Understanding the Effects of Sheet Size and Salt Addition on Aqueous MXene Dispersions: Phase Behavior, Rheological Properties, and Printability

MXene是由过渡金属碳化物、氮化物或碳氮化物组成的二维（2D）晶体纳米材料家族。它们在电子和储能设备（如更好的电池）中的应用非常有前景。MXene的一个优点是它们可以分散在水中，并使用流体相处理技术（如直接墨水书写（DIW））加工成设备和结构。到目前为止，MXene处理的进步需要耗时且昂贵的试错方法。需要对MXene分散体有基本的了解，才能通过基于流体的制造方法始终如一地实现功能性MXene设备。该项目将通过对MXene分散特性，DIW打印以及打印设备的微观结构和电导率之间的联系进行基本了解来满足这一需求。此外，通过将MXenes视为带电2D胶体血小板的一个例子，这项研究也将扩展目前对2D材料分散体的科学理解。该研究小组将与其他研究人员合作，推进研究2D材料胶体分散体的实验和理论方法。 本科研究人员将成为研究团队的一个组成部分，PI将指导高中学生进行相关研究。为了进一步吸引K-12学生，该团队将为奥本大学的几个项目开发有关印刷和电气设备的活动，包括工程日，促进儿童工程（PEAK），工程营中的女性以及为即将到来的少数民族工程专业学生提供的夏桥计划。提出的研究的动机是假设MXene分散体表现出与其他带电胶体2D血小板（也称为盘或板）类似的富相行为。拟议的研究旨在回答有关MXene分散体的三个问题：1）纸张尺寸分布对相行为和流变性的影响; 2）氯化钠（NaCl）添加对相行为和流变性的影响;以及3）分散体特性如何影响测试结构的印刷性和导电性？这项研究将促进对MXene相行为以及影响印刷适性的组成和微观结构依赖的流变性能的理解。与流变学和小角中子散射（Rheo-SANS）相结合的专家以及理解带电2D材料分散理论发展的领导者的合作将增加科学理解的深度。这些贡献将促进对结构-工艺-性能关系的理解，以及如何为DIW配制MXene油墨。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。

MXenes are a family of two-dimensional (2D) crystalline nanomaterials composed of transition metal carbides, nitrides, or carbonitrides. They are very promising for applications in electronics and energy storage devices such as better batteries. One advantage of MXenes is that they can be dispersed in water and processed into devices and structures using fluid phase processing techniques such as direct ink writing (DIW). So far, advances in MXene processing have required time consuming and expensive trial and error approaches. A fundamental understanding of MXene dispersions is needed to consistently achieve functional MXene devices via fluid-based manufacturing methods. This project will address this need by developing a fundamental understanding of the connections between MXene dispersion properties, DIW printing, and the microstructure and electrical conductivity of printed devices. In addition, by considering MXenes as an example of a charged 2D colloidal platelet, this research will also extend the current scientific understanding of dispersions of 2D materials. The research team will collaborate with other researchers on advancing the experimental and theoretical methods to study colloidal dispersions of 2D materials. Undergraduate researchers will be an integral part of the research team, and the PIs will mentor high school students on related research. To further engage K-12 students, the team will develop activities on printing and electrical devices for several programs at Auburn University, including Engineering Day, Promoting Engineering for Kids (PEAK), Women in Engineering Camp, and a Summer Bridge Program for incoming minority engineering students. The proposed research is motivated by the hypothesis that MXene dispersions exhibit a rich phase behavior similar to that of other charged colloidal 2D platelets (also termed disks or plates). The proposed research seeks to answer three questions about MXene dispersions: 1) What are the effects of sheet size distribution on phase behavior and rheology; 2) What are the effects of sodium chloride (NaCl) addition on phase behavior and rheology; and 3) How do dispersion properties affect printability and the electrical conductivity of test structures? This research will advance understanding of MXene phase behavior and the composition and microstructure dependent rheological properties that affect printability. Collaborations with an expert in combining rheology and small angle neutron scattering (Rheo-SANS) and a leader in the development of theories for understanding dispersions of charged 2D materials will increase the depth of scientific understanding. Together these contributions will advance understanding of structure-process-property relationships and how to formulate MXene inks for DIW.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.