Rhenium electrical resistivity

Thermal Conductivity Detector One of the earliest gas chromatography detectors, which is still widely used, is based on the mobile phase s thermal conductivity (Figure 12.21). As the mobile phase exits the column, it passes over a tungsten-rhenium wire filament. The filament s electrical resistance depends on its temperature, which, in turn, depends on the thermal conductivity of the mobile phase. Because of its high thermal conductivity, helium is the mobile phase of choice when using a thermal conductivity detector (TCD). 

The electrical resistance of rhenium is about 3.5 times higher than tungsten at 20°C. However, the difference is reduced at higher temperatures because of rhenium s lower temperature coefficient, so that at 2500°C the resistivity of rhenium is only about 20% more than tungsten. The higher resistance at low temperature, combined with a lower temperature coefficient, contributes to rapid heating of a filament. 

For vibration-resistant applications, such as traffic signal lamps, non-sag wires with (1-5 wt%) Re are used. Rhenium improves the ductility of the recrystallized wire and also increases its electrical resistance, thus allowing a thicker and mechanically more stable wire [6.17]. 

Rhenium is also used as an electrical contact material because it has good wear resistance and withstands arc corrosion. Thermocouples made of Re-W are used for measuring temperatures up to 2200C, and rhenium wire is used in photoflash lamps for photography. 

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