A chromium-containing emission active material for a coated diffusion cathode and a preparation method and application thereof

Abstract

The application discloses a kind of film diffusion cathode with chromium-containing emitting active material and its preparation method and application, the chromium-containing emitting active material includes: chromium, barium, calcium, aluminum, carbon, hydrogen and oxygen element, wherein, the molar ratio of chromium, barium, calcium, aluminum is 1-36:18-40:1-15:2-45.The chromium-containing emitting active material developed in the application compared with traditional barium calcium aluminate emitting material, innovatively introduces chromium element, and chromium is used as the carrier of active element barium during the working process of cathode, so that the film diffusion cathode prepared by it is significantly superior to ordinary film diffusion cathode in emission performance.And the preparation process of the chromium-containing emitting active material is simple, and the repeatability is good, with the potential of popularization and application in the field of vacuum electron devices.

Description

Technical Field

[0001] This invention relates to the field of vacuum electronic components technology. More specifically, it relates to a chromium-containing emission-active material for coated diffusion cathodes, its preparation method, and its applications. Background Technology

[0002] Coated diffused cathodes are indispensable core components in vacuum electronic devices, which play a crucial role in information systems. A coated diffused cathode typically consists of a cathode substrate, an emission-active material, and a noble metal film. The cathode substrate is made of a porous metal, such as tungsten. The noble metal film is generally made of one or an alloy of any two of Os, Ir, or Ru. The emission-active material is a major component of the coated diffused cathode and significantly affects its emission performance. The performance of the emission-active material greatly influences the final emission performance of the cathode. Electrons emitted from the cathode form a current under the influence of an electric field. During device operation, this current interacts with a high-frequency field, enabling the device to perform amplification, oscillation, and other functions, ultimately outputting the desired signal. During the operation of the coated diffused cathode, the emission-active material reacts with the substrate. Active components (such as Ba) are generated and migrate to the cathode surface, forming a structure with a low work function with the substrate metal and the noble metal film, thus enabling the cathode to emit a large number of electrons. Therefore, the performance of the emission-active material largely determines the final emission performance of the cathode.

[0003] For coated diffused cathodes, the current demand for high emission current density remains primary in vacuum electronic device applications. Therefore, improving emission performance has always been a focus of research, both in coated diffused cathode research and in emission-active material research. Insufficient emission current will lead to the following problems: ① low gain and bandwidth in vacuum electronic devices, failing to meet device operating requirements; ② poor electron beam quality, making focusing difficult; ③ large cathode size, failing to meet the miniaturization requirements of device design. Therefore, to avoid these problems, it is necessary to further improve the high emission current density of coated diffused cathodes to meet the needs of cathode research and the design and development of vacuum electronic devices. Summary of the Invention

[0004] Based on the above background, the main objective of this invention is to develop a new chromium-containing emission active material in order to improve the emission current density of the coated diffusion cathode, thereby improving the gain, bandwidth and electron beam quality in vacuum electronic devices, and promoting the miniaturization of vacuum electronic devices.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a chromium-containing emissive material for a coated diffusion cathode, wherein the chromium-containing emissive material comprises chromium, barium, calcium, aluminum, carbon, hydrogen and oxygen elements.

[0007] To address the need for increased emission current density in existing coated diffusion cathodes, this invention incorporates chromium (Cr) into a chromium-containing emission-active material, forming a novel chromium-containing emission-active material. Experiments have confirmed that the introduction of chromium allows it to form barium chromate with barium in the emission-active material, serving as a carrier for the active element barium. When the chromium-containing emission-active material is impregnated into the cathode substrate to prepare a coated diffusion cathode, the barium chromate provides elemental Ba during operation. This elemental Ba, along with other components in the chromium-containing emission-active material, diffuses through the substrate pores to the surface of the coated diffusion cathode. This results in a low work function structure on the cathode surface, enabling the emission of a large number of electrons.

[0008] Preferably, the molar ratio of chromium, barium, calcium and aluminum is 1-36:18-40:1-15:2-45.

[0009] In this invention, by doping chromium into the chromium-containing emissive material and combining it with a suitable ratio of chromium, barium, calcium, and aluminum, the emission current density of the coated diffusion cathode can be improved more effectively.

[0010] More preferably, the molar ratio of chromium, barium, calcium and aluminum is 5-15:18-25:5-15:20-25.

[0011] In a second aspect, the present invention provides a method for preparing the above-mentioned chromium-containing emission active material for a coated diffusion cathode, comprising the following steps:

[0012] 1) Weigh out the soluble salts of chromium, barium, calcium, and aluminum according to the proportions, dissolve them in a solvent to prepare a mixed salt solution;

[0013] 2) The mixed salt solution is mixed with ammonium carbonate solution, stirred and reacted to obtain a suspension, which is then filtered to obtain a chromium-containing emission-active material precursor;

[0014] 3) Dry the chromium-containing emission-active material precursor to obtain the final product.

[0015] It is understood that the chromium-containing emission active material obtained by the present invention through chemical reaction is a mixture containing BaCO3, BaCrO4, BaCa(CO3)2, and AlOOH.

[0016] Furthermore, in step 2), the ratio of the mixed salt solution to the ammonium carbonate solution can be determined by continuously increasing the amount of one and observing whether precipitation continues to occur during the stirring reaction; in a specific embodiment of the present invention, the ratio of the mixed salt solution to the ammonium carbonate solution is 1:1-1.5 (v:v).

[0017] More preferably, in the above steps, the soluble salt of chromium is selected from chromium nitrate or chromium chloride; the soluble salt of barium is selected from barium nitrate or barium chloride; the soluble salt of calcium is selected from calcium nitrate or calcium chloride; and the soluble salt of aluminum is selected from aluminum nitrate or aluminum chloride.

[0018] The total concentration of solutes in the mixed salt solution is 0.1-1.0 mol / L. It can be understood that the solutes here refer to soluble salts of chromium, barium, calcium, and aluminum.

[0019] The concentration of the ammonium carbonate solution is 0.1-1.2 mol / L.

[0020] The stirring reaction is carried out at 18-30°C for 5-25 minutes.

[0021] The drying conditions are as follows: the drying temperature is 80-150℃, and the drying time is ≥6h.

[0022] Thirdly, the present invention provides the application of a chromium-containing emission active material for a coated diffusion cathode in the preparation of a coated diffusion cathode.

[0023] Unless otherwise specified, all raw materials used in this invention are commercially available. Any range described in this invention includes end values, any values ​​between end values, and any subranges formed by end values ​​or any values ​​between end values.

[0024] The beneficial effects of this invention are as follows:

[0025] 1) Compared with traditional emission active materials, the chromium-containing emission active material provided by this invention innovatively introduces chromium. Chromium reacts with barium to form barium chromate. During cathode operation, chromium acts as a carrier for the active element barium, which helps in the generation and migration of the active element Ba during the operation of the coated diffusion cathode. This effectively improves the emission performance of the coated diffusion cathode prepared by the chromium-containing emission active material, which is of great significance for solving the problem of insufficient emission current in the current technology. Moreover, the preparation process of the chromium-containing emission active material is compatible with the application process conditions of the coated diffusion cathode and devices containing it. Therefore, the chromium-containing emission active material of this invention has the prospect of further promotion and application.

[0026] 2) The chromium-containing emission active material provided by the present invention, combined with the appropriate ratio of chromium, barium, calcium and aluminum elements, can further improve the emission current density of the coated diffusion cathode. This is beneficial to the improvement of the gain, bandwidth and electron beam quality of vacuum electronic devices, and at the same time helps the miniaturization of vacuum electronic devices.

[0027] 3) The preparation process of the chromium-containing emission active material for the coated diffusion cathode provided by the present invention is simple and the raw materials are readily available, and it has the prospect of large-scale and commercial production. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying 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.

[0029] Figure 1 The image shown is a scanning electron microscope (SEM) image of the chromium-containing emissive material prepared in Example 1 of the present invention;

[0030] Figure 2 The X-ray diffraction (XRD) pattern of the chromium-containing emission-active material prepared in Example 1 of the present invention is shown.

[0031] Figure 3 The emission test curves of the coated diffusion cathode prepared using the chromium-containing emission-active material of Example 1 of the present invention are shown.

[0032] Figure 4 The graph shows a comparison of emission test curves of coated diffusion cathodes prepared using the chromium-containing emission active material of Example 1 of the present invention and the conventional 612 type barium calcium aluminate emission material. Detailed Implementation

[0033] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments and accompanying drawings, further clarifies the invention. It should be understood that the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0034] Unless otherwise specified, all methods used in this invention are conventional, and the raw materials used can be obtained from publicly available commercial sources unless otherwise specified.

[0035] The conventional barium calcium aluminate emitting material used in the following examples is a 612-type formulation, i.e., the molar ratio of barium, calcium, and aluminum is 6:1:2.

[0036] Example 1

[0037] This example discloses a chromium-containing emission-active material for a coated diffusion cathode, and the specific preparation method includes the following steps:

[0038] 1) Weigh and mix Cr(NO3)3·9H2O, Ba(NO3)2, Ca(NO3)2·4H2O and Al(NO3)3·9H2O in a molar ratio of 5:18:13:20. Dissolve the mixed salt in deionized water to prepare a mixed salt solution with a concentration of 0.28 mol / L.

[0039] 2) Dissolve ammonium carbonate in deionized water and stir thoroughly to prepare an ammonium carbonate solution with a concentration of 0.27 mol / L;

[0040] 3) Mix and stir the 400 mL mixed salt solution with 400 mL ammonium carbonate solution to carry out the reaction. The reaction is carried out at room temperature for 5-25 minutes. After the reaction is completed, a suspension is obtained. Filter the suspension to obtain a chromium-containing emission active material precursor.

[0041] 4) Dry the chromium-containing emission active material precursor at 117°C for ≥6 hours to obtain a mixture whose main components are carbonate, chromate and aluminum hydroxide, which is the chromium-containing emission active material.

[0042] Figure 1 The image shows a scanning electron microscope (SEM) image of the chromium-containing emissive material prepared in this example. As can be seen from the image, the chromium-containing emissive material is in the form of irregular particles.

[0043] Figure 2 The image shows the X-ray diffraction (XRD) pattern of the chromium-containing emission-active material prepared in this example. The figure shows that the material composition includes calcium barium carbonate, barium carbonate, barium chromate, and aluminum hydroxide, indicating that the preparation method of this invention effectively achieves Cr doping and generates a chromium-containing compound—barium chromate.

[0044] Performance testing:

[0045] Parallel tests: The chromium-containing emission active material prepared in this embodiment and the traditional 612-type barium calcium aluminate emission material were respectively made into coated diffusion cathodes (the substrates were both porous tungsten, and the surface films were both Os) using the same method. The emission performance of the two groups of coated diffusion cathodes was tested.

[0046] Figure 3 The pulse emission test curve for the coated diffused cathode prepared with chromium-containing emissive material in this example is shown. The test pulse conditions were 200 Hz and 10 μs. The test results show that the emission current density of this cathode can reach 41.94 A / cm² at 1050 °C. 2 A coated diffusion cathode (referred to as a conventional coated cathode) prepared using the same method with conventional 612 type barium calcium aluminate emission material typically exhibits a pulse emission current density of 15-30 A / cm² at 1050℃ under the same test conditions. 2 .

[0047] Figure 4 The figure compares the emission test curves of a conventional coated diffusion cathode and the coated diffusion cathode prepared in this example (referred to as the novel cathode (containing chromium)) at 1050℃. The figure shows that the pulse emission current density of the coated diffusion cathode prepared in this example is 41.94 A / cm². 2The pulse emission current density of a conventional coated diffused cathode is 22.29 A / cm². 2 .

[0048] In summary, the above results all indicate that the chromium-containing emission-active material prepared in this embodiment can enable the coated diffusion cathode to have better emission performance when applied to the preparation of the coated diffusion cathode.

[0049] Example 2

[0050] This example discloses a chromium-containing emission-active material for a coated diffusion cathode, and the specific preparation method includes the following steps:

[0051] 1) Weigh and mix Cr(NO3)3·9H2O, Ba(NO3)2, Ca(NO3)2·4H2O and Al(NO3)3·9H2O in a molar ratio of 11:24:8:22. Dissolve the mixed salt in deionized water to prepare a mixed salt solution with a concentration of 0.45 mol / L.

[0052] 2) Dissolve ammonium carbonate in deionized water and stir thoroughly to prepare an ammonium carbonate solution with a concentration of 0.35 mol / L;

[0053] 3) Mix the mixed salt solution and ammonium carbonate solution at a volume ratio of 1:1.2 and stir to carry out the reaction. The reaction is carried out at room temperature for 5-25 minutes. After the reaction is completed, a suspension is obtained. The suspension is filtered to obtain a chromium-containing emission active material precursor.

[0054] 4) Dry the chromium-containing emission active material precursor at 122°C for ≥6 hours to obtain a mixture whose main components are carbonate, chromate and aluminum hydroxide, which is the chromium-containing emission active material.

[0055] Performance testing:

[0056] Parallel tests: The chromium-containing emission active material prepared in this embodiment and the traditional 612-type barium calcium aluminate emission material were respectively made into coated diffusion cathodes (the substrates were both porous tungsten, and the surface films were both Os) using the same method. The emission performance of the two groups of coated diffusion cathodes was tested.

[0057] Test results show that the coated diffusion cathode made of the chromium-containing emissive material in this example can achieve an emission current density of 43.97 A / cm² at 1050℃. 2 Compared with coated cathodes made using traditional barium calcium aluminate emission materials, the emission current density can be increased by more than 45% under the same conditions.

[0058] Example 3

[0059] This example discloses a chromium-containing emission-active material for a coated diffusion cathode, and the specific preparation method includes the following steps:

[0060] 1) Weigh and mix Cr(NO3)3·9H2O, Ba(NO3)2, Ca(NO3)2·4H2O and Al(NO3)3·9H2O in a molar ratio of 1:20:2:5. Dissolve the mixed salt in deionized water to prepare a mixed salt solution with a concentration of 0.40 mol / L.

[0061] 2) Dissolve ammonium carbonate in deionized water and stir thoroughly to prepare an ammonium carbonate solution with a concentration of 0.30 mol / L;

[0062] 3) Mix the mixed salt solution and ammonium carbonate solution at a volume ratio of 1:1.3 and stir to carry out the reaction. The reaction is carried out at room temperature for 5-25 minutes. After the reaction is completed, a suspension is obtained. Filter the suspension to obtain a chromium-containing emission active material precursor.

[0063] 4) Dry the chromium-containing emission active material precursor at 120°C for ≥6 hours to obtain a mixture whose main components are carbonate, chromate and aluminum hydroxide, which is the chromium-containing emission active material.

[0064] Performance testing:

[0065] Parallel tests: The chromium-containing emission active material prepared in this embodiment and the traditional 612-type barium calcium aluminate emission material were respectively made into coated diffusion cathodes (the substrates were both porous tungsten, and the surface films were both Os) using the same method. The emission performance of the two groups of coated diffusion cathodes was tested.

[0066] Test results show that the coated diffusion cathode made of the chromium-containing emissive material in this example can achieve an emission current density of 29.22 A / cm² at 1050℃. 2 Compared with coated cathodes made using traditional barium calcium aluminate emission materials, the emission current density can be increased by about 10% under the same conditions.

[0067] Example 4

[0068] This example discloses a chromium-containing emission-active material for a coated diffusion cathode, and the specific preparation method includes the following steps:

[0069] 1) Weigh and mix Cr(NO3)3·9H2O, Ba(NO3)2, Ca(NO3)2·4H2O and Al(NO3)3·9H2O in a molar ratio of 36:39:13:40. Dissolve the mixed salt in deionized water to prepare a mixed salt solution with a concentration of 0.80 mol / L.

[0070] 2) Dissolve ammonium carbonate in deionized water and stir thoroughly to prepare an ammonium carbonate solution with a concentration of 0.65 mol / L;

[0071] 3) Mix the mixed salt solution and ammonium carbonate solution at a volume ratio of 1:1.5 and stir to carry out the reaction. The reaction is carried out at room temperature for 5-25 minutes. After the reaction is completed, a suspension is obtained. The suspension is filtered to obtain a chromium-containing emission active material precursor.

[0072] 4) Dry the chromium-containing emission active material precursor at 118°C for ≥6 hours to obtain a mixture whose main components are carbonate, chromate and aluminum hydroxide, which is the chromium-containing emission active material.

[0073] Performance testing:

[0074] Parallel tests: The chromium-containing emission active material prepared in this embodiment and the traditional 612-type barium calcium aluminate emission material were respectively made into coated diffusion cathodes (the substrates were both porous tungsten, and the surface films were both Os) using the same method. The emission performance of the two groups of coated diffusion cathodes was tested.

[0075] Test results show that the coated diffusion cathode made of the chromium-containing emissive material in this example can achieve an emission current density of 31.37 A / cm² at 1050℃. 2 Compared with coated cathodes made of traditional barium calcium aluminate emission materials, the emission current density can be increased by about 15% under the same conditions.

[0076] Example 5

[0077] This example discloses a chromium-containing emission-active material for a coated diffusion cathode, and the specific preparation method includes the following steps:

[0078] 1) Weigh and mix Cr(NO3)3·9H2O, Ba(NO3)2, Ca(NO3)2·4H2O and Al(NO3)3·9H2O in a molar ratio of 9:32:12:27. Dissolve the mixed salt in deionized water to prepare a mixed salt solution with a concentration of 0.50 mol / L.

[0079] 2) Dissolve ammonium carbonate in deionized water and stir thoroughly to prepare an ammonium carbonate solution with a concentration of 0.35 mol / L;

[0080] 3) Mix the mixed salt solution and ammonium carbonate solution at a volume ratio of 1:1.1 and stir to carry out the reaction. The reaction is carried out at room temperature for 5-25 minutes. After the reaction is completed, a suspension is obtained. Filter the suspension to obtain a chromium-containing emission active material precursor.

[0081] 4) Dry the chromium-containing emission active material precursor at 118°C for ≥6 hours to obtain a mixture whose main components are carbonate, chromate and aluminum hydroxide, which is the chromium-containing emission active material.

[0082] Performance testing:

[0083] Parallel tests: The chromium-containing emission active material prepared in this embodiment and the traditional 612-type barium calcium aluminate emission material were respectively made into coated diffusion cathodes (the substrates were both porous tungsten, and the surface films were both Os) using the same method. The emission performance of the two groups of coated diffusion cathodes was tested.

[0084] Test results show that the coated diffusion cathode made of the chromium-containing emissive material in this example can achieve an emission current density of 36.75 A / cm² at 1050 °C. 2 Compared with coated cathodes made using traditional barium calcium aluminate emission materials, the emission current density can be increased by about 28% under the same conditions.

[0085] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A chromium-containing emission-active material for a coated diffusion cathode, characterized in that, The chromium-containing emission active material comprises elements of chromium, barium, calcium, aluminum, carbon, hydrogen and oxygen; The molar ratio of the chromium, barium, calcium and aluminum is 1-36:18-40:1-15:2-45; The preparation of the chromium-containing emission active material comprises the following steps: 1) Weighing soluble salts of chromium, barium, calcium and aluminum according to the proportion, dissolving in solvent to configure a mixed salt solution; 2) Mixing the mixed salt solution with ammonium carbonate solution, stirring and reacting to obtain a suspension, and filtering to obtain a chromium-containing emission active material precursor; 3) Drying the chromium-containing emission active material precursor to obtain a chromium-containing emission active material, which mainly comprises barium chromate.

2. The chromium-containing emission active material for a coated film diffusion cathode according to claim 1, wherein The molar ratio of the chromium, barium, calcium and aluminum is 5-15:18-25:5-15:20-25.

3. The chromium-containing emission active material for a coated film diffusion cathode according to claim 1, wherein The soluble salt of chromium is selected from chromium nitrate or chromium chloride; the soluble salt of barium is selected from barium nitrate or barium chloride; the soluble salt of calcium is selected from calcium nitrate or calcium chloride; and the soluble salt of aluminum is selected from aluminum nitrate or aluminum chloride.

4. The chromium-containing active material for a coated film diffusion cathode according to claim 1, wherein The total concentration of solutes in the mixed salt solution is 0.1-1.0 mol / L.

5. The chromium-containing emission active material for a coated film diffusion cathode according to claim 1, wherein The concentration of the ammonium carbonate solution is 0.1-1.2 mol / L.

6. The chromium-containing emission active material for a coated film diffusion cathode according to claim 1, wherein The stirring and reacting is performed at 18-30℃ for 5-25 minutes.

7. The chromium-containing active material for a coated film diffusion cathode according to claim 1, wherein The drying condition is that the drying temperature is 80-150℃, and the drying time is ≥6h.

8. Use of the chromium-containing emission active material for film-coated diffusion cathode according to any one of claims 1-7 in the preparation of a film-coated diffusion cathode.

Images