Numerical study of Gezon experiment

International audienceTo prepare the microgravity experiment of crystal growth by floating zone method, GEZON, numerical studies of hydrodynamics of the melt are carried out. Calculations of zone length and convection driven by surface-tension gradients are presented for germanium floating zone operating under microgravity conditions. Results of linear stability analysis show the instability of intense thermocapillarity convection needed to be damped by using a magnetic field; the critical magnetic induction is obtained. it is expected to grow a striation-free crystal with this magnetic fiel

On the detachment of Si ingots from SiO2 crucibles.

International audienceIn a directional solidification furnace, ingots of silicon are contained in a silica crucible covered with a silicon nitride (Si3N4) powder layer. During the crystallization of the ingot, the layer may suffer various behaviors. When properly applied, it can efficiently act as a mechanical shunt between the Si and the silica wall. However, filling of the crucible with silicon pieces can also scratch locally the layer, resulting in deleterious adhesion between ingot and crucible. The layer can also be too thin, or insufficiently pyrolyzed, so that the Si interacts with the silica crucible. An extended simulation is carried out; taking into account the thermo-elastic stresses induced by the difference in thermal expansion coefficients of the crucible and ingot materials that are attached On small areas. The model compares the remaining elastic energy to the adhesion energy between the silicon and the crucible, in order to predict the temperature at which the Si detaches from the crucible in case of sticking. Two configurations are compared in terms of amount or stresses and extent of the ingot volume likely to be impacted by dislocation generation. (C) 2013 Published by Elsevier B.V

Analysis of the unsteady segregation in crystal growth from a melt. Part I: Fluctuating interface velocity.

International audienc

Method for assembling carbon bodies through refractory brazing

La présente invention se rapporte à un procédé d'assemblage de pièces carbonées avec une brasure à base de carbure de silicium. Elle vise en outre les pièces assemblées selon un tel procédé

Reference microgravity measurements of liquid phase solute diffusivities in tin and aluminum based alloys

This paper presents results of the measurement of solute diffusivities in the Al Ni and Sn Bi In systems. These experiments were conducted in microgravity and may therefore be assigned as reference values. A dedicated facility, allowing to process four identical samples in parallel, was developed for the experiments under consideration. In addition, a rather thorough analysis of possible error sources in shear cell type experiments is carried out. Comparison with work carried out using magnetic fields to control convective flows, and with previous indirect measurements results is also provided. A coherent picture emerges from the overall agreement between various measurements, and our data can thus be considered as reference benchmarks for future experiments. Another conclusion of the present study is that the shear cell technique is well suited for the measurement of solute diffusivitie

Production of polycristalline silicon by natural sintering for photovoltaic applications

The invention relates to a silicon sintering process, with no external force added, which comprises positioning a silicon sample in a furnace and then heat-treating this sample at least at a certain temperature and with at least a partial pressure of oxidizing species in order to control the thickness of a silicon oxide layer on the surface thereof

Reference Microgravity Measurements of Liquid Phase Solute Diffusivities in Tin- and Aluminium-Based Alloys

This paper presents results of the measurement of solute diffusivities in the Al Ni and Sn Bi In systems. These experiments were conducted in microgravity and may therefore be assigned as reference values. A dedicated facility, which can be used for processing of four identical samples in parallel, was developed for the experiments under consideration. In addition, a rather thorough analysis of possible error sources in shear cell type experiments is carried out. Comparison with work carried out using magnetic fields to control convective flows, and with previous indirect measurements results, is also provided. A coherent picture emerges from the overall agreement between various measurements, and the data from the current work can thus be considered as reference benchmarks for future experiments. Another conclusion of the present study is that the shear cell technique is well suited for the measurement of solute diffusivitie