Tailoring the Composition, Morphology and Assembly of MXene Nanosheets

MXenes是最近发现的一类引人入胜的二维过渡金属(M) -碳(X)纳米片，有望在与先进能源，电子和国防应用相关的许多领域促进国家繁荣和国防。这项资助推进了不同组成和形态的MXene纳米结构的加工及其组装成功能纳米膜的研究。该基金将解决与MXenes生产相关的主要研究挑战，并开发加工技术，将这些技术形成可用的薄膜，并确定最终的工艺-性能关系。各种MXenes在理论上是可能的，但尚未通过实验获得。MXenes以二维薄片的形式存在，将其横向尺寸从纳米尺寸扩展到宏观尺寸仍然具有挑战性。该项目将开发处理方法，以生产具有以前不可能的组合物和官能团的MXenes。计划将这些有趣的材料整合到聚合物复合材料中，将使它们能够整合到许多涂层技术中。通过对组成、形状、结构和多层结构的操纵来控制材料特性，将允许扩展其物理特性的范围。研究人员和学生将参与多种推广工作，以促进研究生，本科生和K-12级别的材料科学教育，研究，多样性和代表性，特别注重培养学生的创业技能。本文将研究目前MXene合成和加工的主要局限性，以及在纳米或单个纳米片水平和宏观薄膜和复合材料水平上潜在的工艺-结构-性能关系。这些材料来源于层状陶瓷（即MAX相），具有广泛的可能成分和官能团。“MX”这个名字是指这些层状结构中的M（过渡金属）和X（通常是碳）；一个常见的例子包括Ti3C2Tx，其中T代表各种终端组。具体的研究任务包括：(1)通过改变母相MAX的组成来实现A层的容易蚀刻，并通过施加电化学偏压来扩展现有MXenes的组成空间；(2)喷雾干燥过程中的毛细力会操纵MXene的形态，形成货架稳定的三维MXene颗粒；(3)通过逐层组装制备的宏观MXene-聚合物结构的性质和性能将被确定为MXene层间距和形貌的函数。在每个阶段，MXene的组成、官能团和结构将与整体机械和电气性能联系起来。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。

MXenes are a recently discovered fascinating class of 2-D transition metal (M) - carbon (X) nanosheets that hold promise to advance the national prosperity and defense in numerous areas associated with advanced energy, electronics, and defense applications. This grant advances the processing of MXene nanostructures with different compositions and morphologies and their assembly into functional nanofilms. The grant will address the major research challenges associated with the production of MXenes and develop the processing techniques to form these into usable films as well as determine the resultant process-property relationships. A variety of MXenes are theoretically possible, but have yet to be experimentally obtained. MXenes exist as 2D sheets and extending their lateral dimension from nano-to-macro size remains challenging. This project will develop processing methodologies for producing MXenes with compositions and functional groups that have previously been impossible. The planned incorporation of these interesting materials into polymer composites would allow their integration into many coating technologies. The control over the material properties through manipulation of composition, shape, structure, and multi-layer architectures will allow an expansion of the range of their physical properties. The researchers and students will engage in multiple outreach efforts to foster education, research, diversity, and representation in materials science at the graduate, undergraduate, and K-12 levels, with the special focus on developing students entrepreneurship skills. The major current limitations in both MXene synthesis and processing and the underlying process-structure-property relationships at both the nano or individual nanosheet level and the macroscopic films and composites level will be investigated. These materials are derived from layered ceramics (i.e., MAX phases) and have a wide range of possible compositions and functional groups. The "MX" name refers to the M (transition metal) and X (typically carbon) in these layered structures; a common example includes Ti3C2Tx, where T stands for various terminal groups. The specific research tasks include the following: (1) The compositional space of existing MXenes will be extended by altering the composition of the parent MAX phase to achieve easy etching of A layers and by applying an electrochemical bias; (2) Capillary forces during spray drying will manipulate MXene morphology and create shelf-stable 3-D MXene particles; and (3) Properties and performance of macroscopic MXene-polymer structures created using layer-by-layer assembly as a function of MXene interlayer spacing and morphology will be determined. At each stage, MXene composition, functional groups, and architecture will be connected to the bulk mechanical and electrical properties.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.