| The fused quartz is one of main materials in optical elements. Optical elements as an important part of the terminal in the optical components, whose surface cleanliness has an important influence on the pass rate of laser and the lifetime of the device. With the further increase of laser power transient, clean degree involves problem increasingly prominent: optical elements structure and pollutants will reduce the efficiency of laser, and pollutants absorbed energy would lead to explosive evaporation, further damaging structure and formating on the surface of mechanical damage. Therefore, in order to improve the optical quality and reduce maintenance costs and gain cleaning surface of the high degree, it is necessary to study the wetting of nanostructure and adsorpton dsorption mechanism of pollutants optical from fused silica.Firstly, the theory of molecular dynamics(MD) is introduced to lay a foundation for the simulations later. At the same time, the common processing methods of optical elements are analyzed, and some typical defect structures of the processing surface is summarized, which is the foundation of substrate nanostructure.Secondly, in order to study the effect of surface nanostructure on dsorption of contaminants in the environment of water medium from Fused silica. The adsorption process of water cluster structure on fused silica with nanostructure is simulated by MD. The adsorption process of water cluster is analyzed by changing the surface parameters such as shape and size of the structure, the content of the organic group and the degree of hydroxylation. From the analyze above the Wenzel-Cassie critical transition rules are found and the critical transition line is put forward. The analyzing emphasis is put on the the oppsite rules when water cluster size is among the specific threshold range.Thirdly, the adsorption of organic pollutant on fours different nanostructures are simulated. By analyzing the changing rules of the energy and mass center height during the adsorption process, a special rebound phenomenon is found when the surface nanostructure is rectangular groove. By analyzing the molecular density distribution, the influence which the surface structure has on the stability of oil layer is analyzed. It can be inferred that the formation of oil film goes against the desorption process of oil molecules.Thirdly, based on the former water and oil adsorption analyzing, the desorption process of oil within water medium is simulated on four kinds of nanostructures surface. By analyzing and comparing the four kinds of desorption processes of oil reservoir, we found that the more the oil film is difficult to take off, and found a conclusion that the more oil film exists the harder for oil desorption can be draw, which verifies the assumption and it is also found that the formation speed of vertical water channel is the driven factor for this phenomenon. At the same time, the quantity and distribution patterns of residual oil molecules of four kinds of structure are analyzed, and two kinds of residual oil molecular phenomenon about ring well and rectangular groove structures are found. Through the analysis of the mechanism of groove potential well the the rectangular groove structure of residual oil mechanism is clarified and this is also the ring well functional mechanism.Finally, the different methods of cleaning cleaning are used to different structures on the surface of fused silica samples. The contact angles are compared in the experiment and, the influence of surface nanostructure on the wettability is analyzed. The discussion above, combined with the surface residual organic matters content detection through X-ray photoelectron spectroscopy(XPS), verifies the residual effect of oil melecules on nanostructure. and the influence factors of the experimental results are analyzed from different aspects. |
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