Analysis and Control of nano molecular gathering texture in the mesophase pitch

采用高分辨率扫描电镜（hrsem）观察了中间相沥青基纤维经310℃纺丝、稳定、碳化、煅烧和石墨化后横向织构的发展情况。纺丝纤维的横截面表面显示出随机取向的球形或椭球状微畴，其长轴长约50nm。当温度达到500℃时，微畴的形状和取向基本保持不变，微畴呈现出带有一定曲率的片状结构。700℃以下的热处理，根据挥发性气体的演化，通过收缩诱导微畴的连接和取向，形成确定的畴。在微畴之间也观察到一些空洞。700℃热处理促进了微畴内碳平面的生长和层状堆积。在700 ~ 1500℃时，碳化纤维的横截面区域由于六边形较小而呈现出平缓的曲率。畴形…More基本上没有改变到石墨化。在2000℃以上石墨化过程中，由于石墨平面的生长，弯曲区域逐渐变直。用吡啶提取未纺纤维，观察其显微结构。在低倍率下，310℃下提取的纤维在宏观上表现出与炭化纤维相同的随机横向织构。提取的纺丝纤维中的微畴与石墨化纤维中观察到的微畴已经是直的并且取向相同，没有观察到曲率。另外两种纤维在300℃和340℃纺丝时分别呈现径向织构和洋葱状横向织构，表现出相同的纺丝和石墨化趋势。这一系列的观察表明，石墨化纤维中不溶性组分决定了微畴的形状、取向和排列。在纺丝过程中，溶质分数形成了中间相微畴的曲率，以遵循取向不溶分数的形状进行碳化。碳化后提取的原纺纤维的织构基本保持不变，但在不溶性微畴中出现了明亮的突起。经炭化处理后，提取的纺丝纤维形成了非常直的短畴边缘。经热处理后的纤维经提取后，其弯曲程度减小，说明可溶性组分在结构域生长中起连接作用。在微畴中以马刺形式观察到的碳层的堆叠基本上是沿着微畴形状和排列的较长轴方向进行的。少

Development of the transversal texture in the mesophase pitch-based as-spun at 310℃, stabilized, carbonized, calcined and graphitized fibers was examined using a high resolution scanning electron microscope (HR-SEM). The cross-sectional surface of the as-spun fiber showed randomly oriented microdomains of spherical or ellipsoidal shape with ca. 50nm long in their longer axis. Such shape and orientation of the microdomain stayed almost same up to 500℃, where the microdomain took a plate shapes with some curvatures. The heat-treatment up to 700℃ induced the connection and orientation of microdomains through the shrinkage according to the evolution of volatile gas, forming the definite domain. Some voids were also observed among the microdomains. The heat-treatment at 700℃ enhanced the growth of carbon planes and their layer stacking in the microdomain. The cross-sectional domain showed gentle curvatures in the carbonized fiber at 700℃ to 1500℃ owing to smaller hexagons. The domain shape … More was basically not changed up to graphitization. The curved domain became straight during graphitization up to 2000℃, owing to the growth of graphitic planes. The as-spun fiber was extracted with pyridine to observe its microtexture. The extracted as-spun fiber at 310℃ showed macroscopically the same random transversal texture at low magnification to that of the carbonized fiber. The microdomain in the extracted as-spun fiber was already straight and oriented in the same direction as that observed in the graphitized fiber, no curvature being observable. Two other fibers spun at 300 and 340℃ to show the radial and onion transverse textures, respectively, exhibited the same trend of as-spun and graphitized fibers. Such a series of observation suggests that the insoluble fraction frames the shape, orientation and arrangement of microdomains in the graphitized fiber. The solute fraction in the as-spun fiber formed the curvature of mesophase microdomain to be carbonized to follow the shape of the oriented insoluble fraction. The texture in the extracted as-spun fiber was maintained basically after the carbonization, although bright spurs appeared in the insoluble microdomain after the carbonization of extracted as-spun fiber. The carbonization of extracted as-spun fiber induced the very straight periphery of the shorter domain. Less bent was observable in the heat-treated fibers after extraction of as-spun fiber, suggesting the connecting roles of the soluble fraction in the growth of domain. The stacking of carbon layers observed as spurs in the microdomain is basically directed along the longer axis of the shape and alignment of microdomains. Less