Filament types typically use pure Tungsten, or Thoriated Tungsten or in newer types a Nickel alloy coated with alkaline "Rare Earth" compounds.
Gold and Molybdenum are very soft metals, and would probably not support their own weight if heated to the temperatures of the pure Tungsten filaments. At a minimum they would have the potential to stretch and possibly short things out. Molybdenum has been used as a friction reducing additive because of the softness of the material, and it's ability to act as a lubricant at higher temperatures.
This is not to say that deForest, Flemming, Marconi, and Edison did not experiment with those materials, just that it is not very likely. Edison's experiments with various materials for his light bulbs, so his work laid out a starting point for Lee deForest, Flemming, Marconi, and others to build on, and they knew what characteristics they needed to make things work.
Gold and Molybdenum also do not form oxides reaily, and their reaction potentials are low, so they are not "free electron emitters", that you would need for a filament, or a heater for that matter.
RCA does list Molybdenum as one of the materials that are used in grid wires, but they do not specify which tubes, and again, Molybdenum is a very soft metal, so it is doubtful it was widely used even there.
You may have heard some erroneous speculations by some Gold hunters, which would be bad for the tube market as you would have speculators running prices up, then essentially removing them (tubes/valves) from the market place where they would be destroyed for no good reason; and well out of the reach of radio restorers.
I will however gladly sell them my duds, and I am sure many people would contribute their duds too, but there just is not any amount of gold- regardless of spot prices of gold- that would be of real use in a tube that would have been used in real amounts. One would find more gold as an impurity in eutectic solders.
If you do hear something that sounds substantial, please let us know.
: Does Anybody know a kind of tube (or termoionic valve) wich is based on filaments (anode?) of molybdenum coated with gold?
: If so, could I have any reference about it?
: Regards
: Marcello D'Elia - Italy
: Filament types typically use pure Tungsten, or Thoriated Tungsten or in newer types a Nickel alloy coated with alkaline "Rare Earth" compounds.
: Gold and Molybdenum are very soft metals, and would probably not support their own weight if heated to the temperatures of the pure Tungsten filaments. At a minimum they would have the potential to stretch and possibly short things out. Molybdenum has been used as a friction reducing additive because of the softness of the material, and it's ability to act as a lubricant at higher temperatures.
: This is not to say that deForest, Flemming, Marconi, and Edison did not experiment with those materials, just that it is not very likely. Edison's experiments with various materials for his light bulbs, so his work laid out a starting point for Lee deForest, Flemming, Marconi, and others to build on, and they knew what characteristics they needed to make things work.
: Gold and Molybdenum also do not form oxides reaily, and their reaction potentials are low, so they are not "free electron emitters", that you would need for a filament, or a heater for that matter.
: RCA does list Molybdenum as one of the materials that are used in grid wires, but they do not specify which tubes, and again, Molybdenum is a very soft metal, so it is doubtful it was widely used even there.
: You may have heard some erroneous speculations by some Gold hunters, which would be bad for the tube market as you would have speculators running prices up, then essentially removing them (tubes/valves) from the market place where they would be destroyed for no good reason; and well out of the reach of radio restorers.
: I will however gladly sell them my duds, and I am sure many people would contribute their duds too, but there just is not any amount of gold- regardless of spot prices of gold- that would be of real use in a tube that would have been used in real amounts. One would find more gold as an impurity in eutectic solders.
: If you do hear something that sounds substantial, please let us know.
:
: : Does Anybody know a kind of tube (or termoionic valve) wich is based on filaments (anode?) of molybdenum coated with gold?
: : If so, could I have any reference about it?
: : Regards
: : Marcello D'Elia - Italy
: Does Anybody know a kind of tube (or termoionic valve) wich is based on filaments (anode?) of molybdenum coated with gold?
: If so, could I have any reference about it?
: Regards
: Marcello D'Elia - Italy
Western Electric made most of their tubes with molybdenum grids held with nickel side rails. Western Electric gold plated these grid laterals in their premium tubes such as 350A and 350B.
RCA used molybdeum for plates and grids, even in transmitting tubes. It was easier to work with and degas than tungsten. Usually fins were added to molybdeum plates and they were roughened by carborundum blasting to improve heat radiation.
Norm
: Does Anybody know a kind of tube (or termoionic valve) wich is based on filaments (anode?) of molybdenum coated with gold?
: If so, could I have any reference about it?
: Regards
: Marcello D'Elia - Italy