Detection and Imaging of Nanoscale Defects

我们提出了一个跨学科的研究计划，将正电子技术众所周知的缺陷敏感性与最先进的正电子束技术相结合，以检测和成像传统技术不适用的各种工程材料中的微结构损伤的早期阶段。无法描述压力计尺寸范围内的缺陷演化，这是我们对许多工程材料从合成到失效生命周期的基础知识中缺少的一个主要环节。如果材料科学家能够测量损伤从合成到失效的微观结构演变，他们将大大有助于提高材料的强度和耐久性、耐磨性和耐腐蚀性、环境兼容性和制造成本效益。本研究的主要目标是展示新的测量技术，该技术解决了缺陷形核和生长的初始阶段，形成更大的空洞，最终导致样品失效。这种缺陷积累(可高度局部化)可由机械手段(例如，疲劳、热应力)、化学手段(例如，腐蚀)、辐射或诸如电迁移等其他因素引起。样品系统的范围从结晶金属到无定形聚合物再到非均质复合材料，包括微电子器件、反应金属表面的钝化层和核电反应堆中的管道等。在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展将通过结合深度分布、微观横向分辨率来扩展多普勒展宽光谱、正电子发射和正电子寿命光谱的已知缺陷灵敏度。这将实现无损、三维、纳米级、缺陷成像。在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强大的现有合作基础上。为了在这样的跨学科项目中提供关键的指导，我们寻找了在大学、国家实验室和工业领域工作的专家合作者。

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.***