NSF - (US-German) Materials Collaboration: Unusual Stability of Amorphous Polymer Derived Ceramics at High Temperatures

NSF -（美国-德国）材料合作：非晶聚合物衍生陶瓷在高温下的异常稳定性

• 批准号: 0502781
• 负责人: Rishi Raj
• 金额: --
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-08-15 至 2009-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0502781&HistoricalAwards=false
• 关键词: NSF; US; German; Materials; Collaboration

This research program is focused on the relationship between synthesis, structure and properties of a new class of ceramic materials that are made directly from polymers. They are becoming known as PDC's, or polymer-derived-ceramics. Currently two families of PDC's, silicon carbonitride (SiCN) and silicon oxycarbide (SiCO), have been identified. The PDC's are neither a crystal nor a glass; instead they contain nanodomains, about 1-5 nm in size. These nanodomains persist to very high temperatures, up to 1500oC; that is, their nanodomain structure resists large-scale crystallization at temperatures where the stoichiometric constituents (Si3N4, SiC and SiO2) would readily crystallize. The excess carbon in the composition is known to influence this behavior but the materials science of PDC's remains largely un-understood. In this project the faculty and students at the University of Colorado will collaborate with Professor Navrotsky at the University of California at Davis and her students, and with scientists and students from three institutions in Germany (Universities of Stuttgart, Darmstadt and Aachen) to elucidate (i) the evolution of the nanodomain structure from the structure of the organic polymeric state during controlled pyrolysis, and (ii) the relationship between the nanostructure of SiCN and SiCO, and their alloys, and their properties, e.g. crystallization, resistance to creep, and thermodynamic and kinetic behavior. Students from both countries will visit sister institutions across the Atlantic for extended periods to foster international scientific collaboration. One of the key features of the program is to highlight the use of non-conventional techniques for characterizing the nanostructure and the modeling of properties of these non-traditional class of ceramics. NMR and FTIR spectroscopies will be used to identify the first (and to some extent the second) nearest neighbor configuration of molecules, Raman spectroscopy to quantify the short range and long-range bonding of carbon atoms, and small-angle-X-ray-scattering will be employed to characterize the size and the distribution of nanodomains. The thermodynamic predictions of the structure derived from the above spectroscopic information and molecular modeling will be checked against measurement of the thermodynamic enthalpies by high temperature calorimetry. For example, the interfacial energies of the nanodomains predicted by molecular modeling will be measured directly in this way. For example, this information will be built into models that can explain the unusual resistance of PDC-s to crystallization. Nanotechnologies for high temperatures (space and energy are two examples) require materials that must have a special property: their structure must remain stable at temperatures where atoms can move and change the structure. This program is focused on a new class of ceramics, called polymer-derived-ceramics or PDC's that resist this time and temperature dependent change. The PDC's are robust and multifunctional materials, which will usher in breakthrough technologies such as sensors, electronics and optoelectronics, and coatings that can be used in extreme environments. The objective of this project is to develop a scientific base of fundamental understanding of PDC's, which is not present, and which is essential for these new technologies to move forward. This program involves two major US universities, one in Colorado and the other in California, and three German universities in close collaboration. Five to seven doctoral graduate students and an equal number of undergraduate students will participate in this materials world network collaboration between the United States and Germany.

本研究项目的重点是直接由聚合物制成的新型陶瓷材料的合成、结构和性能之间的关系。它们被称为PDC，即聚合物衍生陶瓷。目前已经确定了两类PDC，即碳氮化硅（SiCN）和碳化氧硅（SiCO）。PDC既不是晶体也不是玻璃；相反，它们包含约1-5纳米大小的纳米结构域。这些纳米结构域可以持续到非常高的温度，高达1500℃；也就是说，在化学计量成分（Si3N4， SiC和SiO2）容易结晶的温度下，它们的纳米结构抵抗大规模结晶。已知成分中过量的碳会影响这种行为，但PDC的材料科学在很大程度上仍然不为人所知。在这个项目中，科罗拉多大学的师生将与加州大学戴维斯分校的Navrotsky教授和她的学生，以及来自德国三所大学（斯图加特大学、达姆施塔特大学和亚琛大学）的科学家和学生合作，阐明(i)有机聚合物状态在受控热解过程中纳米结构的演变，以及（ii） SiCN和SiCO的纳米结构之间的关系。以及它们的合金及其性能，如结晶性、抗蠕变性、热力学和动力学行为。来自两国的学生将在大西洋彼岸的姐妹机构进行长期访问，以促进国际科学合作。该计划的主要特点之一是强调使用非常规技术来表征纳米结构和这些非传统类别陶瓷的特性建模。NMR和FTIR光谱将用于识别分子的第一个（在某种程度上是第二个）近邻配置，拉曼光谱将用于量化碳原子的短程和远程键合，小角度x射线散射将用于表征纳米畴的大小和分布。由上述光谱信息和分子模型得出的结构的热力学预测将通过高温量热法的热力学焓测量来检验。例如，通过分子模型预测的纳米结构域的界面能将通过这种方式直接测量。例如，这些信息将被构建到可以解释PDC-s不寻常的抗结晶性的模型中。用于高温的纳米技术（空间和能源是两个例子）要求材料必须具有一种特殊的性质：它们的结构必须在原子可以移动和改变结构的温度下保持稳定。该项目专注于一种新型陶瓷，称为聚合物衍生陶瓷（PDC），可以抵抗这种时间和温度依赖性变化。PDC是一种坚固耐用的多功能材料，它将带来突破性的技术，如传感器、电子和光电子以及可在极端环境中使用的涂层。该项目的目标是建立对PDC的基本认识的科学基础，这对于这些新技术的发展至关重要。该项目涉及两所主要的美国大学，一所在科罗拉多州，另一所在加利福尼亚州，以及三所德国大学密切合作。五至七名博士研究生和同等数量的本科生将参加美国和德国之间的材料世界网络合作。