The microstructure of carbon–carbon composites obtained by
chemical vapor infiltration of a carbon fiber felt was comparatively
studied by reflection light microscopy, transmission electron
microscopy (TEM), scanning electron microscopy (SEM), atomic force
microscopy (AFM), and laser scanning confocal microscopy (LSCM).
Ar+ ion etching was used to reveal and distinguish
structural units of the pyrolytic carbon matrix. Mechanically polished
samples, polished and subsequently ion etched samples, and fractured
samples were compared. The values of surface roughness and surface
height after polishing or after polishing and subsequent etching
determined by AFM and LSCM correlate well with the degree of texture of
the matrix layers obtained by polarized light microscopy and selected
area electron diffraction. The carbon matrix is composed of structural
units or “cells,” which contain a carbon fiber and a
sequence of several differently textured layers around each fiber.
Within high-textured layers columnar grains are well recognizable using
polarized reflection light microscopy and confocal microscopy. The size
of depressions within high-textured carbon layers found by AFM after
ion etching correlates well with the size of differently tilted domains
detected by both TEM and SEM.