The carbothermal reduction of MgO and Al2O3 in argon flow at low pressure allows to lower the onset temperature of metal vapor formation. Thermodynamic calculations indicate that metal formation begins at 1400 and 1700 K for a primary vacuum (1000 Pa), respectively, for Mg and Al. In the experimental section, concentrated solar energy was used for the process heating in order to favor energy savings. The products of the reaction between MgO or Al2O3 and 2 varieties of carbon (graphite, carbon black) in flowing argon atmosphere at a total pressure of around 1000 to 1600 Pa were studied using X-ray diffraction, and microstructure observations revealed the formation of metallic nanopowders with some by-products. Metallic conversions close to 45 wt% and 52 wt%, respectively, for Mg and Al, were obtained. The low conversion yield of the carbothermal reduction of MgO can be attributed to a backward reaction reforming MgO powder and to a sintering process between oxide particles at high temperature. Aluminum production challenge is to avoid formation of undesired by-products: Al2O, Al4C3 and Al-oxycarbides. Advantages and weaknesses of the used process are described and some improvements are proposed to increase metallic yields

2nd International Summer School on Nuclear Glass Wasteform - Structure, Properties and Long-Term Behavior (SumGLASS), FRANCE, SEP 23-27, 2013International audienceDispersions of undissolved palladium or ruthenium in nuclear glass can affect the glass flow during the vitrification process. As a consequence, one of the major challenges in nuclear glass elaboration is to understand and control the rheological behavior of glass melts. In this context, this work aims at describing accurately the rheological behavior of glass melts containing platinum group metals to better model the thermal hydraulics in vitrification process. A Searle viscometer has been used to characterize the non-Newtonian behavior of nuclear glass melt containing these noble metals versus temperature and shear rate. Obtained data have been compared to different reference models (Bingham, Ostwald ... ) in order to find the appropriate relation describing rheological behavior of nuclear glass melts. The specific role of low shear rates on viscosity measurements has been highlighted. Finally, another investigation under a constant low shear rate has been performed at high temperature during a few hours with the view to clarify this role and the associated physical phenomenon