F. Lamouroux et al., STRUCTURE OXIDATION BEHAVIOR RELATIONSHIP IN THE CARBONACEOUS CONSTITUENTS OF 2D-C PYC/SIC COMPOSITES/, Carbon, 31(8), 1993, pp. 1273-1288
Oxidation tests were performed (at 500 < T < 900-degrees-C), on (a) as
-received T300 fiber, (b) PyC-infiltrated tows, and (c) C/PvC/SiC comp
osite. The goal was to assess which carbonaceous constituent exhibits
the highest reactivity with oxygen in the composites. TGA and TEM were
used to establish the relationship between the behaviour of the mater
ials in oxygen and their nano/microtexture. In the as-processed state,
the overall oxidation rate of the fiber is higher than that of the Py
C-interphase, whereas both constituents behave in a similar way after
an annealing treatment at 1600-degrees-C. Beyond 700-degrees-C, the ra
te-determining step in the oxidation of uncoated fibers is diffusion t
ransport in the external stagnant boundary layer. Below 700-degrees-C,
it is a mixed in-pore diffusion/surface reaction mode for the as-rece
ived fibers and mainly surface reaction for the annealed fibers. The o
xidation of the fiber is selective. In cross-section, it occurs more r
apidly in the outer zone, owing to the high porosity of this specific
zone. The occurrence of a high porosity zone very near the PyC interph
ase plays a kev role in understanding the effect of environment on the
mechanical behaviour of the composites.