A kind of preparation method of porous cathode substrate

A porous cathode and substrate technology, which is applied in the field of powder metallurgy, can solve the problems of high cost, low material utilization rate, and long cycle, and achieve the effects of overcoming the influence of harmful impurities, improving electron emission performance, and high material utilization rate

Inactive Publication Date: 2011-11-30
UNIV OF SCI & TECH BEIJING
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] The purpose of the present invention is to provide a method for preparing a porous cathode substrate, which can overcome the complex process existing in the traditional sintered skeleton-copper immersion-machining-decopper process, low material utilization rate, high cost, easy to cause cathode poisoning, and poor reliability At the same time, it can effectively control the microstructure of the material such as porosity, pore size, uniformity of pore distribution, and open porosity, so as to improve the reliability of the cathode and improve its emission performance.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0017] The Fischer particle size of the tungsten powder is 4-6 μm, and the metal impurity content is less than 0.01%. The adhesive used is a wax-based adhesive. According to the proportion of powder volume fraction of 52%, the powder and binder are mixed on a disc high shear force mixer, the mixing temperature is 160 ℃, and the time is 2 hours, so that the binder and powder particles are mixed and dispersed uniform. The binder and powder mixture are further mixed on a twin-screw extruder and made into pelletized feed. The feed material is shaped on an injection molding machine to obtain a shaped blank. Dissolve and remove the soluble components such as paraffin wax and polystyrene in trichlorethylene, and the solvent degreasing time is 4 hours. After solvent degreasing, remove the remaining binder by heating and decomposing. The thermal decomposing temperature is from room temperature to 600°C. The binder is removed by a certain heating system, while avoiding the occurrence...

Embodiment 2

[0019] The Fischer particle size of the tungsten powder is 1-2 μm, and the metal impurity content is less than 0.01%. The spherical tungsten powder is obtained after the tungsten powder is treated with plasma spheroidization equipment. The binder used is a wax-based binder. According to the proportion of spherical tungsten powder with a volume fraction of 65%, the powder and binder are mixed on a disc high-shear mixer, and the mixing temperature is 160°C. , the time is 2 hours, so that the binder and the powder particles are mixed and dispersed evenly. The binder and powder mixture are further mixed on a twin-screw extruder and made into pelletized feed. The feed material is shaped on an injection molding machine to obtain a shaped blank. Dissolve and remove the soluble components such as paraffin wax and polystyrene in trichlorethylene, and the solvent degreasing time is 6 hours. After solvent degreasing, remove the remaining binder by heating and decomposing. The thermal d...

Embodiment 3

[0021] The tungsten powder with a mass fraction of 80% and a Fischer particle size of 4-6 μm and the iridium powder with a mass fraction of 20% and a Fischer particle size of 8-10 μm are ball milled and mixed for 240 minutes to obtain uniformly mixed raw material powder. According to the powder volume fraction of 55%, the binder and the powder are mixed on a disc high-shear mixer, the mixing temperature is 160 ° C, and the time is 2 hours, so that the binder and the powder particles are mixed and dispersed evenly. The binder and powder mixture are further mixed on a twin-screw extruder and made into pelletized feed. The feed material is shaped on an injection molding machine to obtain a shaped blank. Dissolve and remove the soluble components such as paraffin wax and polystyrene in trichlorethylene, and the solvent degreasing time is 6 hours. After solvent degreasing, remove the remaining binder by heating and decomposing. The thermal decomposing temperature is from room temp...

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Abstract

The invention provides a method for preparing a porous cathode substrate, which belongs to the field of powder metallurgy. The raw material powders used include various powders such as tungsten, iridium, rhenium, and scandium oxide. The various powders are mixed evenly according to a certain weight percentage, and the tungsten content is 40~100%. Mix and disperse the raw material powder particles and the binder evenly to make a granular feed, and the volume fraction of the powder in the feed is 40-75%. The feed material is formed into a green body of a certain shape on an injection molding machine, and the binder in the shaped green body is removed to obtain a porous cathode substrate. The invention has the advantages that the porous cathode substrate with special shape and size requirements can be directly prepared without mechanical processing, the material utilization rate is high, and the cost is low. It can effectively overcome the influence of harmful impurities brought by the traditional process, and improve the electron emission performance, service life and working reliability of the cathode. It can effectively control the pore size, pore distribution, porosity and pore connectivity of the material.

Description

technical field [0001] The invention belongs to the field of powder metallurgy and provides a method for preparing a porous cathode substrate. Background technique [0002] As the electron emission source of vacuum electronic devices, the cathode plays a vital role in the power output, lifetime, and working stability of high-power microwave devices. Due to the characteristics of high emission current density, low operating temperature and long service life, diffused cathodes are more and more widely used. Diffusion cathodes usually consist of a porous substrate (or sponge) mainly composed of tungsten and an electron-emitting active material impregnated in the porous substrate. The porous cathode substrate is an essential part of the diffused cathode. The electron emission active material impregnated in its porous framework will be lost after the surface emits electrons, and new substances should immediately diffuse to the surface of the cathode through the open pores in th...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B22F3/22B22F3/20H01J9/02
Inventor 秦明礼曲选辉张怀龙黄化钟小婧
Owner UNIV OF SCI & TECH BEIJING
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