why are tungsten filaments used in light bulbs
Tungsten is a kind of refractory metal, it has a high melting point, resistivity, good strength, low steam, is the best material to make incandescent filament of all the pure metal.Tungsten wire resistance related to the temperature, the higher the temperature, the greater the resistance of tungsten wire.
Tungsten wire can remain stable at high temperatures without melting, used as a light bulb in the heating element, possesses the advantages of long service life, low price.
Once the tungsten wire is recrystallized at high temperature, it becomes brittle and easily breaks under impact or vibration。In order to prevent the filament from breaking, 3-5% rhenium is often added to the doped tungsten filament, which is called tungsten-rhenium filament. It can reduce the ductile-brittle transition temperature of tungsten to below room temperature. This is a very strange rhenium effect, and no element has been found to replace rhenium in tungsten to produce the same effect.
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