Active-Filler-Controlled Pyrolysis of Preceramic Polymers

Authors

  • Peter Greil

    1. Department of Materials Science (Glass and Ceramics), University of Erlangen-Nuernberg, D-91058 Erlangen, Germany
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      Member, American Ceramic Society.


  • G. L. Messing — contributing editor

  • Peter Greil received a Dipl. Ing. degree in mineralogy/crystal chemistry and a Ph.D. in metallurgy from University of Stuttgart, Germany, in 1982. As a member of the research staff at the Powder Metallurgical Laboratory of the Max-Planck-Institute for Metals Research, he worked on microstructure and high-temperature properties of non-oxide ceramics for seven years. In 1988, Greil joined the faculty of mechanical engineering at the Technical University of Hamburg-Harburg, where he changed fields to work on processing of composite ceramics involving powder and non-powder processing techniques. Since 1993, Greil has been professor of glass and ceramics at the Department of Materials Science at the University of Erlangen-Nuernberg. Currently, he is engaged in novel processes for fabrication of composite ceramics from preceramic polymers and metal precursor systems.

Abstract

Manufacturing of bulk ceramic components from materials in the system Si-Me-C-N-O (Me = Ti, Cr, V, Mo, Si, B, CrSi2, MoSi2, etc.) from preceramic organosilicon polymers - such as poly(carbosilanes), poly(silazanes), or poly(siloxanes) - has become possible by incorporating reactive filler particles into the liquid or solid polymer pre-cursor. During pyrolytic decomposition of the polymer matrix, the filler particles react with carbon from the polymer precursor or nitrogen from the reaction gas atmosphere to form new (oxy)carbide or (oxy)nitride phases embedded in a nanocrystalline Si-O-C(-N) matrix. The selective expansion encountered in the filler phase reaction can be used to compensate for the polymer shrinkage upon pyrolytic conversion. The formation of a transient pore net-work between 400° and 1000°C is governed by the polymer decomposition as well as the filler particle reaction kinetics. Thus, the properties of the oxycarbonitride composite materials can be tailored by controlling the microstructures of the polymer-derived matrix phase, the filler network, and the residual porosity. Near-net-shape forming of bulk ceramic components, even with complex geometry, is possible, making novel applications of polymer-derived bulk materials in biomedical, electrical, and mechanical fields highly interesting.

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