If I have any worthwhile input, it’s most likely to be on your first question. If you’d be interested, I think I could generate some phase diagrams for boron-hydrogen under reactor-relevant conditions. I’ll try to make a phase diagram of boron-hydrogen around 3500K, and 10-1000 Torr.
Edit:
I’ve attached Pressure vs Temperature and Temperature vs Composition phase diagrams.
The data describing the thermodynamics of these systems comes from SGTE’s “SSUB4” database.
This modeling describes solid and liquid boron’s Gibbs energies as two functions, both of which are essentially polynomials. The gas phase is described as 10 ideally interacting species, each of which also has its own sort-of-polynomial function Gibbs energy.
Thermo-calc, the software these plots were produced in, takes those descriptions and finds the lowest energy combination of species to make the gas phase, and the lowest energy combination of phases to meet the pressure/composition/temperature conditions.
So, for example, at 3500K, it’s found that out of 1 mole of substance, .913 moles are in the gas phase, and .086 moles are liquid boron. Further, the gas phase is made up of .480 moles Boron, .439 moles Hydrogen, .073 moles H_2, .005 moles BH, and .001 moles B2, along with trace amounts of other compounds, e.g., 1.58e-6 moles of BH3.
This P-T(log P vs 1/T) diagram was created at a fixed composition of 50:50::boron:hydrogen, but could be generated at other compositions as well, and the T-X(T vs mole fraction B) diagram was created at 100 torr, but could also be created at other pressures.
