Thermal electron emission properties of novel W-Re mixed matrix cathodes

Abstract:

Tungsten-rhenium mixed powders were prepared by spray drying followed by two-step hydrogen reduction method. With these powders, W-Re mixed metal matrix cathodes were prepared by processes of die pressing, sintering and impregnation. Thermal electron emission properties of the cathodes were tested using the self-prepared pulsed power testing system. SEM, XRD and AES were adopted to analyze the surface morphology, phase structure and surface chemical elements of the cathodes respectively. It revealed that the phase of the cathodes depends on the content of rhenium in the matrixs. The W-75Re cathode (containing 75at% Re) is composed of Re3W singular phase. The emission testing results show that the W-75Re cathode impregnated with 411 salt has the lowest work function of 1.902 eV and the highest zero field emission current density of 14.03A cm-2 at 1000℃b among the prepared cathodes. It is possibly due to the high concentration of Re in the matrix, which results in fine grains in the matrix and is favourable to the formation of active Ba element and its diffusion on the cathode surface.

Key words:spray drying; tungsten-rhenium powder; tungsten-rhenium mixed cathodes; pulsed emission; work function