热解炭的化学气相沉积机理和组织形貌

STUDY ON MACHANISM AND MICROSTRUCTURE OF PYROLYTIC CARBON PREPARED BY CHEMICAL VAPOUR DEPOSITION

以石油液化气作为沉积气体,在900～1300℃温度内研究热解炭在炭纤维上的沉积机理及组织形貌。研究发现:热解炭在纤维表面上通过形核、长大,大晶粒吞并小晶粒的过程,形成宏观上均匀平整而微观上呈球状突起的表面形貌。热解炭以层状微晶(主导)和球状微晶(辅助)两种模式同时生长,最终得到层状结构。在微观上热解炭由若干个的炭层组成,每一层的炭层内含有若干小的并与微晶尺寸相当的亚层。热解炭中的微晶排列不规整,层状和球状微晶均可通过位置的移动调整和脱氢来优化结构。

The formation mechanism and microstructure of pyrolytic carbons were investigated at 900～1 300 ℃with a kind of liquified petroleum gas as carbon resource. The gas flow rate was 0.5～1.5 m3/h. The results showed that the pyrolytic carbon was deposited on the carbon fibers via the following steps: formation of nucleus, growth of nucleus and annexation of grains to form convex-sphere-shaped surface. The pyrolytic carbon grows in pattern of laminated (dominant) and spherical (subordinate) crystallite, and finally results in multilayer structure. The pyrolytic carbon consists of several thick carbon layers and each layer consists of numerous sublayers. It is believed that the laminated structure of pyrolytic carbon results from the net plane molecules, of which benzenering structure is the initial precursor. The crystallites are present in the pyrolytic carbon in a disorder way, and its structures could be adjusted by migration, arrangement and dehydrogenation of carbon atoms.