Dispersion behaviour of laser-synthesized silicon carbide nanopowders in ethanol for electrophoretic infiltration

SiC nanopowders of 30 nm in diameter were successfully synthesized by laser-pyrolysis with high production rate (1.7 kg/h) and high quantity (>2 kg). The as-synthesized nanopowders were heat-treated in order to slightly oxidize the surface. It was shown that the heat-treatment does not modify structural properties or morphology but modifies the surface chemistry. Ethanolic suspensions with polyethylenimine (PEI) as dispersant were prepared from the heat-treated powders. The suspensions properties were characterized in terms of rheology, zeta potential and size distribution before and after operational pH adjustment with hydrochloric acid (HCl 1 M) or acetic acid (CH3COOH). High concentrated suspensions (28 wt%) with low viscosity were obtained after pH adjustment with CH3COOH. Electrophoretic infiltrations of carbon preforms carried out with these suspensions lead to a high quality infiltration of the inter-tows area as well as of the intra-tows area, some tows being completely filled with the nanopowders.