Processing of carbon nanofiber reinforced silicon nitride matrix composites

This work presents a process optimization study for processing vapor grown carbon fibers and single walled carbon nanotubes into Si₃N₄ with the goal of developing advanced structural ceramic materials. Solid composite specimens were fabricated using a freeform fabrication technique called robocasting that uses high solids loading aqueous suspensions to fabricate near-net-shape-ceramic composite parts. Colloidal processing methods were used to manipulate the charging behavior between carbon nanofibers and silicon nitride particle surfaces in order to develop forty-five percent solids loading suspensions with a pseudoplastic theology that borders on dilatancy and is suitable for robocasting solid parts. Dispersion of nanofibers within each composite system was identified as was the starting dispersion of the nanofibers in the slurry.