Spherical Tungsten Powder Application in Cathode Substrate

Spherical tungsten powder has the advantages of regular shape, good uniformity and adequate liquidity, using spherical tungsten powder to prepare the cathode can meet the current needs of engineering applications, which will play a positive role in cathode studies.

Cathode as the electron emission source of vacuum device, its research direction and development have the large influence on the development level of vacuum devices even weapons systems.

Modern dispenser cathode nowadays is one of the key researches of cathode. The common structures are usually composed of three parts: the porous tungsten matrix, emitting material and heater assembly. Of which the porous tungsten matrix is the framework and launch materials’ support of the entire cathode. As can be seen from the hot cathode development course, the porous tungsten matrix is the results of hot cathode constant pursuit of high emission current density and high reliability. Properties of the porous tungsten matrix, especially the pore structure and the pore distribution will directly affect the emission size, low evaporation rate, emission uniformity and lifetime of the cathode. In the actual production, it requires that the cathode matrix have a uniform distribution of pores of 24-26%. The porous tungsten matrix processes include compression molding process and the sintering process, the development of process is dependent on the progress in powder metallurgy process level, as well as affected by the matrix powder properties. If the matrix porosity and pore distribution can be reasonable controlled by process control, there will be a positive role in the cathode research.

Spherical tungsten powder has the advantages of regular shape, good uniformity and adequate liquidity. These advantages are especially suitable for the automatic press with the automatic filling, and the porous tungsten matrix can be obtained with the suitable size of pore and uniform distribution, compared to conventional tungsten powder, it has quite a lot of advantages. During the process of spherical tungsten powder producing the cathode, relationship between the initial porosity and compaction pressure is in line with Heckel's Law. Cathode pulse emission test results show that in 1050 ℃, cathode substrate prepared by spherical tungsten powder can obtain inflection current density of 20.46A / cm2, which can fully meet the current needs of engineering applications.

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