Molecular Preparative Approaches to Si(Hf,B)CNBased Polymer-Derived Ceramic Nanocomposites for Ultrahigh-Temperature Applications

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Polymer-derived ceramic nanocomposites (PDC-NCs) can be synthesized via polymer-to-ceramic conversion of suitable single-source precursors, leading in a first step to amorphous single-phase ceramics, which subsequently undergo phase separation processes to furnish bi- or multiphase ceramic nanocomposites. PDC-NCs have been shown to possess intriguing properties which make them excellent candidates as structural and (multi)functional materials for applications at high-temperatures and under harsh environments.However, despite several case studies related to the effect of the polymer architecture on the composition and microstructure of the resulting ceramics as well as on their properties, no systematic/general understanding is yet available concerning these aspects.Thus, the intention of the proposal is to systematically study the effect of the single-source precursor on the (nano/micro)structure of the resulting ceramic nanocomposites and consequently on their (high temperature) properties. Within this context, systematic studies on model materials are planned. The polymer-derived ceramic systems which will be considered are the ternary ceramic system Si-C-N as well as related, chemically modified model systems (i.e., SiHf(B)CN-based PDC-NCs). The Si(Hf,B)CN-based PDC-NCs will be extensively investigated with respect to their composition and microstructure as well as to their high-temperature behavior. Within this context, high temperature crystallization and decomposition processes as well as oxidation/corrosion and creep behavior will be specifically addressed.The main aim of the proposal will be eventually to elucidate of the relationship between the molecular structure/architecture of the precursor and the nano/microstructure and HT properties of the resulting PDC-NCs. Taking into account the highly promising properties of PDCNCs (especially at high temperatures) and their potential in applications under harsh conditions (temperature, environment), the systematic studies planned within this proposal will provide an excellent opportunity to prepare and use these unique materials in a rational, knowledge-based way for applications beyond state-of-the-art.