Fracture Mechanics of Nanowires and Nanostructures

理想晶体的强度一直是人们感兴趣的，但“真正的”材料的强度较低，因为它们有缺陷。纳米结构的失效方式不同于更大的结构，因此对纳米结构如何断裂的研究提供了一个将“真实”与“理想”联系起来的机会。这项纳米线断裂的研究具有新颖的结构，由于其电学、热学和机械性能而非常重要，包括来自美国、瑞典和韩国的合作者，他们将提供用于机械测试的纳米线。一种新的微机电（“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，将与其他微小的测试设备一起使用，以找出导致纳米线断裂的原因。纳米线可用于纳米电子学（作为逻辑学、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灵敏度，可用于纳米机电系统(NEMS；作为机械部件、机电部件、致动器、应变片、流量传感器等)，以及结构复合材料中，纳米线的完美结晶有望赋予卓越的刚度、强度和韧性。因此，了解单晶纳米线的详细力学是很重要的，这样就可以为它们在随后的各种机械应力应用中提供基础知识。这项工作包括研究生和博士后的研究项目，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.