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[en] The Zr-based bulk metallic glasses, developed since the late 1980's, have very interesting mechanical properties, which can be considered for many applications including working under oxidizing atmosphere conditions at high temperatures. It is therefore interesting to study their oxidation resistance and to characterize the oxide scale formed on alloys surface. The fundamental objective of this thesis is to enhance the understanding of the role of various thermodynamic and chemistry parameters on the oxidation behaviour of the Zr-based bulk metallic glasses at high temperature under dry air, to determine the residual stresses in the oxide layer, in comparison with their crystalline alloys with the same chemical composition after an annealing treatment. The oxidation kinetics of these glasses and the crystalline structure of oxide scale ZrO_2 depend on the temperature and the oxidation duration: for short periods of oxidation or at a temperature below Tg, the kinetics follows a parabolic law, whereas, if the sample is oxidized at T ≥ Tg, the kinetics can be divided into two parts. The crystalline counterparts are oxidized by a parabolic rule whatever the temperature; for long oxidation duration at a temperature close to Tg, the kinetics becomes more complex because of the crystallisation of the glasses during the oxidation tests. Also the crystalline structure of the oxide layers depends on the oxidation temperature: the oxide layer consists only in tetragonal Zirconia at T ≤ Tg, while monoclinic Zirconia was formed at higher temperature. The mechanism of the formation of the oxide scale is due to both the interior diffusion of Oxygen ions and the external diffusion of Zirconium ions. However the diffusion of Zirconium ions slows gradually during the crystallisation process of the glass matrix. When the crystallisation is completed, the formation of Zirconia is controlled by only the internal diffusion of oxygen ions. The corresponding residual stresses existing in the oxide layer are compressive, both for the metallic glass and counterpart, and they increase linearly with the thickness of the oxide layer. The growth and residual stresses are strongly influenced by the phase transition of Zirconia during oxidation process. (author)

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[en] The temperature measurement branch is a subsystem in a thermo-hydraulic sodium testing loop. It is very important to check and guarantee the safe operation of the loop. Because the subsystem operates at 650 degree C, it is necessary to analyse the stress of the subsystem piping. The analysis is according to the criteria SDGJ6-78 completed with program PSDP. The analysis included is as follows: check the primary stress intensity; check the secondary stress intensity; check the range of the primary plus secondary stress intensity; check the peak stress intensity (using the stress multiplying factors); check the maximum pushing forces which act on the ends of the piping (considering the fixing and safety of equipment). The dynamic and creep analysis is not included in this analysis

[en] We have studied the interaction between dark energy and dark matter from the thermodynamical consideration. Assuming the interaction as stable fluctuations around equilibrium and using the logarithmic correction to entropy caused by the fluctuation, we have derived the physical expression of the interaction. We have tested the viability of our scenario on the interaction by confronting with cosmological observations. (authors)