Polymer-Derived In-Situ Metal-Matrix Nanocomposites: A New Paradigm in Processing, Structure, and Properties of Dispersion Strengthened (copper) Alloys

技术概述：纳米级稳定的、非粗化的陶瓷颗粒分散到金属基体中是金属复合材料在高温下抗蠕变的先决条件。该计划的目标是为一种将陶瓷相的细颗粒分散到金属中的新方法开发科学基础，并了解它们如何影响机械性能。在这种方法中，将陶瓷作为聚合物引入金属中，然后原位热解以产生纳米分散的陶瓷相。本研究项目将探索聚合物原位转化为陶瓷的基本机制。铜，分散在由Si-C-N-O组成的聚合物衍生陶瓷相的纳米颗粒中，将被用作本研究的“模型”材料体系。在接近950℃（约熔点的0.9℃）时，研究了合金的显微组织稳定性和蠕变及蠕变断裂行为。基本机制，包括如何大小和间距，结构和键在颗粒-基质界面控制位错的攀升和孔洞的核在高温机械载荷下，将进行研究。一个关键问题是阐明界面键合如何影响阈值应力，最终目标是实现接近Orowan上限的阈值应力，以避免由硬颗粒固定的位错。原子模型有望为实验结果提供信息。非技术总结：具有不同寻常性能的新型纳米材料通常在制造方式和性能上都非常复杂。为了将它们成功地应用到下一代系统中，它们的性能必须以科学的理解和模型为基础。该研究项目致力于新型高温金属合金的科学和开发，这对未来的工程系统具有潜在的重要意义。他们的新颖之处在于用聚合物的方法在金属基体上制造出高度稳定的纳米级分散的陶瓷颗粒。该研究计划包括在奥地利和德国进行密切的国际合作，提供原子尺度表征和建模方面的重要专业知识。该项目有一个积极的计划，主要是通过每两年在科罗拉多州博尔德举行的国际会议来传播这项研究的科学成果。

TECHNICAL SUMMARY: A nanoscale dispersion of stable, non-coarsening ceramic particles into a metal matrix is a precondition for metallic composites that resist creep at high homologous temperatures. The goal of this program is to develop the scientific underpinnings for a new method for dispersing fine particles of a ceramic phase into a metal, and understanding how they influence the mechanical properties. In this method the ceramic is introduced into the metal as a polymer, which is then pyrolyzed in-situ to create the nanodispersed ceramic phase. This research program will explore the basic mechanisms for the in-situ conversion of the polymer into the ceramic. Copper, dispersed with nanoparticles of a polymer-derived ceramic phase constituted from Si-C-N-O, will be employed as the "model" material system for this investigation. The microstructural stability and the creep and creep fracture behavior of the alloy at temperatures approaching 950 °C (about 0.9 of the melting temperature) will be investigated. Fundamental mechanisms that include how the size and spacing, and the structure and bonding at the particle-matrix interface control the climb of dislocations and the nucleation of voids under mechanical loading at high temperatures, will be studied. A key issue is to elucidate how the interfacial bonding influences the threshold stress, the ultimate goal being to achieve a threshold stress that approaches the Orowan upper bound for the escape of dislocations pinned by hard particles. Atomistic modeling isexpected to inform the experimental results.NON-TECHNICAL SUMMARY: New nanomaterials with unusual properties are often highly complex, both in the way they are made and how they perform. For them to be successfully implemented into next-generation systems, their performance must be underpinned by scientific understanding and models. This research program is dedicated to the science and development of novel high temperature metallic alloys that are potentially important for future engineering systems. Their novelty lies in a polymer route to the creation of a highly stable, nanoscale dispersion of ceramic particles in a metal matrix. The research plan includes intimate international collaborations in Austria and Germany that provide important expertise in atomic scale characterization and modeling. The program has an aggressive plan for dissemination of the scientific outcomes of this research, primarily through International Meetings that are held every two years in Boulder, Colorado.