Effects of electronic and nuclear interactions in SiC
Introduction
The aim of this paper is to study the structural evolution of silicon carbide under ion irradiation. Numerous studies have been already performed with low energy ions in order to observe the nuclear interaction effects on single 6H–SiC crystals. They have shown a rapid amorphization during irradiation at room temperature (RT) [1]. On the other hand, only few studies concern the electronic interaction effects. They indicate a very low disordering of virgin samples under high energy ion irradiation at RT and a defects recovery of predamaged samples under 827 MeV Pb irradiations [2].
Beside the peculiar properties of SiC, its elaboration as a nanostructured ceramic (NSC) is also worth studying because of the high grain boundaries density that is expected to provide an efficient source of traps for irradiation induced defects [3], but the enhancement of the behaviour under irradiation has still to be proven.
The present work is focussed on the structural evolution of NSC–SiC samples under irradiation at RT with 95 MeV Xe delivered by the IRRSUD line of the GANIL facility. These ions are similar to fission products and allow the observation of the combined electronic and nuclear interactions with matter. To study separately the nuclear and the electronic interactions effects, the samples were irradiated with 4 MeV Au ions on the ARAMIS accelerator of the CSNSM and 910 MeV Xe ions delivered by the GANIL.
Section snippets
Experimental
3C–SiC nanopowders with an average grain size of 10 nm were synthesized by the laser pyrolysis technique [4], [5], which allows an accurate control of the granulometry and stoichiometry. Using these nanopowders, two ceramic samples were subsequently prepared by hot isostatic pressing (HIP) without sintering additives. The densification of the final NSC–SiC pellet is close to 92% with a grain size after sintering around 36 nm.
The first pellet was irradiated at RT with 95 MeV Xe ions and a fluence
Results and discussion
The results obtained from XRD on the nanostructured samples before irradiation for a probed depth of 2.5 μm (Fig. 1) clearly show the cubic phase of SiC. The slight contribution at 2θ = 34.2° could be attributed to the hexagonal phase. This contribution is in fact the consequence of stacking faults in some crystallites of the starting nanopowders [6]. Fig. 1 also exhibits the typical peak broadening coming from the nanometric size of the crystallites [7], [8].
The samples were irradiated with 95 MeV
Conclusion
Nanostructured 3C–SiC samples were irradiated at RT with 95 MeV Xe ions and no large scale amorphization could be detected in spite of a number of dpa exceeding the amorphization threshold found in literature with low energy ions. However, a complete sample amorphization was noticed after irradiation at RT with low energy ions (4 MeV Au), where the nuclear interactions are dominant. The absence of amorphization under 95 MeV Xe ions irradiation is assumed to be the consequence of the competing
Acknowledgements
The authors thank the DEN/DMN/SRMA/LTMEX Laboratory for the pellets sintering.
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