A thermodynamical calculation scheme is worked out to study radial and axial transport of tungsten in a halogen incandescent lamp. The approximations of a common diffusion coefficient for all gaseous components and local chemical equilibrium are used. Non-blackening is connected to an inequality forbidding deposition of tungsten onto the bulb wall. Chemical attack or growth of a given part of the coil is characterized by the second derivative of the global pressure of tungsten along the coil. The gettering effect of carbon on oxygen is shown to be limited by partial deposition of carbon as well as the formation of CO2 that decomposes at the coil releasing active oxygen.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Acoustics and Ultrasonics
- Surfaces, Coatings and Films