Studies on the Use of Atomically Thin Films for Controlling Friction and Adhesion at Interfaces

摩擦和粘附力的控制是广泛认识到的问题，其影响广泛的材料应用，从齿轮和发动机部件到用于关节置换的医疗植入物，再到微米和纳米级机器技术。设计先进润滑方案的动力不仅有助于在这些领域引入新技术，而且还可以在提高机器效率方面发挥关键作用，其中许多经济部门摩擦和磨损的总能量损失极大地促进了满足美国能源需求的艰巨挑战。石墨烯是一种单原子厚的碳膜，由于其出色的电气和机械性能，为控制界面处的摩擦和粘附力方面的许多挑战提供了潜在的解决方案。然而，大多数关于石墨烯摩擦特性的科学研究都是在完美光滑的理想表面上进行的。 该奖项支持基础研究，以了解原子级薄材料（如石墨烯）在现实界面中的特性，这些界面并不完全光滑，但具有精细的粗糙度。这些实验研究将用于确定哪些方面控制石墨烯原子薄膜的特性，以及如何设计这些特性以满足技术需求。参与该项目的学生接受材料科学，工程，表面化学和物理学的多学科培训，发展这些领域的熟练程度，这对美国技术竞争力的持续发展至关重要。真实的表面特性，如表面粗糙度和粘合剂相互作用对石墨烯的影响-将研究基于润滑剂的材料，以确定如何设计表面和石墨烯以满足技术需求。重要的是，这些材料如何结合到具有受控纳米级粗糙度的基底上，将通过创建熔融二氧化硅纳米颗粒的膜来检查，其中表面粗糙度由颗粒尺寸决定。与金纳米颗粒薄膜的类似研究将用于解决导电表面的这些相同的问题。原子力显微镜和拉曼显微光谱将用于了解这些材料如何符合纳米级粗糙度的基板，以及这如何影响其摩擦化学反应性和摩擦特性。 这些研究将与类似条件下粗糙接触中石墨烯的分子动力学模拟配对，提供原子解析的化学相互作用和机械贡献的细节，以改变石墨烯在粗糙-粗糙接触中的化学，结构，机械和摩擦特性，这些接触主导技术相关表面之间的接触。

Control of friction and adhesion are widely recognized problems that impact a broad range of materials applications from gears and engine components, to medical implants for joint replacements, to micro- and nano-scaled machine technologies. The drive to design advanced lubrication schemes not only facilitates bringing new technologies online in these areas, but can also play a critical role in terms of improved machine efficiencies, where aggregate energy losses to friction and wear in many sectors of the economy contribute greatly to the daunting challenges of meeting US energy needs. Graphene, a single-atom-thick film of carbon, offers a potential solution to many of the challenges in controlling friction and adhesion at interfaces due to its exceptional electrical and mechanical properties. The majority of the scientific studies on the frictional properties of graphene, however, are on perfectly smooth, idealized surfaces. This award supports fundamental research to understand the properties of atomically thin materials such as graphene in realistic interfaces, which are not perfectly smooth but have fine roughness. These experimental studies will be used to determine what aspects control the properties in atomically thin films of graphene, and how these may be engineered to meet technological needs. Students involved in this project receive multidisciplinary training in materials science, engineering, and surface chemistry and physics, developing proficiency in these areas that are critical for the continued development of US technological competitiveness.The influence of real surface characteristics like surface roughness and adhesive interactions on graphene-based lubricants will be investigated to determine how surfaces and graphene may be engineered to meet technological needs. Importantly, how such materials bind to substrates with controlled nanoscopic roughness will be examined by creating films of fused silica nanoparticles, where surface roughness is determined by particle size. Analogous studies with gold nanoparticulate films will be used to address these same questions for conductive surfaces. Atomic force microscopy and Raman microspectroscopy will be used to understand how these materials conform to substrates with nanoscale roughness, and how this influences its tribochemical reactivity and frictional characteristics. These studies will be paired with molecular dynamics simulations of graphene in asperity contacts under analogous conditions, providing atomically resolved detail of the chemical interactions and mechanical contributions to changes in the chemical, structural, mechanical, and frictional properties of graphene in the asperity-asperity contacts that dominate contact between technologically relevant surfaces.