Polymer-derived ceramics microstructure

Polymer-derived ceramics (PDCs) represent a rather novel class of ceramics which can be synthesized via cross-linking and pyrolysis of suitable polymeric precursors. In the last decades, PDCs have been attaining increased attention due to their outstanding ultrahigh-temperature properties, such as stability with respect to decomposition and crystallization processes as well as resistance in oxidative and corrosive environments. Moreover, their creep resistance is excellent at temperatures far beyond 1000 °C. The properties of PDCs were shown to be strongly related to their microstructure (network topology) and phase composition, which are determined by the chemistry and molecular structure of the polymeric precursor used and by the conditions of the polymer-to-ceramic transformation. 

Polymer derived ceramics have been known for the last four decades and are prepared via solid-state thermolysis of preceramic polymers. They exhibit a unique combination of remarkable properties due to their covalent bonding and amorphous nature. Thus, silicon oxycarbide (SiOC) and silicon carbonitride (SiCN) based ternary PDCs have been shown to possess outstanding high-temperature properties such as stability with respect to crystallization and decomposition, oxidation and corrosion resistance as well as excellent thermomechanical properties (e.g., near zero steady state creep resistance up to temperatures far beyond 1000 °C). Their properties are directly influenced by the chemistry and the architecture of the preceramic precursors, thus there is an enormous potential in tuning the microstructure and properties of the PDCs by using tailored polymers. Furthermore, suitable chemical modification of the preceramic precursors leads to quaternary and multinary ceramics, as it has been shown for instance for silicon boron carbonitride ceramics in the last 25 years, which in some cases exhibit improved properties as compared to those of the ternary materials. 

Toma, L., Kleehe, H.-J., Muller, M. M., Janssen, E., Riedel, R., Melz, T., Hanselka, H. (2011). Correlation Between Intrinsic Microstructure and Piezoresistivity in a SiOC Polymer-Derived Ceramic. Journal of the American Ceramic Society, n/a-n/a. 

M. Mayer, D. V. Szabo, M. Ruble, M. Seher, and R. Riedel, Polymer-Derived Si-Based Bulk Ceramics, Part I Microstructural Characterization by Electron Spectroscopy Imaging, J. Europ. Ceram. Soc. 1995, 15, 717-727. 

Klonczynski, A., Schneider, G., Riedel, R., Theissmann, R. (2004). Influence of boron on the microstructure of polymer derived SiCO ceramics. Advanced Engineering Materials, 6(1-2), 64—68. doi 10.1002/adem.200300525. 

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