Study On Microstructures And Fine Structures Of The Carbon/Carbon Composites

During the compacting process of Carbon/Carbon materials, different structures will apper due to the change of parameters of deposition technics. Different structures result in different properties. Only by comprehending the classification, characteristic, properties and technical conditions, could we know the relationship among the structures, properties and technics. The process parameters can then be determined and controlled properly, after which we can get the stuctures and the relative properties needed.The present work had analyzed the microstructures and fine structures of pyrocarbon and carbon fiber in the C/C composites in detail by means of polarized light microscopy, XRD, SEM and HRTEM.The graphitization degree of several samples were analyzed by x-ray diffractions. With the graphitization temperature rises, the graphitization of cloth precursor C/C composites have been divided into three stages. Below 2600℃ and above 2800℃, the graphitization degree increases rapidly with the increase of temperature. While from 2600℃ and 2800℃, the graphitization degree changes little.The basic principles of polarized light microscopy observation were used for measuring the extinction angles (Ae). Pyrocarbon may be classified according to the extinction angles. Under the polarized light microscopy, the structures can be more rough with the increase of extinction angles. The main reason is that the rough laminar with higher graphitization degree have more complete layer planes and more anisotropic. The microstructures of carbon fibers in C/C composites had been analyzed with the fringe lattices of TEM. The structure of Dunlop sample was looked on as the exact graphic layer plane, the structures of Goodrich and cloth precursor C/C composites can be measured. In the cloth precursor C/C composites, which have the same compacting technics, the layer spaces will decrease with the increase of graphitization degrees. The fine structures of pyrocarbons have been analyzed with TEM and SAED, the relative speed of pyrogenation, nucleation and the growth decides the structure of pyrocarbons.The orientation angles (OA) were measured by SAED.