome, the production cycle is long, and the production cost is high. The process includes nickel powder forming, sintering, emission paste preparation, emission paste coating, baking, degassing, activation, etc., which involve many and complex steps and a long production time. At the same time, the high-temperature sintering equipment has high energy consumption and high maintenance costs, and the emission paste preparation and coating processes require high skill levels from operators, resulting in a high overall production cost for the cathode.

[0005] Secondly, uneven and insufficient filling of the emission material severely affects the cathode's service life. Due to the complex three-dimensional interconnected pore structure of the nickel sponge matrix, it is difficult to ensure that the emission material can penetrate evenly and fully into all pores using a slurry filling method. This easily leads to surface emission material accumulation and insufficient filling of deep pores. During long-term operation of the cathode, the insufficiently filled areas will prematurely deplete the emission material, resulting in a decrease in cathode emission current density, uneven emission, and ultimately shortening the cathode's service life.

[0006] Secondly, the nickel sponge matrix has low bonding strength and is prone to powder shedding failure. Nickel sponge matrices prepared by spraying or mold vibration filling methods have low metallurgical bonding and poor overall structural strength. Under the thermal cycling effects during subsequent assembly, transportation, and cathode operation, nickel powder particles are prone to detachment. The detached nickel powder can contaminate the internal vacuum environment of vacuum electronic devices and even cause short circuits between electrodes, resulting in permanent device failure.

[0007] Finally, the venting process is time-consuming and has low production efficiency. The emission paste contains a large amount of organic binders and solvents. During the cathode venting process, a long period of heat preservation is required to completely decompose these organic components and remove them from the cavity. This not only further prolongs the cathode manufacturing cycle but also increases energy consumption and equipment occupancy time, which is not conducive to large-scale industrial production.

[0008] Therefore, it is necessary to improve existing technologies to overcome their shortcomings. Summary of the Invention

[0009] The purpose of this invention is to solve the above-mentioned problems in the prior art and provide an efficient method for preparing oxide cathodes by exhaust activation and synchronous sintering, so as to overcome the defects of existing oxide cathodes, such as complex manufacturing process, long manufacturing time, high cost, uneven filling of emission material and low bonding strength of nickel sponge matrix.

[0010] The technical solution adopted by this invention to solve its technical problem is: a method for efficiently preparing oxide cathodes by utilizing exhaust gas activation and simultaneous sintering, comprising the following steps: S1. Mix and ball-mill the metal matrix powder and the emissive material to make the emissive material uniformly adhere to the surface of the metal matrix powder; S2. The ball-milled mixed powder is sieved to remove excess free emissive material and obtain a metal matrix powder with emissive material adhering to its surface. S3. Place the metal matrix powder with the emission material adhering to its surface into a pressing mold, apply a preset pressure to press it together, and obtain an emitter compact; S4. Assemble the emitter blank into the cathode cylinder and fix it, then assemble the hot wire component to obtain the pre-assembled cathode; S5. The pre-assembled cathode is placed in a vacuum environment, and the hot wire component is energized to heat it in sequence to perform exhaust treatment and activation treatment. During the controlled heating process of exhaust treatment and activation treatment, atomic migration and diffusion occur between the metal matrix powders and solid-state sintering is formed, thereby sintering the emitter compact into a metal sponge emitter with the emitter material uniformly dispersed inside. At the same time, the emitter material completes thermal decomposition and activation during the controlled heating process, and finally an oxide cathode that can emit electrons is obtained.

[0011] As a further improvement of the present invention, in step S1, the metal matrix powder is nickel powder, nickel-cobalt alloy or nickel-magnesium alloy, and its particle size is between 20μm and 30μm.

[0012] As a further improvement of the present invention, in step S1, the emission material is a ternary carbonate powder, which includes calcium carbonate, barium carbonate and strontium carbonate.

[0013] As a further improvement of the present invention, in step S1, the weight ratio of the metal matrix powder to the emission material is (8-12):1.

[0014] As a further improvement of the present invention, in step S1, the metal matrix powder and the emission material are mixed and ball-milled using a ball mill, the ball mill speed is 200 r / min to 280 r / min, and the ball milling time is 36 h to 60 h.

[0015] As a further improvement of the present invention, in step S3, the preset pressure applied to the metal matrix powder with the emission material adhering to the surface is 40MPa~200MPa.

[0016] As a further improvement of the present invention, step S4 specifically includes: S41. Place the emitter blank into the cathode cylinder and make the emitter blank abut against the limiting stop at one end of the cathode cylinder; S42. Place a fixing plate inside the cathode cylinder, press the emitter blank with the fixing plate, and weld the fixing plate to the inner wall of the cathode cylinder; S43. The hot wire component is assembled into the inside of the cathode cylinder and fixed, with the hot wire component located on the side of the fixing plate opposite to the emitter blank, to obtain a pre-assembled cathode.

[0017] As a further improvement of the present invention, in step S5, the exhaust process is carried out in a vacuum environment with continuous evacuation throughout the process; when the vacuum level of the vacuum environment reaches the first preset vacuum level, the hot wire component is energized and the current is gradually increased; during the heating process, when the vacuum level drops to the second preset vacuum level, the current increase is stopped and the current value is maintained, while the continuous evacuation state is maintained; when the vacuum level rises back to the third preset vacuum level, the current is increased again, and so on in a cyclical control; wherein, the highest temperature in the exhaust stage does not exceed 1100°C.

[0018] As a further improvement of the present invention, in step S5, the exhaust process is determined by detecting the vacuum level of the vacuum environment; when the vacuum level of the vacuum environment reaches the fourth preset vacuum level, and the vacuum level no longer decreases as the current of the hot wire component increases and the temperature rises, it is determined that the thermal decomposition exhaust of the emission material is completed.

[0019] As a further improvement of the present invention, in step S5, the activation process is carried out after the thermal decomposition and exhaust of the emission material is completed; by increasing the current supplied to the hot wire component, the temperature is raised to 1100℃-1200℃, and the temperature is kept for a set time to complete the activation of the emission material.

[0020] The beneficial effects of this invention are: 1. This invention provides an efficient method for preparing oxide cathodes using exhaust gas activation and simultaneous sintering. By simultaneously performing decomposition, exhaust gas removal, activation, and sintering of the oxide cathode, the method eliminates multiple independent processes in the prior art, such as low-temperature and high-temperature sintering of the nickel sponge substrate, as well as the preparation, coating, and baking of the emission paste. This greatly simplifies the oxide cathode manufacturing process, significantly reduces the manufacturing time and cost, and improves production efficiency.

[0021] 2. The emission material is uniformly distributed on the surface of the metal matrix powder during the ball milling stage. After pressing, the emission material is uniformly dispersed inside the emitter compact, which completely avoids the defects of insufficient filling and uneven distribution in the traditional slurry filling method. This ensures the uniformity of electron emission across the entire emission surface of the cathode and effectively extends the service life of the cathode.

[0022] 3. The metal matrix powder is first pressed into an emitter compact with a certain mechanical strength, and then solid-state sintering is formed in a vacuum environment through atomic migration and diffusion. The resulting metal sponge matrix has a bonding strength that is much higher than that of nickel sponge matrix prepared by traditional spraying or vibration filling methods, which fundamentally solves the problem of nickel powder shedding and improves the structural stability and reliability of the cathode.

[0023] 4. Since this invention directly uses powdered emission material, there is no need to add organic binders and solvents. The long-term heat preservation required for the decomposition of organic components is omitted during the exhaust process, which further shortens the exhaust time and reduces energy consumption. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a flowchart illustrating the steps of the efficient preparation method of oxide cathodes using exhaust-activated synchronous sintering according to the present invention. Figure 2 This is a flowchart illustrating the specific steps of step S4 in the efficient preparation method of oxide cathodes using exhaust gas activation and synchronous sintering of the present invention. Figure 3 This is a cross-sectional view of the oxide cathode prepared according to the present invention.

[0026] Referring to the accompanying drawings, the following explanations are provided: 1. Cathode cylinder; 101. Limiting baffle; 2. Hot wire component; 3. Metal sponge emitter; 4. Fixing plate. Detailed Implementation

[0027] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0028] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this application, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0029] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. The illustrations only show the components related to this application and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the shape, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0030] Additionally, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that practice can be carried out without these specific details.

[0031] The technical solutions provided by the various embodiments of this application are described below with reference to the accompanying drawings.

[0032] See Figures 1 to 3 This invention provides a highly efficient method for preparing oxide cathodes using exhaust gas activation and simultaneous sintering, comprising the following steps: S1. Mix the metal matrix powder and the emission material and ball mill them to make the emission material uniformly adhere to the surface of the metal matrix powder; S2. The ball-milled mixed powder is sieved to remove excess free emissive material and obtain a metal matrix powder with emissive material adhering to its surface. S3. Place the metal matrix powder with the emission material adhering to its surface into a pressing mold, apply a preset pressure to press it together, and obtain the emitter compact; S4. Assemble the emitter blank into the cathode cylinder 1 and fix it. Then, insert the hot wire component 2 into the cathode cylinder 1 to obtain the pre-assembled cathode. S5. The pre-assembled cathode is placed in a vacuum environment and heated by the hot wire component 2 to perform exhaust treatment and activation treatment in sequence. During the controlled heating process of exhaust treatment and activation treatment, atomic migration and diffusion occur between the metal matrix powders and solid-phase sintering is formed, thereby sintering the emitter compact into a metal sponge emitter 3 with the emitter material uniformly dispersed inside. At the same time, the emitter material completes thermal decomposition and activation during the controlled heating process, and finally obtains an oxide cathode that can emit electrons.

[0033] This invention pre-mixes and ball-mills the metal matrix powder and the emission material, allowing the emission material to adhere uniformly to the surface of the metal matrix powder. After pressing and forming, the powder is directly assembled. The sintering of the metal sponge emitter 3 is completed simultaneously using the high temperature of the cathode's own venting and activation process. This completely breaks the technical bias of the prior art, which requires the separate preparation of the metal sponge matrix before filling with the emission material. It fundamentally solves the problems of complex manufacturing process, long manufacturing time, high cost, uneven filling of emission material, and low bonding strength of nickel sponge matrix in the existing oxide cathode manufacturing process.

[0034] This invention simplifies the oxide cathode manufacturing process by simultaneously performing decomposition, degassing, activation, and sintering of the oxide cathode. This eliminates the multiple independent processes involved in existing technologies, such as low-temperature and high-temperature sintering of the nickel sponge matrix, and the preparation, coating, and baking of the emission slurry. This significantly reduces the manufacturing time and cost, improving production efficiency. Furthermore, the emission material is uniformly distributed on the surface of the metal matrix powder during the ball milling stage. The uniform dispersion of emission material within the compacted emitter blank after pressing completely avoids the defects of insufficient filling and uneven distribution inherent in traditional slurry filling methods. This ensures the uniformity of electron emission across the entire emission surface of the cathode, effectively extending its service life. In addition, the metal matrix powder is first pressed to obtain an emitter blank with a certain mechanical strength, and then solid-state sintering is achieved in a vacuum environment through atomic migration and diffusion. The resulting metal sponge matrix has a bonding strength far exceeding that of nickel sponge matrices prepared by traditional spraying or vibratory filling methods, fundamentally solving the problem of nickel powder detachment and improving the structural stability and reliability of the cathode. Moreover, since the present invention directly uses powdered emission material, there is no need to add organic binders and solvents. The long-term heat preservation required for the decomposition of organic components is omitted during the exhaust process, which further shortens the exhaust time and reduces energy consumption.

[0035] In this embodiment, the metal matrix powder used in step S1 is nickel powder, which is obtained after being purified, ground and sieved in a hydrogen furnace, and its particle size is between 20μm and 30μm.

[0036] Nickel powder, widely recognized as the optimal matrix material in the field of oxide cathodes, not only possesses moderate reducing power—capable of reacting with barium oxide produced by the decomposition of the emitter material at the cathode activation temperature to generate free barium atoms that diffuse to the surface of the metal sponge, forming a low-work function electron emission layer—but also exhibits a sintering temperature range that perfectly matches the temperature range of the cathode degassing and activation processes of this invention, achieving sufficient solid-state sintering without the need for additional process temperature increases. Furthermore, nickel exhibits excellent chemical stability and a low evaporation rate under high-temperature vacuum conditions, preventing harmful reactions with the emitter material and avoiding contamination of the internal environment of vacuum electronic devices through evaporation, effectively extending the cathode's lifespan. In addition, nickel possesses excellent electrical and thermal conductivity, enabling the uniform transfer of current and heat to all parts of the emitter, ensuring uniform temperature on the emitting surface and preventing premature depletion of the emitter material due to localized overheating. Based on this, the particle size of nickel powder is further controlled between 20μm and 30μm. Nickel powder in this particle size range has both good pressing and molding performance and sintering activity. Under appropriate pressing pressure, it can form a uniformly structured emitter compact. At the same time, during the degassing and activation process, sufficient atomic migration and diffusion can occur to form a firmly bonded metal sponge matrix, which further ensures the structural stability and electron emission performance of the oxide cathode.

[0037] In addition, in other embodiments of the present invention, the metal matrix powder may also be selected from nickel-cobalt alloys or nickel-magnesium alloys, etc. It should be noted that, regardless of which matrix material is used, as long as the core technical solution of the present invention is adopted—mixing and ball-milling the metal matrix powder with the emission material powder, pressing and then directly assembling them, and simultaneously completing the sintering using the cathode exhaust activation process—it falls within the protection scope of the present invention.

[0038] In this embodiment, the emission material used in step S1 is ternary carbonate powder, which includes calcium carbonate, barium carbonate and strontium carbonate. These three carbonates are also recognized as the best emission material combination in the field of oxide cathodes. The composite oxide formed by decomposition at high temperature has low electron work function and good electron emission performance. By adjusting the ratio of the three carbonates, the working temperature and emission current density of the cathode can be flexibly adjusted to meet the needs of different vacuum electronic devices.

[0039] In step S1, the weight ratio of the metal matrix powder to the emission material is (8-12):1, preferably 10:1. This ratio is the optimal ratio verified by a large number of experiments, which can ensure that during the mixing and ball milling process, the emission material powder is fully and uniformly adhered to the surface of all the metal matrix powder under the action of electrostatic adsorption and friction, forming a complete coating layer with a suitable thickness.

[0040] In step S1, the metal matrix powder and the emissive material are mixed and ball-milled using a ball mill at a speed of 200 r / min to 280 r / min for 36 h to 60 h. These process parameters ensure that the emissive material powder adheres uniformly and firmly to the surface of the metal matrix powder under mechanical force. This prevents uneven adhesion due to excessively low speed or short ball milling time, and avoids excessive deformation of the metal matrix powder or overly fine particle size of the emissive material due to excessively high speed or long ball milling time, thus ensuring the smooth progress of subsequent pressing and sintering processes.

[0041] Preferably, in this embodiment, the ball mill rotation speed is 240 r / min and the ball milling time is 48 h.

[0042] In this embodiment, step S2 uses a 320-mesh sieve to sieve the ball-milled mixed powder to remove excess emission material.

[0043] In step S3, the preset pressure applied to the metal matrix powder with the emitting material adhering to its surface is 40MPa~200MPa. This preset pressure is related to the particle size of the metal matrix powder; that is, the larger the particle size of the metal matrix powder, the greater the required pressure. Preferably, the preset pressure in this embodiment is 50MPa. The outer diameter of the emitter blank formed by the pressing die is adapted to the inner cavity size of the cathode cylinder 1 so that the emitter blank can be smoothly assembled into the inner cavity of the cathode cylinder 1.

[0044] The compaction process of metal matrix powder can be divided into the following two stages: The first stage is the rearrangement and filling of nickel powder particles: When the pressing mold begins to apply pressure, the originally loosely packed and disordered nickel powder particles will move and rearrange under the pressure. The contact area between the particles increases significantly, the particles that were originally connected to each other collapse, the overall volume shrinks significantly, and the porosity decreases. This stage mainly occurs in the early stage when the pressure is low. The density of the emitter compact increases rapidly with the increase of pressure.

[0045] The second stage is the plastic deformation of nickel powder particles: When the pressure continues to rise to a certain level (50 MPa in this invention), exceeding the yield strength of the nickel powder particles, the nickel powder particles will undergo plastic deformation. The originally spherical nickel powder particles are flattened and elongated, and the contact between particles changes from point contact to surface contact. The dislocation density inside the nickel powder particles increases, and the surface energy increases significantly, providing a driving force for subsequent atomic diffusion and sintering.

[0046] Through the combined action of the two stages described above, the originally loose nickel powder is pressed into a nickel sponge blank with a specific shape, a certain mechanical strength, and an interconnected pore structure. This nickel sponge blank is strong enough to support subsequent assembly, transportation, and welding operations without cracking or shedding powder.

[0047] More importantly, plastic deformation significantly increases the surface energy of nickel powder particles, reducing the activation energy required for sintering, enabling nickel powder to complete full sintering and bonding within the temperature range of cathode exhaust activation (600-1200℃).

[0048] See Figure 2 and Figure 3 Step S4 specifically includes the following steps: S41. The cathode cylinder 1 is cylindrical in shape, and its upper end extends inward to form an annular limiting baffle 101. The emitter blank is placed into the inner cavity of the cathode cylinder 1 from the lower end of the cathode cylinder 1 and abuts against the limiting baffle 101 at the upper end of the cathode cylinder 1. S42. Place the fixing plate 4 inside the cathode cylinder 1, press the emitter blank with the fixing plate 4, and weld the fixing plate 4 to the inner wall of the cathode cylinder 1 by spot welding or laser welding. S43. Assemble the hot wire component 2 into the cathode cylinder 1 and fix it on the side of the fixing plate 4 facing away from the emitter blank to obtain a pre-assembled cathode.

[0049] The present invention uses a limiting baffle 101 at one end of the cathode cylinder 1 to precisely position the emitter blank, and then uses a fixing plate 4 to press and weld the emitter blank, which can ensure that the emitter blank is accurately positioned and firmly fixed in the cathode cylinder 1, and will not shift or fall off during subsequent sintering and operation. The hot wire component 2 is assembled on the side of the fixing plate 4 that is away from the emitter blank, which can ensure that the heat generated by the hot wire is evenly transferred to the entire emitter, thus improving the working reliability of the cathode.

[0050] In this embodiment, both the cathode cylinder 1 and the fixing plate 4 can be made of nickel or molybdenum.

[0051] In step S5 of this invention, the pre-assembled cathode is installed onto the fixture of a dedicated vacuum exhaust station, ensuring good contact between the hot wire component 2 and the power supply electrode of the exhaust station. The vacuum exhaust system is started to continuously evacuate the exhaust station cavity. Throughout the entire exhaust and activation process, the vacuum system must remain in continuous operation and the vacuuming process must not be interrupted.

[0052] When the vacuum level reaches the first preset vacuum level of 1.0 × 10⁻⁶ -5 When Pa, it indicates that the air in the cavity has been basically eliminated. At this time, the power system of the exhaust station starts to supply current to the hot wire component 2 and gradually increases the current so that the heat generated by the hot wire component 2 is evenly transferred to the emitter compact through thermal radiation and thermal conduction.

[0053] In the initial stage of heating (temperature below 600℃), the emitter compact mainly releases the adsorbed gas and a small amount of residual surface impurities. The amount of gas generated is much less than the pumping rate of the vacuum system, and the vacuum level can be maintained at a high level. During this stage, the current can be increased steadily according to the set rate.

[0054] When the temperature rises above 600℃, the emission material begins to undergo significant thermal decomposition, releasing a large amount of gas. At this point, the amount of gas generated exceeds the pumping rate of the vacuum system, causing the vacuum level inside the cavity to drop rapidly. When the vacuum level drops to the second preset vacuum level of 5.0 × 10⁻⁶, the vacuum level will decrease. -4 When the current reaches Pa, immediately stop increasing the current of the hot wire component 2, maintain the current value unchanged, and simultaneously keep the vacuum system continuously evacuated. During this isothermal maintenance phase, the generated gas is continuously discharged, and the vacuum level inside the chamber will gradually recover.

[0055] When the vacuum level rises back to the third preset vacuum level of 1.0 × 10⁻⁶ -5When Pa, the current to the hot wire component 2 is increased further, and the temperature continues to rise. This cycle of "heating up - vacuum decreasing - temperature maintaining - vacuum recovering - heating up again" is repeated. Throughout the entire exhaust phase, the maximum temperature is controlled below 1100℃.

[0056] Whether the exhaust process is complete is objectively determined by real-time monitoring of the vacuum level inside the chamber. The process is completed when the vacuum level inside the chamber reaches the fourth preset vacuum level of 1.0 × 10⁻⁶. -6 When the vacuum level no longer shows a decreasing trend when the hot wire current and emitter temperature are increased, but instead remains stable or is further increased, it indicates that the thermal decomposition reaction of the emitter material has been completed and all the gases produced by the decomposition have been discharged from the cavity. At this point, the exhaust process is considered complete.

[0057] During the aforementioned exhaust heating process, due to the plastic deformation caused by the early compression of the nickel sponge blank, the nickel powder has a high surface energy. During the decomposition and exhaust of the emission material, atomic migration and diffusion begin simultaneously between the nickel powder particles, gradually forming a solid-phase sintered bond.

[0058] After the exhaust process is completed, the activation process begins immediately. The current supplied to the hot wire component 2 is increased to raise the emitter temperature to a set temperature between 1100℃ and 1200℃, and the temperature is maintained at this set temperature for a set duration.

[0059] The heat preservation time can be adjusted according to the size and specifications of the oxide cathode, and this application does not impose any restrictions on it.

[0060] During the activation and heat preservation stage, atomic diffusion between the metal matrix powders is further intensified, forming a stronger metallurgical bond, enabling the metal sponge emitter 3 to achieve its final structural strength. At the same time, the metal matrix undergoes a reduction reaction with the barium oxide produced by the decomposition of the emission material, generating free barium atoms that diffuse to the surface of the metal sponge, forming an electron emission layer with low work function. This enables the cathode to obtain stable electron emission capability, completing the activation of the emission material and ultimately yielding an oxide cathode.

[0061] The same or similar parts between the various embodiments in this specification can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments.

[0062] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A highly efficient method for preparing oxide cathodes using exhaust gas activation and simultaneous sintering, characterized in that, Includes the following steps: S1. Mix and ball-mill the metal matrix powder and the emissive material to make the emissive material uniformly adhere to the surface of the metal matrix powder; S2. The ball-milled mixed powder is sieved to remove excess free emissive material and obtain a metal matrix powder with emissive material adhering to its surface. S3. Place the metal matrix powder with the emission material adhering to its surface into a pressing mold, apply a preset pressure to press it together, and obtain an emitter compact; S4. The emitter blank is assembled into the cathode cylinder (1) and fixed, and then the hot wire component (2) is assembled to obtain the pre-assembled cathode; S5. The pre-assembled cathode is placed in a vacuum environment and heated by the hot wire component (2) in sequence to perform exhaust treatment and activation treatment. During the controlled heating process of exhaust treatment and activation treatment, atomic migration and diffusion occur between the metal matrix powders and solid-phase sintering is formed, thereby sintering the emitter compact into a metal sponge emitter (3) with the emitter material uniformly dispersed inside. At the same time, the emitter material completes thermal decomposition and activation during the controlled heating process, and finally obtains an oxide cathode that can emit electrons.

2. The method for efficient preparation of oxide cathodes using exhaust gas activation and simultaneous sintering according to claim 1, characterized in that, In step S1, the metal matrix powder is nickel powder, nickel-cobalt alloy or nickel-magnesium alloy, and its particle size is between 20μm and 30μm.

3. The method for efficient preparation of oxide cathodes using exhaust gas activation and simultaneous sintering according to claim 1, characterized in that, In step S1, the emission material is a ternary carbonate powder, which includes calcium carbonate, barium carbonate, and strontium carbonate.

4. The method for efficient preparation of oxide cathodes using exhaust gas activation and simultaneous sintering according to claim 1, characterized in that, In step S1, the weight ratio of the metal matrix powder to the emission material is (8-12):

1.

5. The method for efficient preparation of oxide cathodes using exhaust gas activation and simultaneous sintering according to claim 1, characterized in that, In step S1, the metal matrix powder and the emission material are mixed and ball-milled using a ball mill. The ball mill speed is 200 r / min to 280 r / min, and the ball milling time is 36 h to 60 h.

6. The method for efficient preparation of oxide cathodes using exhaust gas activation and simultaneous sintering according to claim 1, characterized in that, In step S3, the preset pressure applied to the metal matrix powder with the emission material adhering to its surface is 40MPa~200MPa.

7. The method for efficient preparation of oxide cathodes using exhaust gas activation and simultaneous sintering according to claim 1, characterized in that, Step S4 specifically includes: S41. Place the emitter blank into the cathode cylinder (1) and make the emitter blank abut against the limiting stop (101) at one end of the cathode cylinder (1); S42. Place a fixing plate (4) inside the cathode cylinder (1), press the emitter blank with the fixing plate (4), and weld the fixing plate (4) to the inner wall of the cathode cylinder (1); S43. The hot wire component (2) is assembled into the cathode cylinder (1) and fixed. The hot wire component (2) is located on the side of the fixing plate (4) facing away from the emitter blank, thus obtaining a pre-assembled cathode.

8. The method for efficient preparation of oxide cathodes using exhaust gas activation and simultaneous sintering according to claim 1, characterized in that, In step S5, the exhaust process is carried out in a vacuum environment with continuous evacuation throughout the process; when the vacuum level of the vacuum environment reaches the first preset vacuum level, the hot wire component (2) is energized and the current is gradually increased; during the heating process, when the vacuum level drops to the second preset vacuum level, the current is stopped and the current value is maintained, while the continuous evacuation state is maintained; when the vacuum level rises back to the third preset vacuum level, the current is increased again, and so on in a cyclical control; wherein, the highest temperature in the exhaust stage does not exceed 1100℃.

9. The method for efficient preparation of oxide cathodes using exhaust gas activation and simultaneous sintering according to claim 8, characterized in that, In step S5, the exhaust process is determined by detecting the vacuum level of the vacuum environment. When the vacuum level of the vacuum environment reaches the fourth preset vacuum level, and the vacuum level no longer decreases as the current of the hot wire component (2) increases and the temperature rises, the thermal decomposition exhaust of the emission material is determined to be complete.

10. The method for efficient preparation of oxide cathodes using exhaust gas activation and simultaneous sintering according to claim 1, characterized in that, In step S5, the activation process is carried out after the thermal decomposition and exhaust of the emission material is completed; by increasing the current supplied to the hot wire component (2), the temperature is raised to 1100℃-1200℃, and the temperature is kept for a set time to complete the activation of the emission material.

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