Polymer or precursor ceramics represent a novel class of high-performance materials that are produced by controlled pyrolysis of organometal compounds. Shrinkage and porosity resulting from thermal decomposition can be compensated by adding chemically reactive filler powders. This technique permits manufacturing of dense ceramic bulk components true to size by cost-effective near-net-shape forming of cross-linked green compacts. For process control, definition of the course of the reaction of the active fillers and thus the exact knowledge of the chemical composition and the microstructure development of the solid residues during pyrolysis of the polymer precursor is required. Due to both the great technical importance of the final ceramic products and their economical availability, in the present work, thermal decomposition of a silicone resin (polymethylsiloxane) at temperatures between 525 and 1550degreesC was characterized nanochemically and microstructurally. In part 1, the results of the quantitative phase identification by means of analytical electron microscopy are reported. The bonding state of silicon was determined by fine structure analysis (Si-L-2,L-3-ionisation edge) of the electron energy-loss spectrum and has proved to be always mainly oxidic. By means of energy-filtered transmission electron microscopy, elemental distributions in the nanometre range were recorded. The phase separation of the polymer-derived Si-C-O matrix into SiO2, C and SiC could be proved definitely. The characterization of structure formation by high-resolution imaging and diffraction methods follows in part 2.
