低能氦离子辐照对钨和钼材料的表面损伤作用

摘要

钨和钼材料具有高熔点、高热导率、低溅射率等优点成为国际热核实验反应堆计划中面向等离子体材料的候选材料。因此研究钨和钼材料的辐照损伤行为对于认识面向等离子体材料的辐照损伤机制具有重要意义。本文采用120 eV的 He+在873 K对钨和钼材料进行辐照实验，利用纳米压痕仪与导电模式原子力显微镜(Conductive Atomic Force Microscopy, CAFM)相结合，原位比较了钨和钼材料在辐照前后的表面形貌、表面微结构以及表层缺陷分布的变化特征。结果表明，低能He+辐照会导致钨和钼材料的近表面产生纳米量级氦泡缺陷，这些氦泡缺陷的存在使得样品表面产生绒毛或波浪状结构。纳米压痕深度分析和扫描电镜的分析结果表明，低能He+辐照会对Mo材料产生明显的刻蚀作用。本工作对于进一步认识低能氦离子辐照对面向等离子体材料的辐照损伤作用具有一定的科学参考意义。%Background: Due to their high melting point, high thermal conductivity, low sputtering yield, tungsten (W) and molybdenum (Mo) have been regarded as the potential candidates for plasma facing materials in fusion reactors.Purpose: This study aims to understand the irradiation damage behavior of W and Mo for the development of key fusion reactors materials. Methods: Polycrystalline W and Mo materials have been irradiated by 120-eV He ions with the irradiation temperature at 873 K.In situ analysis of these samples was carried out using nano-identation masked technique and non-destructive conductive atomic force microscopy (CAFM). The morphology, microscopic evolution and distribution of defects of these samples before and after irradiation are compared.Results:Analysis indicated that a large number of nanometer-sized helium bubbles were formed near the sample surface. Over-high internal pressure of nanometer-sized helium bubbles may result in forming protuberances of irradiated W and Mo. The section analysis of nano-identation showed that an obvious etching effect was founded on Mo materials. Conclusion:This work is of great significance for further understanding of the low-energy ion irradiation damage on plasma facing materials.