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On the determination of diffusion coefficients in two-component alloys and doped semiconductors: several implications concerning the International Space Station
Sánchez Meneses, O.; Ruiz Martí, Xavier; Pujalte, Mónica; Mercader Calvo, María Isabel; Batiste Boleda, Oriol; Gavaldà, Josefina
Universitat Politècnica de Catalunya. Departament de Física; Universitat Politècnica de Catalunya. DF - Dinàmica No Lineal de Fluids
The accurate determination of mass diffusion coefficients is a technologically relevant problem that has implications on the modelling and control of material processes such as crystal growth and casting. It is also important in the validation of different theories of atomic diffusion. The experimental determination of these coefficients, when there is a liquid phase, is difficult due to the unavoidable presence of buoyancy driven convection currents that enhance mass transport and disturb diffusion measurements. To minimize as much as possible these problems, long capillaries are used in order to confine the fluid and reduce the intensity of the convective motions. These measurements have also been done in reduced gravity environments, but the residual gravity may still be able to induce buoyancy driven convection motions. The aim of our work is to analyze the impact of low solutal Rayleigh number environments on the accuracy of the interdiffusion coefficient measurements using long capillaries. In the present study we deal with two liquid systems; photovoltaic silicon and Al-based liquid binary alloys at high temperature. We have numerically simulated two different experimental techniques used to determine the diffusion coefficients; the shear cell and the long capillary techniques. We also consider the effect of rotating the cylindrical cell along their axis as a mechanism to reduce axial convective transport even in Earth laboratories. Finally, we use typical accelerometric signals from the International Space Station (ISS) in the quasi-steady range of frequencies. The signals concentrate on typical station reboosts because the accelerometric level of the rest of potentially dangerous disturbances - dockings, undockings and Extra Vehicular Activities, EVAs - is considerably lower.
Peer Reviewed
Àrees temàtiques de la UPC::Física
Àrees temàtiques de la UPC::Enginyeria dels materials
Reduced gravity environments
Liquid metals
Diffusion coefficients
Numerical simulation
Microgravity conditions
Melted semiconductors
Liquid metals
Shear cell
Long capillaries
Submerged heater method
Dilute liquid-metals
Shear cell
Directional solidification
Microgravity environment
Multicrystalline silicon
Concentration profile
Ambients de microgravetat
Metalls líquids
Difusió (Física)

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