Unusual Stability of Amorphous Polymer Derived Ceramics at High Temperatures

这项拟议工作的目标是发现SiCN-SiCO系统中PDCs的分子结构是什么使它们如此抗结晶和抗蠕变。最近的SAXS研究表明，存在尺寸为1-3 nm的持久纳米结构域。然而，这些纳米结构域的化学和分子结构尚不清楚。它们是如何从有机聚合态转变为陶瓷态的，目前还不清楚。它们的形成热力学和界面能量学是未知的。为什么这些纳米结构域阻止了结晶和蠕变，目前还不清楚。这些问题必须一致回答，并相互联系起来。美国-德国团队融合了来自核磁共振(D)、SAXS(US)、高温氧化溶液化学(US)、从头算分子模拟(D)、无机合成与加工(D)和高温表征(US)的专业知识，以全面和根本地解决这一关键问题。这个国际团队是一个自然的联盟，也是对德国科学家在该领域早期发展中所发挥的重要作用的认可，以及美国人在研究聚合物衍生陶瓷高温现象学方面的最近作用。

The objective of the proposed work is to discover what it is about the molecular structure of PDCs in the SiCN-SiCO system that renders them so resistant to crystallization and to creep. Recent SAXS studies have shown the presence of persistent nanodomains, 1-3 nm in size. However, the chemical and molecular constructions of these nanodomains are unknown. How they envolve from the organo-polymeric state into the ceramic state is not understood. Their thermodynamics of formation and interfacial energetics are unknown. Why these nanodomains preclude crystallization and creep is unclear. These questions must be answered in unison, and in relationship to each other. The US-German Team coalesces the expertise from NMR (D), SAXS (US), high temperature oxidative solution chemistry (US), ab-initio molecular modelling (D), inorganic synthesis and processing (D), and high temperature characterization (US), to solve this critical issue comprehensively and fundamentally. This international team is a natural coalition of, and also a recognition of the important role played be German scientists in the early developments of this field, and the recent role of the Americans in investigating the high temperature phenomenology of polymer-derived ceramics.