Thermo-Mechanical Separation by Atomic Diffusion for Refinement and Recycling of Alloys

这项拨款支持的研究重点是一种有效回收金属合金的分离方法，这对实现循环经济很重要。合金废料的分离效率低下导致有价值的合金元素以杂质的形式流失。目前的合金分离方法是基于化学方法，这是能源密集型和危险的。本文研究了一种基于废金属中合金元素原子扩散差异的热-机械分离方法。该项目发展理论，以预测合金元素的分离率的基础上的扩散规律为基础的给定合金的兴趣。热机械分离过程使用适中的温度和压力，因此能耗较低。这种基于扩散的分离工艺为开发一种节能、经济、环保的方法从合金和废金属中分离元素奠定了基础，这对美国经济产生了重大影响。该项目涉及学生，特别是妇女和代表性不足的少数民族，他们接受多学科研究方面的培训，成为下一代熟练的工程师和科学家。学生将学习先进的材料制造和表征技术，数据分析及其解决材料科学问题的适应性。热机械分离是利用合金元素在施加温度和压力下扩散速率的差异将合金元素从合金中分离出来。这项研究基于最近开发的热机械纳米成型工艺的结果，在该工艺中，合金在高温和大压力梯度下通过纳米腔挤压。热机械纳米成型工作的初步结果显示，在大约40%的液相温度以上的温度下，元素分离。这种热机械分离过程基本上是由合金成分的原子扩散速率差异控制的。建立的压力梯度源于施加的压力和纳米腔的几何形状，激发了元素的扩散。建立了基于原子扩散的模型，量化了不同合金的分离速率，并将模型预测与实验确定的不同成分合金的分离速率进行了比较。在实验中，合金的选择是基于它们的技术重要性、开采、提取和回收产生的元素组合、元素的临界性以及替代精炼和回收过程的局限性。该项目的结果是揭示使用热机械分离来分离所需元素的合金是最有效的，最具影响力的，并且优于现有技术。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Research supported by this grant focuses on a separation method for efficient recycling of metallic alloys, which is important for achieving a circular economy. Inefficient separation of alloy scrap leads to loss of valuable alloying elements as impurities. Current alloy separation methods are based on chemical processes, which are energy intensive and hazardous. This research develops a thermo-mechanical separation method based on differences in atomic diffusion of the alloying elements in scrap metal. The project develops theory to predict the separation rates of the alloying elements based on the laws governing diffusion for a given alloy of interest. The thermo-mechanical separation process uses moderate temperatures and pressures and is thus less energy intensive. This diffusion-based separation process lays the foundation for the development of an energy-efficient, economic, and environmentally viable method to separate elements from alloys and scrap metal, which has significant impact on the US economy. The project involves students, especially women and under-represented minorities, who are trained in multi-disciplinary research and who become the next generation of skilled engineers and scientists. The students learn advanced materials fabrication and characterization techniques, data analytics and its adaptation for solving materials science problems.Thermo-mechanical separation is the separation of alloying elements from alloys utilizing their differences in diffusion rates under applied temperature and pressure. This research is based on results from a recently developed thermo-mechanical nanomolding process, in which an alloy is extruded through nanocavities at elevated temperatures and large applied pressure gradients. Preliminary results from the thermo-mechanical nanomolding work revealed separation of elements at temperatures above approximately 40% of the liquidus temperature. This thermo-mechanical separation process is essentially controlled by differences in atomic diffusion rates of the alloy constituents. The established pressure gradient, which originates from the applied pressure and nanocavity geometry, motivates diffusion of the elements. Models based on atomic diffusion are developed that quantify the separation rate for different alloys and model predictions are compared against experimentally determined separation rates for alloys with various compositions. For the experiments, alloys are selected based on their technological importance, the element combinations resulting from mining, extraction, and recycling, the criticality of the elements, and limitations of alternative refinement and recycling processes. The outcome of the project is to reveal for which alloys the use of thermo-mechanical separation to separate desired elements is the most effective, impactful, and superior over existing technologies.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.