Molybdenum powder for ceramic metallization and preparation method thereof

Abstract

The invention relates to molybdenum powder for ceramic metallizing and a preparing method of the molybdenum powder and belongs to the field of powder preparing of powder metallurgy of refractory metals. The molybdenum powder is approximately spherical and has the average particle size of 0.5-2.0 microns and the maximum particle size not larger than two times of the average particle size; or the molybdenum powder is flaky and has the average thickness of 0.3-1.5 microns and the specific area of 0.5-4.0m<2> / g. The preparing method uses an ammonium molybdate solution as a raw material, uses a polymeric surfactant as a disperser and uses commonly seen alcanol or ketones for enhancing the dispersing effect, and comprises the steps of adopting spraying drying to perform fast crystallizing and drying so as to obtain fine particle hollow thin-wall spherical ammonium molybdate crystals, and in-situ generating well-dispersed, micron and submicron, approximately spherical or flaky narrow particle-size distributed molybdenum powder by pyrolysis, hydrogen reduction, chemical decomposition, filtering, washing, secondary dispersion, drying and screening. The preparing method is subjected to technology improving and extension based on the existing production conditions of an enterprise, scale production can be easily realized, the production efficiency is high and the effects are good.

Description

technical field [0001] The invention relates to molybdenum powder for ceramic metallization and a preparation method thereof, belonging to the field of refractory metal powder metallurgy powder making. technical background [0002] With the development of vacuum electronic devices in the direction of ultra-high frequency, high power and long life, glass and metal sealing can no longer meet the requirements of tube making, and the development of ceramic-metal sealing technology is gradually put on the agenda. The process has been tested in China since 1958, and it was industrialized in 1975, and it has matured day by day. Common methods of ceramic-metal sealing are sintered metal powder method and active metal method, and others include oxide solder method, vapor deposition process, solid phase process, pressure sealing, electron beam welding, etc. Ceramic parts are mostly used as insulating materials in electric vacuum devices, and their properties are quite different from ...

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Problems solved by technology

Central South University (ZL200710035815.3, 200810030407.3, 200810030666.6) mainly adopts sol-spray drying-two-step or three-step reduction method to prepare ultrafine or nano molybdenum copper, tungsten molybdenum copper and rare earth doped ultrafine molybdenum powder, among which CN200810030666.6 implements Example 1 prepared ultra-fine molybdenum powder with a particle size of less than 0.5 μm, but its raw materials were limited to soluble molybdenum salts—ammonium dimolybdate and ammonium paramolybdate. Good narrow particle size distribution molybdenum powder

The medium-coarse molybdenum powder with a particle size greater than 4.0 μm can partially improve particle agglomeration through fluidized bed airflow crushing (ZL200910023113.2), while the micron and submicron molybdenum powders with a particle size of 0.5-2.0 μm inherit the morphology of the molybdenum oxide precursor. It exists in the form of aggregates of tens of microns and the agglomeration is relatively serious. Even with pre-dispersion treatment, it is easy to re-agglomerate due to its large surface activity. It is very difficult or even difficult to classify by the above physical means. Molybdenum powder has a certain hardness. During the grading process, the powder rubs against the grading wheel and the inner wall of the equipment at high speed, so it is very easy to introduce impurities such as iron, nickel, and chromium. The oxygen content of the processed powder is high, and it is prone to spontaneous combustion and even dust. explode

Beijing University of Science and Technology (ZL200810223084.X) used the uniform precipitation method to prepare ultrafine molybdenum powder, adding glass powder required for ceramic metallization and mixing it in the solution to obtain evenly mixed molybdenum powder particle size nanoscale Ceramic metallized powder, and then sintered to obtain a molybdenum skeleton with a network structure, a well-filled glass phase, and a dense metallized layer microstructure, but there is no evaluation of the sealing strength and airtightness, and no practical application

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