744 Ph Colomban, N. lapous uniform habit and the detachment of some grains is corrosion is straightforward and the platelet habit is observed. The corrosion rate is faster for hexag clearly visible at the limit between the pyrolysed celsian and especially for lithium-containing matrices ZrSiPB interface precursor and the matrix (monoclinic celsian, see Fig. 4(a)). The anisotropic Typical microstructure char ges induce Fig. 4. Polished sections of BAS-matrix composites after attack for: (a)15 min(5);(a )30 min(5);(a)30 min(10)by boiling sulphuric acid. (c) Polished sections of CAS-matrix composite after attack by sulphuric acid for 90 min site 2. interslab section). The corrosion after chemical attack by a NaNO, melt is shown in(b) composite 5, BAs matrix NAS matrix, 6 h. See Table 1 for preparation details744 Ph. Colomban, N. Lapous unifo am habit and the detachment of some grains is obser -ved. The corrosion rate is faster for hexagonal celsia m and especially for lithium-containing matrices (mon loclinic celsian, see Fig. 4(a”)). The anisotropic corrosion is straightforward and the platelet habit is clearly visible at the limit between the pyrolysed ZrSiPB interface precursor and the matrix. Typical microstructure changes induced by the Fig. 4. Polished sections of BAS-matrix composites after attack for: (a) 1.5 min (5); (a’) 30 min (5); (a”) 30 min (10) by boiling sulphuric acid. (c) Polished sections of CAS-matrix composite after attack by sulphuric acid for 90 min (composite 2, interslab section). The corrosion after chemical attack by a NaNO, melt is shown in (b) composite 5, BAS matrix, 6 h; (d) composite 3, NAS matrix, 6 h. See Table 1 for preparation details