The migration behaviour of xenon implanted into glassy carbon

This study is in two parts. Both parts are geared towards the study of the effectiveness of glassy carbon as a good storage material was investigated. Firstly, 200 keV Xe ions were implanted into glassy carbon substrates to a fluence of 1×1016 ions/cm2 at room temperature. Also, we have also investigated the effect of SHI irradiation on Xe as-implanted samples at a fluence of 1×1014 ions/cm2. After implantation and swift heavy ion irradiation, the samples were investigated using several techniques. This was with a view to characterizing the level of damage created by the ion bombardment, the distributions of the Xe ions in glassy carbon and the effect of SHI irradiation on these distributions. The irradiated and un-irradiated but implanted with Xe samples were isochronally annealed in a vacuum in steps of 100 C for 5 hours at temperatures ranging from 300 C – 800 C and 900 C – 1500 C, respectively.Thesis (PhD (Physics))--University of Pretoria, 2019.PhysicsPhD (Physics)Unrestricte

The nature of surface defects in Xe ion-implanted glassy carbon annealed at high temperatures: Raman spectroscopy analysis

Please read abstract in the article.The National Research Foundation (NRF) of South Africa via iThemba LABS Materials Research Department (MRD) and University of Pretoria (South Africa).http://www.elsevier.com/locate/apsuschj2021Physic

Migration behaviour of selenium implanted into polycrystalline 3C–SiC

Please read abstract in the article.The National Research Foundation and The World Academy of Science.http://www.journals.elsevier.com/vacuum2021-05-01hj2020Physic

Effect of heat treatment on the migration behaviour of Sr and Ag CO-implanted in glassy carbon

The effect of annealing on the diffusion of silver, silver and strontium co-implanted in glassy carbon was investigated. Glassy carbon samples were implanted with 360 keV Ag ions at room temperature. The RBS profile showed that Fickian diffusion of Ag in glassy carbon is only observed at temperatures ranging from 500 °C–600 °C. At higher annealing temperatures, there was a significant loss of Ag and no Ag was retained in glassy carbon at 700 °C. Glassy carbon samples were also co-implanted with Ag and Sr. The diffusion behaviour of Ag when co-implanted with Sr was similar to that of the singly implanted Ag sample. However, the introduction of Sr into the glassy carbon matrix assisted in the retainment of the Ag ions. The co-implantation of Ag and Sr resulted in a change in the diffusion behaviour of Sr in glassy carbon. The implantation of Ag with Sr prevented the movement of Sr deeper into the bulk of the glassy carbon. The non-movement of Sr into the bulk of the glassy carbon was attributed to the increase of radiation damage near the surface of the glassy carbon making diffusion of Sr towards the surface of glassy carbon an easier choice.The National Research Foundation, South Africa and the TWAS-DFG Co-operation Programme.http://www.journals.elsevier.com/vacuumhj2021Physic

Evaluation of diffusion parameters and phase formation between tungsten films and glassy carbon

Thin films of tungsten (W) were deposited on glassy carbon (C) substrates using a magnetron sputtering system. The as-deposited samples were annealed isothermally under vacuum at temperatures ranging from 673 to 1273 K. The structural changes due to thermal annealing were monitored by Rutherford backscattering spectrometry (RBS) and grazing incidence X-ray diffraction (GIXRD). RUMP software was used to simulate the RBS spectra. The thickness of W thin films deposited, atomic composition of deposited layer and the intermixed layer growth were deduced from the RUMP simulation results. The GIXRD analysis showed that carbide formation was first observed at annealing temperature of 1173 K. The kinetics of the solid-state interaction was found to be diffusion controlled at the interface between W and C. The activation energy for the diffusion of C in W was estimated as 2.23 eV. The XRD results showed that the average crystallite size of the as-deposited W film was 9.77 nm. It increased with annealing temperature up to 18.05 nm at 1173 K. The first carbide phase observed was W2C in the sample annealed at 1173 K, while WC was the dominant carbide phase at 1273 K. The stability of W/C system under heat treatments below 1073 K suggests that this system has a promising application for long-term structural integrity of dry cask storage devices.http://www.journals.elsevier.com/vacuumhj2021Physic

Investigating the effect of heat treatment on the diffusion behaviour of xenon implanted in glassy carbon

The effect of sequential isochronal annealing on the diffusion behavior of implanted xenon in glassy carbon is reported. Glassy carbon substrates were implanted with 200 keV xenon ions to a fluence of 1 × 1016Xe+cm−2. The sample was annealed in vacuum at temperatures ranging from 300 °C to 1000 °C for 5 h in steps of 100 °C. The RBS depth profiles obtained at temperatures above 800 °C showed that some diffusion occurred. The broadening of the peaks was not accompanied with a loss of the implanted Xe. Microstructural changes in the glassy carbon substrate due to Xe bombardment and annealing were monitored using Raman spectroscopy. The Raman spectrum obtained after xenon bombardment showed that the glassy carbon substrate became amorphized. However, a slight recovery of the glassy carbon structure was noticed after heat treatment. The SEM micrographs of the glassy carbon substrate showed an increase in the surface roughness of the glassy carbon substrate after implantation. The increase in the roughness of the glassy carbon substrate was attributed to the sputtering of the loosely bonded carbon atoms along the polishing marks after implantation and annealing.MYA Ismail, acknowledges the financial support by the University of Pretoria (South Africa) in terms of the UP postgraduate bursary and by the Ministry of Higher Education, the University of Zalingei (Sudan).http://www.journals.elsevier.com/vacuumhj2019Physic