Re: [Phys-l] 50 year incandescent bulb plus 56 more years

[Bernard Cleyet <bernardcleyet@redshift.com>]

Melting point order:

C, W, Re ....


It is widely used as filaments for mass spectrographs and ion gages. 
Rhenium-molybdenum alloys are superconductive at 10 K.

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.

Rhenium catalysts are exceptionally resistant to poisoning from nitrogen 
<http://www.corrosionsource.com/handbook/periodic/7.htm>, sulfur 
<http://www.corrosionsource.com/handbook/periodic/16.htm>, and 
phosphorus <http://www.corrosionsource.com/handbook/periodic/15.htm>, 
and are used for hydrogenation of fine chemicals.


   http://www.corrosionsource.com/handbook/periodic/75.htm


Thoriated W is used for cathodes in vacuum tubes.  I suspect such would 
lower the efficiency of lamps.

bc

Paul Lulai wrote:

> I would guess the 100+ year bulb is low wattage.  This would allow it to
> glow dimly w/o worrying about evaporation.  Thanks to Woolf, this
> probably means it has an increased resistance (skinnier or longer).
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> To any h.s. teachers out there, the Line of Resistance activities are
> pretty darn good.
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> Joe Bellina knows and mentions other alloys.  I don't know the variety
> of options that exist. I believe thorium is one common option (maybe a
> thorium oxide?).  I think the migration of the alloy to the surface
> would tweak the work function of the filament.  Would this have any
> noticeable effect on the function of the light bulb?   
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> Paul Lulai
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