Segregation and Preferential Sputtering of Cr in WCrY Smart Alloy
| Autor: | H. R. Koslowski, Christian Linsmeier, Janina Schmitz |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2020 |
| Předmět: |
010302 applied physics
Nuclear and High Energy Physics Condensed Matter - Materials Science Materials science Materials Science (miscellaneous) Analytical chemistry Flux chemistry.chemical_element Materials Science (cond-mat.mtrl-sci) FOS: Physical sciences Atmospheric temperature range Tungsten lcsh:TK9001-9401 01 natural sciences 010305 fluids & plasmas Ion Nuclear Energy and Engineering Low-energy ion scattering chemistry Sputtering 0103 physical sciences Monolayer lcsh:Nuclear engineering. Atomic power Surface layer ddc:624 |
| Zdroj: | Nuclear materials and energy 22, 100736-(2020). doi:10.1016/j.nme.2020.100736 Nuclear Materials and Energy Nuclear Materials and Energy, Vol 22, Iss, Pp-(2020) |
| Popis: | The temperature driven segregation of Cr to the surface of the tungsten-based WCrY alloy is analysed with low energy ion scattering of He+ ions with an energy of 1 keV in the temperature range from room temperature to 1000 K. Due to the high surface sensitivity, these measurements probe only the composition of the outermost monolayer. The surface concentration of Cr increases slightly when the temperature of the sample is increased up to 700 K and exhibits a much stronger increase when the sample temperature is further raised. The segregation enthalpy for Cr is obtained from the Langmuir-McLean relation and amounts to 0.7 eV. The surface concentration of Y shows a similar behaviour to the Cr concentration. The temperature thresholds between slow and accelerated surface density increases for Cr and Y are nearly the same. At a temperature of 1000 K the low energy ion scattering detects almost no W on the surface. The modified surface composition due to the segregated species, i.e. the mixed Cr/Y layer, stays stable during cool-down of the sample. Preferential sputtering is investigated using ion bombardment of 250 eV D atoms, resulting in an increase of the W surface density at room temperature. This effect is counteracted at elevated temperatures where segregation replenishes the lighter elements on the surface and prevents the formation of an all-W surface layer. The flux of segregating Cr atoms towards the surface is evaluated from the equilibrium between sputter erosion and segregation. 28 pages, 7 figures |
| Databáze: | OpenAIRE |
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