Evaporation coating is to vaporize a substance by heating so that it can deposit on a solid surface. First proposed in 1857 by M. Faraday, this approach has become one of the common coating technologies in modern times. The structure of the evaporation coating device is shown in figure 1. Vaporized material such as metal and compound are placed in a crucible or hung on the hot wire as the evaporation source and the workpiece to be coated, such as metals, ceramics and plastics are placed in front of the crucible. After the system is vacuumized, the crucible should be heated so that the material therein evaporates. Atoms or molecules of the evaporated material is deposited on the substrate surface in condensation mode. The thickness of the film ranges from several hundred angstroms to several microns. Thickness depends on the evaporation rate and time (or inventory) of the evaporation source and is related to the distance between the source and the substrate. For large-area coating, the method of rotating the substrate or increasing evaporation source is often used to ensure that the thickness of the film is even. Distance from the evaporation source to the substrate should be less than the mean free path of vapor molecules of residual gas to prevent vapor molecules from colliding with residual gas thus causing chemical action. The average kinetic energy of the vapor molecules is about 0.1 to 0.2 eV.
。The mechanism vacuum tube coating is explained as follows. Aluminum nitrogen complex films are widely used in vacuum tubes. The film layer can be divided to the interior, middle and exterior layer and all have their own function. As a reflective layer, the inner layer is mainly used to prevent the heat of the hot water in the pipe from radiating outward; the middle layer is an absorbing layer and the main function of it is to absorb energy and transform the energy into heat; the exterior layer is an anti-reflection layer, which is mainly used to reduce the sun reflection and increase the absorption rate of sunlight.
The mechanism vacuum coating is that the membrane body is evaporated to the surface of the workpiece at a high temperature and crystallizes. Since the air will obstruct the evaporated membrane molecules, making the crystalline rough and dim, crystalline can only be exquisite and glossy under the environment of high vacuum. If the vacuum degree is not high, the crystalline will lose its luster and the adhesion is also very poor. Early vacuum coating which relied on the evaporated items to scatter naturally is of poor adhesion, low efficiency, and poor glossiness. Now intermediate frequency magnetron sputtering target is used. the evaporated molecules of the membrane bombard the target under the effect of an electric field at faster speed and sputter a large number of target atoms. Neutral target atoms (or molecules) is deposited on a substrate and become the film, which solves the problem that some films can not be processed through natural evaporation formation, such as titanize and plate zirconium. Currently aluminum nitrogen complex films are widely used in vacuum tubes. The film layer can be divided to the interior, middle and exterior layer and all have their own function. As a reflective layer, the inner layer is mainly used to prevent the heat of the hot water in the pipe from radiating outward; the middle layer is an absorbing layer and the main function of it is to absorb energy and transform the energy into heat; the exterior layer is an anti-reflection layer, which is mainly used to reduce the sun reflection and increase the absorption rate of sunlight.
The mechanism vacuum coating is that the membrane body is evaporated to the surface of the workpiece at a high temperature and crystallizes. Since the air will obstruct the evaporated membrane molecules, making the crystalline rough and dim, crystalline can only be exquisite and glossy under the environment of high vacuum. If the vacuum degree is not high, the crystalline will lose its luster and the adhesion is also very poor. Early vacuum coating which relied on the evaporated items to scatter naturally is of poor adhesion, low efficiency, and poor glossiness. Now intermediate frequency magnetron sputtering target is used. the evaporated molecules of the membrane bombard the target under the effect of an electric field at faster speed and sputter a large number of target atoms. Neutral target atoms (or molecules) is deposited on a substrate and become the film, which solves the problem that some films can not be processed through natural evaporation formation, such as titanize and plate zirconium.
