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

聚合物衍生陶瓷纳米复合材料(PDC-NCS)可以通过将合适的单源前驱体转化为陶瓷来合成，第一步是无定形单相陶瓷，然后经过相分离过程得到双相或多相陶瓷纳米复合材料。PDC-NCs具有耐人寻味的特性，使其成为在高温和恶劣环境下应用的结构和多功能材料的优秀候选者。然而，尽管有一些案例研究涉及聚合物结构对所得陶瓷的组成和微观结构的影响以及对其性能的影响，但对于这些方面还没有系统的/一般的了解。因此，本提案的目的是系统地研究单一来源的前驱体对所得到的陶瓷纳米复合材料的(纳米/微)结构的影响，从而对其(高温)性能进行系统的研究。在此背景下，计划对模型材料进行系统研究。将考虑的聚合物衍生陶瓷系统是Si-C-N三元陶瓷系统以及相关的化学修饰的模型系统(即SiHf(B)CN基PDC-NCS)。基于Si(Hf，B)CN的PDC-NCS的组成和微观结构以及高温行为将被广泛研究。在此背景下，将具体讨论高温结晶和分解过程以及氧化/腐蚀和蠕变行为。该提案的主要目的将最终阐明前驱体的分子结构/构型与所得到的PDC-NCS的纳米/微观结构和高温性能之间的关系。考虑到PDCNCs极有希望的特性(特别是在高温下)及其在恶劣条件(温度、环境)下的应用潜力，本提案中计划的系统研究将提供一个极好的机会，以合理、基于知识的方式制备和使用这些独特的材料，用于超出最先进水平的应用。

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.