Can Ordinary Glass Be Used as a Bulb Shell for Iodine Tungsten Lamp?

Ordinary glass cannot be used as a bulb shell for an iodine tungsten lamp. The iodine tungsten lamp is a kind of illumination lamp that uses the principle of halogen-tungsten circulation to fill iodine into the bulb to control the sublimation of the tungsten wire. It has the characteristics of high brightness and long life. It is often used as the light source of cinematography stage factory building square.

The iodine tungsten lamp consists of metal tungsten wire and a bulb shell, in which the function of the shell is to prevent internal heat loss for oxidation speed and prevent external scald and electric shock. Because the combination temperature of iodine and tungsten is between 250℃ and 1200℃, the reaction between the tungsten surface and iodine vapor will have a great influence on sealing, so the bulb wall must be stable in this temperature range. In actual production, quartz glass with a small thermal coefficient and high melting point is generally selected as the bulb shell.

However, quartz glass as the bulb shell of iodine tungsten lamp also has some shortcomings, and the brittleness of quartz glass is poor, while the hardness is not conducive to the long-term use of iodine tungsten lamp at high temperatures with the increase in temperature.

Therefore, can ordinary glass be used as a substitute?

The main components of ordinary glass are more complex, such as sodium silicate, calcium silicate, etc. Physically, ordinary glass working at this temperature will crystallize and be opaque. In thermodynamics, the negative Gibbs reaction energy between glass and iodine vapor in the temperature range of the tungsten-iodine combination reaction means that the corresponding chemical reaction will take place to produce sodium iodide (NaI), which will affect the halogen-tungsten cycle between tungsten wire and iodine vapor. Moreover, in surface pretreatment such as oxidation, hydrogen burning, and decarburization, the manufacturing process of ordinary glass is more complicated than that of quartz glass, so ordinary glass is not suitable for the bulb shell of an iodine tungsten lamp.

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