辐照温度对钨材料表面微结构的影响

Influence of irradiation temperature on the surface damage of tungsten

本文采用100 eV的He+对钨进行辐照实验,考察了辐照温度变化(室温-800°C)对钨材料的表面损伤作用。分别采用扫描电镜(Scanning Electron Microscope,SEM)、透射电镜(Transmission Electron Microscope,TEM)、导电原子力显微镜(Conductive Atomic Force Microscopy,CAFM)以及X射线衍射(X Ray Diffraction,XRD)技术对辐照后样品的微观形貌、内表面缺陷分布以及晶格结构进行了分析。结果表明,He+辐照后钨样品表面出现了纳米绒毛结构层,这种结构层组织间的间距及覆盖率都随辐照温度的增加而增加。纳米结构层会造成样品表面损伤,产生表面离域化,但不会引起钨晶相的改变。通过无损伤的CAFM检测技术证实了样品表面绒毛结构层的形成与样品内表面纳米尺寸He泡的形成有关。

Background： In fusion reactors, W suffers from the displacement damage caused by high energy neutrons, and surface damage, such as blistering, erosion, and sputtering caused by low-energy（tens of eV to several keV） and high-flux（1020-1024 m-2·s-1） helium and hydrogen ions. Purpose： The understanding of the behavior of W materials in fusion environment is a major issue of the material-related stake of fusion reactors. Methods： W samples were irradiated with low-energy（100 eV） and high-flux（6×1020 ions·m-2·s-1） He＋ at a sample temperature changing from room temperature to 800 °C to a fluence of 1×1025 ions·m-2. Microscopic evolution of these samples was carried out using scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, conductive atomic force microscopy（CAFM） and X-ray diffraction（XRD）. Results： Analysis indicates that the nanometer-sized fibre-form structure is formed in the surface of W. The spacing and the covering degree of the nanostructure increase with the irradiation temperature. Nanostructure layer may cause the damage of W surface, resulting in surface delocalized, but does not cause a change in the crystal phase of tungsten. Conclusion： Non-destructive conductive atomic force microscopy gives the direct evidence that the forming of the nanometer-sized fibre-form structure is related to the nano-sized He bubbles. This is important for understanding the microstructure formation process of tungsten material.