Silicon-based ceramics are promising materials for high temperature applications in corrosive atmospheres.

For instance SiC, Si3N4, SiCN and SiCO represent such ceramic materials that can be prepared from the thermal conversion of polycarbosilanes, polysilazanes and polysiloxanes precursors. Some of the potential advantages in the preparation of ceramic materials from these precursors include (i) compositional homogeneity in the final products, (ii) high purity ceramic products with uniform microstructure, amorphous to microcrystalline, and (iii) the preparation of refractory ceramics at relatively low temperatures.

The present study describes the conversion of different types of polymers precursors and the high temperature behavior of the resulting silicon based materials. The aim is to better understand the effect of substituting groups bonded to silicon atom on the cross-linking and ceramic yield, as well as to evaluate the relationship between the structure of preceramic polymers, the pyrolysis conditions and final microstructure of the ceramic products.

The thermal decomposition in flowing inert or oxidizing gas was investigated by using two complementary techniques : the thermogravimetric analysis (TGA) and the continuous gas analysis by mass spectrometry. The pyrolysis products were characterized by other techniques, X-ray diffractometry, solid state NMS spectroscopy and chemical analysis. When combining these informations attained by these various methods of analysis, a very detailed picture of the thermal evolution of polymers can be obtained.

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