As the core component of the diffusion cathode, the performance of porous tungsten matrix material will directly affect the output performance and life of microwave source. Therefore, the preparation of porous tungsten matrix is the key process of making a cathode material. In this paper, the industrial tungsten powder was used as raw material, whose particle size was modulated by fluidic classification firstly. Then via cold isostatic pressing and hydrogen sintering in high temperature, the porous tungsten sintered body was obtained. Finally, by the process of copper infiltration, machining and copper removal, the porous tungsten matrix was achieved. The result showed that compared with raw material tungsten powder, the classified tungsten powder’s particle size distribution was narrowed and its tap density obviously increased, indicating that it had better particle stacking performance. Setting the temperature between 1900°C and 2050°C the high temperature hydrogen sintering experiment was conducted, and it was found that the volume shrinkage ratio of tungsten sintered body increased with the sintering temperature, and correspondingly, its total porosity decreased from 24.4% at 1900°C to 20.8% at 2050°C. It was characterized by MIP (mercury intrusion porosimetry) that at high temperature between 1950~2050°C, the porous tungsten matrix with an open porosity of 21±1%, 1.30~1.60μm average pore size, a close cell ratio less than 1% and the skeleton strength greater than 150MPa was obtained. Thus this porous tungsten matrix is an ideal material to be applied to highly reliable diffusion bariated tungsten cathode manufacturing.
Production of target cathodes from composite silicides for applying protective coatings using casting and deformation technologies
