CN110931329A - Preparation method of columnar nickel sponge oxide cathode - Google Patents
Preparation method of columnar nickel sponge oxide cathode Download PDFInfo
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- CN110931329A CN110931329A CN201911266537.1A CN201911266537A CN110931329A CN 110931329 A CN110931329 A CN 110931329A CN 201911266537 A CN201911266537 A CN 201911266537A CN 110931329 A CN110931329 A CN 110931329A
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- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
- H01J9/02—Manufacture of electrodes or electrode systems
- H01J9/12—Manufacture of electrodes or electrode systems of photo-emissive cathodes; of secondary-emission electrodes
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Abstract
The invention discloses a preparation method of a columnar nickel sponge oxide cathode, which comprises the following steps: (1) inserting the pretreated columnar cathode substrate into a columnar depressed part at the end part of a core rod, then placing the core rod inserted with the columnar cathode substrate into a sleeve, wherein a clearance surrounding one circle is formed between the columnar cathode substrate and the inner wall of the sleeve above the end part of the core rod; (2) filling nickel powder in the gap, and dripping a binder; (3) drying, separating the columnar cathode substrate and the nickel powder attached to the outer wall of the columnar cathode substrate from the sleeve and the core rod; then sintering the columnar cathode substrate and the nickel powder attached to the outer wall of the columnar cathode substrate in a hydrogen atmosphere, and converting the nickel powder into a nickel sponge layer; (4) and filling ternary carbonate in the nickel sponge layer to obtain the columnar nickel sponge oxide cathode. The preparation method has the advantages of smooth cathode surface, easy size control, good consistency, easy preparation process operation, low preparation cost and high production efficiency.
Description
Technical Field
The invention relates to the technical field of electric vacuum. And more particularly, to a method for preparing a columnar nickel sponge oxide cathode.
Background
Oxide cathodes are one of the most widely used hot cathodes for electrical vacuum devices. The common oxide cathode is formed by directly spraying carbonate on a nickel base, and the cathode has high emission efficiency and large secondary emission coefficient, so the cathode is used in a long-wave-band, low-voltage and low-power vacuum tube. However, the cathode coating has loose structure, easy ignition and poor electron and ion bombardment resistance. The nickel sponge cathode overcomes the defects of the common oxide cathode to a certain extent, and is formed by sintering porous nickel powder on a base metal cylinder and then soaking carbonate.
The preparation method of the nickel sponge mainly comprises a screen coating method and a traditional molding method. The screen coating method is that a layer of adhesive, such as nitro-cotton solution, is sprayed on the base metal uniformly, then the nickel powder is screened on the base metal by a screen, the process is repeated for several times to reach a certain thickness, then the nickel powder is sintered in a hydrogen furnace, and a firm spongy layer can be obtained, and finally the carbonate is coated in a dip mode. The process for preparing the nickel sponge layer by the screen coating method is simple and easy to operate, but the thickness and the smoothness of the nickel sponge layer are greatly influenced by external factors, and the product is difficult to achieve good consistency. In order to solve the problems, a cathode researcher fills nickel powder into a mould provided with a cathode core, performs low-temperature moulding in a hydrogen furnace at 900-1000 ℃ to preliminarily form a nickel sponge layer, then removes the mould, performs high-temperature sintering in the hydrogen furnace at 1200-1300 ℃, and can dip-coat carbonate after the nickel sponge layer is further strengthened. The cathode manufactured by the method has uniform thickness, smooth surface and good product consistency. However, this method requires a long production period and low efficiency, and is not easy to realize mass production. In addition, the method needs to use a burning wet hydrogen oxidation mold frequently to ensure that the mold is molded at low temperature without sticking, so that the mold has high elimination rate and increased cost.
Therefore, it is desirable to provide a method for preparing a cylindrical nickel sponge oxide cathode with a recyclable mold, easily controlled cathode sponge thickness and porosity, and a smooth surface.
Disclosure of Invention
The invention aims to provide a preparation method of a columnar nickel sponge oxide cathode, which adopts the following technical scheme:
a preparation method of a columnar nickel sponge oxide cathode comprises the following steps:
(1) inserting the pretreated columnar cathode substrate into a columnar depressed part at the end part of the core rod, then placing the core rod inserted with the columnar cathode substrate into a sleeve, wherein the inner wall of the sleeve is in sliding assembly with the outer wall of the core rod, the bottom of the core rod is flush with the bottom of the sleeve, and a gap surrounding one circle is formed between the columnar cathode substrate and the inner wall of the sleeve above the end part of the core rod;
(2) filling nickel powder in the gap, and dropwise adding the binder until the nickel powder is completely infiltrated by the binder;
(3) drying, separating the columnar cathode substrate and the nickel powder attached to the outer wall of the columnar cathode substrate from the sleeve and the core rod; then sintering the columnar cathode substrate and the nickel powder attached to the outer wall of the columnar cathode substrate for 20-30min at 1200-1300 ℃ in a hydrogen atmosphere, and converting the nickel powder into a nickel sponge layer;
(4) and filling ternary carbonate in the nickel sponge layer to obtain the columnar nickel sponge oxide cathode. Optionally, the pretreatment process of the cylindrical cathode substrate in step (1) includes a cleaning process in acetone and an annealing process at 860 ℃ and 950 ℃ in a hydrogen furnace.
Optionally, the particle size of the nickel powder is 200-325 mesh.
Optionally, the arithmetic mean of the roughness profile offsets of the inner sleeve wall and the outer core rod wall are both less than 0.4 μm.
Optionally, the width of the gap in the radial direction is 0.01-0.05mm greater than the thickness of the nickel sponge layer.
Optionally, the gap has an extension, perpendicular to the radial direction, of 0.1-0.2mm greater than the extension of the nickel sponge layer.
Optionally, the binder is a nitrocellulose solution having a viscosity of 70CP to 90 CP.
Optionally, the ternary carbonate is BaCO3、SrCO3And CaCO3。
Optionally, the drying process in the step (3) is drying at 90-100 ℃ for 20-50 s.
Optionally, the step (4) of filling the interior of the nickel sponge layer with the ternary carbonate includes the steps of dip-coating a suspension of the ternary carbonate on the nickel sponge layer until a layer of carbonate is attached to the surface of the nickel sponge layer, and then scraping off the layer of carbonate attached to the surface of the nickel sponge layer.
The invention has the following beneficial effects:
the preparation method of the columnar nickel sponge oxide cathode provided by the invention is directly prepared by a normal-temperature demolding method, so that a mold oxidation process and a low-temperature molding process in the traditional molding method are omitted, the preparation process of the oxide cathode is simplified, the preparation cost of the molded cathode is effectively reduced, and the preparation efficiency is improved. Compared with a screen coating cathode, the novel molded cathode has the advantages of smooth surface, easily controlled size, good consistency, easy operation of preparation process, low preparation cost and high production efficiency, and solves the problems of instability, sparking, mold jumping and the like of a vacuum tube.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 shows a schematic of a cylindrical nickel sponge oxide cathode in accordance with the present invention.
FIG. 2 is a schematic view of a device for preparing a columnar nickel sponge oxide cathode according to the present invention.
Fig. 3 shows SEM images of nickel sponge of the columnar nickel sponge oxide cathode prepared according to the present invention and sintered nickel sponge by a conventional screen coating method.
Detailed Description
In order to illustrate the invention more clearly, the invention is further described below with reference to preferred embodiments and the accompanying figures 1-3. Similar components in fig. 1-3 are denoted by the same reference numerals. It should be noted that: the relative arrangement of the components and steps, the numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise.
The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.
Techniques and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail, but are intended to be considered a part of the specification where appropriate.
In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not limiting. Thus, other examples of the exemplary embodiments may have different values.
In the process of preparing the oxide cathode by the preparation method in the prior art, a wet-burning hydro-oxidation mold is required to be utilized to ensure that the mold does not occupy the mold during low-temperature molding, so that the mold has high elimination rate, long preparation period, low efficiency and high cost, and is not easy to produce on a large scale. The screen coating method has simple process and easy operation, but the thickness and the smoothness of the nickel sponge coating are greatly influenced by external factors, and the product is difficult to achieve good consistency.
Aiming at the problem, the invention provides a preparation method of a columnar nickel sponge oxide cathode, which comprises the following steps:
(1) inserting the pretreated columnar cathode substrate 1 into a columnar concave part 33 of a core rod end part 31, then placing a core rod 3 inserted with the columnar cathode substrate 1 into a sleeve 2, wherein the inner wall 21 of the sleeve is in sliding fit with the outer wall 34 of the core rod, the bottom 32 of the core rod is flush with the bottom 22 of the sleeve, and a gap surrounding one circle is formed between the columnar cathode substrate 1 and the inner wall 21 of the sleeve above the core rod end part 31;
(2) filling nickel powder in the gap, and dropwise adding the binder until the nickel powder is completely infiltrated by the binder;
(3) drying, separating the columnar cathode substrate 1 and the nickel powder attached to the outer wall of the columnar cathode substrate from the sleeve 2 and the core rod 3; then sintering the columnar cathode substrate 1 and the nickel powder attached to the outer wall 11 of the columnar cathode substrate for 20-30min at 1200-1300 ℃ in a hydrogen atmosphere, and converting the nickel powder into a nickel sponge layer 12;
(4) the interior of the nickel sponge layer 12 is filled with ternary carbonate to obtain a columnar nickel sponge oxide cathode.
It should be noted that, the end 31 of the mandrel is recessed downward to form a cylindrical recess 33, and after the cylindrical cathode substrate 1 is inserted into the recess 33, the circumferential wall of the recess 33 and the outer wall 11 of the cylindrical cathode substrate 1 are in a state of being attached to each other, and if there is a gap between the two, the nickel powder will penetrate and adhere to the outer wall 11 of the cylindrical cathode substrate 1. The length of the recess 33 in the axial direction is determined by the position of the nickel sponge layer 12 on the columnar cathode substrate 1, the nickel sponge layer 12 is not formed on the columnar cathode substrate 1 inserted into the recess 33, and the nickel sponge layer 12 is formed on the outer wall 11 of the columnar cathode substrate 1 which forms a circumferential gap with the inner wall 21 of the sleeve 2 above the end 31 of the stem 3.
After the gaps are filled with the nickel powder, the binder is dripped, and the nickel powder is completely soaked by the binder, mutually bonded and also bonded on the outer wall 11 of the columnar cathode substrate 1; meanwhile, the roughness of the inner wall 21 of the sleeve is less than 0.4 mu m, and the nickel powder can not be bonded on the inner wall 21. Putting the columnar cathode substrate into an oven, drying the columnar cathode substrate for 20-50s at 90-100 ℃, then ejecting the core rod 3 out of the sleeve 2 from the bottom by using an ejector rod, and pulling the columnar cathode substrate 1 out of the concave part 33 at the end part 31 of the core rod to obtain the columnar cathode substrate 1 and nickel powder attached to the outer wall 11 of the columnar cathode substrate.
Sintering the columnar cathode substrate 1 and the nickel powder attached to the outer wall 11 of the columnar cathode substrate for 20-30min at 1200-1300 ℃ in a hydrogen atmosphere, and converting the nickel powder into a nickel sponge layer 12;
the interior of the nickel sponge layer 12 is filled with ternary carbonate to obtain a columnar nickel sponge oxide cathode. One possible method for filling the interior of the nickel sponge layer 12 with the ternary carbonate is to dip-coat a suspension of the ternary carbonate on the nickel sponge layer 12 until a layer of carbonate is attached to the surface of the nickel sponge layer 12, and then scrape off the layer of carbonate attached to the surface of the nickel sponge layer 12 until a uniform nickel powder layer is exposed.
Before the cylindrical cathode substrate 1 is used, a pretreatment process, specifically cleaning in acetone, and then annealing at 860 ℃ and 950 ℃ in a hydrogen furnace, is required. The pretreatment process helps to eliminate the internal stress of the columnar cathode substrate 1, thereby improving the adhesion between the outer wall 11 of the columnar cathode substrate 1 and the nickel powder.
In the specific implementation process, the particle size of the selected nickel powder is 200-325 meshes, so that the nickel powder with the particle size is beneficial to the formation of nickel sponge holes, and the carbonate is easier to infiltrate. Further, for example, the particle size of the nickel powder can be, but not limited to, 315 mesh, 220 mesh, 305 mesh, 230 mesh, 295 mesh, 240 mesh, 285 mesh, or 250 mesh, 275 mesh, etc.
The inner sleeve wall 21 and the outer core rod wall 34 are in sliding fit and are fixedly restrained with each other by virtue of friction force between the two. If the friction force is too small, the material is not firm and may slip off in the preparation process; if the frictional force is too large, the assembly and separation process thereof may be difficult, particularly after nickel powder is attached to the outer wall 11 of the cylindrical cathode base 1. In the invention, the arithmetic mean value of the roughness profile offset distances of the sleeve inner wall 21 and the core rod outer wall 34 is less than 0.4 μm, and the arrangement ensures the firm assembly of the sleeve inner wall and the core rod outer wall and is convenient for separating the sleeve inner wall and the core rod outer wall.
In the invention, when the dies such as the sleeve 2, the core bar 3 and the like are designed, the width of the gap is 0.01-0.05mm larger than the thickness of the nickel sponge layer 12 to be obtained in the radial direction, so that the thickness of the nickel powder attached to the outer wall 11 of the columnar cathode substrate 1 is larger than the thickness of the nickel sponge layer 12 to be obtained, and the required thickness of the nickel sponge layer 12 is just obtained after sintering shrinkage; at the same time, the large gap width also facilitates the separation of the nickel sponge layer 12 from the interior of the sleeve 2. The gap has an extension in the direction perpendicular to the radial direction of 0.1-0.2mm greater than the required extension of the nickel sponge layer 12, so that the deformed part of the nickel sponge layer 12 at the top of the gap can be repaired, resulting in a high-quality nickel sponge layer 12 of satisfactory length.
The binder used in the invention is a nitrocellulose solution, and the viscosity of the nitrocellulose solution is 70-90 CP. The ternary carbonate used is BaCO3、SrCO3And CaCO3。
The nickel sponge of the columnar nickel sponge oxide cathode prepared by the method provided by the invention is shown in fig. 3a, compared with the nickel sponge prepared by a screen coating method, the nickel sponge layer 12 prepared by the novel molding method has the advantages of smooth surface, clear thickness size and length size, more uniform pore distribution, easier formation of uniform emission surface, and uniform work function distribution provided by the uniformity of the surface, thereby forming uniform emission. By respectively using more than 30 cathodes as samples, the pore size distribution of the nickel sponge prepared by the conventional screening and coating method is 60-80 percent through calculation, while the pore size distribution of the nickel sponge prepared by the method is 68-69 percent, so that the pore size of the nickel sponge prepared by the method is more uniform. The novel columnar molded nickel sponge cathode is manufactured and is arranged in a magnetron, and the test is carried out after decomposition, activation and aging, so that the power meets the requirement, and the problems of sparking, mold jumping and the like in the test process are reduced.
It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the invention and are not to be construed as limiting the embodiments of the present invention, and it will be apparent to those skilled in the art that other variations and modifications can be made on the basis of the above description.
Claims (10)
1. The preparation method of the columnar nickel sponge oxide cathode is characterized by comprising the following steps of:
(1) inserting the pretreated columnar cathode substrate into a columnar depressed part at the end part of the core rod, then placing the core rod inserted with the columnar cathode substrate into a sleeve, wherein the inner wall of the sleeve is in sliding assembly with the outer wall of the core rod, the bottom of the core rod is flush with the bottom of the sleeve, and a gap surrounding one circle is formed between the columnar cathode substrate and the inner wall of the sleeve above the end part of the core rod;
(2) filling nickel powder in the gap, and dropwise adding the binder until the nickel powder is completely infiltrated by the binder;
(3) drying, separating the columnar cathode substrate and the nickel powder attached to the outer wall of the columnar cathode substrate from the sleeve and the core rod; then sintering the columnar cathode substrate and the nickel powder attached to the outer wall of the columnar cathode substrate for 20-30min at 1200-1300 ℃ in a hydrogen atmosphere, and converting the nickel powder into a nickel sponge layer;
(4) and filling ternary carbonate in the nickel sponge layer to obtain the columnar nickel sponge oxide cathode.
2. The method as set forth in claim 1, wherein the pretreatment process of the cylindrical cathode substrate in the step (1) comprises a cleaning process in acetone and an annealing process at 860 ℃ to 950 ℃ in a hydrogen furnace.
3. The method according to claim 1, wherein the particle size of the nickel powder is 200-325 mesh.
4. The method of claim 1 wherein the roughness profile offsets of the inner sleeve wall and the outer core rod wall are each less than 0.4 μm on an arithmetic average.
5. The production method according to claim 1, wherein the width of the gap is larger than the thickness of the nickel sponge layer by 0.01 to 0.05mm in the radial direction.
6. The production method according to claim 1, wherein the gap extends over 0.1 to 0.2mm longer than the nickel sponge layer in a direction perpendicular to the radial direction.
7. The method as claimed in claim 1, wherein the binder is a nitrocellulose solution having a viscosity of 70CP to 90 CP.
8. The method according to claim 1, wherein the ternary carbonate is BaCO3、SrCO3And CaCO3。
9. The method according to claim 1, wherein the drying in the step (3) is performed at 90-100 ℃ for 20-50 s.
10. The method according to claim 1, wherein the step (4) of filling the interior of the nickel sponge layer with the ternary carbonate comprises the steps of dip-coating a suspension of the ternary carbonate on the nickel sponge layer until a layer of carbonate is attached to the surface of the nickel sponge layer, and then scraping off the layer of carbonate attached to the surface of the nickel sponge layer.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111545760A (en) * | 2020-05-18 | 2020-08-18 | 安徽华东光电技术研究所有限公司 | Nickel sponge matrix, preparation method thereof and oxide cathode |
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| JPH04202635A (en) * | 1990-11-30 | 1992-07-23 | New Japan Radio Co Ltd | Production of porous metallic base material |
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| CN105244244A (en) * | 2015-10-13 | 2016-01-13 | 甘肃虹光电子有限责任公司 | Oxide cathode |
| CN108054069A (en) * | 2017-11-06 | 2018-05-18 | 昆山国力大功率器件工业技术研究院有限公司 | A kind of oxide-coated cathode powder filling device and its application method |
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2019
- 2019-12-11 CN CN201911266537.1A patent/CN110931329B/en active Active
Patent Citations (5)
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| SU1123438A1 (en) * | 1982-02-26 | 1992-03-07 | Предприятие П/Я Р-6021 | Method of manufacturing spongy cathode |
| JPH04202635A (en) * | 1990-11-30 | 1992-07-23 | New Japan Radio Co Ltd | Production of porous metallic base material |
| CN1109922A (en) * | 1995-03-11 | 1995-10-11 | 吉林大学 | Process for preparing spongy foam nickel |
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| CN111545760A (en) * | 2020-05-18 | 2020-08-18 | 安徽华东光电技术研究所有限公司 | Nickel sponge matrix, preparation method thereof and oxide cathode |
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