From the article initially linked by apophys, both of these were experimented with, but combustion was given up because of solid deposits of boron oxides on the engine, and fluorination was given up because fluorine is fluorine. Properties for the new boron compounds were taken from NIST JANAF kinetics (B2O3, BF3) and wikipedia. Stoichometry / number of reagents balanced by me.
LOX Diborane reaction characteristics copied from LOX Ethane, Fluorine Diborane characteristics copied from Fluorine Hydrazine.
Please review / adjust / recommend corrections.
Last Edit: Jan 9, 2017 5:30:29 GMT by someusername6: Fixed Fluorine-Diborane reactant and product counts
I think there might be an error relating to the decomposition - in a 4478 K resistojet, I am only getting 7.83% dissociation - compare that to methane, which fully dissociates at only ~900 K. And diborane, with its 3c2e bonds and with how touchy it is at only 300 K, should definitely be fully dissociated by 4478 K.
Update: I noticed another weird effect: When keeping everything else constant, the dissociation percentage varies depending on the throat diameter! Tightest I can make it without the engine explodingA bit wider, and the dissociation percentage is markably increased. And fully dissociated
Any idea why this would happen? Other substances like Methane seem to also show this behaviour, but they fully dissociate at nearly all throat radii with the chamber temperatures we typically use.