Freeze-Cast Manufacturing of Stable Iron-Alloy Foams for Energy Conversion and Storage

冷冻铸造是一种用于制造多孔材料或泡沫的低成本制造技术。该奖项研究了冷冻铸造作为制造铁镍、铁钴和铁铜泡沫的一种手段，这些泡沫有助于为电网储存能量的电池提供动力，或改善化学循环技术，以捕获发电厂的二氧化碳排放。通过推进这些应用的材料制造，该项目有助于国家能源安全，气候行动目标和美国在先进能源材料领域的竞争力。在多孔材料的冷冻铸造方面开发的知识也有利于其他工业部门，如医疗保健，通过多孔骨替代植入物，以及汽车和航空航天，通过轻质结构。目前使用冷冻铸造能源材料的一个限制是它们在使用过程中降解。为了解决这个问题，本研究探讨了方法，如添加合金元素，以稳定冷冻铸铁泡沫和增加其使用寿命。研究工艺参数与材料性能之间的关系，为此类合金的优化和商业化奠定了基础。该项目积极促进女性和代表性不足的少数民族参与研究，并继续建立跨学科和国际合作。在能源应用中，如高温固体氧化物电池或化学链燃烧，铁基氧化还原材料由于与氧化/还原反应相关的重复摩尔体积变化而迅速降解。冷冻铸造的层状泡沫的孔结构非常适合解决这个问题，因为它为每个薄片提供了自由膨胀和收缩的空间，而不受相邻薄片的约束。尽管如此，机械降解仍然发生由于Kirkendall的不平衡的扩散通量和断裂/分解的氧化物相的形成。合金铁泡沫镍，钴，或铜的研究作为一种策略，以抑制上述降解过程中，通过创建镍，钴或铜丰富的韧性核心内的薄板，并通过使扩散通量更平衡。原位同步辐射X射线衍射和纳米层析成像被用来揭示这些合金在氧化还原循环过程中的相和微观结构的演变。这些原位研究的补充热重分析，异位氧化还原循环，金相研究。最后，CALPHAD，相场和有限元模型的开发，以帮助指导合金和成分的选择，通过实验提供验证。这个奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

Freeze casting is a low-cost manufacturing technique for creating porous materials or foams. This award investigates freeze casting as a means to make iron-nickel, iron-cobalt, and iron-copper foams that help power batteries for storing energy on the electricity grid, or improve chemical looping technologies for capturing carbon dioxide emissions from power plants. By advancing the materials manufacturing for these applications, this project contributes to national energy security, climate action goals, and U.S. competitiveness in the advanced energy materials sector. The knowledge developed in freeze casting of porous materials also benefits other industrial sectors such as healthcare, via porous bone-replacement implants, and automotive and aerospace, via lightweight structures. One current limitation to using freeze-cast energy materials is that they degrade during use. To address this problem, this research investigates methods, such as adding an alloying element, to stabilize freeze-cast iron foams and increase their usable lifetime. The relationships between manufacturing parameters and materials performance lay the groundwork for optimization and commercialization of such freeze-cast alloys. This project actively promotes participation of women and underrepresented minorities in research and continues building interdisciplinary and international collaborations.In energy applications, such as high-temperature solid-oxide batteries or chemical looping combustion, iron-based redox materials rapidly degrade due to the repeated molar volume changes associated with oxidation/reduction reactions. The pore architecture of freeze-cast, lamellar foams is ideally suited to address this issue, as it provides space for each lamella to expand and contract freely, without constraints from neighboring lamellae. Nevertheless, mechanical degradation still occurs due to Kirkendall micropore formation from imbalanced diffusion fluxes and fracture/spallation of the oxide phase. Alloying iron foams with nickel, cobalt, or copper is investigated as a strategy to suppress the above degradation processes, by creating Ni-, Co- or Cu-rich ductile cores within the lamellae, and by making diffusional fluxes more balanced. In-situ synchrotron X-ray diffraction and nano-tomography are used to reveal the phase and microstructural evolution in these alloys during redox cycling. These in-situ studies are complemented by thermogravimetry, ex-situ redox cycling, and metallography studies. Lastly, CALPHAD, phase-field, and finite-element models are developed to help guide alloy and composition selection, with validation provided by experiment.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.