Friction properties of the single-crystal Si in collision sliding contacts under different lubrication conditions

With the development of nanotechnology, micro-nano electromechanical systems are widely used in various high-precision instruments, e.g., micro-nano satellites, pico-satellites, in which single-crystal Si is always employed. In outer space, there will be random collisions in space mechanisms caused by unexpected and irregular small disturbances especially under the microgravity environment. In this paper, a molecular dynamics model is used to simulate the motion of the mechanism based on the motion characteristics of random collisions happened within space mechanisms, and irregular collisions are represented by sinusoidal vibrations of the indenter in Y and Z directions. The friction properties of the collision sliding contacts under the lubrication of gold films with different layers are investigated. The results show that a nine-layer gold film presents good vibration absorption and lubrication performance. Then, rectangular textures are designed and made on the gold film. The textured surface can significantly reduce the friction forces at high vibration frequencies. In addition, the friction properties of a molybdenum disulfide (MoS2) film and the combined lubrication behaviors of molybdenum disulfide films and gold films are studied. The molybdenum disulfide film shows excellent friction properties at different vibration frequencies, and the combination of molybdenum disulfide and gold films can significantly reduce the average friction force within a specific vibration frequency range.