【摘要】 采用化学气相渗透工艺在Nextel 720纤维表面制备PyC和PyC/SiC两种涂层,然后以正硅酸乙酯和异丙醇铝作为先驱体,以先驱体浸渗热解法制备三维Nextel 720纤维增韧莫来石陶瓷基复合材料,比较分析了两种涂层复合材料的力学性能和断裂模式。结果表明:具预先涂覆PyC的复合材料中纤维与基体直接接触,发生烧结形成强结合界面,复合材料脆性断裂,三点抗弯强度仅56 MPa。PyC/Sic涂层则演化为间隙/Sic复合界面层,Sic成为阻滞纤维与基体接触的阻挡层,间隙保证了纤维拔出,复合材料韧性断裂且三点抗弯强度高达267.2 MPa。更多还原

【Abstract】 PyC and PyC/SiC interface layers were coated on the surface of Nextel 720 fibers by chemical vapor infiltration. The 3D Nextel 720/mullite composites were fabricated by precursor infiltration and pyrolysis using TEOS- AIP as precursor. The mechanical properties and rupture model of the 3D Nextel 720/mullite composites with PyC and PyC/SiC coating were analyzed. Results indicate that the rupture model is brittle rupture for the 3D Nextel 720/mullite composites with PyC coating, and the flexural strength is 56 MPa only, due to the forming of strong bonding interfaces between fibers and matrix in the 3D Nextel 720/mullite composites during the pyrolysis process. But gap/SiC composite interfaces resulted from PyC/SiC interface layers lead to a weak bonding between fibers and matrix. As an obstruct layer, SiC prevents fibers from contacting to matrix, and the gap results in the pulling-out of fibers. The rupture model of the 3D Nextel 720/mullite composites with PyC/SiC coating is toughness failure and the flexural strength reaches to 267.2 MPa.更多还原