Advanced ceramics from a preceramic polymer and nano-fillers

A commercial silicone resin ("silicone") filled with ceramic nanoparticles has been employed for the preparation of mullite and beta-SiAlON ceramics. Dense, pure, crack free mullite were prepared by the heating in air of a mixture of silicone resin and alumina nanoparticles in the temperature range 1200-1550 degrees C. The high reactivity of Al(2)O(3) towards silica, coupled with nanometric size, led to a large volume fraction of mullite crystals even at low firing temperatures (1250 degrees C). beta-SiAlON ceramics were prepared by the heating of a mixture of silicone resin and fillers consisting of Al(2)O(3) nanoparticles and Si(3)N(4) and AlN microparticles, in the temperature range 1450-1550 degrees C in nitrogen atmosphere. The formation of SiAlON was found to be preceded by the formation of intermediate alumino-silicate phases like mullite and sillimanite, successively reduced (due to the carbon content of the ceramic residue of silicone resins) and nitrided. Although some oxide contamination was still present after the high temperature treatment, a high beta-SiAlON yield (about 80%) was achieved. The use of nano-filled silicones provides a promising route for the fabrication of advanced ceramic components by exploiting polymer processing techniques, with the achievement of complex shapes. (c) 2008 Elsevier Ltd. All rights reserved.