which took place after sintering at 1300oC. The The low viscosity(0.5-1 poise)of the liquid same phenomenon occurred for the composite polymeric precursors makes it possible to infiltrate matrix but cracks dominated after sintering at them in porous ceramics and to convert them into 1300C due to the matrix segmentation imposed ceramics by 'polymerization'and then pyrolysis by the invariable fibre array: the matrix densifi- Hydrolytic polycondensation of alkoxides is well cation crcatcd cracks documented for the preparation of oxides 3-16 FIBER FIBER MATRIX MATRIX Sinte Inter-particle Fig. 2. Microphotographs of a 1200oC sir composite (a, bar: 20 um; a', bar: 100 um ). The microcracking induced by the competition between the matrix shrinkage he invariant 3D fibre network is sketched in(b); detail of the dense packing of primary oxide particles inter-particle voids available for alkoxide infiltration is shown 1300c 00010.01 P。 re diameter(μm Pore diameter【μm Fig. 3. Pore distribution in an alumina monolith (a)and in a 3D reinforced composite(b), versus sintering temperature1478 Ph. Colomban, M. Wey which took place after sintering at 1300°C. The The low viscosity (-0.5-l poise) of the liquid same phenomenon occurred for the composite polymeric precursors” makes it possible to infiltrate matrix but cracks dominated after sintering at them in porous ceramics and to convert them into 1300°C due to the matrix segmentation imposed ceramics by ‘polymerization’ and then pyrolysis. by the invariable fibre array: the matrix densifi- Hydrolytic polycondensation of alkoxides is well cation created cracks. documented for the preparation of oxides.‘3m’6 Inteqmticle voids Fig. 2. Microphotographs of a 1200°C sintered composite (a, bar: 20 pm; a’, bar: 100 pm). The microcracking induced by the competition between the matrix shrinkage and the invariant 3D fibre network is sketched in (b); detail of the dense packing of primary oxide particles with inter-particle voids available for alkoxide infiltration is shown. Pore diametwfpm) Pore diameter lpm) Fig. 3. Pore distribution in an alumina monolith (a) and in a 3D reinforced composite (b), versus sintering temperature