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

该基金支持的研究重点是有效回收金属合金的分离方法，这对实现循环经济非常重要。合金废料的低效分离导致有价值的合金元素作为杂质损失。目前的合金分离方法是基于化学过程，这是能源密集型和危险的。本研究发展了一种基于合金元素在废金属中原子扩散差异的热力分离方法。该项目开发理论，以预测合金元素的分离率的基础上，为一个给定的合金感兴趣的扩散规律。热机械分离工艺使用中等温度和压力，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，数据分析及其用于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的温度和压力下的扩散速率差异将合金元素从合金中分离出来。这项研究是基于最近开发的热机械纳米成型工艺的结果，在该工艺中，合金在升高的温度和大的压力梯度下通过纳米腔挤出。来自热机械纳米模塑工作的初步结果揭示了在高于液相线温度的约40%的温度下元素的分离。这种热机械分离过程基本上由合金成分的原子扩散速率的差异控制。所建立的压力梯度，其来源于所施加的压力和纳米腔的几何形状，促使元素的扩散。基于原子扩散模型的开发，量化不同合金的分离率和模型预测进行比较，对实验确定的分离率与各种成分的合金。在实验中，合金的选择是基于其技术重要性，采矿，提取和回收产生的元素组合，元素的关键性，以及替代精炼和回收工艺的局限性。该项目的成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，影响最大的，并且优于现有技术的上级。该奖项反映了NSF的法定使命，并且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.