Fracture Mechanics of Nanowires and Nanostructures

理想晶体的强度一直是人们感兴趣的问题，但“真正的”材料的强度较低，因为它们有缺陷。纳米结构可能会以不同于较大结构的方式失效，因此对纳米结构如何断裂(断裂)的研究提供了一个将“真实”与“理想”联系起来的机会。这项关于纳米线断裂的研究具有新的结构，由于其电、热和机械性能而具有重要意义，该研究包括美国、瑞典和韩国的合作者，他们将为机械测试提供纳米线。一种新型的微型机电(基于MEMS)的机械加载平台可以在亚纳米分辨率的透射电子显微镜内操作，它将与其他微小的测试设备一起使用，以找出是什么导致纳米线断裂。纳米线可用于纳米电子学(作为逻辑、存储器和互连元件)，由于其高表面体积比和对表面相互作用的特殊敏感性而作为化学传感元件，在纳米机电系统(NEMS；作为机械部件、机电部件、致动器、应变计、流量传感器等)中，以及在结构复合材料中，纳米线的结晶完整性有望赋予其特殊的刚性、强度和韧性。因此，重要的是要了解单晶纳米线的详细机制，这样才能为它们随后在存在机械应力的各种应用中使用提供知识基础。这一努力包括研究生和博士后研究员的研究计划，本科生和高中教师的暑期研究培训，以及其他教育活动。

The strength of an ideal crystal has long been of interest but 'real' materials have lower strengths because they have defects. Nanostructures can fail differently from larger structures, so studies of how nanostructures will break (fracture) provide an opportunity to connect the 'real' to the 'ideal'. This study of fracture in nanowires having novel structures that are important due to their electrical, thermal, and mechanical properties includes collaborators in the United States, Sweden, and South Korea who will provide nanowires for mechanical testing. A new microelectromechanical ('MEMS-based') mechanical loading stage that can operate inside a transmission electron microscope with sub-nanometer resolution will be used along with other tiny testing devices to find out what makes nanowires break. Nanowires may be used in nanoelectronics (as logic and memory and interconnect elements), as chemical sensing elements due to their high surface to volume ratio and exceptional sensitivity to surface interactions, in nanoelectromechanical systems (NEMS; as mechanical components, electromechanical components, actuators, strain gauges, flow sensors, others), and in structural composites where the crystalline perfection of nanowires is expected to confer exceptional stiffness, strength, and toughness. It is thus important to understand the detailed mechanics of single crystal nanowires so a base of knowledge can be available for their subsequent use in diverse applications where mechanical stress will be present. This effort includes research programs for graduate students and postdoctoral fellows, summer research training for undergraduate students and high school teachers, and other educational activities.