CAREER: Understanding and controlling the sintering of metal powders with nanoscale additives

非技术总结该职业项目将金属可持续3D打印的研究与教育工作联系起来，通过实践材料科学结合几位卓有成就的黑人科学家的鼓舞人心的故事来激励K-12和大学生。该研究解决了围绕一种称为粘合剂喷射的金属3D打印的关键问题。金属是食品、水、交通和医疗保健的核心，但不幸的是，金属开采和生产产生了全球气候变化影响的10%。因此，需要对金属采取少花钱多办事的做法。为此，粘合剂喷射是大规模制造可持续金属零件的最有前途的方法之一。然而，粘结剂喷射正被有关烧结科学的知识缺口所阻碍。当固体材料随着时间的推移融合在一起时，就会发生烧结，比如冰块在冰箱里粘在一起。对于粘结剂喷射，烧结是至关重要的，因为它将金属粉末熔化到最终部件中。烧结对表面的化学成分高度敏感，但对表面成分（如涂层）的微小变化如何影响金属粉末的烧结却知之甚少。为了推进粘结剂喷射，这项工作使用多模态方法来理解烧结过程中重要的物理和化学过程。总的来说，这项研究为理解、预测和控制含有微量添加剂的金属烧结，实现可持续的金属制造铺平了道路。该项目的综合研究和教育工作对社会产生了广泛影响。这项研究本身为汽车、航空航天等领域的可扩展、可持续金属制造打开了新的大门。此外，该项目还推出了教育举措，致力于使历史上代表性不足的群体充分参与STEM，沿着加强STEM教育和教育工作者的发展。这些努力开始在当地的塔尔萨社区分享动手K-12模块烧结，沿着迷人的故事，高度成就的黑人科学家。这些努力通过与TeachEngineering.org和NSBE的合作在全球范围内扩大。总的来说，综合研究和教育支持多元化，具有全球竞争力的STEM劳动力的增长。技术总结该项目的研究重点是解锁新的范式，用于通过粘合剂喷射制造大批量，高效率的金属零件的性能和可预测性。知识产权的优点集中在建立广泛的工艺结构性能的关系，烧结铝和钛合金粉末，并没有微量添加剂，提高烧结。详细地说，该研究探测了在使用纳米级添加剂（例如，增强粘合剂、纳米颗粒、粉末涂料和渗透剂）。这项工作使用原位显微镜和光谱学来解开耦合的物理和化学机制，在光的散装衍射，原位定量烧结变形，烧结后的机械性能。此外，这项工作研究了重要的孔隙/晶界相互作用，通过引入一类新的纳米级渗透，这提供了一个工具箱来研究空位扩散和孔隙/晶界相互作用，以及增加烧结金属的密度的新途径。这项工作还通过数字图像相关来量化部分失真，以校准基于材料点方法的粘合剂喷射烧结模型，这是一种对数百万颗粒的物理特性进行建模的强大方法。总的来说，该研究解决了烧结过程中添加剂与基体金属的化学/物理相互作用的关键问题。这为定制/设计粉末、纳米颗粒、涂料、添加剂和渗透剂开辟了新的视野。该研究与教育紧密结合，旨在丰富科学学习并激励未来的STEM领导者。与塔尔萨社区的STEM教育工作者合作，这项工作分享了为学生带来烧结生活的实践活动。再加上这种动手学习的故事，海报和数字媒体的分享，许多高度成就的黑人工程师和材料科学家。与NSBE合作，这些故事在全世界发行。最后，在烧结研究的基础上，塔尔萨大学的本科课程中增加了一个新的粉末冶金实验室模块。该奖项反映了NSF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。

NON-TECHNICAL SUMMARYThis CAREER project connects research on sustainable 3D printing of metals with education efforts to inspire K-12 and college students through hands-on materials science combined with inspiring stories about several highly accomplished Black scientists. The research addresses critical questions surrounding a type of metal 3D printing called binder jet. Metals are central to food, water, transportation, and healthcare, but unfortunately, metal extraction and production generates 10% of global climate change impacts. Therefore, there is a need for doing more with less for metals. Towards this, binder jet is one of the most promising ways to make sustainable metal parts at a large scale. However, binder jet is being held back by knowledge gaps about the science of sintering. Sintering happens when solid pieces of material fuse together over time, such as ice cubes sticking together in a freezer. For binder jet, sintering is critical because it fuses metal powders into the final part. Sintering is highly sensitive to the chemical composition of surfaces, yet there is little understanding about how small changes in surface compositions (such as coatings) influence the sintering of metal powders. To advance binder jet, this work uses a multi-modal approach to understand important physical and chemical processes during sintering. Overall, this research paves the way towards understanding, predicting, and controlling sintering of metals with trace additives, towards sustainable metal manufacturing. The project's integrated research and education efforts have broad impacts around society. The research itself opens new doors for scalable, sustainable metal manufacturing for automotive, aerospace, and beyond. Additionally, this project launches education initiatives that work towards full participation of people from historically underrepresented groups in STEM, along with enhanced STEM education and educator development. These efforts start locally in the Tulsa community by sharing hands-on K-12 modules on sintering, along with captivating stories about highly accomplished Black scientists. The efforts expand globally in collaboration with TeachEngineering.org and NSBE. Overall, the integrated research and education supports the growth of a diverse, globally competitive STEM workforce.TECHNICAL SUMMARYThe research of this project focuses on unlocking new paradigms for the performance and predictability of high-volume, high-efficiency metal parts fabricated by binder jet. The intellectual merit centers on establishing extensive process-structure-property relationships for sintered Al- and Ti-alloy powders with and without trace additives that enhance sintering. In detail, the investigation probes the evolution of particle interfaces, necks, grains, and pores during sintering with nanoscale additives (e.g., enhancing binders, nanoparticles, powder coatings, and infiltrants). The work uses in situ microscopy and spectroscopy to unravel coupled physical and chemical mechanisms, in light of bulk dilatometry, in situ quantification of sintering distortions, and mechanical properties after sintering. Additionally, this work studies important pore/grain-boundary interactions by introducing a new class of nanoscale infiltration, which provides a toolbox to study vacancy diffusion and pore/grain boundary interactions, as well as a new pathway for increasing the density of sintered metals. This work also quantifies part distortion via digital image correlation to calibrate models of binder jet sintering based on the material point method, a powerful way to model the physics of millions of particles. Overall, the research addresses key questions about the combined chemical/physical interactions of additives with the base metal during sintering. This opens new horizons for tailored/designer powders, nanoparticles, coatings, additives, and infiltrants. The research integrates closely with education that seeks to enrich science learning and inspire future STEM leaders. In collaboration with STEM educators in the Tulsa community, the work shares hands-on activities that bring sintering to life for students. Coupled with this hands-on learning is the sharing of stories, posters, and digital media about numerous highly accomplished Black engineers and material scientists. In collaboration with NSBE, these stories are distributed worldwide. Finally, building from the sintering research, a new laboratory module on powder metallurgy is added to the undergraduate curriculum at The University of Tulsa.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.