CAREER: Mechanics of Ultra-Strength Nanomaterials: Revealing Deformation Mechanisms

技术总结：该职业奖支持一个研究项目，该项目旨在描述一种新的材料--超强材料，这种材料具有承受接近理论极限的试件范围的机械应力的能力，即晶体材料中可达到的最大应力。本项目是一项揭示超强纳米材料基本变形机理的实验研究。对“硬”材料(金属、陶瓷、半导体)的实验将试图确定强度和速率控制塑性的机制。该项目将采用一套定量的原位纳米机械实验，以提供直接观察到的结构、缺陷成核和演化、长度尺度和伴随的材料响应之间的重要联系。系统地改变试验温度和采用瞬时力学试验(如应变率变化、应力松弛)将定量地阐明塑性变形的能垒。这项研究由三个技术目标驱动：(A)合成无准缺陷的单晶和异质结构纳米材料；(B)在高分辨率电子显微镜和聚焦离子束显微镜上采用定量的原位纳米力学测试，利用不同的温度和瞬变实验来识别和研究应力接近理想极限时的变形机制；以及(C)利用对缺陷和缺陷对随之而来的力学响应的影响的洞察，设计允许混合功能的微结构控制的新型纳米材料。非技术摘要：这项研究项目是由几个技术相关问题推动的：(1)当整个试件、特征、(2)这些超强材料的强度和速率控制变形机制如何通过纳米级的合成和定量的原位力学测试来实验阐明？(3)超强材料中可用的高动态弹性应变范围能否通过应变工程来调整功能特性，如电和热传输？拟议的活动旨在通过新的培训和推广计划丰富宾夕法尼亚大学学生的教育和研究经验。该项目将包括开发一门本科课程，将纳米级材料科学与工程融入其中。此外，还将启动一系列国会访问华盛顿特区的试点活动。它是面向本科生和毕业生通过杰罗姆·费舍尔管理与技术计划进行工程和经济学混合培训。还将通过拟议将国际合作研究与该项目相结合来提供经验和机会。

TECHNICAL SUMMARY: This CAREER award supports a research project to characterize a new class of materials, the ULTRA-STRENGTH, which have the capability of withstanding specimen-wide mechanical stresses that approach the theoretical limit, i.e. the maximum achievable stress in crystalline materials. This project is an experimental study to reveal the fundamental deformation mechanisms of ultra-strength nanoscaled materials. Experiments on "hard" materials (metals, ceramics, semiconductors) will attempt to ascertain both the strength- and rate-controlling plasticity mechanisms. The project will employ a suite of quantitative in situ nanomechanical experiments to provide essential links between directly observed structures, defect nucleation and evolution, length scales, and attendant materials response. Systematically varying the testing temperature and employing transient mechanical tests (e.g. strain-rate changes, stress relaxations) will quantitatively elucidate the energy barriers for plastic deformation. This research is driven by three technical objectives: (a) synthesize quasi-defect free single crystalline and heterostructure nanomaterials, (b) employ quantitative in situ nanomechanical testing in high-resolution electron and focused-ion-beam microscopes utilizing varied temperature and transient experiments to identify and study deformation mechanisms at stresses near the ideal limit, and (c) leverage the insight gained of the influence of flaws and defects on attendant mechanical response to engineer novel nanomaterials with microstructural control allowing for hybrid functionality.NON-TECHNICAL SUMMARY: This research project is motivated by several technologically relevant questions: (1) How do nanomaterials accommodate deformation when an entire specimen, feature, or device is subjected to stresses at or near the theoretical limit of strength? (2) How can the strength- and rate-controlling deformation mechanisms of these ultra-strength materials be experimentally elucidated via nanoscale synthesis and quantitative in situ mechanical testing? (3) Can the high dynamic range of elastic strain available in ultra-strength materials be used to tune functional properties such as electrical and thermal transport via strain engineering? The proposed activity aims to enrich the educational and research experience of students at UPenn through new training and outreach programs. The project will include the development of an undergraduate curriculum with infusions of nanoscale materials science & engineering. Additionally, a pilot series of Congressional visits to Washington DC will be launched. It is intended for undergraduates and graduates with hybrid engineering and economics training via the Jerome Fisher Management & Technology Program. Experiences and opportunities will also be provided through the proposed integration of international collaborative research with this project.