SiC_f/SiC Composites Fabricated By Electrophoretic Deposition With PIP

With low density,high specific strength and modulus,high temperature resistance,corrosion resistance,low neutron radiation and many other excellent properties,SiC_f/SiC composites are widely applied in areas such as aerospace and nuclear fusion reactor.The processing routes combined electrophoretic deposition and PIP for fabricating SiC_f/SiC are able to reduce production cycle,improve composites’density and thermal conductivity greatly without any sintering additives,which are recognized as promising routes for the fabrication of fusion SiC_f/SiC composites and concerned by researchers from all over the world.This article is mainly divided into three parts.The first part is the SiC_f/SiC composites’performance comparation between EPD+PIP and pure PIP.It is resulted that SiC_f/SiC composites produced by EPD with PIP could save 1/10 fabrication cycles,enhance 10%density and increase thermal conductivity over doubled.Through EPD,the density and thermal conductivity of SiC_f/SiC composites were considerably improved.The second part is about the influence of EPD on SiC fibers.The experiment used SiC fibers as EPD simulation,results showed that with EPD time extended,SiC fibers’surface defects grew,mechanical properties decreased.Therefore,it is possible that SiC fibers would be corroded or damaged during EPD.The third part is the influence of suspension parameters（pH and SiC solid content）and EPD parameters（EPD time and current density）on SiC_f/SiC green bodies and SiC_f/SiC composites.With suspension pH value increased,SiC solid content enhanced,EPD time extended and current density rised,the weight gain rate of SiC fabrics first grew then fell.pH=10.5,60 wt.%SiC suspension,15min EPD time and 5 mA/cm² current density fabricated largest weight gain rate SiC_f/SiC green bodies respectively.While the density of SiC_f/SiC composites is usually linear with the weight gain rate of SiC_f/SiC green bodies,i.e.the higher the weight gain rate is,the higher the density of composite materials are.At pH=10.5,55 wt.%SiC suspension,10min EPD time,5 mA/cm² current density,we obtained largest SiC_f/SiC composites density,2.39 g/cm³.Mechanical properties of SiC_f/SiC composites are inversely proportional with weight gain rate of SiC_f/SiC green bodies because of matrix brittleness.Best mechanical properties were achieved at pH=9,55 wt.%SiC suspension,5 min and5 mA/cm²,whose flexural strength was 681.2 MPa,fracture toughness was 17.7MPa·m^1/2.Due to the affection of density,crystallinity and porosity,thermal conductivity of SiC_f/SiC composites are determined by both the weight gain rate of green bodies and the porosity of composites.The largest thermal conductivity was attained at pH=9,55wt.%SiC suspension,10 min and 4.5 mA/cm² EPD routes.Thermal conductivity at 25℃,200℃and 400℃is 5.296 W/m·K,6.216 W/m·K,6.614 W/m·K respectively.