Development of an electron work function-based novel methodology for designing advanced tribo-materials

材料科学和工程在发展理论和方法来改进材料以增强抗破坏能力方面有着悠久的历史。微结构工程在材料设计中起着至关重要的作用。然而，微观结构特征并不总是为裁剪材料提供明确的线索。随着在常规条件和极端条件下的应用需求的增加，材料设计已经被要求依赖于更基本的原则。该项目旨在开发结构材料设计的新方法，重点是在可行的电子基础上使用摩擦材料。材料的内在特性从根本上是由它们的电子行为决定的，电子行为决定着原子键的强度和延展性。基于量子力学将材料的力学性质与其电子态联系起来已经做了大量的工作，然而量子力学在结构材料设计中的应用比较复杂。为了使材料的分析和设计可行，迫切需要具有反映材料电子行为的简单而基本的参数。申请人小组对电子功函数（EWF）进行了广泛的研究，并证明了EWF与许多材料性能相关，是指导裁剪材料的有希望的指标。然而，材料的性能不仅取决于材料中单个相和晶粒的性能，还取决于材料的微观结构。多晶材料中不同EWFs的第二相接触时，存在电子转移以建立热力学平衡。这些会影响EWF分布，从而影响整体性能。因此，了解微观结构成分如何影响整体EWF及其与整体或整体材料特性的关系，对于开发现实材料设计的新方法具有重要意义。这是本次新发现项目提出的主要研究目标或长期研究目标，这与申请人之前的发现项目不同，该项目主要研究EWF与纯金属和均质固溶体性质之间的关系。该项目将包括以下内容：1)研究微观结构成分，包括晶粒尺寸、取向、晶界和第二相（尺寸、形貌、性能和界面）如何影响多晶多相材料的局部和全局EWFs；2)研究EWF与多相材料性能之间的相关性，以发展基于EWF的材料设计和裁剪方法，重点是摩擦材料。

Materials science and engineering have a long history of developing theories and approaches to improve materials for enhanced resistance to failure. Microstructure engineering plays a crucial role in material design. However, microstructural features do not always provide clear clues for tailoring materials. With increased demands for applications under not only usual conditions but also extreme ones, material design has been required to rely on more fundamental principles. This project is proposed to develop new methodologies for structural material design with emphasis on tribo-materials on a feasible electronic base. Intrinsic properties of materials are fundamentally determined by their electron behavior, which governs the atomic bond strength and ductility. Great effort has long been made to correlate mechanical properties of materials to their electron state based on quantum mechanics, which is, however, complicated to be used in structural material design. It is highly desired to have simple but fundamental parameters, which reflect the electron behavior of materials, for material analysis and design in a feasible manner. The applicant's group has conducted extensive studies on electron work function (EWF) and demonstrated that EWF is correlated to many material properties, and is a promising indicator for guiding tailoring materials. However, material properties are dependent not only on properties of individual phases and grains in a material but also its microstructure. When second phases in polycrystalline materials with different EWFs are in contact, there exists electron transfer in order to establish thermodynamic equilibrium. These affect EWF distribution and thus overall performance. Thus, it is of significance to understand how microstructuralconstituents influence the overall EWF and its relationships with theoverall or global material properties towards the development of newmethodologies for realistic material design. This is the main goal orlong-term objective of research proposed in this new Discovery project,which is distinct from that of applicant's previous Discovery project, which was focused on thecorrelation between EWF and properties of pure metals and homogeneoussolid solutions. The followings will be included in the project: 1) studies on how microstructural constituents, including grain size, orientation, grain boundaries, and second phases (size, morphology, properties and interface), influence local and global EWFs of polycrystalline multiphase materials; and 2) studies on the correlation between EWF and properties of the multi-phase materials towards development of EWF-based approaches or methodologies for material design and tailoring with focus on tribo-materials.