SiC/Si composites elaboration by capillary infiltration of molten silicon
Résumé
Infiltration of molten metal into ceramic performs without external pressure is a promising fabrication method for metal-matrix composites. Thus, this research is focused on the kinetic of capillary infiltration in the processing of Si/SiC composites. The calculation of the infiltration kinetics for a liquid in a porous material is possible by applying the modified-Washburn equation which involves the effective diameter of the pores. This equation implies a K value depending on the wetting angle, the density, the viscosity and the surface tension of the liquid at a given temperature. In this study, the main aim was to measure the K Si value of molten silicon infiltration into porous SiC at 1500°C. On this way, consolidated β-SiC powder compacts were prepared for infiltration experiments. The effects of the SiC particles presintering on the pore size were examined as they can affect molten silicon infiltration. So, the monitoring of the mass increase during hexadecane rise was used to determine the effective diameter of the pores. It was evidenced that an increase of 15.5% of the initial effective diameter occurs. Consequently, a corresponding correction has to be applied to the initial effective diameter of the silicon-infiltrated compacts. Infiltrations of pure molten silicon into SiC compacts were successfully carried out at 1500°C under high vacuum (5.10-3 mbar) and the average value of K Si was found equal to (5.8±0.4)×10-6 cm 5 .s.g-2. The effect of molten silicon rise on the porosity was also considered.
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