We have used Mossbauer spectroscopy on the 9.40 keV transition in R3Kr for the first time, in order to investigate the hyperfine interaction and lattice dynamics of Kr bubbles in Al. The spectra show two components: a single line from Kr atoms inside the bubble and a quadrupole component from Kr at the Kr-AI interface. The precipitates grow from 1.5 nm after implantation to 3.7 nm after 700 K annealing, while the characteristic Mossbauer temperature gradually decreases from 89 K to 64 K. At the same time a decrease in the isomer shift is observed. Both phenomena reflect the increase in atomic volume in the Kr bubbles during annealing. Our-experiments do not show melting in the temperature range 0-230 K.
Grid-enhanced plasma source ion implantation (GEPSII) is a newly proposed technique for inner surface modification of materials with cylindrical geometry. In this paper, a collisional fluid model is used to investigate the ion sheath dynamics between the grid electrode and the inner surface of a cylindrical bore during the GEPSII process. Assuming the initial ion density along the radial direction is not uniform but determined by diffusion mechanisms, the effects of grid electrode radius, target radius and ion–neutral collisions on the ion dose and impact energy are investigated by solving fluid equations for ions coupled with Boltzmann assumption for electrons and Poisson's equation. The results show that small gap distance between grid electrode and target is favourable to increase the ion dose and impact energy on the target. In addition, ion–neutral collisions can reduce both the ion dose and impact energy.
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