Influence Of Radiation-induced Defects Research Articles

In-situ studies on the mechanical properties of He ion irradiated nanotwinned Ag

Recent studies show that twin boundaries are effective defect sinks in eliminating radiation-induced defects. However, the influence of radiation-induced defects on the mechanical behavior of nanotwinned (NT) materials is less well understood. In this study, we investigate the mechanical properties of He ion irradiated NT Ag. In-situ micropillar compression tests show that deformation induces prominent detwinning in as-deposited NT Ag, whereas He ion irradiation alleviates detwinning during deformation of NT Ag. The radiation hardening mechanism and the influence of He bubbles on the deformation behavior of NT Ag are discussed.

Radiation embrittlement modelling in multi-scale approach to brittle fracture of RPV steels

The purpose of the present article is to develop a multi-scale brittle fracture modelling for irradiated RPV materials. For this development, applicability of local brittle fracture criteria for radiation embrittlement modelling is analysed through comparison of the predicted and test results on radiation embrittlement of RPV steels in terms of ductile-to-brittle transition temperature and fracture toughness. The influence of radiation-induced defects on the processes of cleavage microcrack nucleation and propagation is clarified. The physical-and-mechanical models of the effect of irradiation-induced defects on cleavage microcrack nucleation are developed on the basis of dislocation and brittle fracture theories. Stress-and-strain controlled fracture criterion is developed that allows the adequate prediction of radiation embrittlement by various mechanisms. The differences and commonalities are revealed in the nature of material embrittlement due to cold work and neutron irradiation. The mechanism is explained of significant recovery of fracture resistance properties with simultaneous increase of fraction of intercrystalline fracture after post-irradiation annealing. Engineering approach for prediction of the temperature dependence of fracture toughness as a function of neutron fluence is justified.

Influence of radiation defects on the energy gap in YBa 2Cu 3O 7−δ as measured with the help of Andreev reflection

The influence of radiation-induced defects on the energy gap Δ in YBa 2Cu 3O 7−δ, as measured with the help of Andreev reflection, was investigated. It was found that Δ decreases with irradiation fluence F increasing at a much lower rate than T c. It is shown that δ remains different from zero for F>F c, where F c is the fluence corresponding to T c=0. The results are interpreted as a transition of a Bose condensate of Cooper pairs into a localized state.

A study of the charging and dissociation of SiO 2 Surfaces by AES

AES is used to determine the initial spectrum of a vacuum-broken SiO 2 surface and to follow its dissociation under the electron beam probe. Both Auger peaks heights and energies are affected by the irradiation. The change in stoichiometry is accompanied by a decrease of the surface charge by 5–8 V. The relation between stoichiometry and charge is explained by the influence of radiation-induced defects on secondary electron emission. The reduction of SiO 2 is characterized in terms of irradiation dose, dissociation cross-section and electron impact efficiency. Resistance to radiation damage is increased by surface carbon contamination. The chemical contribution to the Auger peak energy can be distinguished from the charging effect leading to a shift between element and compound of 12 eV for the silicon peak.