Detection and Imaging of Nanoscale Defects

9732804 Gidley我们提出了一个跨学科的研究计划，结合了众所周知的缺陷灵敏度的正电子技术与国家的最先进的正电子束技术，以检测和成像的早期阶段的微结构损伤在广泛的工程材料，传统的技术是不够的。 无法表征缺陷演变的压力计大小规模代表了一个主要的缺失环节，在我们的基础知识的合成失效的生命周期的许多工程材料。如果材料科学家能够测量从合成到失效的损伤的微观结构演变，他们将大大有助于改善材料的强度和耐久性，耐磨性和耐腐蚀性，环境相容性，本研究的主要目标是展示新的测量技术，该技术解决了缺陷成核和生长的初始阶段，以形成更大的空隙，最终导致样品失效。 这种缺陷累积（其可以是高度局部化的）可以通过机械手段（例如，疲劳，热应力），通过化学方法（例如，腐蚀）、辐射、或其它因素如电迁移。 样品系统的范围从结晶金属到无定形聚合物到异质复合材料，包括微电子器件、活性金属表面的钝化层和核电反应堆中的管道等各种物品。 这项研究中使用的主要新技术是正电子显微镜/微探针。 正电子束技术的这一进步将通过结合深度轮廓、微观横向分辨率来扩展多普勒加宽光谱、正电子发射和正电子寿命光谱的已知缺陷灵敏度。 这将有助于无损、三维、纳米级缺陷成像。 当研究不需要横向分辨率的特定表面和薄膜时，更传统的非微观光束将继续以深度轮廓模式使用。拟议的研究是一个基础广泛的探索性计划，建立在密歇根大学物理系和材料科学与工程系之间现有的强大合作基础上。 为了在这样一个跨学科的项目中提供重要的指导，我们已经找到了在大学，国家实验室和工业界工作的专家合作者。

9732804GidleyWe propose an interdisciplinary research program that combines the well known defect sensitivity of positron techniques with state-of-the-art positron beam technology in order to detect and image the early stages of microstructural damage in a wide range of engineering materials where traditional techniques are not adequate. The inability to characterize defect evolution on the manometer size scale represents a major missing link in our fundamental knowledge of the synthesis-to-failure life cycle of many engineering materials. If materials scientists can measure the microstructural evolution of damage from synthesis to failure they will be greatly aided in improving such material properties as strength and durability, wear and corrosion resistance, environmental compatibility, and fabrication cost effectiveness.The major goal of this research is to demonstrate new measurement technology which addresses the initial stages of the nucleation and growth of defects to form larger voids that eventually lead to sample failure. Such defect accumulation (which can be highly localized) may be induced by mechanical means (e.g., fatigue, thermal stress), by chemical means (e.g., corrosion), by radiation, or by other agents such as electromigration. Sample systems range from crystalline metals to amorphous polymers to heterogeneous composites, and include such diverse items as microelectronic devices, passivation layers on reactive metal surfaces, and pipes in nuclear power reactors. The primary new technique to be used in this research is the positron microscope/microprobe. This advancement in positron beam technology will extend the known defect sensitivity of Doppler broadening spectroscopy, positron emission, and positron lifetime spectroscopy by incorporating depth profiled, microscopic lateral resolution. This will pen-nit non-destructive, three dimensional, nanoscale, defect imaging. A more traditional non-microscopic beam will continue to be used in a depth profiled mode when studying particular surfaces and films that do not require lateral resolution.The proposed research is a broad-based exploratory program that builds upon a strong existing collaboration between the University of Michigan Physics Department and the Materials Science and Engineering Department. To provide critical guidance in such an interdisciplinary program we have sought out expert collaborators working at universities, national laboratories and in industry.***