H.B. Peng

Potential sputtering on SiO2 and Au induced by highly charged ions impact

Potential sputtering was studied using highly charged ions impacting on SiO2 and Au surface. A threshold effect for potential sputtering was found for gold.

Formation of bubbles and blisters in hydrogen ion implanted polycrystalline tungsten

ABSTRACT Tungsten (W) has been regarded as one of the most promising plasma facing materials (PFMs) in fusion reactors. The formation of bubbles and blisters during hydrogen (H) irradiation will affect the properties of W. The dependence of implantation conditions, such as fluence and energy, is therefore of great interest. In this work, polycrystalline tungsten samples were separated into two groups for study. The thick samples were implanted by 18 keV H3+ ions to fluences of 1 × 1018, 1 × 1019 and 1 × 1020 H+/cm2, respectively. Another thick sample was also implanted by 80 keV H2+ ions to a fluence of 2 × 1017 H+/cm2 for comparison. Moreover, the thin samples were implanted by 18 keV H3+ ions to fluences of 9.38 × 1016, 1.88 × 1017 and 5.63 × 1017 H+/cm2, respectively. Focused ion beam (FIB) combined with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used for micro-structure analysis, while time-of-flight ion mass spectrometry (ToF-SIMS) was used to characterize the H depth profile. It is indicated that bubbles and blisters could form successively with increasing H+ fluence. H bubbles are formed at a fluence of ∼5.63 × 1017 H+/cm2, and H blisters are formed at ∼1 × 1019 H+/cm2 for 18 keV H3+ implantation. On the other hand, 80 keV H2+ ions can create more trapping sites in a shallow projected range, and thus enhancing the blisters formation with a relatively lower fluence of 2 × 1017 H+/cm2. The crack-like microstructures beneath the blisters are also observed and prefer to form on the deep side of the implanted range.

Morphology and elemental behaviour in the alteration layer of borosilicate glass in simulated groundwater

ABSTRACT To understand the behaviour of nuclear waste glass in groundwater, borosilicate glasses were placed in simulated groundwater for more than 200 days. The composition of the simulated groundwater was similar to that of the groundwater in Beishan (a potential nuclear waste site). The pH value of groundwater was adjusted to 7.5, and the ratio of the surface area of glass to the volume of the solution (SA/V) was set to 10 m−1. Solutions and bulk glasses were characterised to obtain the elemental behaviour and surface morphology of the glass/solution interface, which was named the alteration layer. The mean thicknesses of the alteration layer were 5.16 ± 0.11 µm and 11.67 ± 0.28 µm at 70°C and 90°C, respectively. A thicker alteration layer was attributed to the lower surface activation energy of the glass and a high ion exchange between K+ and Na+ in the interface between the glass surface and the solution. For the elemental behaviour, mobile species B and Na were depleted, while K and Ca from the solution were enriched in the alteration layer due to ion exchange. Network species Si decreased in the layer, leading to the corrosion of the backbone of the glass; however, species Al increased, which implied that some [SiO4] units were partially replaced by [AlO4] units. In this work, glass in groundwater suffered much more intense corrosion than that in de-ionised water.