基体炭对反应熔渗法制备的C/C-SiC复合材料性能的影响

Effect of matrix carbon on properties of C/C-SiC composites fabricated by RMI

以炭纤维针刺整体毡为预制体,分别采用化学气相渗透(chemical vapor infiltration,CVI)法、浸渍炭化(Impregnation and carbonization,I/C)法以及CVI与I/C相结合(CVI&I/C)的方法制备C/C坯体,坯体中的基体炭分别为热解炭,树脂炭,热解炭和树脂炭共存体,再通过反应熔渗硅(Reactive molten infiltration,RMI)获得C/C-SiC复合材料,对该材料的组织结构、力学性能和抗氧化性能进行研究。结果表明:C/C-SiC复合材料的相组成为SiC、C及残留Si相。I/C增密坯体的树脂炭更易与Si反应,因而形成的SiC量较多,CVI增密的坯体渗Si后SiC量较少而残留Si的量较多,材料的强度和韧性最低,分别为122.7 MPa和3.9 MPa.m1/2,但在1 200℃时其氧化性能优于用I/C增密的C/C坯体制备的材料的抗氧化性能。用CVI&I/C方法制备的C/C坯体,渗硅后的抗弯强度和断裂韧性最高,分别达到174.5 MPa和5.2 MPa.m1/2。

C/C-SiC composite was fabricated by reactive molten infiltrating（RMI） Si to C/C preforms with pyrolitic carbon,resin carbon,pyrolitic carbon and resin carbon which were prepared by chemical vapor infiltration（CVI）,resin impregnation and carbonization（I/C）,CVI and I/C（CVI I/C） respectively.The microstructure,mechanical properties and oxidation resistance of the composites were studied.The results show that RMI C/C-SiC composite consists of SiC,C and residual Si.The resin carbon in I/C preform is easier to reactive with infiltrating Si,leading to formation of more SiC,but pyrolytic carbon in CVI preform only reacts with infiltrating Si in its surface,resulting in more residual Si.Flexural strength and fracture toughness of the composite from CVI preform with pyrolytic carbon are the lowest,which are 122.7 MPa and 3.9 MPa？m1/2,respectively,but the oxidation resistance of the composite from the CVI preform with pyrolytic carbon is better than that of the composite from the I/C perform.The flexural strength and fracture toughness of the composite from CVIIC preform with pyrolytic carbon and resin carbon are the highest,which are 174.5 MPa and 5.2 MPa？m1/2,respectively.