Fabrication of fibre reinforced green bodies by electrophoretic deposition of silicon powder from aqueous suspensions

Fine silicon powders with a mean particle size of 0.5 μm were used to prepare aqueous suspensions for electrophoretic deposition (EPD). A cellulose film membrane was proved to be a cost-efficient alternative material to the dialysis hoses with excellent properties for the EPD-process. Several organic additives were tested to stabilise the suspension against sedimentation effects, to increase the electrophoretic mobility of particles and to optimise the mechanical properties of the dried green bodies. Mainly the electrokinetic sonic analysis (ESA) was used to characterise the influence of the additives and several parameters like solids content and ionic strength on the thickness of the electrical double layer. A computer-controlled and monitored EPD led to a dense and homogeneous packing of the powder and contributes to the understanding of deposition mechanisms. Even severe machining of the dried green bodies was possible. Using the planetary milled silicon powder the small spaces between the carbon (C-) or silicon carbide (SiC-) monofilaments of the fibre fabrics were infiltrated homogeneously by the silicon particles.