CAREER: Microstructure and Size Effects on Metal Plasticity at Limited Length Scale

技术：只有充分了解微结构和样品大小的影响，才能在一维金属纳米线的强度和塑性方面取得有意义的结果。这些研究活动的两个焦点是：(1)利用平行原子模拟来表征金和镍纳米线中晶格位错和特殊晶界之间的复杂相互作用；(2)利用电化学方法和原子力显微镜测量具有可控微结构和晶粒度的金和镍纳米线的强度、延展性和应变速率敏感性。这将使PI能够从理论和实验上证明，特殊的晶界，如孪晶界，可以显著改善纳米线的这些特性。智能的优点在于提出了一种综合的实验/建模研究方法，利用了原子模拟和原子力显微镜的力量。这种方法的结合将非常成功地弥合单个纳米积木材料的力学表征中实验和建模之间的差距。这种方法的另一个潜在结果是帮助迅速建立新的标准方法和校准程序来测试纳米线，以及定义良好的薄膜纳米压痕技术，开辟新的研究领域并产生更多发现。这项研究还有望展示制造纳米棒和纳米线的新方法，这些纳米棒和纳米线具有特定的缺陷，使它们变得更坚固。非技术性：这个五年计划的教育部分与多学科研究计划紧密结合在一起。国际学生计划将对佛蒙特州大学(UVM)的教育和宣传做出重大贡献，以(1)带头修订工程学研究生课程，重点是多尺度系统和建模；(2)通过现有的国际学生交流计划(ISEP)，在本科阶段与八个欧洲工程学专业课程建立国际学生交流计划；(3)通过一种与摄影艺术交叉的新颖科学成像，制定一个强有力的推广计划，以改善佛蒙特州北部农村高中和密西斯诺伊山谷社区的Abenaki印第安人部落的工程学学生的招生工作。这一职业奖还将广泛促进对该领域的了解，同时促进参与研究项目的本科生和研究生的教育培训。特别是，这一奖项有望加强学生在高性能和并行计算以及高分辨率成像领域的教育。研究生还将有机会在国家会议上广泛传播研究成果，以增进对该领域的科学理解。这项职业奖将鼓励使用多用户设施，即UVM新成立的佛蒙特州高级计算中心，并让科学家参与美国能源部新设立的国家研究设施。这一职业奖项的教育计划将广泛地重振密歇根大学对材料科学和工程的兴趣，帮助从代表性不足的群体中招收工程专业学生，并改善学生的多元文化培训。

TECHNICAL: Meaningful results related to strength and plasticity in one-dimensional metallic nanowires can only be achieved if the influences of microstructure and sample size are fully understood. The two foci of these research activities are to (1) use parallel atomistic simulation to characterize the complex interactions between lattice dislocations and special grain boundaries in gold and nickel nanowires, and (2) measure the strength, ductility and strain-rate sensitivity of gold and nickel nanowires with controlled microstructures and grain size using applied electrochemical methods and atomic force microscopy. This would enable the PI to prove both theoretically and experimentally that special grain boundaries such as twin boundaries can dramatically improve these properties in nanowires. The intellectual merit lies in the presentation of a combined experimental/modeling research approach harnessing the power of both atomistic simulation and atomic force microscopy. This combination of methodologies will be very successful in bridging the gap between experiment and modeling in the mechanical characterization of individual nano-building block materials. Another potential outcome of such approach can be to rapidly help establish new standard methods and calibration procedures to test nanowires, as well-defined as nanoindentation technique for thin films, open up new research areas and lead to more findings. The research is also expected to show new ways to fabricate nanorods and nanowires with specific defects that make them stronger. NON-TECHNICAL: The educational component of this 5-year plan is strongly integrated to the multidisciplinary research program. The PI will make major educational and outreach contributions at the University of Vermont (UVM) to (1) spearhead the effort of revising the graduate engineering program with a focus on Multiscale Systems and Modeling; (2) structure international student exchanges with eight European engineering-specific programs at undergraduate level via the existing International Student Exchange Program (ISEP); and (3) develop a vigorous outreach program, via a novel scientific imaging which cross-cuts with the photographic arts, to improve the recruitment in engineering of students from rural high schools in Northern Vermont and the Abenaki Indian tribe in the Missisquoi Valley community. This CAREER award will also broadly advance the understanding in the field while promoting educational training of undergraduate and graduate students involved in the research project. In particular, this award is expected to enhance the education of students in the area of high performance and parallel computing, and high-resolution imaging. The graduate students will also have opportunities to broadly disseminate the results of the research at national conferences and meetings to enhance scientific understanding in the field. This CAREER award will stimulate the use of a multi-user facility, UVM's newly-established Vermont Advanced Computing Center, and involve the participation of scientists at a new US DOE's national research facility. The education program of this CAREER award will broadly revitalize the interest for materials science and engineering at UVM, help recruit engineering students from underrepresented groups, and improve the student's multicultural training.