Collaborative Research: Understanding Run-In and Superlubricity of Diamond-Like Carbon Coatings from a Tribochemical Perspective

合作研究：从摩擦化学角度理解类金刚石碳涂层的磨合和超润滑性

• 批准号: 1912210
• 负责人: Brian Borovsky
• 金额: $ 5.18万
• 依托单位: Saint Olaf College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-06-01 至 2023-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1912210&HistoricalAwards=false
• 关键词: Collaborative; Research; Understanding; Run; Superlubricity; Collaborative; Research; Understanding; Run; Superlubricity

Smartphone screens are an impressive example of how new technologies often rely on surface engineering, such as the ability to create durable, hard and slippery surfaces. Many key economic sectors can benefit from minimized wear and friction of surfaces, including the automotive, medical device, computer component and defense sectors, so that this research directly and positively impacts the economic welfare and national security of the United States. Recently, a hard surface coating known as diamond-like carbon (DLC) has been found to achieve an extreme level of slipperiness called "superlubricity". This desirable property is, however, very sensitive to environmental conditions such as the amount of water or hydrogen in the surrounding atmosphere. Sensitivity to environmental conditions limits the effectiveness of the coating for many potential applications. This collaborative research aims to understand the chemical reactions that govern superlubricity in DLC and to discover ways to extend its high performance to a wider range of conditions. The collaborators at Penn State and St. Olaf College specialize in measuring friction using different state-of-the-art methods that complement each other. The broader impacts of this study extend to training the next generation of scientists in the United States by supporting student participation in the research. Educational activities will include outreach for underrepresented minority recruitment at Penn State and undergraduates at St. Olaf, instruction of undergraduates in friction-related physics at St. Olaf, instruction in DLC surface properties for a graduate course at Penn State, surface characterization tutorials in professional conferences, and student participation in international collaborations. Due to its amorphous nature, the carbon atoms in DLC have very broad distributions in bond length and angle. The covalent bonds in DLC are formed during the high-energy deposition process and cannot be relaxed or rearranged without annealing at extremely high temperatures. This means that the lengths and angles of many bonds in DLC deviate significantly from the minimum-energy structure of ideal sp2 and sp3 hybridization. Those bonds are weaker and more reactive compared to the bonds with parameters close to the ideal structures. Such broad distributions in bond parameters and reactivities are intrinsic parameters specific to each DLC coating and its deposition conditions. The main thesis of this study is that the presence of highly-distorted carbon-carbon bonds facilitates a mechanochemically-induced polymorphic transition to graphitic domains at the shearing interface. Under this hypothesis, the run-in process can be attributed to the shear-induced mechanochemical transformation of the distorted carbon networks to graphitic (or graphene-like) domains. The transformation process will also be affected by reactions with molecules impinging from the gas phase. These surface reactions with surrounding gas molecules are extrinsic parameters affecting the run-in and superlubricity of DLC. A mechanically-assisted thermal activation (Arrhenius-type) model will be combined with structural characterization to study how the intrinsic and extrinsic parameters facilitate or hamper the shear-induced mechanochemical transformation of the DLC interface to graphitic domains with ultra-low shear resistance.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.

智能手机屏幕是新技术通常如何依赖地表工程的一个令人印象深刻的例子，例如能够创建耐用，坚硬和湿滑的表面。许多关键的经济部门可以从最小化的磨损和摩擦力中受益，包括汽车，医疗设备，计算机组件和防御部门，因此这项研究直接和积极地影响了美国的经济福利和国家安全。最近，发现一种称为钻石样碳（DLC）的硬表面涂层达到了一种极端的滑水，称为“超级润滑性”。然而，这种理想的特性非常敏感，例如环境条件，例如周围大气中的水或氢的数量。对环境条件的敏感性限制了许多潜在应用的涂层的有效性。这项协作研究旨在了解控制DLC上级润滑性的化学反应，并发现将其高性能扩展到更广泛条件的方法。 宾夕法尼亚州立大学和圣奥拉夫学院的合作者专门使用彼此补充的不同最先进的方法来测量摩擦。这项研究的更广泛的影响扩展到培训美国下一代科学家，通过支持学生参与研究。教育活动将包括在宾夕法尼亚州立大学的少数族裔招募和本科生的教育活动，圣奥拉夫的本科生的本科生指导，在宾夕法尼亚州立大学的DLC Surface Properties指导宾夕法尼亚州立大学的教学，专业会议中的表面表征教程，并参与了国际合作。由于其无定形性，DLC中的碳原子的键长和角度具有非常广泛的分布。 DLC中的共价键是在高能沉积过程中形成的，不能在高温下退火而放松或重新排列。这意味着DLC中许多键的长度和角度显着偏离了理想SP2和SP3杂交的最小能量结构。与接近理想结构的参数相比，这些键更弱且更具反应性。键参数和反应性中的这种广泛分布是每个DLC涂层及其沉积条件的内在参数。这项研究的主要论点是，高度延伸的碳键的存在促进了机械化学诱导的多态性过渡到剪切界面处的石墨结构域。在此假设下，磨合过程可以归因于剪切诱导的碳网络向石墨（或石墨烯状）域的机械化学转换。转化过程也将受气相撞击的分子的反应影响。这些与周围气体分子的表面反应是影响DLC磨合和超级润滑性的外部参数。机械辅助的热激活（ARRHENIUS型）模型将与结构表征相结合，以研究固有和外在参数如何促进或阻碍剪切诱导的DLC界面机械化学转化的机械化学转化，使得型智力奖励的智力奖励。优点和更广泛的影响审查标准。