Co-doped Effects on Tungsten Copper Electrode IV

Use cobalt (Co) powder as activator can greatly promote the solid phase sintering of tungsten skeleton. Some studies have shown that due to the existence of W₆CO₇ phase or Co atom on the surface of tungsten particle, it has better wettability and improve the rearrangements of particles in sintering. Although the effect of Co additives can not be removed, the high phase boundary diffusion and the transformation of material are enhancing. In the process of tungsten skeleton sintering, W dissolved in Co, firstly formed "carrier phase" on the surface of tungsten particle and then the tungsten atom by spreading the opposing Co phase, when liquid phase sintering is preferentially formed in connecting skeleton. Co-W and Co-Cu binary phase diagram as follow:

During the infiltration, viscous Cu liquid flows and fills the pores in, which further improve the densification. When the Co content exceeds 0.2%, the pores in the material substantially eliminated, and a large number of solid phase tungsten particles is connected with each other to form continuous skeleton, which limit the flow of liquid Cu, block the increase of densification, and decrease the density because of the growth of tungsten particle.

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