Fibre-matrix interfacial zone in ceramic matrix composites: R. R. Naslain 0.1 um 0.1pm 15%t,B 01m 0% at B(Py FIBRE 100 lifetime at 600%C air 800MIPa time (h) Figure7 Nicalon/C(BySiC microcomposites with a graded composition interphase: (a) structure of the interphase, (b)deflection mode of a matrix k(TEM image), and(c)lifetime curves of microcomposites with a single PyC interphase or C(B)interphases. in air at 600C(interphase A is similar to a' but without layer V), according to Ref. 85 with time as the pyrocarbon interphase is consumed (the so shown in Figure 8a, the sublayer thicknesses were in the called pipeline oxidation), and for that of silica on the pore range 50-100 nm and their morphology relatively rough, as wall(assuming passive oxidation ). Oxygen has thus to a result of the preferred growth of B-Sic in the [lll diffuse along the pore for continued reaction with direction. The main advantage of replacing part of the carbon.8. Since this pipeline oxidation is easier when compliant pyrocarbon by stiff Sic was to improve the FM the PyC interphase is thick, a design strategy which has been load transfer and the tensile behaviour whereas the effect of cpajordx is to reduce the PyC thickness by oxidizing environments is discussed elsewhere. Further, lacing, in a sequencial manner, part of the pyrocarbon by lowering the sublayer thicknesses to a few nm and by a glass former such as SiC, the glass being expected to replacing stoichiometric SiC by smooth nanocrystalline SiC plug the annular pores(which now display a much lower +C deposits, more regular(PyC-SiC), interphases witl cross-section) and hence to slow down the oxidation typically 10 n 30 were deposited, utilizing P-CVI process. Multilayer(PyC-SiC), interphases, with typically (Figure &b)47. Preliminary experiments on model micro 1 n<4, have been deposited by conventional I-CVI in composites have shown that such highly engineered 2D-Nicalon fibre preforms, utilizing alternately a carbon interphases, which have common feature with the structure and a Sic precursor,97 Under such conditions, as of seashells, increased both the tensile failure strength and 1152