Constant current electrophoretic infiltration deposition of fiber-reinforced ceramic composites

Modified electrophoretic infiltration deposition (EPID) under constant current conditions is used to fabricate non-conductive-fiber-reinforced composites from an ethanol suspension. Particles are infiltrated through a fiber preform by an electric field and are deposited on the front of the electrode and "backfill" through the fiber preform. A uniform morphology is achieved at the optimum deposition rate. The constant current EPID process is modeled as capillary infiltration electrophoresis. Particles "stream" the fiber preform due to the repulsive interaction between the fiber filaments and the particles as both have the same-sign surface charge. Electro-osmotic flow makes no contribution to deposit yield as the net flow across a closed capillary cross section is zero. Hamaker's law is extended to electrophoretic infiltration; however, the total deposit yield is controlled by particle electrophoresis outside the capillaries due to the much lower electric field in the suspension. The deposit thickness increases linearly with time under optimum current conditions. Too high a deposition rate promotes air entrapment in the depositing green body.