LPVCS改性制备Cf/SiC复合材料及其耐高温性能

High Temperature Performance of Modified Cf/SiC Composites with LPVCS

摘要:

以液态聚碳硅烷(LPVCS)、聚碳硅烷(PCS)为先驱体,采用PIP工艺制备了连续碳纤维增强碳化硅(C_f/SiC)复合材料。LPVCS是一种新型先驱体,具有室温下为液态、浸渍效率高的优点,同时由LPVCS裂解得到的SiC基体具有能够与T300碳纤维形成合适界面力的优点。相比于全周期采用PCS浸渍制备的C_f/SiC复合材料,第一周期使用LPVCS浸渍,第二至八周期使用PCS浸渍,第八周期之后使用LPVCS浸渍制备的C_f/SiC复合材料具有更优异的力学性能,其三点弯曲强度由301MPa提高到442MPa,断裂韧性由11.2MPa.m_1/2提高到26.1MPa.m_1/2。力学性能提高的原因为两个方面,第一周期使用LPVCS浸渍得到了合适的界面结合强度,第八周期之后使用LPVCS浸渍提高了SiC基体的致密化程度。

Abstract:

Three dimensional and four directional carbon fiber reinforced SiC matrix (C_f/SiC) composites were fabricated by precursor infiltration and pyrolysis process with ameliorated interface and low porosity employing a new precursor, liquid polyvinylcarbosilane (LPVCS). LPVCS is a novel precursor with active Si-H and –CH=CH₂ groups with relatively high oxygen content (~7.3 wt.%). The mechanical properties improvement led by ameliorated interface and low porosity was reasearched. Samples with ameliorated interface and low porosity employing LPVCS showed better mechanical properties than those employing ploycarbpsilane (PCS). The flexural strength and fracture toughness of the C_f/SiC composites fabricated with PCS were 301 MPa and 11.2 MPa.m_1/2, respectively, whereas the equivalent values of the samples fabricated with ameliorated interface and low porosity were 442 MPa and 26.1 MPa.m_1/2, respectively. Employing LPVCS for the first infiltration and pyrolysis cycle formed suitable interface, employing PCS as precursor for the left cycles formed relatively low oxygen content matrix, then employing LPVCS for the last several cycles formed low porosity, this the main reason of mechanical properties improvement.