Reactive infiltration of silicon melt through microporous amorphous carbonpreforms

The kinetics of unidirectional capillary infiltration of silicon melt into microporous carbon preforms has been investigated as a function of the pore morphology and melt temperature. The infiltrated specimens showed alternat ing bands of dark and bright regions, which corresponded to the unreacted f ree carbon and free silicon regions, respectively. The decrease in the infi ltration front velocity for increasing infiltration distances is in qualita tive agreement with the closed-form solution of capillarity-driven fluid fl ow through constant-cross-section cylindrical pores. However, drastic chang es in the thermal response and infiltration front morphologies were observe d for minute differences in the preform's microstructure. This suggests the need for a dynamic percolation model that would account for the exothermic nature of the silicon-carbon chemical reaction and the associated pore-clo sing phenomenon.