The biggest difference between a halogen bulb and other incandescent lamps is that the glass envelope of the halogen lamp is filled with some halogen gas (usually iodine or bromine). The working principle is: when the filament is heated, the tungsten atoms are evaporated. The glass tube wall moves, and when approaching the glass tube wall, the tungsten vapor is cooled to about 800 ° C and combined with halogen atoms to form a tungsten halide (tungsten iodide or tungsten bromide). The tungsten halide continues to move toward the center of the glass tube and returns to the oxidized filament. Since the tungsten halide is a very unstable compound, it will be decomposed into halogen vapor and tungsten after heat, so that the tungsten is in the filament. It is deposited on top to make up for the part that is evaporated. Through this regeneration cycle, the service life of the filament is not only greatly extended (almost four times that of incandescent lamps), but also because the filament can work at higher temperatures, resulting in higher brightness, higher color temperature and Higher luminous efficiency.
The basic light-emitting principle of a tungsten halogen lamp is the same as that of an incandescent lamp, and is a heat radiation source. The difference is that the tungsten halogen lamp is filled with a special working gas, which is composed of a mixture of 95% (dibromomethane and helium) and 5% of high-purity nitrogen, which establish a tungsten halogen cycle in the bulb. The specific process is that after the tungsten in the filament is volatilized, it will move beyond the lower temperature, and then combine with Br to form WBr2 at the tube wall; at a higher temperature, WBr2 will decompose again, and the generated W will return to the filament. On, Br returns to the working gas, which is the process of the entire tungsten halogen cycle. Through such a tungsten halogen cycle, the tungsten on the filament does not gradually evaporate, and the filament is blown due to the "hot spot" effect, and the tungsten is not blackened by deposition on the bulb shell, and its life is greatly prolonged.
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