Micro- and nanostructure of the carbon matrix of infiltrated carbon fiber felts Original Research Article

The structural properties of carbon/carbon-composites fabricated by chemical vapor infiltration (CVI) were studied by polarized light microscopy (PLM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) on a micrometer and nanometer scale. The types of carbon bonds were estimated by electron-energy-loss spectroscopy (EELS). Using a methane/hydrogen gas mixture at a temperature of 1100°C two different methane partial pressures were applied. The carbon fibers are surrounded by ring-shaped layers with different optical reflectance. The SEM analyses of fracture surfaces revealed differences in the micromechanical behavior depending on the matrix morphology. Particular emphasis was put on the distinction of individual forms of pyrolytic carbons with similar optical behavior, which reveals significant structural differences in detailed SEM and TEM analyses.