The Study On Fabrication Of 2D C_f/SiC Composites By Silicon Infiltration

The carbon fiber-reinforced silicon carbide matrix composites(Cr/SiC)have some superior properties,such as low density,high thermal conductivity,high strength,high fracture toughness,low thermal expansion coefficient,excellent friction and wear characteristics,excellent oxidation resistance,and so on.Thus,they have a good extensive application prospect.Some techniques are available for manufacture of Cf/SiC composites.And the liquid/gas silicon infiltration(LSI/GSI)is the best choice with lowest cost.Therefore,the C/C composite was prepared by stacking plain weave carbon cloths,and the optimum preparation conditions were studied by LSI method in the dissertation.This study mainly focused on the following aspects:the effect of the dose of silicon powder,the infiltration temperature,the infiltration time and the preform density on the mechanical properties of Cf/SiC composites,the optimum preparation conditions of Cf/SiC composites by liquid silicon infiltration.And the optimization of C content in C/C preform to improve the oxidation resistance of Cf/SiC composites.The C/C composite was prepared by stacking plain weave carbon cloths.In addition,the influences of liquid or gas silicon infiltration,silicon powder content,temperature of silicon infiltration and holding time of silicon infiltration on the preparation of Cf/SiC composites were also discussed.The results manifested that the composite has a better performance when the mass of silicon powder is 1.5 times greater than that of C/C composite,the temperature of silicon infiltration is 1550 ? and the holding time of silicon infiltration is 3 h.And the flexure strength and density of the Cf/SiC composites are 128 MPa and 2.15 g/cm3,respectively.The effect of the C/C preform's density of Cf/SiC composites was studied by imitating mathematic model and experimental process.It was found that the density of Cf/SiC composites and C/C preform are closely related,and the experimental results are basically consistent with the theoretical mathematical results.The theoretical mathematical results show that the density of Cf/SiC composites reached its maximum when the density of C/C preform was 0.96 g/cm3.The experimental results indicate that the flexural strength of composites decreased with the increase of C/C preform's density when the density of C/C preform is greater than 0.96g/cm3.And the composites have a better performance when the density of C/C preform is 0.98 g/cm3.While the flexure strength and density of the Cf/SiC composites are 134.51 MPa and 2.24 g/cm3,respectively.The oxidation resistance of Cf/SiC composites was studied by oxidation weight loss method.The results indicated that the oxidation weight loss rate of Cf/SiC composites,which was prepared by 1.02g/cm3 C/C preform,was 50%.The carbon area in the Cf/SiC composites led to the formation of large voids after oxidation,and it also led to the decreased of the mechanical properties.SiC added into phenolic resin,in the preparation of C/C preform,can reduce the content of carbon in the composites and microcrack,and improve the oxidation resistance of Cf/SiC composites.Moreover,The unidirectional porous SiC/Si ceramic was prepared by silicon infiltration and oxidation of a preform which winding by carbon fibers.