CAREER: New Solid State Metal Foams Using Oxide Reduction and Intraparticle Expansion

事业：利用氧化物还原和颗粒内膨胀的新型固态金属泡沫

• 批准号: 2035473
• 负责人: Mark Atwater
• 金额: $ 20.42万
• 依托单位: Liberty University, Inc.
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-01-15 至 2023-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2035473&HistoricalAwards=false
• 关键词: CAREER; New; Solid; State; Metal

Nontechnical DescriptionMetals are useful materials, as they are durable and easy to manufacture, but they have characteristically high densities which make them inefficient in many weight-sensitive applications. Their density can be reduced by introducing porosity, but porosity is also useful for increasing surface area, enhancing energy absorption, assisting bone ingrowth and more. Methods used to "foam" metals often require high temperatures, high pressures and/or complex processes, which limit the availability and cost-effectiveness of these materials. A new method has been developed to enhance porosity in metals at modest temperatures using simple, well-established powder metallurgy processes. The fundamental difference is that pores are developed within individual powder particles in the solid state, and this expandable metal powder can be incorporated into current, state-of-the-art foaming processes to enhance the level of porosity, or it can be used as a stand-alone process. This unique approach to creating porous metals may allow for cost reduction, the development of new metals and alloys for solid state foaming and the overall improvement of solid state foam processing. Both the fundamental mechanisms and commercial potential of this technology will be investigated to create a holistic understanding of the process and resulting materials. This technology can result in more fuel-efficient transit, safer vehicles, reduced emissions and much more. Through this work, educational awareness and career opportunities will be developed in partnership with the local community. This will involve establishing, promoting and expanding undergraduate research initiatives and promoting diversity in materials research and nanoscale technologies. Technical DescriptionA new method in the solid state foaming of metals has been developed using standard powder metallurgy processing. The technique involves two steps: (1) disperse oxides in a metal powder and (2) reduce oxides at a temperature sufficient to allow expansion. In general, mechanical milling can be used to create an oxide dispersion-strengthened (ODS) metal which is later foamed under hydrogen at elevated temperature via the formation of steam at oxide sites. The conditions under which this process is achieved depend on the oxide and matrix composition but are expected to be modest when compared to current foaming processes. This fundamentally different approach will allow for advances on three major fronts: (1) the ability to make metal foams with new compositions, (2) enhanced ability to control the structure and properties of the metal foam, and (3) the ability to combine this process with established powder metallurgy foaming methods to significantly increase the resulting porosity.This work will help to elucidate the fundamental mechanisms of this new method and has the potential to alleviate some of the critical issues plaguing solid state foaming. These issues include the complexity of processing, the lack of diversity in foamed metals and alloys and the modest porosities and/or mechanical properties achieved using current solid-state foaming methods. A number of fundamental research questions will be addressed, including: What is the influence of process variables, including reduction temperature, oxide chemistry, content and character, the microstructural properties of the matrix, and quantity and chemistry of process gas(es) on the pore formation process? What is the reduction and pore expansion behavior of multi-element systems, especially in which the elements possess greatly differing oxidation potentials? And what is the fundamental behavior of the ODS powder feedstock during bulk processing? A process map will be produced for creating metallic foams of a given porosity while independently controlling pore size, morphology and interconnectedness.This work will be conducted in a multi-scale manner, and an understanding of the nano- and micro-scale phenomena will be leveraged to inform processing decisions and methods by which to incorporate this feedstock into current, state-of-the-art methodologies. Educational initiatives will impact the university and community through increased collaboration internally and engaging local organizations to provide new opportunities for students to develop professionally. Expanded programs and opportunities in undergraduate research will be developed through this work, and outreach in the community will be conducted to help inform others of advanced materials and manufacturing as well as to inspire the future generation toward science and engineering.

非技术描述金属是有用的材料，因为它们耐用且易于制造，但它们具有高密度的特点，这使得它们在许多重量敏感的应用中效率低下。它们的密度可以通过引入孔隙度来降低，但孔隙度对于增加表面积、增强能量吸收、帮助骨骼向内生长等也很有用。用于“发泡”金属的方法通常需要高温、高压和/或复杂的工艺，这限制了这些材料的可用性和成本效益。已经开发出一种新方法，可使用简单、完善的粉末冶金工艺在适度温度下提高金属的孔隙率。根本区别在于，孔隙是在固态的单个粉末颗粒内形成的，这种可膨胀金属粉末可以纳入当前最先进的发泡工艺中以提高孔隙率水平，也可以用作独立工艺。这种独特的多孔金属制造方法可以降低成本，开发用于固态发泡的新金属和合金，并全面改进固态泡沫加工。将研究该技术的基本机制和商业潜力，以全面了解该过程和所得材料。这项技术可以带来更省油的交通、更安全的车辆、减少排放等等。通过这项工作，将与当地社区合作提高教育意识和职业机会。这将涉及建立、促进和扩大本科生研究计划，并促进材料研究和纳米技术的多样性。技术描述采用标准粉末冶金加工技术开发出一种金属固态发泡的新方法。该技术包括两个步骤：（1）将氧化物分散在金属粉末中，（2）在足以允许膨胀的温度下还原氧化物。一般来说，机械研磨可用于制造氧化物弥散强化（ODS）金属，随后在高温下通过在氧化物位点形成蒸汽而在氢气下发泡。实现该过程的条件取决于氧化物和基体成分，但与当前的发泡过程相比，预计条件是适度的。这种根本不同的方法将在三个主要方面取得进展：(1) 能够制造具有新成分的金属泡沫，(2) 增强控制金属泡沫的结构和性能的能力，以及 (3) 能够将该工艺与现有的粉末冶金发泡方法相结合，以显着增加最终的孔隙率。这项工作将有助于阐明这种新方法的基本机制，并有可能缓解 困扰固态发泡的一些关键问题。这些问题包括加工的复杂性、泡沫金属和合金缺乏多样性以及使用当前固态发泡方法实现的适度的孔隙率和/或机械性能。将解决许多基础研究问题，包括：工艺变量（包括还原温度、氧化物化学、含量和特性、基体的微观结构特性以及工艺气体的数量和化学性质）对孔形成过程的影响是什么？多元素体系的还原和孔扩张行为是什么，特别是其中元素具有截然不同的氧化电位的情况？ ODS 粉末原料在批量加工过程中的基本行为是什么？将制作一个工艺图，用于创建给定孔隙率的金属泡沫，同时独立控制孔径、形态和互连性。这项工作将以多尺度方式进行，并将利用对纳米和微米尺度现象的理解来为加工决策和方法提供信息，从而将该原料纳入当前最先进的方法中。教育举措将通过加强内部合作和当地组织的参与来影响大学和社区，为学生的专业发展提供新的机会。通过这项工作，将开发本科生研究的扩展项目和机会，并将在社区中进行推广，以帮助其他人了解先进材料和制造，并激励下一代走向科学和工程。