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.
