金属Ag，Cu及其与石墨烯复合界面摩擦的第一性原理研究
发布时间：2018-08-29 16:06
【摘要】：摩擦现象对人类的生产和生活有着不可忽视的影响。世界上有大约1/3-1/2的一次性能源消耗在摩擦过程中,世界上工业发达国家由于摩擦和磨损引起的损失占了国民生产总值(GDP)的5%-7%。所以对摩擦的研究至关重要,从四世纪开始,人们已经开始对摩擦进行研究,最基本的摩擦学规律是阿蒙顿定律。随着科学技术的发展,现代精密器件的尺寸越来越小,比表面积越来越大,摩擦对微电子机械器件的正常运行和使用寿命有着决定性的影响。科学家在对一些材料研究中发现了超润滑现象,超润滑指摩擦因数为0或无限接近于0,超润滑的发现为现代微纳机械系统设计和制造带来了希望。理论研究表明最有可能产生超润滑现象的材料就是二维材料,如石墨烯,二硫化钼,六方氮化硼等。这些二维材料由于晶面原子间有极强的化学键,晶面间不易发生形变,同时层间有很弱的范德华力,界面间滑动时的摩擦力更易接近零。随后在实验中也证实了超润滑现象验证了理论预测。软金属Ag,Cu的优良润滑性能使它们被应用于精密仪器的制造。但是随着科学技术的飞速发展,在超高精密仪器或微电子机械系统的滑动界面需要非常低的摩擦甚至没有摩擦。这就对润滑材料有了更苛刻的要求,传统的软金属Ag,Cu的润滑性能已不能满足需要,超润滑(Superlubricity)(指发生相对运动的物体间的摩擦力几乎为零甚至完全消失的现象)性能的发现和研究为更高摩擦学性能需求的器件和微电子机械系统带来了希望。二维材料(石墨烯,MoS2,WO2等)在特定的实验条件下摩擦力消失摩擦因数为零出现超润滑现象,但是,都有不足之处,就拿石墨烯来说,承受一定载荷后滑动会引起边缘起皱,这种面内形变会引起摩擦因数升高导致超润滑失效。于是,我们希望把石墨烯附着在软金属表面上作为润滑层,一方面保护金属层,另一方面改善表面的润滑性能,满足机械系统所需要的超低摩擦要求。本文中运用第一性原理密度泛函理论(DFT)系统地研究了在微纳尺度下金属与金属界面,金属与石墨烯界面和通过石墨修饰的金属界面的摩擦性能研究。我们的研究发现了金属与金属界面在微尺度下仍遵守阿蒙顿定律;金属与石墨烯界面有着极低的摩擦因数是由界面间较弱的物理吸附引起的;石墨修饰的金属界面产生了超润滑现象,比单独的石墨烯界面更易实现超润滑。
[Abstract]:Friction phenomenon has an important influence on the production and life of human beings. About 1 / 3-1 / 2 of the world's disposable energy is consumed in the friction process. The losses caused by friction and wear in the developed countries in the world account for 5- 7% of the gross national product (GDP). Therefore, the study of friction is very important. Since the fourth century, people have begun to study friction, the most basic law of tribology is Amonton's law. With the development of science and technology, the size and specific surface area of modern precision devices are becoming smaller and larger. Friction has a decisive effect on the normal operation and service life of microelectro-mechanical devices. In the study of some materials, scientists have found the phenomenon of superlubrication, which means that the friction coefficient is zero or infinitely close to zero. The discovery of superlubrication brings hope to the design and manufacture of modern micro-nano mechanical system. Theoretical studies show that the most likely superlubricating materials are two-dimensional materials, such as graphene, molybdenum disulfide, hexagonal boron nitride and so on. Due to the strong chemical bond between the atoms in the crystal plane, the deformation between the two planes is not easy, and there is a very weak van der Waals force in the interlayer, so the friction force between the interfacial sliding is closer to zero. Then the theoretical prediction was verified in the experiment. The excellent lubricating properties of soft metal Ag,Cu make them used in the manufacture of precision instruments. However, with the rapid development of science and technology, very low friction or no friction is required in the sliding interface of ultra-high precision instruments or microelectromechanical systems. This has more stringent requirements for lubricating materials. The lubricating performance of traditional soft metal Ag,Cu can no longer meet the needs. Superlubricating (Superlubricity) (refers to the phenomenon that the friction between objects in relative motion is almost zero or even completely disappeared) the discovery and study of the properties bring hope to the devices and microelectromechanical systems with higher tribological properties. Two dimensional materials (graphene, MoS2WO2, etc.) have superlubricating phenomena when the friction coefficient is zero, but there are some shortcomings. For graphene, sliding under certain load will cause edge wrinkle. This in-plane deformation can cause the friction coefficient to increase and lead to overlubrication failure. Therefore, we hope to attach graphene to the soft metal surface as a lubricating layer, on the one hand to protect the metal layer, on the other hand to improve the lubricating performance of the surface, to meet the requirements of the mechanical system for ultra-low friction. In this paper, the friction properties of metal-metal interface, metal-graphene interface and graphite-modified metal interface are systematically studied by using first-principles density functional theory (DFT). It is found that the metal to metal interface obeys Amonton's law at the microscale, and the very low friction coefficient between the metal and graphene interface is caused by the weak physical adsorption between the metal and the graphene interface. The metal interface modified by graphite produces superlubrication, which is easier to realize than the single graphene interface.
【学位授予单位】：兰州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TH117.1
本文编号：2211710
[Abstract]:Friction phenomenon has an important influence on the production and life of human beings. About 1 / 3-1 / 2 of the world's disposable energy is consumed in the friction process. The losses caused by friction and wear in the developed countries in the world account for 5- 7% of the gross national product (GDP). Therefore, the study of friction is very important. Since the fourth century, people have begun to study friction, the most basic law of tribology is Amonton's law. With the development of science and technology, the size and specific surface area of modern precision devices are becoming smaller and larger. Friction has a decisive effect on the normal operation and service life of microelectro-mechanical devices. In the study of some materials, scientists have found the phenomenon of superlubrication, which means that the friction coefficient is zero or infinitely close to zero. The discovery of superlubrication brings hope to the design and manufacture of modern micro-nano mechanical system. Theoretical studies show that the most likely superlubricating materials are two-dimensional materials, such as graphene, molybdenum disulfide, hexagonal boron nitride and so on. Due to the strong chemical bond between the atoms in the crystal plane, the deformation between the two planes is not easy, and there is a very weak van der Waals force in the interlayer, so the friction force between the interfacial sliding is closer to zero. Then the theoretical prediction was verified in the experiment. The excellent lubricating properties of soft metal Ag,Cu make them used in the manufacture of precision instruments. However, with the rapid development of science and technology, very low friction or no friction is required in the sliding interface of ultra-high precision instruments or microelectromechanical systems. This has more stringent requirements for lubricating materials. The lubricating performance of traditional soft metal Ag,Cu can no longer meet the needs. Superlubricating (Superlubricity) (refers to the phenomenon that the friction between objects in relative motion is almost zero or even completely disappeared) the discovery and study of the properties bring hope to the devices and microelectromechanical systems with higher tribological properties. Two dimensional materials (graphene, MoS2WO2, etc.) have superlubricating phenomena when the friction coefficient is zero, but there are some shortcomings. For graphene, sliding under certain load will cause edge wrinkle. This in-plane deformation can cause the friction coefficient to increase and lead to overlubrication failure. Therefore, we hope to attach graphene to the soft metal surface as a lubricating layer, on the one hand to protect the metal layer, on the other hand to improve the lubricating performance of the surface, to meet the requirements of the mechanical system for ultra-low friction. In this paper, the friction properties of metal-metal interface, metal-graphene interface and graphite-modified metal interface are systematically studied by using first-principles density functional theory (DFT). It is found that the metal to metal interface obeys Amonton's law at the microscale, and the very low friction coefficient between the metal and graphene interface is caused by the weak physical adsorption between the metal and the graphene interface. The metal interface modified by graphite produces superlubrication, which is easier to realize than the single graphene interface.
【学位授予单位】：兰州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TH117.1
【参考文献】
相关期刊论文 前1条
1 郑泉水;欧阳稳根;马明;张首沫;赵治华;董华来;林立;;超润滑:“零”摩擦的世界[J];科技导报;2016年09期
，本文编号：2211710
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