Cao Jingjing, Zhao Wenwu, Gao Shuzhen
College of Mechanical and Equipment Engineering, Hebei University of Engineering, Handan 056038, China.
Materials (Basel). 2018 Jun 15;11(6):1017. doi: 10.3390/ma11061017.
Carbon fibers in situ prepared during the hot-pressed sintering in a vacuum is termed in situ transformed polyacrylonitrile-based (PAN-based) carbon fibers, and the fibrous precursors are the pre-oxidized PAN fibers. The properties and structure of in situ transformed PAN-based carbon fibers are investigated by Nano indenter, SEM, TEM, XRD, and Raman. The results showed that the microstructure of the fiber surface layer was compact, while the core was loose, with evenly-appearing microvoids. The elastic modulus and nanohardness of the fiber surface layer (303.87 GPa and 14.82 GPa) were much higher than that of the core (16.57 GPa and 1.54 GPa), and its interlayer spacing d002 and crystallinity were about 0.347 nm and 0.97 respectively. It was found that the preferred orientation of the surface carbon layers with ordered carbon atomic arrangement tended to be parallel to the fiber axis, whereas the fiber core in the amorphous region exhibited a random texture and the carbon atomic arrangement was in a disordered state. It indicates that the in situ transformed PAN-based carbon fibers possess significantly turbostratic structure and anisotropy.
在真空热压烧结过程中原位制备的碳纤维被称为原位转化聚丙烯腈基（PAN基）碳纤维，其纤维前驱体为预氧化的PAN纤维。采用纳米压痕仪、扫描电子显微镜（SEM）、透射电子显微镜（TEM）、X射线衍射仪（XRD）和拉曼光谱对原位转化PAN基碳纤维的性能和结构进行了研究。结果表明，纤维表层微观结构致密，而芯部疏松，存在均匀分布的微孔。纤维表层的弹性模量和纳米硬度（303.87 GPa和14.82 GPa）远高于芯部（16.57 GPa和1.54 GPa），其层间距d002和结晶度分别约为0.347 nm和0.97。研究发现，具有有序碳原子排列的表面碳层的择优取向倾向于平行于纤维轴，而无定形区域的纤维芯呈现随机织构，碳原子排列处于无序状态。这表明原位转化PAN基碳纤维具有明显的乱层结构和各向异性。
