3D observations of room temperature capillary infiltration mechanism in SiC compacts

Abstract

The melt infiltration of a liquid metal is a successful method for densifying metal and ceramic matrix composites (CMC). The reduction of residual porosity of silicon carbide composites by infiltration of molten silicon into the matrix allows to reach interesting mechanical properties. However, fluid progression within the pore network of the granular matrix is a complex phenomenon, driven by physical and thermomechanical mechanisms that are not yet fully understood. This publication focuses on the capillary impregnation at room temperature and highlights important parameters related to the physical aspect of the process. Two different model fluids (n-hexadecane and exo-dicyclopentadiene) were used to reproduce the behaviour of molten silicon alloy. During the infiltration, the monitoring of the infiltrated liquid weight, along with the image acquisition, was used to compare the infiltration difference between several types of samples. An innovative way to interrupt and fix liquid inside samples, based on rapid polymerization, was investigated during capillary rise experiments. The correlation between 2D observations and 3D volumes obtained by tomography outlines the existence of two different flow fronts, the surface flow front (SFF) which often have a flat shape, and a second inside the sample, the volume flow front (VFF), which shows a paraboloid shape.