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Fabrication, microstructures and properties of SiCf/SiC composites prepared with two kinds of SiC fibers as reinforcements
New Carbon Materials ( IF 5.7 ) Pub Date : 2019-07-11 , DOI: 10.1016/s1872-5805(19)60010-7
Hong-lei Wang , Xin-gui Zhou , Shu-ming Peng , Hai-bin Zhang , Xiao-song Zhou

Three-dimensional (3D) SiC/SiCf composites were fabricated by a polymer impregnation and pyrolysis (PIP) method using 3D four directional braided preforms from two kinds of SiC fibers as the reinforcements and liquid polycarbosilane as the SiC precursor. Both kinds of SiC fibers were prepared from the same precursor and process but with different heat treatment temperatures. The one prepared at a higher temperature (No.1) had a higher crystallinity than the another one (No.2). A thin pyrolytic carbon (PyC) interlayer was coated on the preforms by a methane CVD method before impregnation. Their microstructures and mechanical properties were investigated by TEM, SEM, Raman spectroscopy and mechanical tests. Results showed that both had a polycrystalline structure with grain sizes of 8-15 nm. Fiber pullout was seen from the fracture cross-section of the composites after a bending test, indicating pseudo-ductile fracture behavior. The composite using No.1 SiC fibers had an average flexural strength, elastic modulus and fracture toughness of 955.0±42.8 MPa, 110.3±1.7 GPa and 28.5±2.8 MPa·m1/2, respectively, which are superior to those of the material formed using No.2 SiC fibers. This was ascribed to the high modulus and excellent thermal resistance of the stoichiometric No.1 SiC fibers. The PyC layer adhering to No.1 SiC fibers was ordered and smooth while that deposited on No.2 SiC fibers had a loose and granular microstructure, which was attributed to the different surface chemistries of the two types of SiC fibers.



中文翻译:

两种SiC纤维增强的SiC f / SiC复合材料的制备,微观结构和性能

三维(3D)SiC / SiC f通过聚合物浸渍和热解(PIP)方法,使用两种SiC纤维作为增强材料,液态聚碳硅烷作为SiC前驱体,使用3D四向编织预成型坯制造复合材料。两种SiC纤维均由相同的前体和工艺制备,但热处理温度不同。一种在较高温度(1号)下制备的结晶度比另一种(2号)高。在浸渍之前,通过甲烷CVD方法将薄的热解碳(PyC)中间层涂覆在预成型件上。通过TEM,SEM,拉曼光谱和力学测试研究了它们的微观结构和力学性能。结果显示两者均具有晶粒大小为8-15nm的多晶结构。弯曲试验后,从复合材料的断裂横截面观察到纤维拉出,表明假韧性断裂行为。采用1号SiC纤维的复合材料的平均弯曲强度,弹性模量和断裂韧性分别为955.0±42.8 MPa,110.3±1.7 GPa和28.5±2.8 MPa·m。分别为1/2,优于使用2号SiC纤维形成的材料。这归因于化学计量的1号SiC纤维的高模量和出色的耐热性。附着在1号SiC纤维上的PyC层是有序且光滑的,而沉积在2号SiC纤维上的PyC层则具有疏松的颗粒状微观结构,这归因于两种类型SiC纤维的表面化学性质不同。

更新日期:2019-07-11
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