Microstructural Engineering of Shape Memory Thin Films and Nanowires

形状记忆薄膜和纳米线的微结构工程

• 批准号: 0907090
• 负责人: Ainissa Ramirez
• 金额: $ 40.5万
• 依托单位: Yale University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-07-01 至 2012-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0907090&HistoricalAwards=false
• 关键词: Microstructural; Engineering; Shape; Memory; Thin

This Award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).TECHNICAL SUMMARY:Materials like NiTi, which have the unique ability of ?remembering? their original shape when heated, can be used as actuators. These materials undergo a martensitic phase transformation from one crystallographic structure to another and provide large actuation forces. Despite these interesting properties the integration of shape memory alloys in microelectromechanical systems (MEMS) is limited because the details of the phase transformation that activates the shape changes is very sensitive to microstructural details. For example a small increase in grain size significantly changes the actuation force and the transformation temperature. In addition, the mechanical behavior of NiTi in thin-film form differs from the bulk and is a largely unexplored research topic. Objectives of this program are to evaluate the effects of grain structure, grain size and grain-size distributions on phase transformation temperatures, hysteresis behavior, actuation properties, and mechanical properties. Accordingly, we will explore the crystallization behavior of NiTi thin films and nanostructures; and broaden the understanding of thin film mechanical properties by examining materials that exhibit elastic nonlinearities. Structure-property relationships will be studied by observing microstructural development using in situ transmission electron microscopy. Evolution of the and grain structure will be evaluated using the Johnson?Mehl?Avrami?Kolmogorov theory. The resulting actuation properties of the engineered microstructures will be studied with wafer curvature methods and MEMS-based cantilevers; and the transformation temperature changes will be investigated with differential scanning calorimetry. The dependence of mechanical properties on microstructure will be examined with nanoindentation. This study will provide novel observations of the behavior of thin film shape memory materials, and provide guidance for their adoption into MEMS.NON-TECHNICAL SUMMARY:Knowledge of the link between phase transformations, microstructure, and mechanical properties will be studied in thin films by observing a new class of materials that undergo a martensitic (i.e. displacive) transformation. From this work, we will improve the fundamental understanding of thin-film shape memory alloys and learn how to control their properties in a predictable way, thereby illuminating the role of microstructure on the thermodynamics of martensitic transformations. This ability to control properties will benefit the MEMS community and enable future devices. Additionally, these materials provide a model to hone the ability to tailor microstructures and will benefit other research pursuits in amorphous silicon, amorphous carbon, and metallic glasses. This program?s broader impact consists of stimulating the interest in science for a range of individuals from the training of graduate students to the encouragement of school children. A revamped introductory materials science class that includes hands-on demonstrations and real-world examples will cultivate engineers with strong materials backgrounds. A compilation of classroom demonstrations disseminated on the web will serve a wider learning community. This educational program also provides informal opportunities to change the perception of science via a lecture series that showcases diverse scientists and presents enjoyable science events. The aim is to encourage all students, particularly students of color and girls, to consider science as a career. It furnishes richer connections to science for school children, their teachers, and their parents and is a simple model that can be extended within and between universities. By leveraging a partnership with the NISE network, this program will have large dissemination channels. Leaving no student behind, this program seeks to capture the attention of non-science majors in a liberal-arts environment by using them as demonstrators to teach science in a compelling way.

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。技术概述：像镍钛这样的材料，具有独特的记忆能力。当加热时，它们的原始形状可以用作执行器。这些材料经历从一种晶体结构到另一种晶体结构的马氏体相变，并提供大的驱动力。尽管有这些有趣的特性，但由于激活形状变化的相变细节对微结构细节非常敏感，因此形状记忆合金在微机电系统（MEMS）中的集成受到限制。例如，晶粒尺寸的微小增加会显著改变驱动力和转变温度。此外，薄膜形式的NiTi的力学行为不同于体，这是一个很大程度上未开发的研究课题。本程序的目的是评估晶粒结构、晶粒尺寸和晶粒分布对相变温度、滞后行为、驱动性能和力学性能的影响。因此，我们将探索NiTi薄膜的结晶行为和纳米结构；并通过研究表现出弹性非线性的材料，拓宽对薄膜力学性能的理解。结构-性能关系将通过使用原位透射电子显微镜观察微观结构的发展来研究。采用Johnson?Mehl?Avrami？柯尔莫哥洛夫的理论。工程微结构的驱动特性将通过晶圆曲率方法和基于mems的悬臂来研究；用差示扫描量热法研究相变温度的变化。力学性能与微观结构的关系将通过纳米压痕进行研究。本研究将对薄膜形状记忆材料的行为提供新的观察，并为其在MEMS中的应用提供指导。非技术总结：通过观察一类经历马氏体（即位移）转变的新材料，我们将在薄膜中研究相变、微观结构和机械性能之间的联系。通过这项工作，我们将提高对薄膜形状记忆合金的基本认识，并学习如何以可预测的方式控制其性能，从而阐明微观结构在马氏体相变热力学中的作用。这种控制特性的能力将使MEMS社区受益，并使未来的器件成为可能。此外，这些材料提供了一个模型来磨练定制微结构的能力，并将有利于非晶硅、非晶碳和金属玻璃的其他研究。这个程序吗?从培养研究生到鼓励学龄儿童，科学的广泛影响包括激发人们对科学的兴趣。经过改进的材料科学入门课程，包括动手演示和现实世界的例子，将培养具有强大材料背景的工程师。在网上传播的课堂演示汇编将为更广泛的学习社区服务。这个教育项目还提供了非正式的机会，通过一系列的讲座来改变对科学的看法，这些讲座展示了不同的科学家和令人愉快的科学事件。其目的是鼓励所有学生，特别是有色人种学生和女生，将科学视为一种职业。它为学生、他们的老师和他们的父母提供了与科学更丰富的联系，是一个简单的模型，可以在大学内部和大学之间推广。通过与NISE网络的合作，该项目将拥有庞大的传播渠道。不让任何一个学生掉队，这个项目试图在文科环境中吸引非理科专业学生的注意，用他们作为示范，以一种引人注目的方式教授科学。