Tungsten Filament Sublimation

Tungsten Filament Sublimation

Tungsten filament sublimation is that tungsten atom would directly become gaseous tungsten. After a long time using, when the bulb doesn’t work, the temperature of inner bulb would decrease, gaseous tungsten would release heat and become solid tungsten and attach to the bulb inwall. Due to sublimation, tungsten filament would be thinner, cross-sectional area would be smaller, resulting filament resistance increases. The formula P = U2/R shows that the greater the resistance, the less actual power. When the bulb works, temperature of filament would rise and solid tungsten would directly become gaseous state due to the heat effect of current. Tungsten atoms sublime at high temperatures generated by the current, leaving the tungsten filament, so the tungsten filament would become thinner. There are two electrodes inside the bulb, people can change their place, so that the other side of the filament would not sublime for a long time.

How to Prevent Tungsten Sublimation?

High power lamps can be filled with argon, nitrogen and other gases to prevent sublimation of tungsten filament at high temperature. Incandescent filament would be surrounded by a thin stable protective, which can slow the speed of tungsten fimanet sublimation.