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Tungsten matrix for hot cathode and preparing method of tungsten matrix

A hot cathode and substrate technology, applied in electrical components, discharge tube/lamp parts, circuits, etc., can solve the problems affecting the emission performance of porous tungsten substrates, the difficulty of the process has not been paid attention to, and the inevitable residual carbon pollution, etc., to achieve The effect of good product consistency, narrow distribution and suitable porosity

Active Publication Date: 2018-07-06
GRIMAT ENG INST CO LTD
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Problems solved by technology

Beijing University of Science and Technology (201110213464.7) directly prepared porous tungsten matrix with special shape and size requirements by injection molding process, but 25-60% binder in the feed will inevitably residual carbon pollution, because tungsten is a strong Carbide forming elements, residual carbon will affect the actual emission performance of the porous tungsten substrate
Beijing University of Science and Technology (201510944267.0) used a jet mill to classify commercially available 3-8μm medium-grained tungsten powder to remove ultra-fine tungsten powder particles below 2μm to obtain tungsten powder with a narrow particle size distribution; on the basis of this tungsten powder raw material, injection Forming process is used to prepare porous tungsten matrix; in addition to the problem of binder carbon pollution, this invention has not yet paid attention to the preparation of small-aperture tungsten matrix with more difficult processes, the control of extremely low closed porosity and the acquisition of high-quality tungsten skeleton
Hefei University of Technology (201610291281.X) used plasma spheroidized tungsten powder after electric screening as raw material, and used spark plasma sintering technology to prepare porous tungsten bulk material; this invention overcomes the problem of pressing and forming spherical tungsten powder. However, after sintering The surface of the porous tungsten block that is in direct contact with the graphite mold will form a tungsten carbide layer. If the contaminated surface is not properly treated, it will be difficult to directly use it for the production of hot cathodes

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  • Tungsten matrix for hot cathode and preparing method of tungsten matrix

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preparation example Construction

[0054] The technical process of the preparation method of hot cathode tungsten matrix powder of the present invention is as follows figure 1 As shown, it includes the following steps: 1 wet classification; 2 vacuum degassing; 3 sieving; 4 cold isostatic pressing; 5 composite sintering; 6 hot isostatic pressing modification; ; 9 to remove copper; finally obtain a hot cathode tungsten or tungsten alloy substrate with suitable porosity, small pore size and narrow distribution, extremely low closed porosity, and high skeleton strength.

[0055] The preparation method of the tungsten substrate for hot cathodes of the present invention uses wet-classified tungsten or tungsten alloy powder with narrow particle size and medium-fine particles as raw materials, vacuum degassing, sieving, cold isostatic pressing, composite sintering, and then heat etc. Static pressure re-pressure re-firing modification, fully dense copper infiltration, final machining, high-temperature vacuum copper remo...

Embodiment 1

[0066] The tungsten-rhenium alloy powder with an average particle size of 0.5 μm is subjected to wet centrifugal classification, and the laser particle size span (SPAN) of the classified tungsten-rhenium alloy powder is 1.4; after drying at 50°C, the vacuum degree is kept at 5×10 -3 Pa, heat at 400°C for 2 hours for deep degassing and purification; pass through a 200-mesh sieve; put the tungsten-rhenium alloy powder evenly into the In the soft rubber mold, cold isostatic pressing under 250MPa pressure for 1min to obtain a tungsten-rhenium alloy compact with a relatively regular shape; place the tungsten-rhenium compact in a high-temperature tungsten mesh furnace, and sinter at a low temperature of 800°C in a high-purity hydrogen atmosphere 60min, then, directly switch the hydrogen atmosphere to 2×10 -3 Pa high vacuum, sintering at 1700°C for 10 minutes at high temperature to obtain a porous tungsten-rhenium alloy skeleton with suitable porosity and pore size distribution; Th...

Embodiment 2

[0068] The tungsten-iridium alloy powder with an average particle size of 2.4 μm is subjected to wet overflow classification, and the laser particle size span (SPAN) of the classified tungsten-iridium alloy powder is 1.2; after drying at 75°C, the vacuum degree is kept at 1×10 -4 Pa, heat at 500°C for 6 hours for deep degassing and purification; pass through a 150-mesh sieve; put the tungsten-iridium alloy powder evenly into the In the soft rubber mold, the tungsten-iridium alloy compact is obtained by cold isostatic pressing under 200MPa pressure for 10 minutes; the tungsten-iridium compact is placed in a high-temperature tungsten mesh furnace, and sintered at a low temperature of 1000°C in a high-purity hydrogen atmosphere 90min, then, directly switch the hydrogen atmosphere to 4×10 -3 Pa high vacuum, sintering at 1800°C for 30 minutes at high temperature to obtain a porous tungsten-iridium skeleton with suitable porosity and pore size distribution; The tungsten-iridium all...

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Abstract

The invention relates to a tungsten matrix for a hot cathode and a preparing method of the tungsten matrix, and belongs to the microwave vacuum electronic technology and the refractory metal powder metallurgical field. The tungsten matrix for the hot cathode is pure tungsten or tungsten iridium or tungsten osmium or tungsten rhenium alloy, the overall porosity is 13% to 22%, the average pore sizeis 0.2 to 1.5 micrometers, the percentage of close area is smaller than 0.5%, and the framework tensile strength is 150 to 300 MPa. The preparing method comprises the steps that wet classified narrowgranularity and medium-fine particle tungsten or tungsten alloy powder serves as a raw material, and vacuum degassing, screening, isostatic cool pressing, composite sintering, hot isostatic pressure repressing and re-sintering modifying, fully compacted copperizing, final machining and high-temperature vacuum copper removal are executed; the tungsten matrix for the hot cathode is proper in porosity, small in hole diameter, narrow in distribution, extremely low in percentage of close area, high in framework strength, and capable of being used for making low-temperature large current, high reliability and long service life cathodes. The preparing method is high in process controllability, good in product consistency and capable of easily achieving large-scale production.

Description

technical field [0001] The invention relates to a tungsten substrate for a hot cathode and a preparation method thereof, belonging to the fields of microwave vacuum electron technology and refractory metal powder metallurgy. technical background [0002] Microwave vacuum electronics technology is a research field with a long history, full of vitality and great potential for development, covering microwave electronics, cathode electronics, electromagnetic field theory, new material technology, vacuum technology, numerical calculation and simulation technology, etc., comprehensive extremely strong. The development history shows that the development of microwave vacuum electronic technology depends on the comprehensive strength of a country and determines the development level of microwave vacuum electronic devices in the country. At present, countries with strong comprehensive scientific and technological strengths such as the United States, Russia, the United Kingdom, France...

Claims

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Application Information

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IPC IPC(8): C22C27/04C22C1/08B22F3/11B22F3/10B22F3/04B22F3/15B22F3/24H01J1/146
CPCB22F3/04B22F3/101B22F3/1146B22F3/15B22F3/26B22F2003/247B22F2998/10C22C27/04H01J1/146
Inventor 周增林李艳惠志林
Owner GRIMAT ENG INST CO LTD
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