Influence of tungsten powder modification process on the rheological properties of feedstock and pore properties of porous tungsten matrix for barium-tungsten cathodes

The industrial reduced tungsten powders with the average particle size of 3～5 μm were modified by low-energy ball milling, airflow crushing, and radio frequency plasma spheroidization technology, respectively. The modified tungsten powders were used as the raw materials, and the metal powder injection molding (MIM) technology was applied to prepare the porous tungsten matrix for barium-tungsten cathodes. The influence of modification processes on the properties of tungsten powders, the rheological characteristics of the feedstock during the injection process, and the pore structure of the finally prepared porous tungsten matrix were systematically studied. The results show that the tungsten powders prepared by airflow crushing (ACW) and radio frequency plasma spheroidization technology (SW) exhibit the characteristics of narrower particle size distribution, smooth particle surfaces, and better powder dispersibility. Using the same binder, the feedstock prepared by ACW and SW powders has the higher powder loading. The porous tungsten matrix prepared by ACW and SW powders can meet the basic requirements of barium-tungsten cathodes with low closed pore rate, better pore connectivity, and more uniform pore size distribution.