Manufacturing and microstructure of novel materials in the Si-Al-O-N-C system derived from polymer-filler mixtures were investigated. Silicon (Si) and aluminium (AI) were added to a poly(methyl and phenyl)siloxane matrix to react with the carbon-bearing products that result from the decomposition of the latter during pyrolysis. This was carried out in nitrogen atmosphere up to 1500 degrees for 2h. Silicon Carbide (SiC) particles were used as inert filler embedded in the polymer/active filler mixture. Green bodies of the metal/polysiloxane mixtures were pressed and cured at 170 degreesC for 30min. Microcrystalline composites, such as SiC, AlN and SiAlON, from the filler reaction products embedded in a silicon oxycarbide glass matrix could be formed with complex geometry through near-net-shape process of polymer/ceramic conversion.