A silicon carbide green body, additively manufactured via binder jetting, with additional carbon content and trace amount of B 4 C, was subsequently infiltrated by liquid silicon to produce a Si/SiC composite. The resulting microstructure, analyzed by means of high-resolution scanning and transmission electron microscopies, showed there exist five main phases: primary α-SiC particles, secondary α-SiC fronts, excess carbon pools, residual silicon and ternary Si-B-C phase. The secondary SiC formation reaction involves diffusion of carbon towards liquid silicon through the newly formed SiC layer, such that a region of non-stoichiometric silicon-rich hybrid α/β-SiC nanoparticles encompass the silicon/carbon interfaces. As these nanoparticles continue to grow, they eventually impinge on a primary SiC particle, assume its spatial orientation by realigning themselves, and transform into the α-SiC polymorph. Nano-indentation experiments confirmed primary SiC particles and their secondary SiC growth fronts share not only their crystal structure, but also their hardness, found to be approximately 47 GPa.
Eshed et al. (Sun,) studied this question.