15 research outputs found
In-situ RBS studies of strontium implanted glassy carbon
The diffusion behaviour of strontium in glassy carbon was investigated using in-situ real time
Rutherford backscattering spectrometry. The sample was annealed in vacuum from room
temperature to 650 oC. Diffusion of the implanted strontium towards the bulk was observed
after annealing at temperatures ranging from 450 oC – 560 oC. The diffusion depth was
limited to the end-of-ion-range region where there were still some radiation damage present.No diffusion into the pristine glassy carbon was observed suggestion that diffusion of Sr in
glassy carbon can only occur in regions with radiation damage. Annealing the sample at
higher temperatures higher than 560 oC resulted in migration of the implanted strontium
towards the surface of the glassy carbon substrate. The amount of the accumulated strontium
at the surface increased as the annealing temperature is increased. The RBS spectra obtained
after annealing the sample isothermally at 650 oC for 2 hours show that there was no further
diffusion and accumulation of the strontium during this period.http://www.journals.elsevier.com/vacuum2017-04-30hb2017Physic
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
Diffusion of a mono-energetic implanted species with a Gaussian profile
The implanted profile in an isotropic substrate of a mono-energetic ion species is usually very near a Gaussian profile. An exact solution to the time-dependent Fick diffusion equation of an initially Gaussian profile is presented. This solution is a general one also covering the diffusion within the two limiting cases usually considered in solutions to the Fick equation, viz. a perfect sink at the surface and a perfectly reflecting surface plane at the surface. An analysis of the solutions for these two cases shows that at small diffusion times the main effect of annealing is a nearly symmetric broadening of the implanted profile. At the origin and for longer diffusion times the profile deviates significantly from Gaussian. A review is also given of past attempts to extract diffusion coefficients by fitting experimental data to approximate equations based on simplified initial profiles.http://www.elsevier.com/locate/nimb2018-09-01hj2018Physic
Effect of thermal annealing on SHI irradiated indium implanted glassy carbon
Please read abstract in the article.The National Research Foundation (NRF) of South Africa and the University of Pretoria.http://www.elsevier.com/locate/nimb2022-06-22hj2022Materials Science and Metallurgical EngineeringPhysic
Changes in the mechanical, structural and electrical properties of glassy carbon due to strontium and silver co-implantation and annealing
Please read abstract in the article.https://www.elsevier.com/locate/apsusc2022-09-22hj2022Physic
Structural modification of indium implanted glassy carbon by thermal annealing and SHI irradiation
Please read abstract in the article.The National Research Foundation (NRF) (grant no. 110363) of South Africahttp://www.journals.elsevier.com/vacuum2018-10-30hj2017Physic
Effects of implantation temperature and annealing on structural evolution and migration of Se into glassy carbon
Please read abstract in the article.The AST&D scholarship from the Tertiary Education Trust Fund (TETFund), Nigeria, and the Postgraduate Bursary from the University of Pretoria, South Africa.http://www.elsevier.com/locate/sssciehj2023Physic
Effect of sequential isochronal annealing on the structure and migration behaviour of selenium-ion implanted in glassy carbon
Please read abstract in the article.http://www.journals.elsevier.com/vacuumhj2021Physic
Scanning electron microscopy of the surfaces of ion implanted SiC
This paper gives a brief review of radiation damage caused by particle (ions and neutrons) bombardment
in SiC at different temperatures, and its annealing, with an expanded discussion on the effects occurring
on the surface. The surface effects were observed using SEM (scanning electron microscopy) with an inlens
detector and EBSD (electron backscatter diffraction). Two substrates were used, viz. single crystalline
6H-SiC wafers and polycrystalline SiC, where the majority of the crystallites were 3C-SiC. The surface
modification of the SiC samples by 360 keV ion bombardment was studied at temperatures below (i.e.
room temperature), just at (i.e. 350 C), or above (i.e. 600 C) the critical temperature for amorphization
of SiC. For bombardment at a temperature at about the critical temperature an extra step, viz. postbombardment
annealing, was needed to ascertain the microstructure of bombarded layer. Another aspect
investigated was the effect of annealing of samples with an ion bombardment-induced amorphous layer
on a 6H-SiC substrate. SEM could detect that this layer started to crystalize at 900 C. The resulting
topography exhibited a dependence on the ion species. EBSD showed that the crystallites forming in
the amorphized layer were 3C-SiC and not 6H-SiC as the substrate. The investigations also pointed out
the behaviour of the epitaxial regrowth of the amorphous layer from the 6H-SiC interface.http://www.elsevier.com/locate/nimb2016-07-31hb201
Modification of glassy carbon under strontium ion implantation
Glassy carbon is a disordered form of carbon with very high temperature resistance, high
hardness and strength and chemical stability even in extreme environments. Glassy carbon is also
unaffected by nearly all acids and cannot be graphitized even at very high temperature. Because
of these characteristics, there is a possibility that glassy carbon can replace copper, iron, titanium
alloys and other materials employed in making canisters used in nuclear waste storage.
The modification of glassy carbon due to strontium ions implantation and heat treatment is
reported. Glassy carbon (GC) samples were implanted with 200 keV strontium ions to a fluence
of 2×1016 ions/cm2 at room temperature.
Sequential isochronal annealing was carried out on the implanted samples at temperatures
ranging from 200 oC - 900 oC for one hour. The influence of ion implantation and annealing on
surface topography was examined by the scanning electron microscopy (SEM), while Raman
spectroscopy was used to monitor the corresponding structural changes induced in the glassy
carbon. The depth profiles of the implanted strontium before and after annealing were
determined using Rutherford Backscattering Spectroscopy (RBS). Compared to SRIM predictions the implanted strontium profiles was broader. After annealing at
300 oC, bulk and surface diffusion of the strontium atoms took place. Annealing at 400 oC- 700
oC not only resulted in further diffusion of strontium towards the surface, the diffusion was
accompanied with segregation of strontium on the surface of the glassy carbon substrate.
Evaporation of the strontium atoms was noticed when the sample was annealed at 800 oC and
900 oC respectively. These annealing temperatures are higher than the melting point of strontium
(~769 oC).
The Raman spectrum of the virgin glassy carbon shows the disorder (D) and graphitic (G) peaks
which characterize disordered carbon materials. Merging of these two peaks was observed when
the virgin sample was implanted with strontium ions. Merging of these peaks is due to damage
caused by the implantation of strontium. The Raman spectrum recorded after heat treatment
showed that only some of the damage due to implantation was annealed out. Annealing at
20000C for 5 hours resulted in a Raman spectrum very similar to that of virgin glassy carbon
indicating that the damage due to the ion implantation was annealed out.
SEM showed large differences in the surface topography of the polished glassy carbon surfaces
and those of as-implanted samples. Annealing did not significantly change the surface
microstructure of the implanted samples.Dissertation (MSc)--University of Pretoria, 2013.gm2014Physicsunrestricte