First off I would like to say that my knowledge on chemistry, even general chemistry, is basic if not poor.

That said, I have some intuituions on this matter. I haven´t found any paper regarding this kind of system, and that is pretty much a killer for me. Even with that I´d still like to ask the question.

Ionic liquids, liquid salts, are regarded as having some conductive capacities, being low to moderate conductors due to their ionic nature. I know that salts have been used in MHD (magnetohydrodynamic) systems due to their high melting points -the ionic bond being particularly strong- and their conductive potential.

I have an specific fuel reaction in mind, An hydrazinium based propellant + LOX (liquid oxygen) as oxidizer,

[HO-C2H4-N2H4]+[NO3]- + 2.25 O2 = 2 CO2 + 1.5 N2 + 4.5 H2O

for example. I read that ionic liquid salts do not need to be dissolved for the anion and the cation to conduct electricity (https://www.researchgate.net/post/How_is_the_electrical_conductivity_of_ionic_liquids_in_comparison_with_metals) Outside of that I´d like to know if hydrainium based reactions do have some electric potential, or if by any reason wich I did not manage to grasp, it is simply out of the question to use them in such machines.

I would be very pleased to know if something is just worng or has been misunderstood.

Source for the reaction: http://cdn.intechweb.org/pdfs/20222.pdf, page 9 (455 in the original text).

Overal description of how a MHD machine works: https://en.wikipedia.org/wiki/Magnetohydrodynamic_generator

*Edit: The majority of the volume is occupied by the reaction products. Using just conventional fuels like liquid hydrogen is just more practical.

Still, we could use a thermal/catalytical decomposition reaction, like 6 NH3OHNO3(aq) = 2 N2(g) + 2 NH4NO3(s or l) + 6 H2O(g) + 4 HNO3(g), where both a salt and water are produced.


1 Answer 1


If fuel is oxidized at high temperature, the conductivity of the fuel itself is irrelevant -- only the conductivity of the combustion products, which are ionized because of the high temperature and are therefor conductive. Brittanica states that temperatures greater than ~2,500 K are needed for sufficient ionization. Alkali metals can be used to increase ionization, or higher temperatures have been used with inert gases.

Note that the temperature of ions and electrons in the gas are not necessarily the same, due to the difference in mass and time to reach equilibrium. This impacts on conductivity and the rate of erosion of the MHD components.


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