阅读说明：本技术 一种磁控管用的阴极的制备方法 (Preparation method of cathode for magnetron ) 是由 漆世锴 王小霞 王兴起 高阳 查兵 刘理 曾伟 徐梦婷 于 2019-09-16 设计创作，主要内容包括：一种磁控管用阴极的制备方法,该方法包括以下步骤：(1)将处理好的螺旋钨丝套在圆柱形内胆上,然后在套有内胆的螺旋钨丝表面均匀涂覆三氧化二铝悬浊液,每涂覆一次后再在烘干机下烘干,重复上述操作直至三氧化二铝层厚度超过螺旋钨丝的直径,取出内胆,最后放入高温氢气炉中烧结获得绝缘性能良好的热子；(2)利用高压喷枪在热子的表面均匀喷涂上钨粉层,反复喷涂烘干,然后放入高温氢气炉中烧结形成钨海绵层；(3)利用高压喷枪在钨海绵层的表面均匀喷涂电子发射活性物质,反复喷涂烘干,然后放入高温真空炉中烧结形成陶瓷层,即制备得到磁控管用的阴极。本发明制得的阴极具有工作温度低,蒸发小,抗中毒性能好,耐电子轰击性能强的优点。(A method for preparing a cathode for a magnetron, the method comprising the steps of: (1) sleeving the processed spiral tungsten wire on a cylindrical inner container, uniformly coating an aluminum oxide suspension on the surface of the spiral tungsten wire sleeved with the inner container, drying the spiral tungsten wire in a dryer after each coating, repeating the operation until the thickness of the aluminum oxide layer exceeds the diameter of the spiral tungsten wire, taking out the inner container, and finally putting the inner container into a high-temperature hydrogen furnace for sintering to obtain a heater with good insulating property; (2) uniformly spraying a tungsten powder layer on the surface of the thermite by using a high-pressure spray gun, repeatedly spraying and drying, and then putting into a high-temperature hydrogen furnace for sintering to form a tungsten sponge layer; (3) and (3) uniformly spraying electron emission active substances on the surface of the tungsten sponge layer by using a high-pressure spray gun, repeatedly spraying and drying, and then putting into a high-temperature vacuum furnace to sinter to form a ceramic layer, thus preparing the cathode for the magnetron. The cathode prepared by the invention has the advantages of low working temperature, small evaporation, good poisoning resistance and strong electron bombardment resistance.)

1. A method for preparing a cathode for a magnetron, the method comprising the steps of:

sleeving the processed spiral tungsten wire on a cylindrical inner container, uniformly coating an aluminum oxide suspension on the surface of the spiral tungsten wire sleeved with the inner container, drying the spiral tungsten wire in a dryer after each coating, repeating the operation until the thickness of the aluminum oxide layer exceeds the diameter of the spiral tungsten wire, taking out the inner container, and finally putting the inner container into a high-temperature hydrogen furnace for sintering to obtain a heater with good insulating property;

uniformly spraying a tungsten powder layer on the surface of the thermite by using a high-pressure spray gun, repeatedly spraying and drying, and then putting into a high-temperature hydrogen furnace for sintering to form a tungsten sponge layer;

and (3) uniformly spraying electron emission active substances on the surface of the tungsten sponge layer by using a high-pressure spray gun, repeatedly spraying and drying, and then putting into a high-temperature vacuum furnace to sinter to form a ceramic layer, thus preparing the cathode for the magnetron.

2. The method of claim 1, wherein the alumina suspension of step (1) is a mixture of 20wt% alumina powder, 10wt% methanol solution (1 ~ 3) and 70wt% nitro-cotton solution (1 ~ 3), wherein the alumina powder has a purity of 4N and an average diameter of less than 1 μm, and the spiral tungsten filament has a filament diameter of 1.2 ~ 1.4.4 mm, a spiral diameter of 8.5 ~ 8.7.7 mm, and a spiral length of 8623 mm and 23 ~ 27 mm.

3. The method of claim 1, wherein the sintering process in the high temperature hydrogen furnace in step (1) comprises the steps of heating linearly from room temperature to 1450 ~ 1800 ℃ over 2 ~ 20 minutes, maintaining the temperature for 10 ~ 30 minutes, and then cooling linearly to room temperature over 2 ~ 12 hours to obtain the thermite with good insulating property.

4. The method of claim 1, wherein the repeatedly spraying and drying step (2) is performed so that the thickness of the tungsten powder layer is 20 ~ 200 μm, the purity of the tungsten powder is 4N, the particle size is 1 ~ 2 μm, the pressure of the high pressure spray gun used for spraying the tungsten powder layer is 0.4 ~ 0.8.8 Mpa, the tungsten powder layer is dried by a dryer after each spraying, and the above operations are repeated until the tungsten powder layer has a certain thickness.

5. The method of claim 1, wherein the sintering process in the high temperature hydrogen furnace in step (2) comprises linearly raising the temperature from room temperature to 1500 ~ 2000 ℃ over 0.5 ~ 2 hours, maintaining the temperature for 0.5 ~ 2 hours, and linearly lowering the temperature to room temperature over 2 ~ 12 hours to obtain the tungsten sponge layer.

6. The method of claim 1, wherein the electron emission active material in the step (3) is one of a yttrium zirconate suspension, a gadolinium hafnate suspension, and a yttrium hafnate suspension, wherein the yttrium zirconate suspension is a mixture of 20wt% yttrium zirconate powder and 80wt% nitro-cotton solution (1 ~ 3)% and the gadolinium hafnate suspension is a mixture of 20wt% gadolinium hafnate powder and 80wt% nitro-cotton solution (1 ~ 3)% and the yttrium hafnate suspension is a mixture of 20wt% yttrium hafnate powder and 80wt% nitro-cotton solution (1 ~ 3)% and the pressure applied to the high pressure of the spray gun for spraying the electron emission active material is 0.5 ~ 1.0.0 Mpa and the spray gun is dried by a dryer after spraying the electron emission active material once and the above operation is repeated until a certain thickness is reached.

7. The method of claim 1, wherein the sintering process in the high temperature vacuum furnace in step (3) is performed by first linearly raising the temperature from room temperature for 2 ~ 4 hours to 1400 ~ 1800 ℃ and maintaining the temperature for 2 ~ 7 hoursThe ceramic layer is obtained after the temperature is linearly reduced to the normal temperature within 12 ~ 24 hours, and the vacuum degree in the sintering process is always superior to 10^-5Pa, and the thickness of the final sintered ceramic layer is 50 ~ 300 μm.

Technical Field

The invention relates to a preparation method of a cathode for a magnetron.

Background

A magnetron is an electric vacuum device used to generate microwave energy. The tube is a vacuum diode placed in a constant magnetic field, electrons in the tube interact with a high-frequency electromagnetic field under the control of the constant magnetic field and the constant electric field which are perpendicular to each other, and energy obtained from the constant electric field can be converted into microwave energy, so that the aim of generating the microwave energy is fulfilled. Currently, magnetrons have proven to be the most efficient and economical microwave generator for industrial use as a vacuum electronic device. The cathode is one of the heart parts of the magnetron, and the quality of the cathode directly influences the output power and the service life of the magnetron; in the normal working process of the high-power magnetron, the cathode of the high-power magnetron works at a higher temperature and in a worse working environment, the surface of the cathode is bombarded by violent electrons and ions, and the traditional oxide cathode and the barium-tungsten cathode can lose effectiveness.

Disclosure of Invention

The invention aims to provide a method for preparing a cathode for a magnetron, which solves the problems that the conventional high-power magnetron works at a higher temperature and in a worse working environment, the surface of the cathode is bombarded by violent electrons and ions, and the conventional oxide cathode and the conventional barium-tungsten cathode fail in the normal working process.

In order to achieve the above object, the technical scheme is that the preparation method of the cathode for the magnetron comprises the following steps:

(1) sleeving the processed spiral tungsten wire on a cylindrical inner container, uniformly coating an aluminum oxide suspension on the surface of the spiral tungsten wire sleeved with the inner container, drying the spiral tungsten wire in a dryer after each coating, repeating the operation until the thickness of the aluminum oxide layer exceeds the diameter of the spiral tungsten wire, taking out the inner container, and finally putting the inner container into a high-temperature hydrogen furnace for sintering to obtain a heater with good insulating property;

(2) uniformly spraying a tungsten powder layer on the surface of the thermite by using a high-pressure spray gun, repeatedly spraying and drying, and then putting into a high-temperature hydrogen furnace for sintering to form a tungsten sponge layer;

(3) and (3) uniformly spraying electron emission active substances on the surface of the tungsten sponge layer by using a high-pressure spray gun, repeatedly spraying and drying, and then putting into a high-temperature vacuum furnace to sinter to form a ceramic layer, thus preparing the cathode for the magnetron.

Advantageous effects

Compared with the prior art, the invention has the following advantages.

1. The cathode prepared by the invention has the advantages of low working temperature, small evaporation, good poisoning resistance and strong electron bombardment resistance;

2. the invention has simple manufacturing process and lower cost and has better application potential in a high-power magnetron.

Drawings

The invention is further described below with reference to the accompanying drawings.

FIG. 1 is a flow chart of the cathode preparation of the present invention;

FIG. 2 is a schematic view of the spiral tungsten filament and the inner container of the present invention;

FIG. 3 is EDS spectrum of yttrium zirconate cathode prepared in the first embodiment of the present invention

FIG. 4 is a cross-sectional view of the overall structure of a yttrium zirconate cathode fabricated according to a first embodiment of the present invention;

FIG. 5 is a thermal emission I-V characteristic curve of a yttrium zirconate cathode prepared according to a first embodiment of the invention;

FIG. 6 is a graph of the life characteristics of a yttrium zirconate cathode prepared in accordance with example one of the present invention;

FIG. 7 is an EDS spectrum of a gadolinium hafnate cathode prepared in example two of the present invention;

fig. 8 is a cross-sectional view of the overall structure of a gadolinium hafnate cathode according to a second embodiment of the present invention;

FIG. 9 is a thermal emission I-V characteristic curve of a gadolinium hafnate cathode prepared according to a second embodiment of the present invention;

FIG. 10 is a graph illustrating lifetime characteristics of a gadolinium hafnate cathode prepared according to example two of the present invention;

FIG. 11 is an EDS spectrum of a yttrium hafnate cathode prepared in example three of the present invention;

FIG. 12 is a sectional view showing the overall structure of a yttrium hafnate cathode according to a third embodiment of the present invention;

FIG. 13 is a thermal emission I-V characteristic curve of a yttrium hafnate cathode prepared according to a third embodiment of the present invention;

fig. 14 is a graph showing the lifetime characteristics of a yttrium hafnate cathode prepared according to example three of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to specific embodiments and accompanying drawings.

A method for preparing a cathode for a magnetron, as shown in fig. 1 and 2, the method comprising the steps of:

(4) sleeving the processed spiral tungsten wire on a cylindrical inner container, uniformly coating an aluminum oxide suspension on the surface of the spiral tungsten wire sleeved with the inner container, drying the spiral tungsten wire in a dryer after each coating, repeating the operation until the thickness of the aluminum oxide layer exceeds the diameter of the spiral tungsten wire, taking out the inner container, and finally putting the inner container into a high-temperature hydrogen furnace for sintering to obtain a heater with good insulating property;

(5) uniformly spraying a tungsten powder layer on the surface of the thermite by using a high-pressure spray gun, repeatedly spraying and drying, and then putting into a high-temperature hydrogen furnace for sintering to form a tungsten sponge layer;

(6) and (3) uniformly spraying electron emission active substances on the surface of the tungsten sponge layer by using a high-pressure spray gun, repeatedly spraying and drying, and then putting into a high-temperature vacuum furnace to sinter to form a ceramic layer, thus preparing the cathode for the magnetron.

The alumina suspension in the step (1) is a mixed solution of 20wt% of alumina powder, 10wt% of (1 ~ 3)% methanol solution and 70wt% of (1 ~ 3)% nitro-cotton solution, wherein the purity of the alumina powder is 4N, the average grain diameter is less than 1 mu m, the wire diameter of the spiral tungsten wire is 1.2 ~ 1.4mm, the spiral diameter is 8.5 ~ 8.7.7 mm, and the spiral length is 23 ~ 27 mm.

The sintering process of the high-temperature hydrogen furnace in the step (1) comprises the steps of linearly raising the temperature to 1450 ~ 1800 ℃ from the normal temperature within 2 ~ 20 minutes, preserving the temperature for 10 ~ 30 minutes, and linearly lowering the temperature to the normal temperature within 2 ~ 12 hours to obtain the thermite with good insulating property.

The thickness of the tungsten powder layer repeatedly sprayed and dried in the step (2) is 20 ~ 200 microns, the purity of the tungsten powder is 4N, the particle size is 1 ~ 2 microns, the air pressure value adopted by a high-pressure spray gun for spraying the tungsten powder layer is 0.4 ~ 0.8.8 Mpa, the tungsten powder layer is dried by a dryer after being sprayed once, and the operation is repeated until the tungsten powder layer is of a certain thickness.

The sintering process of the high-temperature hydrogen furnace in the step (2) comprises the steps of linearly raising the temperature to 1500 ~ 2000 ℃ from the normal temperature within 0.5 ~ 2 hours, preserving the temperature for 0.5 ~ 2 hours, and linearly lowering the temperature to the normal temperature within 2 ~ 12 hours to obtain the tungsten sponge layer.

The electron emission active material in the step (3) is one of a yttrium zirconate suspension, a gadolinium hafnate suspension and a yttrium hafnate suspension, wherein the yttrium zirconate suspension is a mixed solution of 20wt% of yttrium zirconate powder and 80wt% of (1 ~ 3)% of nitrocotton solution, the gadolinium hafnate suspension is a mixed solution of 20wt% of gadolinium hafnate powder and 80wt% of (1 ~ 3)% of nitrocotton solution, the yttrium hafnate suspension is a mixed solution of 20wt% of yttrium hafnate powder and 80wt% of (1 ~ 3)% of nitrocotton solution, a high-pressure spray gun for spraying the electron emission active material has a pressure value of 0.5 ~ 1.0.0 Mpa, and after each time of spraying the electron emission active material, the high-pressure spray gun is dried by using a dryer, and the operation is repeated until a certain thickness is achieved.

The sintering process in the high-temperature vacuum furnace in the step (3) comprises the steps of firstly linearly increasing the temperature from the normal temperature to 1400 ~ 1800 ℃ within 2 ~ 4 hours, preserving the temperature for 2 ~ 7 hours, and then linearly decreasing the temperature to the normal temperature within 12 ~ 24 hours to obtain the ceramic layer, wherein the vacuum degree in the sintering process is always superior to 10^-5Pa, and the thickness of the final sintered ceramic layer is 50 ~ 300 μm.