Nanostructure and Calorimetry of Amorphous SiCN and SiBCN Ceramics

智力优势：聚合物衍生的陶瓷（PDC）是通过有机聚合物的仔细热分解获得的X射线无定形但纳米级异质的材料的广泛组，所述有机聚合物以受控比例提供硅、碳、氧、氮和/或硼。它们重量轻，具有优异的机械性能，并且在接近1500 oC的温度下仍保持不结晶或降解。该项目汇集了美国和德国的团队，他们在PDC合成、光谱、散射和成像工具表征、热化学测量和理论方面具有专业知识，以提供系统的数据，并对这些材料的结构、键合和稳定性产生基本的理解，重点是SiBCN系统中的新材料，以及SiCO、SiCN和SiOCN系统中的PDC。一个具体的目标是要了解最近观察到的热力学稳定性的起源（从二元晶体端员形成的三元非晶陶瓷的放热）在大范围的组合物中的SiCO和SiCON系统。纳米相域的性质和它们的界面，其中含有硅键合到一个以上类型的阴离子可能是这种稳定性的起源，但更详细的结构模型必须开发。这些模型必须与纳米结构，光谱和热化学动力学数据一致，并且必须由纳米畴界面处的结构和相互作用的第一原理计算指导。具体来说，达姆施塔特的Riedel将专注于合成，加州大学戴维斯分校的Navrotsky将专注于量热测量和热力学分析，达姆施塔特的Kleebe将专注于电子显微镜，加州大学戴维斯分校的Sen将专注于核磁共振和振动光谱以及X射线和中子散射，加州大学戴维斯分校的Galli将专注于理论计算。作为材料世界网络项目，这汇集了美国和德国的研究人员，并为学生和博士后提供了参与跨学科和国际材料研究的机会。计划安排一系列有条理的研究人员交流和讲习班。一些妇女（包括戴维斯大学三名教师中的两名）将参加该项目，正在招募来自其他代表性不足群体的年轻科学家。由于PDC具有广泛的潜在用途，从汽车和飞机发动机到涂层，这项基础研究的结果将有助于推进陶瓷科学的实际应用。

Intellectual Merit: Polymer derived ceramics (PDCs) are a broad group of x-ray amorphous but nanoscopically heterogeneous materials obtained by careful thermal decomposition of organic polymers which provide silicon, carbon, oxygen, nitrogen, and/or boron in controlled proportions. They are lightweight, have excellent mechanical properties, and persist without crystallization or degradation to near 1500 oC. This project brings together groups in the U.S.A. and Germany with expertise in PDC synthesis, characterization by spectroscopic, scattering, and imaging tools, thermochemical measurements, and theory to provide systematic data and generate fundamental understanding of the structure, bonding, and stability of these materials, with an emphasis on new materials in the SiBCN system, as well as PDCs in the SiCO, SiCN, and SiOCN systems. A specific goal is to understand the origin of the recently observed thermodynamic stability (exothermic heats of formation of ternary amorphous ceramics from binary crystalline end-members) over a large range of compositions in the SiCO and SiCON systems. The nature of the nanophase domains and their interfaces which contain silicon bonded to more than one type of anion may be the origin of such stability, but much more detailed structural models must be developed. These models must be consistent with nanostructural, spectroscopic and thermochemdynamic data, and must be guided by first principles calculations of structure and interactions at the nanodomain interfaces. Specifically, Riedel at Darmstadt will concentrate on synthesis, Navrotsky at UC Davis on calorimetric measurements and thermodynamic analysis, Kleebe at Darmstadt on electron microscopy, Sen at UC Davis on nuclear magnetic resonance and vibrational spectroscopy and x-ray and neutron scattering, and Galli at UC Davis on theoretical calculations.Broader Impacts: As a Materials World Network project, this brings together researchers in the U.S.A. and Germany and provides students and postdocs an opportunity to participate in both interdisciplinary and international materials research. A structured set of exchanges of researchers and workshops is planned. A number of women (including two of the three faculty from Davis) will participate in the project and young scientists from other underrepresented groups are being recruited. Because PDCs have a wide range of potential uses, ranging from automotive and aircraft engines to coatings, the results of this fundamental study will help advance ceramic science with practical applications.