Creep-Based Nanomanufacturing of Crystalline Metals and Alloys

金属材料的纳米结构对于满足日益增长的催化、能量存储、传感器、过滤和药物输送等方面的需求至关重要。金属纳米结构的制造在很大程度上依赖于昂贵的光刻和薄膜沉积技术。模压成型是一种高通量的纳米结构制造工艺，但金属中粗大的晶体阻碍了其在纳米尺度上的流动。这笔赠款支持晶体金属高温塑性变形的基础研究，以促进基于模塑的可伸缩纳米制造。这项研究使得许多金属合金的高深宽比纳米结构的制备成为可能，其中包括高比表面积的多孔金属纳米结构，这些纳米结构非常适合于能量转换和存储以及生物医学应用。金属纳米结构的制造研究通过促进能源、医疗保健和其他工业部门的技术进步，从而促进美国的竞争力和繁荣，从而造福于经济和社会。该项目为所有级别的学生提供教育和动手培训，并为他们在先进制造业中不断增长的行业做好准备。该项目的外展活动旨在特别激励残疾学生投身科学和工程领域。纳米结构通常是通过模板成型软聚合物和其他玻璃材料在其稳定的粘性状态下制造的。然而，类似的方法并不直接适用于晶体金属，因为它们在固态中具有高活性的液态和刚性的微结构特征。本项目研究晶体金属和合金的蠕变塑性变形，以实现不同长度尺度的可控成型。金属的蠕变通常被认为对结构应用是有害的，但最近的研究表明，它具有可控纳米形成的潜力。通过对加工条件和原料进行系统变化的成型实验，可以分离不同的蠕变机制及其在控制纳米级金属成型中的作用。该项目研究了金属和合金热机械纳米成型中与尺寸有关的机制，例如位错介导的塑性、纳巴罗-鲱鱼蠕变和Coble蠕变，以及模板填充中的流动机制作为模具尺寸、加工时间和气氛的函数。从均质材料成型中获得的知识被应用于多相和多孔性金属合金，包括高熵和共晶合金。蠕变诱导流动的定量描述促进了对复杂合金和多孔结构中原子扩散的理解。除了新颖的制造科学，该项目还有可能贡献冶金和机械方面的新基础知识。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Nanostructures of metallic materials are critical for meeting the growing demands in catalysis, energy storage, sensors, filtration, and drug-delivery. Manufacturing of metal nanostructures largely relies on expensive lithography and thin film deposition techniques. Molding is a high-throughput fabrication process for nanostructures, but the large crystal grains in metals hinder their flow at nanoscale. This grant supports fundamental research in high temperature plastic deformation of crystalline metals to advance molding-based scalable nanomanufacturing. The research enables fabrication of high aspect-ratio nanostructures of many metallic alloys including high surface-area porous metal nanostructures which are highly desirable for energy conversion and storage and biomedical applications. The manufacturing research in metal nanostructures benefits the economy and society by advancing technologies in energy, healthcare and other industrial sectors thus advancing US competitiveness and prosperity. The project provides education and hands-on training to students at all levels and prepares them for the growing industry in advanced manufacturing. The outreach activities in this project are designed to particularly inspire students with disabilities for careers in science and engineering fields. Nanostructures are routinely fabricated by templated molding of soft polymers and other glassy materials in their stable viscous state. A similar approach is however not directly applicable to crystalline metals due to their highly reactive liquid state and rigid microstructural features in the solid state. This project investigates creep-based plastic deformation of crystalline metals and alloys for controllable molding at different length scales. Creep in metals is generally considered detrimental for structural applications, but recent studies indicate its potential for controllable nanoforming. Molding experiments with systematic variation in processing conditions and feedstock material enable decoupling of different creep mechanisms and their role in governing nanoscale metal molding. The project studies size-dependent mechanisms, e.g., dislocation-mediated plasticity, Nabarro-Herring creep, and Coble creep, in thermomechanical nanomolding of metals and alloys and flow mechanisms in template filling as a function of mold size, processing time and atmosphere. The knowledge gained from molding of homogeneous materials is applied to multi-phase and porous metal alloys, including high-entropy and eutectic alloys. Quantitative descriptions of creep induced flow advances the understanding of atomic diffusion in complex alloys and porous structures. Besides novel manufacturing science, the project has the potential to contribute new fundamental knowledge in metallurgy and mechanics.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.