纳米阴极材料电弧分散特性的理论分析

Theoretical analysis of arc dispersion property of nanocrystalline cathode materials

采用扫描电子显微镜观察了纳晶结构和粗晶结构的W-20%Cu和Cu的首击穿烧蚀形貌,指出纳晶电弧烧蚀痕迹分散,烧蚀比较轻微;常规材料烧蚀比较集中,且烧蚀比较严重。通过分析阴极材料的微观结构,建立了多晶材料电子所处势场结构模型,通过数值计算得出:晶粒越小,对应价电子子能带间能隙越大。分析认为,纳米晶结构的阴极材料电弧分散是由于较大的能隙阻碍了大量电子同时参与导电并迫使阴极斑点快速运动,从而避免大电流产生的焦耳热所导致的严重烧蚀。

The arc tracks on the conventional and nanostructured W-20%Cu and Cu after the first discharge were investigated by scanning electron microscopy. It is found that for the nanostructured cathodes, the erosion is slight and spreads over a dispersal area, while for the conventional cathodes, the erosion locates intensively at some specifically area. A simple model potential was built through analyzing the microstructure of the cathodes. The computational results show that the subband gap is wider for the nanostructured cathodes than for those of the conventional cathodes. It is the relatively wide energy gaps in the nanostructured cathode materials that clag electrons movement between the potential barriers and force cathode spots move quickly from one site to another, which in return avoids very high-current and severe cathode erosion.