Beside that Tungsten has a high melting point, resistivity, it has a catalytic effect on H2 gas decomposition to H radicals (H*) when it's heated.
im working on a process where i have to generate H-radicals using a hot filament; a process similar to the Cat-CVD.
to be clear; i use just H2 gas to make sure that the H-radicals are generated from the H2 gas decomposition !!
i tried many filament, Tungsten, Molybden, Titanium, Zirconium....etc
when using Zirconium, no H-radicals generated !!
searching on website, i found that some metals has a catalytic effect for H-radical generation and other's not !! But i can't find how or which properties make that some metals has the catalyzer, others not !!
J.W Geus thanks for the answer !!
in cat-CVD, types of source gases, catalyzing material and also the proper temperature of such catalyzer have to be determined as one set. [paper]
so: as i tried Zirconium filament up to 1400°C i checked no effect !!
so, what i would like to know if, is that some metal has catalyst effect and some no !! and why ?
Article Cat-CVD (hot-wire CVD): how different from PECVD in preparin...
Our group was investigating the hydrogen chemistry during the Cat-CVD for many years. Hydrogen decomposition on the hot wire depends on the metal nature, decomposition temperature, the nature of the precursor and pressure, in addition to other factors. In order to comprehend why some metals are more active than others, you need to look for their affinity towards molecular hydrogen at different temperature ranges.,
Please take a look at
\Y. J. Shi* (2015), Acc. Chem. Res. 48, 163-173, 2015 (DOI: 10.1021/ar500241x)
And the references herein
Mr. Ismail Badran thanks for the answer !!
could you please show me a link for the reference u shared, i cant fined an available one to check the paper or download it.
At lower temperatures the adsorbed or with zirconium the absorbed hydrogen atoms are highly mobile over the metal surface. The mobility induces collision between the adsorbed hydrogen atoms, which leads to desorption of molecular hydrogen. Tungsten has a very high melting point and exhibits a low vapor pressure at high temperatures. Consequently a tungsten filament can be rapidly heated to a temperature level where the adsorbed hydrogen atoms desorb as atoms before they can react on the surface to hydrogen molecules. From the binding energy of hydrogen in a hydrogen molecule it is obvious that desorption of molecular hydrogen can proceed at lower temperature than desorption of atomic hydrogen.
Elsewhere at this forum, I have discussed the apparent possiblity of high temperature formation of hydrogen cyanide (HCN) after CHi radicals (i = 1, 2, 3) reacting with (gaseous) nitrogen species, possibly involving heterogeneous catalysis:
https://www.researchgate.net/post/formation-of-cyanide-in-vacuum-sintering-in-high-temps-like-2000-C-with-nitrogen-atmosphere
I have also discussed the case of high temperature dissociation of H2 to atomic H for a (previous) gas misture of H2 and He ― while specifically adressing its heat capacity ratio (γ = Cp/Cv): https://www.researchgate.net/post/how_can_we_calculate_gamma_specific_heat_ratio_for_real_gas_chemical_non-equili/1
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